eiac/crypto
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

crypto/openpgp: add clear-signing support.

Browse Source 
Clear signed messages are often seen in email and are formatted so
that the plaintext of the signed message is readable without any
special tools.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5604043
This commit is contained in:
Adam Langley
2012-02-03 16:46:11 -05:00
parent a1e605a210
commit 303976f059
3 changed files with 584 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
openpgp/clearsign/clearsign.go
+365
View File
@@ -0,0 +1,365 @@
// 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.
// Package clearsign generates and processes OpenPGP, clear-signed data. See
// RFC 4880, section 7.
//
// Clearsigned messages are cryptographically signed, but the contents of the
// message are kept in plaintext so that it can be read without special tools.
package clearsign
import (
"bufio"
"bytes"
"crypto"
"hash"
"io"
"net/textproto"
"strconv"
"time"
"code.google.com/p/go.crypto/openpgp/armor"
"code.google.com/p/go.crypto/openpgp/errors"
"code.google.com/p/go.crypto/openpgp/packet"
)
// A Block represents a clearsigned message. A signature on a Block can
// be checked by passing Bytes into openpgp.CheckDetachedSignature.
type Block struct {
Headers textproto.MIMEHeader // Optional message headers
Plaintext []byte // The original message text
Bytes []byte // The signed message
ArmoredSignature *armor.Block // The signature block
}
// start is the marker which denotes the beginning of a clearsigned message.
var start = []byte("\n-----BEGIN PGP SIGNED MESSAGE-----")
// dashEscape is prefixed to any lines that begin with a hypen so that they
// can't be confused with endText.
var dashEscape = []byte("- ")
// endText is a marker which denotes the end of the message and the start of
// an armored signature.
var endText = []byte("-----BEGIN PGP SIGNATURE-----")
// end is a marker which denotes the end of the armored signature.
var end = []byte("\n-----END PGP SIGNATURE-----")
var crlf = []byte("\r\n")
var lf = byte('\n')
// getLine returns the first \r\n or \n delineated line from the given byte
// array. The line does not include the \r\n or \n. The remainder of the byte
// array (also not including the new line bytes) is also returned and this will
// always be smaller than the original argument.
func getLine(data []byte) (line, rest []byte) {
i := bytes.Index(data, []byte{'\n'})
var j int
if i < 0 {
i = len(data)
j = i
} else {
j = i + 1
if i > 0 && data[i-1] == '\r' {
i--
}
}
return data[0:i], data[j:]
}
// Decode finds the first clearsigned message in data and returns it, as well
// as the suffix of data which remains after the message.
func Decode(data []byte) (b *Block, rest []byte) {
// start begins with a newline. However, at the very beginning of
// the byte array, we'll accept the start string without it.
rest = data
if bytes.HasPrefix(data, start[1:]) {
rest = rest[len(start)-1:]
} else if i := bytes.Index(data, start); i >= 0 {
rest = rest[i+len(start):]
} else {
return nil, data
}
// Consume the start line.
_, rest = getLine(rest)
var line []byte
b = &Block{
Headers: make(textproto.MIMEHeader),
}
// Next come a series of header lines.
for {
// This loop terminates because getLine's second result is
// always smaller than its argument.
if len(rest) == 0 {
return nil, data
}
// An empty line marks the end of the headers.
if line, rest = getLine(rest); len(line) == 0 {
break
}
i := bytes.Index(line, []byte{':'})
if i == -1 {
return nil, data
}
key, val := line[0:i], line[i+1:]
key = bytes.TrimSpace(key)
val = bytes.TrimSpace(val)
b.Headers.Add(string(key), string(val))
}
for {
start := rest
line, rest = getLine(rest)
if bytes.Equal(line, endText) {
// Back up to the start of the line because armor expects to see the
// header line.
rest = start
break
}
// The final CRLF isn't included in the hash so we don't write it until
// we've seen the next line.
if len(b.Bytes) > 0 {
b.Bytes = append(b.Bytes, crlf...)
