/*
* Copyright (C) 2013-2019 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
* Copyright (C) 2007-2013 Sourcefire, Inc.
*
* Authors: 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.
*/
/*
** upxdec.c
**
** 05/05/2k4 - 1st attempt
** 08/05/2k4 - Now works as a charm :D
** 09/05/2k4 - Moved code outta main(), got rid of globals for thread safety, added bound checking, minor cleaning
** 04/06/2k4 - Now we handle 2B, 2D and 2E :D
** 28/08/2k4 - PE rebuild for nested packers
** 12/12/2k4 - Improved PE rebuild code and added some debug info on failure
** 23/03/2k7 - New approach for rebuilding:
o Get imports via magic
o Get imports via leascan
o if (!pe) pe=scan4pe();
o if (!pe) forgepe();
*/
/*
** This code unpacks a dumped UPX1 section to a file.
** It was written reversing the loader found on some Win32 UPX compressed trojans; while porting
** it to C i've kinda followed the asm flow so it will probably be a bit hard to read.
** This code DOES NOT revert the uncompressed section to its original state as no E8/E9 fixup and
** of cause no IAT rebuild are performed.
**
** The Win32 asm unpacker is really a little programming jewel, pretty damn rare in these days of
** bloatness. My gratitude to whoever wrote it.
*/
#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include <stdlib.h>
#include <string.h>
#include "clamav.h"
#include "others.h"
#include "upx.h"
#include "str.h"
#include "lzma_iface.h"
#define PEALIGN(o, a) (((a)) ? (((o) / (a)) * (a)) : (o))
#define PESALIGN(o, a) (((a)) ? (((o) / (a) + ((o) % (a) != 0)) * (a)) : (o))
#define HEADERS "\
\x4D\x5A\x90\x00\x02\x00\x00\x00\x04\x00\x0F\x00\xFF\xFF\x00\x00\
\xB0\x00\x00\x00\x00\x00\x00\x00\x40\x00\x1A\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xD0\x00\x00\x00\
\x0E\x1F\xB4\x09\xBA\x0D\x00\xCD\x21\xB4\x4C\xCD\x21\x54\x68\x69\
\x73\x20\x66\x69\x6C\x65\x20\x77\x61\x73\x20\x63\x72\x65\x61\x74\
\x65\x64\x20\x62\x79\x20\x43\x6C\x61\x6D\x41\x56\x20\x66\x6F\x72\
\x20\x69\x6E\x74\x65\x72\x6E\x61\x6C\x20\x75\x73\x65\x20\x61\x6E\
\x64\x20\x73\x68\x6F\x75\x6C\x64\x20\x6E\x6F\x74\x20\x62\x65\x20\
\x72\x75\x6E\x2E\x0D\x0A\x43\x6C\x61\x6D\x41\x56\x20\x2D\x20\x41\
\x20\x47\x50\x4C\x20\x76\x69\x72\x75\x73\x20\x73\x63\x61\x6E\x6E\
\x65\x72\x20\x2D\x20\x68\x74\x74\x70\x3A\x2F\x2F\x77\x77\x77\x2E\
\x63\x6C\x61\x6D\x61\x76\x2E\x6E\x65\x74\x0D\x0A\x24\x00\x00\x00\
"
#define FAKEPE "\
\x50\x45\x00\x00\x4C\x01\x01\x00\x43\x4C\x41\x4D\x00\x00\x00\x00\
\x00\x00\x00\x00\xE0\x00\x83\x8F\x0B\x01\x00\x00\x00\x10\x00\x00\
\x00\x10\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x10\x00\x00\
\x00\x10\x00\x00\x00\x00\x40\x00\x00\x10\x00\x00\x00\x02\x00\x00\
\x01\x00\x00\x00\x00\x00\x00\x00\x03\x00\x0A\x00\x00\x00\x00\x00\
\xFF\xFF\xFF\xFF\x00\x02\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\
\x00\x00\x10\x00\x00\x10\x00\x00\x00\x00\x10\x00\x00\x10\x00\x00\
\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x2e\x63\x6c\x61\x6d\x30\x31\x00\
\xFF\xFF\xFF\xFF\x00\x10\x00\x00\xFF\xFF\xFF\xFF\x00\x02\x00\x00\
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff\xff\xff\
"
