/*
* 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.
*/
/*
** petitep.c
**
** 09/07/2k4 - Dumped and reversed
** 10/07/2k4 - Very 1st approach
** 10/07/2k4 - PE stuff and main loop
** 11/07/2k4 - Porting finished, tracking my bugs...
** 12/07/2k4 - ARRRRRGHHH :D
** 14/07/2k4 - Code cleaned
** 15/07/2k4 - Securing && ClamAV porting
** 21/07/2k4 - Unmangled imports now supported
** 22/07/2k4 - Unstripped .relocs now supported
**
*/
/*
** Unpacks a buffer containing a petite 2.2 compressed
** file. Doesn't perform Import Table unmangling. Doesn't
** fixup call/jumps. Tries to "guess" the original sections
** structure and entrypoint.
**
** Lotta phanx to Micky for patiently bearing my screams :P
** Greets to Ian Luck: the SEH MOVSB thingy almost got me :O
** TODO: Cope with level 0 and older petite versions.
*/
#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include <stdlib.h>
#include <string.h>
#include "clamav.h"
#include "rebuildpe.h"
#include "execs.h"
#include "others.h"
#include "petite.h"
static int doubledl(char **scur, uint8_t *mydlptr, char *buffer, uint32_t buffersize)
{
unsigned char mydl = *mydlptr;
unsigned char olddl = mydl;
mydl *= 2;
if (!(olddl & 0x7f)) {
if (*scur < buffer || *scur >= buffer + buffersize - 1)
return -1;
olddl = **scur;
mydl = olddl * 2 + 1;
*scur = *scur + 1;
}
*mydlptr = mydl;
return (olddl >> 7) & 1;
}
int petite_inflate2x_1to9(char *buf, uint32_t minrva, uint32_t bufsz, struct cli_exe_section *sections, unsigned int sectcount, uint32_t Imagebase, uint32_t pep, int desc, int version, uint32_t ResRva, uint32_t ResSize)
{
char *adjbuf = buf - minrva;
char *packed = NULL;
uint32_t thisrva = 0, bottom = 0, enc_ep = 0, irva = 0, workdone = 0, grown = 0x355, skew = 0x35;
int j = 0, oob, mangled = 0, check4resources = 0;
struct cli_exe_section *usects = NULL;
void *tmpsct = NULL;
/*
-] The real thing [-
*/
/* NOTE: (435063->4350a5) Petite kernel32!imports and error strings */
/* Here we adjust the start of packed blob, the size of petite code,
* the difference in size if relocs were stripped
* See below...
*/
if (version == 2)
packed = adjbuf + sections[sectcount - 1].rva + 0x1b8;
if (version == 1) {
packed = adjbuf + sections[sectcount - 1].rva + 0x178;
grown = 0x323; /* My name is Harry potter */
skew = 0x34;
}
while (1) {
char *ssrc, *ddst;
uint32_t size, srva;
int backbytes, oldback, addsize;
unsigned int backsize;
if (!CLI_ISCONTAINED(buf, bufsz, packed, 4)) {
if (usects)
free(usects);
return 1;
}
srva = cli_readint32(packed);
if (!srva) {
/* WERE DONE !!! :D */
int t, upd = 1;
if (j <= 0) /* Some non petite compressed files will get here */
return 1;
/* Select * from sections order by rva asc; */
while (upd) {
upd = 0;
for (t = 0; t < j - 1; t++) {
uint32_t trva, trsz, tvsz;
if (usects[t].rva <= usects[t + 1].rva)
continue;
trva = usects[t].rva;
trsz = usects[t].rsz;
tvsz = usects[t].vsz;
usects[t].rva = usects[t + 1].rva;
usects[t].rsz = usects[t + 1].rsz;
usects[t].vsz = usects[t + 1].vsz;
usects[t + 1].rva = trva;
usects[t + 1].rsz = trsz;
usects[t + 1].vsz = tvsz;
upd = 1;
}
}
/* Computes virtualsize... we try to guess, actually :O */
for (t = 0; t < j - 1; t++) {
if (usects[t].vsz != usects[t + 1].rva - usects[t].rva)
usects[t].vsz = usects[t + 1].rva - usects[t].rva;
}
/*
* Our encryption is pathetic and out software is lame but
* we need to claim it's unbreakable.