}
if bytes.HasPrefix(line, dashEscape) {
line = line[2:]
}
line = bytes.TrimRight(line, " \t")
b.Bytes = append(b.Bytes, line...)
b.Plaintext = append(b.Plaintext, line...)
b.Plaintext = append(b.Plaintext, lf)
}
// We want to find the extent of the armored data (including any newlines at
// the end).
i := bytes.Index(rest, end)
if i == -1 {
return nil, data
}
i += len(end)
for i < len(rest) && (rest[i] == '\r' || rest[i] == '\n') {
i++
}
armored := rest[:i]
rest = rest[i:]
var err error
b.ArmoredSignature, err = armor.Decode(bytes.NewBuffer(armored))
if err != nil {
return nil, data
}
return b, rest
}
// A dashEscaper is an io.WriteCloser which processes the body of a clear-signed
// message. The clear-signed message is written to buffered and a hash, suitable
// for signing, is maintained in h.
//
// When closed, an armored signature is created and written to complete the
// message.
type dashEscaper struct {
buffered *bufio.Writer
h hash.Hash
hashType crypto.Hash
atBeginningOfLine bool
isFirstLine bool
whitespace []byte
byteBuf []byte // a one byte buffer to save allocations
privateKey *packet.PrivateKey
signingTime time.Time
rand io.Reader
}
func (d *dashEscaper) Write(data []byte) (n int, err error) {
for _, b := range data {
d.byteBuf[0] = b
if d.atBeginningOfLine {
// The final CRLF isn't included in the hash so we have to wait
// until this point (the start of the next line) before writing it.
if !d.isFirstLine {
d.h.Write(crlf)
}
d.isFirstLine = false
// At the beginning of a line, hyphens have to be escaped.
if b == '-' {
// The signature isn't calculated over the dash-escaped text so
// the escape is only written to buffered.
if _, err = d.buffered.Write(dashEscape); err != nil {
return
}
d.h.Write(d.byteBuf)
d.atBeginningOfLine = false
} else if b == '\n' {
// Nothing to do because we dely writing CRLF to the hash.
} else {
d.h.Write(d.byteBuf)
d.atBeginningOfLine = false
}
if err = d.buffered.WriteByte(b); err != nil {
return
}
} else {
// Any whitespace at the end of the line has to be removed so we
// buffer it until we find out whether there's more on this line.
if b == ' ' || b == '\t' || b == '\r' {
d.whitespace = append(d.whitespace, b)
} else if b == '\n' {
// We got a raw \n. Drop any trailing whitespace and write a
// CRLF.
d.whitespace = d.whitespace[:0]
// We dely writing CRLF to the hash until the start of the
// next line.
if err = d.buffered.WriteByte(b); err != nil {
return
}
d.atBeginningOfLine = true
} else {
// Any buffered whitespace wasn't at the end of the line so
// we need to write it out.
if len(d.whitespace) > 0 {
d.h.Write(d.whitespace)
if _, err = d.buffered.Write(d.whitespace); err != nil {
return
}
d.whitespace = d.whitespace[:0]
}
d.h.Write(d.byteBuf)
if err = d.buffered.WriteByte(b); err != nil {
return
}
}
}
}
n = len(data)
return
}
func (d *dashEscaper) Close() (err error) {
if !d.atBeginningOfLine {
if err = d.buffered.WriteByte(lf); err != nil {
return
}
}
sig := new(packet.Signature)
sig.SigType = packet.SigTypeText
sig.PubKeyAlgo = d.privateKey.PubKeyAlgo
sig.Hash = d.hashType
sig.CreationTime = d.signingTime
sig.IssuerKeyId = &d.privateKey.KeyId
if err = sig.Sign(d.rand, d.h, d.privateKey); err != nil {
return
}
out, err := armor.Encode(d.buffered, "PGP SIGNATURE", nil)
if err != nil {
return
}
if err = sig.Serialize(out); err != nil {
return
}
if err = out.Close(); err != nil {
return
}
if err = d.buffered.Flush(); err != nil {
return
}
return
}
// Encode returns a WriteCloser which will clear-sign a message with privateKey
// and write it to w. If config is nil, sensible defaults are used.
