added decryption step

include/header_encryption.h

@@ -18,8 +18,8 @@
 
 
 uint32_t packet_header_decrypt (uint8_t packet[], uint16_t packet_len,
-                                char * community_name, he_context_t * ctx);
+                                char * community_name, he_context_t * ctx,
-
+                                he_context_t * ctx_iv, uint16_t * checksum);
 
 int32_t packet_header_encrypt (uint8_t packet[], uint8_t header_len, he_context_t * ctx,
                                he_context_t * ctx_iv, uint16_t checksum);

src/edge_utils.c

@@ -1594,11 +1594,18 @@ static void readFromIPSocket(n2n_edge_t * eee, int in_sock) {
   traceEvent(TRACE_DEBUG, "### Rx N2N UDP (%d) from %s",
 	     (signed int)recvlen, sock_to_cstr(sockbuf1, &sender));
 
-  if(eee->conf.header_encryption == HEADER_ENCRYPTION_ENABLED)
+  if(eee->conf.header_encryption == HEADER_ENCRYPTION_ENABLED) {
-    if( packet_header_decrypt (udp_buf, recvlen, (char *)eee->conf.community_name, eee->conf.header_encryption_ctx) == 0) {
+    uint16_t checksum = 0;
+    if( packet_header_decrypt (udp_buf, recvlen, (char *)eee->conf.community_name, eee->conf.header_encryption_ctx,
+                               eee->conf.header_iv_ctx, &checksum) == 0) {
       traceEvent(TRACE_DEBUG, "readFromIPSocket failed to decrypt header.");
       return;
     }
+    if (checksum != pearson_hash_16 (udp_buf, recvlen)) {
+      traceEvent(TRACE_DEBUG, "readFromIPSocket dropped packet due to checksum error.");
+      return;
+    }
+  }
 
   /* hexdump(udp_buf, recvlen); */
 

src/header_encryption.c

@@ -24,7 +24,8 @@
 /* ********************************************************************** */
 
 uint32_t packet_header_decrypt (uint8_t packet[], uint16_t packet_len,
-			        char * community_name, he_context_t * ctx) {
+			        char * community_name, he_context_t * ctx,
+				he_context_t * ctx_iv, uint16_t * checksum) {
 
   // assemble IV
   // the last four are ASCII "n2n!" and do not get overwritten
@@ -34,6 +35,10 @@ uint32_t packet_header_decrypt (uint8_t packet[], uint16_t packet_len,
   // to full 128 bit IV
   memcpy (iv, packet, 12);
 
+  // extract checksum (last 16 bit) blended in IV
+  speck_he_iv_decrypt (packet, (speck_context_t*)ctx_iv);
+  *checksum = be16toh (((uint16_t*)packet)[5]);
+
   // try community name as possible key and check for magic bytes
   uint32_t magic = 0x6E326E00; // ="n2n_"
   uint32_t test_magic;

src/sn.c

@@ -491,7 +491,13 @@ static int process_udp(n2n_sn_t * sss,
       /* skip the definitely unencrypted communities */
       if (comm->header_encryption == HEADER_ENCRYPTION_NONE)
         continue;
-      if ( (ret = packet_header_decrypt (udp_buf, udp_size, comm->community, comm->header_encryption_ctx)) ) {
+      uint16_t checksum = 0;
+      if ( (ret = packet_header_decrypt (udp_buf, udp_size, comm->community, comm->header_encryption_ctx,
+                                         comm->header_iv_ctx, &checksum)) ) {
+        if (checksum != pearson_hash_16 (udp_buf, udp_size)) {
+          traceEvent(TRACE_DEBUG, "process_udp dropped packet due to checksum error.");
+          return -1;
+        }
         if (comm->header_encryption == HEADER_ENCRYPTION_UNKNOWN) {
 	  traceEvent (TRACE_INFO, "process_udp locked community '%s' to using "
                                   "encrypted headers.", comm->community);
@@ -650,7 +656,7 @@ static int process_udp(n2n_sn_t * sss,
 
 	/* Re-encode the header. */
 	encode_REGISTER(encbuf, &encx, &cmn2, &reg);
-// !!! does this ever happen? does REGISTER ever come with a payload ??? !!!
+
 	/* Copy the original payload unchanged */
 	encode_buf(encbuf, &encx, (udp_buf + idx), (udp_size - idx));
       } else {

src/sn_utils.c

@@ -417,7 +417,13 @@ static int process_udp(n2n_sn_t * sss,
       /* skip the definitely unencrypted communities */
       if (comm->header_encryption == HEADER_ENCRYPTION_NONE)
         continue;
-      if ( (ret = packet_header_decrypt (udp_buf, udp_size, comm->community, comm->header_encryption_ctx)) ) {
+      uint16_t checksum = 0;
+      if ( (ret = packet_header_decrypt (udp_buf, udp_size, comm->community, comm->header_encryption_ctx,
+                                         comm->header_iv_ctx, &checksum)) ) {
+       if (checksum != pearson_hash_16 (udp_buf, udp_size)) {
+          traceEvent(TRACE_DEBUG, "process_udp dropped packet due to checksum error.");
+          return -1;
+        }
         if (comm->header_encryption == HEADER_ENCRYPTION_UNKNOWN) {
 	  traceEvent (TRACE_INFO, "process_udp locked community '%s' to using "
                                   "encrypted headers.", comm->community);
@@ -577,7 +583,7 @@ static int process_udp(n2n_sn_t * sss,
 
 	/* Re-encode the header. */
 	encode_REGISTER(encbuf, &encx, &cmn2, &reg);
-// !!! does this ever happen? does REGISTER ever come with a payload ??? !!!
+
 	/* Copy the original payload unchanged */
 	encode_buf(encbuf, &encx, (udp_buf + idx), (udp_size - idx));
       } else {