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507 lines
14 KiB
507 lines
14 KiB
/*
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* Copyright (C) 2005 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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** spin.c
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**
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** 19/07/2k5 - Finally started coding something
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** 21/07/2k5 - Works, started clearing the mess
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** 31/07/2k5 - Porting to libclamav
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*/
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/*
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** Unpacks pespin v1.1
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**
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** Funny thing to reverse
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**
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** [ A big fat thank to christoph for not letting me give up ]
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*/
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/*
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** TODO ( a fat one ):
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**
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** OEP restore and unhijacking
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** code redir handling (at least near OEP)
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** passwd protection (didn't really look at it)
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**
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** All this stuff really needs a way better emu and a hell of unlaming
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** ATM not worth the effort... and pespin v1.3 is out :@
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**
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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 "pe.h"
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#include "rebuildpe.h"
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#include "execs.h"
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#include "others.h"
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#include "packlibs.h"
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#include "spin.h"
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#define EC32(x) le32_to_host(x) /* Convert little endian to host */
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static char exec86(uint8_t aelle, uint8_t cielle, char *curremu, int *retval) {
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int len = 0;
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*retval=0;
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while (len <0x24) {
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uint8_t opcode = curremu[len], support;
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len++;
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switch (opcode) {
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case 0xeb:
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len++;
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case 0x0a:
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len++;
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case 0x90:
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case 0xf8:
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case 0xf9:
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break;
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case 0x02: /* add al, cl */
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aelle+=cielle;
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len++;
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break;
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case 0x2a: /* sub al, cl */
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aelle-=cielle;
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len++;
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break;
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case 0x04: /* add al, ?? */
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aelle+=curremu[len];
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len++;
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break;
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case 0x2c: /* sub al, ?? */
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aelle-=curremu[len];
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len++;
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break;
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case 0x32: /* xor al, cl */
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aelle^=cielle;
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len++;
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break;
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case 0x34: /* xor al, ?? */
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aelle^=curremu[len];
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len++;
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break;
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case 0xfe: /* inc/dec al */
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if ( curremu[len] == '\xc0' ) aelle++;
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else aelle--;
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len++;
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break;
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case 0xc0: /* ror/rol al, ?? */
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support = curremu[len];
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len++;
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if ( support == 0xc0 ) ROL(aelle, curremu[len]);
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else ROR(aelle, curremu[len]);
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len++;
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break;
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default:
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cli_dbgmsg("spin: bogus opcode %x\n", opcode);
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*retval=1;
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return aelle;
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}
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}
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if ( len!=0x24 || curremu[len]!='\xaa' ) {
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cli_dbgmsg("spin: bad emucode\n");
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*retval=1;
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}
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return aelle;
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}
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static uint32_t summit (char *src, int size)
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{
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uint32_t eax=0xffffffff, ebx=0xffffffff;
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int i;
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while(size) {
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eax ^= *src++<<8 & 0xff00;
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eax = eax>>3 & 0x1fffffff;
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for (i=0; i<4; i++) {
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uint32_t swap;
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eax ^= ebx>>8 & 0xff;
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eax += 0x7801a108;
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eax ^= ebx;
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ROR(eax, ebx&0xff);
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swap = eax;
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eax = ebx;
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ebx = swap;
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}
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size--;
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}
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return ebx;
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}
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int unspin(char *src, int ssize, struct pe_image_section_hdr *sections, int sectcnt, uint32_t nep, int desc, cli_ctx *ctx) {
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char *curr, *emu, *ep, *spinned;
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char **sects;
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int blobsz=0, j;
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uint32_t key32, bitmap, bitman;
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uint32_t len;
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uint8_t key8;
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cli_dbgmsg("in unspin\n");
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if ( (spinned = (char *) cli_malloc(EC32(sections[sectcnt].SizeOfRawData))) == NULL )
