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483 lines
14 KiB
483 lines
14 KiB
/*
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* Copyright (C) 2004 aCaB <acab@clamav.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301, USA.
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*/
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/*
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** upxdec.c
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**
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** 05/05/2k4 - 1st attempt
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** 08/05/2k4 - Now works as a charm :D
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** 09/05/2k4 - Moved code outta main(), got rid of globals for thread safety, added bound checking, minor cleaning
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** 04/06/2k4 - Now we handle 2B, 2D and 2E :D
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** 28/08/2k4 - PE rebuild for nested packers
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** 12/12/2k4 - Improved PE rebuild code and added some debug info on failure
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*/
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/*
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** This code unpacks a dumped UPX1 section to a file.
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** It was written reversing the loader found on some Win32 UPX compressed trojans; while porting
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** it to C i've kinda followed the asm flow so it will probably be a bit hard to read.
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** This code DOES NOT revert the uncompressed section to its original state as no E8/E9 fixup and
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** of cause no IAT rebuild are performed.
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**
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** The Win32 asm unpacker is really a little programming jewel, pretty damn rare in these days of
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** bloatness. My gratitude to whoever wrote it.
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*/
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#if HAVE_CONFIG_H
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#include "clamav-config.h"
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#endif
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#include <stdlib.h>
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#include <string.h>
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#include "cltypes.h"
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#include "others.h"
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#define HEADERS "\
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\x4D\x5A\x90\x00\x02\x00\x00\x00\x04\x00\x0F\x00\xFF\xFF\x00\x00\
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\xB0\x00\x00\x00\x00\x00\x00\x00\x40\x00\x1A\x00\x00\x00\x00\x00\
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\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
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\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xD0\x00\x00\x00\
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\x0E\x1F\xB4\x09\xBA\x0D\x00\xCD\x21\xB4\x4C\xCD\x21\x54\x68\x69\
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\x73\x20\x66\x69\x6C\x65\x20\x77\x61\x73\x20\x63\x72\x65\x61\x74\
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\x65\x64\x20\x62\x79\x20\x43\x6C\x61\x6D\x41\x56\x20\x66\x6F\x72\
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\x20\x69\x6E\x74\x65\x72\x6E\x61\x6C\x20\x75\x73\x65\x20\x61\x6E\
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\x64\x20\x73\x68\x6F\x75\x6C\x64\x20\x6E\x6F\x74\x20\x62\x65\x20\
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\x72\x75\x6E\x2E\x0D\x0A\x43\x6C\x61\x6D\x41\x56\x20\x2D\x20\x41\
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\x20\x47\x50\x4C\x20\x76\x69\x72\x75\x73\x20\x73\x63\x61\x6E\x6E\
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\x65\x72\x20\x2D\x20\x68\x74\x74\x70\x3A\x2F\x2F\x77\x77\x77\x2E\
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\x63\x6C\x61\x6D\x61\x76\x2E\x6E\x65\x74\x0D\x0A\x24\x00\x00\x00\
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"
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/* PE from UPX */
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int pefromupx (char *src, char *dst, uint32_t *dsize, uint32_t ep, uint32_t upx0, uint32_t upx1, uint32_t magic)
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{
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char *imports, *sections, *pehdr, *newbuf;
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int sectcnt, upd=1;
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uint32_t realstuffsz;
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uint32_t foffset=0xd0+0xf8;
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if((dst == NULL) || (src == NULL))
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return 0;
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imports = dst + cli_readint32(src + ep - upx1 + magic);
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realstuffsz = imports-dst;
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if (realstuffsz >= *dsize ) {
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cli_dbgmsg("UPX: wrong realstuff size - giving up rebuild\n");
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return 0;
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}
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pehdr = imports;
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while (CLI_ISCONTAINED(dst, *dsize, pehdr, 8) && cli_readint32(pehdr)) {
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pehdr+=8;
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while(CLI_ISCONTAINED(dst, *dsize, pehdr, 2) && *pehdr) {
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pehdr++;
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while (CLI_ISCONTAINED(dst, *dsize, pehdr, 2) && *pehdr)
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pehdr++;
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pehdr++;
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}
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pehdr++;
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}
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pehdr+=4;
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if (!CLI_ISCONTAINED(dst, *dsize, pehdr, 0xf8)) {
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cli_dbgmsg("UPX: sections out of bounds - giving up rebuild\n");
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return 0;
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}
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if ( cli_readint32(pehdr) != 0x4550 ) {
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cli_dbgmsg("UPX: No magic for PE - giving up rebuild\n");
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return 0;
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}
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if (! cli_readint32(pehdr+0x38)) {
