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dtls.c: cleanup record_sequence_filter. #117

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Merged
obgm merged 1 commit into from
Feb 22, 2022
Merged

dtls.c: cleanup record_sequence_filter. #117

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8 changes: 7 additions & 1 deletion crypto.h
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Original file line number Diff line number Diff line change
Expand Up @@ -92,7 +92,13 @@ typedef struct {
} dtls_handshake_parameters_psk_t;

typedef struct {
uint64_t cseq;
uint64_t cseq; /**< current read sequence number */
/**
* bitfield of already received sequence numbers.
* B0 := cseqn, B1 := cseqn -1, ..., B63 := cseqn - 63
* Initially 0, set to 1 (B0) with the first received message of the epoch,
* or -1 (B0..B63) with a verified ClientHello (server-side only)
*/
uint64_t bitfield;
} seqnum_t;

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79 changes: 43 additions & 36 deletions dtls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4249,48 +4249,55 @@ dtls_handle_message(dtls_context_t *ctx,
dtls_warn("No security context for epoch: %i\n", epoch);
data_length = -1;
} else {
if(pkt_seq_nr == 0 && security->cseq.cseq == 0) {
dtls_debug("bitfield is %" PRIx64 " sequence base %" PRIx64 " rseqn %" PRIx64 "\n",
security->cseq.bitfield, security->cseq.cseq, pkt_seq_nr);
if (security->cseq.bitfield == 0) { /* first message of epoch */
data_length = decrypt_verify(peer, msg, rlen, &data);
if (data_length > 0) {
security->cseq.cseq = 0;
/* bitfield. B0 last seq seen. B1 seq-1 seen, B2 seq-2 seen etc. */
security->cseq.bitfield = 1;
if(data_length > 0) {
security->cseq.cseq = pkt_seq_nr;
security->cseq.bitfield = 1;
dtls_debug("init bitfield is %" PRIx64 " sequence base %" PRIx64 "\n",
security->cseq.bitfield, security->cseq.cseq);
}
} else if (pkt_seq_nr == security->cseq.cseq) {
dtls_info("Duplicate packet arrived (cseq=%" PRIu64 ")\n", security->cseq.cseq);
return 0;
} else if ((int64_t)(security->cseq.cseq-pkt_seq_nr) > 0) { /* pkt_seq_nr < security->cseq.cseq */
if (((security->cseq.cseq-1)-pkt_seq_nr) < 64) {
if(security->cseq.bitfield & ((uint64_t)1<<((security->cseq.cseq-1)-pkt_seq_nr))) {
dtls_info("Duplicate packet arrived (bitfield)\n");
/* seen it */
} else {
int64_t seqn_diff = (int64_t)(pkt_seq_nr - security->cseq.cseq);
if(seqn_diff == 0) {
/* already seen */
dtls_debug("Drop: duplicate packet arrived (cseq=%" PRIu64 " bitfield's start)\n", pkt_seq_nr);
return 0;
} else if (seqn_diff < 0) { /* older pkt_seq_nr < security->cseq.cseq */
if (seqn_diff < -63) { /* too old */
dtls_debug("Drop: packet from before the bitfield arrived\n");
return 0;
} else {
dtls_info("Packet arrived out of order\n");
data_length = decrypt_verify(peer, msg, rlen, &data);
if(data_length > 0) {
security->cseq.bitfield |= ((uint64_t)1<<((security->cseq.cseq-1)-pkt_seq_nr));
}
}
} else {
dtls_info("Packet from before the bitfield arrived\n");
uint64_t seqn_bit = ((uint64_t)1 << -seqn_diff);
if (security->cseq.bitfield & seqn_bit) { /* seen it */
dtls_debug("Drop: duplicate packet arrived (bitfield)\n");
return 0;
}
} else { /* pkt_seq_nr > security->cseq.cseq */
data_length = decrypt_verify(peer, msg, rlen, &data);
if(data_length > 0) {
if (pkt_seq_nr - security->cseq.cseq > 63) {
/* reset bitfield if new packet number is beyond its boundaries */
security->cseq.bitfield = 0;
} else {
/* shift bitfield */
security->cseq.bitfield <<= (pkt_seq_nr-security->cseq.cseq);
}
security->cseq.bitfield |= 1;
/* bitfield. B0 last seq seen. B1 seq-1 seen, B2 seq-2 seen etc. */
security->cseq.cseq = pkt_seq_nr;
dtls_debug("new bitfield is %" PRIx64 " sequence base %" PRIx64 "\n",
security->cseq.bitfield, security->cseq.cseq);
dtls_debug("Packet arrived out of order\n");
data_length = decrypt_verify(peer, msg, rlen, &data);
if(data_length > 0) {
security->cseq.bitfield |= seqn_bit;
dtls_debug("update bitfield is %" PRIx64 " keep sequence base %" PRIx64 "\n",
security->cseq.bitfield, security->cseq.cseq);
}
} else { /* newer pkt_seq_nr > security->cseq.cseq */
data_length = decrypt_verify(peer, msg, rlen, &data);
if(data_length > 0) {
security->cseq.cseq = pkt_seq_nr;
/* bitfield. B0 last seq seen. B1 seq-1 seen, B2 seq-2 seen etc. */
if (seqn_diff > 63) {
/* reset bitfield if new packet number is beyond its boundaries */
security->cseq.bitfield = 1;
} else {
/* shift bitfield */
security->cseq.bitfield <<= seqn_diff;
security->cseq.bitfield |= 1;
}
dtls_debug("update bitfield is %" PRIx64 " new sequence base %" PRIx64 "\n",
security->cseq.bitfield, security->cseq.cseq);
}
}
}
}
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