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packet: ensure pinfo->curr_layer_num does not depend on tree 

The TLS dissector relies on a stable value for pinfo->curr_layer_num
between passes to enable handshake reassembly and decryption. A mismatch
could occur if the subdissector accepted the data (len is non-zero), but
did not add any tree items (tree->tree_data->count remains unchanged).

The original change added the check for tree->tree_data->count in order
to remove protocol names that are not visible in the tree. This could
for example occur when the HTTP dissector accepts the data but requests
more data for reassembly.

This desire to hide protocols is understandable, so simply reverting the
change would not be ok. Checking pinfo->desegment_offset is also not
stable. So that leaves the current approach.

Change-Id: I247adafbaa6d23ab9397eadacabaed9e1bfde997
Ping-Bug: 15625
Fixes: v2.5.0rc0-1206-gcd90f732a1 ("Improve frame.protocols accuracy.")
Reviewed-on: https://code.wireshark.org/review/32919
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Pascal Quantin <pascal@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>
This commit is contained in:
Peter Wu 2019-04-21 03:16:12 +01:00 committed by Anders Broman
parent c802a83363
commit 5076e53ffb
1 changed files with 18 additions and 2 deletions
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20
epan/packet.c
View File

@ -798,7 +798,15 @@ call_dissector_work(dissector_handle_t handle, tvbuff_t *tvb, packet_info *pinfo
* tree. Remove it.
*/
while (wmem_list_count(pinfo->layers) > saved_layers_len) {
pinfo->curr_layer_num--;
if (len == 0) {
/*
* Only reduce the layer number if the dissector
* rejected the data. Since tree can be NULL on
* the first pass, we cannot check it or it will
* break dissectors that rely on a stable value.
*/
pinfo->curr_layer_num--;
}
wmem_list_remove_frame(pinfo->layers, wmem_list_tail(pinfo->layers));
}
}
@ -2756,7 +2764,15 @@ dissector_try_heuristic(heur_dissector_list_t sub_dissectors, tvbuff_t *tvb,
* items to the tree so remove it from the list.
*/
while (wmem_list_count(pinfo->layers) > saved_layers_len) {
pinfo->curr_layer_num--;
if (len == 0) {
/*
* Only reduce the layer number if the dissector
* rejected the data. Since tree can be NULL on
* the first pass, we cannot check it or it will
* break dissectors that rely on a stable value.
*/
pinfo->curr_layer_num--;
}
wmem_list_remove_frame(pinfo->layers, wmem_list_tail(pinfo->layers));
}
}