static char *checkpe(char *dst, uint32_t dsize, char *pehdr, uint32_t *valign, unsigned int *sectcnt)
{
char *sections;
if (!CLI_ISCONTAINED(dst, dsize, pehdr, 0xf8)) return NULL;
if (cli_readint32(pehdr) != 0x4550) return NULL;
if (!(*valign = cli_readint32(pehdr + 0x38))) return NULL;
sections = pehdr + 0xf8;
if (!(*sectcnt = (unsigned char)pehdr[6] + (unsigned char)pehdr[7] * 256)) return NULL;
if (!CLI_ISCONTAINED(dst, dsize, sections, *sectcnt * 0x28)) return NULL;
return sections;
}
/* PE from UPX */
static int pefromupx(const char *src, uint32_t ssize, char *dst, uint32_t *dsize, uint32_t ep, uint32_t upx0, uint32_t upx1, uint32_t *magic, uint32_t dend)
{
char *imports, *sections = NULL, *pehdr = NULL, *newbuf;
unsigned int sectcnt = 0, upd = 1;
uint32_t realstuffsz = 0, valign = 0;
uint32_t foffset = 0xd0 + 0xf8;
if ((dst == NULL) || (src == NULL))
return 0;
while ((valign = magic[sectcnt++])) {
if (CLI_ISCONTAINED(src, ssize - 5, src + ep - upx1 + valign - 2, 2) &&
src[ep - upx1 + valign - 2] == '\x8d' && /* lea edi, ... */
src[ep - upx1 + valign - 1] == '\xbe') /* ... [esi + offset] */
break;
}
if (!valign && CLI_ISCONTAINED(src, ssize - 8, src + ep - upx1 + 0x80, 8)) {
const char *pt = &src[ep - upx1 + 0x80];
cli_dbgmsg("UPX: bad magic - scanning for imports\n");
while ((pt = cli_memstr(pt, ssize - (pt - src) - 8, "\x8d\xbe", 2))) {
if (pt[6] == '\x8b' && pt[7] == '\x07') { /* lea edi, [esi+imports] / mov eax, [edi] */
valign = pt - src + 2 - ep + upx1;
break;
}
pt++;
}
}
if (valign && CLI_ISCONTAINED(src, ssize, src + ep - upx1 + valign, 4)) {
imports = dst + cli_readint32(src + ep - upx1 + valign);
realstuffsz = imports - dst;
if (realstuffsz >= *dsize) {
cli_dbgmsg("UPX: wrong realstuff size\n");
/* fallback and eventually craft */
} else {
pehdr = imports;
while (CLI_ISCONTAINED(dst, *dsize, pehdr, 8) && cli_readint32(pehdr)) {
pehdr += 8;
while (CLI_ISCONTAINED(dst, *dsize, pehdr, 2) && *pehdr) {
pehdr++;
while (CLI_ISCONTAINED(dst, *dsize, pehdr, 2) && *pehdr)
pehdr++;
pehdr++;
}
pehdr++;
}
pehdr += 4;
if (!(sections = checkpe(dst, *dsize, pehdr, &valign, §cnt))) pehdr = NULL;
}
}
if (!pehdr && dend > 0xf8 + 0x28) {
cli_dbgmsg("UPX: no luck - scanning for PE\n");
pehdr = &dst[dend - 0xf8 - 0x28];
while (pehdr > dst) {
if ((sections = checkpe(dst, *dsize, pehdr, &valign, §cnt)))
break;
pehdr--;
}
if (!(realstuffsz = pehdr - dst)) pehdr = NULL;
}
if (!pehdr) {
uint32_t rebsz = PESALIGN(dend, 0x1000);
cli_dbgmsg("UPX: no luck - brutally crafting a reasonable PE\n");
if (!(newbuf = (char *)cli_calloc(rebsz + 0x200, sizeof(char)))) {
cli_dbgmsg("UPX: malloc failed - giving up rebuild\n");
return 0;
}
memcpy(newbuf, HEADERS, 0xd0);
memcpy(newbuf + 0xd0, FAKEPE, 0x120);
memcpy(newbuf + 0x200, dst, dend);
memcpy(dst, newbuf, dend + 0x200);
free(newbuf);
cli_writeint32(dst + 0xd0 + 0x50, rebsz + 0x1000);
cli_writeint32(dst + 0xd0 + 0x100, rebsz);
cli_writeint32(dst + 0xd0 + 0x108, rebsz);
*dsize = rebsz + 0x200;
cli_dbgmsg("UPX: PE structure added to uncompressed data\n");
return 1;
}
if (!sections)
sectcnt = 0;
foffset = PESALIGN(foffset + 0x28 * sectcnt, valign);
