go.mod: update golang.org/x dependencies

Update golang.org/x dependencies to their latest tagged versions. Change-Id: Iae75e5fcbcfe3709820dd66638a763f662f8d939 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/603396 Auto-Submit: Gopher Robot <gobot@golang.org> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: David Chase <drchase@google.com>
ssh: add support for unpadded RSA signatures
2024-08-06 15:38:17 +00:00 · 2024-07-26 16:39:19 +00:00 · 2024-07-22 17:35:33 +00:00 · 2024-07-17 17:59:23 +00:00 · 2024-07-16 18:24:57 +00:00 · 2024-07-16 16:09:32 +00:00
244 changed files with 19961 additions and 11790 deletions
@@ -1,3 +0,0 @@
-# This source code refers to The Go Authors for copyright purposes.
-# The master list of authors is in the main Go distribution,
-# visible at https://tip.golang.org/AUTHORS.
@@ -1,3 +0,0 @@
-# This source code was written by the Go contributors.
-# The master list of contributors is in the main Go distribution,
-# visible at https://tip.golang.org/CONTRIBUTORS.
@@ -1,4 +1,4 @@
-Copyright (c) 2009 The Go Authors. All rights reserved.
+Copyright 2009 The Go Authors.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are
@@ -10,7 +10,7 @@ notice, this list of conditions and the following disclaimer.
 copyright notice, this list of conditions and the following disclaimer
 in the documentation and/or other materials provided with the
 distribution.
-   * Neither the name of Google Inc. nor the names of its
+   * Neither the name of Google LLC nor the names of its
 contributors may be used to endorse or promote products derived from
 this software without specific prior written permission.

@@ -3,17 +3,20 @@
 // license that can be found in the LICENSE file.

 // Package acme provides an implementation of the
-// Automatic Certificate Management Environment (ACME) spec.
-// The intial implementation was based on ACME draft-02 and
-// is now being extended to comply with RFC 8555.
-// See https://tools.ietf.org/html/draft-ietf-acme-acme-02
-// and https://tools.ietf.org/html/rfc8555 for details.
+// Automatic Certificate Management Environment (ACME) spec,
+// most famously used by Let's Encrypt.
+//
+// The initial implementation of this package was based on an early version
+// of the spec. The current implementation supports only the modern
+// RFC 8555 but some of the old API surface remains for compatibility.
+// While code using the old API will still compile, it will return an error.
+// Note the deprecation comments to update your code.
+//
+// See https://tools.ietf.org/html/rfc8555 for the spec.
 //
 // Most common scenarios will want to use autocert subdirectory instead,
 // which provides automatic access to certificates from Let's Encrypt
 // and any other ACME-based CA.
-//
-// This package is a work in progress and makes no API stability promises.
 package acme

 import (
@@ -33,8 +36,6 @@ import (
 	"encoding/pem"
 	"errors"
 	"fmt"
-	"io"
-	"io/ioutil"
 	"math/big"
 	"net/http"
 	"strings"
@@ -72,22 +73,22 @@ const (
 )

 // Client is an ACME client.
+//
 // The only required field is Key. An example of creating a client with a new key
 // is as follows:
 //
-// 	key, err := rsa.GenerateKey(rand.Reader, 2048)
-// 	if err != nil {
-// 		log.Fatal(err)
-// 	}
-// 	client := &Client{Key: key}
-//
+//	key, err := rsa.GenerateKey(rand.Reader, 2048)
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//	client := &Client{Key: key}
 type Client struct {
 	// Key is the account key used to register with a CA and sign requests.
 	// Key.Public() must return a *rsa.PublicKey or *ecdsa.PublicKey.
 	//
 	// The following algorithms are supported:
 	// RS256, ES256, ES384 and ES512.
-	// See RFC7518 for more details about the algorithms.
+	// See RFC 7518 for more details about the algorithms.
 	Key crypto.Signer

 	// HTTPClient optionally specifies an HTTP client to use
@@ -125,7 +126,9 @@ type Client struct {

 	cacheMu sync.Mutex
 	dir     *Directory // cached result of Client's Discover method
-	kid     keyID      // cached Account.URI obtained from registerRFC or getAccountRFC
+	// KID is the key identifier provided by the CA. If not provided it will be
+	// retrieved from the CA by making a call to the registration endpoint.
+	KID KeyID

 	noncesMu sync.Mutex
 	nonces   map[string]struct{} // nonces collected from previous responses
@@ -140,23 +143,22 @@ type Client struct {
 //
 // When in pre-RFC mode or when c.getRegRFC responds with an error, accountKID
 // returns noKeyID.
-func (c *Client) accountKID(ctx context.Context) keyID {
+func (c *Client) accountKID(ctx context.Context) KeyID {
 	c.cacheMu.Lock()
 	defer c.cacheMu.Unlock()
-	if !c.dir.rfcCompliant() {
-		return noKeyID
-	}
-	if c.kid != noKeyID {
-		return c.kid
+	if c.KID != noKeyID {
+		return c.KID
 	}
 	a, err := c.getRegRFC(ctx)
 	if err != nil {
 		return noKeyID
 	}
-	c.kid = keyID(a.URI)
-	return c.kid
+	c.KID = KeyID(a.URI)
+	return c.KID
 }

+var errPreRFC = errors.New("acme: server does not support the RFC 8555 version of ACME")
+
 // Discover performs ACME server discovery using c.DirectoryURL.
 //
 // It caches successful result. So, subsequent calls will not result in
@@ -177,53 +179,36 @@ func (c *Client) Discover(ctx context.Context) (Directory, error) {
 	c.addNonce(res.Header)

 	var v struct {
-		Reg          string `json:"new-reg"`
-		RegRFC       string `json:"newAccount"`
-		Authz        string `json:"new-authz"`
-		AuthzRFC     string `json:"newAuthz"`
-		OrderRFC     string `json:"newOrder"`
-		Cert         string `json:"new-cert"`
-		Revoke       string `json:"revoke-cert"`
-		RevokeRFC    string `json:"revokeCert"`
-		NonceRFC     string `json:"newNonce"`
-		KeyChangeRFC string `json:"keyChange"`
-		Meta         struct {
-			Terms           string   `json:"terms-of-service"`
-			TermsRFC        string   `json:"termsOfService"`
-			WebsiteRFC      string   `json:"website"`
-			CAA             []string `json:"caa-identities"`
-			CAARFC          []string `json:"caaIdentities"`
-			ExternalAcctRFC bool     `json:"externalAccountRequired"`
+		Reg       string `json:"newAccount"`
+		Authz     string `json:"newAuthz"`
+		Order     string `json:"newOrder"`
+		Revoke    string `json:"revokeCert"`
+		Nonce     string `json:"newNonce"`
+		KeyChange string `json:"keyChange"`
+		Meta      struct {
+			Terms        string   `json:"termsOfService"`
+			Website      string   `json:"website"`
+			CAA          []string `json:"caaIdentities"`
+			ExternalAcct bool     `json:"externalAccountRequired"`
 		}
 	}
 	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
 		return Directory{}, err
 	}
-	if v.OrderRFC == "" {
-		// Non-RFC compliant ACME CA.
-		c.dir = &Directory{
-			RegURL:    v.Reg,
-			AuthzURL:  v.Authz,
-			CertURL:   v.Cert,
-			RevokeURL: v.Revoke,
-			Terms:     v.Meta.Terms,
-			Website:   v.Meta.WebsiteRFC,
-			CAA:       v.Meta.CAA,
-		}
-		return *c.dir, nil
+	if v.Order == "" {
+		return Directory{}, errPreRFC
 	}
-	// RFC compliant ACME CA.
 	c.dir = &Directory{
-		RegURL:                  v.RegRFC,
-		AuthzURL:                v.AuthzRFC,
-		OrderURL:                v.OrderRFC,
-		RevokeURL:               v.RevokeRFC,
-		NonceURL:                v.NonceRFC,
-		KeyChangeURL:            v.KeyChangeRFC,
-		Terms:                   v.Meta.TermsRFC,
-		Website:                 v.Meta.WebsiteRFC,
-		CAA:                     v.Meta.CAARFC,
-		ExternalAccountRequired: v.Meta.ExternalAcctRFC,
+		RegURL:                  v.Reg,
+		AuthzURL:                v.Authz,
+		OrderURL:                v.Order,
+		RevokeURL:               v.Revoke,
+		NonceURL:                v.Nonce,
+		KeyChangeURL:            v.KeyChange,
+		Terms:                   v.Meta.Terms,
+		Website:                 v.Meta.Website,
+		CAA:                     v.Meta.CAA,
+		ExternalAccountRequired: v.Meta.ExternalAcct,
 	}
 	return *c.dir, nil
 }
@@ -235,55 +220,11 @@ func (c *Client) directoryURL() string {
 	return LetsEncryptURL
 }

-// CreateCert requests a new certificate using the Certificate Signing Request csr encoded in DER format.
-// It is incompatible with RFC 8555. Callers should use CreateOrderCert when interfacing
-// with an RFC-compliant CA.
+// CreateCert was part of the old version of ACME. It is incompatible with RFC 8555.
 //
-// The exp argument indicates the desired certificate validity duration. CA may issue a certificate
-// with a different duration.
-// If the bundle argument is true, the returned value will also contain the CA (issuer) certificate chain.
-//
-// In the case where CA server does not provide the issued certificate in the response,
-// CreateCert will poll certURL using c.FetchCert, which will result in additional round-trips.
-// In such a scenario, the caller can cancel the polling with ctx.
-//
-// CreateCert returns an error if the CA's response or chain was unreasonably large.
-// Callers are encouraged to parse the returned value to ensure the certificate is valid and has the expected features.
+// Deprecated: this was for the pre-RFC 8555 version of ACME. Callers should use CreateOrderCert.
 func (c *Client) CreateCert(ctx context.Context, csr []byte, exp time.Duration, bundle bool) (der [][]byte, certURL string, err error) {
-	if _, err := c.Discover(ctx); err != nil {
-		return nil, "", err
-	}
-
-	req := struct {
-		Resource  string `json:"resource"`
-		CSR       string `json:"csr"`
-		NotBefore string `json:"notBefore,omitempty"`
-		NotAfter  string `json:"notAfter,omitempty"`
-	}{
-		Resource: "new-cert",
-		CSR:      base64.RawURLEncoding.EncodeToString(csr),
-	}
-	now := timeNow()
-	req.NotBefore = now.Format(time.RFC3339)
-	if exp > 0 {
-		req.NotAfter = now.Add(exp).Format(time.RFC3339)
-	}
-
-	res, err := c.post(ctx, nil, c.dir.CertURL, req, wantStatus(http.StatusCreated))
-	if err != nil {
-		return nil, "", err
-	}
-	defer res.Body.Close()
-
-	curl := res.Header.Get("Location") // cert permanent URL
-	if res.ContentLength == 0 {
-		// no cert in the body; poll until we get it
-		cert, err := c.FetchCert(ctx, curl, bundle)
-		return cert, curl, err
-	}
-	// slurp issued cert and CA chain, if requested
-	cert, err := c.responseCert(ctx, res, bundle)
-	return cert, curl, err
+	return nil, "", errPreRFC
 }

 // FetchCert retrieves already issued certificate from the given url, in DER format.
@@ -297,20 +238,10 @@ func (c *Client) CreateCert(ctx context.Context, csr []byte, exp time.Duration,
 // Callers are encouraged to parse the returned value to ensure the certificate is valid
 // and has expected features.
 func (c *Client) FetchCert(ctx context.Context, url string, bundle bool) ([][]byte, error) {
-	dir, err := c.Discover(ctx)
-	if err != nil {
+	if _, err := c.Discover(ctx); err != nil {
 		return nil, err
 	}
-	if dir.rfcCompliant() {
-		return c.fetchCertRFC(ctx, url, bundle)
-	}
-
-	// Legacy non-authenticated GET request.
-	res, err := c.get(ctx, url, wantStatus(http.StatusOK))
-	if err != nil {
-		return nil, err
-	}
-	return c.responseCert(ctx, res, bundle)
+	return c.fetchCertRFC(ctx, url, bundle)
 }

 // RevokeCert revokes a previously issued certificate cert, provided in DER format.
@@ -320,30 +251,10 @@ func (c *Client) FetchCert(ctx context.Context, url string, bundle bool) ([][]by
 // For instance, the key pair of the certificate may be authorized.
 // If the key is nil, c.Key is used instead.
 func (c *Client) RevokeCert(ctx context.Context, key crypto.Signer, cert []byte, reason CRLReasonCode) error {
-	dir, err := c.Discover(ctx)
-	if err != nil {
+	if _, err := c.Discover(ctx); err != nil {
 		return err
 	}
-	if dir.rfcCompliant() {
-		return c.revokeCertRFC(ctx, key, cert, reason)
-	}
-
-	// Legacy CA.
-	body := &struct {
-		Resource string `json:"resource"`
-		Cert     string `json:"certificate"`
-		Reason   int    `json:"reason"`
-	}{
-		Resource: "revoke-cert",
-		Cert:     base64.RawURLEncoding.EncodeToString(cert),
-		Reason:   int(reason),
-	}
-	res, err := c.post(ctx, key, dir.RevokeURL, body, wantStatus(http.StatusOK))
-	if err != nil {
-		return err
-	}
-	defer res.Body.Close()
-	return nil
+	return c.revokeCertRFC(ctx, key, cert, reason)
 }

 // AcceptTOS always returns true to indicate the acceptance of a CA's Terms of Service
@@ -366,75 +277,47 @@ func (c *Client) Register(ctx context.Context, acct *Account, prompt func(tosURL
 	if c.Key == nil {
 		return nil, errors.New("acme: client.Key must be set to Register")
 	}
-
-	dir, err := c.Discover(ctx)
-	if err != nil {
+	if _, err := c.Discover(ctx); err != nil {
 		return nil, err
 	}
-	if dir.rfcCompliant() {
-		return c.registerRFC(ctx, acct, prompt)
-	}
-
-	// Legacy ACME draft registration flow.
-	a, err := c.doReg(ctx, dir.RegURL, "new-reg", acct)
-	if err != nil {
-		return nil, err
-	}
-	var accept bool
-	if a.CurrentTerms != "" && a.CurrentTerms != a.AgreedTerms {
-		accept = prompt(a.CurrentTerms)
-	}
-	if accept {
-		a.AgreedTerms = a.CurrentTerms
-		a, err = c.UpdateReg(ctx, a)
-	}
-	return a, err
+	return c.registerRFC(ctx, acct, prompt)
 }

 // GetReg retrieves an existing account associated with c.Key.
 //
-// The url argument is an Account URI used with pre-RFC 8555 CAs.
-// It is ignored when interfacing with an RFC-compliant CA.
+// The url argument is a legacy artifact of the pre-RFC 8555 API
+// and is ignored.
 func (c *Client) GetReg(ctx context.Context, url string) (*Account, error) {
-	dir, err := c.Discover(ctx)
-	if err != nil {
+	if _, err := c.Discover(ctx); err != nil {
 		return nil, err
 	}
-	if dir.rfcCompliant() {
-		return c.getRegRFC(ctx)
-	}
-
-	// Legacy CA.
-	a, err := c.doReg(ctx, url, "reg", nil)
-	if err != nil {
-		return nil, err
-	}
-	a.URI = url
-	return a, nil
+	return c.getRegRFC(ctx)
 }

 // UpdateReg updates an existing registration.
 // It returns an updated account copy. The provided account is not modified.
 //
-// When interfacing with RFC-compliant CAs, a.URI is ignored and the account URL
-// associated with c.Key is used instead.
+// The account's URI is ignored and the account URL associated with
+// c.Key is used instead.
 func (c *Client) UpdateReg(ctx context.Context, acct *Account) (*Account, error) {
-	dir, err := c.Discover(ctx)
-	if err != nil {
+	if _, err := c.Discover(ctx); err != nil {
 		return nil, err
 	}
-	if dir.rfcCompliant() {
-		return c.updateRegRFC(ctx, acct)
-	}
+	return c.updateRegRFC(ctx, acct)
+}

-	// Legacy CA.
-	uri := acct.URI
-	a, err := c.doReg(ctx, uri, "reg", acct)
-	if err != nil {
-		return nil, err
-	}
-	a.URI = uri
-	return a, nil
+// AccountKeyRollover attempts to transition a client's account key to a new key.
+// On success client's Key is updated which is not concurrency safe.
+// On failure an error will be returned.
+// The new key is already registered with the ACME provider if the following is true:
+//   - error is of type acme.Error
+//   - StatusCode should be 409 (Conflict)
+//   - Location header will have the KID of the associated account
+//
+// More about account key rollover can be found at
+// https://tools.ietf.org/html/rfc8555#section-7.3.5.
+func (c *Client) AccountKeyRollover(ctx context.Context, newKey crypto.Signer) error {
+	return c.accountKeyRollover(ctx, newKey)
 }

 // Authorize performs the initial step in the pre-authorization flow,
@@ -503,17 +386,11 @@ func (c *Client) authorize(ctx context.Context, typ, val string) (*Authorization
 // If a caller needs to poll an authorization until its status is final,
 // see the WaitAuthorization method.
 func (c *Client) GetAuthorization(ctx context.Context, url string) (*Authorization, error) {
-	dir, err := c.Discover(ctx)
-	if err != nil {
+	if _, err := c.Discover(ctx); err != nil {
 		return nil, err
 	}

-	var res *http.Response
-	if dir.rfcCompliant() {
-		res, err = c.postAsGet(ctx, url, wantStatus(http.StatusOK))
-	} else {
-		res, err = c.get(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
-	}
+	res, err := c.postAsGet(ctx, url, wantStatus(http.StatusOK))
 	if err != nil {
 		return nil, err
 	}
@@ -535,7 +412,6 @@ func (c *Client) GetAuthorization(ctx context.Context, url string) (*Authorizati
 //
 // It does not revoke existing certificates.
 func (c *Client) RevokeAuthorization(ctx context.Context, url string) error {
-	// Required for c.accountKID() when in RFC mode.
 	if _, err := c.Discover(ctx); err != nil {
 		return err
 	}
@@ -565,18 +441,11 @@ func (c *Client) RevokeAuthorization(ctx context.Context, url string) error {
 // In all other cases WaitAuthorization returns an error.
 // If the Status is StatusInvalid, the returned error is of type *AuthorizationError.
 func (c *Client) WaitAuthorization(ctx context.Context, url string) (*Authorization, error) {
-	// Required for c.accountKID() when in RFC mode.
-	dir, err := c.Discover(ctx)
-	if err != nil {
+	if _, err := c.Discover(ctx); err != nil {
 		return nil, err
 	}
-	getfn := c.postAsGet
-	if !dir.rfcCompliant() {
-		getfn = c.get
-	}
-
 	for {
-		res, err := getfn(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
+		res, err := c.postAsGet(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
 		if err != nil {
 			return nil, err
 		}
@@ -619,17 +488,11 @@ func (c *Client) WaitAuthorization(ctx context.Context, url string) (*Authorizat
 //
 // A client typically polls a challenge status using this method.
 func (c *Client) GetChallenge(ctx context.Context, url string) (*Challenge, error) {
-	// Required for c.accountKID() when in RFC mode.
-	dir, err := c.Discover(ctx)
-	if err != nil {
+	if _, err := c.Discover(ctx); err != nil {
 		return nil, err
 	}

-	getfn := c.postAsGet
-	if !dir.rfcCompliant() {
-		getfn = c.get
-	}
-	res, err := getfn(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
+	res, err := c.postAsGet(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
 	if err != nil {
 		return nil, err
 	}
@@ -647,29 +510,11 @@ func (c *Client) GetChallenge(ctx context.Context, url string) (*Challenge, erro
 //
 // The server will then perform the validation asynchronously.
 func (c *Client) Accept(ctx context.Context, chal *Challenge) (*Challenge, error) {
-	// Required for c.accountKID() when in RFC mode.
-	dir, err := c.Discover(ctx)
-	if err != nil {
+	if _, err := c.Discover(ctx); err != nil {
 		return nil, err
 	}

-	var req interface{} = json.RawMessage("{}") // RFC-compliant CA
-	if !dir.rfcCompliant() {
-		auth, err := keyAuth(c.Key.Public(), chal.Token)
-		if err != nil {
-			return nil, err
-		}
-		req = struct {
-			Resource string `json:"resource"`
-			Type     string `json:"type"`
-			Auth     string `json:"keyAuthorization"`
-		}{
-			Resource: "challenge",
-			Type:     chal.Type,
-			Auth:     auth,
-		}
-	}
-	res, err := c.post(ctx, nil, chal.URI, req, wantStatus(
+	res, err := c.post(ctx, nil, chal.URI, json.RawMessage("{}"), wantStatus(
 		http.StatusOK,       // according to the spec
 		http.StatusAccepted, // Let's Encrypt: see https://goo.gl/WsJ7VT (acme-divergences.md)
 	))
@@ -720,7 +565,7 @@ func (c *Client) HTTP01ChallengePath(token string) string {

 // TLSSNI01ChallengeCert creates a certificate for TLS-SNI-01 challenge response.
 //
-// Deprecated: This challenge type is unused in both draft-02 and RFC versions of ACME spec.
+// Deprecated: This challenge type is unused in both draft-02 and RFC versions of the ACME spec.
 func (c *Client) TLSSNI01ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) {
 	ka, err := keyAuth(c.Key.Public(), token)
 	if err != nil {
@@ -738,7 +583,7 @@ func (c *Client) TLSSNI01ChallengeCert(token string, opt ...CertOption) (cert tl

 // TLSSNI02ChallengeCert creates a certificate for TLS-SNI-02 challenge response.
 //
-// Deprecated: This challenge type is unused in both draft-02 and RFC versions of ACME spec.
+// Deprecated: This challenge type is unused in both draft-02 and RFC versions of the ACME spec.
 func (c *Client) TLSSNI02ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) {
 	b := sha256.Sum256([]byte(token))
 	h := hex.EncodeToString(b[:])
@@ -805,63 +650,6 @@ func (c *Client) TLSALPN01ChallengeCert(token, domain string, opt ...CertOption)
 	return tlsChallengeCert([]string{domain}, newOpt)
 }

-// doReg sends all types of registration requests the old way (pre-RFC world).
-// The type of request is identified by typ argument, which is a "resource"
-// in the ACME spec terms.
-//
-// A non-nil acct argument indicates whether the intention is to mutate data
-// of the Account. Only Contact and Agreement of its fields are used
-// in such cases.
-func (c *Client) doReg(ctx context.Context, url string, typ string, acct *Account) (*Account, error) {
-	req := struct {
-		Resource  string   `json:"resource"`
-		Contact   []string `json:"contact,omitempty"`
-		Agreement string   `json:"agreement,omitempty"`
-	}{
-		Resource: typ,
-	}
-	if acct != nil {
-		req.Contact = acct.Contact
-		req.Agreement = acct.AgreedTerms
-	}
-	res, err := c.post(ctx, nil, url, req, wantStatus(
-		http.StatusOK,       // updates and deletes
-		http.StatusCreated,  // new account creation
-		http.StatusAccepted, // Let's Encrypt divergent implementation
-	))
-	if err != nil {
-		return nil, err
-	}
-	defer res.Body.Close()
-
-	var v struct {
-		Contact        []string
-		Agreement      string
-		Authorizations string
-		Certificates   string
-	}
-	if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
-		return nil, fmt.Errorf("acme: invalid response: %v", err)
-	}
-	var tos string
-	if v := linkHeader(res.Header, "terms-of-service"); len(v) > 0 {
-		tos = v[0]
-	}
-	var authz string
-	if v := linkHeader(res.Header, "next"); len(v) > 0 {
-		authz = v[0]
-	}
-	return &Account{
-		URI:            res.Header.Get("Location"),
-		Contact:        v.Contact,
-		AgreedTerms:    v.Agreement,
-		CurrentTerms:   tos,
-		Authz:          authz,
-		Authorizations: v.Authorizations,
-		Certificates:   v.Certificates,
-	}, nil
-}
-
 // popNonce returns a nonce value previously stored with c.addNonce
 // or fetches a fresh one from c.dir.NonceURL.
 // If NonceURL is empty, it first tries c.directoryURL() and, failing that,
@@ -936,78 +724,6 @@ func nonceFromHeader(h http.Header) string {
 	return h.Get("Replay-Nonce")
 }

-func (c *Client) responseCert(ctx context.Context, res *http.Response, bundle bool) ([][]byte, error) {
-	b, err := ioutil.ReadAll(io.LimitReader(res.Body, maxCertSize+1))
-	if err != nil {
-		return nil, fmt.Errorf("acme: response stream: %v", err)
-	}
-	if len(b) > maxCertSize {
-		return nil, errors.New("acme: certificate is too big")
-	}
-	cert := [][]byte{b}
-	if !bundle {
-		return cert, nil
-	}
-
-	// Append CA chain cert(s).
-	// At least one is required according to the spec:
-	// https://tools.ietf.org/html/draft-ietf-acme-acme-03#section-6.3.1
-	up := linkHeader(res.Header, "up")
-	if len(up) == 0 {
-		return nil, errors.New("acme: rel=up link not found")
-	}
-	if len(up) > maxChainLen {
-		return nil, errors.New("acme: rel=up link is too large")
-	}
-	for _, url := range up {
-		cc, err := c.chainCert(ctx, url, 0)
-		if err != nil {
-			return nil, err
-		}
-		cert = append(cert, cc...)
-	}
-	return cert, nil
-}
-
-// chainCert fetches CA certificate chain recursively by following "up" links.
-// Each recursive call increments the depth by 1, resulting in an error
-// if the recursion level reaches maxChainLen.
-//
-// First chainCert call starts with depth of 0.
-func (c *Client) chainCert(ctx context.Context, url string, depth int) ([][]byte, error) {
-	if depth >= maxChainLen {
-		return nil, errors.New("acme: certificate chain is too deep")
-	}
-
-	res, err := c.get(ctx, url, wantStatus(http.StatusOK))
-	if err != nil {
-		return nil, err
-	}
-	defer res.Body.Close()
-	b, err := ioutil.ReadAll(io.LimitReader(res.Body, maxCertSize+1))
-	if err != nil {
-		return nil, err
-	}
-	if len(b) > maxCertSize {
-		return nil, errors.New("acme: certificate is too big")
-	}
-	chain := [][]byte{b}
-
-	uplink := linkHeader(res.Header, "up")
-	if len(uplink) > maxChainLen {
-		return nil, errors.New("acme: certificate chain is too large")
-	}
-	for _, up := range uplink {
-		cc, err := c.chainCert(ctx, up, depth+1)
-		if err != nil {
-			return nil, err
-		}
-		chain = append(chain, cc...)
-	}
-
-	return chain, nil
-}
-
 // linkHeader returns URI-Reference values of all Link headers
 // with relation-type rel.
 // See https://tools.ietf.org/html/rfc5988#section-5 for details.
@@ -1098,5 +814,5 @@ func encodePEM(typ string, b []byte) []byte {
 	return pem.EncodeToMemory(pb)
 }

-// timeNow is useful for testing for fixed current time.
+// timeNow is time.Now, except in tests which can mess with it.
 var timeNow = time.Now
@@ -79,115 +79,6 @@ func decodeJWSHead(r io.Reader) (*jwsHead, error) {
 	return &head, nil
 }

-func TestDiscover(t *testing.T) {
-	const (
-		reg    = "https://example.com/acme/new-reg"
-		authz  = "https://example.com/acme/new-authz"
-		cert   = "https://example.com/acme/new-cert"
-		revoke = "https://example.com/acme/revoke-cert"
-	)
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		w.Header().Set("Content-Type", "application/json")
-		w.Header().Set("Replay-Nonce", "testnonce")
-		fmt.Fprintf(w, `{
-			"new-reg": %q,
-			"new-authz": %q,
-			"new-cert": %q,
-			"revoke-cert": %q
-		}`, reg, authz, cert, revoke)
-	}))
-	defer ts.Close()
-	c := Client{DirectoryURL: ts.URL}
-	dir, err := c.Discover(context.Background())
-	if err != nil {
-		t.Fatal(err)
-	}
-	if dir.RegURL != reg {
-		t.Errorf("dir.RegURL = %q; want %q", dir.RegURL, reg)
-	}
-	if dir.AuthzURL != authz {
-		t.Errorf("dir.AuthzURL = %q; want %q", dir.AuthzURL, authz)
-	}
-	if dir.CertURL != cert {
-		t.Errorf("dir.CertURL = %q; want %q", dir.CertURL, cert)
-	}
-	if dir.RevokeURL != revoke {
-		t.Errorf("dir.RevokeURL = %q; want %q", dir.RevokeURL, revoke)
-	}
-	if _, exist := c.nonces["testnonce"]; !exist {
-		t.Errorf("c.nonces = %q; want 'testnonce' in the map", c.nonces)
-	}
-}
-
-func TestRegister(t *testing.T) {
-	contacts := []string{"mailto:admin@example.com"}
-
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method == "HEAD" {
-			w.Header().Set("Replay-Nonce", "test-nonce")
-			return
-		}
-		if r.Method != "POST" {
-			t.Errorf("r.Method = %q; want POST", r.Method)
-		}
-
-		var j struct {
-			Resource  string
-			Contact   []string
-			Agreement string
-		}
-		decodeJWSRequest(t, &j, r.Body)
-
-		// Test request
-		if j.Resource != "new-reg" {
-			t.Errorf("j.Resource = %q; want new-reg", j.Resource)
-		}
-		if !reflect.DeepEqual(j.Contact, contacts) {
-			t.Errorf("j.Contact = %v; want %v", j.Contact, contacts)
-		}
-
-		w.Header().Set("Location", "https://ca.tld/acme/reg/1")
-		w.Header().Set("Link", `<https://ca.tld/acme/new-authz>;rel="next"`)
-		w.Header().Add("Link", `<https://ca.tld/acme/recover-reg>;rel="recover"`)
-		w.Header().Add("Link", `<https://ca.tld/acme/terms>;rel="terms-of-service"`)
-		w.WriteHeader(http.StatusCreated)
-		b, _ := json.Marshal(contacts)
-		fmt.Fprintf(w, `{"contact": %s}`, b)
-	}))
-	defer ts.Close()
-
-	prompt := func(url string) bool {
-		const terms = "https://ca.tld/acme/terms"
-		if url != terms {
-			t.Errorf("prompt url = %q; want %q", url, terms)
-		}
-		return false
-	}
-
-	c := Client{
-		Key:          testKeyEC,
-		DirectoryURL: ts.URL,
-		dir:          &Directory{RegURL: ts.URL},
-	}
-	a := &Account{Contact: contacts}
-	var err error
-	if a, err = c.Register(context.Background(), a, prompt); err != nil {
-		t.Fatal(err)
-	}
-	if a.URI != "https://ca.tld/acme/reg/1" {
-		t.Errorf("a.URI = %q; want https://ca.tld/acme/reg/1", a.URI)
-	}
-	if a.Authz != "https://ca.tld/acme/new-authz" {
-		t.Errorf("a.Authz = %q; want https://ca.tld/acme/new-authz", a.Authz)
-	}
-	if a.CurrentTerms != "https://ca.tld/acme/terms" {
-		t.Errorf("a.CurrentTerms = %q; want https://ca.tld/acme/terms", a.CurrentTerms)
-	}
-	if !reflect.DeepEqual(a.Contact, contacts) {
-		t.Errorf("a.Contact = %v; want %v", a.Contact, contacts)
-	}
-}
-
 func TestRegisterWithoutKey(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.Method == "HEAD" {
@@ -213,134 +104,6 @@ func TestRegisterWithoutKey(t *testing.T) {
 	}
 }

-func TestUpdateReg(t *testing.T) {
-	const terms = "https://ca.tld/acme/terms"
-	contacts := []string{"mailto:admin@example.com"}
-
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method == "HEAD" {
-			w.Header().Set("Replay-Nonce", "test-nonce")
-			return
-		}
-		if r.Method != "POST" {
-			t.Errorf("r.Method = %q; want POST", r.Method)
-		}
-
-		var j struct {
-			Resource  string
-			Contact   []string
-			Agreement string
-		}
-		decodeJWSRequest(t, &j, r.Body)
-
-		// Test request
-		if j.Resource != "reg" {
-			t.Errorf("j.Resource = %q; want reg", j.Resource)
-		}
-		if j.Agreement != terms {
-			t.Errorf("j.Agreement = %q; want %q", j.Agreement, terms)
-		}
-		if !reflect.DeepEqual(j.Contact, contacts) {
-			t.Errorf("j.Contact = %v; want %v", j.Contact, contacts)
-		}
-
-		w.Header().Set("Link", `<https://ca.tld/acme/new-authz>;rel="next"`)
-		w.Header().Add("Link", `<https://ca.tld/acme/recover-reg>;rel="recover"`)
-		w.Header().Add("Link", fmt.Sprintf(`<%s>;rel="terms-of-service"`, terms))
-		w.WriteHeader(http.StatusOK)
-		b, _ := json.Marshal(contacts)
-		fmt.Fprintf(w, `{"contact":%s, "agreement":%q}`, b, terms)
-	}))
-	defer ts.Close()
-
-	c := Client{
-		Key:          testKeyEC,
-		DirectoryURL: ts.URL,       // don't dial outside of localhost
-		dir:          &Directory{}, // don't do discovery
-	}
-	a := &Account{URI: ts.URL, Contact: contacts, AgreedTerms: terms}
-	var err error
-	if a, err = c.UpdateReg(context.Background(), a); err != nil {
-		t.Fatal(err)
-	}
-	if a.Authz != "https://ca.tld/acme/new-authz" {
-		t.Errorf("a.Authz = %q; want https://ca.tld/acme/new-authz", a.Authz)
-	}
-	if a.AgreedTerms != terms {
-		t.Errorf("a.AgreedTerms = %q; want %q", a.AgreedTerms, terms)
-	}
-	if a.CurrentTerms != terms {
-		t.Errorf("a.CurrentTerms = %q; want %q", a.CurrentTerms, terms)
-	}
-	if a.URI != ts.URL {
-		t.Errorf("a.URI = %q; want %q", a.URI, ts.URL)
-	}
-}
-
-func TestGetReg(t *testing.T) {
-	const terms = "https://ca.tld/acme/terms"
-	const newTerms = "https://ca.tld/acme/new-terms"
-	contacts := []string{"mailto:admin@example.com"}
-
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method == "HEAD" {
-			w.Header().Set("Replay-Nonce", "test-nonce")
-			return
-		}
-		if r.Method != "POST" {
-			t.Errorf("r.Method = %q; want POST", r.Method)
-		}
-
-		var j struct {
-			Resource  string
-			Contact   []string
-			Agreement string
-		}
-		decodeJWSRequest(t, &j, r.Body)
-
-		// Test request
-		if j.Resource != "reg" {
-			t.Errorf("j.Resource = %q; want reg", j.Resource)
-		}
-		if len(j.Contact) != 0 {
-			t.Errorf("j.Contact = %v", j.Contact)
-		}
-		if j.Agreement != "" {
-			t.Errorf("j.Agreement = %q", j.Agreement)
-		}
-
-		w.Header().Set("Link", `<https://ca.tld/acme/new-authz>;rel="next"`)
-		w.Header().Add("Link", `<https://ca.tld/acme/recover-reg>;rel="recover"`)
-		w.Header().Add("Link", fmt.Sprintf(`<%s>;rel="terms-of-service"`, newTerms))
-		w.WriteHeader(http.StatusOK)
-		b, _ := json.Marshal(contacts)
-		fmt.Fprintf(w, `{"contact":%s, "agreement":%q}`, b, terms)
-	}))
-	defer ts.Close()
-
-	c := Client{
-		Key:          testKeyEC,
-		DirectoryURL: ts.URL,       // don't dial outside of localhost
-		dir:          &Directory{}, // don't do discovery
-	}
-	a, err := c.GetReg(context.Background(), ts.URL)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if a.Authz != "https://ca.tld/acme/new-authz" {
-		t.Errorf("a.AuthzURL = %q; want https://ca.tld/acme/new-authz", a.Authz)
-	}
-	if a.AgreedTerms != terms {
-		t.Errorf("a.AgreedTerms = %q; want %q", a.AgreedTerms, terms)
-	}
-	if a.CurrentTerms != newTerms {
-		t.Errorf("a.CurrentTerms = %q; want %q", a.CurrentTerms, newTerms)
-	}
-	if a.URI != ts.URL {
-		t.Errorf("a.URI = %q; want %q", a.URI, ts.URL)
-	}
-}
-
 func TestAuthorize(t *testing.T) {
 	tt := []struct{ typ, value string }{
 		{"dns", "example.com"},
@@ -491,82 +254,6 @@ func TestAuthorizeValid(t *testing.T) {
 	}
 }

