/*
* Copyright (C) 2005 aCaB <acab@clamav.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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.
*/
/*
** spin.c
**
** 19/07/2k5 - Finally started coding something
** 21/07/2k5 - Works, started clearing the mess
** 31/07/2k5 - Porting to libclamav
*/
/*
** Unpacks pespin v1.1
**
** Funny thing to reverse
**
** [ A big fat thank to christoph for not letting me give up ]
*/
/*
** TODO ( a fat one ):
**
** OEP restore and unhijacking
** code redir handling (at least near OEP)
** passwd protection (didn't really look at it)
**
** All this stuff really needs a way better emu and a hell of unlaming
** ATM not worth the effort... and pespin v1.3 is out :@
**
*/
#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include "cltypes.h"
#include "pe.h"
#include "rebuildpe.h"
#include "others.h"
#include "spin.h"
#define EC32(x) le32_to_host(x) /* Convert little endian to host */
static char exec86(uint8_t aelle, uint8_t cielle, char *curremu) {
int len = 0;
while (len <0x24) {
uint8_t opcode = curremu[len], support;
len++;
switch (opcode) {
case 0xeb:
len++;
case 0x0a:
len++;
case 0x90:
case 0xf8:
case 0xf9:
break;
case 0x02: /* add al, cl */
aelle+=cielle;
len++;
break;
case 0x2a: /* sub al, cl */
aelle-=cielle;
len++;
break;
case 0x04: /* add al, ?? */
aelle+=curremu[len];
len++;
break;
case 0x2c: /* sub al, ?? */
aelle-=curremu[len];
len++;
break;
case 0x32: /* xor al, cl */
aelle^=cielle;
len++;
break;
case 0x34: /* xor al, ?? */
aelle^=curremu[len];
len++;
break;
case 0xfe: /* inc/dec al */
if ( curremu[len] == '\xc0' ) aelle++;
else aelle--;
len++;
break;
case 0xc0: /* ror/rol al, ?? */
support = curremu[len];
len++;
if ( support == 0xc0 ) ROL(aelle, curremu[len]);
else ROR(aelle, curremu[len]);
len++;
break;
default:
cli_dbgmsg("Bogus opcode %x\n", opcode);
}
}
if ( len!=0x24 || curremu[len]!='\xaa' )
cli_dbgmsg("spin: bad emucode\n"); /* FIXME: I should really give up here */
return aelle;
}
static int doubledl(char **scur, uint8_t *mydlptr, char *buffer, int 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;
}
static int unfsg(char *source, char *dest, int ssize, int dsize) {
uint8_t mydl=0x80;
uint32_t backbytes, backsize, oldback = 0;
char *csrc = source, *cdst = dest;
int oob, lostbit = 1;
/* I assume buffers size is >0 - No checking! */
*cdst++=*csrc++;
while ( 1 ) {
if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
if (oob == -1)
return -1;
/* 164 */
backsize = 0;
if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
if (oob == -1)
return -1;
/* 16a */
backbytes = 0;
if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
if (oob == -1)
return -1;
/* 170 */
lostbit = 1;
backsize++;
backbytes = 0x10;
while ( backbytes < 0x100 ) {
if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
return -1;
backbytes = backbytes*2+oob;
}
backbytes &= 0xff;
if ( ! backbytes ) {
if (cdst >= dest+dsize)
return -1;
*cdst++=0x00;
continue;
} else {
/* repne movsb - FIXME dont remove for now */
}
} else {
/* 18f */
if (csrc >= source+ssize)
return -1;
backbytes = *(unsigned char*)csrc;
backsize = backsize * 2 + (backbytes & 1);
backbytes = (backbytes & 0xff)>>1;
csrc++;
if (! backbytes)
break;
backsize+=2;
oldback = backbytes;
lostbit = 0;
}
} else {
/* 180 */
backsize = 1;
do {
if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
return -1;
backsize = backsize*2+oob;
if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
return -1;
} while (oob);
backsize = backsize - 1 - lostbit;
if (! backsize) {
/* 18a */
backsize = 1;
do {
if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
