TCAP: fix SRT analysis

When reviewing the code, the following issues were identified:
- otid/dtid on 3 bytes were not stored
- when receiving the first continue from dest, the TC_END hash entry was
created with the source tid / address instead of destination ones
- when receiving the first continue from src, the logic could prevent
the creation of the hash entry

Bug: 13739
Change-Id: If4ee70f0fa69f5ff74fdf75f3a741102baa0121a
Reviewed-on: https://code.wireshark.org/review/21780
Petri-Dish: Pascal Quantin <pascal.quantin@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
Reviewed-by: Michael Mann <mmann78@netscape.net>

2 files changed, 18 insertions, 5 deletions

diff --git a/epan/dissectors/asn1/tcap/packet-tcap-template.c b/epan/dissectors/asn1/tcap/packet-tcap-template.c
index 24e3f58b11..576f78da9d 100644
--- a/epan/dissectors/asn1/tcap/packet-tcap-template.c
+++ b/epan/dissectors/asn1/tcap/packet-tcap-template.c
@@ -1036,6 +1036,7 @@ tcaphash_cont_matching(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
   proto_item *pi;
   proto_item *stat_item=NULL;
   proto_tree *stat_tree=NULL;
+  gboolean use_dst = TRUE;
 
 #ifdef DEBUG_TCAPSRT
   dbg(51,"src %s srcTid %lx dst %s dstTid %lx ", address_to_str(wmem_packet_scope(), &pinfo->src), p_tcapsrt_info->src_tid, address_to_str(wmem_packet_scope(), &pinfo->dst), p_tcapsrt_info->dst_tid);
@@ -1091,11 +1092,13 @@ tcaphash_cont_matching(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
 #endif
     p_tcaphash_begincall = find_tcaphash_begin(&tcaphash_begin_key, pinfo, FALSE);
     if(!p_tcaphash_begincall){
+      try_src:
 /* can this actually happen? */
 #ifdef DEBUG_TCAPSRT
         dbg(12,"BNotFound trying stid,src");
 #endif
         /* Do we have a continue from the same source? (stid,src) */
+        use_dst = FALSE;
         tcaphash_begin_key.tid = p_tcapsrt_info->src_tid;
         if (pinfo->src.type == ss7pc_address_type && pinfo->dst.type == ss7pc_address_type)
         {
@@ -1128,21 +1131,21 @@ tcaphash_cont_matching(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
       create_tcaphash_cont(&tcaphash_cont_key,
                            p_tcaphash_begincall->context);
 
-      /* Create END for (stid,src) */
-      tcaphash_end_key.tid = p_tcapsrt_info->src_tid;
+      /* Create END for (dtid,dst) or (stid,src) */
+      tcaphash_end_key.tid = use_dst ? p_tcapsrt_info->dst_tid : p_tcapsrt_info->src_tid;
       if (pinfo->src.type == ss7pc_address_type && pinfo->dst.type == ss7pc_address_type)
       {
         /* We have MTP3 PCs (so we can safely do this cast) */
-        tcaphash_end_key.pc_hash = mtp3_pc_hash((const mtp3_addr_pc_t *)pinfo->src.data);
+        tcaphash_end_key.pc_hash = mtp3_pc_hash((const mtp3_addr_pc_t *)(use_dst ? pinfo->dst.data : pinfo->src.data));
       } else {
         /* Don't have MTP3 PCs (have SCCP GT ?) */
-        tcaphash_end_key.pc_hash = g_str_hash(address_to_str(wmem_packet_scope(), &pinfo->src));
+        tcaphash_end_key.pc_hash = g_str_hash(address_to_str(wmem_packet_scope(), use_dst ? &pinfo->dst : &pinfo->src));
       }
       tcaphash_end_key.hashKey=tcaphash_end_calchash(&tcaphash_end_key);
 
 #ifdef DEBUG_TCAPSRT
       dbg(10,"New Ekey %lx ",tcaphash_end_key.hashKey);
-      dbg(51,"addr %s ", address_to_str(wmem_packet_scope(), &pinfo->src));
+      dbg(51,"addr %s ", address_to_str(wmem_packet_scope(), use_dst ? &pinfo->dst : &pinfo->src));
       dbg(51,"Tid %lx ",tcaphash_end_key.tid);
       dbg(11,"Frame reqlink #%u ", pinfo->num);
 #endif
@@ -1153,6 +1156,10 @@ tcaphash_cont_matching(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
 #ifdef DEBUG_TCAPSRT
       dbg(12,"BnotFound ");
 #endif
+      if (use_dst) {
+        /* make another try with src tid / address */
+        goto try_src;
+      }
     } /* begin found */
   } /* cont found */
     /* display tcap session, if available */
diff --git a/epan/dissectors/asn1/tcap/tcap.cnf b/epan/dissectors/asn1/tcap/tcap.cnf
index 217048ab82..8898561d4a 100644
--- a/epan/dissectors/asn1/tcap/tcap.cnf
+++ b/epan/dissectors/asn1/tcap/tcap.cnf
@@ -156,6 +156,9 @@ ABRT-apdu/_untag/user-information abrt_user_information
     case 2:
       gp_tcapsrt_info->src_tid=tvb_get_ntohs(parameter_tvb, 0);
       break;
+    case 3:
+      gp_tcapsrt_info->src_tid=tvb_get_ntoh24(parameter_tvb, 0);
+      break;
     case 4:
       gp_tcapsrt_info->src_tid=tvb_get_ntohl(parameter_tvb, 0);
       break;
@@ -201,6 +204,9 @@ ABRT-apdu/_untag/user-information abrt_user_information
     case 2:
       gp_tcapsrt_info->dst_tid=tvb_get_ntohs(parameter_tvb, 0);
       break;
+    case 3:
+      gp_tcapsrt_info->dst_tid=tvb_get_ntoh24(parameter_tvb, 0);
+      break;
     case 4:
       gp_tcapsrt_info->dst_tid=tvb_get_ntohl(parameter_tvb, 0);
       break;