for (upd = 0; upd < sectcnt; upd++) {
uint32_t vsize = PESALIGN((uint32_t)cli_readint32(sections + 8), valign);
uint32_t urva = PEALIGN((uint32_t)cli_readint32(sections + 12), valign);
/* Within bounds ? */
if (!CLI_ISCONTAINED(upx0, realstuffsz, urva, vsize)) {
cli_dbgmsg("UPX: Sect %d out of bounds - giving up rebuild\n", upd);
return 0;
}
cli_writeint32(sections + 8, vsize);
cli_writeint32(sections + 12, urva);
cli_writeint32(sections + 16, vsize);
cli_writeint32(sections + 20, foffset);
if (foffset + vsize < foffset) {
/* Integer overflow */
return 0;
}
foffset += vsize;
sections += 0x28;
}
cli_writeint32(pehdr + 8, 0x4d414c43);
cli_writeint32(pehdr + 0x3c, valign);
if (!(newbuf = (char *)cli_calloc(foffset, sizeof(char)))) {
cli_dbgmsg("UPX: malloc failed - giving up rebuild\n");
return 0;
}
memcpy(newbuf, HEADERS, 0xd0);
memcpy(newbuf + 0xd0, pehdr, 0xf8 + 0x28 * sectcnt);
sections = pehdr + 0xf8;
for (upd = 0; upd < sectcnt; upd++) {
uint32_t offset1, offset2, offset3;
offset1 = (uint32_t)cli_readint32(sections + 20);
offset2 = (uint32_t)cli_readint32(sections + 16);
if (offset1 > foffset || offset2 > foffset || offset1 + offset2 > foffset) {
free(newbuf);
return 1;
}
offset3 = (uint32_t)cli_readint32(sections + 12);
if (offset3 - upx0 > *dsize) {
free(newbuf);
return 1;
}
memcpy(newbuf + offset1, dst + offset3 - upx0, offset2);
sections += 0x28;
}
/* CBA restoring the imports they'll look different from the originals anyway... */
/* ...and yeap i miss the icon too :P */
if (foffset > *dsize + 8192) {
cli_dbgmsg("UPX: wrong raw size - giving up rebuild\n");
free(newbuf);
return 0;
}
memcpy(dst, newbuf, foffset);
*dsize = foffset;
free(newbuf);
cli_dbgmsg("UPX: PE structure rebuilt from compressed file\n");
return 1;
}
/* [doubleebx] */
static int doubleebx(const char *src, uint32_t *myebx, uint32_t *scur, uint32_t ssize)
{
uint32_t oldebx = *myebx;
*myebx *= 2;
if (!(oldebx & 0x7fffffff)) {
if (!CLI_ISCONTAINED(src, ssize, src + *scur, 4))
return -1;
oldebx = cli_readint32(src + *scur);
*myebx = oldebx * 2 + 1;
*scur += 4;
}
return (oldebx >> 31);
}
/* [inflate] */
int upx_inflate2b(const char *src, uint32_t ssize, char *dst, uint32_t *dsize, uint32_t upx0, uint32_t upx1, uint32_t ep)
{
int32_t backbytes, unp_offset = -1;
uint32_t backsize, myebx = 0, scur = 0, dcur = 0, i, magic[] = {0x108, 0x110, 0xd5, 0};
int oob;
while (1) {
while ((oob = doubleebx(src, &myebx, &scur, ssize)) == 1) {
if (scur >= ssize || dcur >= *dsize)
return -1;
dst[dcur++] = src[scur++];
}
if (oob == -1)
return -1;
backbytes = 1;
while (1) {
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (((int64_t)backbytes + oob) > INT32_MAX / 2)
return -1;
backbytes = backbytes * 2 + oob;
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (oob)
break;
}
backbytes -= 3;
if (backbytes >= 0) {
if (scur >= ssize)
return -1;
if (backbytes & 0xff000000)
return -1;
backbytes <<= 8;
backbytes += (unsigned char)(src[scur++]);
backbytes ^= 0xffffffff;
if (!backbytes)
break;
unp_offset = backbytes;
}
if ((backsize = (uint32_t)doubleebx(src, &myebx, &scur, ssize)) == 0xffffffff)
return -1;