return -1;
backsize = backsize*2+oob;
if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
return -1;
} while (oob);
backbytes = oldback;
} else {
/* 198 */
if (csrc >= source+ssize)
return -1;
backbytes = *(unsigned char*)csrc;
backbytes += (backsize-1)<<8;
backsize = 1;
csrc++;
do {
if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
return -1;
backsize = backsize*2+oob;
if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
return -1;
} while (oob);
if (backbytes >= 0x7d00)
backsize++;
if (backbytes >= 0x500)
backsize++;
if (backbytes <= 0x7f)
backsize += 2;
oldback = backbytes;
}
lostbit = 0;
}
if ((backsize > (uint32_t)(dest + dsize - cdst)) || (backbytes > (uint32_t)(cdst - dest)))
return -1;
while(backsize--) {
*cdst=*(cdst-backbytes);
cdst++;
}
} else {
/* 15d */
if (cdst < dest || cdst >= dest+dsize || csrc < source || csrc >= source+ssize)
return -1;
*cdst++=*csrc++;
lostbit=1;
}
}
return 0;
}
static uint32_t summit (char *src, int size)
{
uint32_t eax=0xffffffff, ebx=0xffffffff;
int i;
while(size) {
eax ^= *src++<<8 & 0xff00;
eax = eax>>3 & 0x1fffffff;
for (i=0; i<4; i++) {
uint32_t swap;
eax ^= ebx>>8 & 0xff;
eax += 0x7801a108;
eax ^= ebx;
ROR(eax, ebx&0xff);
swap = eax;
eax = ebx;
ebx = swap;
}
size--;
}
return ebx;
}
int unspin(char *src, int ssize, struct pe_image_section_hdr *sections, int sectcnt, uint32_t nep, int desc) {
char *curr, *emu, *ep, *spinned;
char **sects;
int blobsz=0, j;
uint32_t key32, bitmap, bitman;
uint32_t len;
uint8_t key8;
cli_dbgmsg("in unspin\n");
if ( (spinned = (char *) cli_malloc(EC32(sections[sectcnt].SizeOfRawData))) == NULL )
return 1;
memcpy(spinned, src + EC32(sections[sectcnt].PointerToRawData), EC32(sections[sectcnt].SizeOfRawData));
ep = spinned + nep - sections[sectcnt].VirtualAddress;
curr = ep+0xdb; /* HELP: as a general rule, can i do char* math or should use monsters like "&ep[0xdb]" instead? */
if ( *curr != '\xbb' ) {
free(spinned);
cli_dbgmsg("spin: Not spinned or bad version\n");
return 1;
}
key8 = (uint8_t)*++curr;
curr+=4;
if ( *curr != '\xb9' ) {
free(spinned);
cli_dbgmsg("spin: Not spinned or bad version\n");
return 1;
}
if ( (len = cli_readint32(curr+1)) != 0x11fe ) {
free(spinned);
cli_dbgmsg("spin: Not spinned or bad version\n");
return 1;
}
cli_dbgmsg("spin: Key8 is %x, Len is %x\n", key8, len);
if ( (uint32_t)(ep - spinned) >= EC32(sections[sectcnt].SizeOfRawData) - len - 0x1fe5 ) {
free(spinned);
cli_dbgmsg("spin: len out of bounds, giving up\n");
return 1; /* Outta bounds - HELP: i suppose i should check for wraps.. not sure though */
}
if ( ep[0x1e0]!='\xb8' )
cli_dbgmsg("spin: prolly not spinned, expect failure\n");
if ( (cli_readint32(ep+0x1e1) & 0x00200000) )
cli_dbgmsg("spin: password protected, expect failure\n");
curr = ep+0x1fe5+len-1;
while ( len-- ) {
*curr=(*curr)^(key8--);
curr--;
}
curr = ep+0x26eb;
key32 = cli_readint32(curr);
if ( (len = cli_readint32(curr+5)) != 0x5a0) {
free(spinned);
cli_dbgmsg("spin: Not spinned or bad version\n");
return 1;
}
curr = ep+0x2d5; /* 0x2d5+5a0 < 0x3217 - still within bounds (checked by caller) */
cli_dbgmsg("spin: Key is %x, Len is %x\n", key32, len);
while ( len-- ) {
if ( key32 & 1 ) {
key32 = key32>>1&0x7fffffff;
key32 ^= 0x8c328834;
} else {
key32 = key32>>1 & 0x7fffffff;
}
*curr = *curr ^ (key32 & 0xff);
curr++;
}
len = ssize - cli_readint32(ep+0x429); /* sub size, value */
if ( len >= (uint32_t)ssize ) {
free(spinned);
cli_dbgmsg("spin: crc out of bounds, giving up\n");
return 1; /* We wrapped */
}
key32 = cli_readint32(ep+0x3217) - summit(src,len);
