chiark / gitweb /
polypath asymmetric routing: Handle MSG2-4 late dupes
authorIan Jackson <ijackson@chiark.greenend.org.uk>
Wed, 15 May 2019 20:59:18 +0000 (21:59 +0100)
committerIan Jackson <ijackson@chiark.greenend.org.uk>
Sat, 18 May 2019 01:16:37 +0000 (02:16 +0100)
If we get a MSG2-4 and it seems too late for the protocol stage, and
it had the same nonces, it was probably an old packet via a different
route.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
site.c

diff --git a/site.c b/site.c
index 2bab3f7..9d922ce 100644 (file)
--- a/site.c
+++ b/site.c
@@ -1778,6 +1778,26 @@ static bool_t we_have_priority(struct site *st, const struct msg *m) {
     return st->our_name_later;
 }
 
+static bool_t setup_late_msg_ok(struct site *st, 
+                               const struct buffer_if *buf_in,
+                               uint32_t msgtype,
+                               const struct comm_addr *source) {
+    /* For setup packets which seem from their type like they are
+     * late.  Maybe they came via a different path.  All we do is make
+     * a note of the sending address, iff they look like they are part
+     * of the current key setup attempt. */
+    struct msg m;
+    if (!named_for_us(st,buf_in,msgtype,&m))
+       /* named_for_us calls unpick_msg which gets the nonces */
+       return False;
+    if (!consttime_memeq(m.nR,st->remoteN,NONCELEN) ||
+       !consttime_memeq(m.nL,st->localN, NONCELEN))
+       /* spoof ?  from stale run ?  who knows */
+       return False;
+    transport_setup_msgok(st,source);
+    return True;
+}
+
 /* This function is called by the communication device to deliver
    packets from our peers.
    It should return True if the packet is recognised as being for
@@ -1898,6 +1918,10 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
        case LABEL_MSG2:
            /* Setup packet: expected only in state SENTMSG1 */
            if (st->state!=SITE_SENTMSG1) {
+               if ((st->state==SITE_SENTMSG3 ||
+                    st->state==SITE_SENTMSG5) &&
+                   setup_late_msg_ok(st,buf,msgtype,source))
+                   break;
                slog(st,LOG_UNEXPECTED,"unexpected MSG2");
            } else if (process_msg2(st,buf,source)) {
                transport_setup_msgok(st,source);
@@ -1910,6 +1934,9 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
        case LABEL_MSG3BIS:
            /* Setup packet: expected only in state SENTMSG2 */
            if (st->state!=SITE_SENTMSG2) {
+               if ((st->state==SITE_SENTMSG4) &&
+                   setup_late_msg_ok(st,buf,msgtype,source))
+                   break;
                slog(st,LOG_UNEXPECTED,"unexpected MSG3");
            } else if (process_msg3(st,buf,source,msgtype)) {
                transport_setup_msgok(st,source);
@@ -1921,6 +1948,9 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
        case LABEL_MSG4:
            /* Setup packet: expected only in state SENTMSG3 */
            if (st->state!=SITE_SENTMSG3) {
+               if ((st->state==SITE_SENTMSG5) &&
+                   setup_late_msg_ok(st,buf,msgtype,source))
+                   break;
                slog(st,LOG_UNEXPECTED,"unexpected MSG4");
            } else if (process_msg4(st,buf,source)) {
                transport_setup_msgok(st,source);