ssh: validate key type in SSH_MSG_USERAUTH_PK_OK response
According to RFC 4252 Section 7 the algorithm in SSH_MSG_USERAUTH_PK_OK
should match that of the request but some servers send the key type instead.
OpenSSH checks for the key type, so we do the same.
Fixes golang/go#66438
Fixes golang/go#64785
Fixes golang/go#56342
Fixes golang/go#54027
Change-Id: I2f733f0faece097e44ba7a97c868d30a53e21d79
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/573360
Auto-Submit: Nicola Murino <nicola.murino@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Run-TryBot: Nicola Murino <nicola.murino@gmail.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Joedian Reid <joedian@google.com>
diff --git a/ssh/client_auth.go b/ssh/client_auth.go
index 34bf089..9486c59 100644
--- a/ssh/client_auth.go
+++ b/ssh/client_auth.go
@@ -404,10 +404,10 @@
return false, err
}
- return confirmKeyAck(key, algo, c)
+ return confirmKeyAck(key, c)
}
-func confirmKeyAck(key PublicKey, algo string, c packetConn) (bool, error) {
+func confirmKeyAck(key PublicKey, c packetConn) (bool, error) {
pubKey := key.Marshal()
for {
@@ -425,7 +425,15 @@
if err := Unmarshal(packet, &msg); err != nil {
return false, err
}
- if msg.Algo != algo || !bytes.Equal(msg.PubKey, pubKey) {
+ // According to RFC 4252 Section 7 the algorithm in
+ // SSH_MSG_USERAUTH_PK_OK should match that of the request but some
+ // servers send the key type instead. OpenSSH allows any algorithm
+ // that matches the public key, so we do the same.
+ // https://github.com/openssh/openssh-portable/blob/86bdd385/sshconnect2.c#L709
+ if !contains(algorithmsForKeyFormat(key.Type()), msg.Algo) {
+ return false, nil
+ }
+ if !bytes.Equal(msg.PubKey, pubKey) {
return false, nil
}
return true, nil