memcpy(src + EC32(sections[sectcnt].PointerToRawData), spinned, EC32(sections[sectcnt].SizeOfRawData));
free(spinned); /* done CRC'ing - can have a dirty buffer now */
ep = src + nep + sections[sectcnt].PointerToRawData - sections[sectcnt].VirtualAddress; /* Fix the helper */
bitmap = cli_readint32(ep+0x3207);
cli_dbgmsg("spin: Key32 is %x - XORbitmap is %x\n", key32, bitmap);
cli_dbgmsg("spin: Decrypting sects (xor)\n");
for (j=0; j<sectcnt; j++) {
if (bitmap&1) {
uint32_t size = EC32(sections[j].SizeOfRawData);
char *ptr = src + EC32(sections[j].PointerToRawData);
uint32_t keydup = key32;
if ( EC32(sections[j].PointerToRawData) + size >= (uint32_t)ssize ) {
cli_dbgmsg("spin: sect %d out of file, giving up\n", j);
return 1; /* sect outta bounds - HELP: i suppose i should check for wraps.. not sure though */
}
while (size--) {
if (! (keydup & 1)) {
keydup = keydup>>1&0x7fffffff; /* HELP: clear sign bit for unsigned values too? */
keydup ^= 0xed43af31;
} else {
keydup = keydup>>1 & 0x7fffffff; /* HELP: clear sign bit for unsigned values too? */
}
*ptr = *ptr ^ (keydup & 0xff);
ptr++;
}
}
bitmap = bitmap >>1 & 0x7fffffff; /* HELP: clear sign bit for unsigned values too? */
}
cli_dbgmsg("spin: done\n");
curr = ep+0x644; /* 0x28d3+0x180 < 0x3217 - still within bounds (checked by caller) */
if ( (len = cli_readint32(curr)) != 0x180) {
cli_dbgmsg("spin: Not spinned or bad version\n");
return 1;
}
key32 = cli_readint32(curr+0x0c);
cli_dbgmsg("spin: Key is %x, Len is %x\n", key32, len);
curr = ep+0x28d3;
while ( len-- ) {
if ( key32 & 1 ) {
key32 = key32>>1&0x7fffffff;
key32 ^= 0xed43af32;
} else {
key32 = key32>>1 & 0x7fffffff;
}
*curr = *curr ^ (key32 & 0xff);
curr++;
}
curr = ep+0x28dd;
if ( (len = cli_readint32(curr)) != 0x1a1 ) {
cli_dbgmsg("spin: Not spinned or bad version\n");
return 1;
}
cli_dbgmsg("spin: POLY1 len is %x\n", len);
curr+=0xf; /* POLY1 */
emu = ep+0x6d4; /* Still within bounds */
while (len) {
*emu=exec86(*emu, len-- & 0xff, curr); /* unlame POLY1 */
emu++;
}
bitmap = cli_readint32(ep+0x6f1);
cli_dbgmsg("spin: POLYbitmap is %x - decrypting sects (poly)\n", bitmap);
curr = ep+0x755;
for (j=0; j<sectcnt; j++) {
if (bitmap&1) {
uint32_t notthesamelen = EC32(sections[j].SizeOfRawData);
emu = src + EC32(sections[j].PointerToRawData);
if ( emu < src || EC32(sections[j].PointerToRawData) + notthesamelen >= (uint32_t)ssize) { /* HELP: Is this enough for me to be within bounds? */
cli_dbgmsg("spin: code to exec is out of file?\n");
return 1;
}
while (notthesamelen) {
*emu=exec86(*emu, notthesamelen-- & 0xff, curr);
emu++;
}
}
bitmap = bitmap >>1 & 0x7fffffff;
}
cli_dbgmsg("spin: done\n");
bitmap = cli_readint32(ep+0x3061);
bitman = bitmap;
cli_dbgmsg("spin: Compression bitmap is %x\n", bitmap);
if ( (sects= (char **) cli_malloc(sectcnt*sizeof(char *))) == NULL )
return 1;
len = 0;
for (j=0; j<sectcnt; j++) {
if (bitmap&1) {
if ( (sects[j] = (char *) cli_malloc(EC32(sections[j].VirtualSize)) ) == NULL ) { /* FIXME: use "static" maxmalloc @4380b6 instead??? */
cli_dbgmsg("spin: malloc(%d) failed\n", EC32(sections[j].VirtualSize));
len = 1;
break;
}
blobsz+=EC32(sections[j].VirtualSize);
memset(sects[j], 0, EC32(sections[j].VirtualSize));
cli_dbgmsg("spin: Growing sect%d: was %x will be %x\n", j, EC32(sections[j].SizeOfRawData), EC32(sections[j].VirtualSize));
if ( unfsg(src + EC32(sections[j].PointerToRawData), sects[j], EC32(sections[j].SizeOfRawData), EC32(sections[j].VirtualSize)) == -1 ) {
len++;
cli_dbgmsg("spin: Unpack failure\n");
}
/* sections[j].rsz = sections[j].vsz; FIXME: can't hack the caller, gotta find a better way! */