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return 1;
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memcpy(spinned, src + EC32(sections[sectcnt].PointerToRawData), EC32(sections[sectcnt].SizeOfRawData));
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ep = spinned + nep - sections[sectcnt].VirtualAddress;
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curr = ep+0xdb;
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if ( *curr != '\xbb' ) {
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free(spinned);
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cli_dbgmsg("spin: Not spinned or bad version\n");
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return 1;
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}
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key8 = (uint8_t)*++curr;
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curr+=4;
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if ( *curr != '\xb9' ) {
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free(spinned);
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cli_dbgmsg("spin: Not spinned or bad version\n");
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return 1;
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}
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if ( (len = cli_readint32(curr+1)) != 0x11fe ) {
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free(spinned);
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cli_dbgmsg("spin: Not spinned or bad version\n");
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return 1;
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}
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cli_dbgmsg("spin: Key8 is %x, Len is %x\n", key8, len);
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if (!CLI_ISCONTAINED(spinned, EC32(sections[sectcnt].SizeOfRawData), ep, len+0x1fe5-1)) {
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free(spinned);
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cli_dbgmsg("spin: len out of bounds, giving up\n");
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return 1;
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}
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if ( ep[0x1e0]!='\xb8' )
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cli_dbgmsg("spin: prolly not spinned, expect failure\n");
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if ( (cli_readint32(ep+0x1e1) & 0x00200000) )
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cli_dbgmsg("spin: password protected, expect failure\n");
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curr = ep+0x1fe5+len-1;
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while ( len-- ) {
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*curr=(*curr)^(key8--);
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curr--;
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}
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if (!CLI_ISCONTAINED(spinned, EC32(sections[sectcnt].SizeOfRawData), ep+0x3217, 4)) {
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free(spinned);
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cli_dbgmsg("spin: key out of bounds, giving up\n");
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return 1;
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}
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curr = ep+0x26eb;
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key32 = cli_readint32(curr);
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if ( (len = cli_readint32(curr+5)) != 0x5a0) {
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free(spinned);
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cli_dbgmsg("spin: Not spinned or bad version\n");
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return 1;
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}
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curr = ep+0x2d5;
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cli_dbgmsg("spin: Key is %x, Len is %x\n", key32, len);
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while ( len-- ) {
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if ( key32 & 1 ) {
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key32 = key32>>1;
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key32 ^= 0x8c328834;
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} else {
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key32 = key32>>1;
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}
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*curr = *curr ^ (key32 & 0xff);
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curr++;
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}
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len = ssize - cli_readint32(ep+0x429); /* sub size, value */
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if ( len >= (uint32_t)ssize ) {
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free(spinned);
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cli_dbgmsg("spin: crc out of bounds, giving up\n");
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return 1;
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}
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key32 = cli_readint32(ep+0x3217) - summit(src,len);
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memcpy(src + EC32(sections[sectcnt].PointerToRawData), spinned, EC32(sections[sectcnt].SizeOfRawData));
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free(spinned); /* done CRC'ing - can have a dirty buffer now */
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ep = src + nep + sections[sectcnt].PointerToRawData - sections[sectcnt].VirtualAddress; /* Fix the helper */
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if (!CLI_ISCONTAINED(src, ssize, ep+0x3207, 4)) { /* this one holds all ep based checks */
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cli_dbgmsg("spin: key out of bounds, giving up\n");
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return 1;
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}
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bitmap = cli_readint32(ep+0x3207);
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cli_dbgmsg("spin: Key32 is %x - XORbitmap is %x\n", key32, bitmap);
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cli_dbgmsg("spin: Decrypting sects (xor)\n");
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for (j=0; j<sectcnt; j++) {
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if (bitmap&1) {
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uint32_t size = EC32(sections[j].SizeOfRawData);
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char *ptr = src + EC32(sections[j].PointerToRawData);
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uint32_t keydup = key32;
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if (!CLI_ISCONTAINED(src, ssize, ptr, size)) {
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cli_dbgmsg("spin: sect %d out of file, giving up\n", j);
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return 1; /* FIXME: Already checked in pe.c? */
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}
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while (size--) {
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if (! (keydup & 1)) {
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keydup = keydup>>1;
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keydup ^= 0xed43af31;
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} else {
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keydup = keydup>>1;
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}
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*ptr = *ptr ^ (keydup & 0xff);
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ptr++;
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}
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}
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bitmap = bitmap >>1;
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}
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cli_dbgmsg("spin: done\n");
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curr = ep+0x644;
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if ( (len = cli_readint32(curr)) != 0x180) {
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cli_dbgmsg("spin: Not spinned or bad version\n");
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return 1;
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}
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key32 = cli_readint32(curr+0x0c);
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cli_dbgmsg("spin: Key is %x, Len is %x\n", key32, len);
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curr = ep+0x28d3;
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if (!CLI_ISCONTAINED(src, ssize, curr, len)) { /* always true but i may decide to remove the previous check */
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cli_dbgmsg("spin: key out of bounds, giving up\n");
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return 1;
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}
