forked from osmocom/wireshark
a985d71ec1
the payload we hand to the next dissector. Check whether the length field in an 802.3 header doesn't go past the (presumed) end of the payload. svn path=/trunk/; revision=25731
134 lines
4.7 KiB
C
134 lines
4.7 KiB
C
/* packet-ieee8023.c
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* Routine for dissecting 802.3 (as opposed to D/I/X Ethernet) packets.
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*
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* $Id$
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*
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* Wireshark - Network traffic analyzer
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* By Gerald Combs <gerald@wireshark.org>
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* Copyright 1998 Gerald Combs
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#ifdef HAVE_CONFIG_H
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# include "config.h"
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#endif
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#include <glib.h>
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#include <epan/packet.h>
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#include <epan/expert.h>
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#include "packet-ieee8023.h"
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#include "packet-eth.h"
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#include "packet-frame.h"
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static dissector_handle_t ipx_handle;
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static dissector_handle_t llc_handle;
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void
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dissect_802_3(volatile int length, gboolean is_802_2, tvbuff_t *tvb,
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int offset_after_length, packet_info *pinfo, proto_tree *tree,
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proto_tree *fh_tree, int length_id, int trailer_id,
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int fcs_len)
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{
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proto_item *length_it;
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tvbuff_t *volatile next_tvb = NULL;
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tvbuff_t *volatile trailer_tvb = NULL;
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const char *saved_proto;
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gint captured_length, reported_length;
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length_it = proto_tree_add_uint(fh_tree, length_id, tvb,
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offset_after_length - 2, 2, length);
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/* Get the length of the payload.
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If the FCS length is positive, remove the FCS.
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(If it's zero, there's no FCS; if it's negative, we don't know whether
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there's an FCS, so we'll guess based on the length of the trailer.) */
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reported_length = tvb_reported_length_remaining(tvb, offset_after_length);
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if (fcs_len > 0) {
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if (reported_length >= fcs_len)
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reported_length -= fcs_len;
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}
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/* Make sure the length in the 802.3 header doesn't go past the end of
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the payload. */
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if (length > reported_length) {
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length = reported_length;
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expert_add_info_format(pinfo, length_it, PI_MALFORMED, PI_ERROR,
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"Length field value goes past the end of the payload");
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}
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/* Give the next dissector only 'length' number of bytes. */
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captured_length = tvb_length_remaining(tvb, offset_after_length);
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if (captured_length > length)
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captured_length = length;
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next_tvb = tvb_new_subset(tvb, offset_after_length, captured_length, length);
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TRY {
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trailer_tvb = tvb_new_subset(tvb, offset_after_length + length, -1, -1);
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}
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CATCH2(BoundsError, ReportedBoundsError) {
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/* The packet has exactly "length" bytes worth of captured data
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left in it, so the "tvb_new_subset()" creating "trailer_tvb"
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threw an exception.
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This means that all the data in the frame is within the length
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value (assuming our offset isn't past the end of the tvb), so
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we give all the data to the next protocol and have no trailer. */
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trailer_tvb = NULL;
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}
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ENDTRY;
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/* Dissect the payload either as IPX or as an LLC frame.
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Catch BoundsError and ReportedBoundsError, so that if the
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reported length of "next_tvb" was reduced by some dissector
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before an exception was thrown, we can still put in an item
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for the trailer. */
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saved_proto = pinfo->current_proto;
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TRY {
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if (is_802_2)
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call_dissector(llc_handle, next_tvb, pinfo, tree);
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else
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call_dissector(ipx_handle, next_tvb, pinfo, tree);
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}
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CATCH(BoundsError) {
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/* Somebody threw BoundsError, which means that dissecting the payload
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found that the packet was cut off by a snapshot length before the
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end of the payload. The trailer comes after the payload, so *all*
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of the trailer is cut off - don't bother adding the trailer, just
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rethrow the exception so it gets reported. */
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RETHROW;
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}
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CATCH_ALL {
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/* Well, somebody threw an exception other than BoundsError.
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Show the exception, and then drive on to show the trailer,
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restoring the protocol value that was in effect before we
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called the subdissector. */
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show_exception(next_tvb, pinfo, tree, EXCEPT_CODE, GET_MESSAGE);
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pinfo->current_proto = saved_proto;
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}
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ENDTRY;
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add_ethernet_trailer(pinfo, fh_tree, trailer_id, tvb, trailer_tvb, fcs_len);
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}
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void
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proto_reg_handoff_ieee802_3(void)
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{
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/*
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* Get handles for the IPX and LLC dissectors.
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*/
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ipx_handle = find_dissector("ipx");
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llc_handle = find_dissector("llc");
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}
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