https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=7820
Summary: wlan_mgt.ht.capabilities bits 8-15 incorrectly decoded
(from wrong packet offset)
Product: Wireshark
Version: 1.8.3
Platform: x86
OS/Version: Windows 7
Status: NEW
Severity: Major
Priority: Low
Component: Dissection engine (libwireshark)
AssignedTo: bugzilla-admin@xxxxxxxxxxxxx
ReportedBy: mark.phillips@xxxxxxxxxx
Created attachment 9310
--> https://bugs.wireshark.org/bugzilla/attachment.cgi?id=9310
Look at the HT capabilities IE (not the VHT one)
Build Information:
Version 1.8.3 (SVN Rev 45256 from /trunk-1.8)
Copyright 1998-2012 Gerald Combs <gerald@xxxxxxxxxxxxx> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Compiled (64-bit) with GTK+ 2.24.10, with Cairo 1.10.2, with Pango 1.30.0, with
GLib 2.32.2, with WinPcap (4_1_2), with libz 1.2.5, without POSIX capabilities,
with SMI 0.4.8, with c-ares 1.7.1, with Lua 5.1, without Python, with GnuTLS
2.12.18, with Gcrypt 1.4.6, without Kerberos, with GeoIP, with PortAudio
V19-devel (built Oct 2 2012), with AirPcap.
Running on 64-bit Windows 7 Service Pack 1, build 7601, with WinPcap version
4.1.2 (packet.dll version 4.1.0.2001), based on libpcap version 1.0 branch
1_0_rel0b (20091008), GnuTLS 2.12.18, Gcrypt 1.4.6, without AirPcap.
Built using Microsoft Visual C++ 10.0 build 40219
Wireshark is Open Source Software released under the GNU General Public
License.
Check the man page and http://www.wireshark.org for more information.
--
The HT Capabilities IE starts as follows:-
0x21 Tag HT Capabilities
0x1a Tag length
0xad HT Capabilities Info B0-B7
0x09 HT Capabilities Info B8-B15
Note that the B8-B15 value is non-zero, but all the bits are decoded as 0!
I have appended an example of the decode.
The bug is that the code defines the bit fields as 16 bit, but increments the
offset in-between decoding B0-B7 and B8-B15 which causes the wrong bits to be
decoded.
Tag: HT Capabilities (802.11n D1.10)
Tag Number: HT Capabilities (802.11n D1.10) (45)
Tag length: 26
HT Capabilities Info: 0x09ad
.... .... .... ...1 = HT LDPC coding capability: Transmitter
supports receiving LDPC coded packets
.... .... .... ..0. = HT Support channel width: Transmitter
only supports 20MHz operation
.... .... .... 11.. = HT SM Power Save: SM Power Save disabled
(0x0003)
.... .... ...0 .... = HT Green Field: Transmitter is not able
to receive PPDUs with Green Field (GF) preamble
.... .... ..1. .... = HT Short GI for 20MHz: Supported
.... .... .0.. .... = HT Short GI for 40MHz: Not supported
.... .... 1... .... = HT Tx STBC: Supported
.... ..00 .... .... = HT Rx STBC: No Rx STBC support (0x0000)
.... .0.. .... .... = HT Delayed Block ACK: Transmitter does
not support HT-Delayed BlockAck
.... 0... .... .... = HT Max A-MSDU length: 3839 bytes
...0 .... .... .... = HT DSSS/CCK mode in 40MHz: Won't/Can't
use of DSSS/CCK in 40 MHz
..0. .... .... .... = HT PSMP Support: Won't/Can't support PSMP
operation
.0.. .... .... .... = HT Forty MHz Intolerant: Use of 40 MHz
transmissions unrestricted/allowed
0... .... .... .... = HT L-SIG TXOP Protection support: Not
supported
--
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