Bump golang.org/x/crypto from 0.25.0 to 0.31.0

Bumps [golang.org/x/crypto](https://github.com/golang/crypto) from 0.25.0 to 0.31.0.
- [Commits](https://github.com/golang/crypto/compare/v0.25.0...v0.31.0)

---
updated-dependencies:
- dependency-name: golang.org/x/crypto
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/golang.org/x/crypto/ssh/client_auth.go

@@ -555,6 +555,7 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 	}
 
 	gotMsgExtInfo := false
+	gotUserAuthInfoRequest := false
 	for {
 		packet, err := c.readPacket()
 		if err != nil {
@@ -585,6 +586,9 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 			if msg.PartialSuccess {
 				return authPartialSuccess, msg.Methods, nil
 			}
+			if !gotUserAuthInfoRequest {
+				return authFailure, msg.Methods, unexpectedMessageError(msgUserAuthInfoRequest, packet[0])
+			}
 			return authFailure, msg.Methods, nil
 		case msgUserAuthSuccess:
 			return authSuccess, nil, nil
@@ -596,6 +600,7 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		if err := Unmarshal(packet, &msg); err != nil {
 			return authFailure, nil, err
 		}
+		gotUserAuthInfoRequest = true
 
 		// Manually unpack the prompt/echo pairs.
 		rest := msg.Prompts

vendor/golang.org/x/crypto/ssh/keys.go

@@ -488,7 +488,49 @@ func (r *rsaPublicKey) Verify(data []byte, sig *Signature) error {
 	h := hash.New()
 	h.Write(data)
 	digest := h.Sum(nil)
-	return rsa.VerifyPKCS1v15((*rsa.PublicKey)(r), hash, digest, sig.Blob)
+
+	// Signatures in PKCS1v15 must match the key's modulus in
+	// length. However with SSH, some signers provide RSA
+	// signatures which are missing the MSB 0's of the bignum
+	// represented. With ssh-rsa signatures, this is encouraged by
+	// the spec (even though e.g. OpenSSH will give the full
+	// length unconditionally). With rsa-sha2-* signatures, the
+	// verifier is allowed to support these, even though they are
+	// out of spec. See RFC 4253 Section 6.6 for ssh-rsa and RFC
+	// 8332 Section 3 for rsa-sha2-* details.
+	//
+	// In practice:
+	// * OpenSSH always allows "short" signatures:
+	//   https://github.com/openssh/openssh-portable/blob/V_9_8_P1/ssh-rsa.c#L526
+	//   but always generates padded signatures:
+	//   https://github.com/openssh/openssh-portable/blob/V_9_8_P1/ssh-rsa.c#L439
+	//
+	// * PuTTY versions 0.81 and earlier will generate short
+	//   signatures for all RSA signature variants. Note that
+	//   PuTTY is embedded in other software, such as WinSCP and
+	//   FileZilla. At the time of writing, a patch has been
+	//   applied to PuTTY to generate padded signatures for
+	//   rsa-sha2-*, but not yet released:
+	//   https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=a5bcf3d384e1bf15a51a6923c3724cbbee022d8e
+	//
+	// * SSH.NET versions 2024.0.0 and earlier will generate short
+	//   signatures for all RSA signature variants, fixed in 2024.1.0:
+	//   https://github.com/sshnet/SSH.NET/releases/tag/2024.1.0
+	//
+	// As a result, we pad these up to the key size by inserting
+	// leading 0's.
+	//
+	// Note that support for short signatures with rsa-sha2-* may
+	// be removed in the future due to such signatures not being
+	// allowed by the spec.
+	blob := sig.Blob
+	keySize := (*rsa.PublicKey)(r).Size()
+	if len(blob) < keySize {
+		padded := make([]byte, keySize)
+		copy(padded[keySize-len(blob):], blob)
+		blob = padded
+	}
+	return rsa.VerifyPKCS1v15((*rsa.PublicKey)(r), hash, digest, blob)
 }
 
 func (r *rsaPublicKey) CryptoPublicKey() crypto.PublicKey {

vendor/golang.org/x/crypto/ssh/server.go

@@ -149,7 +149,7 @@ func (s *ServerConfig) AddHostKey(key Signer) {
 }
 
 // cachedPubKey contains the results of querying whether a public key is
-// acceptable for a user.
+// acceptable for a user. This is a FIFO cache.
 type cachedPubKey struct {
 	user       string
 	pubKeyData []byte
@@ -157,7 +157,13 @@ type cachedPubKey struct {
 	perms      *Permissions
 }
 
-const maxCachedPubKeys = 16
+// maxCachedPubKeys is the number of cache entries we store.
+//
+// Due to consistent misuse of the PublicKeyCallback API, we have reduced this
+// to 1, such that the only key in the cache is the most recently seen one. This
+// forces the behavior that the last call to PublicKeyCallback will always be
+// with the key that is used for authentication.
+const maxCachedPubKeys = 1
 
 // pubKeyCache caches tests for public keys.  Since SSH clients
 // will query whether a public key is acceptable before attempting to
@@ -179,9 +185,10 @@ func (c *pubKeyCache) get(user string, pubKeyData []byte) (cachedPubKey, bool) {
 
 // add adds the given tuple to the cache.
 func (c *pubKeyCache) add(candidate cachedPubKey) {
-	if len(c.keys) < maxCachedPubKeys {
-		c.keys = append(c.keys, candidate)
+	if len(c.keys) >= maxCachedPubKeys {
+		c.keys = c.keys[1:]
 	}
+	c.keys = append(c.keys, candidate)
 }
 
 // ServerConn is an authenticated SSH connection, as seen from the
@@ -510,8 +517,8 @@ userAuthLoop:
 			if err := s.transport.writePacket(Marshal(discMsg)); err != nil {
 				return nil, err
 			}
-
-			return nil, discMsg
+			authErrs = append(authErrs, discMsg)
+			return nil, &ServerAuthError{Errors: authErrs}
 		}
 
 		var userAuthReq userAuthRequestMsg