} else {
blobsz+=EC32(sections[j].SizeOfRawData);
sects[j] = src + EC32(sections[j].PointerToRawData);
cli_dbgmsg("spin: Not growing sect%d\n", j);
}
bitmap = bitmap >>1 & 0x7fffffff;
}
cli_dbgmsg("spin: decompression complete\n");
if ( len ) {
int t;
for (t=0 ; t<j ; t++) {
if (bitman&1)
free(sects[t]);
bitman = bitman >>1 & 0x7fffffff;
}
free(sects);
return 1;
}
key32 = cli_readint32(ep+0x2fee);
if (key32) {
/* len = cli_readint32(ep+0x2fc8); -- Using vsizes instead */
for (j=0; j<sectcnt; j++) {
if (EC32(sections[j].VirtualAddress) <= key32 && EC32(sections[j].VirtualAddress)+EC32(sections[j].SizeOfRawData) > key32) /* HELP: wraps? */
break;
}
if (j!=sectcnt && ((bitman & (1<<j)) == 0)) { /* FIXME: not really sure either the res sect is lamed or just compressed, but this'll save some major headakes */
cli_dbgmsg("spin: Resources (sect%d) appear to be compressed\n\tuncompressed offset %x, len %x\n\tcompressed offset %x, len %x\n", j, EC32(sections[j].VirtualAddress), key32 - EC32(sections[j].VirtualAddress), key32, EC32(sections[j].VirtualSize) - (key32 - EC32(sections[j].VirtualAddress)));
if ( (curr=(char *)cli_malloc(EC32(sections[j].VirtualSize))) != NULL ) {
memcpy(curr, src + EC32(sections[j].PointerToRawData), key32 - EC32(sections[j].VirtualAddress)); /* Uncompressed part */
memset(curr + key32 - EC32(sections[j].VirtualAddress), 0, EC32(sections[j].VirtualSize) - (key32 - EC32(sections[j].VirtualAddress))); /* bzero */
if ( unfsg(src + EC32(sections[j].PointerToRawData) + key32 - EC32(sections[j].VirtualAddress), curr + key32 - EC32(sections[j].VirtualAddress), EC32(sections[j].SizeOfRawData) - (key32 - EC32(sections[j].VirtualAddress)), EC32(sections[j].VirtualSize) - (key32 - EC32(sections[j].VirtualAddress))) ) { /* HELP: i can't read my own line - hope's ok :( */
free(curr);
cli_dbgmsg("spin: Failed to grow resources, continuing anyway\n");
blobsz+=EC32(sections[j].SizeOfRawData);
} else {
sects[j]=curr; /* FIXME: bitman check above should save me from leaks */
bitman|=1<<j;
cli_dbgmsg("spin: Resources grown\n");
blobsz+=EC32(sections[j].VirtualSize);
}
} else {
/* HELP: malloc failed but i'm too deep into this crap to worry... what to do next? */
blobsz+=EC32(sections[j].SizeOfRawData);
}
} else {
cli_dbgmsg("spin: No res?!\n");
}
}
bitmap=bitman; /* save as a free() bitmap */
if ( (ep = (char *) cli_malloc(blobsz)) != NULL ) {
struct SECTION *rebhlp;
if ( (rebhlp = (struct SECTION *) cli_malloc(sizeof(struct SECTION)*(sectcnt))) != NULL ) {
char *to = ep;
int retval = 0;
for (j = 0; j < sectcnt; j++) {
rebhlp[j].raw = (j>0)*(rebhlp[j-1].raw + rebhlp[j-1].rsz);
rebhlp[j].rsz = (bitmap &1) ? EC32(sections[j].VirtualSize) : EC32(sections[j].SizeOfRawData);
rebhlp[j].rva = EC32(sections[j].VirtualAddress);
rebhlp[j].vsz = EC32(sections[j].VirtualSize);
memcpy(to, sects[j], rebhlp[j].rsz);
to+=rebhlp[j].rsz;
if ( bitmap & 1 ) free(sects[j]);
bitmap = bitmap >>1 & 0x7fffffff;
}
if ( (to = rebuildpe(ep, rebhlp, sectcnt, 0x400000, 0x1000, 0, 0))) { /* HELP: should i bother fixing those values? the rebuilt exe is completely broken anyway. */
if (cli_writen(desc, to, 0x148+0x80+0x28*j+rebhlp[j-1].raw+rebhlp[j-1].rsz)==-1) {
cli_dbgmsg("spin: Cannot write unpacked file\n");
retval = 1;
}
free(to);
} else {
cli_dbgmsg("spin: Cannot write unpacked file\n");
retval = 1;
}
free(rebhlp);
free(ep);
free(sects);
return retval;
}
free(ep);
}
cli_dbgmsg ("spin: free bitmap is %x\n", bitman);
for (j=0; j<sectcnt; j++) {
if (bitmap&1) free(sects[j]);
bitman = bitman >>1 & 0x7fffffff;
}
free(sects);
return 1; /* :( */
}