-func TestGetAuthorization(t *testing.T) {
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method != "GET" {
-			t.Errorf("r.Method = %q; want GET", r.Method)
-		}
-
-		w.WriteHeader(http.StatusOK)
-		fmt.Fprintf(w, `{
-			"identifier": {"type":"dns","value":"example.com"},
-			"status":"pending",
-			"challenges":[
-				{
-					"type":"http-01",
-					"status":"pending",
-					"uri":"https://ca.tld/acme/challenge/publickey/id1",
-					"token":"token1"
-				},
-				{
-					"type":"tls-sni-01",
-					"status":"pending",
-					"uri":"https://ca.tld/acme/challenge/publickey/id2",
-					"token":"token2"
-				}
-			],
-			"combinations":[[0],[1]]}`)
-	}))
-	defer ts.Close()
-
-	cl := Client{Key: testKeyEC, DirectoryURL: ts.URL}
-	auth, err := cl.GetAuthorization(context.Background(), ts.URL)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if auth.Status != "pending" {
-		t.Errorf("Status = %q; want pending", auth.Status)
-	}
-	if auth.Identifier.Type != "dns" {
-		t.Errorf("Identifier.Type = %q; want dns", auth.Identifier.Type)
-	}
-	if auth.Identifier.Value != "example.com" {
-		t.Errorf("Identifier.Value = %q; want example.com", auth.Identifier.Value)
-	}
-
-	if n := len(auth.Challenges); n != 2 {
-		t.Fatalf("len(set.Challenges) = %d; want 2", n)
-	}
-
-	c := auth.Challenges[0]
-	if c.Type != "http-01" {
-		t.Errorf("c.Type = %q; want http-01", c.Type)
-	}
-	if c.URI != "https://ca.tld/acme/challenge/publickey/id1" {
-		t.Errorf("c.URI = %q; want https://ca.tld/acme/challenge/publickey/id1", c.URI)
-	}
-	if c.Token != "token1" {
-		t.Errorf("c.Token = %q; want token1", c.Token)
-	}
-
-	c = auth.Challenges[1]
-	if c.Type != "tls-sni-01" {
-		t.Errorf("c.Type = %q; want tls-sni-01", c.Type)
-	}
-	if c.URI != "https://ca.tld/acme/challenge/publickey/id2" {
-		t.Errorf("c.URI = %q; want https://ca.tld/acme/challenge/publickey/id2", c.URI)
-	}
-	if c.Token != "token2" {
-		t.Errorf("c.Token = %q; want token2", c.Token)
-	}
-
-	combs := [][]int{{0}, {1}}
-	if !reflect.DeepEqual(auth.Combinations, combs) {
-		t.Errorf("auth.Combinations: %+v\nwant: %+v\n", auth.Combinations, combs)
-	}
-}
-
 func TestWaitAuthorization(t *testing.T) {
 	t.Run("wait loop", func(t *testing.T) {
 		var count int
@@ -667,38 +354,34 @@ func TestWaitAuthorization(t *testing.T) {
 		})
 	}
 	t.Run("context cancel", func(t *testing.T) {
-		ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
+		ctx, cancel := context.WithCancel(context.Background())
 		defer cancel()
 		_, err := runWaitAuthorization(ctx, t, func(w http.ResponseWriter, r *http.Request) {
 			w.Header().Set("Retry-After", "60")
 			fmt.Fprintf(w, `{"status":"pending"}`)
+			time.AfterFunc(1*time.Millisecond, cancel)
 		})
 		if err == nil {
 			t.Error("err is nil")
 		}
 	})
 }
+
 func runWaitAuthorization(ctx context.Context, t *testing.T, h http.HandlerFunc) (*Authorization, error) {
 	t.Helper()
-	ts := httptest.NewServer(h)
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Replay-Nonce", fmt.Sprintf("bad-test-nonce-%v", time.Now().UnixNano()))
+		h(w, r)
+	}))
 	defer ts.Close()
-	type res struct {
-		authz *Authorization
-		err   error
+
+	client := &Client{
+		Key:          testKey,
+		DirectoryURL: ts.URL,
+		dir:          &Directory{},
+		KID:          "some-key-id", // set to avoid lookup attempt
 	}
-	ch := make(chan res, 1)
-	go func() {
-		var client = Client{DirectoryURL: ts.URL}
-		a, err := client.WaitAuthorization(ctx, ts.URL)
-		ch <- res{a, err}
-	}()
-	select {
-	case <-time.After(3 * time.Second):
-		t.Fatal("WaitAuthorization took too long to return")
-	case v := <-ch:
-		return v.authz, v.err
-	}
-	panic("runWaitAuthorization: out of select")
+	return client.WaitAuthorization(ctx, ts.URL)
 }

 func TestRevokeAuthorization(t *testing.T) {
@@ -743,238 +426,9 @@ func TestRevokeAuthorization(t *testing.T) {
 	}
 }

-func TestPollChallenge(t *testing.T) {
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method != "GET" {
-			t.Errorf("r.Method = %q; want GET", r.Method)
-		}
-
-		w.WriteHeader(http.StatusOK)
-		fmt.Fprintf(w, `{
-			"type":"http-01",
-			"status":"pending",
-			"uri":"https://ca.tld/acme/challenge/publickey/id1",
-			"token":"token1"}`)
-	}))
-	defer ts.Close()
-
-	cl := Client{Key: testKeyEC, DirectoryURL: ts.URL}
-	chall, err := cl.GetChallenge(context.Background(), ts.URL)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if chall.Status != "pending" {
-		t.Errorf("Status = %q; want pending", chall.Status)
-	}
-	if chall.Type != "http-01" {
-		t.Errorf("c.Type = %q; want http-01", chall.Type)
-	}
-	if chall.URI != "https://ca.tld/acme/challenge/publickey/id1" {
-		t.Errorf("c.URI = %q; want https://ca.tld/acme/challenge/publickey/id1", chall.URI)
-	}
-	if chall.Token != "token1" {
-		t.Errorf("c.Token = %q; want token1", chall.Token)
-	}
-}
-
-func TestAcceptChallenge(t *testing.T) {
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method == "HEAD" {
-			w.Header().Set("Replay-Nonce", "test-nonce")
-			return
-		}
-		if r.Method != "POST" {
-			t.Errorf("r.Method = %q; want POST", r.Method)
-		}
-
-		var j struct {
-			Resource string
-			Type     string
-			Auth     string `json:"keyAuthorization"`
-		}
-		decodeJWSRequest(t, &j, r.Body)
-
-		// Test request
-		if j.Resource != "challenge" {
-			t.Errorf(`resource = %q; want "challenge"`, j.Resource)
-		}
-		if j.Type != "http-01" {
-			t.Errorf(`type = %q; want "http-01"`, j.Type)
-		}
-		keyAuth := "token1." + testKeyECThumbprint
-		if j.Auth != keyAuth {
-			t.Errorf(`keyAuthorization = %q; want %q`, j.Auth, keyAuth)
-		}
-
-		// Respond to request
-		w.WriteHeader(http.StatusAccepted)
-		fmt.Fprintf(w, `{
-			"type":"http-01",
-			"status":"pending",
-			"uri":"https://ca.tld/acme/challenge/publickey/id1",
-			"token":"token1",
-			"keyAuthorization":%q
-		}`, keyAuth)
-	}))
-	defer ts.Close()
-
-	cl := Client{
-		Key:          testKeyEC,
-		DirectoryURL: ts.URL,       // don't dial outside of localhost
-		dir:          &Directory{}, // don't do discovery
-	}
-	c, err := cl.Accept(context.Background(), &Challenge{
-		URI:   ts.URL,
-		Token: "token1",
-		Type:  "http-01",
-	})
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if c.Type != "http-01" {
-		t.Errorf("c.Type = %q; want http-01", c.Type)
-	}
-	if c.URI != "https://ca.tld/acme/challenge/publickey/id1" {
-		t.Errorf("c.URI = %q; want https://ca.tld/acme/challenge/publickey/id1", c.URI)
-	}
-	if c.Token != "token1" {
-		t.Errorf("c.Token = %q; want token1", c.Token)
-	}
-}
-
-func TestNewCert(t *testing.T) {
-	notBefore := time.Now()
-	notAfter := notBefore.AddDate(0, 2, 0)
-	timeNow = func() time.Time { return notBefore }
-
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method == "HEAD" {
-			w.Header().Set("Replay-Nonce", "test-nonce")
-			return
-		}
-		if r.Method != "POST" {
-			t.Errorf("r.Method = %q; want POST", r.Method)
-		}
-
-		var j struct {
-			Resource  string `json:"resource"`
-			CSR       string `json:"csr"`
-			NotBefore string `json:"notBefore,omitempty"`
-			NotAfter  string `json:"notAfter,omitempty"`
-		}
-		decodeJWSRequest(t, &j, r.Body)
-
-		// Test request
-		if j.Resource != "new-cert" {
-			t.Errorf(`resource = %q; want "new-cert"`, j.Resource)
-		}
-		if j.NotBefore != notBefore.Format(time.RFC3339) {
-			t.Errorf(`notBefore = %q; wanted %q`, j.NotBefore, notBefore.Format(time.RFC3339))
-		}
-		if j.NotAfter != notAfter.Format(time.RFC3339) {
-			t.Errorf(`notAfter = %q; wanted %q`, j.NotAfter, notAfter.Format(time.RFC3339))
-		}
-
-		// Respond to request
-		template := x509.Certificate{
-			SerialNumber: big.NewInt(int64(1)),
-			Subject: pkix.Name{
-				Organization: []string{"goacme"},
-			},
-			NotBefore: notBefore,
-			NotAfter:  notAfter,
-
-			KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
-			ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
-			BasicConstraintsValid: true,
-		}
-
-		sampleCert, err := x509.CreateCertificate(rand.Reader, &template, &template, &testKeyEC.PublicKey, testKeyEC)
-		if err != nil {
-			t.Fatalf("Error creating certificate: %v", err)
-		}
-
-		w.Header().Set("Location", "https://ca.tld/acme/cert/1")
-		w.WriteHeader(http.StatusCreated)
-		w.Write(sampleCert)
-	}))
-	defer ts.Close()
-
-	csr := x509.CertificateRequest{
-		Version: 0,
-		Subject: pkix.Name{
-			CommonName:   "example.com",
-			Organization: []string{"goacme"},
-		},
-	}
-	csrb, err := x509.CreateCertificateRequest(rand.Reader, &csr, testKeyEC)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	c := Client{Key: testKeyEC, dir: &Directory{CertURL: ts.URL}}
-	cert, certURL, err := c.CreateCert(context.Background(), csrb, notAfter.Sub(notBefore), false)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if cert == nil {
-		t.Errorf("cert is nil")
-	}
-	if certURL != "https://ca.tld/acme/cert/1" {
-		t.Errorf("certURL = %q; want https://ca.tld/acme/cert/1", certURL)
-	}
-}
-
-func TestFetchCert(t *testing.T) {
-	var count byte
-	var ts *httptest.Server
-	ts = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		count++
-		if count < 3 {
-			up := fmt.Sprintf("<%s>;rel=up", ts.URL)
-			w.Header().Set("Link", up)
-		}
-		w.Write([]byte{count})
-	}))
-	defer ts.Close()
-	cl := newTestClient()
-	res, err := cl.FetchCert(context.Background(), ts.URL, true)
-	if err != nil {
-		t.Fatalf("FetchCert: %v", err)
-	}
-	cert := [][]byte{{1}, {2}, {3}}
-	if !reflect.DeepEqual(res, cert) {
-		t.Errorf("res = %v; want %v", res, cert)
-	}
-}
-
-func TestFetchCertRetry(t *testing.T) {
-	var count int
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if count < 1 {
-			w.Header().Set("Retry-After", "0")
-			w.WriteHeader(http.StatusTooManyRequests)
-			count++
-			return
-		}
-		w.Write([]byte{1})
-	}))
-	defer ts.Close()
-	cl := newTestClient()
-	res, err := cl.FetchCert(context.Background(), ts.URL, false)
-	if err != nil {
-		t.Fatalf("FetchCert: %v", err)
-	}
-	cert := [][]byte{{1}}
-	if !reflect.DeepEqual(res, cert) {
-		t.Errorf("res = %v; want %v", res, cert)
-	}
-}
-
 func TestFetchCertCancel(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		<-r.Context().Done()
 		w.Header().Set("Retry-After", "0")
 		w.WriteHeader(http.StatusBadRequest)
 	}))
@@ -1043,42 +497,6 @@ func TestFetchCertSize(t *testing.T) {
 	}
 }

-func TestRevokeCert(t *testing.T) {
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method == "HEAD" {
-			w.Header().Set("Replay-Nonce", "nonce")
-			return
-		}
-
-		var req struct {
-			Resource    string
-			Certificate string
-			Reason      int
-		}
-		decodeJWSRequest(t, &req, r.Body)
-		if req.Resource != "revoke-cert" {
-			t.Errorf("req.Resource = %q; want revoke-cert", req.Resource)
-		}
-		if req.Reason != 1 {
-			t.Errorf("req.Reason = %d; want 1", req.Reason)
-		}
-		// echo -n cert | base64 | tr -d '=' | tr '/+' '_-'
-		cert := "Y2VydA"
-		if req.Certificate != cert {
-			t.Errorf("req.Certificate = %q; want %q", req.Certificate, cert)
-		}
-	}))
-	defer ts.Close()
-	client := &Client{
-		Key: testKeyEC,
-		dir: &Directory{RevokeURL: ts.URL},
-	}
-	ctx := context.Background()
-	if err := client.RevokeCert(ctx, nil, []byte("cert"), CRLReasonKeyCompromise); err != nil {
-		t.Fatal(err)
-	}
-}
-
 func TestNonce_add(t *testing.T) {
 	var c Client
 	c.addNonce(http.Header{"Replay-Nonce": {"nonce"}})
@@ -1199,65 +617,6 @@ func TestNonce_popWhenEmpty(t *testing.T) {
 	}
 }

-func TestNonce_postJWS(t *testing.T) {
-	var count int
-	seen := make(map[string]bool)
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		count++
-		w.Header().Set("Replay-Nonce", fmt.Sprintf("nonce%d", count))
-		if r.Method == "HEAD" {
-			// We expect the client do a HEAD request
-			// but only to fetch the first nonce.
-			return
-		}
-		// Make client.Authorize happy; we're not testing its result.
-		defer func() {
-			w.WriteHeader(http.StatusCreated)
-			w.Write([]byte(`{"status":"valid"}`))
-		}()
-
-		head, err := decodeJWSHead(r.Body)
-		if err != nil {
-			t.Errorf("decodeJWSHead: %v", err)
-			return
-		}
-		if head.Nonce == "" {
-			t.Error("head.Nonce is empty")
-			return
-		}
-		if seen[head.Nonce] {
-			t.Errorf("nonce is already used: %q", head.Nonce)
-		}
-		seen[head.Nonce] = true
-	}))
-	defer ts.Close()
-
-	client := Client{
-		Key:          testKey,
-		DirectoryURL: ts.URL, // nonces are fetched from here first
-		dir:          &Directory{AuthzURL: ts.URL},
-	}
-	if _, err := client.Authorize(context.Background(), "example.com"); err != nil {
-		t.Errorf("client.Authorize 1: %v", err)
-	}
-	// The second call should not generate another extra HEAD request.
-	if _, err := client.Authorize(context.Background(), "example.com"); err != nil {
-		t.Errorf("client.Authorize 2: %v", err)
-	}
-
-	if count != 3 {
-		t.Errorf("total requests count: %d; want 3", count)
-	}
-	if n := len(client.nonces); n != 1 {
-		t.Errorf("len(client.nonces) = %d; want 1", n)
-	}
-	for k := range seen {
-		if _, exist := client.nonces[k]; exist {
-			t.Errorf("used nonce %q in client.nonces", k)
-		}
-	}
-}
-
 func TestLinkHeader(t *testing.T) {
 	h := http.Header{"Link": {
 		`<https://example.com/acme/new-authz>;rel="next"`,
@@ -47,6 +47,8 @@ var createCertRetryAfter = time.Minute
 // pseudoRand is safe for concurrent use.
 var pseudoRand *lockedMathRand

+var errPreRFC = errors.New("autocert: ACME server doesn't support RFC 8555")
+
 func init() {
 	src := mathrand.NewSource(time.Now().UnixNano())
 	pseudoRand = &lockedMathRand{rnd: mathrand.New(src)}
@@ -168,6 +170,11 @@ type Manager struct {
 	// in the template's ExtraExtensions field as is.
 	ExtraExtensions []pkix.Extension

+	// ExternalAccountBinding optionally represents an arbitrary binding to an
+	// account of the CA to which the ACME server is tied.
+	// See RFC 8555, Section 7.3.4 for more details.
+	ExternalAccountBinding *acme.ExternalAccountBinding
+
 	clientMu sync.Mutex
 	client   *acme.Client // initialized by acmeClient method

@@ -456,7 +463,7 @@ func (m *Manager) cert(ctx context.Context, ck certKey) (*tls.Certificate, error
 		leaf: cert.Leaf,
 	}
 	m.state[ck] = s
-	go m.renew(ck, s.key, s.leaf.NotAfter)
+	m.startRenew(ck, s.key, s.leaf.NotAfter)
 	return cert, nil
 }

@@ -582,8 +589,9 @@ func (m *Manager) createCert(ctx context.Context, ck certKey) (*tls.Certificate,
 	if err != nil {
 		// Remove the failed state after some time,
 		// making the manager call createCert again on the following TLS hello.
+		didRemove := testDidRemoveState // The lifetime of this timer is untracked, so copy mutable local state to avoid races.
 		time.AfterFunc(createCertRetryAfter, func() {
-			defer testDidRemoveState(ck)
+			defer didRemove(ck)
 			m.stateMu.Lock()
 			defer m.stateMu.Unlock()
 			// Verify the state hasn't changed and it's still invalid
@@ -601,7 +609,7 @@ func (m *Manager) createCert(ctx context.Context, ck certKey) (*tls.Certificate,
 	}
 	state.cert = der
 	state.leaf = leaf
-	go m.renew(ck, state.key, state.leaf.NotAfter)
+	m.startRenew(ck, state.key, state.leaf.NotAfter)
 	return state.tlscert()
 }

@@ -658,31 +666,19 @@ func (m *Manager) authorizedCert(ctx context.Context, key crypto.Signer, ck cert
 	if err != nil {
 		return nil, nil, err
 	}
-
-	var chain [][]byte
-	switch {
-	// Pre-RFC legacy CA.
-	case dir.OrderURL == "":
-		if err := m.verify(ctx, client, ck.domain); err != nil {
-			return nil, nil, err
-		}
-		der, _, err := client.CreateCert(ctx, csr, 0, true)
-		if err != nil {
-			return nil, nil, err
-		}
-		chain = der
-	// RFC 8555 compliant CA.
-	default:
-		o, err := m.verifyRFC(ctx, client, ck.domain)
-		if err != nil {
-			return nil, nil, err
-		}
-		der, _, err := client.CreateOrderCert(ctx, o.FinalizeURL, csr, true)
-		if err != nil {
-			return nil, nil, err
-		}
-		chain = der
+	if dir.OrderURL == "" {
+		return nil, nil, errPreRFC
 	}
+
+	o, err := m.verifyRFC(ctx, client, ck.domain)
+	if err != nil {
+		return nil, nil, err
+	}
+	chain, _, err := client.CreateOrderCert(ctx, o.FinalizeURL, csr, true)
+	if err != nil {
+		return nil, nil, err
+	}
+
 	leaf, err = validCert(ck, chain, key, m.now())
 	if err != nil {
 		return nil, nil, err
@@ -690,69 +686,6 @@ func (m *Manager) authorizedCert(ctx context.Context, key crypto.Signer, ck cert
 	return chain, leaf, nil
 }

-// verify runs the identifier (domain) pre-authorization flow for legacy CAs
-// using each applicable ACME challenge type.
-func (m *Manager) verify(ctx context.Context, client *acme.Client, domain string) error {
-	// Remove all hanging authorizations to reduce rate limit quotas
-	// after we're done.
-	var authzURLs []string
-	defer func() {
-		go m.deactivatePendingAuthz(authzURLs)
-	}()
-
-	// errs accumulates challenge failure errors, printed if all fail
-	errs := make(map[*acme.Challenge]error)
-	challengeTypes := m.supportedChallengeTypes()
-	var nextTyp int // challengeType index of the next challenge type to try
-	for {
-		// Start domain authorization and get the challenge.
-		authz, err := client.Authorize(ctx, domain)
-		if err != nil {
-			return err
-		}
-		authzURLs = append(authzURLs, authz.URI)
-		// No point in accepting challenges if the authorization status
-		// is in a final state.
-		switch authz.Status {
-		case acme.StatusValid:
-			return nil // already authorized
-		case acme.StatusInvalid:
-			return fmt.Errorf("acme/autocert: invalid authorization %q", authz.URI)
-		}
-
-		// Pick the next preferred challenge.
-		var chal *acme.Challenge
-		for chal == nil && nextTyp < len(challengeTypes) {
-			chal = pickChallenge(challengeTypes[nextTyp], authz.Challenges)
-			nextTyp++
-		}
-		if chal == nil {
-			errorMsg := fmt.Sprintf("acme/autocert: unable to authorize %q", domain)
-			for chal, err := range errs {
-				errorMsg += fmt.Sprintf("; challenge %q failed with error: %v", chal.Type, err)
-			}
-			return errors.New(errorMsg)
-		}
-		cleanup, err := m.fulfill(ctx, client, chal, domain)
-		if err != nil {
-			errs[chal] = err
-			continue
-		}
-		defer cleanup()
-		if _, err := client.Accept(ctx, chal); err != nil {
-			errs[chal] = err
-			continue
-		}
-
-		// A challenge is fulfilled and accepted: wait for the CA to validate.
-		if _, err := client.WaitAuthorization(ctx, authz.URI); err != nil {
-			errs[chal] = err
-			continue
-		}
-		return nil
-	}
-}
-
 // verifyRFC runs the identifier (domain) order-based authorization flow for RFC compliant CAs
 // using each applicable ACME challenge type.
 func (m *Manager) verifyRFC(ctx context.Context, client *acme.Client, domain string) (*acme.Order, error) {
@@ -966,7 +899,7 @@ func httpTokenCacheKey(tokenPath string) string {
 	return path.Base(tokenPath) + "+http-01"
 }

-// renew starts a cert renewal timer loop, one per domain.
+// startRenew starts a cert renewal timer loop, one per domain.
 //
 // The loop is scheduled in two cases:
 // - a cert was fetched from cache for the first time (wasn't in m.state)
@@ -974,7 +907,7 @@ func httpTokenCacheKey(tokenPath string) string {
 //
 // The key argument is a certificate private key.
 // The exp argument is the cert expiration time (NotAfter).
-func (m *Manager) renew(ck certKey, key crypto.Signer, exp time.Time) {
+func (m *Manager) startRenew(ck certKey, key crypto.Signer, exp time.Time) {
 	m.renewalMu.Lock()
 	defer m.renewalMu.Unlock()
 	if m.renewal[ck] != nil {
@@ -1068,7 +1001,7 @@ func (m *Manager) acmeClient(ctx context.Context) (*acme.Client, error) {
 	if m.Email != "" {
 		contact = []string{"mailto:" + m.Email}
 	}
-	a := &acme.Account{Contact: contact}
+	a := &acme.Account{Contact: contact, ExternalAccountBinding: m.ExternalAccountBinding}
 	_, err := client.Register(ctx, a, m.Prompt)
 	if err == nil || isAccountAlreadyExist(err) {
 		m.client = client
@@ -1200,6 +1133,10 @@ func validCert(ck certKey, der [][]byte, key crypto.Signer, now time.Time) (leaf
 	if err := leaf.VerifyHostname(ck.domain); err != nil {
 		return nil, err
 	}
+	// renew certificates revoked by Let's Encrypt in January 2022
+	if isRevokedLetsEncrypt(leaf) {
+		return nil, errors.New("acme/autocert: certificate was probably revoked by Let's Encrypt")
+	}
 	// ensure the leaf corresponds to the private key and matches the certKey type
 	switch pub := leaf.PublicKey.(type) {
 	case *rsa.PublicKey:
@@ -1230,6 +1167,18 @@ func validCert(ck certKey, der [][]byte, key crypto.Signer, now time.Time) (leaf
 	return leaf, nil
 }

+// https://community.letsencrypt.org/t/2022-01-25-issue-with-tls-alpn-01-validation-method/170450
+var letsEncryptFixDeployTime = time.Date(2022, time.January, 26, 00, 48, 0, 0, time.UTC)
+
+// isRevokedLetsEncrypt returns whether the certificate is likely to be part of
+// a batch of certificates revoked by Let's Encrypt in January 2022. This check
+// can be safely removed from May 2022.
+func isRevokedLetsEncrypt(cert *x509.Certificate) bool {
+	O := cert.Issuer.Organization
+	return len(O) == 1 && O[0] == "Let's Encrypt" &&
+		cert.NotBefore.Before(letsEncryptFixDeployTime)
+}
+
 type lockedMathRand struct {
 	sync.Mutex
 	rnd *mathrand.Rand
@@ -7,7 +7,6 @@ package autocert
 import (
 	"context"
 	"errors"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 )
@@ -41,14 +40,14 @@ type DirCache string

 // Get reads a certificate data from the specified file name.
 func (d DirCache) Get(ctx context.Context, name string) ([]byte, error) {
-	name = filepath.Join(string(d), name)
+	name = filepath.Join(string(d), filepath.Clean("/"+name))
 	var (
 		data []byte
 		err  error
 		done = make(chan struct{})
 	)
 	go func() {
-		data, err = ioutil.ReadFile(name)
+		data, err = os.ReadFile(name)
 		close(done)
 	}()
 	select {
@@ -82,7 +81,7 @@ func (d DirCache) Put(ctx context.Context, name string, data []byte) error {
 		case <-ctx.Done():
 			// Don't overwrite the file if the context was canceled.
 		default:
-			newName := filepath.Join(string(d), name)
+			newName := filepath.Join(string(d), filepath.Clean("/"+name))
 			err = os.Rename(tmp, newName)
 		}
 	}()
@@ -96,7 +95,7 @@ func (d DirCache) Put(ctx context.Context, name string, data []byte) error {

 // Delete removes the specified file name.
 func (d DirCache) Delete(ctx context.Context, name string) error {
-	name = filepath.Join(string(d), name)
+	name = filepath.Join(string(d), filepath.Clean("/"+name))
 	var (
 		err  error
 		done = make(chan struct{})
@@ -119,7 +118,7 @@ func (d DirCache) Delete(ctx context.Context, name string) error {
 // writeTempFile writes b to a temporary file, closes the file and returns its path.
 func (d DirCache) writeTempFile(prefix string, b []byte) (name string, reterr error) {
 	// TempFile uses 0600 permissions
-	f, err := ioutil.TempFile(string(d), prefix)
+	f, err := os.CreateTemp(string(d), prefix)
 	if err != nil {
 		return "", err
 	}
@@ -6,7 +6,6 @@ package autocert

 import (
 	"context"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -17,7 +16,7 @@ import (
 var _ Cache = DirCache("/")

 func TestDirCache(t *testing.T) {
-	dir, err := ioutil.TempDir("", "autocert")
+	dir, err := os.MkdirTemp("", "autocert")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -24,6 +24,7 @@ func ExampleManager() {
 	m := &autocert.Manager{
 		Cache:      autocert.DirCache("secret-dir"),
 		Prompt:     autocert.AcceptTOS,
+		Email:      "example@example.org",
 		HostPolicy: autocert.HostWhitelist("example.org", "www.example.org"),
 	}
 	s := &http.Server{
@@ -8,27 +8,30 @@
 package acmetest

 import (
+	"context"
 	"crypto"
 	"crypto/ecdsa"
 	"crypto/elliptic"
 	"crypto/rand"
+	"crypto/rsa"
 	"crypto/tls"
 	"crypto/x509"
 	"crypto/x509/pkix"
+	"encoding/asn1"
 	"encoding/base64"
 	"encoding/json"
 	"encoding/pem"
 	"fmt"
 	"io"
-	"log"
 	"math/big"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"path"
-	"sort"
 	"strconv"
 	"strings"
 	"sync"
+	"testing"
 	"time"

 	"golang.org/x/crypto/acme"
@@ -36,56 +39,65 @@ import (

 // CAServer is a simple test server which implements ACME spec bits needed for testing.
 type CAServer struct {
-	URL   string         // server URL after it has been started
-	Roots *x509.CertPool // CA root certificates; initialized in NewCAServer
-
 	rootKey      crypto.Signer
 	rootCert     []byte // DER encoding
 	rootTemplate *x509.Certificate

-	server           *httptest.Server
-	challengeTypes   []string // supported challenge types
-	domainsWhitelist []string // only these domains are valid for issuing, unless empty
+	t              *testing.T
+	server         *httptest.Server
+	issuer         pkix.Name
+	challengeTypes []string
+	url            string
+	roots          *x509.CertPool
+	eabRequired    bool

 	mu             sync.Mutex
-	certCount      int                       // number of issued certs
-	domainAddr     map[string]string         // domain name to addr:port resolution
-	authorizations map[string]*authorization // keyed by domain name
-	orders         []*order                  // index is used as order ID
-	errors         []error                   // encountered client errors
+	certCount      int                           // number of issued certs
+	acctRegistered bool                          // set once an account has been registered
+	domainAddr     map[string]string             // domain name to addr:port resolution
+	domainGetCert  map[string]getCertificateFunc // domain name to GetCertificate function
+	domainHandler  map[string]http.Handler       // domain name to Handle function
+	validAuthz     map[string]*authorization     // valid authz, keyed by domain name
+	authorizations []*authorization              // all authz, index is used as ID
+	orders         []*order                      // index is used as order ID
+	errors         []error                       // encountered client errors
 }

-// NewCAServer creates a new ACME test server and starts serving requests.
-// The returned CAServer issues certs signed with the CA roots
-// available in the Roots field.
-//
-// The challengeTypes argument defines the supported ACME challenge types
-// sent to a client in a response for a domain authorization.
-// If domainsWhitelist is non-empty, the certs will be issued only for the specified
-// list of domains. Otherwise, any domain name is allowed.
-func NewCAServer(challengeTypes []string, domainsWhitelist []string) *CAServer {
-	var whitelist []string
-	for _, name := range domainsWhitelist {
-		whitelist = append(whitelist, name)
-	}
-	sort.Strings(whitelist)
-	ca := &CAServer{
-		challengeTypes:   challengeTypes,
-		domainsWhitelist: whitelist,
-		domainAddr:       make(map[string]string),
-		authorizations:   make(map[string]*authorization),
+type getCertificateFunc func(hello *tls.ClientHelloInfo) (*tls.Certificate, error)
+
+// NewCAServer creates a new ACME test server. The returned CAServer issues
+// certs signed with the CA roots available in the Roots field.
+func NewCAServer(t *testing.T) *CAServer {
+	ca := &CAServer{t: t,
+		challengeTypes: []string{"fake-01", "tls-alpn-01", "http-01"},
+		domainAddr:     make(map[string]string),
+		domainGetCert:  make(map[string]getCertificateFunc),
+		domainHandler:  make(map[string]http.Handler),
+		validAuthz:     make(map[string]*authorization),
 	}

+	ca.server = httptest.NewUnstartedServer(http.HandlerFunc(ca.handle))
+
+	r, err := rand.Int(rand.Reader, big.NewInt(1000000))
+	if err != nil {
+		panic(fmt.Sprintf("rand.Int: %v", err))
+	}
+	ca.issuer = pkix.Name{
+		Organization: []string{"Test Acme Co"},
+		CommonName:   "Root CA " + r.String(),
+	}
+
+	return ca
+}
+
+func (ca *CAServer) generateRoot() {
 	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
 	if err != nil {
 		panic(fmt.Sprintf("ecdsa.GenerateKey: %v", err))
 	}
 	tmpl := &x509.Certificate{
-		SerialNumber: big.NewInt(1),
-		Subject: pkix.Name{
-			Organization: []string{"Test Acme Co"},
-			CommonName:   "Root CA",
-		},
+		SerialNumber:          big.NewInt(1),
+		Subject:               ca.issuer,
 		NotBefore:             time.Now(),
 		NotAfter:              time.Now().Add(365 * 24 * time.Hour),
 		KeyUsage:              x509.KeyUsageCertSign,
@@ -100,40 +112,96 @@ func NewCAServer(challengeTypes []string, domainsWhitelist []string) *CAServer {
 	if err != nil {
 		panic(fmt.Sprintf("x509.ParseCertificate: %v", err))
 	}
-	ca.Roots = x509.NewCertPool()
-	ca.Roots.AddCert(cert)
+	ca.roots = x509.NewCertPool()
+	ca.roots.AddCert(cert)
 	ca.rootKey = key
 	ca.rootCert = der
 	ca.rootTemplate = tmpl
+}

-	ca.server = httptest.NewServer(http.HandlerFunc(ca.handle))
-	ca.URL = ca.server.URL
+// IssuerName sets the name of the issuing CA.
+func (ca *CAServer) IssuerName(name pkix.Name) *CAServer {
+	if ca.url != "" {
+		panic("IssuerName must be called before Start")
+	}
+	ca.issuer = name
 	return ca
 }

-// Close shuts down the server and blocks until all outstanding
-// requests on this server have completed.
-func (ca *CAServer) Close() {
-	ca.server.Close()
+// ChallengeTypes sets the supported challenge types.
+func (ca *CAServer) ChallengeTypes(types ...string) *CAServer {
+	if ca.url != "" {
+		panic("ChallengeTypes must be called before Start")
+	}
+	ca.challengeTypes = types
+	return ca
+}
+
+// URL returns the server address, after Start has been called.
+func (ca *CAServer) URL() string {
+	if ca.url == "" {
+		panic("URL called before Start")
+	}
+	return ca.url
+}
+
+// Roots returns a pool cointaining the CA root.
+func (ca *CAServer) Roots() *x509.CertPool {
+	if ca.url == "" {
+		panic("Roots called before Start")
+	}
+	return ca.roots
+}
+
+// ExternalAccountRequired makes an EAB JWS required for account registration.
+func (ca *CAServer) ExternalAccountRequired() *CAServer {
+	if ca.url != "" {
+		panic("ExternalAccountRequired must be called before Start")
+	}
+	ca.eabRequired = true
+	return ca
+}
+
+// Start starts serving requests. The server address becomes available in the
+// URL field.
+func (ca *CAServer) Start() *CAServer {
+	if ca.url == "" {
+		ca.generateRoot()
+		ca.server.Start()
+		ca.t.Cleanup(ca.server.Close)
+		ca.url = ca.server.URL
+	}
+	return ca
 }

 func (ca *CAServer) serverURL(format string, arg ...interface{}) string {
 	return ca.server.URL + fmt.Sprintf(format, arg...)
 }

-func (ca *CAServer) addr(domain string) (string, error) {
+func (ca *CAServer) addr(domain string) (string, bool) {
 	ca.mu.Lock()
 	defer ca.mu.Unlock()
 	addr, ok := ca.domainAddr[domain]
-	if !ok {
-		return "", fmt.Errorf("CAServer: no addr resolution for %q", domain)
-	}
-	return addr, nil
+	return addr, ok
+}
+
+func (ca *CAServer) getCert(domain string) (getCertificateFunc, bool) {
+	ca.mu.Lock()
+	defer ca.mu.Unlock()
+	f, ok := ca.domainGetCert[domain]
+	return f, ok
+}
+
+func (ca *CAServer) getHandler(domain string) (http.Handler, bool) {
+	ca.mu.Lock()
+	defer ca.mu.Unlock()
+	h, ok := ca.domainHandler[domain]
+	return h, ok
 }

 func (ca *CAServer) httpErrorf(w http.ResponseWriter, code int, format string, a ...interface{}) {
 	s := fmt.Sprintf(format, a...)
-	log.Println(s)
+	ca.t.Errorf(format, a...)
 	http.Error(w, s, code)
 }

@@ -145,11 +213,33 @@ func (ca *CAServer) Resolve(domain, addr string) {
 	ca.domainAddr[domain] = addr
 }

+// ResolveGetCertificate redirects TLS connections for domain to f when
+// validating challenges for the domain authorization.
+func (ca *CAServer) ResolveGetCertificate(domain string, f getCertificateFunc) {
+	ca.mu.Lock()
+	defer ca.mu.Unlock()
+	ca.domainGetCert[domain] = f
+}
+
+// ResolveHandler redirects HTTP requests for domain to f when
+// validating challenges for the domain authorization.
+func (ca *CAServer) ResolveHandler(domain string, h http.Handler) {
+	ca.mu.Lock()
+	defer ca.mu.Unlock()
+	ca.domainHandler[domain] = h
+}
+
 type discovery struct {
-	NewNonce string `json:"newNonce"`
-	NewReg   string `json:"newAccount"`
-	NewOrder string `json:"newOrder"`
-	NewAuthz string `json:"newAuthz"`
+	NewNonce   string `json:"newNonce"`
+	NewAccount string `json:"newAccount"`
+	NewOrder   string `json:"newOrder"`
+	NewAuthz   string `json:"newAuthz"`
+
+	Meta discoveryMeta `json:"meta,omitempty"`
+}
+
+type discoveryMeta struct {
+	ExternalAccountRequired bool `json:"externalAccountRequired,omitempty"`
 }

 type challenge struct {
@@ -163,6 +253,7 @@ type authorization struct {
 	Challenges []challenge `json:"challenges"`

 	domain string
+	id     int
 }

 type order struct {
@@ -175,7 +266,7 @@ type order struct {
 }

 func (ca *CAServer) handle(w http.ResponseWriter, r *http.Request) {
-	log.Printf("%s %s", r.Method, r.URL)
+	ca.t.Logf("%s %s", r.Method, r.URL)
 	w.Header().Set("Replay-Nonce", "nonce")
 	// TODO: Verify nonce header for all POST requests.

