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/*
* Decompression code for LZNT1. This encoding is used by
* Microsoft in various file formats and protocols including SMB3.
*
* See MS-XCA.
*
* Copyright (C) 2019 Aurélien Aptel
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include <glib.h>
#include <epan/exceptions.h>
#include <epan/tvbuff.h>
#include <epan/wmem_scopes.h>
#define MAX_INPUT_SIZE (16*1024*1024) /* 16MB */
static bool
uncompress_chunk(tvbuff_t *tvb, int offset, int in_size, wmem_array_t *obuf)
{
int in_off = 0, out_off = 0, out_start = 0;
uint8_t flags;
unsigned i, j, val, pos;
out_start = wmem_array_get_count(obuf);
while (in_off < in_size) {
flags = tvb_get_uint8(tvb, offset+in_off);
in_off++;
for (i = 0; i < 8; i++) {
if (0 == ((flags>>i)&1)) {
val = tvb_get_uint8(tvb, offset+in_off);
in_off++;
wmem_array_append_one(obuf, val);
out_off++;
} else {
unsigned f, l_mask = 0x0FFF, o_shift = 12;
unsigned match_len, match_off;
f = tvb_get_letohs(tvb, offset+in_off);
in_off += 2;
pos = out_off-1;
while (pos >= 0x10) {
l_mask >>= 1;
o_shift -= 1;
pos >>= 1;
}
match_len = (f & l_mask) + 3;
match_off = (f >> o_shift) + 1;
for (j = 0; j < match_len; j++) {
uint8_t byte;
if (match_off > (unsigned)out_off)
return false;
if (wmem_array_try_index(obuf, out_start+out_off-match_off, &byte))
return false;
wmem_array_append_one(obuf, byte);
out_off++;
}
}
if (in_off == in_size) {
goto out;
}
}
}
out:
return true;
}
static bool
do_uncompress(tvbuff_t *tvb, int offset, int in_size, wmem_array_t *obuf)
{
int in_off = 0;
uint32_t header, length, i;
bool ok;
if (!tvb)
return false;
if (!in_size || in_size > MAX_INPUT_SIZE)
return false;
while (in_off < in_size) {
header = tvb_get_letohs(tvb, offset+in_off);
in_off += 2;
length = (header & 0x0FFF) + 1;
if (!(header & 0x8000)) {
for (i = 0; i < length; i++) {
uint8_t v = tvb_get_uint8(tvb, offset+in_off);
wmem_array_append_one(obuf, v);
in_off++;
}
} else {
ok = uncompress_chunk(tvb, offset + in_off, length, obuf);
if (!ok)
return false;
in_off += length;
}
}
return true;
}
tvbuff_t *
tvb_uncompress_lznt1(tvbuff_t *tvb, const int offset, int in_size)
{
volatile bool ok = false;
wmem_allocator_t *pool;
wmem_array_t *obuf;
tvbuff_t *out;
pool = wmem_allocator_new(WMEM_ALLOCATOR_SIMPLE);
obuf = wmem_array_sized_new(pool, 1, in_size*2);
TRY {
ok = do_uncompress(tvb, offset, in_size, obuf);
} CATCH_ALL {
ok = false;
}
ENDTRY;
if (ok) {
/*
* Cannot pass a tvb free callback that frees the wmem
* pool, so we make an extra copy that uses bare
* pointers. This could be optimized if tvb API had a
* free pool callback of some sort.
*/
unsigned size = wmem_array_get_count(obuf);
uint8_t *p = (uint8_t *)g_malloc(size);
memcpy(p, wmem_array_get_raw(obuf), size);
out = tvb_new_real_data(p, size, size);
tvb_set_free_cb(out, g_free);
} else {
out = NULL;
}
wmem_destroy_allocator(pool);
return out;
}
tvbuff_t *
tvb_child_uncompress_lznt1(tvbuff_t *parent, tvbuff_t *tvb, const int offset, int in_size)
{
tvbuff_t *new_tvb = tvb_uncompress_lznt1(tvb, offset, in_size);
if (new_tvb)
tvb_set_child_real_data_tvbuff(parent, new_tvb);
return new_tvb;
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 8
* tab-width: 8
* indent-tabs-mode: t
* End:
*
* vi: set shiftwidth=8 tabstop=8 noexpandtab:
* :indentSize=8:tabSize=8:noTabs=false:
*/
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