forked from osmocom/wireshark
95 lines
2.5 KiB
C
95 lines
2.5 KiB
C
/* packet-wap.c
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*
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* Utility routines for WAP dissectors
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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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* WAP dissector based on original work by Ben Fowler
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* Updated by Neil Hunter <neil.hunter@energis-squared.com>
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* WTLS support by Alexandre P. Ferreira (Splice IP)
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*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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#include "config.h"
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#ifdef DEBUG
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#include <stdio.h>
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#endif
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#include <epan/packet.h>
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#include "packet-wap.h"
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/*
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* Accessor to retrieve variable length int as used in WAP protocol.
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* The value is encoded in the lower 7 bits. If the top bit is set, then the
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* value continues into the next byte.
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* The octetCount parameter holds the number of bytes read in order to return
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* the final value. Can be pre-initialised to start at offset+count.
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*
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* XXX This seems to be used exclusively for fetching size values. We should
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* probably rename this to wap_get_checked_size or something along those lines.
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*/
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#define MAX_WAP_GUINTVAR (100 * 1000 * 1000) // Arbitrary. We need a large number that won't overflow a guint.
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guint
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tvb_get_guintvar (tvbuff_t *tvb, guint offset,
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guint *octetCount, packet_info *pinfo, expert_field *ei)
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{
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guint value = 0, previous_value;
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guint octet;
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guint counter = 0;
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#ifdef DEBUG
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fprintf (stderr,
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"dissect_wap: Starting tvb_get_guintvar at offset %d\n", offset);
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#endif
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do {
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octet = tvb_get_guint8 (tvb, offset+counter);
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counter++;
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previous_value = value;
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value <<= 7; /* Value only exists in 7 of the 8 bits */
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value += (octet & 0x7F);
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if (value < previous_value || value > MAX_WAP_GUINTVAR) {
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/* overflow; clamp the value at UINT_MAX */
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proto_tree_add_expert(NULL, pinfo, ei, tvb, offset, counter);
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value = MAX_WAP_GUINTVAR;
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break;
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}
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#ifdef DEBUG
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fprintf(stderr,
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"dissect_wap: computing: octet is %d (0x%02x), count=%d, value=%d\n",
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octet, octet, counter, value);
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#endif
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} while (octet & 0x80);
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#ifdef DEBUG
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fprintf (stderr,
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"dissect_wap: Leaving tvb_get_guintvar count=%d, value=%u\n",
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counter, value);
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#endif
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if (octetCount)
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*octetCount = counter;
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return value;
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}
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/*
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* Editor modelines - https://www.wireshark.org/tools/modelines.html
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*
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* Local variables:
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* c-basic-offset: 4
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* tab-width: 8
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* indent-tabs-mode: nil
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* End:
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*
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* vi: set shiftwidth=4 tabstop=8 expandtab:
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* :indentSize=4:tabSize=8:noTabs=true:
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*/
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