/*
* Copyright (C) 2013-2019 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
* Copyright (C) 2007-2013 Sourcefire, Inc.
*
* Authors: Luciano Giuseppe 'Pnluck', Alberto Wu
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*/
#include <string.h>
#include "clamav.h"
#include "execs.h"
#include "others.h"
#include "rebuildpe.h"
#include "aspack.h"
#define ASPACK_BLOCKS_OFFSET_212 0x57c
#define ASPACK_BLOCKS_OFFSET_OTHER 0x5d8
#define ASPACK_BLOCKS_OFFSET_242 0x5e4
#define ASPACK_STR_INIT_MLT_OFFSET_212 0x70e
#define ASPACK_STR_INIT_MLT_OFFSET_OTHER 0x76a
#define ASPACK_STR_INIT_MLT_OFFSET_242 0x776
#define ASPACK_COMP_BLOCK_OFFSET_212 0x6d6
#define ASPACK_COMP_BLOCK_OFFSET_OTHER 0x732
#define ASPACK_COMP_BLOCK_OFFSET_242 0x73e
#define ASPACK_WRKBUF_OFFSET_212 0x148
#define ASPACK_WRKBUF_OFFSET_OTHER 0x13a
#define ASPACK_WRKBUF_OFFSET_242 0x148
#define ASPACK_OEP_OFFSET_212 0x39b
#define ASPACK_OEP_OFFSET_OTHER 0x401
#define ASPACK_OEP_OFFSET_242 0x40d
struct DICT_HELPER {
uint32_t *starts;
uint8_t *ends;
uint32_t size;
};
struct ASPK {
uint32_t bitpos;
uint32_t hash;
uint32_t init_array[58];
struct DICT_HELPER dict_helper[4];
uint8_t *input;
uint8_t *iend;
uint8_t *decrypt_dict;
uint32_t decarray3[4][24];
uint32_t decarray4[4][24];
int dict_ok;
uint8_t array2[758];
uint8_t array1[19];
};
static inline int readstream(struct ASPK *stream)
{
while (stream->bitpos >= 8) {
if (stream->input >= stream->iend) return 0;
stream->hash = (stream->hash << 8) | *stream->input;
stream->input++;
stream->bitpos -= 8;
}
return 1;
}
static uint32_t getdec(struct ASPK *stream, uint8_t which, int *err)
{
uint32_t ret;
uint8_t pos;
uint32_t *d3 = stream->decarray3[which];
uint32_t *d4 = stream->decarray4[which];
*err = 1;
if (!readstream(stream)) return 0;
ret = (stream->hash >> (8 - stream->bitpos)) & 0xfffe00;
if (ret < d3[8]) {
if ((ret >> 16) >= 0x100) return 0;
if (!(pos = stream->dict_helper[which].ends[ret >> 16]) || pos >= 24) return 0; /* 0<pos<24 */
} else {
if (ret < d3[10]) {
if (ret < d3[9])
pos = 9;
else
pos = 10;
} else {
if (ret < d3[11])
pos = 11;
else {
if (ret < d3[12])
pos = 12;
else {
if (ret < d3[13])
pos = 13;
else {
if (ret < d3[14])
pos = 14;
else
pos = 15;
}
}
}
}
}
stream->bitpos += pos;
ret = ((ret - d3[pos - 1]) >> (24 - pos)) + d4[pos];
if (ret >= stream->dict_helper[which].size) return 0;
ret = stream->dict_helper[which].starts[ret];
*err = 0;
return ret;
}
static uint8_t build_decrypt_array(struct ASPK *stream, uint8_t *array, uint8_t which)
{
uint32_t sum = 0, counter = 23, i, endoff = 0, bus[18], dict[18];
uint32_t *d3 = stream->decarray3[which];
uint32_t *d4 = stream->decarray4[which];
memset(bus, 0, sizeof(bus));
memset(dict, 0, sizeof(dict));
for (i = 0; i < stream->dict_helper[which].size; i++) {
/* within bounds - see comments in build_decrypt_dictionaries */
if (array[i] > 17) return 0;
bus[array[i]]++;
}
d3[0] = 0;
d4[0] = 0;
i = 0;
while (counter >= 9) { /* 0<=i<=14 */
sum += (bus[i + 1] << counter);
if (sum > 0x1000000) return 0;
d3[i + 1] = sum;
d4[i + 1] = dict[i + 1] = bus[i] + d4[i];
if (counter >= 0x10) {
