Check fingerprint before checking password (server linking)

Checking the password before the fingerprint means that even without the
correct cert it's possible to brute force the password or leak
information about it. Checking the fingerprint means attackers must
forge the cert before they can learn any information about the password.

1 files changed, 15 insertions, 15 deletions

diff --git a/src/modules/m_spanningtree/hmac.cpp b/src/modules/m_spanningtree/hmac.cpp
index 895323a02..15cfbc37a 100644
--- a/src/modules/m_spanningtree/hmac.cpp
+++ b/src/modules/m_spanningtree/hmac.cpp
@@ -69,21 +69,6 @@ bool TreeSocket::ComparePass(const Link& link, const std::string &theirs)
 	capab->auth_fingerprint = !link.Fingerprint.empty();
 	capab->auth_challenge = !capab->ourchallenge.empty() && !capab->theirchallenge.empty();
 
-	if (capab->auth_challenge)
-	{
-		std::string our_hmac = MakePass(link.RecvPass, capab->ourchallenge);
-
-		/* Straight string compare of hashes */
-		if (our_hmac != theirs)
-			return false;
-	}
-	else
-	{
-		/* Straight string compare of plaintext */
-		if (link.RecvPass != theirs)
-			return false;
-	}
-
 	std::string fp = SSLClientCert::GetFingerprint(this);
 	if (capab->auth_fingerprint)
 	{
@@ -101,5 +86,20 @@ bool TreeSocket::ComparePass(const Link& link, const std::string &theirs)
 		ServerInstance->SNO->WriteToSnoMask('l', "SSL fingerprint for link %s is \"%s\". "
 			"You can improve security by specifying this in <link:fingerprint>.", link.Name.c_str(), fp.c_str());
 	}
+
+	if (capab->auth_challenge)
+	{
+		std::string our_hmac = MakePass(link.RecvPass, capab->ourchallenge);
+
+		/* Straight string compare of hashes */
+		if (our_hmac != theirs)
+			return false;
+	}
+	else
+	{
+		/* Straight string compare of plaintext */
+		if (link.RecvPass != theirs)
+			return false;
+	}
 	return true;
 }