}
}
+static bool sptps_check_seqno(sptps_t *s, uint32_t seqno, bool update_state) {
+ // Replay protection using a sliding window of configurable size.
+ // s->inseqno is expected sequence number
+ // seqno is received sequence number
+ // s->late[] is a circular buffer, a 1 bit means a packet has not been received yet
+ // The circular buffer contains bits for sequence numbers from s->inseqno - s->replaywin * 8 to (but excluding) s->inseqno.
+ if(s->replaywin) {
+ if(seqno != s->inseqno) {
+ if(seqno >= s->inseqno + s->replaywin * 8) {
+ // Prevent packets that jump far ahead of the queue from causing many others to be dropped.
+ bool farfuture = s->farfuture < s->replaywin >> 2;
+ if (update_state)
+ s->farfuture++;
+ if(farfuture)
+ return error(s, EIO, "Packet is %d seqs in the future, dropped (%u)\n", seqno - s->inseqno, s->farfuture);
+
+ // Unless we have seen lots of them, in which case we consider the others lost.
+ warning(s, "Lost %d packets\n", seqno - s->inseqno);
+ if (update_state) {
+ // Mark all packets in the replay window as being late.
+ memset(s->late, 255, s->replaywin);
+ }
+ } else if (seqno < s->inseqno) {
+ // If the sequence number is farther in the past than the bitmap goes, or if the packet was already received, drop it.
+ if((s->inseqno >= s->replaywin * 8 && seqno < s->inseqno - s->replaywin * 8) || !(s->late[(seqno / 8) % s->replaywin] & (1 << seqno % 8)))
+ return error(s, EIO, "Received late or replayed packet, seqno %d, last received %d\n", seqno, s->inseqno);
+ } else if (update_state) {
+ // We missed some packets. Mark them in the bitmap as being late.
+ for(int i = s->inseqno; i < seqno; i++)
+ s->late[(i / 8) % s->replaywin] |= 1 << i % 8;
+ }
+ }
+
+ if (update_state) {
+ // Mark the current packet as not being late.
+ s->late[(seqno / 8) % s->replaywin] &= ~(1 << seqno % 8);
+ s->farfuture = 0;
+ }
+ }
+
+ if (update_state) {
+ if(seqno >= s->inseqno)
+ s->inseqno = seqno + 1;
+
+ if(!s->inseqno)
+ s->received = 0;
+ else
+ s->received++;
+ }
+
+ return true;
+}
+
// Check datagram for valid HMAC
bool sptps_verify_datagram(sptps_t *s, const char *data, size_t len) {
if(!s->instate || len < 21)
return error(s, EIO, "Received short packet");
- // TODO: just decrypt without updating the replay window
+ uint32_t seqno;
+ memcpy(&seqno, data, 4);
+ seqno = ntohl(seqno);
- return true;
+ char buffer[len];
+ size_t outlen;
+ if(!chacha_poly1305_decrypt(s->incipher, seqno, data + 4, len - 4, buffer, &outlen))
+ return false;
+
+ return sptps_check_seqno(s, seqno, false);
}
// Receive incoming data, datagram version.
if(!chacha_poly1305_decrypt(s->incipher, seqno, data + 4, len - 4, buffer, &outlen))
return error(s, EIO, "Failed to decrypt and verify packet");
- // Replay protection using a sliding window of configurable size.
- // s->inseqno is expected sequence number
- // seqno is received sequence number
- // s->late[] is a circular buffer, a 1 bit means a packet has not been received yet
- // The circular buffer contains bits for sequence numbers from s->inseqno - s->replaywin * 8 to (but excluding) s->inseqno.
- if(s->replaywin) {
- if(seqno != s->inseqno) {
- if(seqno >= s->inseqno + s->replaywin * 8) {
- // Prevent packets that jump far ahead of the queue from causing many others to be dropped.
- if(s->farfuture++ < s->replaywin >> 2)
- return error(s, EIO, "Packet is %d seqs in the future, dropped (%u)\n", seqno - s->inseqno, s->farfuture);
-
- // Unless we have seen lots of them, in which case we consider the others lost.
- warning(s, "Lost %d packets\n", seqno - s->inseqno);
- // Mark all packets in the replay window as being late.
- memset(s->late, 255, s->replaywin);
- } else if (seqno < s->inseqno) {
- // If the sequence number is farther in the past than the bitmap goes, or if the packet was already received, drop it.
- if((s->inseqno >= s->replaywin * 8 && seqno < s->inseqno - s->replaywin * 8) || !(s->late[(seqno / 8) % s->replaywin] & (1 << seqno % 8)))
- return error(s, EIO, "Received late or replayed packet, seqno %d, last received %d\n", seqno, s->inseqno);
- } else {
- // We missed some packets. Mark them in the bitmap as being late.
- for(int i = s->inseqno; i < seqno; i++)
- s->late[(i / 8) % s->replaywin] |= 1 << i % 8;
- }
- }
-
- // Mark the current packet as not being late.
- s->late[(seqno / 8) % s->replaywin] &= ~(1 << seqno % 8);
- s->farfuture = 0;
- }
-
- if(seqno >= s->inseqno)
- s->inseqno = seqno + 1;
-
- if(!s->inseqno)
- s->received = 0;
- else
- s->received++;
+ if(!sptps_check_seqno(s, seqno, true))
+ return false;
// Append a NULL byte for safety.
buffer[len - 20] = 0;
projects / tinc / blobdiff