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ssh: support RSA SHA-2 (RFC8332) signatures

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This change adds support for RSA SHA-2 based signatures for host keys and certificates. It also switches the default certificate signature algorithm for RSA to use SHA-512. This is implemented by treating ssh.Signer specially when the key type is `ssh-rsa` by also allowing SHA-256 and SHA-512 signatures.

Fixes golang/go#37278

Change-Id: I2ee1ac4ae4c9c1de441a2d6cf1e806357ef18910
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/220037
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
This commit is contained in:
Hans Nielsen
2021-11-15 23:45:14 +00:00
committed by Jason A. Donenfeld
parent ceb1ce70b4
commit b4de73f9ec
12 changed files with 213 additions and 69 deletions
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ssh/certs.go
+22 -2
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@@ -14,7 +14,7 @@ import (
"time"
)
// These constants from [PROTOCOL.certkeys] represent the algorithm names
// These constants from [PROTOCOL.certkeys] represent the key algorithm names
// for certificate types supported by this package.
const (
CertAlgoRSAv01 = "ssh-rsa-cert-v01@openssh.com"
@@ -27,6 +27,14 @@ const (
CertAlgoSKED25519v01 = "sk-ssh-ed25519-cert-v01@openssh.com"
)
// These constants from [PROTOCOL.certkeys] represent additional signature
// algorithm names for certificate types supported by this package.
const (
CertSigAlgoRSAv01 = "ssh-rsa-cert-v01@openssh.com"
CertSigAlgoRSASHA2256v01 = "rsa-sha2-256-cert-v01@openssh.com"
CertSigAlgoRSASHA2512v01 = "rsa-sha2-512-cert-v01@openssh.com"
)
// Certificate types distinguish between host and user
// certificates. The values can be set in the CertType field of
// Certificate.
@@ -423,6 +431,12 @@ func (c *Certificate) SignCert(rand io.Reader, authority Signer) error {
}
c.SignatureKey = authority.PublicKey()
if v, ok := authority.(AlgorithmSigner); ok {
if v.PublicKey().Type() == KeyAlgoRSA {
authority = &rsaSigner{v, SigAlgoRSASHA2512}
}
}
sig, err := authority.Sign(rand, c.bytesForSigning())
if err != nil {
return err
@@ -431,8 +445,14 @@ func (c *Certificate) SignCert(rand io.Reader, authority Signer) error {
return nil
}
// certAlgoNames includes a mapping from signature algorithms to the
// corresponding certificate signature algorithm. When a key type (such
// as ED25516) is associated with only one algorithm, the KeyAlgo
// constant is used instead of the SigAlgo.
var certAlgoNames = map[string]string{
KeyAlgoRSA: CertAlgoRSAv01,
SigAlgoRSA: CertSigAlgoRSAv01,
SigAlgoRSASHA2256: CertSigAlgoRSASHA2256v01,
SigAlgoRSASHA2512: CertSigAlgoRSASHA2512v01,
KeyAlgoDSA: CertAlgoDSAv01,
KeyAlgoECDSA256: CertAlgoECDSA256v01,
KeyAlgoECDSA384: CertAlgoECDSA384v01,