commit 62797ee85f11f61a490092e0fde0a92c7b71b8ed
author Jannis Konrad <Jannis.Konrad@h-brs.de> Thu Nov 17 14:59:27 2016 +0100
committer Olaf Bergmann <bergmann@tzi.org> Tue Feb 28 05:29:55 2017 -0400
tree 8858414a6cdf03cf152dcba56c50ccc5d9df2055
parent f11270a00e6b51cf541a53e2edf84de3335f3cda

check sequence Numbers of received messages

Signed-off-by: Jannis Konrad <jannis.Konrad@h-brs.de>

crypto.h

diff --git a/crypto.h b/crypto.h
index f319109..b0b7d56 100644
--- a/crypto.h
+++ b/crypto.h
@@ -87,6 +87,11 @@
 } dtls_handshake_parameters_psk_t;
 
 typedef struct {
+    uint64_t cseq;
+    uint64_t bitfield;
+} seqnum_t;
+
+typedef struct {
   dtls_compression_t compression;	/**< compression method */
 
   dtls_cipher_t cipher;		/**< cipher type */
@@ -100,6 +105,8 @@
    * access the components of the key block.
    */
   uint8 key_block[MAX_KEYBLOCK_LENGTH];
+  
+  seqnum_t cseq;        /**<sequence number of last record received*/
 } dtls_security_parameters_t;
 
 struct netq_t;

dtls.c

diff --git a/dtls.c b/dtls.c
index 3e9b285..2da67f8 100644
--- a/dtls.c
+++ b/dtls.c
@@ -3662,7 +3662,51 @@
 
     dtls_debug("got packet %d (%d bytes)\n", msg[0], rlen);
     if (peer) {
-      data_length = decrypt_verify(peer, msg, rlen, &data);
+      dtls_record_header_t *header = DTLS_RECORD_HEADER(msg);
+      
+      dtls_security_parameters_t *security = dtls_security_params_epoch(peer, dtls_get_epoch(header));
+      if (!security) {
+        dtls_alert("No security context for epoch: %i\n", dtls_get_epoch(header));
+        data_length = -1;
+      } else {
+        uint64_t pkt_seq_nr = dtls_uint48_to_int(header->sequence_number);
+        if(pkt_seq_nr == 0 && security->cseq.cseq == 0) {
+          data_length = decrypt_verify(peer, msg, rlen, &data);
+          if (data_length) {
+            security->cseq.cseq = 0;
+            security->cseq.bitfield = -1;
+          }
+        } else if (pkt_seq_nr == security->cseq.cseq) {
+          dtls_info("Duplicate packet arrived (cseq=%llu)\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 & (1<<((security->cseq.cseq-1)-pkt_seq_nr))) {
+                dtls_info("Duplicate packet arrived (bitfield)\n");
+                //seen it
+                  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 |= (1<<((security->cseq.cseq-1)-pkt_seq_nr));
+                }
+              }
+          } else {
+            dtls_info("Packet from before the bitfield arrived\n");
+              return 0;
+          }
+        } else { //pkt_seq_nr > security->cseq.cseq
+          data_length = decrypt_verify(peer, msg, rlen, &data);
+          if(data_length > 0) {
+            security->cseq.bitfield <<= (pkt_seq_nr-security->cseq.cseq);
+            security->cseq.bitfield |= 1<<((pkt_seq_nr-security->cseq.cseq)-1);
+            security->cseq.cseq = pkt_seq_nr;
+            dtls_debug("new packet arrived with seqNr: %llu\n", pkt_seq_nr);
+            dtls_debug("new bitfield is              : %llx\n", security->cseq.bitfield);
+          }
+        }
+      }
       if (data_length < 0) {
         if (hs_attempt_with_existing_peer(msg, rlen, peer)) {
           data = msg + DTLS_RH_LENGTH;