168 lines
3.7 KiB
C
168 lines
3.7 KiB
C
/*
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* Decompression code for LZNT1. This encoding is used by
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* Microsoft in various file formats and protocols including SMB3.
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*
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* See MS-XCA.
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*
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* Copyright (C) 2019 Aurélien Aptel
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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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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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#include <glib.h>
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#include <epan/exceptions.h>
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#include <epan/tvbuff.h>
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#include <epan/wmem_scopes.h>
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#define MAX_INPUT_SIZE (16*1024*1024) /* 16MB */
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static gboolean
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uncompress_chunk(tvbuff_t *tvb, int offset, int in_size, wmem_array_t *obuf)
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{
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int in_off = 0, out_off = 0, out_start = 0;
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guint8 flags;
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guint i, j, val, pos;
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out_start = wmem_array_get_count(obuf);
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while (in_off < in_size) {
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flags = tvb_get_guint8(tvb, offset+in_off);
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in_off++;
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for (i = 0; i < 8; i++) {
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if (0 == ((flags>>i)&1)) {
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val = tvb_get_guint8(tvb, offset+in_off);
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in_off++;
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wmem_array_append_one(obuf, val);
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out_off++;
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} else {
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guint f, l_mask = 0x0FFF, o_shift = 12;
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guint match_len, match_off;
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f = tvb_get_letohs(tvb, offset+in_off);
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in_off += 2;
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pos = out_off-1;
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while (pos >= 0x10) {
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l_mask >>= 1;
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o_shift -= 1;
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pos >>= 1;
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}
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match_len = (f & l_mask) + 3;
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match_off = (f >> o_shift) + 1;
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for (j = 0; j < match_len; j++) {
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guint8 byte;
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if (match_off > (guint)out_off)
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return FALSE;
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if (wmem_array_try_index(obuf, out_start+out_off-match_off, &byte))
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return FALSE;
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wmem_array_append_one(obuf, byte);
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out_off++;
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}
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}
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if (in_off == in_size) {
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goto out;
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}
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}
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}
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out:
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return TRUE;
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}
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static gboolean
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do_uncompress(tvbuff_t *tvb, int offset, int in_size, wmem_array_t *obuf)
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{
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int in_off = 0;
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guint32 header, length, i;
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gboolean ok;
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if (!tvb)
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return FALSE;
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if (!in_size || in_size > MAX_INPUT_SIZE)
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return FALSE;
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while (in_off < in_size) {
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header = tvb_get_letohs(tvb, offset+in_off);
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in_off += 2;
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length = (header & 0x0FFF) + 1;
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if (!(header & 0x8000)) {
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for (i = 0; i < length; i++) {
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guint8 v = tvb_get_guint8(tvb, offset+in_off);
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wmem_array_append_one(obuf, v);
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in_off++;
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}
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} else {
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ok = uncompress_chunk(tvb, offset + in_off, length, obuf);
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if (!ok)
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return FALSE;
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in_off += length;
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}
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}
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return TRUE;
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}
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tvbuff_t *
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tvb_uncompress_lznt1(tvbuff_t *tvb, const int offset, int in_size)
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{
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volatile gboolean ok = FALSE;
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wmem_allocator_t *pool;
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wmem_array_t *obuf;
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tvbuff_t *out;
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pool = wmem_allocator_new(WMEM_ALLOCATOR_SIMPLE);
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obuf = wmem_array_sized_new(pool, 1, in_size*2);
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TRY {
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ok = do_uncompress(tvb, offset, in_size, obuf);
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} CATCH_ALL {
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ok = FALSE;
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}
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ENDTRY;
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if (ok) {
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/*
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* Cannot pass a tvb free callback that frees the wmem
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* pool, so we make an extra copy that uses bare
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* pointers. This could be optimized if tvb API had a
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* free pool callback of some sort.
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*/
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guint size = wmem_array_get_count(obuf);
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guint8 *p = (guint8 *)g_malloc(size);
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memcpy(p, wmem_array_get_raw(obuf), size);
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out = tvb_new_real_data(p, size, size);
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tvb_set_free_cb(out, g_free);
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} else {
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out = NULL;
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}
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wmem_destroy_allocator(pool);
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return out;
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}
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tvbuff_t *
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tvb_child_uncompress_lznt1(tvbuff_t *parent, tvbuff_t *tvb, const int offset, int in_size)
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{
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tvbuff_t *new_tvb = tvb_uncompress_lznt1(tvb, offset, in_size);
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if (new_tvb)
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tvb_set_child_real_data_tvbuff(parent, new_tvb);
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return new_tvb;
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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: 8
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* tab-width: 8
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* indent-tabs-mode: t
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* End:
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*
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* vi: set shiftwidth=8 tabstop=8 noexpandtab:
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* :indentSize=8:tabSize=8:noTabs=false:
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*/
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