func Encode(w io.Writer, privateKey *packet.PrivateKey, config *packet.Config) (plaintext io.WriteCloser, err error) {
if privateKey.Encrypted {
return nil, errors.InvalidArgumentError("signing key is encrypted")
}
hashType := config.Hash()
name := nameOfHash(hashType)
if len(name) == 0 {
return nil, errors.UnsupportedError("unknown hash type: " + strconv.Itoa(int(hashType)))
}
h := hashType.New()
if h == nil {
return nil, errors.UnsupportedError("unsupported hash type: " + strconv.Itoa(int(hashType)))
}
buffered := bufio.NewWriter(w)
// start has a \n at the beginning that we don't want here.
if _, err = buffered.Write(start[1:]); err != nil {
return
}
if err = buffered.WriteByte(lf); err != nil {
return
}
if _, err = buffered.WriteString("Hash: "); err != nil {
return
}
if _, err = buffered.WriteString(name); err != nil {
return
}
if err = buffered.WriteByte(lf); err != nil {
return
}
if err = buffered.WriteByte(lf); err != nil {
return
}
plaintext = &dashEscaper{
buffered: buffered,
h: h,
hashType: hashType,
atBeginningOfLine: true,
isFirstLine: true,
byteBuf: make([]byte, 1),
privateKey: privateKey,
signingTime: config.Now(),
rand: config.Random(),
}
return
}
// nameOfHash returns the OpenPGP name for the given hash, or the empty string
// if the name isn't known. See RFC 4880, section 9.4.
func nameOfHash(h crypto.Hash) string {
switch h {
case crypto.MD5:
return "MD5"
case crypto.SHA1:
return "SHA1"
case crypto.RIPEMD160:
return "RIPEMD160"
case crypto.SHA224:
return "SHA224"
case crypto.SHA256:
return "SHA256"
case crypto.SHA384:
return "SHA384"
case crypto.SHA512:
return "SHA512"
}
return ""
}
openpgp/clearsign/clearsign_test.go
+161
View File
@@ -0,0 +1,161 @@
// 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.
package clearsign
import (
"bytes"
"code.google.com/p/go.crypto/openpgp"
"testing"
)
func TestParse(t *testing.T) {
b, rest := Decode(clearsignInput)
if b == nil {
t.Fatal("failed to decode clearsign message")
}
if !bytes.Equal(rest, []byte("trailing")) {
t.Errorf("unexpected remaining bytes returned: %s", string(rest))
}
if b.ArmoredSignature.Type != "PGP SIGNATURE" {
t.Errorf("bad armor type, got:%s, want:PGP SIGNATURE", b.ArmoredSignature.Type)
}
expected := []byte("Hello world\r\nline 2")
if !bytes.Equal(b.Bytes, expected) {
t.Errorf("bad body, got:%x want:%x", b.Bytes, expected)
}
expected = []byte("Hello world\nline 2\n")
if !bytes.Equal(b.Plaintext, expected) {
t.Errorf("bad plaintext, got:%x want:%x", b.Plaintext, expected)
}
keyring, err := openpgp.ReadArmoredKeyRing(bytes.NewBufferString(signingKey))
if err != nil {
t.Errorf("failed to parse public key: %s", err)
}
if _, err := openpgp.CheckDetachedSignature(keyring, bytes.NewBuffer(b.Bytes), b.ArmoredSignature.Body); err != nil {
t.Errorf("failed to check signature: %s", err)
}
}
func TestParseWithNoNewlineAtEnd(t *testing.T) {
input := clearsignInput
input = input[:len(input)-len("trailing")-1]
b, rest := Decode(input)
if b == nil {
t.Fatal("failed to decode clearsign message")
}
if len(rest) > 0 {
t.Errorf("unexpected remaining bytes returned: %s", string(rest))
}
}
var signingTests = []struct {
