Only allow keys configured on a given interface.

We used to accept packets signed by any key.

hmac.c

@@ -242,26 +242,20 @@ add_hmac(struct buffered *buf, struct interface *ifp,
 static int
 compare_hmac(const unsigned char *src, const unsigned char *dst,
              const unsigned char *packet, int bodylen,
-             const unsigned char *hmac, int hmaclen)
+             const unsigned char *hmac, int hmaclen,
+             struct key *key)
 {
-    unsigned char true_hmac[MAX_DIGEST_LEN];
-    int true_hmaclen;
-    int i;
-    for(i = 0; i < numkeys; i++) {
-        true_hmaclen = compute_hmac(src, dst, packet,
-                                    packet + 4, bodylen, keys[i],
-                                    true_hmac);
-        if(true_hmaclen != hmaclen)
-            continue;
-        if(memcmp(true_hmac, hmac, hmaclen) == 0)
-            return 1;
-    }
-    return 0;
+    unsigned char buf[MAX_DIGEST_LEN];
+    int len;
+
+    len = compute_hmac(src, dst, packet, packet + 4, bodylen, key, buf);
+    return len == hmaclen && (memcmp(buf, hmac, hmaclen) == 0);
 }
 
 int
 check_hmac(const unsigned char *packet, int packetlen, int bodylen,
-           const unsigned char *src, const unsigned char *dst)
+           const unsigned char *src, const unsigned char *dst,
+           struct interface *ifp)
 {
     int i = bodylen + 4;
     int len;
@@ -275,14 +269,15 @@ check_hmac(const unsigned char *packet, int packetlen, int bodylen,
         }
         len = packet[i + 1];
         if(packet[i] == MESSAGE_HMAC) {
+            int ok;
             if(i + len + 2 > packetlen) {
                 fprintf(stderr, "Received truncated message.\n");
                 return -1;
             }
-            if(compare_hmac(src, dst, packet, bodylen,
-                            packet + i + 2 , len) == 1) {
+            ok = compare_hmac(src, dst, packet, bodylen,
+                              packet + i + 2, len, ifp->key);
+            if(ok)
                 return 1;
-            }
         }
         i += len + 2;
     }

hmac.h

@@ -29,4 +29,5 @@ struct key *add_key(char *id, int type, int len, unsigned char *value);
 int add_hmac(struct buffered *buf, struct interface *ifp,
              unsigned char *packet_header);
 int check_hmac(const unsigned char *packet, int packetlen, int bodylen,
-               const unsigned char *src, const unsigned char *dst);
+               const unsigned char *src, const unsigned char *dst,
+               struct interface *ifp);

message.c

@@ -588,7 +588,7 @@ parse_packet(const unsigned char *from, struct interface *ifp,
     }
 
     if(ifp->key != NULL && !(ifp->flags & IF_NO_HMAC_VERIFY)) {
-        if(check_hmac(packet, packetlen, bodylen, from, to) != 1) {
+        if(check_hmac(packet, packetlen, bodylen, from, to, ifp) != 1) {
             fprintf(stderr, "Received wrong hmac.\n");
             return;
         }