Better log messages when we already know the peer's key during an upgrade.

If the peer presents a different one from the one we already know, log
an error. Otherwise, log an informational message, and terminate in the
same way as we would if we didn't already have that key.

diff --git a/src/protocol_auth.c b/src/protocol_auth.c
index 5782a97..84aece0 100644 (file)
--- a/src/protocol_auth.c
+++ b/src/protocol_auth.c
@@ -726,8 +726,16 @@ static bool upgrade_h(connection_t *c, const char *request) {
        }
 
        if(ecdsa_active(c->ecdsa) || read_ecdsa_public_key(c)) {
-               logger(DEBUG_ALWAYS, LOG_INFO, "Already have Ed25519 public key from %s (%s), not upgrading.", c->name, c->hostname);
-               return false;
+               char *knownkey = ecdsa_get_base64_public_key(c->ecdsa);
+               bool different = strcmp(knownkey, pubkey);
+               free(knownkey);
+               if(different) {
+                       logger(DEBUG_ALWAYS, LOG_ERR, "Already have an Ed25519 public key from %s (%s) which is different from the one presented now!", c->name, c->hostname);
+                       return false;
+               }
+               logger(DEBUG_ALWAYS, LOG_INFO, "Already have Ed25519 public key from %s (%s), ignoring.", c->name, c->hostname);
+               c->allow_request = TERMREQ;
+               return send_termreq(c);
        }
 
        c->ecdsa = ecdsa_set_base64_public_key(pubkey);