* So why dont we just mangle the imports and encrypt the EP?!
*/
/* Decrypts old entrypoint if we got enough clues */
if (enc_ep) {
uint32_t virtaddr = pep + 5 + Imagebase, tmpep;
int rndm = 0, dummy = 1;
char *thunk = adjbuf + irva;
char *imports;
if (version == 2) { /* 2.2 onley */
while (dummy && CLI_ISCONTAINED(buf, bufsz, thunk, 4)) {
uint32_t api;
if (!cli_readint32(thunk)) {
workdone = 1;
break;
}
imports = adjbuf + cli_readint32(thunk);
thunk += 4;
dummy = 0;
while (CLI_ISCONTAINED(buf, bufsz, imports, 4)) {
dummy = 0;
imports += 4;
if (!(api = cli_readint32(imports - 4))) {
dummy = 1;
break;
}
if ((api != (api | 0x80000000)) && mangled && --rndm < 0) {
api = virtaddr;
virtaddr += 5; /* EB + 1 double */
rndm = virtaddr & 7;
} else {
api = 0xbff01337; /* KERNEL32!leet */
}
if (sections[sectcount - 1].rva + Imagebase < api)
enc_ep--;
if (api < virtaddr)
enc_ep--;
tmpep = (enc_ep & 0xfffffff8) >> 3 & 0x1fffffff;
enc_ep = (enc_ep & 7) << 29 | tmpep;
}
}
} else
workdone = 1;
enc_ep = pep + 5 + enc_ep;
if (workdone == 1) {
cli_dbgmsg("Petite: Old EP: %x\n", enc_ep);
} else {
enc_ep = usects[0].rva;
cli_dbgmsg("Petite: In troubles while attempting to decrypt old EP, using bogus %x\n", enc_ep);
}
}
/* Let's compact data */
for (t = 0; t < j; t++) {
usects[t].raw = (t > 0) ? (usects[t - 1].raw + usects[t - 1].rsz) : 0;
if (usects[t].rsz != 0) {
if (CLI_ISCONTAINED(buf, bufsz, buf + usects[t].raw, usects[t].rsz)) {
memmove(buf + usects[t].raw, adjbuf + usects[t].rva, usects[t].rsz);
} else {
cli_dbgmsg("Petite: Skipping section %d, Raw: %x, RSize:%x\n", t, usects[t].raw, usects[t].rsz);
usects[t].raw = t > 0 ? usects[t - 1].raw : 0;
usects[t].rsz = 0;
}
}
}
/* Showtime!!! */
cli_dbgmsg("Petite: Sections dump:\n");
for (t = 0; t < j; t++)
cli_dbgmsg("Petite: .SECT%d RVA:%x VSize:%x ROffset: %x, RSize:%x\n", t, usects[t].rva, usects[t].vsz, usects[t].raw, usects[t].rsz);
if (!cli_rebuildpe(buf, usects, j, Imagebase, enc_ep, ResRva, ResSize, desc)) {
cli_dbgmsg("Petite: Rebuilding failed\n");
free(usects);
return 1;
}
free(usects);
return 0;
}
size = srva & 0x7fffffff;
if (srva != size) { /* Test and clear bit 31 */
check4resources = 0;
/*
Enumerates each petite data section
I should get here once ot twice:
- 1 time for the resource section (if present)
- 1 time for the all_the_rest section
*/
if (!CLI_ISCONTAINED(buf, bufsz, packed + 4, 8)) {
if (usects)
free(usects);
return 1;
}
/* Save the end of current packed section for later use */
bottom = cli_readint32(packed + 8) + 4;
ssrc = adjbuf + cli_readint32(packed + 4) - (size - 1) * 4;
ddst = adjbuf + cli_readint32(packed + 8) - (size - 1) * 4;
if (!CLI_ISCONTAINED(buf, bufsz, ssrc, size * 4) || !CLI_ISCONTAINED(buf, bufsz, ddst, size * 4)) {
if (usects)
free(usects);
return 1;
}
/* Copy packed data to the end of the current packed section */
memmove(ddst, ssrc, size * 4);
packed += 0x0c;
} else {
uint32_t check1, check2;
