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ssh: add support for FIPS mode

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Unsupported algoritms are silently ignored and not negotiated, or
rejected

Fixes golang/go#75061

Change-Id: I08d50d10a97c08e78aedead89ca61beceff88918
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/698795
Reviewed-by: Mio Mio <miomio0086@gmail.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Nicola Murino
2025-09-27 12:36:52 -07:00
parent ddb4e80c6a
commit 66c3d8ce71
8 changed files with 163 additions and 69 deletions
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ssh/common.go
+35 -15
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@@ -6,6 +6,7 @@ package ssh
import (
"crypto"
"crypto/fips140"
"crypto/rand"
"fmt"
"io"
@@ -256,6 +257,40 @@ type Algorithms struct {
PublicKeyAuths []string
}
func init() {
if fips140.Enabled() {
defaultHostKeyAlgos = slices.DeleteFunc(defaultHostKeyAlgos, func(algo string) bool {
_, err := hashFunc(underlyingAlgo(algo))
return err != nil
})
defaultPubKeyAuthAlgos = slices.DeleteFunc(defaultPubKeyAuthAlgos, func(algo string) bool {
_, err := hashFunc(underlyingAlgo(algo))
return err != nil
})
}
}
func hashFunc(format string) (crypto.Hash, error) {
switch format {
case KeyAlgoRSASHA256, KeyAlgoECDSA256, KeyAlgoSKED25519, KeyAlgoSKECDSA256:
return crypto.SHA256, nil
case KeyAlgoECDSA384:
return crypto.SHA384, nil
case KeyAlgoRSASHA512, KeyAlgoECDSA521:
return crypto.SHA512, nil
case KeyAlgoED25519:
// KeyAlgoED25519 doesn't pre-hash.
return 0, nil
case KeyAlgoRSA, InsecureKeyAlgoDSA:
if fips140.Enabled() {
return 0, fmt.Errorf("ssh: hash algorithm for format %q not allowed in FIPS 140 mode", format)
}
return crypto.SHA1, nil
default:
return 0, fmt.Errorf("ssh: hash algorithm for format %q not mapped", format)
}
}
// SupportedAlgorithms returns algorithms currently implemented by this package,
// excluding those with security issues, which are returned by
// InsecureAlgorithms. The algorithms listed here are in preference order.
@@ -283,21 +318,6 @@ func InsecureAlgorithms() Algorithms {
var supportedCompressions = []string{compressionNone}
// hashFuncs keeps the mapping of supported signature algorithms to their
// respective hashes needed for signing and verification.
var hashFuncs = map[string]crypto.Hash{
KeyAlgoRSA: crypto.SHA1,
KeyAlgoRSASHA256: crypto.SHA256,
KeyAlgoRSASHA512: crypto.SHA512,
InsecureKeyAlgoDSA: crypto.SHA1,
KeyAlgoECDSA256: crypto.SHA256,
KeyAlgoECDSA384: crypto.SHA384,
KeyAlgoECDSA521: crypto.SHA512,
// KeyAlgoED25519 doesn't pre-hash.
KeyAlgoSKECDSA256: crypto.SHA256,
KeyAlgoSKED25519: crypto.SHA256,
}
// algorithmsForKeyFormat returns the supported signature algorithms for a given
// public key format (PublicKey.Type), in order of preference. See RFC 8332,
// Section 2. See also the note in sendKexInit on backwards compatibility.