@@ -186,10 +277,12 @@ func (ca *CAServer) handle(w http.ResponseWriter, r *http.Request) {
 	// Discovery request.
 	case r.URL.Path == "/":
 		resp := &discovery{
-			NewNonce: ca.serverURL("/new-nonce"),
-			NewReg:   ca.serverURL("/new-reg"),
-			NewOrder: ca.serverURL("/new-order"),
-			NewAuthz: ca.serverURL("/new-authz"),
+			NewNonce:   ca.serverURL("/new-nonce"),
+			NewAccount: ca.serverURL("/new-account"),
+			NewOrder:   ca.serverURL("/new-order"),
+			Meta: discoveryMeta{
+				ExternalAccountRequired: ca.eabRequired,
+			},
 		}
 		if err := json.NewEncoder(w).Encode(resp); err != nil {
 			panic(fmt.Sprintf("discovery response: %v", err))
@@ -201,7 +294,29 @@ func (ca *CAServer) handle(w http.ResponseWriter, r *http.Request) {
 		return

 	// Client key registration request.
-	case r.URL.Path == "/new-reg":
+	case r.URL.Path == "/new-account":
+		ca.mu.Lock()
+		defer ca.mu.Unlock()
+		if ca.acctRegistered {
+			ca.httpErrorf(w, http.StatusServiceUnavailable, "multiple accounts are not implemented")
+			return
+		}
+		ca.acctRegistered = true
+
+		var req struct {
+			ExternalAccountBinding json.RawMessage
+		}
+
+		if err := decodePayload(&req, r.Body); err != nil {
+			ca.httpErrorf(w, http.StatusBadRequest, err.Error())
+			return
+		}
+
+		if ca.eabRequired && len(req.ExternalAccountBinding) == 0 {
+			ca.httpErrorf(w, http.StatusBadRequest, "registration failed: no JWS for EAB")
+			return
+		}
+
 		// TODO: Check the user account key against a ca.accountKeys?
 		w.Header().Set("Location", ca.serverURL("/accounts/1"))
 		w.WriteHeader(http.StatusCreated)
@@ -221,7 +336,7 @@ func (ca *CAServer) handle(w http.ResponseWriter, r *http.Request) {
 		o := &order{Status: acme.StatusPending}
 		for _, id := range req.Identifiers {
 			z := ca.authz(id.Value)
-			o.AuthzURLs = append(o.AuthzURLs, ca.serverURL("/authz/%s", z.domain))
+			o.AuthzURLs = append(o.AuthzURLs, ca.serverURL("/authz/%d", z.id))
 		}
 		orderID := len(ca.orders)
 		ca.orders = append(ca.orders, o)
@@ -244,49 +359,50 @@ func (ca *CAServer) handle(w http.ResponseWriter, r *http.Request) {
 			panic(err)
 		}

-	// Identifier authorization request.
-	case r.URL.Path == "/new-authz":
-		var req struct {
-			Identifier struct{ Value string }
-		}
-		if err := decodePayload(&req, r.Body); err != nil {
-			ca.httpErrorf(w, http.StatusBadRequest, err.Error())
-			return
-		}
+	// Accept challenge requests.
+	case strings.HasPrefix(r.URL.Path, "/challenge/"):
+		parts := strings.Split(r.URL.Path, "/")
+		typ, id := parts[len(parts)-2], parts[len(parts)-1]
 		ca.mu.Lock()
-		defer ca.mu.Unlock()
-		z := ca.authz(req.Identifier.Value)
-		w.Header().Set("Location", ca.serverURL("/authz/%s", z.domain))
-		w.WriteHeader(http.StatusCreated)
-		if err := json.NewEncoder(w).Encode(z); err != nil {
-			panic(fmt.Sprintf("new authz response: %v", err))
+		supported := false
+		for _, suppTyp := range ca.challengeTypes {
+			if suppTyp == typ {
+				supported = true
+			}
 		}
-
-	// Accept tls-alpn-01 challenge type requests.
-	case strings.HasPrefix(r.URL.Path, "/challenge/tls-alpn-01/"):
-		domain := strings.TrimPrefix(r.URL.Path, "/challenge/tls-alpn-01/")
-		ca.mu.Lock()
-		_, exist := ca.authorizations[domain]
+		a, err := ca.storedAuthz(id)
 		ca.mu.Unlock()
-		if !exist {
-			ca.httpErrorf(w, http.StatusBadRequest, "challenge accept: no authz for %q", domain)
+		if !supported {
+			ca.httpErrorf(w, http.StatusBadRequest, "unsupported challenge: %v", typ)
 			return
 		}
-		go ca.validateChallenge("tls-alpn-01", domain)
+		if err != nil {
+			ca.httpErrorf(w, http.StatusBadRequest, "challenge accept: %v", err)
+			return
+		}
+		ca.validateChallenge(a, typ)
 		w.Write([]byte("{}"))

 	// Get authorization status requests.
 	case strings.HasPrefix(r.URL.Path, "/authz/"):
-		domain := strings.TrimPrefix(r.URL.Path, "/authz/")
+		var req struct{ Status string }
+		decodePayload(&req, r.Body)
+		deactivate := req.Status == "deactivated"
 		ca.mu.Lock()
 		defer ca.mu.Unlock()
-		authz, ok := ca.authorizations[domain]
-		if !ok {
-			ca.httpErrorf(w, http.StatusNotFound, "no authz for %q", domain)
+		authz, err := ca.storedAuthz(strings.TrimPrefix(r.URL.Path, "/authz/"))
+		if err != nil {
+			ca.httpErrorf(w, http.StatusNotFound, "%v", err)
 			return
 		}
+		if deactivate {
+			// Note we don't invalidate authorized orders as we should.
+			authz.Status = "deactivated"
+			ca.t.Logf("authz %d is now %s", authz.id, authz.Status)
+			ca.updatePendingOrders()
+		}
 		if err := json.NewEncoder(w).Encode(authz); err != nil {
-			panic(fmt.Sprintf("get authz for %q response: %v", domain, err))
+			panic(fmt.Sprintf("encoding authz %d: %v", authz.id, err))
 		}

 	// Certificate issuance request.
@@ -314,15 +430,6 @@ func (ca *CAServer) handle(w http.ResponseWriter, r *http.Request) {
 			ca.httpErrorf(w, http.StatusBadRequest, err.Error())
 			return
 		}
-		names := unique(append(csr.DNSNames, csr.Subject.CommonName))
-		if err := ca.matchWhitelist(names); err != nil {
-			ca.httpErrorf(w, http.StatusUnauthorized, err.Error())
-			return
-		}
-		if err := ca.authorized(names); err != nil {
-			ca.httpErrorf(w, http.StatusUnauthorized, err.Error())
-			return
-		}
 		// Issue the certificate.
 		der, err := ca.leafCert(csr)
 		if err != nil {
@@ -355,25 +462,6 @@ func (ca *CAServer) handle(w http.ResponseWriter, r *http.Request) {
 	}
 }

-// matchWhitelist reports whether all dnsNames are whitelisted.
-// The whitelist is provided in NewCAServer.
-func (ca *CAServer) matchWhitelist(dnsNames []string) error {
-	if len(ca.domainsWhitelist) == 0 {
-		return nil
-	}
-	var nomatch []string
-	for _, name := range dnsNames {
-		i := sort.SearchStrings(ca.domainsWhitelist, name)
-		if i == len(ca.domainsWhitelist) || ca.domainsWhitelist[i] != name {
-			nomatch = append(nomatch, name)
-		}
-	}
-	if len(nomatch) > 0 {
-		return fmt.Errorf("matchWhitelist: some domains don't match: %q", nomatch)
-	}
-	return nil
-}
-
 // storedOrder retrieves a previously created order at index i.
 // It requires ca.mu to be locked.
 func (ca *CAServer) storedOrder(i string) (*order, error) {
@@ -387,46 +475,50 @@ func (ca *CAServer) storedOrder(i string) (*order, error) {
 	if idx > len(ca.orders)-1 {
 		return nil, fmt.Errorf("storedOrder: no such order %d", idx)
 	}
+
+	ca.updatePendingOrders()
 	return ca.orders[idx], nil
 }

-// authz returns an existing authorization for the identifier or creates a new one.
+// storedAuthz retrieves a previously created authz at index i.
 // It requires ca.mu to be locked.
+func (ca *CAServer) storedAuthz(i string) (*authorization, error) {
+	idx, err := strconv.Atoi(i)
+	if err != nil {
+		return nil, fmt.Errorf("storedAuthz: %v", err)
+	}
+	if idx < 0 {
+		return nil, fmt.Errorf("storedAuthz: invalid authz index %d", idx)
+	}
+	if idx > len(ca.authorizations)-1 {
+		return nil, fmt.Errorf("storedAuthz: no such authz %d", idx)
+	}
+	return ca.authorizations[idx], nil
+}
+
+// authz returns an existing valid authorization for the identifier or creates a
+// new one. It requires ca.mu to be locked.
 func (ca *CAServer) authz(identifier string) *authorization {
-	authz, ok := ca.authorizations[identifier]
+	authz, ok := ca.validAuthz[identifier]
 	if !ok {
+		authzId := len(ca.authorizations)
 		authz = &authorization{
+			id:     authzId,
 			domain: identifier,
 			Status: acme.StatusPending,
 		}
 		for _, typ := range ca.challengeTypes {
 			authz.Challenges = append(authz.Challenges, challenge{
 				Type:  typ,
-				URI:   ca.serverURL("/challenge/%s/%s", typ, authz.domain),
-				Token: challengeToken(authz.domain, typ),
+				URI:   ca.serverURL("/challenge/%s/%d", typ, authzId),
+				Token: challengeToken(authz.domain, typ, authzId),
 			})
 		}
-		ca.authorizations[authz.domain] = authz
+		ca.authorizations = append(ca.authorizations, authz)
 	}
 	return authz
 }

-// authorized reports whether all authorizations for dnsNames have been satisfied.
-// It requires ca.mu to be locked.
-func (ca *CAServer) authorized(dnsNames []string) error {
-	var noauthz []string
-	for _, name := range dnsNames {
-		authz, ok := ca.authorizations[name]
-		if !ok || authz.Status != acme.StatusValid {
-			noauthz = append(noauthz, name)
-		}
-	}
-	if len(noauthz) > 0 {
-		return fmt.Errorf("CAServer: no authz for %q", noauthz)
-	}
-	return nil
-}
-
 // leafCert issues a new certificate.
 // It requires ca.mu to be locked.
 func (ca *CAServer) leafCert(csr *x509.CertificateRequest) (der []byte, err error) {
@@ -447,79 +539,231 @@ func (ca *CAServer) leafCert(csr *x509.CertificateRequest) (der []byte, err erro
 	return x509.CreateCertificate(rand.Reader, leaf, ca.rootTemplate, csr.PublicKey, ca.rootKey)
 }

-// TODO: Only tls-alpn-01 is currently supported: implement http-01 and dns-01.
-func (ca *CAServer) validateChallenge(typ, identifier string) {
+// LeafCert issues a leaf certificate.
+func (ca *CAServer) LeafCert(name, keyType string, notBefore, notAfter time.Time) *tls.Certificate {
+	if ca.url == "" {
+		panic("LeafCert called before Start")
+	}
+
+	ca.mu.Lock()
+	defer ca.mu.Unlock()
+	var pk crypto.Signer
+	switch keyType {
+	case "RSA":
+		var err error
+		pk, err = rsa.GenerateKey(rand.Reader, 1024)
+		if err != nil {
+			ca.t.Fatal(err)
+		}
+	case "ECDSA":
+		var err error
+		pk, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+		if err != nil {
+			ca.t.Fatal(err)
+		}
+	default:
+		panic("LeafCert: unknown key type")
+	}
+	ca.certCount++ // next leaf cert serial number
+	leaf := &x509.Certificate{
+		SerialNumber:          big.NewInt(int64(ca.certCount)),
+		Subject:               pkix.Name{Organization: []string{"Test Acme Co"}},
+		NotBefore:             notBefore,
+		NotAfter:              notAfter,
+		KeyUsage:              x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		DNSNames:              []string{name},
+		BasicConstraintsValid: true,
+	}
+	der, err := x509.CreateCertificate(rand.Reader, leaf, ca.rootTemplate, pk.Public(), ca.rootKey)
+	if err != nil {
+		ca.t.Fatal(err)
+	}
+	return &tls.Certificate{
+		Certificate: [][]byte{der},
+		PrivateKey:  pk,
+	}
+}
+
+func (ca *CAServer) validateChallenge(authz *authorization, typ string) {
 	var err error
 	switch typ {
 	case "tls-alpn-01":
-		err = ca.verifyALPNChallenge(identifier)
+		err = ca.verifyALPNChallenge(authz)
+	case "http-01":
+		err = ca.verifyHTTPChallenge(authz)
 	default:
 		panic(fmt.Sprintf("validation of %q is not implemented", typ))
 	}
 	ca.mu.Lock()
 	defer ca.mu.Unlock()
-	authz := ca.authorizations[identifier]
 	if err != nil {
 		authz.Status = "invalid"
 	} else {
 		authz.Status = "valid"
+		ca.validAuthz[authz.domain] = authz
 	}
-	log.Printf("validated %q for %q; authz status is now: %s", typ, identifier, authz.Status)
+	ca.t.Logf("validated %q for %q, err: %v", typ, authz.domain, err)
+	ca.t.Logf("authz %d is now %s", authz.id, authz.Status)
+
+	ca.updatePendingOrders()
+}
+
+func (ca *CAServer) updatePendingOrders() {
 	// Update all pending orders.
 	// An order becomes "ready" if all authorizations are "valid".
 	// An order becomes "invalid" if any authorization is "invalid".
 	// Status changes: https://tools.ietf.org/html/rfc8555#section-7.1.6
-OrdersLoop:
 	for i, o := range ca.orders {
 		if o.Status != acme.StatusPending {
 			continue
 		}
-		var countValid int
-		for _, zurl := range o.AuthzURLs {
-			z, ok := ca.authorizations[path.Base(zurl)]
-			if !ok {
-				log.Printf("no authz %q for order %d", zurl, i)
-				continue OrdersLoop
-			}
-			if z.Status == acme.StatusInvalid {
-				o.Status = acme.StatusInvalid
-				log.Printf("order %d is now invalid", i)
-				continue OrdersLoop
-			}
-			if z.Status == acme.StatusValid {
-				countValid++
-			}
+
+		countValid, countInvalid := ca.validateAuthzURLs(o.AuthzURLs, i)
+		if countInvalid > 0 {
+			o.Status = acme.StatusInvalid
+			ca.t.Logf("order %d is now invalid", i)
+			continue
 		}
 		if countValid == len(o.AuthzURLs) {
 			o.Status = acme.StatusReady
 			o.FinalizeURL = ca.serverURL("/new-cert/%d", i)
-			log.Printf("order %d is now ready", i)
+			ca.t.Logf("order %d is now ready", i)
 		}
 	}
 }

-func (ca *CAServer) verifyALPNChallenge(domain string) error {
+func (ca *CAServer) validateAuthzURLs(urls []string, orderNum int) (countValid, countInvalid int) {
+	for _, zurl := range urls {
+		z, err := ca.storedAuthz(path.Base(zurl))
+		if err != nil {
+			ca.t.Logf("no authz %q for order %d", zurl, orderNum)
+			continue
+		}
+		if z.Status == acme.StatusInvalid {
+			countInvalid++
+		}
+		if z.Status == acme.StatusValid {
+			countValid++
+		}
+	}
+	return countValid, countInvalid
+}
+
+func (ca *CAServer) verifyALPNChallenge(a *authorization) error {
 	const acmeALPNProto = "acme-tls/1"

-	addr, err := ca.addr(domain)
-	if err != nil {
-		return err
+	addr, haveAddr := ca.addr(a.domain)
+	getCert, haveGetCert := ca.getCert(a.domain)
+	if !haveAddr && !haveGetCert {
+		return fmt.Errorf("no resolution information for %q", a.domain)
 	}
-	conn, err := tls.Dial("tcp", addr, &tls.Config{
-		ServerName:         domain,
-		InsecureSkipVerify: true,
-		NextProtos:         []string{acmeALPNProto},
-	})
-	if err != nil {
-		return err
+	if haveAddr && haveGetCert {
+		return fmt.Errorf("overlapping resolution information for %q", a.domain)
 	}
-	if v := conn.ConnectionState().NegotiatedProtocol; v != acmeALPNProto {
-		return fmt.Errorf("CAServer: verifyALPNChallenge: negotiated proto is %q; want %q", v, acmeALPNProto)
+
+	var crt *x509.Certificate
+	switch {
+	case haveAddr:
+		conn, err := tls.Dial("tcp", addr, &tls.Config{
+			ServerName:         a.domain,
+			InsecureSkipVerify: true,
+			NextProtos:         []string{acmeALPNProto},
+			MinVersion:         tls.VersionTLS12,
+		})
+		if err != nil {
+			return err
+		}
+		if v := conn.ConnectionState().NegotiatedProtocol; v != acmeALPNProto {
+			return fmt.Errorf("CAServer: verifyALPNChallenge: negotiated proto is %q; want %q", v, acmeALPNProto)
+		}
+		if n := len(conn.ConnectionState().PeerCertificates); n != 1 {
+			return fmt.Errorf("len(PeerCertificates) = %d; want 1", n)
+		}
+		crt = conn.ConnectionState().PeerCertificates[0]
+	case haveGetCert:
+		hello := &tls.ClientHelloInfo{
+			ServerName: a.domain,
+			// TODO: support selecting ECDSA.
+			CipherSuites:      []uint16{tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305},
+			SupportedProtos:   []string{acme.ALPNProto},
+			SupportedVersions: []uint16{tls.VersionTLS12},
+		}
+		c, err := getCert(hello)
+		if err != nil {
+			return err
+		}
+		crt, err = x509.ParseCertificate(c.Certificate[0])
+		if err != nil {
+			return err
+		}
 	}
-	if n := len(conn.ConnectionState().PeerCertificates); n != 1 {
-		return fmt.Errorf("len(PeerCertificates) = %d; want 1", n)
+
+	if err := crt.VerifyHostname(a.domain); err != nil {
+		return fmt.Errorf("verifyALPNChallenge: VerifyHostname: %v", err)
+	}
+	// See RFC 8737, Section 6.1.
+	oid := asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 1, 31}
+	for _, x := range crt.Extensions {
+		if x.Id.Equal(oid) {
+			// TODO: check the token.
+			return nil
+		}
+	}
+	return fmt.Errorf("verifyTokenCert: no id-pe-acmeIdentifier extension found")
+}
+
+func (ca *CAServer) verifyHTTPChallenge(a *authorization) error {
+	addr, haveAddr := ca.addr(a.domain)
+	handler, haveHandler := ca.getHandler(a.domain)
+	if !haveAddr && !haveHandler {
+		return fmt.Errorf("no resolution information for %q", a.domain)
+	}
+	if haveAddr && haveHandler {
+		return fmt.Errorf("overlapping resolution information for %q", a.domain)
+	}
+
+	token := challengeToken(a.domain, "http-01", a.id)
+	path := "/.well-known/acme-challenge/" + token
+
+	var body string
+	switch {
+	case haveAddr:
+		t := &http.Transport{
+			DialContext: func(ctx context.Context, network, _ string) (net.Conn, error) {
+				return (&net.Dialer{}).DialContext(ctx, network, addr)
+			},
+		}
+		req, err := http.NewRequest("GET", "http://"+a.domain+path, nil)
+		if err != nil {
+			return err
+		}
+		res, err := t.RoundTrip(req)
+		if err != nil {
+			return err
+		}
+		if res.StatusCode != http.StatusOK {
+			return fmt.Errorf("http token: w.Code = %d; want %d", res.StatusCode, http.StatusOK)
+		}
+		b, err := io.ReadAll(res.Body)
+		if err != nil {
+			return err
+		}
+		body = string(b)
+	case haveHandler:
+		r := httptest.NewRequest("GET", path, nil)
+		r.Host = a.domain
+		w := httptest.NewRecorder()
+		handler.ServeHTTP(w, r)
+		if w.Code != http.StatusOK {
+			return fmt.Errorf("http token: w.Code = %d; want %d", w.Code, http.StatusOK)
+		}
+		body = w.Body.String()
+	}
+
+	if !strings.HasPrefix(body, token) {
+		return fmt.Errorf("http token value = %q; want 'token-http-01.' prefix", body)
 	}
-	// TODO: verify conn.ConnectionState().PeerCertificates[0]
 	return nil
 }

@@ -535,8 +779,8 @@ func decodePayload(v interface{}, r io.Reader) error {
 	return json.Unmarshal(payload, v)
 }

-func challengeToken(domain, challType string) string {
-	return fmt.Sprintf("token-%s-%s", domain, challType)
+func challengeToken(domain, challType string, authzID int) string {
+	return fmt.Sprintf("token-%s-%s-%d", domain, challType, authzID)
 }

 func unique(a []string) []string {
@@ -20,7 +20,7 @@ import (
 //
 // It enables one-line HTTPS servers:
 //
-//     log.Fatal(http.Serve(autocert.NewListener("example.com"), handler))
+//	log.Fatal(http.Serve(autocert.NewListener("example.com"), handler))
 //
 // NewListener is a convenience function for a common configuration.
 // More complex or custom configurations can use the autocert.Manager
@@ -21,8 +21,9 @@ type domainRenewal struct {
 	ck  certKey
 	key crypto.Signer

-	timerMu sync.Mutex
-	timer   *time.Timer
+	timerMu    sync.Mutex
+	timer      *time.Timer
+	timerClose chan struct{} // if non-nil, renew closes this channel (and nils out the timer fields) instead of running
 }

 // start starts a cert renewal timer at the time
@@ -38,16 +39,28 @@ func (dr *domainRenewal) start(exp time.Time) {
 	dr.timer = time.AfterFunc(dr.next(exp), dr.renew)
 }

-// stop stops the cert renewal timer.
-// If the timer is already stopped, calling stop is a noop.
+// stop stops the cert renewal timer and waits for any in-flight calls to renew
+// to complete. If the timer is already stopped, calling stop is a noop.
 func (dr *domainRenewal) stop() {
 	dr.timerMu.Lock()
 	defer dr.timerMu.Unlock()
-	if dr.timer == nil {
-		return
+	for {
+		if dr.timer == nil {
+			return
+		}
+		if dr.timer.Stop() {
+			dr.timer = nil
+			return
+		} else {
+			// dr.timer fired, and we acquired dr.timerMu before the renew callback did.
+			// (We know this because otherwise the renew callback would have reset dr.timer!)
+			timerClose := make(chan struct{})
+			dr.timerClose = timerClose
+			dr.timerMu.Unlock()
+			<-timerClose
+			dr.timerMu.Lock()
+		}
 	}
-	dr.timer.Stop()
-	dr.timer = nil
 }

 // renew is called periodically by a timer.
@@ -55,7 +68,9 @@ func (dr *domainRenewal) stop() {
 func (dr *domainRenewal) renew() {
 	dr.timerMu.Lock()
 	defer dr.timerMu.Unlock()
-	if dr.timer == nil {
+	if dr.timerClose != nil {
+		close(dr.timerClose)
+		dr.timer, dr.timerClose = nil, nil
 		return
 	}

@@ -67,8 +82,8 @@ func (dr *domainRenewal) renew() {
 		next = renewJitter / 2
 		next += time.Duration(pseudoRand.int63n(int64(next)))
 	}
-	dr.timer = time.AfterFunc(next, dr.renew)
 	testDidRenewLoop(next, err)
+	dr.timer = time.AfterFunc(next, dr.renew)
 }

 // updateState locks and replaces the relevant Manager.state item with the given
@@ -6,19 +6,13 @@ package autocert

 import (
 	"context"
+	"crypto"
 	"crypto/ecdsa"
-	"crypto/elliptic"
-	"crypto/rand"
-	"crypto/tls"
-	"crypto/x509"
-	"encoding/base64"
-	"fmt"
-	"net/http"
-	"net/http/httptest"
 	"testing"
 	"time"

 	"golang.org/x/crypto/acme"
+	"golang.org/x/crypto/acme/autocert/internal/acmetest"
 )

 func TestRenewalNext(t *testing.T) {
@@ -48,101 +42,47 @@ func TestRenewalNext(t *testing.T) {
 }

 func TestRenewFromCache(t *testing.T) {
-	// ACME CA server stub
-	var ca *httptest.Server
-	ca = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		w.Header().Set("Replay-Nonce", "nonce")
-		if r.Method == "HEAD" {
-			// a nonce request
-			return
-		}
+	man := testManager(t)
+	man.RenewBefore = 24 * time.Hour

-		switch r.URL.Path {
-		// discovery
-		case "/":
-			if err := discoTmpl.Execute(w, ca.URL); err != nil {
-				t.Fatalf("discoTmpl: %v", err)
-			}
-		// client key registration
-		case "/new-reg":
-			w.Write([]byte("{}"))
-		// domain authorization
-		case "/new-authz":
-			w.Header().Set("Location", ca.URL+"/authz/1")
-			w.WriteHeader(http.StatusCreated)
-			w.Write([]byte(`{"status": "valid"}`))
-		// authorization status request done by Manager's revokePendingAuthz.
-		case "/authz/1":
-			w.Write([]byte(`{"status": "valid"}`))
-		// cert request
-		case "/new-cert":
-			var req struct {
-				CSR string `json:"csr"`
-			}
-			decodePayload(&req, r.Body)
-			b, _ := base64.RawURLEncoding.DecodeString(req.CSR)
-			csr, err := x509.ParseCertificateRequest(b)
-			if err != nil {
-				t.Fatalf("new-cert: CSR: %v", err)
-			}
-			der, err := dummyCert(csr.PublicKey, exampleDomain)
-			if err != nil {
-				t.Fatalf("new-cert: dummyCert: %v", err)
-			}
-			chainUp := fmt.Sprintf("<%s/ca-cert>; rel=up", ca.URL)
-			w.Header().Set("Link", chainUp)
-			w.WriteHeader(http.StatusCreated)
-			w.Write(der)
-		// CA chain cert
-		case "/ca-cert":
-			der, err := dummyCert(nil, "ca")
-			if err != nil {
-				t.Fatalf("ca-cert: dummyCert: %v", err)
-			}
-			w.Write(der)
-		default:
-			t.Errorf("unrecognized r.URL.Path: %s", r.URL.Path)
-		}
-	}))
-	defer ca.Close()
+	ca := acmetest.NewCAServer(t).Start()
+	ca.ResolveGetCertificate(exampleDomain, man.GetCertificate)

-	man := &Manager{
-		Prompt:      AcceptTOS,
-		Cache:       newMemCache(t),
-		RenewBefore: 24 * time.Hour,
-		Client: &acme.Client{
-			DirectoryURL: ca.URL,
-		},
+	man.Client = &acme.Client{
+		DirectoryURL: ca.URL(),
 	}
-	defer man.stopRenew()

 	// cache an almost expired cert
-	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
-	if err != nil {
-		t.Fatal(err)
-	}
 	now := time.Now()
-	cert, err := dateDummyCert(key.Public(), now.Add(-2*time.Hour), now.Add(time.Minute), exampleDomain)
-	if err != nil {
-		t.Fatal(err)
-	}
-	tlscert := &tls.Certificate{PrivateKey: key, Certificate: [][]byte{cert}}
-	if err := man.cachePut(context.Background(), exampleCertKey, tlscert); err != nil {
+	c := ca.LeafCert(exampleDomain, "ECDSA", now.Add(-2*time.Hour), now.Add(time.Minute))
+	if err := man.cachePut(context.Background(), exampleCertKey, c); err != nil {
 		t.Fatal(err)
 	}

-	// veriy the renewal happened
+	// verify the renewal happened
 	defer func() {
+		// Stop the timers that read and execute testDidRenewLoop before restoring it.
+		// Otherwise the timer callback may race with the deferred write.
+		man.stopRenew()
 		testDidRenewLoop = func(next time.Duration, err error) {}
 	}()
-	done := make(chan struct{})
+	renewed := make(chan bool, 1)
 	testDidRenewLoop = func(next time.Duration, err error) {
-		defer close(done)
+		defer func() {
+			select {
+			case renewed <- true:
+			default:
+				// The renewal timer uses a random backoff. If the first renewal fails for
+				// some reason, we could end up with multiple calls here before the test
+				// stops the timer.
+			}
+		}()
+
 		if err != nil {
 			t.Errorf("testDidRenewLoop: %v", err)
 		}
 		// Next should be about 90 days:
-		// dummyCert creates 90days expiry + account for man.RenewBefore.
+		// CaServer creates 90days expiry + account for man.RenewBefore.
 		// Previous expiration was within 1 min.
 		future := 88 * 24 * time.Hour
 		if next < future {
@@ -153,7 +93,8 @@ func TestRenewFromCache(t *testing.T) {
 		after := time.Now().Add(future)
 		tlscert, err := man.cacheGet(context.Background(), exampleCertKey)
 		if err != nil {
-			t.Fatalf("man.cacheGet: %v", err)
+			t.Errorf("man.cacheGet: %v", err)
+			return
 		}
 		if !tlscert.Leaf.NotAfter.After(after) {
 			t.Errorf("cache leaf.NotAfter = %v; want > %v", tlscert.Leaf.NotAfter, after)
@@ -164,11 +105,13 @@ func TestRenewFromCache(t *testing.T) {
 		defer man.stateMu.Unlock()
 		s := man.state[exampleCertKey]
 		if s == nil {
-			t.Fatalf("m.state[%q] is nil", exampleCertKey)
+			t.Errorf("m.state[%q] is nil", exampleCertKey)
+			return
 		}
 		tlscert, err = s.tlscert()
 		if err != nil {
-			t.Fatalf("s.tlscert: %v", err)
+			t.Errorf("s.tlscert: %v", err)
+			return
 		}
 		if !tlscert.Leaf.NotAfter.After(after) {
 			t.Errorf("state leaf.NotAfter = %v; want > %v", tlscert.Leaf.NotAfter, after)
@@ -180,55 +123,34 @@ func TestRenewFromCache(t *testing.T) {
 	if _, err := man.GetCertificate(hello); err != nil {
 		t.Fatal(err)
 	}
-
-	// wait for renew loop
-	select {
-	case <-time.After(10 * time.Second):
-		t.Fatal("renew took too long to occur")
-	case <-done:
-	}
+	<-renewed
 }

 func TestRenewFromCacheAlreadyRenewed(t *testing.T) {
-	man := &Manager{
-		Prompt:      AcceptTOS,
-		Cache:       newMemCache(t),
-		RenewBefore: 24 * time.Hour,
-		Client: &acme.Client{
-			DirectoryURL: "invalid",
-		},
+	ca := acmetest.NewCAServer(t).Start()
+	man := testManager(t)
+	man.RenewBefore = 24 * time.Hour
+	man.Client = &acme.Client{
+		DirectoryURL: "invalid",
 	}
-	defer man.stopRenew()

 	// cache a recently renewed cert with a different private key
-	newKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
-	if err != nil {
-		t.Fatal(err)
-	}
 	now := time.Now()
-	newCert, err := dateDummyCert(newKey.Public(), now.Add(-2*time.Hour), now.Add(time.Hour*24*90), exampleDomain)
-	if err != nil {
+	newCert := ca.LeafCert(exampleDomain, "ECDSA", now.Add(-2*time.Hour), now.Add(time.Hour*24*90))
+	if err := man.cachePut(context.Background(), exampleCertKey, newCert); err != nil {
 		t.Fatal(err)
 	}
-	newLeaf, err := validCert(exampleCertKey, [][]byte{newCert}, newKey, now)
+	newLeaf, err := validCert(exampleCertKey, newCert.Certificate, newCert.PrivateKey.(crypto.Signer), now)
 	if err != nil {
 		t.Fatal(err)
 	}
-	newTLSCert := &tls.Certificate{PrivateKey: newKey, Certificate: [][]byte{newCert}, Leaf: newLeaf}
-	if err := man.cachePut(context.Background(), exampleCertKey, newTLSCert); err != nil {
-		t.Fatal(err)
-	}

 	// set internal state to an almost expired cert
-	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	oldCert := ca.LeafCert(exampleDomain, "ECDSA", now.Add(-2*time.Hour), now.Add(time.Minute))
 	if err != nil {
 		t.Fatal(err)
 	}
-	oldCert, err := dateDummyCert(key.Public(), now.Add(-2*time.Hour), now.Add(time.Minute), exampleDomain)
-	if err != nil {
-		t.Fatal(err)
-	}
-	oldLeaf, err := validCert(exampleCertKey, [][]byte{oldCert}, key, now)
+	oldLeaf, err := validCert(exampleCertKey, oldCert.Certificate, oldCert.PrivateKey.(crypto.Signer), now)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -237,20 +159,32 @@ func TestRenewFromCacheAlreadyRenewed(t *testing.T) {
 		man.state = make(map[certKey]*certState)
 	}
 	s := &certState{
-		key:  key,
-		cert: [][]byte{oldCert},
+		key:  oldCert.PrivateKey.(crypto.Signer),
+		cert: oldCert.Certificate,
 		leaf: oldLeaf,
 	}
 	man.state[exampleCertKey] = s
 	man.stateMu.Unlock()

