Proxy: fix heuristic dissector

Ensure that at least 12 bytes were captured before trying to check the magic.
Otherwise it can trigger an exception and prevent other heuristic dissectors
from being called.

Change-Id: Ib90febc208a69ae4e10c5c971e7cddfa7157c8a4
Reviewed-on: https://code.wireshark.org/review/29298
Petri-Dish: Pascal Quantin <pascal.quantin@gmail.com>
Tested-by: Petri Dish Buildbot
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>

diff --git a/epan/dissectors/packet-proxy.c b/epan/dissectors/packet-proxy.c
index 8e24a4aa354f37f7f89081b582f0da5e37604194..633e5df870c4e3f1968971c6b1791fd30fa08ec4 100644 (file)
--- a/epan/dissectors/packet-proxy.c
+++ b/epan/dissectors/packet-proxy.c
@@ -258,8 +258,9 @@ dissect_proxy_v2(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
 static gboolean
 dissect_proxy_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
 {
-    guint length = tvb_reported_length(tvb);
-    if (length >= 16 && tvb_memeql(tvb, 0, proxy_v2_magic, sizeof(proxy_v2_magic)) == 0) {
+    if (tvb_reported_length(tvb) >= 16 &&
+        tvb_captured_length(tvb) >= sizeof(proxy_v2_magic) &&
+        tvb_memeql(tvb, 0, proxy_v2_magic, sizeof(proxy_v2_magic)) == 0) {
         // TODO maybe check for "(hdr.v2.ver_cmd & 0xF0) == 0x20" as done in "9. Sample code" from
         // https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt?
         dissect_proxy_v2(tvb, pinfo, tree, data);