iso14443: use the correct I-block payload

When we reassemble I-blocks, we pass the payload to fragment_add_seq_next.
To do so, we use the overall iso14443 tvb, an offset and the payload length
as parameters.

We then call process_reassembled_data to do reassembly. If the I-block was
not fragmented, process_reassembled_data returns the only fragment + the
rest of the packet after this fragment.

This might be a misunderstanding on my part or something to be fixed in the
reassembly routines. For now, we work around this by defining a new tvb for
the data we submit to fragment_add_seq_next.

(I ran into a similar issue years ago for DVB-CI. Add a comment about this.
If it turns out that there's a better way to fix this, we should be fixing
both dissectors.)

Change-Id: Id83ab152529a5150669df3099df6f60be7a3a723
Reviewed-on: https://code.wireshark.org/review/33355
Petri-Dish: Martin Kaiser <wireshark@kaiser.cx>
Tested-by: Petri Dish Buildbot
Petri-Dish: Anders Broman <a.broman58@gmail.com>
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>

1 files changed, 8 insertions, 5 deletions

diff --git a/epan/dissectors/packet-iso14443.c b/epan/dissectors/packet-iso14443.c
index fc0154c210..56e402cef9 100644
--- a/epan/dissectors/packet-iso14443.c
+++ b/epan/dissectors/packet-iso14443.c
@@ -1071,9 +1071,6 @@ dissect_iso14443_cmd_type_block(tvbuff_t *tvb, packet_info *pinfo,
     }
 
     if (inf_len > 0) {
-        fragment_head *frag_msg;
-        tvbuff_t *payload_tvb;
-
         inf_ti = proto_tree_add_item(tree, hf_iso14443_inf,
                 tvb, offset, inf_len, ENC_NA);
         if (block_type == S_BLOCK_TYPE) {
@@ -1089,10 +1086,16 @@ dissect_iso14443_cmd_type_block(tvbuff_t *tvb, packet_info *pinfo,
         }
 
         if (block_type == I_BLOCK_TYPE) {
+            fragment_head *frag_msg;
+            tvbuff_t *inf_tvb, *payload_tvb;
+
+            /* see the comment in dissect_dvbci_tpdu (packet-dvbci.c) */
+            inf_tvb = tvb_new_subset_length(tvb, offset, inf_len);
             frag_msg = fragment_add_seq_next(&i_block_reassembly_table,
-                    tvb, offset, pinfo, 0, NULL, inf_len, (pcb & 0x10) ? 1 : 0);
+                    inf_tvb, 0, pinfo, 0, NULL, inf_len,
+                    (pcb & 0x10) ? 1 : 0);
 
-            payload_tvb = process_reassembled_data(tvb, offset, pinfo,
+            payload_tvb = process_reassembled_data(inf_tvb, 0, pinfo,
                     "Reassembled APDU", frag_msg,
                     &i_block_frag_items, NULL, tree);