-	// veriy the renewal accepted the newer cached cert
+	// verify the renewal accepted the newer cached cert
 	defer func() {
+		// Stop the timers that read and execute testDidRenewLoop before restoring it.
+		// Otherwise the timer callback may race with the deferred write.
+		man.stopRenew()
 		testDidRenewLoop = func(next time.Duration, err error) {}
 	}()
-	done := make(chan struct{})
+	renewed := make(chan bool, 1)
 	testDidRenewLoop = func(next time.Duration, err error) {
-		defer close(done)
+		defer func() {
+			select {
+			case renewed <- true:
+			default:
+				// The renewal timer uses a random backoff. If the first renewal fails for
+				// some reason, we could end up with multiple calls here before the test
+				// stops the timer.
+			}
+		}()
+
 		if err != nil {
 			t.Errorf("testDidRenewLoop: %v", err)
 		}
@@ -264,7 +198,8 @@ func TestRenewFromCacheAlreadyRenewed(t *testing.T) {
 		// ensure the cached cert was not modified
 		tlscert, err := man.cacheGet(context.Background(), exampleCertKey)
 		if err != nil {
-			t.Fatalf("man.cacheGet: %v", err)
+			t.Errorf("man.cacheGet: %v", err)
+			return
 		}
 		if !tlscert.Leaf.NotAfter.Equal(newLeaf.NotAfter) {
 			t.Errorf("cache leaf.NotAfter = %v; want == %v", tlscert.Leaf.NotAfter, newLeaf.NotAfter)
@@ -275,30 +210,22 @@ func TestRenewFromCacheAlreadyRenewed(t *testing.T) {
 		defer man.stateMu.Unlock()
 		s := man.state[exampleCertKey]
 		if s == nil {
-			t.Fatalf("m.state[%q] is nil", exampleCertKey)
+			t.Errorf("m.state[%q] is nil", exampleCertKey)
+			return
 		}
 		stateKey := s.key.Public().(*ecdsa.PublicKey)
-		if stateKey.X.Cmp(newKey.X) != 0 || stateKey.Y.Cmp(newKey.Y) != 0 {
-			t.Fatalf("state key was not updated from cache x: %v y: %v; want x: %v y: %v", stateKey.X, stateKey.Y, newKey.X, newKey.Y)
+		if !stateKey.Equal(newLeaf.PublicKey) {
+			t.Error("state key was not updated from cache")
+			return
 		}
 		tlscert, err = s.tlscert()
 		if err != nil {
-			t.Fatalf("s.tlscert: %v", err)
+			t.Errorf("s.tlscert: %v", err)
+			return
 		}
 		if !tlscert.Leaf.NotAfter.Equal(newLeaf.NotAfter) {
 			t.Errorf("state leaf.NotAfter = %v; want == %v", tlscert.Leaf.NotAfter, newLeaf.NotAfter)
 		}
-
-		// verify the private key is replaced in the renewal state
-		r := man.renewal[exampleCertKey]
-		if r == nil {
-			t.Fatalf("m.renewal[%q] is nil", exampleCertKey)
-		}
-		renewalKey := r.key.Public().(*ecdsa.PublicKey)
-		if renewalKey.X.Cmp(newKey.X) != 0 || renewalKey.Y.Cmp(newKey.Y) != 0 {
-			t.Fatalf("renewal private key was not updated from cache x: %v y: %v; want x: %v y: %v", renewalKey.X, renewalKey.Y, newKey.X, newKey.Y)
-		}
-
 	}

 	// assert the expiring cert is returned from state
@@ -312,21 +239,31 @@ func TestRenewFromCacheAlreadyRenewed(t *testing.T) {
 	}

 	// trigger renew
-	go man.renew(exampleCertKey, s.key, s.leaf.NotAfter)
+	man.startRenew(exampleCertKey, s.key, s.leaf.NotAfter)
+	<-renewed
+	func() {
+		man.renewalMu.Lock()
+		defer man.renewalMu.Unlock()

-	// wait for renew loop
-	select {
-	case <-time.After(10 * time.Second):
-		t.Fatal("renew took too long to occur")
-	case <-done:
-		// assert the new cert is returned from state after renew
-		hello := clientHelloInfo(exampleDomain, algECDSA)
-		tlscert, err := man.GetCertificate(hello)
-		if err != nil {
-			t.Fatal(err)
+		// verify the private key is replaced in the renewal state
+		r := man.renewal[exampleCertKey]
+		if r == nil {
+			t.Errorf("m.renewal[%q] is nil", exampleCertKey)
+			return
 		}
-		if !newTLSCert.Leaf.NotAfter.Equal(tlscert.Leaf.NotAfter) {
-			t.Errorf("state leaf.NotAfter = %v; want == %v", tlscert.Leaf.NotAfter, newTLSCert.Leaf.NotAfter)
+		renewalKey := r.key.Public().(*ecdsa.PublicKey)
+		if !renewalKey.Equal(newLeaf.PublicKey) {
+			t.Error("renewal private key was not updated from cache")
 		}
+	}()
+
+	// assert the new cert is returned from state after renew
+	hello = clientHelloInfo(exampleDomain, algECDSA)
+	tlscert, err = man.GetCertificate(hello)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !newLeaf.NotAfter.Equal(tlscert.Leaf.NotAfter) {
+		t.Errorf("state leaf.NotAfter = %v; want == %v", tlscert.Leaf.NotAfter, newLeaf.NotAfter)
 	}
 }
@@ -10,10 +10,12 @@ import (
 	"crypto"
 	"crypto/rand"
 	"encoding/json"
+	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"math/big"
 	"net/http"
+	"runtime/debug"
 	"strconv"
 	"strings"
 	"time"
@@ -155,7 +157,7 @@ func (c *Client) get(ctx context.Context, url string, ok resOkay) (*http.Respons
 	}
 }

-// postAsGet is POST-as-GET, a replacement for GET in RFC8555
+// postAsGet is POST-as-GET, a replacement for GET in RFC 8555
 // as described in https://tools.ietf.org/html/rfc8555#section-6.3.
 // It makes a POST request in KID form with zero JWS payload.
 // See nopayload doc comments in jws.go.
@@ -215,6 +217,9 @@ func (c *Client) post(ctx context.Context, key crypto.Signer, url string, body i
 func (c *Client) postNoRetry(ctx context.Context, key crypto.Signer, url string, body interface{}) (*http.Response, *http.Request, error) {
 	kid := noKeyID
 	if key == nil {
+		if c.Key == nil {
+			return nil, nil, errors.New("acme: Client.Key must be populated to make POST requests")
+		}
 		key = c.Key
 		kid = c.accountKID(ctx)
 	}
@@ -267,9 +272,27 @@ func (c *Client) httpClient() *http.Client {
 }

 // packageVersion is the version of the module that contains this package, for
-// sending as part of the User-Agent header. It's set in version_go112.go.
+// sending as part of the User-Agent header.
 var packageVersion string

+func init() {
+	// Set packageVersion if the binary was built in modules mode and x/crypto
+	// was not replaced with a different module.
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return
+	}
+	for _, m := range info.Deps {
+		if m.Path != "golang.org/x/crypto" {
+			continue
+		}
+		if m.Replace == nil {
+			packageVersion = m.Version
+		}
+		break
+	}
+}
+
 // userAgent returns the User-Agent header value. It includes the package name,
 // the module version (if available), and the c.UserAgent value (if set).
 func (c *Client) userAgent() string {
@@ -306,7 +329,7 @@ func isRetriable(code int) bool {
 func responseError(resp *http.Response) error {
 	// don't care if ReadAll returns an error:
 	// json.Unmarshal will fail in that case anyway
-	b, _ := ioutil.ReadAll(resp.Body)
+	b, _ := io.ReadAll(resp.Body)
 	e := &wireError{Status: resp.StatusCode}
 	if err := json.Unmarshal(b, e); err != nil {
 		// this is not a regular error response:
@@ -7,7 +7,7 @@ package acme
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"reflect"
@@ -54,7 +54,7 @@ func TestErrorResponse(t *testing.T) {
 	res := &http.Response{
 		StatusCode: 400,
 		Status:     "400 Bad Request",
-		Body:       ioutil.NopCloser(strings.NewReader(s)),
+		Body:       io.NopCloser(strings.NewReader(s)),
 		Header:     http.Header{"X-Foo": {"bar"}},
 	}
 	err := responseError(res)
@@ -115,8 +115,8 @@ func TestPostWithRetries(t *testing.T) {
 	if _, err := client.Authorize(context.Background(), "example.com"); err != nil {
 		t.Errorf("client.Authorize 1: %v", err)
 	}
-	if count != 4 {
-		t.Errorf("total requests count: %d; want 4", count)
+	if count != 3 {
+		t.Errorf("total requests count: %d; want 3", count)
 	}
 }

@@ -224,7 +224,7 @@ func TestUserAgent(t *testing.T) {
 			}

 			w.WriteHeader(http.StatusOK)
-			w.Write([]byte(`{}`))
+			w.Write([]byte(`{"newOrder": "sure"}`))
 		}))
 		defer ts.Close()

@@ -238,3 +238,18 @@ func TestUserAgent(t *testing.T) {
 		}
 	}
 }
+
+func TestAccountKidLoop(t *testing.T) {
+	// if Client.postNoRetry is called with a nil key argument
+	// then Client.Key must be set, otherwise we fall into an
+	// infinite loop (which also causes a deadlock).
+	client := &Client{dir: &Directory{OrderURL: ":)"}}
+	_, _, err := client.postNoRetry(context.Background(), nil, "", nil)
+	if err == nil {
+		t.Fatal("Client.postNoRetry didn't fail with a nil key")
+	}
+	expected := "acme: Client.Key must be populated to make POST requests"
+	if err.Error() != expected {
+		t.Fatalf("Unexpected error returned: wanted %q, got %q", expected, err.Error())
+	}
+}
@@ -11,12 +11,12 @@
 //
 // A usage example:
 //
-//     go run prober.go \
-//       -d https://acme-staging-v02.api.letsencrypt.org/directory \
-//       -f order \
-//       -t http-01 \
-//       -a :8080 \
-//       -domain some.example.org
+//	go run prober.go \
+//	  -d https://acme-staging-v02.api.letsencrypt.org/directory \
+//	  -f order \
+//	  -t http-01 \
+//	  -a :8080 \
+//	  -domain some.example.org
 //
 // The above assumes a TCP tunnel from some.example.org:80 to 0.0.0.0:8080
 // in order for the test to be able to fulfill http-01 challenge.
@@ -50,14 +50,13 @@ import (

 var (
 	// ACME CA directory URL.
-	// Let's Encrypt v1 prod: https://acme-v01.api.letsencrypt.org/directory
 	// Let's Encrypt v2 prod: https://acme-v02.api.letsencrypt.org/directory
 	// Let's Encrypt v2 staging: https://acme-staging-v02.api.letsencrypt.org/directory
 	// See the following for more CAs implementing ACME protocol:
 	// https://en.wikipedia.org/wiki/Automated_Certificate_Management_Environment#CAs_&_PKIs_that_offer_ACME_certificates
 	directory = flag.String("d", "", "ACME directory URL.")
 	reginfo   = flag.String("r", "", "ACME account registration info.")
-	flow      = flag.String("f", "", "Flow to run: order, preauthz (RFC8555) or preauthz02 (draft-02).")
+	flow      = flag.String("f", "", `Flow to run: "order" or "preauthz" (RFC8555).`)
 	chaltyp   = flag.String("t", "", "Challenge type: tls-alpn-01, http-01 or dns-01.")
 	addr      = flag.String("a", "", "Local server address for tls-alpn-01 and http-01.")
 	dnsscript = flag.String("s", "", "Script to run for provisioning dns-01 challenges.")
@@ -127,8 +126,6 @@ When running with dns-01 challenge type, use -s argument instead of -a.
 		p.runOrder(ctx, identifiers)
 	case "preauthz":
 		p.runPreauthz(ctx, identifiers)
-	case "preauthz02":
-		p.runPreauthzLegacy(ctx, identifiers)
 	default:
 		log.Fatalf("unknown flow: %q", *flow)
 	}
@@ -276,50 +273,6 @@ func (p *prober) runPreauthz(ctx context.Context, identifiers []acme.AuthzID) {
 	}
 }

-func (p *prober) runPreauthzLegacy(ctx context.Context, identifiers []acme.AuthzID) {
-	var zurls []string
-	for _, id := range identifiers {
-		z, err := authorize(ctx, p.client, id)
-		if err != nil {
-			log.Fatalf("AuthorizeID(%+v): %v", id, err)
-		}
-		if z.Status == acme.StatusValid {
-			log.Printf("authz %s is valid; skipping", z.URI)
-			continue
-		}
-		if err := p.fulfill(ctx, z); err != nil {
-			log.Fatalf("fulfill(%s): %v", z.URI, err)
-		}
-		zurls = append(zurls, z.URI)
-		log.Printf("authorized for %+v", id)
-	}
-
-	// We should be all set now.
-	log.Print("all authorizations are done")
-	csr, certkey := newCSR(identifiers)
-	der, curl, err := p.client.CreateCert(ctx, csr, 48*time.Hour, true)
-	if err != nil {
-		log.Fatalf("CreateCert: %v", err)
-	}
-	log.Printf("cert URL: %s", curl)
-	if err := checkCert(der, identifiers); err != nil {
-		p.errorf("invalid cert: %v", err)
-	}
-
-	// Deactivate all authorizations we satisfied earlier.
-	for _, v := range zurls {
-		if err := p.client.RevokeAuthorization(ctx, v); err != nil {
-			p.errorf("RevokAuthorization(%q): %v", v, err)
-			continue
-		}
-	}
-	// Try revoking the issued cert using its private key.
-	if err := p.client.RevokeCert(ctx, certkey, der[0], acme.CRLReasonCessationOfOperation); err != nil {
-		p.errorf("RevokeCert: %v", err)
-	}
-
-}
-
 func (p *prober) fulfill(ctx context.Context, z *acme.Authorization) error {
 	var chal *acme.Challenge
 	for i, c := range z.Challenges {
@@ -20,12 +20,12 @@ import (
 	"math/big"
 )

-// keyID is the account identity provided by a CA during registration.
-type keyID string
+// KeyID is the account key identity provided by a CA during registration.
+type KeyID string

 // noKeyID indicates that jwsEncodeJSON should compute and use JWK instead of a KID.
 // See jwsEncodeJSON for details.
-const noKeyID = keyID("")
+const noKeyID = KeyID("")

 // noPayload indicates jwsEncodeJSON will encode zero-length octet string
 // in a JWS request. This is called POST-as-GET in RFC 8555 and is used to make
@@ -33,6 +33,10 @@ const noKeyID = keyID("")
 // See https://tools.ietf.org/html/rfc8555#section-6.3 for more details.
 const noPayload = ""

+// noNonce indicates that the nonce should be omitted from the protected header.
+// See jwsEncodeJSON for details.
+const noNonce = ""
+
 // jsonWebSignature can be easily serialized into a JWS following
 // https://tools.ietf.org/html/rfc7515#section-3.2.
 type jsonWebSignature struct {
@@ -43,32 +47,56 @@ type jsonWebSignature struct {

 // jwsEncodeJSON signs claimset using provided key and a nonce.
 // The result is serialized in JSON format containing either kid or jwk
-// fields based on the provided keyID value.
+// fields based on the provided KeyID value.
 //
-// If kid is non-empty, its quoted value is inserted in the protected head
+// The claimset is marshalled using json.Marshal unless it is a string.
+// In which case it is inserted directly into the message.
+//
+// If kid is non-empty, its quoted value is inserted in the protected header
 // as "kid" field value. Otherwise, JWK is computed using jwkEncode and inserted
 // as "jwk" field value. The "jwk" and "kid" fields are mutually exclusive.
 //
+// If nonce is non-empty, its quoted value is inserted in the protected header.
+//
 // See https://tools.ietf.org/html/rfc7515#section-7.
-func jwsEncodeJSON(claimset interface{}, key crypto.Signer, kid keyID, nonce, url string) ([]byte, error) {
+func jwsEncodeJSON(claimset interface{}, key crypto.Signer, kid KeyID, nonce, url string) ([]byte, error) {
+	if key == nil {
+		return nil, errors.New("nil key")
+	}
 	alg, sha := jwsHasher(key.Public())
 	if alg == "" || !sha.Available() {
 		return nil, ErrUnsupportedKey
 	}
-	var phead string
+	headers := struct {
+		Alg   string          `json:"alg"`
+		KID   string          `json:"kid,omitempty"`
+		JWK   json.RawMessage `json:"jwk,omitempty"`
+		Nonce string          `json:"nonce,omitempty"`
+		URL   string          `json:"url"`
+	}{
+		Alg:   alg,
+		Nonce: nonce,
+		URL:   url,
+	}
 	switch kid {
 	case noKeyID:
 		jwk, err := jwkEncode(key.Public())
 		if err != nil {
 			return nil, err
 		}
-		phead = fmt.Sprintf(`{"alg":%q,"jwk":%s,"nonce":%q,"url":%q}`, alg, jwk, nonce, url)
+		headers.JWK = json.RawMessage(jwk)
 	default:
-		phead = fmt.Sprintf(`{"alg":%q,"kid":%q,"nonce":%q,"url":%q}`, alg, kid, nonce, url)
+		headers.KID = string(kid)
 	}
-	phead = base64.RawURLEncoding.EncodeToString([]byte(phead))
+	phJSON, err := json.Marshal(headers)
+	if err != nil {
+		return nil, err
+	}
+	phead := base64.RawURLEncoding.EncodeToString([]byte(phJSON))
 	var payload string
-	if claimset != noPayload {
+	if val, ok := claimset.(string); ok {
+		payload = val
+	} else {
 		cs, err := json.Marshal(claimset)
 		if err != nil {
 			return nil, err
@@ -195,8 +195,46 @@ func TestJWSEncodeJSON(t *testing.T) {
 	}
 }

+func TestJWSEncodeNoNonce(t *testing.T) {
+	kid := KeyID("https://example.org/account/1")
+	claims := "RawString"
+	const (
+		// {"alg":"ES256","kid":"https://example.org/account/1","nonce":"nonce","url":"url"}
+		protected = "eyJhbGciOiJFUzI1NiIsImtpZCI6Imh0dHBzOi8vZXhhbXBsZS5vcmcvYWNjb3VudC8xIiwidXJsIjoidXJsIn0"
+		// "Raw String"
+		payload = "RawString"
+	)
+
+	b, err := jwsEncodeJSON(claims, testKeyEC, kid, "", "url")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var jws struct{ Protected, Payload, Signature string }
+	if err := json.Unmarshal(b, &jws); err != nil {
+		t.Fatal(err)
+	}
+	if jws.Protected != protected {
+		t.Errorf("protected:\n%s\nwant:\n%s", jws.Protected, protected)
+	}
+	if jws.Payload != payload {
+		t.Errorf("payload:\n%s\nwant:\n%s", jws.Payload, payload)
+	}
+
+	sig, err := base64.RawURLEncoding.DecodeString(jws.Signature)
+	if err != nil {
+		t.Fatalf("jws.Signature: %v", err)
+	}
+	r, s := big.NewInt(0), big.NewInt(0)
+	r.SetBytes(sig[:len(sig)/2])
+	s.SetBytes(sig[len(sig)/2:])
+	h := sha256.Sum256([]byte(protected + "." + payload))
+	if !ecdsa.Verify(testKeyEC.Public().(*ecdsa.PublicKey), h[:], r, s) {
+		t.Error("invalid signature")
+	}
+}
+
 func TestJWSEncodeKID(t *testing.T) {
-	kid := keyID("https://example.org/account/1")
+	kid := KeyID("https://example.org/account/1")
 	claims := struct{ Msg string }{"Hello JWS"}
 	// JWS signed with testKeyEC
 	const (
@@ -13,7 +13,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"time"
 )
@@ -24,6 +23,9 @@ import (
 //
 // It only works with CAs implementing RFC 8555.
 func (c *Client) DeactivateReg(ctx context.Context) error {
+	if _, err := c.Discover(ctx); err != nil { // required by c.accountKID
+		return err
+	}
 	url := string(c.accountKID(ctx))
 	if url == "" {
 		return ErrNoAccount
@@ -78,7 +80,7 @@ func (c *Client) registerRFC(ctx context.Context, acct *Account, prompt func(tos
 	}
 	// Cache Account URL even if we return an error to the caller.
 	// It is by all means a valid and usable "kid" value for future requests.
-	c.kid = keyID(a.URI)
+	c.KID = KeyID(a.URI)
 	if res.StatusCode == http.StatusOK {
 		return nil, ErrAccountAlreadyExists
 	}
@@ -115,7 +117,7 @@ func (c *Client) updateRegRFC(ctx context.Context, a *Account) (*Account, error)
 	return responseAccount(res)
 }

-// getGegRFC is equivalent to c.GetReg but for CAs implementing RFC 8555.
+// getRegRFC is equivalent to c.GetReg but for CAs implementing RFC 8555.
 // It expects c.Discover to have already been called.
 func (c *Client) getRegRFC(ctx context.Context) (*Account, error) {
 	req := json.RawMessage(`{"onlyReturnExisting": true}`)
@@ -148,6 +150,42 @@ func responseAccount(res *http.Response) (*Account, error) {
 	}, nil
 }

+// accountKeyRollover attempts to perform account key rollover.
+// On success it will change client.Key to the new key.
+func (c *Client) accountKeyRollover(ctx context.Context, newKey crypto.Signer) error {
+	dir, err := c.Discover(ctx) // Also required by c.accountKID
+	if err != nil {
+		return err
+	}
+	kid := c.accountKID(ctx)
+	if kid == noKeyID {
+		return ErrNoAccount
+	}
+	oldKey, err := jwkEncode(c.Key.Public())
+	if err != nil {
+		return err
+	}
+	payload := struct {
+		Account string          `json:"account"`
+		OldKey  json.RawMessage `json:"oldKey"`
+	}{
+		Account: string(kid),
+		OldKey:  json.RawMessage(oldKey),
+	}
+	inner, err := jwsEncodeJSON(payload, newKey, noKeyID, noNonce, dir.KeyChangeURL)
+	if err != nil {
+		return err
+	}
+
+	res, err := c.post(ctx, nil, dir.KeyChangeURL, base64.RawURLEncoding.EncodeToString(inner), wantStatus(http.StatusOK))
+	if err != nil {
+		return err
+	}
+	defer res.Body.Close()
+	c.Key = newKey
+	return nil
+}
+
 // AuthorizeOrder initiates the order-based application for certificate issuance,
 // as opposed to pre-authorization in Authorize.
 // It is only supported by CAs implementing RFC 8555.
@@ -351,7 +389,7 @@ func (c *Client) fetchCertRFC(ctx context.Context, url string, bundle bool) ([][
 	// Get all the bytes up to a sane maximum.
 	// Account very roughly for base64 overhead.
 	const max = maxCertChainSize + maxCertChainSize/33
-	b, err := ioutil.ReadAll(io.LimitReader(res.Body, max+1))
+	b, err := io.ReadAll(io.LimitReader(res.Body, max+1))
 	if err != nil {
 		return nil, fmt.Errorf("acme: fetch cert response stream: %v", err)
 	}
@@ -410,3 +448,29 @@ func isAlreadyRevoked(err error) bool {
 	e, ok := err.(*Error)
 	return ok && e.ProblemType == "urn:ietf:params:acme:error:alreadyRevoked"
 }
+
+// ListCertAlternates retrieves any alternate certificate chain URLs for the
+// given certificate chain URL. These alternate URLs can be passed to FetchCert
+// in order to retrieve the alternate certificate chains.
+//
+// If there are no alternate issuer certificate chains, a nil slice will be
+// returned.
+func (c *Client) ListCertAlternates(ctx context.Context, url string) ([]string, error) {
+	if _, err := c.Discover(ctx); err != nil { // required by c.accountKID
+		return nil, err
+	}
+
+	res, err := c.postAsGet(ctx, url, wantStatus(http.StatusOK))
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+
+	// We don't need the body but we need to discard it so we don't end up
+	// preventing keep-alive
+	if _, err := io.Copy(io.Discard, res.Body); err != nil {
+		return nil, fmt.Errorf("acme: cert alternates response stream: %v", err)
+	}
+	alts := linkHeader(res.Header, "alternate")
+	return alts, nil
+}
@@ -15,12 +15,14 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"encoding/pem"
+	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"math/big"
 	"net/http"
 	"net/http/httptest"
 	"reflect"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -62,7 +64,7 @@ func TestRFC_Discover(t *testing.T) {
 		}`, nonce, reg, order, authz, revoke, keychange, metaTerms, metaWebsite, metaCAA)
 	}))
 	defer ts.Close()
-	c := Client{DirectoryURL: ts.URL}
+	c := &Client{DirectoryURL: ts.URL}
 	dir, err := c.Discover(context.Background())
 	if err != nil {
 		t.Fatal(err)
@@ -146,7 +148,7 @@ func TestRFC_postKID(t *testing.T) {
 			w.Header().Set("Location", "/account-1")
 			w.Write([]byte(`{"status":"valid"}`))
 		case "/post":
-			b, _ := ioutil.ReadAll(r.Body) // check err later in decodeJWSxxx
+			b, _ := io.ReadAll(r.Body) // check err later in decodeJWSxxx
 			head, err := decodeJWSHead(bytes.NewReader(b))
 			if err != nil {
 				t.Errorf("decodeJWSHead: %v", err)
@@ -175,8 +177,7 @@ func TestRFC_postKID(t *testing.T) {
 	}))
 	defer ts.Close()

-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
+	ctx := context.Background()
 	cl := &Client{
 		Key:          testKey,
 		DirectoryURL: ts.URL,
@@ -192,13 +193,13 @@ func TestRFC_postKID(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer res.Body.Close()
-	b, _ := ioutil.ReadAll(res.Body) // don't care about err - just checking b
+	b, _ := io.ReadAll(res.Body) // don't care about err - just checking b
 	if string(b) != "pong" {
 		t.Errorf("res.Body = %q; want pong", b)
 	}
 }

-// acmeServer simulates a subset of RFC8555 compliant CA.
+// acmeServer simulates a subset of RFC 8555 compliant CA.
 //
 // TODO: We also have x/crypto/acme/autocert/acmetest and startACMEServerStub in autocert_test.go.
 // It feels like this acmeServer is a sweet spot between usefulness and added complexity.
@@ -232,6 +233,7 @@ func (s *acmeServer) start() {
 				"newOrder": %q,
 				"newAuthz": %q,
 				"revokeCert": %q,
+				"keyChange": %q,
 				"meta": {"termsOfService": %q}
 				}`,
 				s.url("/acme/new-nonce"),
@@ -239,6 +241,7 @@ func (s *acmeServer) start() {
 				s.url("/acme/new-order"),
 				s.url("/acme/new-authz"),
 				s.url("/acme/revoke-cert"),
+				s.url("/acme/key-change"),
 				s.url("/terms"),
 			)
 			return
@@ -293,7 +296,7 @@ func TestRFC_Register(t *testing.T) {
 			"orders": %q
 		}`, email, s.url("/accounts/1/orders"))

-		b, _ := ioutil.ReadAll(r.Body) // check err later in decodeJWSxxx
+		b, _ := io.ReadAll(r.Body) // check err later in decodeJWSxxx
 		head, err := decodeJWSHead(bytes.NewReader(b))
 		if err != nil {
 			t.Errorf("decodeJWSHead: %v", err)
@@ -312,8 +315,7 @@ func TestRFC_Register(t *testing.T) {
 	s.start()
 	defer s.close()

-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
+	ctx := context.Background()
 	cl := &Client{
 		Key:          testKeyEC,
 		DirectoryURL: s.url("/"),
@@ -344,7 +346,7 @@ func TestRFC_Register(t *testing.T) {
 	if !didPrompt {
 		t.Error("tos prompt wasn't called")
 	}
-	if v := cl.accountKID(ctx); v != keyID(okAccount.URI) {
+	if v := cl.accountKID(ctx); v != KeyID(okAccount.URI) {
 		t.Errorf("account kid = %q; want %q", v, okAccount.URI)
 	}
 }
@@ -450,8 +452,7 @@ func TestRFC_RegisterExternalAccountBinding(t *testing.T) {
 	s.start()
 	defer s.close()

-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
+	ctx := context.Background()
 	cl := &Client{
 		Key:          testKeyEC,
 		DirectoryURL: s.url("/"),
@@ -482,7 +483,7 @@ func TestRFC_RegisterExternalAccountBinding(t *testing.T) {
 	if !didPrompt {
 		t.Error("tos prompt wasn't called")
 	}
-	if v := cl.accountKID(ctx); v != keyID(okAccount.URI) {
+	if v := cl.accountKID(ctx); v != KeyID(okAccount.URI) {
 		t.Errorf("account kid = %q; want %q", v, okAccount.URI)
 	}
 }
@@ -502,7 +503,7 @@ func TestRFC_RegisterExisting(t *testing.T) {
 	if err != ErrAccountAlreadyExists {
 		t.Errorf("err = %v; want %v", err, ErrAccountAlreadyExists)
 	}
-	kid := keyID(s.url("/accounts/1"))
+	kid := KeyID(s.url("/accounts/1"))
 	if v := cl.accountKID(context.Background()); v != kid {
 		t.Errorf("account kid = %q; want %q", v, kid)
 	}
@@ -524,7 +525,7 @@ func TestRFC_UpdateReg(t *testing.T) {
 		w.WriteHeader(http.StatusOK)
 		w.Write([]byte(`{"status": "valid"}`))

-		b, _ := ioutil.ReadAll(r.Body) // check err later in decodeJWSxxx
+		b, _ := io.ReadAll(r.Body) // check err later in decodeJWSxxx
 		head, err := decodeJWSHead(bytes.NewReader(b))
 		if err != nil {
 			t.Errorf("decodeJWSHead: %v", err)
@@ -621,6 +622,128 @@ func TestRFC_GetRegOtherError(t *testing.T) {
 	}
 }

+func TestRFC_AccountKeyRollover(t *testing.T) {
+	s := newACMEServer()
+	s.handle("/acme/new-account", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Location", s.url("/accounts/1"))
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(`{"status": "valid"}`))
+	})
+	s.handle("/acme/key-change", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	})
+	s.start()
+	defer s.close()
+
+	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
+	if err := cl.AccountKeyRollover(context.Background(), testKeyEC384); err != nil {
+		t.Errorf("AccountKeyRollover: %v, wanted no error", err)
+	} else if cl.Key != testKeyEC384 {
+		t.Error("AccountKeyRollover did not rotate the client key")
+	}
+}
+
+func TestRFC_DeactivateReg(t *testing.T) {
+	const email = "mailto:user@example.org"
+	curStatus := StatusValid
+
+	type account struct {
+		Status    string   `json:"status"`
+		Contact   []string `json:"contact"`
+		AcceptTOS bool     `json:"termsOfServiceAgreed"`
+		Orders    string   `json:"orders"`
+	}
+
+	s := newACMEServer()
+	s.handle("/acme/new-account", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Location", s.url("/accounts/1"))
+		w.WriteHeader(http.StatusOK) // 200 means existing account
+		json.NewEncoder(w).Encode(account{
+			Status:    curStatus,
+			Contact:   []string{email},
+			AcceptTOS: true,
+			Orders:    s.url("/accounts/1/orders"),
+		})
+
+		b, _ := io.ReadAll(r.Body) // check err later in decodeJWSxxx
+		head, err := decodeJWSHead(bytes.NewReader(b))
+		if err != nil {
+			t.Errorf("decodeJWSHead: %v", err)
+			return
+		}
+		if len(head.JWK) == 0 {
+			t.Error("head.JWK is empty")
+		}
+
+		var req struct {
+			Status       string   `json:"status"`
+			Contact      []string `json:"contact"`
+			AcceptTOS    bool     `json:"termsOfServiceAgreed"`
+			OnlyExisting bool     `json:"onlyReturnExisting"`
+		}
+		decodeJWSRequest(t, &req, bytes.NewReader(b))
+		if !req.OnlyExisting {
+			t.Errorf("req.OnlyReturnExisting = %t; want = %t", req.OnlyExisting, true)
+		}
+	})
+	s.handle("/accounts/1", func(w http.ResponseWriter, r *http.Request) {
+		if curStatus == StatusValid {
+			curStatus = StatusDeactivated
+			w.WriteHeader(http.StatusOK)
+		} else {
+			s.error(w, &wireError{
+				Status: http.StatusUnauthorized,
+				Type:   "urn:ietf:params:acme:error:unauthorized",
+			})
+		}
+		var req account
+		b, _ := io.ReadAll(r.Body) // check err later in decodeJWSxxx
+		head, err := decodeJWSHead(bytes.NewReader(b))
+		if err != nil {
+			t.Errorf("decodeJWSHead: %v", err)
+			return
+		}
+		if len(head.JWK) != 0 {
+			t.Error("head.JWK is not empty")
+		}
+		if !strings.HasSuffix(head.KID, "/accounts/1") {
+			t.Errorf("head.KID = %q; want suffix /accounts/1", head.KID)
+		}
+
+		decodeJWSRequest(t, &req, bytes.NewReader(b))
+		if req.Status != StatusDeactivated {
+			t.Errorf("req.Status = %q; want = %q", req.Status, StatusDeactivated)
+		}
+	})
+	s.start()
+	defer s.close()
+
+	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
+	if err := cl.DeactivateReg(context.Background()); err != nil {
+		t.Errorf("DeactivateReg: %v, wanted no error", err)
+	}
+	if err := cl.DeactivateReg(context.Background()); err == nil {
+		t.Errorf("DeactivateReg: %v, wanted error for unauthorized", err)
+	}
+}
+
+func TestRF_DeactivateRegNoAccount(t *testing.T) {
+	s := newACMEServer()
+	s.handle("/acme/new-account", func(w http.ResponseWriter, r *http.Request) {
+		s.error(w, &wireError{
+			Status: http.StatusBadRequest,
+			Type:   "urn:ietf:params:acme:error:accountDoesNotExist",
+		})
+	})
+	s.start()
+	defer s.close()
+
+	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
+	if err := cl.DeactivateReg(context.Background()); !errors.Is(err, ErrNoAccount) {
+		t.Errorf("DeactivateReg: %v, wanted ErrNoAccount", err)
+	}
+}
+
 func TestRFC_AuthorizeOrder(t *testing.T) {
 	s := newACMEServer()
 	s.handle("/acme/new-account", func(w http.ResponseWriter, r *http.Request) {
@@ -741,24 +864,13 @@ func testWaitOrderStatus(t *testing.T, okStatus string) {
 	s.start()
 	defer s.close()

-	var order *Order
-	var err error
-	done := make(chan struct{})
-	go func() {
-		cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
-		order, err = cl.WaitOrder(context.Background(), s.url("/orders/1"))
-		close(done)
-	}()
-	select {
-	case <-time.After(3 * time.Second):
-		t.Fatal("WaitOrder took too long to return")
-	case <-done:
-		if err != nil {
-			t.Fatalf("WaitOrder: %v", err)
-		}
-		if order.Status != okStatus {
-			t.Errorf("order.Status = %q; want %q", order.Status, okStatus)
-		}
+	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
+	order, err := cl.WaitOrder(context.Background(), s.url("/orders/1"))
+	if err != nil {
+		t.Fatalf("WaitOrder: %v", err)
+	}
+	if order.Status != okStatus {
+		t.Errorf("order.Status = %q; want %q", order.Status, okStatus)
 	}
 }

@@ -783,30 +895,20 @@ func TestRFC_WaitOrderError(t *testing.T) {
 	s.start()
 	defer s.close()

-	var err error
-	done := make(chan struct{})
-	go func() {
-		cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
-		_, err = cl.WaitOrder(context.Background(), s.url("/orders/1"))
-		close(done)
-	}()
-	select {
-	case <-time.After(3 * time.Second):
-		t.Fatal("WaitOrder took too long to return")
-	case <-done:
-		if err == nil {
-			t.Fatal("WaitOrder returned nil error")
-		}
-		e, ok := err.(*OrderError)
-		if !ok {
-			t.Fatalf("err = %v (%T); want OrderError", err, err)
-		}
-		if e.OrderURL != s.url("/orders/1") {
-			t.Errorf("e.OrderURL = %q; want %q", e.OrderURL, s.url("/orders/1"))
-		}
-		if e.Status != StatusInvalid {
-			t.Errorf("e.Status = %q; want %q", e.Status, StatusInvalid)
-		}
+	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
+	_, err := cl.WaitOrder(context.Background(), s.url("/orders/1"))
+	if err == nil {
+		t.Fatal("WaitOrder returned nil error")
+	}
+	e, ok := err.(*OrderError)
+	if !ok {
+		t.Fatalf("err = %v (%T); want OrderError", err, err)
+	}
+	if e.OrderURL != s.url("/orders/1") {
+		t.Errorf("e.OrderURL = %q; want %q", e.OrderURL, s.url("/orders/1"))
+	}
+	if e.Status != StatusInvalid {
+		t.Errorf("e.Status = %q; want %q", e.Status, StatusInvalid)
 	}
 }