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cli_dbgmsg("UPX: Cant align to a NULL bound - giving up rebuild\n");
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return 0;
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}
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sections = pehdr+0xf8;
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if ( ! (sectcnt = (unsigned char)pehdr[6]+256*(unsigned char)pehdr[7])) {
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cli_dbgmsg("UPX: No sections? - giving up rebuild\n");
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return 0;
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}
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foffset+=0x28*sectcnt;
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if (!CLI_ISCONTAINED(dst, *dsize, sections, 0x28*sectcnt)) {
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cli_dbgmsg("UPX: Not enough space for all sects - giving up rebuild\n");
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return 0;
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}
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for (upd = 0; upd <sectcnt ; upd++) {
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uint32_t vsize=cli_readint32(sections+8)-1;
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uint32_t rsize=cli_readint32(sections+16);
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uint32_t urva=cli_readint32(sections+12);
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vsize=(((vsize/0x1000)+1)*0x1000); /* FIXME: get bounds from header */
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/* Within bounds ? */
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if (!CLI_ISCONTAINED(upx0, realstuffsz, urva, vsize)) {
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cli_dbgmsg("UPX: Sect %d out of bounds - giving up rebuild\n", upd);
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return 0;
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}
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/* Rsize -gt Vsize ? */
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if ( rsize > vsize ) {
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cli_dbgmsg("UPX: Raw size for sect %d is greater than virtual (%x / %x) - giving up rebuild\n", upd, rsize, vsize);
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return 0;
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}
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/* Am i been fooled? There are better ways ;) */
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if ( rsize+4 < vsize && cli_readint32(dst+urva-upx0+rsize) ) {
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cli_dbgmsg("UPX: Am i been fooled? - giving up rebuild\n", upd);
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return 0;
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}
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cli_writeint32(sections+8, vsize);
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cli_writeint32(sections+20, foffset);
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foffset+=rsize;
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sections+=0x28;
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}
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cli_writeint32(pehdr+8, 0x4d414c43);
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if (!(newbuf = (char *) cli_malloc(foffset))) {
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cli_dbgmsg("UPX: malloc failed - giving up rebuild\n", upd);
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return 0;
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}
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memcpy(newbuf, HEADERS, 0xd0);
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memcpy(newbuf+0xd0, pehdr,0xf8+0x28*sectcnt);
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sections = pehdr+0xf8;
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for (upd = 0; upd <sectcnt ; upd++) {
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memcpy(newbuf+cli_readint32(sections+20), dst+cli_readint32(sections+12)-upx0, cli_readint32(sections+16));
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sections+=0x28;
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}
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/* CBA restoring the imports they'll look different from the originals anyway... */
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/* ...and yeap i miss the icon too :P */
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if (foffset > *dsize) {
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cli_dbgmsg("UPX: wrong raw size - giving up rebuild\n");
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return 0;
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}
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memcpy(dst, newbuf, foffset);
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*dsize = foffset;
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free(newbuf);
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cli_dbgmsg("UPX: PE structure rebuilt from compressed file\n");
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return 1;
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}
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/* [doubleebx] */
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static int doubleebx(char *src, int32_t *myebx, int *scur, int ssize)
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{
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int32_t oldebx = *myebx;
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*myebx*=2;
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if ( !(oldebx & 0x7fffffff)) {
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if (! CLI_ISCONTAINED(src, ssize, src+*scur, 4))
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return -1;
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oldebx = cli_readint32(src+*scur);
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*myebx = oldebx*2+1;
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*scur+=4;
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}
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return (oldebx>>31)&1;
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}
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/* [inflate] */
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int upx_inflate2b(char *src, uint32_t ssize, char *dst, uint32_t *dsize, uint32_t upx0, uint32_t upx1, uint32_t ep)
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{
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int32_t backbytes, unp_offset = -1, myebx = 0;
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int scur=0, dcur=0, i, backsize, oob;
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while (1) {
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while ((oob = doubleebx(src, &myebx, &scur, ssize)) == 1) {
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if (scur<0 || scur>=ssize || dcur<0 || dcur>=*dsize)
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return -1;
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dst[dcur++] = src[scur++];
