From 0f27a83c5692b2afebe6e6934c1051f76aa2ecf9 Mon Sep 17 00:00:00 2001
From: Jason Cohen <kryojenik2@gmail.com>
Date: Wed, 31 Aug 2022 11:10:17 -0500
Subject: [PATCH] f5ethtrailer: Improve "old-style" heuristic
Remove a chance for an infinate loop in the disection heuristic.
---
epan/dissectors/packet-f5ethtrailer.c | 108 +++++++++++++-------------
1 file changed, 56 insertions(+), 52 deletions(-)
diff --git a/epan/dissectors/packet-f5ethtrailer.c b/epan/dissectors/packet-f5ethtrailer.c
index b2ba8f899d..915348ea83 100644
--- a/epan/dissectors/packet-f5ethtrailer.c
+++ b/epan/dissectors/packet-f5ethtrailer.c
@@ -2751,69 +2751,73 @@ dissect_dpt_trailer(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *d
static gint
dissect_old_trailer(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
{
- proto_tree *type_tree = NULL;
- proto_item *ti = NULL;
guint offset = 0;
- guint processed = 0;
- f5eth_tap_data_t *tdata = (f5eth_tap_data_t *)data;
- guint8 type;
- guint8 len;
- guint8 ver;
/* While we still have data in the trailer. For old format trailers, this needs
* type, length, version (3 bytes) and for new format trailers, the magic header (4 bytes).
* All old format trailers are at least 4 bytes long, so just check for length of magic.
*/
- while (tvb_reported_length_remaining(tvb, offset)) {
- type = tvb_get_guint8(tvb, offset);
- len = tvb_get_guint8(tvb, offset + F5_OFF_LENGTH) + F5_OFF_VERSION;
- ver = tvb_get_guint8(tvb, offset + F5_OFF_VERSION);
-
- if (len <= tvb_reported_length_remaining(tvb, offset) && type >= F5TYPE_LOW
- && type <= F5TYPE_HIGH && len >= F5_MIN_SANE && len <= F5_MAX_SANE
- && ver <= F5TRAILER_VER_MAX) {
- /* Parse out the specified trailer. */
- switch (type) {
- case F5TYPE_LOW:
- ti = proto_tree_add_item(tree, hf_low_id, tvb, offset, len, ENC_NA);
- type_tree = proto_item_add_subtree(ti, ett_f5ethtrailer_low);
-
- processed = dissect_low_trailer(tvb, pinfo, type_tree, offset, len, ver, tdata);
- if (processed > 0) {
- tdata->trailer_len += processed;
- tdata->noise_low = 1;
- }
- break;
- case F5TYPE_MED:
- ti = proto_tree_add_item(tree, hf_med_id, tvb, offset, len, ENC_NA);
- type_tree = proto_item_add_subtree(ti, ett_f5ethtrailer_med);
-
- processed = dissect_med_trailer(tvb, pinfo, type_tree, offset, len, ver, tdata);
- if (processed > 0) {
- tdata->trailer_len += processed;
- tdata->noise_med = 1;
- }
- break;
- case F5TYPE_HIGH:
- ti = proto_tree_add_item(tree, hf_high_id, tvb, offset, len, ENC_NA);
- type_tree = proto_item_add_subtree(ti, ett_f5ethtrailer_high);
-
- processed =
- dissect_high_trailer(tvb, pinfo, type_tree, offset, len, ver, tdata);
- if (processed > 0) {
- tdata->trailer_len += processed;
- tdata->noise_high = 1;
- }
- break;
+ while (tvb_reported_length_remaining(tvb, offset) >= F5_MIN_SANE) {
+ /* length field does not include the type and length bytes. Add them back in */
+ guint8 len = tvb_get_guint8(tvb, offset + F5_OFF_LENGTH) + F5_OFF_VERSION;
+ if (len > tvb_reported_length_remaining(tvb, offset)
+ || len < F5_MIN_SANE || len > F5_MAX_SANE) {
+ /* Invalid length - either a malformed trailer, corrupt packet, or not f5ethtrailer */
+ return offset;
+ }
+ guint8 type = tvb_get_guint8(tvb, offset);
+ guint8 ver = tvb_get_guint8(tvb, offset + F5_OFF_VERSION);
+
+ /* Parse out the specified trailer. */
+ proto_tree *type_tree = NULL;
+ proto_item *ti = NULL;
+ f5eth_tap_data_t *tdata = (f5eth_tap_data_t *)data;
+ guint processed = 0;
+
+ switch (type) {
+ case F5TYPE_LOW:
+ ti = proto_tree_add_item(tree, hf_low_id, tvb, offset, len, ENC_NA);
+ type_tree = proto_item_add_subtree(ti, ett_f5ethtrailer_low);
+
+ processed = dissect_low_trailer(tvb, pinfo, type_tree, offset, len, ver, tdata);
+ if (processed > 0) {
+ tdata->trailer_len += processed;
+ tdata->noise_low = 1;
}
- if (processed == 0) {
- proto_item_set_len(ti, 1);
- return offset;
+ break;
+ case F5TYPE_MED:
+ ti = proto_tree_add_item(tree, hf_med_id, tvb, offset, len, ENC_NA);
+ type_tree = proto_item_add_subtree(ti, ett_f5ethtrailer_med);
+
+ processed = dissect_med_trailer(tvb, pinfo, type_tree, offset, len, ver, tdata);
+ if (processed > 0) {
+ tdata->trailer_len += processed;
+ tdata->noise_med = 1;
+ }
+ break;
+ case F5TYPE_HIGH:
+ ti = proto_tree_add_item(tree, hf_high_id, tvb, offset, len, ENC_NA);
+ type_tree = proto_item_add_subtree(ti, ett_f5ethtrailer_high);
+
+ processed =
+ dissect_high_trailer(tvb, pinfo, type_tree, offset, len, ver, tdata);
+ if (processed > 0) {
+ tdata->trailer_len += processed;
+ tdata->noise_high = 1;
}
+ break;
+ default:
+ /* Unknown type - malformed trailer, corrupt packet, or not f5ethtrailer - bali out*/
+ return offset;
+ }
+ if (processed == 0) {
+ /* couldn't process trailer - bali out */
+ proto_item_set_len(ti, 1);
+ return offset;
}
offset += processed;
}
-return offset;
+ return offset;
} /* dissect_old_trailer() */
/*---------------------------------------------------------------------------*/
--
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