@@ -846,8 +948,7 @@ func TestRFC_CreateOrderCert(t *testing.T) {
 	})
 	s.start()
 	defer s.close()
-	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
-	defer cancel()
+	ctx := context.Background()

 	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
 	cert, curl, err := cl.CreateOrderCert(ctx, s.url("/pleaseissue"), csr, true)
@@ -882,3 +983,35 @@ func TestRFC_AlreadyRevokedCert(t *testing.T) {
 		t.Fatalf("RevokeCert: %v", err)
 	}
 }
+
+func TestRFC_ListCertAlternates(t *testing.T) {
+	s := newACMEServer()
+	s.handle("/crt", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/pem-certificate-chain")
+		w.Header().Add("Link", `<https://example.com/crt/2>;rel="alternate"`)
+		w.Header().Add("Link", `<https://example.com/crt/3>; rel="alternate"`)
+		w.Header().Add("Link", `<https://example.com/acme>; rel="index"`)
+	})
+	s.handle("/crt2", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/pem-certificate-chain")
+	})
+	s.start()
+	defer s.close()
+
+	cl := &Client{Key: testKeyEC, DirectoryURL: s.url("/")}
+	crts, err := cl.ListCertAlternates(context.Background(), s.url("/crt"))
+	if err != nil {
+		t.Fatalf("ListCertAlternates: %v", err)
+	}
+	want := []string{"https://example.com/crt/2", "https://example.com/crt/3"}
+	if !reflect.DeepEqual(crts, want) {
+		t.Errorf("ListCertAlternates(/crt): %v; want %v", crts, want)
+	}
+	crts, err = cl.ListCertAlternates(context.Background(), s.url("/crt2"))
+	if err != nil {
+		t.Fatalf("ListCertAlternates: %v", err)
+	}
+	if crts != nil {
+		t.Errorf("ListCertAlternates(/crt2): %v; want nil", crts)
+	}
+}
@@ -297,7 +297,7 @@ type Directory struct {

 	// CAA consists of lowercase hostname elements, which the ACME server
 	// recognises as referring to itself for the purposes of CAA record validation
-	// as defined in RFC6844.
+	// as defined in RFC 6844.
 	CAA []string

 	// ExternalAccountRequired indicates that the CA requires for all account-related
@@ -305,14 +305,6 @@ type Directory struct {
 	ExternalAccountRequired bool
 }

-// rfcCompliant reports whether the ACME server implements RFC 8555.
-// Note that some servers may have incomplete RFC implementation
-// even if the returned value is true.
-// If rfcCompliant reports false, the server most likely implements draft-02.
-func (d *Directory) rfcCompliant() bool {
-	return d.OrderURL != ""
-}
-
 // Order represents a client's request for a certificate.
 // It tracks the request flow progress through to issuance.
 type Order struct {
@@ -448,7 +440,7 @@ func DomainIDs(names ...string) []AuthzID {

 // IPIDs creates a slice of AuthzID with "ip" identifier type.
 // Each element of addr is textual form of an address as defined
-// in RFC1123 Section 2.1 for IPv4 and in RFC5952 Section 4 for IPv6.
+// in RFC 1123 Section 2.1 for IPv4 and in RFC 5952 Section 4 for IPv6.
 func IPIDs(addr ...string) []AuthzID {
 	a := make([]AuthzID, len(addr))
 	for i, v := range addr {
@@ -1,28 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.12
-// +build go1.12
-
-package acme
-
-import "runtime/debug"
-
-func init() {
-	// Set packageVersion if the binary was built in modules mode and x/crypto
-	// was not replaced with a different module.
-	info, ok := debug.ReadBuildInfo()
-	if !ok {
-		return
-	}
-	for _, m := range info.Deps {
-		if m.Path != "golang.org/x/crypto" {
-			continue
-		}
-		if m.Replace == nil {
-			packageVersion = m.Version
-		}
-		break
-	}
-}
@@ -11,8 +11,7 @@
 // If you aren't sure which function you need, use Argon2id (IDKey) and
 // the parameter recommendations for your scenario.
 //
-//
-// Argon2i
+// # Argon2i
 //
 // Argon2i (implemented by Key) is the side-channel resistant version of Argon2.
 // It uses data-independent memory access, which is preferred for password
@@ -21,8 +20,7 @@
 // parameters (taken from [2]) for non-interactive operations are time=3 and to
 // use the maximum available memory.
 //
-//
-// Argon2id
+// # Argon2id
 //
 // Argon2id (implemented by IDKey) is a hybrid version of Argon2 combining
 // Argon2i and Argon2d. It uses data-independent memory access for the first
@@ -59,7 +57,7 @@ const (
 // For example, you can get a derived key for e.g. AES-256 (which needs a
 // 32-byte key) by doing:
 //
-//      key := argon2.Key([]byte("some password"), salt, 3, 32*1024, 4, 32)
+//	key := argon2.Key([]byte("some password"), salt, 3, 32*1024, 4, 32)
 //
 // The draft RFC recommends[2] time=3, and memory=32*1024 is a sensible number.
 // If using that amount of memory (32 MB) is not possible in some contexts then
@@ -83,7 +81,7 @@ func Key(password, salt []byte, time, memory uint32, threads uint8, keyLen uint3
 // For example, you can get a derived key for e.g. AES-256 (which needs a
 // 32-byte key) by doing:
 //
-//      key := argon2.IDKey([]byte("some password"), salt, 1, 64*1024, 4, 32)
+//	key := argon2.IDKey([]byte("some password"), salt, 1, 64*1024, 4, 32)
 //
 // The draft RFC recommends[2] time=1, and memory=64*1024 is a sensible number.
 // If using that amount of memory (64 MB) is not possible in some contexts then
@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build amd64 && gc && !purego
-// +build amd64,gc,!purego

 package argon2

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build amd64,gc,!purego
+//go:build amd64 && gc && !purego

 #include "textflag.h"

@@ -199,8 +199,8 @@ TEXT ·mixBlocksSSE2(SB), 4, $0-32
 	MOVQ out+0(FP), DX
 	MOVQ a+8(FP), AX
 	MOVQ b+16(FP), BX
-	MOVQ a+24(FP), CX
-	MOVQ $128, BP
+	MOVQ c+24(FP), CX
+	MOVQ $128, DI

 loop:
 	MOVOU 0(AX), X0
@@ -213,7 +213,7 @@ loop:
 	ADDQ  $16, BX
 	ADDQ  $16, CX
 	ADDQ  $16, DX
-	SUBQ  $2, BP
+	SUBQ  $2, DI
 	JA    loop
 	RET

@@ -222,8 +222,8 @@ TEXT ·xorBlocksSSE2(SB), 4, $0-32
 	MOVQ out+0(FP), DX
 	MOVQ a+8(FP), AX
 	MOVQ b+16(FP), BX
-	MOVQ a+24(FP), CX
-	MOVQ $128, BP
+	MOVQ c+24(FP), CX
+	MOVQ $128, DI

 loop:
 	MOVOU 0(AX), X0
@@ -238,6 +238,6 @@ loop:
 	ADDQ  $16, BX
 	ADDQ  $16, CX
 	ADDQ  $16, DX
-	SUBQ  $2, BP
+	SUBQ  $2, DI
 	JA    loop
 	RET
@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build !amd64 || purego || !gc
-// +build !amd64 purego !gc

 package argon2

@@ -4,7 +4,7 @@

 // Package bcrypt implements Provos and Mazières's bcrypt adaptive hashing
 // algorithm. See http://www.usenix.org/event/usenix99/provos/provos.pdf
-package bcrypt // import "golang.org/x/crypto/bcrypt"
+package bcrypt

 // The code is a port of Provos and Mazières's C implementation.
 import (
@@ -50,7 +50,7 @@ func (ih InvalidHashPrefixError) Error() string {
 type InvalidCostError int

 func (ic InvalidCostError) Error() string {
-	return fmt.Sprintf("crypto/bcrypt: cost %d is outside allowed range (%d,%d)", int(ic), int(MinCost), int(MaxCost))
+	return fmt.Sprintf("crypto/bcrypt: cost %d is outside allowed range (%d,%d)", int(ic), MinCost, MaxCost)
 }

 const (
@@ -82,11 +82,20 @@ type hashed struct {
 	minor byte
 }

+// ErrPasswordTooLong is returned when the password passed to
+// GenerateFromPassword is too long (i.e. > 72 bytes).
+var ErrPasswordTooLong = errors.New("bcrypt: password length exceeds 72 bytes")
+
 // GenerateFromPassword returns the bcrypt hash of the password at the given
 // cost. If the cost given is less than MinCost, the cost will be set to
 // DefaultCost, instead. Use CompareHashAndPassword, as defined in this package,
 // to compare the returned hashed password with its cleartext version.
+// GenerateFromPassword does not accept passwords longer than 72 bytes, which
+// is the longest password bcrypt will operate on.
 func GenerateFromPassword(password []byte, cost int) ([]byte, error) {
+	if len(password) > 72 {
+		return nil, ErrPasswordTooLong
+	}
 	p, err := newFromPassword(password, cost)
 	if err != nil {
 		return nil, err
@@ -241,3 +241,10 @@ func TestNoSideEffectsFromCompare(t *testing.T) {
 		t.Errorf("got=%q want=%q", got, want)
 	}
 }
+
+func TestPasswordTooLong(t *testing.T) {
+	_, err := GenerateFromPassword(make([]byte, 73), 1)
+	if err != ErrPasswordTooLong {
+		t.Errorf("unexpected error: got %q, want %q", err, ErrPasswordTooLong)
+	}
+}
@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-//go:build go1.7 && amd64 && gc && !purego
-// +build go1.7,amd64,gc,!purego
+//go:build amd64 && gc && !purego

 package blake2b

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build go1.7,amd64,gc,!purego
+//go:build amd64 && gc && !purego

 #include "textflag.h"

@@ -1,25 +0,0 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.7 && amd64 && gc && !purego
-// +build !go1.7,amd64,gc,!purego
-
-package blake2b
-
-import "golang.org/x/sys/cpu"
-
-func init() {
-	useSSE4 = cpu.X86.HasSSE41
-}
-
-//go:noescape
-func hashBlocksSSE4(h *[8]uint64, c *[2]uint64, flag uint64, blocks []byte)
-
-func hashBlocks(h *[8]uint64, c *[2]uint64, flag uint64, blocks []byte) {
-	if useSSE4 {
-		hashBlocksSSE4(h, c, flag, blocks)
-	} else {
-		hashBlocksGeneric(h, c, flag, blocks)
-	}
-}
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build amd64,gc,!purego
+//go:build amd64 && gc && !purego

 #include "textflag.h"

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build !amd64 || purego || !gc
-// +build !amd64 purego !gc

 package blake2b

@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-//go:build go1.9
-// +build go1.9
-
 package blake2b

 import (
@@ -16,9 +16,10 @@
 //
 // BLAKE2X is a construction to compute hash values larger than 32 bytes. It
 // can produce hash values between 0 and 65535 bytes.
-package blake2s // import "golang.org/x/crypto/blake2s"
+package blake2s

 import (
+	"crypto"
 	"encoding/binary"
 	"errors"
 	"hash"
@@ -55,6 +56,13 @@ func Sum256(data []byte) [Size]byte {
 // and BinaryUnmarshaler for state (de)serialization as documented by hash.Hash.
 func New256(key []byte) (hash.Hash, error) { return newDigest(Size, key) }

+func init() {
+	crypto.RegisterHash(crypto.BLAKE2s_256, func() hash.Hash {
+		h, _ := New256(nil)
+		return h
+	})
+}
+
 // New128 returns a new hash.Hash computing the BLAKE2s-128 checksum given a
 // non-empty key. Note that a 128-bit digest is too small to be secure as a
 // cryptographic hash and should only be used as a MAC, thus the key argument
@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build 386 && gc && !purego
-// +build 386,gc,!purego

 package blake2s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build 386,gc,!purego
+//go:build 386 && gc && !purego

 #include "textflag.h"

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build amd64 && gc && !purego
-// +build amd64,gc,!purego

 package blake2s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build amd64,gc,!purego
+//go:build amd64 && gc && !purego

 #include "textflag.h"

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build (!amd64 && !386) || !gc || purego
-// +build !amd64,!386 !gc purego

 package blake2s

@@ -1,22 +0,0 @@
-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.9
-// +build go1.9
-
-package blake2s
-
-import (
-	"crypto"
-	"hash"
-)
-
-func init() {
-	newHash256 := func() hash.Hash {
-		h, _ := New256(nil)
-		return h
-	}
-
-	crypto.RegisterHash(crypto.BLAKE2s_256, newHash256)
-}
@@ -11,7 +11,7 @@
 // Deprecated: any new system should use AES (from crypto/aes, if necessary in
 // an AEAD mode like crypto/cipher.NewGCM) or XChaCha20-Poly1305 (from
 // golang.org/x/crypto/chacha20poly1305).
-package blowfish // import "golang.org/x/crypto/blowfish"
+package blowfish

 // The code is a port of Bruce Schneier's C implementation.
 // See https://www.schneier.com/blowfish.html.
@@ -23,7 +23,7 @@
 // elliptic curve. This package is frozen, and not implemented in constant time.
 // There is a more complete implementation at github.com/cloudflare/bn256, but
 // note that it suffers from the same security issues of the underlying curve.
-package bn256 // import "golang.org/x/crypto/bn256"
+package bn256

 import (
 	"crypto/rand"
@@ -162,7 +162,7 @@ type G2 struct {
 	p *twistPoint
 }

-// RandomG1 returns x and g₂ˣ where x is a random, non-zero number read from r.
+// RandomG2 returns x and g₂ˣ where x is a random, non-zero number read from r.
 func RandomG2(r io.Reader) (*big.Int, *G2, error) {
 	var k *big.Int
 	var err error
@@ -11,9 +11,12 @@
 // Deprecated: any new system should use AES (from crypto/aes, if necessary in
 // an AEAD mode like crypto/cipher.NewGCM) or XChaCha20-Poly1305 (from
 // golang.org/x/crypto/chacha20poly1305).
-package cast5 // import "golang.org/x/crypto/cast5"
+package cast5

-import "errors"
+import (
+	"errors"
+	"math/bits"
+)

 const BlockSize = 8
 const KeySize = 16
@@ -241,19 +244,19 @@ func (c *Cipher) keySchedule(in []byte) {
 // These are the three 'f' functions. See RFC 2144, section 2.2.
 func f1(d, m uint32, r uint8) uint32 {
 	t := m + d
-	I := (t << r) | (t >> (32 - r))
+	I := bits.RotateLeft32(t, int(r))
 	return ((sBox[0][I>>24] ^ sBox[1][(I>>16)&0xff]) - sBox[2][(I>>8)&0xff]) + sBox[3][I&0xff]
 }

 func f2(d, m uint32, r uint8) uint32 {
 	t := m ^ d
-	I := (t << r) | (t >> (32 - r))
+	I := bits.RotateLeft32(t, int(r))
 	return ((sBox[0][I>>24] - sBox[1][(I>>16)&0xff]) + sBox[2][(I>>8)&0xff]) ^ sBox[3][I&0xff]
 }

 func f3(d, m uint32, r uint8) uint32 {
 	t := m - d
-	I := (t << r) | (t >> (32 - r))
+	I := bits.RotateLeft32(t, int(r))
 	return ((sBox[0][I>>24] + sBox[1][(I>>16)&0xff]) ^ sBox[2][(I>>8)&0xff]) - sBox[3][I&0xff]
 }

@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-//go:build go1.11 && gc && !purego
-// +build go1.11,gc,!purego
+//go:build gc && !purego

 package chacha20

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build go1.11,gc,!purego
+//go:build gc && !purego

 #include "textflag.h"

@@ -12,7 +12,7 @@ import (
 	"errors"
 	"math/bits"

-	"golang.org/x/crypto/internal/subtle"
+	"golang.org/x/crypto/internal/alias"
 )

 const (
@@ -189,7 +189,7 @@ func (s *Cipher) XORKeyStream(dst, src []byte) {
 		panic("chacha20: output smaller than input")
 	}
 	dst = dst[:len(src)]
-	if subtle.InexactOverlap(dst, src) {
+	if alias.InexactOverlap(dst, src) {
 		panic("chacha20: invalid buffer overlap")
 	}

@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-//go:build (!arm64 && !s390x && !ppc64le) || (arm64 && !go1.11) || !gc || purego
-// +build !arm64,!s390x,!ppc64le arm64,!go1.11 !gc purego
+//go:build (!arm64 && !s390x && !ppc64le) || !gc || purego

 package chacha20

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build gc && !purego
-// +build gc,!purego

 package chacha20

@@ -19,7 +19,7 @@
 // The differences in this and the original implementation are
 // due to the calling conventions and initialization of constants.

-// +build gc,!purego
+//go:build gc && !purego

 #include "textflag.h"

@@ -33,6 +33,9 @@
 #define CONSTBASE  R16
 #define BLOCKS R17

+// for VPERMXOR
+#define MASK  R18
+
 DATA consts<>+0x00(SB)/8, $0x3320646e61707865
 DATA consts<>+0x08(SB)/8, $0x6b20657479622d32
 DATA consts<>+0x10(SB)/8, $0x0000000000000001
@@ -53,7 +56,11 @@ DATA consts<>+0x80(SB)/8, $0x6b2065746b206574
 DATA consts<>+0x88(SB)/8, $0x6b2065746b206574
 DATA consts<>+0x90(SB)/8, $0x0000000100000000
 DATA consts<>+0x98(SB)/8, $0x0000000300000002
-GLOBL consts<>(SB), RODATA, $0xa0
+DATA consts<>+0xa0(SB)/8, $0x5566774411223300
+DATA consts<>+0xa8(SB)/8, $0xddeeffcc99aabb88
+DATA consts<>+0xb0(SB)/8, $0x6677445522330011
+DATA consts<>+0xb8(SB)/8, $0xeeffccddaabb8899
+GLOBL consts<>(SB), RODATA, $0xc0

 //func chaCha20_ctr32_vsx(out, inp *byte, len int, key *[8]uint32, counter *uint32)
 TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40
@@ -70,6 +77,9 @@ TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40
 	MOVD $48, R10
 	MOVD $64, R11
 	SRD $6, LEN, BLOCKS
+	// for VPERMXOR
+	MOVD $consts<>+0xa0(SB), MASK
+	MOVD $16, R20
 	// V16
 	LXVW4X (CONSTBASE)(R0), VS48
 	ADD $80,CONSTBASE
@@ -87,6 +97,10 @@ TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40
 	// V28
 	LXVW4X (CONSTBASE)(R11), VS60

+	// Load mask constants for VPERMXOR
+	LXVW4X (MASK)(R0), V20
+	LXVW4X (MASK)(R20), V21
+
 	// splat slot from V19 -> V26
 	VSPLTW $0, V19, V26

@@ -97,7 +111,7 @@ TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40

 	MOVD $10, R14
 	MOVD R14, CTR
-
+	PCALIGN $16
 loop_outer_vsx:
 	// V0, V1, V2, V3
 	LXVW4X (R0)(CONSTBASE), VS32
@@ -128,22 +142,17 @@ loop_outer_vsx:
 	VSPLTISW $12, V28
 	VSPLTISW $8, V29
 	VSPLTISW $7, V30
-
+	PCALIGN $16
 loop_vsx:
 	VADDUWM V0, V4, V0
 	VADDUWM V1, V5, V1
 	VADDUWM V2, V6, V2
 	VADDUWM V3, V7, V3

-	VXOR V12, V0, V12
-	VXOR V13, V1, V13
-	VXOR V14, V2, V14
-	VXOR V15, V3, V15
-
-	VRLW V12, V27, V12
-	VRLW V13, V27, V13
-	VRLW V14, V27, V14
-	VRLW V15, V27, V15
+	VPERMXOR V12, V0, V21, V12
+	VPERMXOR V13, V1, V21, V13
+	VPERMXOR V14, V2, V21, V14
+	VPERMXOR V15, V3, V21, V15

 	VADDUWM V8, V12, V8
 	VADDUWM V9, V13, V9
@@ -165,15 +174,10 @@ loop_vsx:
 	VADDUWM V2, V6, V2
 	VADDUWM V3, V7, V3

-	VXOR V12, V0, V12
-	VXOR V13, V1, V13
-	VXOR V14, V2, V14
-	VXOR V15, V3, V15
-
-	VRLW V12, V29, V12
-	VRLW V13, V29, V13
-	VRLW V14, V29, V14
-	VRLW V15, V29, V15
+	VPERMXOR V12, V0, V20, V12
+	VPERMXOR V13, V1, V20, V13
+	VPERMXOR V14, V2, V20, V14
+	VPERMXOR V15, V3, V20, V15

 	VADDUWM V8, V12, V8
 	VADDUWM V9, V13, V9
@@ -195,15 +199,10 @@ loop_vsx:
 	VADDUWM V2, V7, V2
 	VADDUWM V3, V4, V3

-	VXOR V15, V0, V15
-	VXOR V12, V1, V12
-	VXOR V13, V2, V13
-	VXOR V14, V3, V14
-
-	VRLW V15, V27, V15
-	VRLW V12, V27, V12
-	VRLW V13, V27, V13
-	VRLW V14, V27, V14
+	VPERMXOR V15, V0, V21, V15
+	VPERMXOR V12, V1, V21, V12
+	VPERMXOR V13, V2, V21, V13
+	VPERMXOR V14, V3, V21, V14

 	VADDUWM V10, V15, V10
 	VADDUWM V11, V12, V11
@@ -225,15 +224,10 @@ loop_vsx:
 	VADDUWM V2, V7, V2
 	VADDUWM V3, V4, V3

-	VXOR V15, V0, V15
-	VXOR V12, V1, V12
-	VXOR V13, V2, V13
-	VXOR V14, V3, V14
-
-	VRLW V15, V29, V15
-	VRLW V12, V29, V12
-	VRLW V13, V29, V13
-	VRLW V14, V29, V14
+	VPERMXOR V15, V0, V20, V15
+	VPERMXOR V12, V1, V20, V12
+	VPERMXOR V13, V2, V20, V13
+	VPERMXOR V14, V3, V20, V14

 	VADDUWM V10, V15, V10
 	VADDUWM V11, V12, V11
@@ -249,48 +243,48 @@ loop_vsx:
 	VRLW V6, V30, V6
 	VRLW V7, V30, V7
 	VRLW V4, V30, V4
-	BC   16, LT, loop_vsx
+	BDNZ   loop_vsx

 	VADDUWM V12, V26, V12

-	WORD $0x13600F8C		// VMRGEW V0, V1, V27
-	WORD $0x13821F8C		// VMRGEW V2, V3, V28
+	VMRGEW V0, V1, V27
+	VMRGEW V2, V3, V28

-	WORD $0x10000E8C		// VMRGOW V0, V1, V0
-	WORD $0x10421E8C		// VMRGOW V2, V3, V2
+	VMRGOW V0, V1, V0
+	VMRGOW V2, V3, V2

-	WORD $0x13A42F8C		// VMRGEW V4, V5, V29
-	WORD $0x13C63F8C		// VMRGEW V6, V7, V30
+	VMRGEW V4, V5, V29
+	VMRGEW V6, V7, V30

 	XXPERMDI VS32, VS34, $0, VS33
 	XXPERMDI VS32, VS34, $3, VS35
 	XXPERMDI VS59, VS60, $0, VS32
 	XXPERMDI VS59, VS60, $3, VS34

-	WORD $0x10842E8C		// VMRGOW V4, V5, V4
-	WORD $0x10C63E8C		// VMRGOW V6, V7, V6
+	VMRGOW V4, V5, V4
+	VMRGOW V6, V7, V6

-	WORD $0x13684F8C		// VMRGEW V8, V9, V27
-	WORD $0x138A5F8C		// VMRGEW V10, V11, V28
+	VMRGEW V8, V9, V27
+	VMRGEW V10, V11, V28

 	XXPERMDI VS36, VS38, $0, VS37
 	XXPERMDI VS36, VS38, $3, VS39
 	XXPERMDI VS61, VS62, $0, VS36
 	XXPERMDI VS61, VS62, $3, VS38

-	WORD $0x11084E8C		// VMRGOW V8, V9, V8
-	WORD $0x114A5E8C		// VMRGOW V10, V11, V10
+	VMRGOW V8, V9, V8
+	VMRGOW V10, V11, V10

-	WORD $0x13AC6F8C		// VMRGEW V12, V13, V29
-	WORD $0x13CE7F8C		// VMRGEW V14, V15, V30
+	VMRGEW V12, V13, V29
+	VMRGEW V14, V15, V30

 	XXPERMDI VS40, VS42, $0, VS41
 	XXPERMDI VS40, VS42, $3, VS43
 	XXPERMDI VS59, VS60, $0, VS40
 	XXPERMDI VS59, VS60, $3, VS42

-	WORD $0x118C6E8C		// VMRGOW V12, V13, V12
-	WORD $0x11CE7E8C		// VMRGOW V14, V15, V14
+	VMRGOW V12, V13, V12
+	VMRGOW V14, V15, V14

 	VSPLTISW $4, V27
 	VADDUWM V26, V27, V26
@@ -431,7 +425,7 @@ tail_vsx:
 	ADD $-1, R11, R12
 	ADD $-1, INP
 	ADD $-1, OUT
-
+	PCALIGN $16
 looptail_vsx:
 	// Copying the result to OUT
 	// in bytes.
@@ -439,7 +433,7 @@ looptail_vsx:
 	MOVBZU 1(INP), TMP
 	XOR    KEY, TMP, KEY
 	MOVBU  KEY, 1(OUT)
-	BC     16, LT, looptail_vsx
+	BDNZ   looptail_vsx

 	// Clear the stack values
 	STXVW4X VS48, (R11)(R0)
@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build gc && !purego
-// +build gc,!purego

 package chacha20

@@ -15,6 +14,7 @@ const bufSize = 256

 // xorKeyStreamVX is an assembly implementation of XORKeyStream. It must only
 // be called when the vector facility is available. Implementation in asm_s390x.s.
+//
 //go:noescape
 func xorKeyStreamVX(dst, src []byte, key *[8]uint32, nonce *[3]uint32, counter *uint32)

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build gc,!purego
+//go:build gc && !purego

 #include "go_asm.h"
 #include "textflag.h"
@@ -5,7 +5,7 @@
 // Package chacha20poly1305 implements the ChaCha20-Poly1305 AEAD and its
 // extended nonce variant XChaCha20-Poly1305, as specified in RFC 8439 and
 // draft-irtf-cfrg-xchacha-01.
-package chacha20poly1305 // import "golang.org/x/crypto/chacha20poly1305"
+package chacha20poly1305

 import (
 	"crypto/cipher"
@@ -26,6 +26,10 @@ const (
 	// NonceSizeX is the size of the nonce used with the XChaCha20-Poly1305
 	// variant of this AEAD, in bytes.
 	NonceSizeX = 24
+
+	// Overhead is the size of the Poly1305 authentication tag, and the
+	// difference between a ciphertext length and its plaintext.
+	Overhead = 16
 )

 type chacha20poly1305 struct {
@@ -47,7 +51,7 @@ func (c *chacha20poly1305) NonceSize() int {
 }

 func (c *chacha20poly1305) Overhead() int {
-	return 16
+	return Overhead
 }

 func (c *chacha20poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte {
@@ -3,14 +3,13 @@
 // license that can be found in the LICENSE file.

 //go:build gc && !purego
-// +build gc,!purego

 package chacha20poly1305

 import (
 	"encoding/binary"

-	"golang.org/x/crypto/internal/subtle"
+	"golang.org/x/crypto/internal/alias"
 	"golang.org/x/sys/cpu"
 )

@@ -56,7 +55,7 @@ func (c *chacha20poly1305) seal(dst, nonce, plaintext, additionalData []byte) []
 	setupState(&state, &c.key, nonce)

 	ret, out := sliceForAppend(dst, len(plaintext)+16)
-	if subtle.InexactOverlap(out, plaintext) {
+	if alias.InexactOverlap(out, plaintext) {
 		panic("chacha20poly1305: invalid buffer overlap")
 	}
 	chacha20Poly1305Seal(out[:], state[:], plaintext, additionalData)
@@ -73,7 +72,7 @@ func (c *chacha20poly1305) open(dst, nonce, ciphertext, additionalData []byte) (

 	ciphertext = ciphertext[:len(ciphertext)-16]
 	ret, out := sliceForAppend(dst, len(ciphertext))
-	if subtle.InexactOverlap(out, ciphertext) {
+	if alias.InexactOverlap(out, ciphertext) {
 		panic("chacha20poly1305: invalid buffer overlap")
 	}
 	if !chacha20Poly1305Open(out, state[:], ciphertext, additionalData) {
@@ -4,7 +4,7 @@

 // This file was originally from https://golang.org/cl/24717 by Vlad Krasnov of CloudFlare.

-// +build gc,!purego
+//go:build gc && !purego

 #include "textflag.h"
 // General register allocation
@@ -183,11 +183,31 @@ GLOBL ·andMask<>(SB), (NOPTR+RODATA), $240
 #define shiftD1Right BYTE $0x66; BYTE $0x45; BYTE $0x0f; BYTE $0x3a; BYTE $0x0f; BYTE $0xd2; BYTE $0x04 // PALIGNR $4, X10, X10
 #define shiftD2Right BYTE $0x66; BYTE $0x45; BYTE $0x0f; BYTE $0x3a; BYTE $0x0f; BYTE $0xdb; BYTE $0x04 // PALIGNR $4, X11, X11
 #define shiftD3Right BYTE $0x66; BYTE $0x45; BYTE $0x0f; BYTE $0x3a; BYTE $0x0f; BYTE $0xff; BYTE $0x04 // PALIGNR $4, X15, X15
+
 // Some macros
+
+// ROL rotates the uint32s in register R left by N bits, using temporary T.
+#define ROL(N, R, T) \
+	MOVO R, T; PSLLL $(N), T; PSRLL $(32-(N)), R; PXOR T, R
+
+// ROL16 rotates the uint32s in register R left by 16, using temporary T if needed.
+#ifdef GOAMD64_v2
+#define ROL16(R, T) PSHUFB ·rol16<>(SB), R
+#else
+#define ROL16(R, T) ROL(16, R, T)
+#endif
+
+// ROL8 rotates the uint32s in register R left by 8, using temporary T if needed.
+#ifdef GOAMD64_v2
+#define ROL8(R, T) PSHUFB ·rol8<>(SB), R
+#else
+#define ROL8(R, T) ROL(8, R, T)
+#endif
+
 #define chachaQR(A, B, C, D, T) \
-	PADDD B, A; PXOR A, D; PSHUFB ·rol16<>(SB), D                            \
+	PADDD B, A; PXOR A, D; ROL16(D, T) \
 	PADDD D, C; PXOR C, B; MOVO B, T; PSLLL $12, T; PSRLL $20, B; PXOR T, B \
-	PADDD B, A; PXOR A, D; PSHUFB ·rol8<>(SB), D                             \
+	PADDD B, A; PXOR A, D; ROL8(D, T) \
 	PADDD D, C; PXOR C, B; MOVO B, T; PSLLL $7, T; PSRLL $25, B; PXOR T, B

 #define chachaQR_AVX2(A, B, C, D, T) \
@@ -8,8 +8,8 @@ import (
 	"encoding/binary"

 	"golang.org/x/crypto/chacha20"
-	"golang.org/x/crypto/internal/subtle"
-	"golang.org/x/crypto/poly1305"
+	"golang.org/x/crypto/internal/alias"
+	"golang.org/x/crypto/internal/poly1305"
 )

 func writeWithPadding(p *poly1305.MAC, b []byte) {
@@ -30,7 +30,7 @@ func writeUint64(p *poly1305.MAC, n int) {
 func (c *chacha20poly1305) sealGeneric(dst, nonce, plaintext, additionalData []byte) []byte {
 	ret, out := sliceForAppend(dst, len(plaintext)+poly1305.TagSize)
 	ciphertext, tag := out[:len(plaintext)], out[len(plaintext):]
-	if subtle.InexactOverlap(out, plaintext) {
+	if alias.InexactOverlap(out, plaintext) {
 		panic("chacha20poly1305: invalid buffer overlap")
 	}

@@ -66,7 +66,7 @@ func (c *chacha20poly1305) openGeneric(dst, nonce, ciphertext, additionalData []
 	writeUint64(p, len(ciphertext))

 	ret, out := sliceForAppend(dst, len(ciphertext))
-	if subtle.InexactOverlap(out, ciphertext) {
+	if alias.InexactOverlap(out, ciphertext) {
 		panic("chacha20poly1305: invalid buffer overlap")
 	}
 	if !p.Verify(tag) {
@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build !amd64 || !gc || purego
-// +build !amd64 !gc purego

 package chacha20poly1305

@@ -35,7 +35,7 @@ func (*xchacha20poly1305) NonceSize() int {
 }

 func (*xchacha20poly1305) Overhead() int {
-	return 16
+	return Overhead
 }

 func (x *xchacha20poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte {
@@ -264,36 +264,35 @@ func (s *String) ReadASN1Boolean(out *bool) bool {
 	return true
 }

-var bigIntType = reflect.TypeOf((*big.Int)(nil)).Elem()
-
 // ReadASN1Integer decodes an ASN.1 INTEGER into out and advances. If out does
-// not point to an integer or to a big.Int, it panics. It reports whether the
-// read was successful.
+// not point to an integer, to a big.Int, or to a []byte it panics. Only
+// positive and zero values can be decoded into []byte, and they are returned as
+// big-endian binary values that share memory with s. Positive values will have
+// no leading zeroes, and zero will be returned as a single zero byte.
+// ReadASN1Integer reports whether the read was successful.
 func (s *String) ReadASN1Integer(out interface{}) bool {
-	if reflect.TypeOf(out).Kind() != reflect.Ptr {
-		panic("out is not a pointer")
-	}
-	switch reflect.ValueOf(out).Elem().Kind() {
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+	switch out := out.(type) {
+	case *int, *int8, *int16, *int32, *int64:
 		var i int64
 		if !s.readASN1Int64(&i) || reflect.ValueOf(out).Elem().OverflowInt(i) {
 			return false
 		}
 		reflect.ValueOf(out).Elem().SetInt(i)
 		return true
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+	case *uint, *uint8, *uint16, *uint32, *uint64:
 		var u uint64
 		if !s.readASN1Uint64(&u) || reflect.ValueOf(out).Elem().OverflowUint(u) {
 			return false
 		}
 		reflect.ValueOf(out).Elem().SetUint(u)
 		return true
-	case reflect.Struct:
-		if reflect.TypeOf(out).Elem() == bigIntType {
-			return s.readASN1BigInt(out.(*big.Int))
-		}
+	case *big.Int:
+		return s.readASN1BigInt(out)
+	case *[]byte:
+		return s.readASN1Bytes(out)
+	default:
+		panic("out does not point to an integer type")
 	}
-	panic("out does not point to an integer type")
 }

 func checkASN1Integer(bytes []byte) bool {
@@ -333,6 +332,21 @@ func (s *String) readASN1BigInt(out *big.Int) bool {
 	return true
 }