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}
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if ( oob == -1 )
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return -1;
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backbytes = 1;
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while (1) {
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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backbytes = backbytes*2+oob;
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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if (oob)
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break;
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}
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backsize = 0;
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backbytes-=3;
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if ( backbytes >= 0 ) {
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if (scur<0 || scur>=ssize)
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return -1;
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backbytes<<=8;
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backbytes+=(unsigned char)(src[scur++]);
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backbytes^=0xffffffff;
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if (!backbytes)
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break;
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unp_offset = backbytes;
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}
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
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return -1;
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backsize = oob;
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
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return -1;
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backsize = backsize*2 + oob;
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if (!backsize) {
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backsize++;
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do {
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
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return -1;
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backsize = backsize*2 + oob;
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} while ((oob = doubleebx(src, &myebx, &scur, ssize)) == 0);
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if ( oob == -1 )
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return -1;
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backsize+=2;
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}
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if ( (uint32_t)unp_offset < 0xfffff300 )
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backsize++;
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backsize++;
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for (i = 0; i < backsize; i++) {
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if (dcur+i<0 || dcur+i>=*dsize || dcur+unp_offset+i<0 || dcur+unp_offset+i>=*dsize)
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return -1;
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dst[dcur + i] = dst[dcur + unp_offset + i];
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}
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dcur+=backsize;
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}
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if ( ep - upx1 + 0x108 <= ssize-5 && /* Wondering how we got so far?! */
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src[ep - upx1 + 0x106] == '\x8d' && /* lea edi, ... */
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src[ep - upx1 + 0x107] == '\xbe' ) /* ... [esi + offset] */
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return pefromupx (src, dst, dsize, ep, upx0, upx1, 0x108);
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cli_dbgmsg("UPX: bad magic for 2b\n");
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return 0;
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}
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int upx_inflate2d(char *src, uint32_t ssize, char *dst, uint32_t *dsize, uint32_t upx0, uint32_t upx1, uint32_t ep)
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{
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int32_t backbytes, unp_offset = -1, myebx = 0;
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int scur=0, dcur=0, i, backsize, oob;
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while (1) {
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while ( (oob = doubleebx(src, &myebx, &scur, ssize)) == 1) {
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if (scur<0 || scur>=ssize || dcur<0 || dcur>=*dsize)
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return -1;
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dst[dcur++] = src[scur++];
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}
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if ( oob == -1 )
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return -1;
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backbytes = 1;
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while (1) {
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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backbytes = backbytes*2+oob;
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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if (oob)
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break;
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backbytes--;
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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backbytes=backbytes*2+oob;
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}
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backsize = 0;
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backbytes-=3;
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if ( backbytes >= 0 ) {
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if (scur<0 || scur>=ssize)
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return -1;
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backbytes<<=8;
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backbytes+=(unsigned char)(src[scur++]);
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backbytes^=0xffffffff;
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if (!backbytes)
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break;
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backsize = backbytes & 1;
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backbytes>>=1;
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unp_offset = backbytes;
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}
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else {
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if ( (backsize = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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}
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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backsize = backsize*2 + oob;
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if (!backsize) {
