Sign all handshake messages up to ECDHE kex with long-term public keys. (done)
- HMACed KEX finished message to prevent downgrade attacks and prove you have the right key material (done by virtue of ECDSA over the whole ECDHE exchange?)
+ HMACed KEX finished message to prevent downgrade attacks and prove you have the right key material (done by virtue of Ed25519 over the whole ECDHE exchange?)
Explicit close message needs to be added.
return send_record_priv(s, SPTPS_HANDSHAKE, s->mykex, 1 + 32 + keylen);
}
-// Send a SIGnature record, containing an ECDSA signature over both KEX records.
+// Send a SIGnature record, containing an Ed25519 signature over both KEX records.
static bool send_sig(sptps_t *s) {
size_t keylen = ECDH_SIZE;
size_t siglen = ecdsa_size(s->mykey);
}
}
+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