vendor: bump golang.org/x/crypto bac4c82f6975 (CVE-2020-9283)

full diff: 1d94cc7ab1...bac4c82f69

Version v0.0.0-20200220183623-bac4c82f6975 of golang.org/x/crypto fixes a
vulnerability in the golang.org/x/crypto/ssh package which allowed peers to
cause a panic in SSH servers that accept public keys and in any SSH client.

An attacker can craft an ssh-ed25519 or sk-ssh-ed25519@openssh.com public
key, such that the library will panic when trying to verify a signature
with it. Clients can deliver such a public key and signature to any
golang.org/x/crypto/ssh server with a PublicKeyCallback, and servers can
deliver them to any golang.org/x/crypto/ssh client.

This issue was discovered and reported by Alex Gaynor, Fish in a Barrel,
and is tracked as CVE-2020-9283.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor.conf

@@ -72,7 +72,7 @@ github.com/tonistiigi/units                         6950e57a87eaf136bbe44ef2ec8e
 github.com/xeipuuv/gojsonpointer                    02993c407bfbf5f6dae44c4f4b1cf6a39b5fc5bb
 github.com/xeipuuv/gojsonreference                  bd5ef7bd5415a7ac448318e64f11a24cd21e594b
 github.com/xeipuuv/gojsonschema                     f971f3cd73b2899de6923801c147f075263e0c50 # v1.1.0
-golang.org/x/crypto                                 1d94cc7ab1c630336ab82ccb9c9cda72a875c382
+golang.org/x/crypto                                 bac4c82f69751a6dd76e702d54b3ceb88adab236
 golang.org/x/net                                    f3200d17e092c607f615320ecaad13d87ad9a2b3
 golang.org/x/oauth2                                 ef147856a6ddbb60760db74283d2424e98c87bff
 golang.org/x/sync                                   e225da77a7e68af35c70ccbf71af2b83e6acac3c

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

@@ -562,9 +562,11 @@ func parseED25519(in []byte) (out PublicKey, rest []byte, err error) {
 		return nil, nil, err
 	}
 
-	key := ed25519.PublicKey(w.KeyBytes)
+	if l := len(w.KeyBytes); l != ed25519.PublicKeySize {
+		return nil, nil, fmt.Errorf("invalid size %d for Ed25519 public key", l)
+	}
 
-	return (ed25519PublicKey)(key), w.Rest, nil
+	return ed25519PublicKey(w.KeyBytes), w.Rest, nil
 }
 
 func (k ed25519PublicKey) Marshal() []byte {
@@ -582,9 +584,11 @@ func (k ed25519PublicKey) Verify(b []byte, sig *Signature) error {
 	if sig.Format != k.Type() {
 		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
 	}
+	if l := len(k); l != ed25519.PublicKeySize {
+		return fmt.Errorf("ssh: invalid size %d for Ed25519 public key", l)
+	}
 
-	edKey := (ed25519.PublicKey)(k)
+	if ok := ed25519.Verify(ed25519.PublicKey(k), b, sig.Blob); !ok {
-	if ok := ed25519.Verify(edKey, b, sig.Blob); !ok {
 		return errors.New("ssh: signature did not verify")
 	}
 
@@ -838,6 +842,10 @@ func parseSKEd25519(in []byte) (out PublicKey, rest []byte, err error) {
 		return nil, nil, err
 	}
 
+	if l := len(w.KeyBytes); l != ed25519.PublicKeySize {
+		return nil, nil, fmt.Errorf("invalid size %d for Ed25519 public key", l)
+	}
+
 	key := new(skEd25519PublicKey)
 	key.application = w.Application
 	key.PublicKey = ed25519.PublicKey(w.KeyBytes)
@@ -862,6 +870,9 @@ func (k *skEd25519PublicKey) Verify(data []byte, sig *Signature) error {
 	if sig.Format != k.Type() {
 		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
 	}
+	if l := len(k.PublicKey); l != ed25519.PublicKeySize {
+		return fmt.Errorf("invalid size %d for Ed25519 public key", l)
+	}
 
 	h := sha256.New()
 	h.Write([]byte(k.application))
@@ -898,8 +909,7 @@ func (k *skEd25519PublicKey) Verify(data []byte, sig *Signature) error {
 
 	original := Marshal(blob)
 
-	edKey := (ed25519.PublicKey)(k.PublicKey)
+	if ok := ed25519.Verify(k.PublicKey, original, edSig.Signature); !ok {
-	if ok := ed25519.Verify(edKey, original, edSig.Signature); !ok {
 		return errors.New("ssh: signature did not verify")
 	}
 
@@ -1051,7 +1061,10 @@ func NewPublicKey(key interface{}) (PublicKey, error) {
 	case *dsa.PublicKey:
 		return (*dsaPublicKey)(key), nil
 	case ed25519.PublicKey:
-		return (ed25519PublicKey)(key), nil
+		if l := len(key); l != ed25519.PublicKeySize {
+			return nil, fmt.Errorf("ssh: invalid size %d for Ed25519 public key", l)
+		}
+		return ed25519PublicKey(key), nil
 	default:
 		return nil, fmt.Errorf("ssh: unsupported key type %T", key)
 	}
@@ -1304,7 +1317,6 @@ func parseOpenSSHPrivateKey(key []byte, decrypt openSSHDecryptFunc) (crypto.Priv
 		return nil, errors.New("ssh: malformed OpenSSH key")
 	}
 
-	// we only handle ed25519 and rsa keys currently
 	switch pk1.Keytype {
 	case KeyAlgoRSA:
 		// https://github.com/openssh/openssh-portable/blob/master/sshkey.c#L2760-L2773