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (backsize + oob > UINT32_MAX / 2)
return -1;
backsize = backsize * 2 + oob;
if (!backsize) {
backsize++;
do {
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (backsize + oob > UINT32_MAX / 2)
return -1;
backsize = backsize * 2 + oob;
} while ((oob = doubleebx(src, &myebx, &scur, ssize)) == 0);
if (oob == -1)
return -1;
if (backsize + 2 > UINT32_MAX)
return -1;
backsize += 2;
}
if ((uint32_t)unp_offset < 0xfffff300)
backsize++;
backsize++;
if (!CLI_ISCONTAINED(dst, *dsize, dst + dcur + unp_offset, backsize) || !CLI_ISCONTAINED(dst, *dsize, dst + dcur, backsize) || unp_offset >= 0)
return -1;
for (i = 0; i < backsize; i++)
dst[dcur + i] = dst[dcur + unp_offset + i];
dcur += backsize;
}
return pefromupx(src, ssize, dst, dsize, ep, upx0, upx1, magic, dcur);
}
int upx_inflate2d(const char *src, uint32_t ssize, char *dst, uint32_t *dsize, uint32_t upx0, uint32_t upx1, uint32_t ep)
{
int32_t backbytes, unp_offset = -1;
uint32_t backsize, myebx = 0, scur = 0, dcur = 0, i, magic[] = {0x11c, 0x124, 0};
int oob;
while (1) {
while ((oob = doubleebx(src, &myebx, &scur, ssize)) == 1) {
if (scur >= ssize || dcur >= *dsize)
return -1;
dst[dcur++] = src[scur++];
}
if (oob == -1)
return -1;
backbytes = 1;
while (1) {
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (((int64_t)backbytes + oob) > INT32_MAX / 2)
return -1;
backbytes = backbytes * 2 + oob;
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (oob)
break;
backbytes--;
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (((int64_t)backbytes + oob) > INT32_MAX / 2)
return -1;
backbytes = backbytes * 2 + oob;
}
backsize = 0;
backbytes -= 3;
if (backbytes >= 0) {
if (scur >= ssize)
return -1;
if (backbytes & 0xff000000)
return -1;
backbytes <<= 8;
backbytes += (unsigned char)(src[scur++]);
backbytes ^= 0xffffffff;
if (!backbytes)
break;
backsize = backbytes & 1;
CLI_SAR(backbytes, 1);
unp_offset = backbytes;
} else {
if ((backsize = (uint32_t)doubleebx(src, &myebx, &scur, ssize)) == 0xffffffff)
return -1;
}
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (backsize + oob > UINT32_MAX / 2)
return -1;
backsize = backsize * 2 + oob;
if (!backsize) {
backsize++;
do {
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (backsize + oob > UINT32_MAX / 2)
return -1;
backsize = backsize * 2 + oob;
} while ((oob = doubleebx(src, &myebx, &scur, ssize)) == 0);
if (oob == -1)
return -1;
if (backsize + 2 > UINT32_MAX)
return -1;
backsize += 2;
}
if ((uint32_t)unp_offset < 0xfffffb00)
backsize++;
backsize++;
if (!CLI_ISCONTAINED(dst, *dsize, dst + dcur + unp_offset, backsize) || !CLI_ISCONTAINED(dst, *dsize, dst + dcur, backsize) || unp_offset >= 0)
return -1;
for (i = 0; i < backsize; i++)
dst[dcur + i] = dst[dcur + unp_offset + i];
dcur += backsize;
}
return pefromupx(src, ssize, dst, dsize, ep, upx0, upx1, magic, dcur);
}
int upx_inflate2e(const char *src, uint32_t ssize, char *dst, uint32_t *dsize, uint32_t upx0, uint32_t upx1, uint32_t ep)
{
int32_t backbytes, unp_offset = -1;
uint32_t backsize, myebx = 0, scur = 0, dcur = 0, i, magic[] = {0x128, 0x130, 0};
int oob;
for (;;) {