+func (s *String) readASN1Bytes(out *[]byte) bool {
+	var bytes String
+	if !s.ReadASN1(&bytes, asn1.INTEGER) || !checkASN1Integer(bytes) {
+		return false
+	}
+	if bytes[0]&0x80 == 0x80 {
+		return false
+	}
+	for len(bytes) > 1 && bytes[0] == 0 {
+		bytes = bytes[1:]
+	}
+	*out = bytes
+	return true
+}
+
 func (s *String) readASN1Int64(out *int64) bool {
 	var bytes String
 	if !s.ReadASN1(&bytes, asn1.INTEGER) || !checkASN1Integer(bytes) || !asn1Signed(out, bytes) {
@@ -407,11 +421,24 @@ func (s *String) ReadASN1Enum(out *int) bool {
 func (s *String) readBase128Int(out *int) bool {
 	ret := 0
 	for i := 0; len(*s) > 0; i++ {
-		if i == 4 {
+		if i == 5 {
+			return false
+		}
+		// Avoid overflowing int on a 32-bit platform.
+		// We don't want different behavior based on the architecture.
+		if ret >= 1<<(31-7) {
 			return false
 		}
 		ret <<= 7
 		b := s.read(1)[0]
+
+		// ITU-T X.690, section 8.19.2:
+		// The subidentifier shall be encoded in the fewest possible octets,
+		// that is, the leading octet of the subidentifier shall not have the value 0x80.
+		if i == 0 && b == 0x80 {
+			return false
+		}
+
 		ret |= int(b & 0x7f)
 		if b&0x80 == 0 {
 			*out = ret
@@ -527,7 +554,7 @@ func (s *String) ReadASN1BitString(out *encoding_asn1.BitString) bool {
 		return false
 	}

-	paddingBits := uint8(bytes[0])
+	paddingBits := bytes[0]
 	bytes = bytes[1:]
 	if paddingBits > 7 ||
 		len(bytes) == 0 && paddingBits != 0 ||
@@ -540,7 +567,7 @@ func (s *String) ReadASN1BitString(out *encoding_asn1.BitString) bool {
 	return true
 }

-// ReadASN1BitString decodes an ASN.1 BIT STRING into out and advances. It is
+// ReadASN1BitStringAsBytes decodes an ASN.1 BIT STRING into out and advances. It is
 // an error if the BIT STRING is not a whole number of bytes. It reports
 // whether the read was successful.
 func (s *String) ReadASN1BitStringAsBytes(out *[]byte) bool {
@@ -549,7 +576,7 @@ func (s *String) ReadASN1BitStringAsBytes(out *[]byte) bool {
 		return false
 	}

-	paddingBits := uint8(bytes[0])
+	paddingBits := bytes[0]
 	if paddingBits != 0 {
 		return false
 	}
@@ -649,34 +676,27 @@ func (s *String) SkipOptionalASN1(tag asn1.Tag) bool {
 	return s.ReadASN1(&unused, tag)
 }

-// ReadOptionalASN1Integer attempts to read an optional ASN.1 INTEGER
-// explicitly tagged with tag into out and advances. If no element with a
-// matching tag is present, it writes defaultValue into out instead. If out
-// does not point to an integer or to a big.Int, it panics. It reports
-// whether the read was successful.
+// ReadOptionalASN1Integer attempts to read an optional ASN.1 INTEGER explicitly
+// tagged with tag into out and advances. If no element with a matching tag is
+// present, it writes defaultValue into out instead. Otherwise, it behaves like
+// ReadASN1Integer.
 func (s *String) ReadOptionalASN1Integer(out interface{}, tag asn1.Tag, defaultValue interface{}) bool {
-	if reflect.TypeOf(out).Kind() != reflect.Ptr {
-		panic("out is not a pointer")
-	}
 	var present bool
 	var i String
 	if !s.ReadOptionalASN1(&i, &present, tag) {
 		return false
 	}
 	if !present {
-		switch reflect.ValueOf(out).Elem().Kind() {
-		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
-			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		switch out.(type) {
+		case *int, *int8, *int16, *int32, *int64,
+			*uint, *uint8, *uint16, *uint32, *uint64, *[]byte:
 			reflect.ValueOf(out).Elem().Set(reflect.ValueOf(defaultValue))
-		case reflect.Struct:
-			if reflect.TypeOf(out).Elem() != bigIntType {
-				panic("invalid integer type")
-			}
-			if reflect.TypeOf(defaultValue).Kind() != reflect.Ptr ||
-				reflect.TypeOf(defaultValue).Elem() != bigIntType {
+		case *big.Int:
+			if defaultValue, ok := defaultValue.(*big.Int); ok {
+				out.(*big.Int).Set(defaultValue)
+			} else {
 				panic("out points to big.Int, but defaultValue does not")
 			}
-			out.(*big.Int).Set(defaultValue.(*big.Int))
 		default:
 			panic("invalid integer type")
 		}
@@ -713,13 +733,14 @@ func (s *String) ReadOptionalASN1OctetString(out *[]byte, outPresent *bool, tag
 	return true
 }

-// ReadOptionalASN1Boolean sets *out to the value of the next ASN.1 BOOLEAN or,
-// if the next bytes are not an ASN.1 BOOLEAN, to the value of defaultValue.
-// It reports whether the operation was successful.
-func (s *String) ReadOptionalASN1Boolean(out *bool, defaultValue bool) bool {
+// ReadOptionalASN1Boolean attempts to read an optional ASN.1 BOOLEAN
+// explicitly tagged with tag into out and advances. If no element with a
+// matching tag is present, it sets "out" to defaultValue instead. It reports
+// whether the read was successful.
+func (s *String) ReadOptionalASN1Boolean(out *bool, tag asn1.Tag, defaultValue bool) bool {
 	var present bool
 	var child String
-	if !s.ReadOptionalASN1(&child, &present, asn1.BOOLEAN) {
+	if !s.ReadOptionalASN1(&child, &present, tag) {
 		return false
 	}

@@ -728,7 +749,7 @@ func (s *String) ReadOptionalASN1Boolean(out *bool, defaultValue bool) bool {
 		return true
 	}

-	return s.ReadASN1Boolean(out)
+	return child.ReadASN1Boolean(out)
 }

 func (s *String) readASN1(out *String, outTag *asn1.Tag, skipHeader bool) bool {
@@ -4,7 +4,7 @@

 // Package asn1 contains supporting types for parsing and building ASN.1
 // messages with the cryptobyte package.
-package asn1 // import "golang.org/x/crypto/cryptobyte/asn1"
+package asn1

 // Tag represents an ASN.1 identifier octet, consisting of a tag number
 // (indicating a type) and class (such as context-specific or constructed).
@@ -115,6 +115,28 @@ func TestReadASN1OptionalInteger(t *testing.T) {
 	}
 }

+const defaultBool = false
+
+var optionalBoolTestData = []readASN1Test{
+	{"empty", []byte{}, 0xa0, true, false},
+	{"invalid", []byte{0xa1, 0x3, 0x1, 0x2, 0x7f}, 0xa1, false, defaultBool},
+	{"missing", []byte{0xa1, 0x3, 0x1, 0x1, 0x7f}, 0xa0, true, defaultBool},
+	{"present", []byte{0xa1, 0x3, 0x1, 0x1, 0xff}, 0xa1, true, true},
+}
+
+func TestReadASN1OptionalBoolean(t *testing.T) {
+	for _, test := range optionalBoolTestData {
+		t.Run(test.name, func(t *testing.T) {
+			in := String(test.in)
+			var out bool
+			ok := in.ReadOptionalASN1Boolean(&out, test.tag, defaultBool)
+			if ok != test.ok || ok && out != test.out.(bool) {
+				t.Errorf("in.ReadOptionalASN1Boolean() = %v, want %v; out = %v, want %v", ok, test.ok, out, test.out)
+			}
+		})
+	}
+}
+
 func TestReadASN1IntegerSigned(t *testing.T) {
 	testData64 := []struct {
 		in  []byte
@@ -154,6 +176,32 @@ func TestReadASN1IntegerSigned(t *testing.T) {
 		}
 	})

+	// Repeat the same cases, reading into a []byte.
+	t.Run("bytes", func(t *testing.T) {
+		for i, test := range testData64 {
+			in := String(test.in)
+			var out []byte
+			ok := in.ReadASN1Integer(&out)
+			if test.out < 0 {
+				if ok {
+					t.Errorf("#%d: in.ReadASN1Integer(%d) = %v, want false", i, test.out, ok)
+				}
+				continue
+			}
+			if !ok {
+				t.Errorf("#%d: in.ReadASN1Integer() = %v, want true", i, ok)
+				continue
+			}
+			n := new(big.Int).SetBytes(out).Int64()
+			if n != test.out {
+				t.Errorf("#%d: in.ReadASN1Integer() = %v, want true; out = %x, want %d", i, ok, out, test.out)
+			}
+			if out[0] == 0 && len(out) > 1 {
+				t.Errorf("#%d: in.ReadASN1Integer() = %v; out = %x, has leading zeroes", i, ok, out)
+			}
+		}
+	})
+
 	// Repeat with the implicit-tagging functions
 	t.Run("WithTag", func(t *testing.T) {
 		for i, test := range testData64 {
@@ -247,6 +295,10 @@ func TestASN1ObjectIdentifier(t *testing.T) {
 		{[]byte{6, 4, 85, 0x02, 0xc0, 0x00}, true, []int{2, 5, 2, 0x2000}},
 		{[]byte{6, 3, 0x81, 0x34, 0x03}, true, []int{2, 100, 3}},
 		{[]byte{6, 7, 85, 0x02, 0xc0, 0x80, 0x80, 0x80, 0x80}, false, []int{}},
+		{[]byte{6, 7, 85, 0x02, 0x85, 0xc7, 0xcc, 0xfb, 0x01}, true, []int{2, 5, 2, 1492336001}},
+		{[]byte{6, 7, 0x55, 0x02, 0x87, 0xff, 0xff, 0xff, 0x7f}, true, []int{2, 5, 2, 2147483647}}, // 2**31-1
+		{[]byte{6, 7, 0x55, 0x02, 0x88, 0x80, 0x80, 0x80, 0x00}, false, []int{}},                   // 2**31
+		{[]byte{6, 3, 85, 0x80, 0x02}, false, []int{}},                                             // leading 0x80 octet
 	}

 	for i, test := range testData {
@@ -95,6 +95,16 @@ func (b *Builder) AddUint32(v uint32) {
 	b.add(byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
 }

+// AddUint48 appends a big-endian, 48-bit value to the byte string.
+func (b *Builder) AddUint48(v uint64) {
+	b.add(byte(v>>40), byte(v>>32), byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
+}
+
+// AddUint64 appends a big-endian, 64-bit value to the byte string.
+func (b *Builder) AddUint64(v uint64) {
+	b.add(byte(v>>56), byte(v>>48), byte(v>>40), byte(v>>32), byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
+}
+
 // AddBytes appends a sequence of bytes to the byte string.
 func (b *Builder) AddBytes(v []byte) {
 	b.add(v...)
@@ -106,13 +116,13 @@ func (b *Builder) AddBytes(v []byte) {
 // supplied to them. The child builder passed to the continuation can be used
 // to build the content of the length-prefixed sequence. For example:
 //
-//   parent := cryptobyte.NewBuilder()
-//   parent.AddUint8LengthPrefixed(func (child *Builder) {
-//     child.AddUint8(42)
-//     child.AddUint8LengthPrefixed(func (grandchild *Builder) {
-//       grandchild.AddUint8(5)
-//     })
-//   })
+//	parent := cryptobyte.NewBuilder()
+//	parent.AddUint8LengthPrefixed(func (child *Builder) {
+//	  child.AddUint8(42)
+//	  child.AddUint8LengthPrefixed(func (grandchild *Builder) {
+//	    grandchild.AddUint8(5)
+//	  })
+//	})
 //
 // It is an error to write more bytes to the child than allowed by the reserved
 // length prefix. After the continuation returns, the child must be considered
@@ -298,9 +308,9 @@ func (b *Builder) add(bytes ...byte) {
 	b.result = append(b.result, bytes...)
 }

-// Unwrite rolls back n bytes written directly to the Builder. An attempt by a
-// child builder passed to a continuation to unwrite bytes from its parent will
-// panic.
+// Unwrite rolls back non-negative n bytes written directly to the Builder.
+// An attempt by a child builder passed to a continuation to unwrite bytes
+// from its parent will panic.
 func (b *Builder) Unwrite(n int) {
 	if b.err != nil {
 		return
@@ -312,6 +322,9 @@ func (b *Builder) Unwrite(n int) {
 	if length < 0 {
 		panic("cryptobyte: internal error")
 	}
+	if n < 0 {
+		panic("cryptobyte: attempted to unwrite negative number of bytes")
+	}
 	if n > length {
 		panic("cryptobyte: attempted to unwrite more than was written")
 	}
@@ -141,7 +141,7 @@ func TestUint24(t *testing.T) {
 	var s String = b.BytesOrPanic()
 	var v uint32
 	if !s.ReadUint24(&v) {
-		t.Error("ReadUint8() = false, want true")
+		t.Error("ReadUint24() = false, want true")
 	}
 	if v != 0xfffefd {
 		t.Errorf("v = %d, want fffefd", v)
@@ -169,7 +169,7 @@ func TestUint32(t *testing.T) {
 	var s String = b.BytesOrPanic()
 	var v uint32
 	if !s.ReadUint32(&v) {
-		t.Error("ReadUint8() = false, want true")
+		t.Error("ReadUint32() = false, want true")
 	}
 	if v != 0xfffefdfc {
 		t.Errorf("v = %x, want fffefdfc", v)
@@ -179,6 +179,47 @@ func TestUint32(t *testing.T) {
 	}
 }

+func TestUint48(t *testing.T) {
+	var b Builder
+	var u uint64 = 0xfefcff3cfdfc
+	b.AddUint48(u)
+	if err := builderBytesEq(&b, 254, 252, 255, 60, 253, 252); err != nil {
+		t.Error(err)
+	}
+
+	var s String = b.BytesOrPanic()
+	var v uint64
+	if !s.ReadUint48(&v) {
+		t.Error("ReadUint48() = false, want true")
+	}
+	if v != u {
+		t.Errorf("v = %x, want %x", v, u)
+	}
+	if len(s) != 0 {
+		t.Errorf("len(s) = %d, want 0", len(s))
+	}
+}
+
+func TestUint64(t *testing.T) {
+	var b Builder
+	b.AddUint64(0xf2fefefcff3cfdfc)
+	if err := builderBytesEq(&b, 242, 254, 254, 252, 255, 60, 253, 252); err != nil {
+		t.Error(err)
+	}
+
+	var s String = b.BytesOrPanic()
+	var v uint64
+	if !s.ReadUint64(&v) {
+		t.Error("ReadUint64() = false, want true")
+	}
+	if v != 0xf2fefefcff3cfdfc {
+		t.Errorf("v = %x, want f2fefefcff3cfdfc", v)
+	}
+	if len(s) != 0 {
+		t.Errorf("len(s) = %d, want 0", len(s))
+	}
+}
+
 func TestUMultiple(t *testing.T) {
 	var b Builder
 	b.AddUint8(23)
@@ -15,7 +15,7 @@
 //
 // See the documentation and examples for the Builder and String types to get
 // started.
-package cryptobyte // import "golang.org/x/crypto/cryptobyte"
+package cryptobyte

 // String represents a string of bytes. It provides methods for parsing
 // fixed-length and length-prefixed values from it.
@@ -81,6 +81,28 @@ func (s *String) ReadUint32(out *uint32) bool {
 	return true
 }

+// ReadUint48 decodes a big-endian, 48-bit value into out and advances over it.
+// It reports whether the read was successful.
+func (s *String) ReadUint48(out *uint64) bool {
+	v := s.read(6)
+	if v == nil {
+		return false
+	}
+	*out = uint64(v[0])<<40 | uint64(v[1])<<32 | uint64(v[2])<<24 | uint64(v[3])<<16 | uint64(v[4])<<8 | uint64(v[5])
+	return true
+}
+
+// ReadUint64 decodes a big-endian, 64-bit value into out and advances over it.
+// It reports whether the read was successful.
+func (s *String) ReadUint64(out *uint64) bool {
+	v := s.read(8)
+	if v == nil {
+		return false
+	}
+	*out = uint64(v[0])<<56 | uint64(v[1])<<48 | uint64(v[2])<<40 | uint64(v[3])<<32 | uint64(v[4])<<24 | uint64(v[5])<<16 | uint64(v[6])<<8 | uint64(v[7])
+	return true
+}
+
 func (s *String) readUnsigned(out *uint32, length int) bool {
 	v := s.read(length)
 	if v == nil {
@@ -5,12 +5,12 @@
 // Package curve25519 provides an implementation of the X25519 function, which
 // performs scalar multiplication on the elliptic curve known as Curve25519.
 // See RFC 7748.
-package curve25519 // import "golang.org/x/crypto/curve25519"
+//
+// This package is a wrapper for the X25519 implementation
+// in the crypto/ecdh package.
+package curve25519

-import (
-	"crypto/subtle"
-	"fmt"
-)
+import "crypto/ecdh"

 // ScalarMult sets dst to the product scalar * point.
 //
@@ -18,7 +18,13 @@ import (
 // zeroes, irrespective of the scalar. Instead, use the X25519 function, which
 // will return an error.
 func ScalarMult(dst, scalar, point *[32]byte) {
-	scalarMult(dst, scalar, point)
+	if _, err := x25519(dst, scalar[:], point[:]); err != nil {
+		// The only error condition for x25519 when the inputs are 32 bytes long
+		// is if the output would have been the all-zero value.
+		for i := range dst {
+			dst[i] = 0
+		}
+	}
 }

 // ScalarBaseMult sets dst to the product scalar * base where base is the
@@ -27,7 +33,12 @@ func ScalarMult(dst, scalar, point *[32]byte) {
 // It is recommended to use the X25519 function with Basepoint instead, as
 // copying into fixed size arrays can lead to unexpected bugs.
 func ScalarBaseMult(dst, scalar *[32]byte) {
-	ScalarMult(dst, scalar, &basePoint)
+	curve := ecdh.X25519()
+	priv, err := curve.NewPrivateKey(scalar[:])
+	if err != nil {
+		panic("curve25519: internal error: scalarBaseMult was not 32 bytes")
+	}
+	copy(dst[:], priv.PublicKey().Bytes())
 }

 const (
@@ -40,21 +51,10 @@ const (
 // Basepoint is the canonical Curve25519 generator.
 var Basepoint []byte

-var basePoint = [32]byte{9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+var basePoint = [32]byte{9}

 func init() { Basepoint = basePoint[:] }

-func checkBasepoint() {
-	if subtle.ConstantTimeCompare(Basepoint, []byte{
-		0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	}) != 1 {
-		panic("curve25519: global Basepoint value was modified")
-	}
-}
-
 // X25519 returns the result of the scalar multiplication (scalar * point),
 // according to RFC 7748, Section 5. scalar, point and the return value are
 // slices of 32 bytes.
@@ -72,24 +72,19 @@ func X25519(scalar, point []byte) ([]byte, error) {
 }