uint8_t mydl = 0;
uint8_t goback;
unsigned int q;
/* Unpack each original section in turn */
if (!CLI_ISCONTAINED(buf, bufsz, packed + 4, 8)) {
if (usects)
free(usects);
return 1;
}
size = cli_readint32(packed + 4); /* How many bytes to unpack */
thisrva = cli_readint32(packed + 8); /* RVA of the original section */
packed += 0x10;
if (j >= 96) {
cli_dbgmsg("Petite: maximum number of sections exceeded, giving up.\n");
free(usects);
return 1;
}
/* Alloc 1 more struct */
if (!(tmpsct = cli_realloc(usects, sizeof(struct cli_exe_section) * (j + 1)))) {
if (usects)
free(usects);
return 1;
}
usects = (struct cli_exe_section *)tmpsct;
/* Save section spex for later rebuilding */
usects[j].rva = thisrva;
usects[j].rsz = size;
if ((int)(bottom - thisrva) > 0)
usects[j].vsz = bottom - thisrva;
else
usects[j].vsz = size;
usects[j].raw = 0; /* Cheaper than memset */
if (!size) { /* That's a ghost section! reloc any1? :P */
j++;
continue;
}
ssrc = adjbuf + srva;
ddst = adjbuf + thisrva;
/* Last petite section (unpacked 1st) could contain unpacked data
* (eg the icon): let's fix the rva
*/
for (q = 0; q < sectcount; q++) {
if (!CLI_ISCONTAINED(sections[q].rva, sections[q].vsz, usects[j].rva, usects[j].vsz))
continue;
if (!check4resources) {
usects[j].rva = sections[q].rva;
usects[j].rsz = thisrva - sections[q].rva + size;
}
break;
}
if (q == sectcount) {
free(usects);
return 1;
}
/* Increase count of unpacked sections */
j++;
/* Setup some crap for later checks */
if (size < 0x10000) {
check1 = 0x0FFFFC060;
check2 = 0x0FFFFFC60;
goback = 5;
} else if (size < 0x40000) {
check1 = 0x0FFFF8180;
check2 = 0x0FFFFF980;
goback = 7;
} else {
check1 = 0x0FFFF8300;
check2 = 0x0FFFFFB00;
goback = 8;
}
/*
* NOTE: on last loop we get esi=edi=ImageBase (which is not writeable)
* The movsb on the next line causes the iat_rebuild_and_decrypt_oldEP()
* func to get called instead... ehehe very smart ;)
*/
if (!CLI_ISCONTAINED(buf, bufsz, ssrc, 1) || !CLI_ISCONTAINED(buf, bufsz, ddst, 1)) {
free(usects);
return 1;
}
size--;
*ddst++ = *ssrc++; /* eheh u C gurus gotta luv these monsters :P */
backbytes = 0;
oldback = 0;
/* No surprises here... NRV any1??? ;) */
while (size > 0) {
oob = doubledl(&ssrc, &mydl, buf, bufsz);
if (oob == -1) {
free(usects);
return 1;
}
if (!oob) {
if (!CLI_ISCONTAINED(buf, bufsz, ssrc, 1) || !CLI_ISCONTAINED(buf, bufsz, ddst, 1)) {
free(usects);
return 1;
}
*ddst++ = (char)((*ssrc++) ^ (size & 0xff));
size--;
} else {
addsize = 0;
backbytes++;
while (1) {
if ((oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1) {
free(usects);
return 1;
}
if (backbytes >= INT_MAX / 2) {
free(usects);
cli_dbgmsg("Petite: probably invalid file\n");
return 1;
}
backbytes = backbytes * 2 + oob;
if ((oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1) {
free(usects);
return 1;
}
if (!oob)
break;
}
backbytes -= 3;
if (backbytes >= 0) {
backsize = goback;
do {
if ((oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1) {