while ((oob = doubleebx(src, &myebx, &scur, ssize))) {
if (oob == -1)
return -1;
if (scur >= ssize || dcur >= *dsize)
return -1;
dst[dcur++] = src[scur++];
}
backbytes = 1;
for (;;) {
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (((int64_t)backbytes + oob) > INT32_MAX / 2)
return -1;
backbytes = backbytes * 2 + oob;
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (oob)
break;
backbytes--;
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (((int64_t)backbytes + oob) > INT32_MAX / 2)
return -1;
backbytes = backbytes * 2 + oob;
}
backbytes -= 3;
if (backbytes >= 0) {
if (scur >= ssize)
return -1;
if (backbytes & 0xff000000)
return -1;
backbytes <<= 8;
backbytes += (unsigned char)(src[scur++]);
backbytes ^= 0xffffffff;
if (!backbytes)
break;
backsize = backbytes & 1; /* Using backsize to carry on the shifted out bit (UPX uses CF) */
CLI_SAR(backbytes, 1);
unp_offset = backbytes;
} else {
if ((backsize = (uint32_t)doubleebx(src, &myebx, &scur, ssize)) == 0xffffffff)
return -1;
} /* Using backsize to carry on the doubleebx result (UPX uses CF) */
if (backsize) { /* i.e. IF ( last sar shifted out 1 bit || last doubleebx()==1 ) */
if ((backsize = (uint32_t)doubleebx(src, &myebx, &scur, ssize)) == 0xffffffff)
return -1;
} else {
backsize = 1;
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (oob) {
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (backsize + oob > UINT32_MAX / 2)
return -1;
backsize = 2 + oob;
} else {
do {
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
return -1;
if (backsize + oob > UINT32_MAX / 2)
return -1;
backsize = backsize * 2 + oob;
} while ((oob = doubleebx(src, &myebx, &scur, ssize)) == 0);
if (oob == -1)
return -1;
if (backsize + 2 > UINT32_MAX)
return -1;
backsize += 2;
}
}
if ((uint32_t)unp_offset < 0xfffffb00)
backsize++;
if (backsize + 2 > UINT32_MAX)
return -1;
backsize += 2;
if (!CLI_ISCONTAINED(dst, *dsize, dst + dcur + unp_offset, backsize) || !CLI_ISCONTAINED(dst, *dsize, dst + dcur, backsize) || unp_offset >= 0)
return -1;
for (i = 0; i < backsize; i++)
dst[dcur + i] = dst[dcur + unp_offset + i];
dcur += backsize;
}
return pefromupx(src, ssize, dst, dsize, ep, upx0, upx1, magic, dcur);
}
int upx_inflatelzma(const char *src, uint32_t ssize, char *dst, uint32_t *dsize, uint32_t upx0, uint32_t upx1, uint32_t ep, uint32_t properties)
{
struct CLI_LZMA l;
uint32_t magic[] = {0xb16, 0xb1e, 0};
unsigned char fake_lzmahdr[5];
memset(&l, 0, sizeof(l));
cli_writeint32(fake_lzmahdr + 1, *dsize);
uint8_t lc = properties & 0xff;
uint8_t lp = (properties >> 8) & 0xff;
uint8_t pb = (properties >> 16) & 0xff;
if (lc >= 9 || lp >= 5 || pb >= 5)
return -1;
*fake_lzmahdr = lc + 9 * (5 * pb + lp);
l.next_in = fake_lzmahdr;
l.avail_in = 5;
if (cli_LzmaInit(&l, *dsize) != LZMA_RESULT_OK)
return 0;
l.avail_in = ssize;
l.avail_out = *dsize;
l.next_in = (unsigned char *)src + 2;
l.next_out = (unsigned char *)dst;
if (cli_LzmaDecode(&l) == LZMA_RESULT_DATA_ERROR) {
/* __asm__ __volatile__("int3"); */
cli_LzmaShutdown(&l);
return -1;
}
cli_LzmaShutdown(&l);
return pefromupx(src, ssize, dst, dsize, ep, upx0, upx1, magic, *dsize);
}