 func x25519(dst *[32]byte, scalar, point []byte) ([]byte, error) {
-	var in [32]byte
-	if l := len(scalar); l != 32 {
-		return nil, fmt.Errorf("bad scalar length: %d, expected %d", l, 32)
+	curve := ecdh.X25519()
+	pub, err := curve.NewPublicKey(point)
+	if err != nil {
+		return nil, err
 	}
-	if l := len(point); l != 32 {
-		return nil, fmt.Errorf("bad point length: %d, expected %d", l, 32)
+	priv, err := curve.NewPrivateKey(scalar)
+	if err != nil {
+		return nil, err
 	}
-	copy(in[:], scalar)
-	if &point[0] == &Basepoint[0] {
-		checkBasepoint()
-		ScalarBaseMult(dst, &in)
-	} else {
-		var base, zero [32]byte
-		copy(base[:], point)
-		ScalarMult(dst, &in, &base)
-		if subtle.ConstantTimeCompare(dst[:], zero[:]) == 1 {
-			return nil, fmt.Errorf("bad input point: low order point")
-		}
+	out, err := priv.ECDH(pub)
+	if err != nil {
+		return nil, err
 	}
+	copy(dst[:], out)
 	return dst[:], nil
 }
@@ -1,241 +0,0 @@
-// Copyright 2012 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build amd64 && gc && !purego
-// +build amd64,gc,!purego
-
-package curve25519
-
-// These functions are implemented in the .s files. The names of the functions
-// in the rest of the file are also taken from the SUPERCOP sources to help
-// people following along.
-
-//go:noescape
-
-func cswap(inout *[5]uint64, v uint64)
-
-//go:noescape
-
-func ladderstep(inout *[5][5]uint64)
-
-//go:noescape
-
-func freeze(inout *[5]uint64)
-
-//go:noescape
-
-func mul(dest, a, b *[5]uint64)
-
-//go:noescape
-
-func square(out, in *[5]uint64)
-
-// mladder uses a Montgomery ladder to calculate (xr/zr) *= s.
-func mladder(xr, zr *[5]uint64, s *[32]byte) {
-	var work [5][5]uint64
-
-	work[0] = *xr
-	setint(&work[1], 1)
-	setint(&work[2], 0)
-	work[3] = *xr
-	setint(&work[4], 1)
-
-	j := uint(6)
-	var prevbit byte
-
-	for i := 31; i >= 0; i-- {
-		for j < 8 {
-			bit := ((*s)[i] >> j) & 1
-			swap := bit ^ prevbit
-			prevbit = bit
-			cswap(&work[1], uint64(swap))
-			ladderstep(&work)
-			j--
-		}
-		j = 7
-	}
-
-	*xr = work[1]
-	*zr = work[2]
-}
-
-func scalarMult(out, in, base *[32]byte) {
-	var e [32]byte
-	copy(e[:], (*in)[:])
-	e[0] &= 248
-	e[31] &= 127
-	e[31] |= 64
-
-	var t, z [5]uint64
-	unpack(&t, base)
-	mladder(&t, &z, &e)
-	invert(&z, &z)
-	mul(&t, &t, &z)
-	pack(out, &t)
-}
-
-func setint(r *[5]uint64, v uint64) {
-	r[0] = v
-	r[1] = 0
-	r[2] = 0
-	r[3] = 0
-	r[4] = 0
-}
-
-// unpack sets r = x where r consists of 5, 51-bit limbs in little-endian
-// order.
-func unpack(r *[5]uint64, x *[32]byte) {
-	r[0] = uint64(x[0]) |
-		uint64(x[1])<<8 |
-		uint64(x[2])<<16 |
-		uint64(x[3])<<24 |
-		uint64(x[4])<<32 |
-		uint64(x[5])<<40 |
-		uint64(x[6]&7)<<48
-
-	r[1] = uint64(x[6])>>3 |
-		uint64(x[7])<<5 |
-		uint64(x[8])<<13 |
-		uint64(x[9])<<21 |
-		uint64(x[10])<<29 |
-		uint64(x[11])<<37 |
-		uint64(x[12]&63)<<45
-
-	r[2] = uint64(x[12])>>6 |
-		uint64(x[13])<<2 |
-		uint64(x[14])<<10 |
-		uint64(x[15])<<18 |
-		uint64(x[16])<<26 |
-		uint64(x[17])<<34 |
-		uint64(x[18])<<42 |
-		uint64(x[19]&1)<<50
-
-	r[3] = uint64(x[19])>>1 |
-		uint64(x[20])<<7 |
-		uint64(x[21])<<15 |
-		uint64(x[22])<<23 |
-		uint64(x[23])<<31 |
-		uint64(x[24])<<39 |
-		uint64(x[25]&15)<<47
-
-	r[4] = uint64(x[25])>>4 |
-		uint64(x[26])<<4 |
-		uint64(x[27])<<12 |
-		uint64(x[28])<<20 |
-		uint64(x[29])<<28 |
-		uint64(x[30])<<36 |
-		uint64(x[31]&127)<<44
-}
-
-// pack sets out = x where out is the usual, little-endian form of the 5,
-// 51-bit limbs in x.
-func pack(out *[32]byte, x *[5]uint64) {
-	t := *x
-	freeze(&t)
-
-	out[0] = byte(t[0])
-	out[1] = byte(t[0] >> 8)
-	out[2] = byte(t[0] >> 16)
-	out[3] = byte(t[0] >> 24)
-	out[4] = byte(t[0] >> 32)
-	out[5] = byte(t[0] >> 40)
-	out[6] = byte(t[0] >> 48)
-
-	out[6] ^= byte(t[1]<<3) & 0xf8
-	out[7] = byte(t[1] >> 5)
-	out[8] = byte(t[1] >> 13)
-	out[9] = byte(t[1] >> 21)
-	out[10] = byte(t[1] >> 29)
-	out[11] = byte(t[1] >> 37)
-	out[12] = byte(t[1] >> 45)
-
-	out[12] ^= byte(t[2]<<6) & 0xc0
-	out[13] = byte(t[2] >> 2)
-	out[14] = byte(t[2] >> 10)
-	out[15] = byte(t[2] >> 18)
-	out[16] = byte(t[2] >> 26)
-	out[17] = byte(t[2] >> 34)
-	out[18] = byte(t[2] >> 42)
-	out[19] = byte(t[2] >> 50)
-
-	out[19] ^= byte(t[3]<<1) & 0xfe
-	out[20] = byte(t[3] >> 7)
-	out[21] = byte(t[3] >> 15)
-	out[22] = byte(t[3] >> 23)
-	out[23] = byte(t[3] >> 31)
-	out[24] = byte(t[3] >> 39)
-	out[25] = byte(t[3] >> 47)
-
-	out[25] ^= byte(t[4]<<4) & 0xf0
-	out[26] = byte(t[4] >> 4)
-	out[27] = byte(t[4] >> 12)
-	out[28] = byte(t[4] >> 20)
-	out[29] = byte(t[4] >> 28)
-	out[30] = byte(t[4] >> 36)
-	out[31] = byte(t[4] >> 44)
-}
-
-// invert calculates r = x^-1 mod p using Fermat's little theorem.
-func invert(r *[5]uint64, x *[5]uint64) {
-	var z2, z9, z11, z2_5_0, z2_10_0, z2_20_0, z2_50_0, z2_100_0, t [5]uint64
-
-	square(&z2, x)        /* 2 */
-	square(&t, &z2)       /* 4 */
-	square(&t, &t)        /* 8 */
-	mul(&z9, &t, x)       /* 9 */
-	mul(&z11, &z9, &z2)   /* 11 */
-	square(&t, &z11)      /* 22 */
-	mul(&z2_5_0, &t, &z9) /* 2^5 - 2^0 = 31 */
-
-	square(&t, &z2_5_0)      /* 2^6 - 2^1 */
-	for i := 1; i < 5; i++ { /* 2^20 - 2^10 */
-		square(&t, &t)
-	}
-	mul(&z2_10_0, &t, &z2_5_0) /* 2^10 - 2^0 */
-
-	square(&t, &z2_10_0)      /* 2^11 - 2^1 */
-	for i := 1; i < 10; i++ { /* 2^20 - 2^10 */
-		square(&t, &t)
-	}
-	mul(&z2_20_0, &t, &z2_10_0) /* 2^20 - 2^0 */
-
-	square(&t, &z2_20_0)      /* 2^21 - 2^1 */
-	for i := 1; i < 20; i++ { /* 2^40 - 2^20 */
-		square(&t, &t)
-	}
-	mul(&t, &t, &z2_20_0) /* 2^40 - 2^0 */
-
-	square(&t, &t)            /* 2^41 - 2^1 */
-	for i := 1; i < 10; i++ { /* 2^50 - 2^10 */
-		square(&t, &t)
-	}
-	mul(&z2_50_0, &t, &z2_10_0) /* 2^50 - 2^0 */
-
-	square(&t, &z2_50_0)      /* 2^51 - 2^1 */
-	for i := 1; i < 50; i++ { /* 2^100 - 2^50 */
-		square(&t, &t)
-	}
-	mul(&z2_100_0, &t, &z2_50_0) /* 2^100 - 2^0 */
-
-	square(&t, &z2_100_0)      /* 2^101 - 2^1 */
-	for i := 1; i < 100; i++ { /* 2^200 - 2^100 */
-		square(&t, &t)
-	}
-	mul(&t, &t, &z2_100_0) /* 2^200 - 2^0 */
-
-	square(&t, &t)            /* 2^201 - 2^1 */
-	for i := 1; i < 50; i++ { /* 2^250 - 2^50 */
-		square(&t, &t)
-	}
-	mul(&t, &t, &z2_50_0) /* 2^250 - 2^0 */
-
-	square(&t, &t) /* 2^251 - 2^1 */
-	square(&t, &t) /* 2^252 - 2^2 */
-	square(&t, &t) /* 2^253 - 2^3 */
-
-	square(&t, &t) /* 2^254 - 2^4 */
-
-	square(&t, &t)   /* 2^255 - 2^5 */
-	mul(r, &t, &z11) /* 2^255 - 21 */
-}
@@ -1,828 +0,0 @@
-// Copyright 2013 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package curve25519
-
-import "encoding/binary"
-
-// This code is a port of the public domain, "ref10" implementation of
-// curve25519 from SUPERCOP 20130419 by D. J. Bernstein.
-
-// fieldElement represents an element of the field GF(2^255 - 19). An element
-// t, entries t[0]...t[9], represents the integer t[0]+2^26 t[1]+2^51 t[2]+2^77
-// t[3]+2^102 t[4]+...+2^230 t[9]. Bounds on each t[i] vary depending on
-// context.
-type fieldElement [10]int32
-
-func feZero(fe *fieldElement) {
-	for i := range fe {
-		fe[i] = 0
-	}
-}
-
-func feOne(fe *fieldElement) {
-	feZero(fe)
-	fe[0] = 1
-}
-
-func feAdd(dst, a, b *fieldElement) {
-	for i := range dst {
-		dst[i] = a[i] + b[i]
-	}
-}
-
-func feSub(dst, a, b *fieldElement) {
-	for i := range dst {
-		dst[i] = a[i] - b[i]
-	}
-}
-
-func feCopy(dst, src *fieldElement) {
-	for i := range dst {
-		dst[i] = src[i]
-	}
-}
-
-// feCSwap replaces (f,g) with (g,f) if b == 1; replaces (f,g) with (f,g) if b == 0.
-//
-// Preconditions: b in {0,1}.
-func feCSwap(f, g *fieldElement, b int32) {
-	b = -b
-	for i := range f {
-		t := b & (f[i] ^ g[i])
-		f[i] ^= t
-		g[i] ^= t
-	}
-}
-
-// load3 reads a 24-bit, little-endian value from in.
-func load3(in []byte) int64 {
-	var r int64
-	r = int64(in[0])
-	r |= int64(in[1]) << 8
-	r |= int64(in[2]) << 16
-	return r
-}
-
-// load4 reads a 32-bit, little-endian value from in.
-func load4(in []byte) int64 {
-	return int64(binary.LittleEndian.Uint32(in))
-}
-
-func feFromBytes(dst *fieldElement, src *[32]byte) {
-	h0 := load4(src[:])
-	h1 := load3(src[4:]) << 6
-	h2 := load3(src[7:]) << 5
-	h3 := load3(src[10:]) << 3
-	h4 := load3(src[13:]) << 2
-	h5 := load4(src[16:])
-	h6 := load3(src[20:]) << 7
-	h7 := load3(src[23:]) << 5
-	h8 := load3(src[26:]) << 4
-	h9 := (load3(src[29:]) & 0x7fffff) << 2
-
-	var carry [10]int64
-	carry[9] = (h9 + 1<<24) >> 25
-	h0 += carry[9] * 19
-	h9 -= carry[9] << 25
-	carry[1] = (h1 + 1<<24) >> 25
-	h2 += carry[1]
-	h1 -= carry[1] << 25
-	carry[3] = (h3 + 1<<24) >> 25
-	h4 += carry[3]
-	h3 -= carry[3] << 25
-	carry[5] = (h5 + 1<<24) >> 25
-	h6 += carry[5]
-	h5 -= carry[5] << 25
-	carry[7] = (h7 + 1<<24) >> 25
-	h8 += carry[7]
-	h7 -= carry[7] << 25
-
-	carry[0] = (h0 + 1<<25) >> 26
-	h1 += carry[0]
-	h0 -= carry[0] << 26
-	carry[2] = (h2 + 1<<25) >> 26
-	h3 += carry[2]
-	h2 -= carry[2] << 26
-	carry[4] = (h4 + 1<<25) >> 26
-	h5 += carry[4]
-	h4 -= carry[4] << 26
-	carry[6] = (h6 + 1<<25) >> 26
-	h7 += carry[6]
-	h6 -= carry[6] << 26
-	carry[8] = (h8 + 1<<25) >> 26
-	h9 += carry[8]
-	h8 -= carry[8] << 26
-
-	dst[0] = int32(h0)
-	dst[1] = int32(h1)
-	dst[2] = int32(h2)
-	dst[3] = int32(h3)
-	dst[4] = int32(h4)
-	dst[5] = int32(h5)
-	dst[6] = int32(h6)
-	dst[7] = int32(h7)
-	dst[8] = int32(h8)
-	dst[9] = int32(h9)
-}
-
-// feToBytes marshals h to s.
-// Preconditions:
-//   |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
-//
-// Write p=2^255-19; q=floor(h/p).
-// Basic claim: q = floor(2^(-255)(h + 19 2^(-25)h9 + 2^(-1))).
-//
-// Proof:
-//   Have |h|<=p so |q|<=1 so |19^2 2^(-255) q|<1/4.
-//   Also have |h-2^230 h9|<2^230 so |19 2^(-255)(h-2^230 h9)|<1/4.
-//
-//   Write y=2^(-1)-19^2 2^(-255)q-19 2^(-255)(h-2^230 h9).
-//   Then 0<y<1.
-//
-//   Write r=h-pq.
-//   Have 0<=r<=p-1=2^255-20.
-//   Thus 0<=r+19(2^-255)r<r+19(2^-255)2^255<=2^255-1.
-//
-//   Write x=r+19(2^-255)r+y.
-//   Then 0<x<2^255 so floor(2^(-255)x) = 0 so floor(q+2^(-255)x) = q.
-//
-//   Have q+2^(-255)x = 2^(-255)(h + 19 2^(-25) h9 + 2^(-1))
-//   so floor(2^(-255)(h + 19 2^(-25) h9 + 2^(-1))) = q.
-func feToBytes(s *[32]byte, h *fieldElement) {
-	var carry [10]int32
-
-	q := (19*h[9] + (1 << 24)) >> 25
-	q = (h[0] + q) >> 26
-	q = (h[1] + q) >> 25
-	q = (h[2] + q) >> 26
-	q = (h[3] + q) >> 25
-	q = (h[4] + q) >> 26
-	q = (h[5] + q) >> 25
-	q = (h[6] + q) >> 26
-	q = (h[7] + q) >> 25
-	q = (h[8] + q) >> 26
-	q = (h[9] + q) >> 25
-
-	// Goal: Output h-(2^255-19)q, which is between 0 and 2^255-20.
-	h[0] += 19 * q
-	// Goal: Output h-2^255 q, which is between 0 and 2^255-20.
-
-	carry[0] = h[0] >> 26
-	h[1] += carry[0]
-	h[0] -= carry[0] << 26
-	carry[1] = h[1] >> 25
-	h[2] += carry[1]
-	h[1] -= carry[1] << 25
-	carry[2] = h[2] >> 26
-	h[3] += carry[2]
-	h[2] -= carry[2] << 26
-	carry[3] = h[3] >> 25
-	h[4] += carry[3]
-	h[3] -= carry[3] << 25
-	carry[4] = h[4] >> 26
-	h[5] += carry[4]
-	h[4] -= carry[4] << 26
-	carry[5] = h[5] >> 25
-	h[6] += carry[5]
-	h[5] -= carry[5] << 25
-	carry[6] = h[6] >> 26
-	h[7] += carry[6]
-	h[6] -= carry[6] << 26
-	carry[7] = h[7] >> 25
-	h[8] += carry[7]
-	h[7] -= carry[7] << 25
-	carry[8] = h[8] >> 26
-	h[9] += carry[8]
-	h[8] -= carry[8] << 26
-	carry[9] = h[9] >> 25
-	h[9] -= carry[9] << 25
-	// h10 = carry9
-
-	// Goal: Output h[0]+...+2^255 h10-2^255 q, which is between 0 and 2^255-20.
-	// Have h[0]+...+2^230 h[9] between 0 and 2^255-1;
-	// evidently 2^255 h10-2^255 q = 0.
-	// Goal: Output h[0]+...+2^230 h[9].
-
-	s[0] = byte(h[0] >> 0)
-	s[1] = byte(h[0] >> 8)
-	s[2] = byte(h[0] >> 16)
-	s[3] = byte((h[0] >> 24) | (h[1] << 2))
-	s[4] = byte(h[1] >> 6)
-	s[5] = byte(h[1] >> 14)
-	s[6] = byte((h[1] >> 22) | (h[2] << 3))
-	s[7] = byte(h[2] >> 5)
-	s[8] = byte(h[2] >> 13)
-	s[9] = byte((h[2] >> 21) | (h[3] << 5))
-	s[10] = byte(h[3] >> 3)
-	s[11] = byte(h[3] >> 11)
-	s[12] = byte((h[3] >> 19) | (h[4] << 6))
-	s[13] = byte(h[4] >> 2)
-	s[14] = byte(h[4] >> 10)
-	s[15] = byte(h[4] >> 18)
-	s[16] = byte(h[5] >> 0)
-	s[17] = byte(h[5] >> 8)
-	s[18] = byte(h[5] >> 16)
-	s[19] = byte((h[5] >> 24) | (h[6] << 1))
-	s[20] = byte(h[6] >> 7)
-	s[21] = byte(h[6] >> 15)
-	s[22] = byte((h[6] >> 23) | (h[7] << 3))
-	s[23] = byte(h[7] >> 5)
-	s[24] = byte(h[7] >> 13)
-	s[25] = byte((h[7] >> 21) | (h[8] << 4))
-	s[26] = byte(h[8] >> 4)
-	s[27] = byte(h[8] >> 12)
-	s[28] = byte((h[8] >> 20) | (h[9] << 6))
-	s[29] = byte(h[9] >> 2)
-	s[30] = byte(h[9] >> 10)
-	s[31] = byte(h[9] >> 18)
-}
-
-// feMul calculates h = f * g
-// Can overlap h with f or g.
-//
-// Preconditions:
-//    |f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
-//    |g| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
-//
-// Postconditions:
-//    |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
-//
-// Notes on implementation strategy:
-//
-// Using schoolbook multiplication.
-// Karatsuba would save a little in some cost models.
-//
-// Most multiplications by 2 and 19 are 32-bit precomputations;
-// cheaper than 64-bit postcomputations.
-//
-// There is one remaining multiplication by 19 in the carry chain;
-// one *19 precomputation can be merged into this,
-// but the resulting data flow is considerably less clean.
-//
-// There are 12 carries below.
-// 10 of them are 2-way parallelizable and vectorizable.
-// Can get away with 11 carries, but then data flow is much deeper.
-//
-// With tighter constraints on inputs can squeeze carries into int32.
-func feMul(h, f, g *fieldElement) {
-	f0 := f[0]
-	f1 := f[1]
-	f2 := f[2]
-	f3 := f[3]
-	f4 := f[4]
-	f5 := f[5]
-	f6 := f[6]
-	f7 := f[7]
-	f8 := f[8]
-	f9 := f[9]
-	g0 := g[0]
-	g1 := g[1]
-	g2 := g[2]
-	g3 := g[3]
-	g4 := g[4]
-	g5 := g[5]
-	g6 := g[6]
-	g7 := g[7]
-	g8 := g[8]
-	g9 := g[9]
-	g1_19 := 19 * g1 // 1.4*2^29
-	g2_19 := 19 * g2 // 1.4*2^30; still ok
-	g3_19 := 19 * g3
-	g4_19 := 19 * g4
-	g5_19 := 19 * g5
-	g6_19 := 19 * g6
-	g7_19 := 19 * g7
-	g8_19 := 19 * g8
-	g9_19 := 19 * g9
-	f1_2 := 2 * f1
-	f3_2 := 2 * f3
-	f5_2 := 2 * f5
-	f7_2 := 2 * f7
-	f9_2 := 2 * f9
-	f0g0 := int64(f0) * int64(g0)
-	f0g1 := int64(f0) * int64(g1)
-	f0g2 := int64(f0) * int64(g2)
-	f0g3 := int64(f0) * int64(g3)
-	f0g4 := int64(f0) * int64(g4)
-	f0g5 := int64(f0) * int64(g5)
-	f0g6 := int64(f0) * int64(g6)
-	f0g7 := int64(f0) * int64(g7)
-	f0g8 := int64(f0) * int64(g8)
-	f0g9 := int64(f0) * int64(g9)
-	f1g0 := int64(f1) * int64(g0)
-	f1g1_2 := int64(f1_2) * int64(g1)
-	f1g2 := int64(f1) * int64(g2)
-	f1g3_2 := int64(f1_2) * int64(g3)
-	f1g4 := int64(f1) * int64(g4)
-	f1g5_2 := int64(f1_2) * int64(g5)
-	f1g6 := int64(f1) * int64(g6)
-	f1g7_2 := int64(f1_2) * int64(g7)
-	f1g8 := int64(f1) * int64(g8)
-	f1g9_38 := int64(f1_2) * int64(g9_19)
-	f2g0 := int64(f2) * int64(g0)
-	f2g1 := int64(f2) * int64(g1)
-	f2g2 := int64(f2) * int64(g2)
-	f2g3 := int64(f2) * int64(g3)
-	f2g4 := int64(f2) * int64(g4)
-	f2g5 := int64(f2) * int64(g5)
-	f2g6 := int64(f2) * int64(g6)
-	f2g7 := int64(f2) * int64(g7)
-	f2g8_19 := int64(f2) * int64(g8_19)
-	f2g9_19 := int64(f2) * int64(g9_19)
-	f3g0 := int64(f3) * int64(g0)
-	f3g1_2 := int64(f3_2) * int64(g1)
-	f3g2 := int64(f3) * int64(g2)
-	f3g3_2 := int64(f3_2) * int64(g3)
-	f3g4 := int64(f3) * int64(g4)
-	f3g5_2 := int64(f3_2) * int64(g5)
-	f3g6 := int64(f3) * int64(g6)
-	f3g7_38 := int64(f3_2) * int64(g7_19)
-	f3g8_19 := int64(f3) * int64(g8_19)
-	f3g9_38 := int64(f3_2) * int64(g9_19)
-	f4g0 := int64(f4) * int64(g0)
-	f4g1 := int64(f4) * int64(g1)
-	f4g2 := int64(f4) * int64(g2)
-	f4g3 := int64(f4) * int64(g3)
-	f4g4 := int64(f4) * int64(g4)
-	f4g5 := int64(f4) * int64(g5)
-	f4g6_19 := int64(f4) * int64(g6_19)
-	f4g7_19 := int64(f4) * int64(g7_19)
-	f4g8_19 := int64(f4) * int64(g8_19)
-	f4g9_19 := int64(f4) * int64(g9_19)
-	f5g0 := int64(f5) * int64(g0)
-	f5g1_2 := int64(f5_2) * int64(g1)
-	f5g2 := int64(f5) * int64(g2)
-	f5g3_2 := int64(f5_2) * int64(g3)
-	f5g4 := int64(f5) * int64(g4)
-	f5g5_38 := int64(f5_2) * int64(g5_19)
-	f5g6_19 := int64(f5) * int64(g6_19)
-	f5g7_38 := int64(f5_2) * int64(g7_19)
-	f5g8_19 := int64(f5) * int64(g8_19)
-	f5g9_38 := int64(f5_2) * int64(g9_19)
-	f6g0 := int64(f6) * int64(g0)
-	f6g1 := int64(f6) * int64(g1)
-	f6g2 := int64(f6) * int64(g2)
-	f6g3 := int64(f6) * int64(g3)
-	f6g4_19 := int64(f6) * int64(g4_19)
-	f6g5_19 := int64(f6) * int64(g5_19)
-	f6g6_19 := int64(f6) * int64(g6_19)
-	f6g7_19 := int64(f6) * int64(g7_19)
-	f6g8_19 := int64(f6) * int64(g8_19)
-	f6g9_19 := int64(f6) * int64(g9_19)
-	f7g0 := int64(f7) * int64(g0)
-	f7g1_2 := int64(f7_2) * int64(g1)
-	f7g2 := int64(f7) * int64(g2)
-	f7g3_38 := int64(f7_2) * int64(g3_19)
-	f7g4_19 := int64(f7) * int64(g4_19)
-	f7g5_38 := int64(f7_2) * int64(g5_19)
-	f7g6_19 := int64(f7) * int64(g6_19)
-	f7g7_38 := int64(f7_2) * int64(g7_19)
-	f7g8_19 := int64(f7) * int64(g8_19)
-	f7g9_38 := int64(f7_2) * int64(g9_19)
-	f8g0 := int64(f8) * int64(g0)
-	f8g1 := int64(f8) * int64(g1)
-	f8g2_19 := int64(f8) * int64(g2_19)
-	f8g3_19 := int64(f8) * int64(g3_19)
-	f8g4_19 := int64(f8) * int64(g4_19)
-	f8g5_19 := int64(f8) * int64(g5_19)
-	f8g6_19 := int64(f8) * int64(g6_19)
-	f8g7_19 := int64(f8) * int64(g7_19)
-	f8g8_19 := int64(f8) * int64(g8_19)
-	f8g9_19 := int64(f8) * int64(g9_19)
-	f9g0 := int64(f9) * int64(g0)
-	f9g1_38 := int64(f9_2) * int64(g1_19)
-	f9g2_19 := int64(f9) * int64(g2_19)
-	f9g3_38 := int64(f9_2) * int64(g3_19)
-	f9g4_19 := int64(f9) * int64(g4_19)
-	f9g5_38 := int64(f9_2) * int64(g5_19)
-	f9g6_19 := int64(f9) * int64(g6_19)
-	f9g7_38 := int64(f9_2) * int64(g7_19)
-	f9g8_19 := int64(f9) * int64(g8_19)
-	f9g9_38 := int64(f9_2) * int64(g9_19)
-	h0 := f0g0 + f1g9_38 + f2g8_19 + f3g7_38 + f4g6_19 + f5g5_38 + f6g4_19 + f7g3_38 + f8g2_19 + f9g1_38
-	h1 := f0g1 + f1g0 + f2g9_19 + f3g8_19 + f4g7_19 + f5g6_19 + f6g5_19 + f7g4_19 + f8g3_19 + f9g2_19
-	h2 := f0g2 + f1g1_2 + f2g0 + f3g9_38 + f4g8_19 + f5g7_38 + f6g6_19 + f7g5_38 + f8g4_19 + f9g3_38
-	h3 := f0g3 + f1g2 + f2g1 + f3g0 + f4g9_19 + f5g8_19 + f6g7_19 + f7g6_19 + f8g5_19 + f9g4_19
-	h4 := f0g4 + f1g3_2 + f2g2 + f3g1_2 + f4g0 + f5g9_38 + f6g8_19 + f7g7_38 + f8g6_19 + f9g5_38
-	h5 := f0g5 + f1g4 + f2g3 + f3g2 + f4g1 + f5g0 + f6g9_19 + f7g8_19 + f8g7_19 + f9g6_19
-	h6 := f0g6 + f1g5_2 + f2g4 + f3g3_2 + f4g2 + f5g1_2 + f6g0 + f7g9_38 + f8g8_19 + f9g7_38
-	h7 := f0g7 + f1g6 + f2g5 + f3g4 + f4g3 + f5g2 + f6g1 + f7g0 + f8g9_19 + f9g8_19
-	h8 := f0g8 + f1g7_2 + f2g6 + f3g5_2 + f4g4 + f5g3_2 + f6g2 + f7g1_2 + f8g0 + f9g9_38
-	h9 := f0g9 + f1g8 + f2g7 + f3g6 + f4g5 + f5g4 + f6g3 + f7g2 + f8g1 + f9g0
-	var carry [10]int64
-
-	// |h0| <= (1.1*1.1*2^52*(1+19+19+19+19)+1.1*1.1*2^50*(38+38+38+38+38))
-	//   i.e. |h0| <= 1.2*2^59; narrower ranges for h2, h4, h6, h8
-	// |h1| <= (1.1*1.1*2^51*(1+1+19+19+19+19+19+19+19+19))
-	//   i.e. |h1| <= 1.5*2^58; narrower ranges for h3, h5, h7, h9
-
-	carry[0] = (h0 + (1 << 25)) >> 26
-	h1 += carry[0]
-	h0 -= carry[0] << 26
-	carry[4] = (h4 + (1 << 25)) >> 26
-	h5 += carry[4]
-	h4 -= carry[4] << 26
-	// |h0| <= 2^25
-	// |h4| <= 2^25
-	// |h1| <= 1.51*2^58
-	// |h5| <= 1.51*2^58
-
-	carry[1] = (h1 + (1 << 24)) >> 25
-	h2 += carry[1]
-	h1 -= carry[1] << 25
-	carry[5] = (h5 + (1 << 24)) >> 25
-	h6 += carry[5]
-	h5 -= carry[5] << 25
-	// |h1| <= 2^24; from now on fits into int32
-	// |h5| <= 2^24; from now on fits into int32
-	// |h2| <= 1.21*2^59
-	// |h6| <= 1.21*2^59
-
-	carry[2] = (h2 + (1 << 25)) >> 26
-	h3 += carry[2]
-	h2 -= carry[2] << 26
-	carry[6] = (h6 + (1 << 25)) >> 26
-	h7 += carry[6]
-	h6 -= carry[6] << 26
-	// |h2| <= 2^25; from now on fits into int32 unchanged
-	// |h6| <= 2^25; from now on fits into int32 unchanged
-	// |h3| <= 1.51*2^58
-	// |h7| <= 1.51*2^58
-
-	carry[3] = (h3 + (1 << 24)) >> 25
-	h4 += carry[3]
-	h3 -= carry[3] << 25
-	carry[7] = (h7 + (1 << 24)) >> 25
-	h8 += carry[7]
-	h7 -= carry[7] << 25
-	// |h3| <= 2^24; from now on fits into int32 unchanged
-	// |h7| <= 2^24; from now on fits into int32 unchanged
-	// |h4| <= 1.52*2^33
-	// |h8| <= 1.52*2^33
-
-	carry[4] = (h4 + (1 << 25)) >> 26
-	h5 += carry[4]
-	h4 -= carry[4] << 26
-	carry[8] = (h8 + (1 << 25)) >> 26
-	h9 += carry[8]
-	h8 -= carry[8] << 26
-	// |h4| <= 2^25; from now on fits into int32 unchanged
-	// |h8| <= 2^25; from now on fits into int32 unchanged
-	// |h5| <= 1.01*2^24
-	// |h9| <= 1.51*2^58
-
-	carry[9] = (h9 + (1 << 24)) >> 25
-	h0 += carry[9] * 19
-	h9 -= carry[9] << 25
-	// |h9| <= 2^24; from now on fits into int32 unchanged
-	// |h0| <= 1.8*2^37
-
-	carry[0] = (h0 + (1 << 25)) >> 26
-	h1 += carry[0]
-	h0 -= carry[0] << 26
-	// |h0| <= 2^25; from now on fits into int32 unchanged
-	// |h1| <= 1.01*2^24
-
-	h[0] = int32(h0)
-	h[1] = int32(h1)
-	h[2] = int32(h2)
-	h[3] = int32(h3)
-	h[4] = int32(h4)
-	h[5] = int32(h5)
-	h[6] = int32(h6)
-	h[7] = int32(h7)
-	h[8] = int32(h8)
-	h[9] = int32(h9)
-}
-
-// feSquare calculates h = f*f. Can overlap h with f.
-//
-// Preconditions:
-//    |f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
-//
-// Postconditions:
-//    |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
-func feSquare(h, f *fieldElement) {
-	f0 := f[0]
-	f1 := f[1]
-	f2 := f[2]
-	f3 := f[3]
-	f4 := f[4]
-	f5 := f[5]
-	f6 := f[6]
-	f7 := f[7]
-	f8 := f[8]
-	f9 := f[9]
-	f0_2 := 2 * f0
-	f1_2 := 2 * f1
-	f2_2 := 2 * f2
-	f3_2 := 2 * f3
-	f4_2 := 2 * f4
-	f5_2 := 2 * f5
-	f6_2 := 2 * f6
-	f7_2 := 2 * f7
-	f5_38 := 38 * f5 // 1.31*2^30
-	f6_19 := 19 * f6 // 1.31*2^30
-	f7_38 := 38 * f7 // 1.31*2^30
-	f8_19 := 19 * f8 // 1.31*2^30
-	f9_38 := 38 * f9 // 1.31*2^30
-	f0f0 := int64(f0) * int64(f0)
-	f0f1_2 := int64(f0_2) * int64(f1)
-	f0f2_2 := int64(f0_2) * int64(f2)
-	f0f3_2 := int64(f0_2) * int64(f3)
-	f0f4_2 := int64(f0_2) * int64(f4)
-	f0f5_2 := int64(f0_2) * int64(f5)
-	f0f6_2 := int64(f0_2) * int64(f6)
-	f0f7_2 := int64(f0_2) * int64(f7)
-	f0f8_2 := int64(f0_2) * int64(f8)
-	f0f9_2 := int64(f0_2) * int64(f9)
-	f1f1_2 := int64(f1_2) * int64(f1)
-	f1f2_2 := int64(f1_2) * int64(f2)
-	f1f3_4 := int64(f1_2) * int64(f3_2)
-	f1f4_2 := int64(f1_2) * int64(f4)
-	f1f5_4 := int64(f1_2) * int64(f5_2)
-	f1f6_2 := int64(f1_2) * int64(f6)
-	f1f7_4 := int64(f1_2) * int64(f7_2)
-	f1f8_2 := int64(f1_2) * int64(f8)
-	f1f9_76 := int64(f1_2) * int64(f9_38)
-	f2f2 := int64(f2) * int64(f2)
-	f2f3_2 := int64(f2_2) * int64(f3)
-	f2f4_2 := int64(f2_2) * int64(f4)
-	f2f5_2 := int64(f2_2) * int64(f5)
-	f2f6_2 := int64(f2_2) * int64(f6)
-	f2f7_2 := int64(f2_2) * int64(f7)
-	f2f8_38 := int64(f2_2) * int64(f8_19)
-	f2f9_38 := int64(f2) * int64(f9_38)
-	f3f3_2 := int64(f3_2) * int64(f3)
-	f3f4_2 := int64(f3_2) * int64(f4)
-	f3f5_4 := int64(f3_2) * int64(f5_2)
-	f3f6_2 := int64(f3_2) * int64(f6)
-	f3f7_76 := int64(f3_2) * int64(f7_38)
-	f3f8_38 := int64(f3_2) * int64(f8_19)
-	f3f9_76 := int64(f3_2) * int64(f9_38)
-	f4f4 := int64(f4) * int64(f4)
-	f4f5_2 := int64(f4_2) * int64(f5)
-	f4f6_38 := int64(f4_2) * int64(f6_19)
-	f4f7_38 := int64(f4) * int64(f7_38)
-	f4f8_38 := int64(f4_2) * int64(f8_19)
-	f4f9_38 := int64(f4) * int64(f9_38)
-	f5f5_38 := int64(f5) * int64(f5_38)
-	f5f6_38 := int64(f5_2) * int64(f6_19)
-	f5f7_76 := int64(f5_2) * int64(f7_38)
-	f5f8_38 := int64(f5_2) * int64(f8_19)
-	f5f9_76 := int64(f5_2) * int64(f9_38)
-	f6f6_19 := int64(f6) * int64(f6_19)
-	f6f7_38 := int64(f6) * int64(f7_38)
-	f6f8_38 := int64(f6_2) * int64(f8_19)
-	f6f9_38 := int64(f6) * int64(f9_38)
-	f7f7_38 := int64(f7) * int64(f7_38)
-	f7f8_38 := int64(f7_2) * int64(f8_19)
-	f7f9_76 := int64(f7_2) * int64(f9_38)
-	f8f8_19 := int64(f8) * int64(f8_19)
-	f8f9_38 := int64(f8) * int64(f9_38)
-	f9f9_38 := int64(f9) * int64(f9_38)
-	h0 := f0f0 + f1f9_76 + f2f8_38 + f3f7_76 + f4f6_38 + f5f5_38
-	h1 := f0f1_2 + f2f9_38 + f3f8_38 + f4f7_38 + f5f6_38
-	h2 := f0f2_2 + f1f1_2 + f3f9_76 + f4f8_38 + f5f7_76 + f6f6_19
-	h3 := f0f3_2 + f1f2_2 + f4f9_38 + f5f8_38 + f6f7_38
-	h4 := f0f4_2 + f1f3_4 + f2f2 + f5f9_76 + f6f8_38 + f7f7_38
-	h5 := f0f5_2 + f1f4_2 + f2f3_2 + f6f9_38 + f7f8_38
-	h6 := f0f6_2 + f1f5_4 + f2f4_2 + f3f3_2 + f7f9_76 + f8f8_19
-	h7 := f0f7_2 + f1f6_2 + f2f5_2 + f3f4_2 + f8f9_38
-	h8 := f0f8_2 + f1f7_4 + f2f6_2 + f3f5_4 + f4f4 + f9f9_38
-	h9 := f0f9_2 + f1f8_2 + f2f7_2 + f3f6_2 + f4f5_2
-	var carry [10]int64
-
-	carry[0] = (h0 + (1 << 25)) >> 26
-	h1 += carry[0]
-	h0 -= carry[0] << 26
-	carry[4] = (h4 + (1 << 25)) >> 26
-	h5 += carry[4]
-	h4 -= carry[4] << 26
-
-	carry[1] = (h1 + (1 << 24)) >> 25
-	h2 += carry[1]
-	h1 -= carry[1] << 25
-	carry[5] = (h5 + (1 << 24)) >> 25
-	h6 += carry[5]
-	h5 -= carry[5] << 25
-
-	carry[2] = (h2 + (1 << 25)) >> 26
-	h3 += carry[2]
-	h2 -= carry[2] << 26
-	carry[6] = (h6 + (1 << 25)) >> 26
-	h7 += carry[6]
-	h6 -= carry[6] << 26
-
-	carry[3] = (h3 + (1 << 24)) >> 25
-	h4 += carry[3]
-	h3 -= carry[3] << 25
-	carry[7] = (h7 + (1 << 24)) >> 25
-	h8 += carry[7]
-	h7 -= carry[7] << 25
-
-	carry[4] = (h4 + (1 << 25)) >> 26
-	h5 += carry[4]
-	h4 -= carry[4] << 26
-	carry[8] = (h8 + (1 << 25)) >> 26
-	h9 += carry[8]
-	h8 -= carry[8] << 26
-
-	carry[9] = (h9 + (1 << 24)) >> 25
-	h0 += carry[9] * 19
-	h9 -= carry[9] << 25
-
-	carry[0] = (h0 + (1 << 25)) >> 26
-	h1 += carry[0]
-	h0 -= carry[0] << 26
-
-	h[0] = int32(h0)
-	h[1] = int32(h1)
-	h[2] = int32(h2)
-	h[3] = int32(h3)
-	h[4] = int32(h4)
-	h[5] = int32(h5)
-	h[6] = int32(h6)
-	h[7] = int32(h7)
-	h[8] = int32(h8)
-	h[9] = int32(h9)
-}
-
-// feMul121666 calculates h = f * 121666. Can overlap h with f.
-//
-// Preconditions:
-//    |f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
-//
-// Postconditions:
-//    |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
-func feMul121666(h, f *fieldElement) {
-	h0 := int64(f[0]) * 121666
-	h1 := int64(f[1]) * 121666
-	h2 := int64(f[2]) * 121666
-	h3 := int64(f[3]) * 121666
-	h4 := int64(f[4]) * 121666
-	h5 := int64(f[5]) * 121666
-	h6 := int64(f[6]) * 121666
-	h7 := int64(f[7]) * 121666
-	h8 := int64(f[8]) * 121666
-	h9 := int64(f[9]) * 121666
-	var carry [10]int64
-
-	carry[9] = (h9 + (1 << 24)) >> 25
-	h0 += carry[9] * 19
-	h9 -= carry[9] << 25
-	carry[1] = (h1 + (1 << 24)) >> 25
-	h2 += carry[1]
-	h1 -= carry[1] << 25
-	carry[3] = (h3 + (1 << 24)) >> 25
-	h4 += carry[3]
-	h3 -= carry[3] << 25
-	carry[5] = (h5 + (1 << 24)) >> 25
-	h6 += carry[5]
-	h5 -= carry[5] << 25
-	carry[7] = (h7 + (1 << 24)) >> 25
-	h8 += carry[7]
-	h7 -= carry[7] << 25
-
-	carry[0] = (h0 + (1 << 25)) >> 26
-	h1 += carry[0]
-	h0 -= carry[0] << 26
-	carry[2] = (h2 + (1 << 25)) >> 26
-	h3 += carry[2]
-	h2 -= carry[2] << 26
-	carry[4] = (h4 + (1 << 25)) >> 26
-	h5 += carry[4]
-	h4 -= carry[4] << 26
-	carry[6] = (h6 + (1 << 25)) >> 26
-	h7 += carry[6]
-	h6 -= carry[6] << 26
-	carry[8] = (h8 + (1 << 25)) >> 26
-	h9 += carry[8]
-	h8 -= carry[8] << 26
-
-	h[0] = int32(h0)
-	h[1] = int32(h1)
-	h[2] = int32(h2)
-	h[3] = int32(h3)
-	h[4] = int32(h4)
-	h[5] = int32(h5)
-	h[6] = int32(h6)
-	h[7] = int32(h7)
-	h[8] = int32(h8)
-	h[9] = int32(h9)
-}
-
-// feInvert sets out = z^-1.
-func feInvert(out, z *fieldElement) {
-	var t0, t1, t2, t3 fieldElement
-	var i int
-
-	feSquare(&t0, z)
-	for i = 1; i < 1; i++ {
-		feSquare(&t0, &t0)
-	}
-	feSquare(&t1, &t0)
-	for i = 1; i < 2; i++ {
-		feSquare(&t1, &t1)
-	}
-	feMul(&t1, z, &t1)
-	feMul(&t0, &t0, &t1)
-	feSquare(&t2, &t0)
-	for i = 1; i < 1; i++ {
-		feSquare(&t2, &t2)
-	}
-	feMul(&t1, &t1, &t2)
-	feSquare(&t2, &t1)
-	for i = 1; i < 5; i++ {
-		feSquare(&t2, &t2)
-	}
-	feMul(&t1, &t2, &t1)
-	feSquare(&t2, &t1)
-	for i = 1; i < 10; i++ {
-		feSquare(&t2, &t2)
-	}
-	feMul(&t2, &t2, &t1)
-	feSquare(&t3, &t2)
-	for i = 1; i < 20; i++ {
-		feSquare(&t3, &t3)
-	}
-	feMul(&t2, &t3, &t2)
-	feSquare(&t2, &t2)
-	for i = 1; i < 10; i++ {
-		feSquare(&t2, &t2)
-	}
-	feMul(&t1, &t2, &t1)
-	feSquare(&t2, &t1)
-	for i = 1; i < 50; i++ {
-		feSquare(&t2, &t2)
-	}
-	feMul(&t2, &t2, &t1)
-	feSquare(&t3, &t2)
-	for i = 1; i < 100; i++ {
-		feSquare(&t3, &t3)
-	}
-	feMul(&t2, &t3, &t2)
-	feSquare(&t2, &t2)
-	for i = 1; i < 50; i++ {
-		feSquare(&t2, &t2)
-	}
-	feMul(&t1, &t2, &t1)
-	feSquare(&t1, &t1)
-	for i = 1; i < 5; i++ {
-		feSquare(&t1, &t1)
-	}
-	feMul(out, &t1, &t0)
-}
-
-func scalarMultGeneric(out, in, base *[32]byte) {
-	var e [32]byte
-
-	copy(e[:], in[:])
-	e[0] &= 248
-	e[31] &= 127
-	e[31] |= 64
-
-	var x1, x2, z2, x3, z3, tmp0, tmp1 fieldElement
-	feFromBytes(&x1, base)
-	feOne(&x2)
-	feCopy(&x3, &x1)
-	feOne(&z3)
-
-	swap := int32(0)
-	for pos := 254; pos >= 0; pos-- {
-		b := e[pos/8] >> uint(pos&7)
-		b &= 1
-		swap ^= int32(b)
-		feCSwap(&x2, &x3, swap)
-		feCSwap(&z2, &z3, swap)
-		swap = int32(b)
-
-		feSub(&tmp0, &x3, &z3)
-		feSub(&tmp1, &x2, &z2)
-		feAdd(&x2, &x2, &z2)
-		feAdd(&z2, &x3, &z3)
-		feMul(&z3, &tmp0, &x2)
-		feMul(&z2, &z2, &tmp1)
-		feSquare(&tmp0, &tmp1)
-		feSquare(&tmp1, &x2)
-		feAdd(&x3, &z3, &z2)
-		feSub(&z2, &z3, &z2)
-		feMul(&x2, &tmp1, &tmp0)
-		feSub(&tmp1, &tmp1, &tmp0)
-		feSquare(&z2, &z2)
-		feMul121666(&z3, &tmp1)
-		feSquare(&x3, &x3)
-		feAdd(&tmp0, &tmp0, &z3)
-		feMul(&z3, &x1, &z2)
-		feMul(&z2, &tmp1, &tmp0)
-	}
-
-	feCSwap(&x2, &x3, swap)
-	feCSwap(&z2, &z3, swap)
-
-	feInvert(&z2, &z2)
-	feMul(&x2, &x2, &z2)
-	feToBytes(out, &x2)
-}
@@ -1,12 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !amd64 || !gc || purego
-// +build !amd64 !gc purego
-
-package curve25519
-
-func scalarMult(out, in, base *[32]byte) {
-	scalarMultGeneric(out, in, base)
-}
@@ -2,13 +2,15 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-package curve25519
+package curve25519_test

 import (
 	"bytes"
 	"crypto/rand"
-	"fmt"
+	"encoding/hex"
 	"testing"
+
+	"golang.org/x/crypto/curve25519"
 )

 const expectedHex = "89161fde887b2b53de549af483940106ecc114d6982daa98256de23bdf77661a"
@@ -19,25 +21,25 @@ func TestX25519Basepoint(t *testing.T) {

 	for i := 0; i < 200; i++ {
 		var err error
-		x, err = X25519(x, Basepoint)
+		x, err = curve25519.X25519(x, curve25519.Basepoint)
 		if err != nil {
 			t.Fatal(err)
 		}
 	}

-	result := fmt.Sprintf("%x", x)
+	result := hex.EncodeToString(x)
 	if result != expectedHex {
 		t.Errorf("incorrect result: got %s, want %s", result, expectedHex)
 	}
 }

 func TestLowOrderPoints(t *testing.T) {
-	scalar := make([]byte, ScalarSize)
+	scalar := make([]byte, curve25519.ScalarSize)
 	if _, err := rand.Read(scalar); err != nil {
 		t.Fatal(err)
 	}
 	for i, p := range lowOrderPoints {
-		out, err := X25519(scalar, p)
+		out, err := curve25519.X25519(scalar, p)
 		if err == nil {
 			t.Errorf("%d: expected error, got nil", i)
 		}
@@ -48,11 +50,10 @@ func TestLowOrderPoints(t *testing.T) {
 }

 func TestTestVectors(t *testing.T) {
-	t.Run("Generic", func(t *testing.T) { testTestVectors(t, scalarMultGeneric) })
-	t.Run("Native", func(t *testing.T) { testTestVectors(t, ScalarMult) })
+	t.Run("Legacy", func(t *testing.T) { testTestVectors(t, curve25519.ScalarMult) })
 	t.Run("X25519", func(t *testing.T) {
 		testTestVectors(t, func(dst, scalar, point *[32]byte) {
-			out, err := X25519(scalar[:], point[:])
+			out, err := curve25519.X25519(scalar[:], point[:])
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -89,22 +90,53 @@ func TestHighBitIgnored(t *testing.T) {
 	var hi0, hi1 [32]byte

 	u[31] &= 0x7f
-	ScalarMult(&hi0, &s, &u)
+	curve25519.ScalarMult(&hi0, &s, &u)

 	u[31] |= 0x80
-	ScalarMult(&hi1, &s, &u)
+	curve25519.ScalarMult(&hi1, &s, &u)

 	if !bytes.Equal(hi0[:], hi1[:]) {
 		t.Errorf("high bit of group point should not affect result")
 	}
 }

-func BenchmarkScalarBaseMult(b *testing.B) {
-	var in, out [32]byte
-	in[0] = 1
+var benchmarkSink byte

-	b.SetBytes(32)
+func BenchmarkX25519Basepoint(b *testing.B) {
+	scalar := make([]byte, curve25519.ScalarSize)
+	if _, err := rand.Read(scalar); err != nil {
+		b.Fatal(err)
+	}
+
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		ScalarBaseMult(&out, &in)
+		out, err := curve25519.X25519(scalar, curve25519.Basepoint)
+		if err != nil {
+			b.Fatal(err)
+		}
+		benchmarkSink ^= out[0]
+	}
+}
+
+func BenchmarkX25519(b *testing.B) {
+	scalar := make([]byte, curve25519.ScalarSize)
+	if _, err := rand.Read(scalar); err != nil {
+		b.Fatal(err)
+	}
+	point, err := curve25519.X25519(scalar, curve25519.Basepoint)
+	if err != nil {
+		b.Fatal(err)
+	}
+	if _, err := rand.Read(scalar); err != nil {
+		b.Fatal(err)
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		out, err := curve25519.X25519(scalar, point)
+		if err != nil {
+			b.Fatal(err)
+		}
+		benchmarkSink ^= out[0]
 	}
 }
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-package curve25519
+package curve25519_test

 // lowOrderPoints from libsodium.
 // https://github.com/jedisct1/libsodium/blob/65621a1059a37d/src/libsodium/crypto_scalarmult/curve25519/ref10/x25519_ref10.c#L11-L70
@@ -1,13 +1,7 @@
-// Copyright 2016 The Go Authors. All rights reserved.
+// Copyright 2019 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// In Go 1.13, the ed25519 package was promoted to the standard library as
-// crypto/ed25519, and this package became a wrapper for the standard library one.
-//
-//go:build !go1.13
-// +build !go1.13
-
 // Package ed25519 implements the Ed25519 signature algorithm. See
 // https://ed25519.cr.yp.to/.
 //
@@ -16,21 +10,13 @@
 // representation includes a public key suffix to make multiple signing
 // operations with the same key more efficient. This package refers to the RFC
 // 8032 private key as the “seed”.
+//
+// This package is a wrapper around the standard library crypto/ed25519 package.
 package ed25519

-// This code is a port of the public domain, “ref10” implementation of ed25519
-// from SUPERCOP.
-
 import (
-	"bytes"
-	"crypto"
-	cryptorand "crypto/rand"
-	"crypto/sha512"
-	"errors"
+	"crypto/ed25519"
 	"io"
-	"strconv"
-
-	"golang.org/x/crypto/ed25519/internal/edwards25519"
 )

 const (
@@ -45,57 +31,21 @@ const (
 )

 // PublicKey is the type of Ed25519 public keys.
-type PublicKey []byte
+//
+// This type is an alias for crypto/ed25519's PublicKey type.
+// See the crypto/ed25519 package for the methods on this type.
+type PublicKey = ed25519.PublicKey

 // PrivateKey is the type of Ed25519 private keys. It implements crypto.Signer.
-type PrivateKey []byte
-
-// Public returns the PublicKey corresponding to priv.
-func (priv PrivateKey) Public() crypto.PublicKey {
-	publicKey := make([]byte, PublicKeySize)
-	copy(publicKey, priv[32:])
-	return PublicKey(publicKey)
-}
-
-// Seed returns the private key seed corresponding to priv. It is provided for
-// interoperability with RFC 8032. RFC 8032's private keys correspond to seeds
-// in this package.
-func (priv PrivateKey) Seed() []byte {
-	seed := make([]byte, SeedSize)
-	copy(seed, priv[:32])
-	return seed
-}
-
-// Sign signs the given message with priv.
-// Ed25519 performs two passes over messages to be signed and therefore cannot
-// handle pre-hashed messages. Thus opts.HashFunc() must return zero to
-// indicate the message hasn't been hashed. This can be achieved by passing
-// crypto.Hash(0) as the value for opts.
-func (priv PrivateKey) Sign(rand io.Reader, message []byte, opts crypto.SignerOpts) (signature []byte, err error) {
-	if opts.HashFunc() != crypto.Hash(0) {
-		return nil, errors.New("ed25519: cannot sign hashed message")
-	}
-
-	return Sign(priv, message), nil
-}
+//
+// This type is an alias for crypto/ed25519's PrivateKey type.
+// See the crypto/ed25519 package for the methods on this type.
+type PrivateKey = ed25519.PrivateKey

