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packet: ensure consistent layer number for heuristics dissector 

DTLS decryption works for single-pass dissection, but breaks in the
second pass. Turns out that "curr_layer_num" has decremented in the
second pass, resulting in a failure to lookup the decrypted data.
This decryption issue was triggered by v2.3.0rc0-3740-ge1f84f985e
("Fix Decode As for protocols that may use tunneling.").

The first time the UDP dissector invokes "dissector_try_heuristic", the
second time "call_heur_dissector_direct". The first one increments
"curr_layer_num", so do the same in the second case.

Change-Id: I62679b817b02f42d073cfc07b88ec36d5bec5f04
Bug: 14243
Fixes: v1.11.4-rc1-468-g2cfda31ff0 ("Change the signature of dissector_try_heuristic() to return hdtbl_entry")
Reviewed-on: https://code.wireshark.org/review/24565
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Reviewed-by: Anders Broman <a.broman58@gmail.com>
This commit is contained in:
Peter Wu 2017-11-24 00:05:05 +00:00 committed by Anders Broman
parent b99677dea9
commit 9ac02f18c9
1 changed files with 16 additions and 1 deletions
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17
epan/packet.c
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@ -3102,6 +3102,7 @@ void call_heur_dissector_direct(heur_dtbl_entry_t *heur_dtbl_entry, tvbuff_t *tv
const char *saved_curr_proto;
const char *saved_heur_list_name;
guint16 saved_can_desegment;
guint saved_layers_len = 0;
g_assert(heur_dtbl_entry);
@ -3121,6 +3122,8 @@ void call_heur_dissector_direct(heur_dtbl_entry_t *heur_dtbl_entry, tvbuff_t *tv
saved_curr_proto = pinfo->current_proto;
saved_heur_list_name = pinfo->heur_list_name;
saved_layers_len = wmem_list_count(pinfo->layers);
if (!heur_dtbl_entry->enabled ||
(heur_dtbl_entry->protocol != NULL && !proto_is_protocol_enabled(heur_dtbl_entry->protocol))) {
g_assert(data_handle->protocol != NULL);
@ -3132,15 +3135,27 @@ void call_heur_dissector_direct(heur_dtbl_entry_t *heur_dtbl_entry, tvbuff_t *tv
/* do NOT change this behavior - wslua uses the protocol short name set here in order
to determine which Lua-based heuristic dissector to call */
pinfo->current_proto = proto_get_protocol_short_name(heur_dtbl_entry->protocol);
pinfo->curr_layer_num++;
wmem_list_append(pinfo->layers, GINT_TO_POINTER(proto_get_id(heur_dtbl_entry->protocol)));
}
pinfo->heur_list_name = heur_dtbl_entry->list_name;
/* call the dissector, in case of failure call data handle (might happen with exported PDUs) */
if(!(*heur_dtbl_entry->dissector)(tvb, pinfo, tree, data))
if(!(*heur_dtbl_entry->dissector)(tvb, pinfo, tree, data)) {
call_dissector_work(data_handle, tvb, pinfo, tree, TRUE, NULL);
/*
* We added a protocol layer above. The dissector
* didn't accept the packet or it didn't add any
* items to the tree so remove it from the list.
*/
while (wmem_list_count(pinfo->layers) > saved_layers_len) {
pinfo->curr_layer_num--;
wmem_list_remove_frame(pinfo->layers, wmem_list_tail(pinfo->layers));
}
}
/* Restore info from caller */
pinfo->can_desegment = saved_can_desegment;
pinfo->current_proto = saved_curr_proto;