/* * Copyright (C) 2013-2022 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 #include #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); }