in, signed, plaintext string
}{
{"", "", ""},
{"a", "a", "a\n"},
{"a\n", "a", "a\n"},
{"-a\n", "-a", "-a\n"},
{"--a\nb", "--a\r\nb", "--a\nb\n"},
}
func TestSigning(t *testing.T) {
keyring, err := openpgp.ReadArmoredKeyRing(bytes.NewBufferString(signingKey))
if err != nil {
t.Errorf("failed to parse public key: %s", err)
}
for i, test := range signingTests {
var buf bytes.Buffer
plaintext, err := Encode(&buf, keyring[0].PrivateKey, nil)
if err != nil {
t.Errorf("#%d: error from Encode: %s", i, err)
continue
}
if _, err := plaintext.Write([]byte(test.in)); err != nil {
t.Errorf("#%d: error from Write: %s", i, err)
continue
}
if err := plaintext.Close(); err != nil {
t.Fatalf("#%d: error from Close: %s", i, err)
continue
}
b, _ := Decode(buf.Bytes())
if b == nil {
t.Errorf("#%d: failed to decode clearsign message", i)
continue
}
if !bytes.Equal(b.Bytes, []byte(test.signed)) {
t.Errorf("#%d: bad result, got:%x, want:%x", i, b.Bytes, test.signed)
continue
}
if !bytes.Equal(b.Plaintext, []byte(test.plaintext)) {
t.Errorf("#%d: bad result, got:%x, want:%x", i, b.Plaintext, test.plaintext)
continue
}
if _, err := openpgp.CheckDetachedSignature(keyring, bytes.NewBuffer(b.Bytes), b.ArmoredSignature.Body); err != nil {
t.Errorf("#%d: failed to check signature: %s", i, err)
}
}
}
var clearsignInput = []byte(`
;lasjlkfdsa
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Hello world
line 2
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.10 (GNU/Linux)
iJwEAQECAAYFAk8kMuEACgkQO9o98PRieSpMsAQAhmY/vwmNpflrPgmfWsYhk5O8
pjnBUzZwqTDoDeINjZEoPDSpQAHGhjFjgaDx/Gj4fAl0dM4D0wuUEBb6QOrwflog
2A2k9kfSOMOtk0IH/H5VuFN1Mie9L/erYXjTQIptv9t9J7NoRBMU0QOOaFU0JaO9
MyTpno24AjIAGb+mH1U=
=hIJ6
-----END PGP SIGNATURE-----
trailing`)
var signingKey = `-----BEGIN PGP PRIVATE KEY BLOCK-----
Version: GnuPG v1.4.10 (GNU/Linux)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=zNCn
-----END PGP PRIVATE KEY BLOCK-----
`
openpgp/packet/config.go
+58
View File
@@ -0,0 +1,58 @@
// 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.
package packet
import (
"crypto"
"crypto/rand"
"io"
"time"
)
// Config collects a number of parameters along with sensible defaults.
// A nil *Config is valid and produces all default values.
type Config struct {
// Rand provides the source of entropy.
// If nil, the crypto/rand Reader is used.
Rand io.Reader
// DefaultHash is the default hash function to be used.
// If zero, SHA-256 is used.
DefaultHash crypto.Hash
// DefaultCipher is the cipher to be used.
// If zero, AES-128 is used.
DefaultCipher CipherFunction
// Time returns the current time as the number of seconds since the
// epoch. If Time is nil, time.Now is used.
Time func() time.Time
}
func (c *Config) Random() io.Reader {
if c == nil || c.Rand == nil {
return rand.Reader
}
return c.Rand
}
func (c *Config) Hash() crypto.Hash {
if c == nil || uint(c.DefaultHash) == 0 {
return crypto.SHA256
}
return c.DefaultHash
}
func (c *Config) Cipher() CipherFunction {
if c == nil || uint8(c.DefaultCipher) == 0 {
return CipherAES128
}
return c.DefaultCipher
}
func (c *Config) Now() time.Time {
if c == nil || c.Time == nil {
return time.Now()
}
return c.Time()
}