 // GenerateKey generates a public/private key pair using entropy from rand.
 // If rand is nil, crypto/rand.Reader will be used.
 func GenerateKey(rand io.Reader) (PublicKey, PrivateKey, error) {
-	if rand == nil {
-		rand = cryptorand.Reader
-	}
-
-	seed := make([]byte, SeedSize)
-	if _, err := io.ReadFull(rand, seed); err != nil {
-		return nil, nil, err
-	}
-
-	privateKey := NewKeyFromSeed(seed)
-	publicKey := make([]byte, PublicKeySize)
-	copy(publicKey, privateKey[32:])
-
-	return publicKey, privateKey, nil
+	return ed25519.GenerateKey(rand)
 }

 // NewKeyFromSeed calculates a private key from a seed. It will panic if
@@ -103,121 +53,17 @@ func GenerateKey(rand io.Reader) (PublicKey, PrivateKey, error) {
 // with RFC 8032. RFC 8032's private keys correspond to seeds in this
 // package.
 func NewKeyFromSeed(seed []byte) PrivateKey {
-	if l := len(seed); l != SeedSize {
-		panic("ed25519: bad seed length: " + strconv.Itoa(l))
-	}
-
-	digest := sha512.Sum512(seed)
-	digest[0] &= 248
-	digest[31] &= 127
-	digest[31] |= 64
-
-	var A edwards25519.ExtendedGroupElement
-	var hBytes [32]byte
-	copy(hBytes[:], digest[:])
-	edwards25519.GeScalarMultBase(&A, &hBytes)
-	var publicKeyBytes [32]byte
-	A.ToBytes(&publicKeyBytes)
-
-	privateKey := make([]byte, PrivateKeySize)
-	copy(privateKey, seed)
-	copy(privateKey[32:], publicKeyBytes[:])
-
-	return privateKey
+	return ed25519.NewKeyFromSeed(seed)
 }

 // Sign signs the message with privateKey and returns a signature. It will
 // panic if len(privateKey) is not PrivateKeySize.
 func Sign(privateKey PrivateKey, message []byte) []byte {
-	if l := len(privateKey); l != PrivateKeySize {
-		panic("ed25519: bad private key length: " + strconv.Itoa(l))
-	}
-
-	h := sha512.New()
-	h.Write(privateKey[:32])
-
-	var digest1, messageDigest, hramDigest [64]byte
-	var expandedSecretKey [32]byte
-	h.Sum(digest1[:0])
-	copy(expandedSecretKey[:], digest1[:])
-	expandedSecretKey[0] &= 248
-	expandedSecretKey[31] &= 63
-	expandedSecretKey[31] |= 64
-
-	h.Reset()
-	h.Write(digest1[32:])
-	h.Write(message)
-	h.Sum(messageDigest[:0])
-
-	var messageDigestReduced [32]byte
-	edwards25519.ScReduce(&messageDigestReduced, &messageDigest)
-	var R edwards25519.ExtendedGroupElement
-	edwards25519.GeScalarMultBase(&R, &messageDigestReduced)
-
-	var encodedR [32]byte
-	R.ToBytes(&encodedR)
-
-	h.Reset()
-	h.Write(encodedR[:])
-	h.Write(privateKey[32:])
-	h.Write(message)
-	h.Sum(hramDigest[:0])
-	var hramDigestReduced [32]byte
-	edwards25519.ScReduce(&hramDigestReduced, &hramDigest)
-
-	var s [32]byte
-	edwards25519.ScMulAdd(&s, &hramDigestReduced, &expandedSecretKey, &messageDigestReduced)
-
-	signature := make([]byte, SignatureSize)
-	copy(signature[:], encodedR[:])
-	copy(signature[32:], s[:])
-
-	return signature
+	return ed25519.Sign(privateKey, message)
 }

 // Verify reports whether sig is a valid signature of message by publicKey. It
 // will panic if len(publicKey) is not PublicKeySize.
 func Verify(publicKey PublicKey, message, sig []byte) bool {
-	if l := len(publicKey); l != PublicKeySize {
-		panic("ed25519: bad public key length: " + strconv.Itoa(l))
-	}
-
-	if len(sig) != SignatureSize || sig[63]&224 != 0 {
-		return false
-	}
-
-	var A edwards25519.ExtendedGroupElement
-	var publicKeyBytes [32]byte
-	copy(publicKeyBytes[:], publicKey)
-	if !A.FromBytes(&publicKeyBytes) {
-		return false
-	}
-	edwards25519.FeNeg(&A.X, &A.X)
-	edwards25519.FeNeg(&A.T, &A.T)
-
-	h := sha512.New()
-	h.Write(sig[:32])
-	h.Write(publicKey[:])
-	h.Write(message)
-	var digest [64]byte
-	h.Sum(digest[:0])
-
-	var hReduced [32]byte
-	edwards25519.ScReduce(&hReduced, &digest)
-
-	var R edwards25519.ProjectiveGroupElement
-	var s [32]byte
-	copy(s[:], sig[32:])
-
-	// https://tools.ietf.org/html/rfc8032#section-5.1.7 requires that s be in
-	// the range [0, order) in order to prevent signature malleability.
-	if !edwards25519.ScMinimal(&s) {
-		return false
-	}
-
-	edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &s)
-
-	var checkR [32]byte
-	R.ToBytes(&checkR)
-	return bytes.Equal(sig[:32], checkR[:])
+	return ed25519.Verify(publicKey, message, sig)
 }
@@ -1,74 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.13
-// +build go1.13
-
-// Package ed25519 implements the Ed25519 signature algorithm. See
-// https://ed25519.cr.yp.to/.
-//
-// These functions are also compatible with the “Ed25519” function defined in
-// RFC 8032. However, unlike RFC 8032's formulation, this package's private key
-// representation includes a public key suffix to make multiple signing
-// operations with the same key more efficient. This package refers to the RFC
-// 8032 private key as the “seed”.
-//
-// Beginning with Go 1.13, the functionality of this package was moved to the
-// standard library as crypto/ed25519. This package only acts as a compatibility
-// wrapper.
-package ed25519
-
-import (
-	"crypto/ed25519"
-	"io"
-)
-
-const (
-	// PublicKeySize is the size, in bytes, of public keys as used in this package.
-	PublicKeySize = 32
-	// PrivateKeySize is the size, in bytes, of private keys as used in this package.
-	PrivateKeySize = 64
-	// SignatureSize is the size, in bytes, of signatures generated and verified by this package.
-	SignatureSize = 64
-	// SeedSize is the size, in bytes, of private key seeds. These are the private key representations used by RFC 8032.
-	SeedSize = 32
-)
-
-// PublicKey is the type of Ed25519 public keys.
-//
-// This type is an alias for crypto/ed25519's PublicKey type.
-// See the crypto/ed25519 package for the methods on this type.
-type PublicKey = ed25519.PublicKey
-
-// PrivateKey is the type of Ed25519 private keys. It implements crypto.Signer.
-//
-// This type is an alias for crypto/ed25519's PrivateKey type.
-// See the crypto/ed25519 package for the methods on this type.
-type PrivateKey = ed25519.PrivateKey
-
-// GenerateKey generates a public/private key pair using entropy from rand.
-// If rand is nil, crypto/rand.Reader will be used.
-func GenerateKey(rand io.Reader) (PublicKey, PrivateKey, error) {
-	return ed25519.GenerateKey(rand)
-}
-
-// NewKeyFromSeed calculates a private key from a seed. It will panic if
-// len(seed) is not SeedSize. This function is provided for interoperability
-// with RFC 8032. RFC 8032's private keys correspond to seeds in this
-// package.
-func NewKeyFromSeed(seed []byte) PrivateKey {
-	return ed25519.NewKeyFromSeed(seed)
-}
-
-// Sign signs the message with privateKey and returns a signature. It will
-// panic if len(privateKey) is not PrivateKeySize.
-func Sign(privateKey PrivateKey, message []byte) []byte {
-	return ed25519.Sign(privateKey, message)
-}
-
-// Verify reports whether sig is a valid signature of message by publicKey. It
-// will panic if len(publicKey) is not PublicKeySize.
-func Verify(publicKey PublicKey, message, sig []byte) bool {
-	return ed25519.Verify(publicKey, message, sig)
-}
@@ -1,221 +1,22 @@
-// Copyright 2016 The Go Authors. All rights reserved.
+// Copyright 2019 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package ed25519_test

 import (
-	"bufio"
-	"bytes"
-	"compress/gzip"
-	"crypto"
-	"crypto/rand"
-	"encoding/hex"
-	"os"
-	"strings"
+	ed25519std "crypto/ed25519"
 	"testing"

 	"golang.org/x/crypto/ed25519"
-	"golang.org/x/crypto/ed25519/internal/edwards25519"
 )

-type zeroReader struct{}
-
-func (zeroReader) Read(buf []byte) (int, error) {
-	for i := range buf {
-		buf[i] = 0
-	}
-	return len(buf), nil
-}
-
-func TestUnmarshalMarshal(t *testing.T) {
-	pub, _, _ := ed25519.GenerateKey(rand.Reader)
-
-	var A edwards25519.ExtendedGroupElement
-	var pubBytes [32]byte
-	copy(pubBytes[:], pub)
-	if !A.FromBytes(&pubBytes) {
-		t.Fatalf("ExtendedGroupElement.FromBytes failed")
-	}
-
-	var pub2 [32]byte
-	A.ToBytes(&pub2)
-
-	if pubBytes != pub2 {
-		t.Errorf("FromBytes(%v)->ToBytes does not round-trip, got %x\n", pubBytes, pub2)
-	}
-}
-
-func TestSignVerify(t *testing.T) {
-	var zero zeroReader
-	public, private, _ := ed25519.GenerateKey(zero)
+func TestTypeAlias(t *testing.T) {
+	public, private, _ := ed25519std.GenerateKey(nil)

 	message := []byte("test message")
 	sig := ed25519.Sign(private, message)
 	if !ed25519.Verify(public, message, sig) {
 		t.Errorf("valid signature rejected")
 	}
-
-	wrongMessage := []byte("wrong message")
-	if ed25519.Verify(public, wrongMessage, sig) {
-		t.Errorf("signature of different message accepted")
-	}
-}
-
-func TestCryptoSigner(t *testing.T) {
-	var zero zeroReader
-	public, private, _ := ed25519.GenerateKey(zero)
-
-	signer := crypto.Signer(private)
-
-	publicInterface := signer.Public()
-	public2, ok := publicInterface.(ed25519.PublicKey)
-	if !ok {
-		t.Fatalf("expected PublicKey from Public() but got %T", publicInterface)
-	}
-
-	if !bytes.Equal(public, public2) {
-		t.Errorf("public keys do not match: original:%x vs Public():%x", public, public2)
-	}
-
-	message := []byte("message")
-	var noHash crypto.Hash
-	signature, err := signer.Sign(zero, message, noHash)
-	if err != nil {
-		t.Fatalf("error from Sign(): %s", err)
-	}
-
-	if !ed25519.Verify(public, message, signature) {
-		t.Errorf("Verify failed on signature from Sign()")
-	}
-}
-
-func TestGolden(t *testing.T) {
-	// sign.input.gz is a selection of test cases from
-	// https://ed25519.cr.yp.to/python/sign.input
-	testDataZ, err := os.Open("testdata/sign.input.gz")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer testDataZ.Close()
-	testData, err := gzip.NewReader(testDataZ)
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer testData.Close()
-
-	scanner := bufio.NewScanner(testData)
-	lineNo := 0
-
-	for scanner.Scan() {
-		lineNo++
-
-		line := scanner.Text()
-		parts := strings.Split(line, ":")
-		if len(parts) != 5 {
-			t.Fatalf("bad number of parts on line %d", lineNo)
-		}
-
-		privBytes, _ := hex.DecodeString(parts[0])
-		pubKey, _ := hex.DecodeString(parts[1])
-		msg, _ := hex.DecodeString(parts[2])
-		sig, _ := hex.DecodeString(parts[3])
-		// The signatures in the test vectors also include the message
-		// at the end, but we just want R and S.
-		sig = sig[:ed25519.SignatureSize]
-
-		if l := len(pubKey); l != ed25519.PublicKeySize {
-			t.Fatalf("bad public key length on line %d: got %d bytes", lineNo, l)
-		}
-
-		var priv [ed25519.PrivateKeySize]byte
-		copy(priv[:], privBytes)
-		copy(priv[32:], pubKey)
-
-		sig2 := ed25519.Sign(priv[:], msg)
-		if !bytes.Equal(sig, sig2[:]) {
-			t.Errorf("different signature result on line %d: %x vs %x", lineNo, sig, sig2)
-		}
-
-		if !ed25519.Verify(pubKey, msg, sig2) {
-			t.Errorf("signature failed to verify on line %d", lineNo)
-		}
-
-		priv2 := ed25519.NewKeyFromSeed(priv[:32])
-		if !bytes.Equal(priv[:], priv2) {
-			t.Errorf("recreating key pair gave different private key on line %d: %x vs %x", lineNo, priv[:], priv2)
-		}
-
-		if pubKey2 := priv2.Public().(ed25519.PublicKey); !bytes.Equal(pubKey, pubKey2) {
-			t.Errorf("recreating key pair gave different public key on line %d: %x vs %x", lineNo, pubKey, pubKey2)
-		}
-
-		if seed := priv2.Seed(); !bytes.Equal(priv[:32], seed) {
-			t.Errorf("recreating key pair gave different seed on line %d: %x vs %x", lineNo, priv[:32], seed)
-		}
-	}
-
-	if err := scanner.Err(); err != nil {
-		t.Fatalf("error reading test data: %s", err)
-	}
-}
-
-func TestMalleability(t *testing.T) {
-	// https://tools.ietf.org/html/rfc8032#section-5.1.7 adds an additional test
-	// that s be in [0, order). This prevents someone from adding a multiple of
-	// order to s and obtaining a second valid signature for the same message.
-	msg := []byte{0x54, 0x65, 0x73, 0x74}
-	sig := []byte{
-		0x7c, 0x38, 0xe0, 0x26, 0xf2, 0x9e, 0x14, 0xaa, 0xbd, 0x05, 0x9a,
-		0x0f, 0x2d, 0xb8, 0xb0, 0xcd, 0x78, 0x30, 0x40, 0x60, 0x9a, 0x8b,
-		0xe6, 0x84, 0xdb, 0x12, 0xf8, 0x2a, 0x27, 0x77, 0x4a, 0xb0, 0x67,
-		0x65, 0x4b, 0xce, 0x38, 0x32, 0xc2, 0xd7, 0x6f, 0x8f, 0x6f, 0x5d,
-		0xaf, 0xc0, 0x8d, 0x93, 0x39, 0xd4, 0xee, 0xf6, 0x76, 0x57, 0x33,
-		0x36, 0xa5, 0xc5, 0x1e, 0xb6, 0xf9, 0x46, 0xb3, 0x1d,
-	}
-	publicKey := []byte{
-		0x7d, 0x4d, 0x0e, 0x7f, 0x61, 0x53, 0xa6, 0x9b, 0x62, 0x42, 0xb5,
-		0x22, 0xab, 0xbe, 0xe6, 0x85, 0xfd, 0xa4, 0x42, 0x0f, 0x88, 0x34,
-		0xb1, 0x08, 0xc3, 0xbd, 0xae, 0x36, 0x9e, 0xf5, 0x49, 0xfa,
-	}
-
-	if ed25519.Verify(publicKey, msg, sig) {
-		t.Fatal("non-canonical signature accepted")
-	}
-}
-
-func BenchmarkKeyGeneration(b *testing.B) {
-	var zero zeroReader
-	for i := 0; i < b.N; i++ {
-		if _, _, err := ed25519.GenerateKey(zero); err != nil {
-			b.Fatal(err)
-		}
-	}
-}
-
-func BenchmarkSigning(b *testing.B) {
-	var zero zeroReader
-	_, priv, err := ed25519.GenerateKey(zero)
-	if err != nil {
-		b.Fatal(err)
-	}
-	message := []byte("Hello, world!")
-	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
-		ed25519.Sign(priv, message)
-	}
-}
-
-func BenchmarkVerification(b *testing.B) {
-	var zero zeroReader
-	pub, priv, err := ed25519.GenerateKey(zero)
-	if err != nil {
-		b.Fatal(err)
-	}
-	message := []byte("Hello, world!")
-	signature := ed25519.Sign(priv, message)
-	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
-		ed25519.Verify(pub, message, signature)
-	}
 }
@@ -1,25 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.13
-// +build go1.13
-
-package ed25519_test
-
-import (
-	ed25519std "crypto/ed25519"
-	"golang.org/x/crypto/ed25519"
-	"testing"
-)
-
-func TestTypeAlias(t *testing.T) {
-	var zero zeroReader
-	public, private, _ := ed25519std.GenerateKey(zero)
-
-	message := []byte("test message")
-	sig := ed25519.Sign(private, message)
-	if !ed25519.Verify(public, message, sig) {
-		t.Errorf("valid signature rejected")
-	}
-}
@@ -1,10 +1,11 @@
 module golang.org/x/crypto

-go 1.17
+go 1.20

 require (
-	golang.org/x/net v0.0.0-20210226172049-e18ecbb05110
-	golang.org/x/sys v0.0.0-20201119102817-f84b799fce68
-	golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1
-	golang.org/x/text v0.3.3 // indirect
+	golang.org/x/net v0.21.0 // tagx:ignore
+	golang.org/x/sys v0.23.0
+	golang.org/x/term v0.23.0
 )
+
+require golang.org/x/text v0.17.0 // indirect
@@ -1,9 +1,8 @@
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 h1:qWPm9rbaAMKs8Bq/9LRpbMqxWRVUAQwMI9fVrssnTfw=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 h1:nxC68pudNYkKU6jWhgrqdreuFiOQWj1Fs7T3VrH4Pjw=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1 h1:v+OssWQX+hTHEmOBgwxdZxK4zHq3yOs8F9J7mk0PY8E=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/text v0.3.3 h1:cokOdA+Jmi5PJGXLlLllQSgYigAEfHXJAERHVMaCc2k=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/net v0.21.0 h1:AQyQV4dYCvJ7vGmJyKki9+PBdyvhkSd8EIx/qb0AYv4=
+golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=
+golang.org/x/sys v0.23.0 h1:YfKFowiIMvtgl1UERQoTPPToxltDeZfbj4H7dVUCwmM=
+golang.org/x/sys v0.23.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/term v0.23.0 h1:F6D4vR+EHoL9/sWAWgAR1H2DcHr4PareCbAaCo1RpuU=
+golang.org/x/term v0.23.0/go.mod h1:DgV24QBUrK6jhZXl+20l6UWznPlwAHm1Q1mGHtydmSk=
+golang.org/x/text v0.17.0 h1:XtiM5bkSOt+ewxlOE/aE/AKEHibwj/6gvWMl9Rsh0Qc=
+golang.org/x/text v0.17.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
@@ -8,7 +8,7 @@
 // HKDF is a cryptographic key derivation function (KDF) with the goal of
 // expanding limited input keying material into one or more cryptographically
 // strong secret keys.
-package hkdf // import "golang.org/x/crypto/hkdf"
+package hkdf

 import (
 	"crypto/hmac"
@@ -56,7 +56,9 @@ func (f *hkdf) Read(p []byte) (int, error) {

 	// Fill the rest of the buffer
 	for len(p) > 0 {
-		f.expander.Reset()
+		if f.counter > 1 {
+			f.expander.Reset()
+		}
 		f.expander.Write(f.prev)
 		f.expander.Write(f.info)
 		f.expander.Write([]byte{f.counter})
@@ -3,11 +3,9 @@
 // license that can be found in the LICENSE file.

 //go:build !purego
-// +build !purego

-// Package subtle implements functions that are often useful in cryptographic
-// code but require careful thought to use correctly.
-package subtle // import "golang.org/x/crypto/internal/subtle"
+// Package alias implements memory aliasing tests.
+package alias

 import "unsafe"

@@ -3,11 +3,9 @@
 // license that can be found in the LICENSE file.

 //go:build purego
-// +build purego

-// Package subtle implements functions that are often useful in cryptographic
-// code but require careful thought to use correctly.
-package subtle // import "golang.org/x/crypto/internal/subtle"
+// Package alias implements memory aliasing tests.
+package alias

 // This is the Google App Engine standard variant based on reflect
 // because the unsafe package and cgo are disallowed.
@@ -2,13 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-package subtle_test
+package alias

-import (
-	"testing"
-
-	"golang.org/x/crypto/internal/subtle"
-)
+import "testing"

 var a, b [100]byte

@@ -32,11 +28,11 @@ var aliasingTests = []struct {
 }

 func testAliasing(t *testing.T, i int, x, y []byte, anyOverlap, inexactOverlap bool) {
-	any := subtle.AnyOverlap(x, y)
+	any := AnyOverlap(x, y)
 	if any != anyOverlap {
 		t.Errorf("%d: wrong AnyOverlap result, expected %v, got %v", i, anyOverlap, any)
 	}
-	inexact := subtle.InexactOverlap(x, y)
+	inexact := InexactOverlap(x, y)
 	if inexact != inexactOverlap {
 		t.Errorf("%d: wrong InexactOverlap result, expected %v, got %v", i, inexactOverlap, any)
 	}
@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build (!amd64 && !ppc64le && !s390x) || !gc || purego
-// +build !amd64,!ppc64le,!s390x !gc purego

 package poly1305

@@ -15,7 +15,7 @@
 // used with a fixed key in order to generate one-time keys from an nonce.
 // However, in this package AES isn't used and the one-time key is specified
 // directly.
-package poly1305 // import "golang.org/x/crypto/poly1305"
+package poly1305

 import "crypto/subtle"

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build gc && !purego
-// +build gc,!purego

 package poly1305

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build gc,!purego
+//go:build gc && !purego

 #include "textflag.h"

@@ -7,7 +7,10 @@

 package poly1305

-import "encoding/binary"
+import (
+	"encoding/binary"
+	"math/bits"
+)

 // Poly1305 [RFC 7539] is a relatively simple algorithm: the authentication tag
 // for a 64 bytes message is approximately
@@ -114,13 +117,13 @@ type uint128 struct {
 }

 func mul64(a, b uint64) uint128 {
-	hi, lo := bitsMul64(a, b)
+	hi, lo := bits.Mul64(a, b)
 	return uint128{lo, hi}
 }

 func add128(a, b uint128) uint128 {
-	lo, c := bitsAdd64(a.lo, b.lo, 0)
-	hi, c := bitsAdd64(a.hi, b.hi, c)
+	lo, c := bits.Add64(a.lo, b.lo, 0)
+	hi, c := bits.Add64(a.hi, b.hi, c)
 	if c != 0 {
 		panic("poly1305: unexpected overflow")
 	}
@@ -136,7 +139,7 @@ func shiftRightBy2(a uint128) uint128 {
 // updateGeneric absorbs msg into the state.h accumulator. For each chunk m of
 // 128 bits of message, it computes
 //
-//     h₊ = (h + m) * r  mod  2¹³⁰ - 5
+//	h₊ = (h + m) * r  mod  2¹³⁰ - 5
 //
 // If the msg length is not a multiple of TagSize, it assumes the last
 // incomplete chunk is the final one.
@@ -155,8 +158,8 @@ func updateGeneric(state *macState, msg []byte) {
 		// hide leading zeroes. For full chunks, that's 1 << 128, so we can just
 		// add 1 to the most significant (2¹²⁸) limb, h2.
 		if len(msg) >= TagSize {
-			h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(msg[0:8]), 0)
-			h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(msg[8:16]), c)
+			h0, c = bits.Add64(h0, binary.LittleEndian.Uint64(msg[0:8]), 0)
+			h1, c = bits.Add64(h1, binary.LittleEndian.Uint64(msg[8:16]), c)
 			h2 += c + 1

 			msg = msg[TagSize:]
@@ -165,8 +168,8 @@ func updateGeneric(state *macState, msg []byte) {
 			copy(buf[:], msg)
 			buf[len(msg)] = 1

-			h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(buf[0:8]), 0)
-			h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(buf[8:16]), c)
+			h0, c = bits.Add64(h0, binary.LittleEndian.Uint64(buf[0:8]), 0)
+			h1, c = bits.Add64(h1, binary.LittleEndian.Uint64(buf[8:16]), c)
 			h2 += c

 			msg = nil
@@ -219,9 +222,9 @@ func updateGeneric(state *macState, msg []byte) {
 		m3 := h2r1

 		t0 := m0.lo
-		t1, c := bitsAdd64(m1.lo, m0.hi, 0)
-		t2, c := bitsAdd64(m2.lo, m1.hi, c)
-		t3, _ := bitsAdd64(m3.lo, m2.hi, c)
+		t1, c := bits.Add64(m1.lo, m0.hi, 0)
+		t2, c := bits.Add64(m2.lo, m1.hi, c)
+		t3, _ := bits.Add64(m3.lo, m2.hi, c)

 		// Now we have the result as 4 64-bit limbs, and we need to reduce it
 		// modulo 2¹³⁰ - 5. The special shape of this Crandall prime lets us do
@@ -243,14 +246,14 @@ func updateGeneric(state *macState, msg []byte) {

 		// To add c * 5 to h, we first add cc = c * 4, and then add (cc >> 2) = c.

-		h0, c = bitsAdd64(h0, cc.lo, 0)
-		h1, c = bitsAdd64(h1, cc.hi, c)
+		h0, c = bits.Add64(h0, cc.lo, 0)
+		h1, c = bits.Add64(h1, cc.hi, c)
 		h2 += c

 		cc = shiftRightBy2(cc)

-		h0, c = bitsAdd64(h0, cc.lo, 0)
-		h1, c = bitsAdd64(h1, cc.hi, c)
+		h0, c = bits.Add64(h0, cc.lo, 0)
+		h1, c = bits.Add64(h1, cc.hi, c)
 		h2 += c

 		// h2 is at most 3 + 1 + 1 = 5, making the whole of h at most
@@ -278,8 +281,7 @@ const (

 // finalize completes the modular reduction of h and computes
 //
-//     out = h + s  mod  2¹²⁸
-//
+//	out = h + s  mod  2¹²⁸
 func finalize(out *[TagSize]byte, h *[3]uint64, s *[2]uint64) {
 	h0, h1, h2 := h[0], h[1], h[2]

@@ -288,9 +290,9 @@ func finalize(out *[TagSize]byte, h *[3]uint64, s *[2]uint64) {
 	// in constant time, we compute t = h - (2¹³⁰ - 5), and select h as the
 	// result if the subtraction underflows, and t otherwise.

-	hMinusP0, b := bitsSub64(h0, p0, 0)
-	hMinusP1, b := bitsSub64(h1, p1, b)
-	_, b = bitsSub64(h2, p2, b)
+	hMinusP0, b := bits.Sub64(h0, p0, 0)
+	hMinusP1, b := bits.Sub64(h1, p1, b)
+	_, b = bits.Sub64(h2, p2, b)

 	// h = h if h < p else h - p
 	h0 = select64(b, h0, hMinusP0)
@@ -302,8 +304,8 @@ func finalize(out *[TagSize]byte, h *[3]uint64, s *[2]uint64) {
 	//
 	// by just doing a wide addition with the 128 low bits of h and discarding
 	// the overflow.
-	h0, c := bitsAdd64(h0, s[0], 0)
-	h1, _ = bitsAdd64(h1, s[1], c)
+	h0, c := bits.Add64(h0, s[0], 0)
+	h1, _ = bits.Add64(h1, s[1], c)

 	binary.LittleEndian.PutUint64(out[0:8], h0)
 	binary.LittleEndian.PutUint64(out[8:16], h1)
@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build gc && !purego
-// +build gc,!purego

 package poly1305

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build gc,!purego
+//go:build gc && !purego

 #include "textflag.h"

@@ -19,15 +19,14 @@

 #define POLY1305_MUL(h0, h1, h2, r0, r1, t0, t1, t2, t3, t4, t5) \
 	MULLD  r0, h0, t0;  \
-	MULLD  r0, h1, t4;  \
 	MULHDU r0, h0, t1;  \
+	MULLD  r0, h1, t4;  \
 	MULHDU r0, h1, t5;  \
 	ADDC   t4, t1, t1;  \
 	MULLD  r0, h2, t2;  \
-	ADDZE  t5;          \
 	MULHDU r1, h0, t4;  \
 	MULLD  r1, h0, h0;  \
-	ADD    t5, t2, t2;  \
+	ADDE   t5, t2, t2;  \
 	ADDC   h0, t1, t1;  \
 	MULLD  h2, r1, t3;  \
 	ADDZE  t4, h0;      \
@@ -37,13 +36,11 @@
 	ADDE   t5, t3, t3;  \
 	ADDC   h0, t2, t2;  \
 	MOVD   $-4, t4;     \
-	MOVD   t0, h0;      \
-	MOVD   t1, h1;      \
 	ADDZE  t3;          \
-	ANDCC  $3, t2, h2;  \
-	AND    t2, t4, t0;  \
+	RLDICL $0, t2, $62, h2; \
+	AND    t2, t4, h0;  \
 	ADDC   t0, h0, h0;  \
-	ADDE   t3, h1, h1;  \
+	ADDE   t3, t1, h1;  \
 	SLD    $62, t3, t4; \
 	SRD    $2, t2;      \
 	ADDZE  h2;          \
@@ -75,6 +72,7 @@ TEXT ·update(SB), $0-32
 loop:
 	POLY1305_ADD(R4, R8, R9, R10, R20, R21, R22)

+	PCALIGN $16
 multiply:
 	POLY1305_MUL(R8, R9, R10, R11, R12, R16, R17, R18, R14, R20, R21)
 	ADD $-16, R5
@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.

 //go:build gc && !purego
-// +build gc,!purego

 package poly1305

@@ -14,6 +13,7 @@ import (
 // updateVX is an assembly implementation of Poly1305 that uses vector
 // instructions. It must only be called if the vector facility (vx) is
 // available.
+//
 //go:noescape
 func updateVX(state *macState, msg []byte)

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

-// +build gc,!purego
+//go:build gc && !purego

 #include "textflag.h"

@@ -17,7 +17,7 @@
 // value. These limbs are, for the most part, zero extended and
 // placed into 64-bit vector register elements. Each vector
 // register is 128-bits wide and so holds 2 of these elements.
-// Using 26-bit limbs allows us plenty of headroom to accomodate
+// Using 26-bit limbs allows us plenty of headroom to accommodate
 // accumulations before and after multiplication without
 // overflowing either 32-bits (before multiplication) or 64-bits
 // (after multiplication).
@@ -0,0 +1,120 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package testenv
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"reflect"
+	"strconv"
+	"testing"
+	"time"
+)
+
+// CommandContext is like exec.CommandContext, but:
+//   - skips t if the platform does not support os/exec,
+//   - sends SIGQUIT (if supported by the platform) instead of SIGKILL
+//     in its Cancel function
+//   - if the test has a deadline, adds a Context timeout and WaitDelay
+//     for an arbitrary grace period before the test's deadline expires,
+//   - fails the test if the command does not complete before the test's deadline, and
+//   - sets a Cleanup function that verifies that the test did not leak a subprocess.
+func CommandContext(t testing.TB, ctx context.Context, name string, args ...string) *exec.Cmd {
+	t.Helper()
+
+	var (
+		cancelCtx   context.CancelFunc
+		gracePeriod time.Duration // unlimited unless the test has a deadline (to allow for interactive debugging)
+	)
+
+	if t, ok := t.(interface {
+		testing.TB
+		Deadline() (time.Time, bool)
+	}); ok {
+		if td, ok := t.Deadline(); ok {
+			// Start with a minimum grace period, just long enough to consume the
+			// output of a reasonable program after it terminates.
+			gracePeriod = 100 * time.Millisecond
+			if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
+				scale, err := strconv.Atoi(s)
+				if err != nil {
+					t.Fatalf("invalid GO_TEST_TIMEOUT_SCALE: %v", err)
+				}
+				gracePeriod *= time.Duration(scale)
+			}
+
+			// If time allows, increase the termination grace period to 5% of the
+			// test's remaining time.
+			testTimeout := time.Until(td)
+			if gp := testTimeout / 20; gp > gracePeriod {
+				gracePeriod = gp
+			}
+
+			// When we run commands that execute subprocesses, we want to reserve two
+			// grace periods to clean up: one for the delay between the first
+			// termination signal being sent (via the Cancel callback when the Context
+			// expires) and the process being forcibly terminated (via the WaitDelay
+			// field), and a second one for the delay between the process being
+			// terminated and the test logging its output for debugging.
+			//
+			// (We want to ensure that the test process itself has enough time to
+			// log the output before it is also terminated.)
+			cmdTimeout := testTimeout - 2*gracePeriod
+
+			if cd, ok := ctx.Deadline(); !ok || time.Until(cd) > cmdTimeout {
+				// Either ctx doesn't have a deadline, or its deadline would expire
+				// after (or too close before) the test has already timed out.
+				// Add a shorter timeout so that the test will produce useful output.
+				ctx, cancelCtx = context.WithTimeout(ctx, cmdTimeout)
+			}
+		}
+	}
+
+	cmd := exec.CommandContext(ctx, name, args...)
+	// Set the Cancel and WaitDelay fields only if present (go 1.20 and later).
+	// TODO: When Go 1.19 is no longer supported, remove this use of reflection
+	// and instead set the fields directly.
+	if cmdCancel := reflect.ValueOf(cmd).Elem().FieldByName("Cancel"); cmdCancel.IsValid() {
+		cmdCancel.Set(reflect.ValueOf(func() error {
+			if cancelCtx != nil && ctx.Err() == context.DeadlineExceeded {
+				// The command timed out due to running too close to the test's deadline.
+				// There is no way the test did that intentionally — it's too close to the
+				// wire! — so mark it as a test failure. That way, if the test expects the
+				// command to fail for some other reason, it doesn't have to distinguish
+				// between that reason and a timeout.
+				t.Errorf("test timed out while running command: %v", cmd)
+			} else {
+				// The command is being terminated due to ctx being canceled, but
+				// apparently not due to an explicit test deadline that we added.
+				// Log that information in case it is useful for diagnosing a failure,
+				// but don't actually fail the test because of it.
+				t.Logf("%v: terminating command: %v", ctx.Err(), cmd)
+			}
+			return cmd.Process.Signal(Sigquit)
+		}))
+	}
+	if cmdWaitDelay := reflect.ValueOf(cmd).Elem().FieldByName("WaitDelay"); cmdWaitDelay.IsValid() {
+		cmdWaitDelay.Set(reflect.ValueOf(gracePeriod))
+	}
+
+	t.Cleanup(func() {
+		if cancelCtx != nil {
+			cancelCtx()
+		}
+		if cmd.Process != nil && cmd.ProcessState == nil {
+			t.Errorf("command was started, but test did not wait for it to complete: %v", cmd)
+		}
+	})
+
+	return cmd
+}
+
+// Command is like exec.Command, but applies the same changes as
+// testenv.CommandContext (with a default Context).
+func Command(t testing.TB, name string, args ...string) *exec.Cmd {
+	t.Helper()
+	return CommandContext(t, context.Background(), name, args...)
+}
@@ -0,0 +1,15 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build windows || plan9 || (js && wasm) || wasip1
+
+package testenv
+
+import (
+	"os"
+)
+
+// Sigquit is the signal to send to kill a hanging subprocess.
+// On Unix we send SIGQUIT, but on non-Unix we only have os.Kill.
+var Sigquit = os.Kill
@@ -0,0 +1,15 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build unix
+
+package testenv
+
+import (
+	"syscall"
+)
+
+// Sigquit is the signal to send to kill a hanging subprocess.
+// Send SIGQUIT to get a stack trace.
+var Sigquit = syscall.SIGQUIT
@@ -0,0 +1,9 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build boringcrypto
+
+package wycheproof
+
+const boringcryptoEnabled = true
--- a/Show More
+++ b/Show More