uint32_t old = endoff;
endoff = d3[i + 1] >> 0x10;
if (endoff - old) {
if (!CLI_ISCONTAINED(stream->dict_helper[which].ends, 0x100, stream->dict_helper[which].ends + old, endoff - old)) return 0;
memset((stream->dict_helper[which].ends + old), i + 1, endoff - old);
}
}
i++;
counter--;
}
if (sum != 0x1000000) return 0;
i = 0;
for (i = 0; i < stream->dict_helper[which].size; i++) {
if (array[i]) { /* within bounds - see above */
if (array[i] > 17) return 0;
if (dict[array[i]] >= stream->dict_helper[which].size) return 0;
stream->dict_helper[which].starts[dict[array[i]]] = i;
dict[array[i]]++;
}
}
return 1;
}
static uint8_t getbits(struct ASPK *stream, uint32_t num, int *err)
{
uint8_t retvalue;
if (!readstream(stream)) {
*err = 1;
return 0;
}
*err = 0;
retvalue = ((stream->hash >> (8 - stream->bitpos)) & 0xffffff) >> (24 - num);
stream->bitpos += num;
return retvalue;
}
static int build_decrypt_dictionaries(struct ASPK *stream)
{
unsigned int counter;
uint32_t ret;
int oob;
if (!getbits(stream, 1, &oob)) memset(stream->decrypt_dict, 0, 0x2f5);
if (oob) return 0;
for (counter = 0; counter < 19; counter++) {
stream->array1[counter] = getbits(stream, 4, &oob);
if (oob) return 0;
}
if (!build_decrypt_array(stream, stream->array1, 3)) return 0; /* array1[19] - [3].size=19 */
counter = 0;
while (counter < 757) {
ret = getdec(stream, 3, &oob);
if (oob) return 0;
if (ret >= 16) {
if (ret != 16) {
if (ret == 17)
ret = 3 + getbits(stream, 3, &oob);
else
ret = 11 + getbits(stream, 7, &oob);
if (oob) return 0;
while (ret) {
if (counter >= 757) break;
stream->array2[1 + counter] = 0;
counter++;
ret--;
}
} else {
ret = 3 + getbits(stream, 2, &oob);
if (oob) return 0;
while (ret) {
if (counter >= 757) break;
stream->array2[1 + counter] = stream->array2[counter];
counter++;
ret--;
}
}
} else {
stream->array2[1 + counter] = (stream->decrypt_dict[counter] + ret) & 0xF;
counter++;
}
}
if (!build_decrypt_array(stream, &stream->array2[1], 0) /* array2[758-1=757] - [0].size=721 */ || !build_decrypt_array(stream, &stream->array2[722], 1) /* array2[758-722=36] - [1].size=28 */ || !build_decrypt_array(stream, &stream->array2[750], 2) /* array2[758-750=8] - [2].size=8 */) return 0;
stream->dict_ok = 0;
for (counter = 0; counter < 8; counter++) {
if (stream->array2[750 + counter] != 3) {
stream->dict_ok = 1;
break;
}
}
memcpy(stream->decrypt_dict, &stream->array2[1], 757);
return 1;
}
static int decrypt(struct ASPK *stream, uint8_t *stuff, uint32_t size, uint8_t *output)
{
/* ep+6d6 -> ep+748 = 0x72*/
uint32_t gen, backsize, backbytes, useold, counter = 0;
uint32_t hist[4] = {0, 0, 0, 0};
int oob;
cli_dbgmsg("Aspack: decrypt size:%x\n", size);
while (counter < size) {
gen = getdec(stream, 0, &oob);
if (oob) return 0;
if (gen < 256) { /* implied within bounds */
output[counter] = (uint8_t)gen;
counter++;
continue;
}
if (gen >= 720) {
if (!build_decrypt_dictionaries(stream)) return 0;
continue;
}
if ((backbytes = (gen - 256) >> 3) >= 58) return 0; /* checks init_array + stuff */
backsize = ((gen - 256) & 7) + 2;
if ((backsize - 2) == 7) {
uint8_t hlp;
gen = getdec(stream, 1, &oob);