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backsize++;
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do {
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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backsize = backsize*2 + oob;
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} while ( (oob = doubleebx(src, &myebx, &scur, ssize)) == 0);
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if ( oob == -1 )
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return -1;
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backsize+=2;
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}
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if ( (uint32_t)unp_offset < 0xfffffb00 )
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backsize++;
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backsize++;
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for (i = 0; i < backsize; i++) {
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if (dcur+i<0 || dcur+i>=*dsize || dcur+unp_offset+i<0 || dcur+unp_offset+i>=*dsize)
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return -1;
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dst[dcur + i] = dst[dcur + unp_offset + i];
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}
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dcur+=backsize;
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}
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if ( ep - upx1 + 0x124 <= ssize-5 ) { /* Wondering how we got so far?! */
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if ( src[ep - upx1 + 0x11a] == '\x8d' && src[ep - upx1 + 0x11b] == '\xbe' )
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return pefromupx (src, dst, dsize, ep, upx0, upx1, 0x11c);
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if ( src[ep - upx1 + 0x122] == '\x8d' && src[ep - upx1 + 0x123] == '\xbe' )
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return pefromupx (src, dst, dsize, ep, upx0, upx1, 0x124);
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}
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cli_dbgmsg("UPX: bad magic for 2d\n");
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return 0;
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}
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int upx_inflate2e(char *src, uint32_t ssize, char *dst, uint32_t *dsize, uint32_t upx0, uint32_t upx1, uint32_t ep)
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{
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int32_t backbytes, unp_offset = -1, myebx = 0;
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int scur=0, dcur=0, i, backsize, oob;
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for(;;) {
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while ( (oob = doubleebx(src, &myebx, &scur, ssize)) ) {
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if (oob == -1)
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return -1;
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if (scur<0 || scur>=ssize || dcur<0 || dcur>=*dsize)
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return -1;
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dst[dcur++] = src[scur++];
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}
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backbytes = 1;
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for(;;) {
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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backbytes = backbytes*2+oob;
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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if ( oob )
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break;
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backbytes--;
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if ( (oob = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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backbytes=backbytes*2+oob;
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}
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backsize = 0;
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backbytes-=3;
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if ( backbytes >= 0 ) {
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if (scur<0 || scur>=ssize)
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return -1;
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backbytes<<=8;
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backbytes+=(unsigned char)(src[scur++]);
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backbytes^=0xffffffff;
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if (!backbytes)
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break;
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backsize = backbytes & 1; /* Using backsize to carry on the shifted out bit (UPX uses CF) */
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backbytes>>=1;
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unp_offset = backbytes;
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}
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else {
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if ( (backsize = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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} /* Using backsize to carry on the doubleebx result (UPX uses CF) */
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if (backsize) { /* i.e. IF ( last sar shifted out 1 bit || last doubleebx()==1 ) */
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if ( (backsize = doubleebx(src, &myebx, &scur, ssize)) == -1 )
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return -1;
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}
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else {
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backsize = 1;
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if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
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return -1;
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if (oob) {
|
|
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
|
|
return -1;
|
|
backsize = 2 + oob;
|
|
}
|
|
else {
|
|
do {
|
|
if ((oob = doubleebx(src, &myebx, &scur, ssize)) == -1)
|
|
return -1;
|
|
backsize = backsize * 2 + oob;
|
|
} while ((oob = doubleebx(src, &myebx, &scur, ssize)) == 0);
|
|
if (oob == -1)
|
|
return -1;
|
|
backsize+=2;
|
|
}
|
|
}
|
|
|
|
if ( (uint32_t)unp_offset < 0xfffffb00 )
|
|
backsize++;
|
|
|
|
backsize+=2;
|
|
for (i = 0; i < backsize; i++) {
|
|
if (dcur+i<0 || dcur+i>=*dsize || dcur+unp_offset+i<0 || dcur+unp_offset+i>=*dsize)
|
|
return -1;
|
|
dst[dcur + i] = dst[dcur + unp_offset + i];
|
|
}
|
|
dcur+=backsize;
|
|
}
|
|
|
|
if ( ep - upx1 + 0x130 <= ssize-5 ) { /* Wondering how we got so far?! */
|
|
if ( src[ep - upx1 + 0x126] == '\x8d' && src[ep - upx1 + 0x127] == '\xbe' )
|
|
return pefromupx (src, dst, dsize, ep, upx0, upx1, 0x128);
|
|
if ( src[ep - upx1 + 0x12e] == '\x8d' && src[ep - upx1 + 0x12f] == '\xbe' )
|
|
return pefromupx (src, dst, dsize, ep, upx0, upx1, 0x130);
|
|
}
|
|
cli_dbgmsg("UPX: bad magic for 2e\n");
|
|
return 0;
|
|
}
|
|
|