From: Guus Sliepen <guus@tinc-vpn.org>
Date: Sat, 20 Jul 2013 22:13:38 +0000 (+0200)
Subject: Forbid protocol version rollback.
X-Git-Tag: release-1.1pre8~24
X-Git-Url: https://tinc-vpn.org/git/browse?p=tinc;a=commitdiff_plain;h=e82bec667059b370b0cfd5df2a34647b8f32829c

Forbid protocol version rollback.

When we know a node's ECDSA key, we only allow communication via the SPTPS
protocol.
---

diff --git a/src/protocol_auth.c b/src/protocol_auth.c
index 05724d6f..f8a3cc3b 100644
--- a/src/protocol_auth.c
+++ b/src/protocol_auth.c
@@ -324,7 +324,7 @@ bool id_h(connection_t *c, const char *request) {
 
 	if(c->protocol_major != myself->connection->protocol_major) {
 		logger(DEBUG_ALWAYS, LOG_ERR, "Peer %s (%s) uses incompatible version %d.%d",
-			   c->name, c->hostname, c->protocol_major, c->protocol_minor);
+			c->name, c->hostname, c->protocol_major, c->protocol_minor);
 		return false;
 	}
 
@@ -346,15 +346,21 @@ bool id_h(connection_t *c, const char *request) {
 			return false;
 		}
 
-		if(experimental && c->protocol_minor >= 2) {
-			if(!read_ecdsa_public_key(c))
-				return false;
-		}
+		if(experimental)
+			read_ecdsa_public_key(c);
 	} else {
 		if(c->protocol_minor && !ecdsa_active(c->ecdsa))
 			c->protocol_minor = 1;
 	}
 
+	/* Forbid version rollback for nodes whose ECDSA key we know */
+
+	if(ecdsa_active(c->ecdsa) && c->protocol_minor < 2) {
+		logger(DEBUG_ALWAYS, LOG_ERR, "Peer %s (%s) tries to roll back protocol version to %d.%d",
+			c->name, c->hostname, c->protocol_major, c->protocol_minor);
+		return false;
+	}
+
 	c->allow_request = METAKEY;
 
 	if(c->protocol_minor >= 2) {