if (oob || gen >= 0x56) return 0;
hlp = stuff[gen + 0x1c];
if (!readstream(stream)) return 0;
backsize += stuff[gen] + (((stream->hash >> (8 - stream->bitpos)) & 0xffffff) >> (0x18 - hlp));
stream->bitpos += hlp;
}
useold = stream->init_array[backbytes];
gen = stuff[backbytes + 0x38];
if (!stream->dict_ok || gen < 3) {
if (!readstream(stream)) return 0;
useold += ((stream->hash >> (8 - stream->bitpos)) & 0xffffff) >> (24 - gen);
stream->bitpos += gen;
} else {
gen -= 3;
if (!readstream(stream)) return 0;
useold += ((((stream->hash >> (8 - stream->bitpos)) & 0xffffff) >> (24 - gen)) * 8);
stream->bitpos += gen;
useold += getdec(stream, 2, &oob);
if (oob) return 0;
}
if (useold < 3) {
backbytes = hist[useold];
if (useold != 0) {
hist[useold] = hist[0];
hist[0] = backbytes;
}
} else {
hist[2] = hist[1];
hist[1] = hist[0];
hist[0] = backbytes = useold - 3;
}
backbytes++;
if (!backbytes || backbytes > counter || backsize > size - counter) return 0;
while (backsize--) {
output[counter] = output[counter - backbytes];
counter++;
}
}
return 1;
}
static int decomp_block(struct ASPK *stream, uint32_t size, uint8_t *stuff, uint8_t *output)
{
memset(stream->decarray3, 0, sizeof(stream->decarray3));
memset(stream->decarray4, 0, sizeof(stream->decarray4));
memset(stream->decrypt_dict, 0, 757);
stream->bitpos = 0x20;
if (!build_decrypt_dictionaries(stream)) return 0;
return decrypt(stream, stuff, size, output);
}
#define INIT_DICT_HELPER(n, sz) \
stream.dict_helper[n].starts = (uint32_t *)wrkbuf; \
stream.dict_helper[n].ends = &wrkbuf[sz * sizeof(uint32_t)]; \
stream.dict_helper[n].size = sz; \
wrkbuf = &wrkbuf[sz * sizeof(uint32_t) + 0x100];
int unaspack(uint8_t *image, unsigned int size, struct cli_exe_section *sections, uint16_t sectcount, uint32_t ep, uint32_t base, int f, aspack_version_t version)
{
struct ASPK stream;
uint32_t i = 0, j = 0;
uint8_t *blocks = NULL, *wrkbuf;
uint32_t block_rva = 1, block_size;
struct cli_exe_section *outsects;
uint32_t blocks_offset, stream_init_multiplier_offset, comp_block_offset, wrkbuf_offset, oep_offset;
switch (version) {
case ASPACK_VER_212:
cli_dbgmsg("Aspack: Attempting to unpack Aspack 2.12.\n");
blocks_offset = ASPACK_BLOCKS_OFFSET_212;
stream_init_multiplier_offset = ASPACK_STR_INIT_MLT_OFFSET_212;
comp_block_offset = ASPACK_COMP_BLOCK_OFFSET_212;
wrkbuf_offset = ASPACK_WRKBUF_OFFSET_212;
oep_offset = ASPACK_OEP_OFFSET_212;
break;
case ASPACK_VER_OTHER:
cli_dbgmsg("Aspack: Attempting to unpack Aspack >2.12, <2.42.\n");
blocks_offset = ASPACK_BLOCKS_OFFSET_OTHER;
stream_init_multiplier_offset = ASPACK_STR_INIT_MLT_OFFSET_OTHER;
comp_block_offset = ASPACK_COMP_BLOCK_OFFSET_OTHER;
wrkbuf_offset = ASPACK_WRKBUF_OFFSET_OTHER;
oep_offset = ASPACK_OEP_OFFSET_OTHER;
break;
case ASPACK_VER_242:
cli_dbgmsg("Aspack: Attempting to unpack Aspack 2.42.\n");
blocks_offset = ASPACK_BLOCKS_OFFSET_242;
stream_init_multiplier_offset = ASPACK_STR_INIT_MLT_OFFSET_242;
comp_block_offset = ASPACK_COMP_BLOCK_OFFSET_242;
wrkbuf_offset = ASPACK_WRKBUF_OFFSET_242;
oep_offset = ASPACK_OEP_OFFSET_242;
break;
default:
cli_dbgmsg("Aspack: Unexpected/Unknown version number.\n");
return 0;
}
blocks = image + ep + blocks_offset;
if (!(wrkbuf = cli_calloc(0x1800, sizeof(uint8_t)))) {
cli_dbgmsg("Aspack: Unable to allocate dictionary\n");
return 0;
}
INIT_DICT_HELPER(0, 721); /* dictionary -> dictionary + b44 */
INIT_DICT_HELPER(1, 28); /* dictionary + c44 -> dictionary + cb4 */
INIT_DICT_HELPER(2, 8); /* dictionary + db4 -> dictionary + dd4 */
INIT_DICT_HELPER(3, 19); /* dictionary + ed4 -> dictionary + f20 */
stream.decrypt_dict = wrkbuf;
stream.hash = 0x10000;
for (i = 0; i < 58; i++) {
stream.init_array[i] = j;
if (ep + i + stream_init_multiplier_offset < size) {
j += (1 << image[ep + i + stream_init_multiplier_offset]);
}
}
memset(stream.array1, 0, sizeof(stream.array1));
memset(stream.array2, 0, sizeof(stream.array2));
i = 0;
while (CLI_ISCONTAINED(image, size, blocks, 8) && (block_rva = cli_readint32(blocks)) && (block_size = cli_readint32(blocks + 4)) && CLI_ISCONTAINED(image, size, image + block_rva, block_size)) {
cli_dbgmsg("Aspack: unpacking block rva:%x - sz:%x\n", block_rva, block_size);
wrkbuf = (uint8_t *)cli_calloc(block_size + 0x10e, sizeof(uint8_t));
if (!wrkbuf) {
cli_dbgmsg("Aspack: Null work buff\n");
break;
}
stream.input = wrkbuf;
stream.iend = &wrkbuf[block_size + 0x10e];
memcpy(wrkbuf, image + block_rva, block_size);
if (!decomp_block(&stream, block_size, &image[ep + comp_block_offset], image + block_rva)) {
cli_dbgmsg("Aspack: decomp_block failed\n");
free(wrkbuf);
break;
} else
cli_dbgmsg("Aspack: decomp block succeed\n");
free(wrkbuf);
if (i == 0 && block_size > 7) { /* first sect j/c unrolling */
while (i < block_size - 6) {
uint8_t curbyte = image[block_rva + i];
if (curbyte == 0xe8 || curbyte == 0xe9) {
wrkbuf = &image[block_rva + i + 1];
if (*wrkbuf == image[ep + wrkbuf_offset]) {
uint32_t target = cli_readint32(wrkbuf) & 0xffffff00;
CLI_ROL(target, 0x18);
cli_writeint32(wrkbuf, target - i);
i += 4;
}
}
i++;
}
}
if (version == ASPACK_VER_212) {
blocks += 8;
} else {
blocks += 12;
block_size = cli_readint32(blocks + 4);
while (!((block_size + 0x10e) & 0xffffffff)) {
blocks += 12;
block_size = cli_readint32(blocks + 4);
}
}
}
cli_dbgmsg("Aspack: leaving loop all uncompressed\n");
free(stream.dict_helper[0].starts);
if (block_rva) {
cli_dbgmsg("Aspack: unpacking failure\n");
return 0;
}
if (sectcount > 2 && ep == sections[sectcount - 2].rva && !sections[sectcount - 1].rsz) {
sectcount -= 2;
}
if (!(outsects = cli_malloc(sizeof(struct cli_exe_section) * sectcount))) {
cli_dbgmsg("Aspack: OOM - rebuild failed\n");
cli_writen(f, image, size);
return 1; /* No whatsoheader - won't infloop in pe.c */
}
memcpy(outsects, sections, sizeof(struct cli_exe_section) * sectcount);
for (i = 0; i < sectcount; i++) {
outsects[i].raw = outsects[i].rva;
outsects[i].rsz = outsects[i].vsz;
}
if (!cli_rebuildpe((char *)image, outsects, sectcount, base, cli_readint32(image + ep + oep_offset), 0, 0, f)) {
cli_dbgmsg("Aspack: rebuild failed\n");
cli_writen(f, image, size);
} else {
cli_dbgmsg("Aspack: successfully rebuilt\n");
}
free(outsects);
return 1;
}