free(usects);
return 1;
}
if (backbytes >= INT_MAX / 2) {
free(usects);
cli_dbgmsg("Petite: probably invalid file\n");
return 1;
}
backbytes = backbytes * 2 + oob;
backsize--;
} while (backsize);
backbytes ^= 0xffffffff;
addsize += 1 + (backbytes < (int)check2) + (backbytes < (int)check1);
oldback = backbytes;
} else {
backsize = backbytes + 1;
backbytes = oldback;
}
if ((oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1) {
free(usects);
return 1;
}
backsize = backsize * 2 + oob;
if ((oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1) {
free(usects);
return 1;
}
backsize = backsize * 2 + oob;
if (!backsize) {
backsize++;
while (1) {
if ((oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1) {
free(usects);
return 1;
}
backsize = backsize * 2 + oob;
if ((oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1) {
free(usects);
return 1;
}
if (!oob)
break;
}
backsize += 2;
}
backsize += addsize;
size -= backsize;
if (!CLI_ISCONTAINED(buf, bufsz, ddst, backsize) || !CLI_ISCONTAINED(buf, bufsz, ddst + backbytes, backsize)) {
free(usects);
return 1;
}
while (backsize--) {
*ddst = *(ddst + backbytes);
ddst++;
}
backbytes = 0;
backsize = 0;
} /* else */
} /* while(ebx) */
/* Any lame petite code here? If so let's strip it
* We've done version adjustments already, see above
*/
if (j) {
int strippetite = 0;
uint32_t reloc;
/* LONG MAGIC = 33C05E64 8B188B1B 8D63D65D */
if (usects[j - 1].rsz > grown &&
CLI_ISCONTAINED(buf, bufsz, ddst - grown + 5 + 0x4f, 8) &&
cli_readint32(ddst - grown + 5 + 0x4f) == 0x645ec033 &&
cli_readint32(ddst - grown + 5 + 0x4f + 4) == 0x1b8b188b) {
reloc = 0;
strippetite = 1;
}
if (!strippetite &&
usects[j - 1].rsz > grown + skew &&
CLI_ISCONTAINED(buf, bufsz, ddst - grown + 5 + 0x4f - skew, 8) &&
cli_readint32(ddst - grown + 5 + 0x4f - skew) == 0x645ec033 &&
cli_readint32(ddst - grown + 5 + 0x4f + 4 - skew) == 0x1b8b188b) {
reloc = skew; /* If the original exe had a .reloc were skewed */
strippetite = 1;
}
if (strippetite && CLI_ISCONTAINED(buf, bufsz, ddst - grown + 0x0f - 8 - reloc, 8)) {
uint32_t test1, test2;
/* REMINDER: DON'T BPX IN HERE U DUMBASS!!!!!!!!!!!!!!!!!!!!!!!! */
test1 = cli_readint32(ddst - grown + 0x0f - 8 - reloc) ^ 0x9d6661aa;
test2 = cli_readint32(ddst - grown + 0x0f - 4 - reloc) ^ 0xe908c483;
cli_dbgmsg("Petite: Found petite code in sect%d(%x). Let's strip it.\n", j - 1, usects[j - 1].rva);
if (test1 == test2 && CLI_ISCONTAINED(buf, bufsz, ddst - grown + 0x0f - reloc, 0x1c0 - 0x0f + 4)) {
irva = cli_readint32(ddst - grown + 0x121 - reloc);
enc_ep = cli_readint32(ddst - grown + 0x0f - reloc) ^ test1;
mangled = ((uint32_t)cli_readint32(ddst - grown + 0x1c0 - reloc) != 0x90909090); /* FIXME: Magic's too short??? */
cli_dbgmsg("Petite: Encrypted EP: %x | Array of imports: %x\n", enc_ep, irva);
}
usects[j - 1].rsz -= grown + reloc;
}
}
check4resources++;
} /* outer else */
} /* while true */
}