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crypto/tls: take key size into account in signature algorithm selection

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Fixes #29793

Change-Id: I6e389d166c2d9a2ba8664a41f4b9569f2481b27f
Reviewed-on: https://go-review.googlesource.com/c/go/+/205177
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>
This commit is contained in:
Filippo Valsorda 2019-11-04 02:14:18 -05:00
parent cb4dd9fcb4
commit aff697f53d
6 changed files with 71 additions and 146 deletions
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41
auth.go
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@ -153,6 +153,25 @@ func legacyTypeAndHashFromPublicKey(pub crypto.PublicKey) (sigType uint8, hash c
}
}
var rsaSignatureSchemes = []struct {
scheme SignatureScheme
minModulusBytes int
maxVersion uint16
}{
// RSA-PSS is used with PSSSaltLengthEqualsHash, and requires
// emLen >= hLen + sLen + 2
{PSSWithSHA256, crypto.SHA256.Size()*2 + 2, VersionTLS13},
{PSSWithSHA384, crypto.SHA384.Size()*2 + 2, VersionTLS13},
{PSSWithSHA512, crypto.SHA512.Size()*2 + 2, VersionTLS13},
// PKCS#1 v1.5 uses prefixes from hashPrefixes in crypto/rsa, and requires
// emLen >= len(prefix) + hLen + 11
// TLS 1.3 dropped support for PKCS#1 v1.5 in favor of RSA-PSS.
{PKCS1WithSHA256, 19 + crypto.SHA256.Size() + 11, VersionTLS12},
{PKCS1WithSHA384, 19 + crypto.SHA384.Size() + 11, VersionTLS12},
{PKCS1WithSHA512, 19 + crypto.SHA512.Size() + 11, VersionTLS12},
{PKCS1WithSHA1, 15 + crypto.SHA1.Size() + 11, VersionTLS12},
}
// signatureSchemesForCertificate returns the list of supported SignatureSchemes
// for a given certificate, based on the public key and the protocol version,
// and optionally filtered by its explicit SupportedSignatureAlgorithms.
@ -189,23 +208,12 @@ func signatureSchemesForCertificate(version uint16, cert *Certificate) []Signatu
return nil
}
case *rsa.PublicKey:
if version != VersionTLS13 {
sigAlgs = []SignatureScheme{
PSSWithSHA256,
PSSWithSHA384,
PSSWithSHA512,
PKCS1WithSHA256,
PKCS1WithSHA384,
PKCS1WithSHA512,
PKCS1WithSHA1,
size := pub.Size()
sigAlgs = make([]SignatureScheme, 0, len(rsaSignatureSchemes))
for _, candidate := range rsaSignatureSchemes {
if size >= candidate.minModulusBytes && version <= candidate.maxVersion {
sigAlgs = append(sigAlgs, candidate.scheme)
}
break
}
// TLS 1.3 dropped support for PKCS#1 v1.5 in favor of RSA-PSS.
sigAlgs = []SignatureScheme{
PSSWithSHA256,
PSSWithSHA384,
PSSWithSHA512,
}
case ed25519.PublicKey:
sigAlgs = []SignatureScheme{Ed25519}
@ -275,6 +283,7 @@ func unsupportedCertificateError(cert *Certificate) error {
return fmt.Errorf("tls: unsupported certificate curve (%s)", pub.Curve.Params().Name)
}
case *rsa.PublicKey:
return fmt.Errorf("tls: certificate RSA key size too small for supported signature algorithms")
case ed25519.PublicKey:
default:
return fmt.Errorf("tls: unsupported certificate key (%T)", pub)