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while ( len-- ) {
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if ( key32 & 1 ) {
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key32 = key32>>1;
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key32 ^= 0xed43af32;
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} else {
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key32 = key32>>1;
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}
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*curr = *curr ^ (key32 & 0xff);
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curr++;
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}
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curr = ep+0x28dd;
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if ( (len = cli_readint32(curr)) != 0x1a1 ) {
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cli_dbgmsg("spin: Not spinned or bad version\n");
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return 1;
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}
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cli_dbgmsg("spin: POLY1 len is %x\n", len);
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curr+=0xf; /* POLY1 */
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emu = ep+0x6d4;
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if (!CLI_ISCONTAINED(src, ssize, emu, len)) {
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cli_dbgmsg("spin: poly1 out of bounds\n");
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return 1;
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}
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while (len) {
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int xcfailure=0;
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*emu=exec86(*emu, len-- & 0xff, curr, &xcfailure); /* unlame POLY1 */
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if (xcfailure) {
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cli_dbgmsg("spin: cannot exec poly1\n");
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return 1;
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}
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emu++;
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}
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bitmap = cli_readint32(ep+0x6f1);
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cli_dbgmsg("spin: POLYbitmap is %x - decrypting sects (poly)\n", bitmap);
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curr = ep+0x755;
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for (j=0; j<sectcnt; j++) {
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if (bitmap&1) {
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uint32_t notthesamelen = EC32(sections[j].SizeOfRawData);
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emu = src + EC32(sections[j].PointerToRawData);
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if (!CLI_ISCONTAINED(src,ssize,curr,0x24)) { /* section bounds already checked twice now */
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cli_dbgmsg("spin: poly1 emucode is out of file?\n");
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return 1;
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}
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while (notthesamelen) {
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int xcfailure=0;
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*emu=exec86(*emu, notthesamelen-- & 0xff, curr, &xcfailure);
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if (xcfailure) {
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cli_dbgmsg("spin: cannot exec section\n");
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return 1;
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}
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emu++;
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}
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}
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bitmap = bitmap >>1;
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}
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cli_dbgmsg("spin: done\n");
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bitmap = cli_readint32(ep+0x3061);
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bitman = bitmap;
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if(ctx->limits && ctx->limits->maxfilesize) {
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unsigned long int filesize = 0;
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for (j=0; j<sectcnt; j++) {
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if (bitmap&1) {
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if ( filesize > ctx->limits->maxfilesize || (uint32_t)EC32(sections[j].VirtualSize) > ctx->limits->maxfilesize - filesize ) return 2;
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filesize += (uint32_t)EC32(sections[j].VirtualSize);
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}
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bitmap>>=1;
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}
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bitmap = bitman;
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}
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cli_dbgmsg("spin: Compression bitmap is %x\n", bitmap);
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if ( (sects= (char **) cli_malloc(sectcnt*sizeof(char *))) == NULL )
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return 1;
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len = 0;
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for (j=0; j<sectcnt; j++) {
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if (bitmap&1) {
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if ( (sects[j] = (char *) cli_malloc(EC32(sections[j].VirtualSize)) ) == NULL ) {
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cli_dbgmsg("spin: malloc(%d) failed\n", EC32(sections[j].VirtualSize));
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len = 1;
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break;
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}
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blobsz+=EC32(sections[j].VirtualSize);
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memset(sects[j], 0, EC32(sections[j].VirtualSize));
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cli_dbgmsg("spin: Growing sect%d: was %x will be %x\n", j, EC32(sections[j].SizeOfRawData), EC32(sections[j].VirtualSize));
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if ( cli_unfsg(src + EC32(sections[j].PointerToRawData), sects[j], EC32(sections[j].SizeOfRawData), EC32(sections[j].VirtualSize), NULL, NULL) == -1 ) {
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len++;
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cli_dbgmsg("spin: Unpack failure\n");
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}
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} else {
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blobsz+=EC32(sections[j].SizeOfRawData);
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sects[j] = src + EC32(sections[j].PointerToRawData);
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cli_dbgmsg("spin: Not growing sect%d\n", j);
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}
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bitmap>>=1;
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}
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cli_dbgmsg("spin: decompression complete\n");
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if ( len ) {
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int t;
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for (t=0 ; t<j ; t++) {
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if (bitman&1)
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free(sects[t]);
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bitman = bitman >>1 & 0x7fffffff;
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}
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free(sects);
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return 1;
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}
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key32 = cli_readint32(ep+0x2fee);
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if (key32) {
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/* len = cli_readint32(ep+0x2fc8); -- Using vsizes instead */
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for (j=0; j<sectcnt; j++) {
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if (EC32(sections[j].VirtualAddress) <= key32 && EC32(sections[j].VirtualAddress)+EC32(sections[j].SizeOfRawData) > key32)
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break;
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}
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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 */
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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)));
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if ( (curr=(char *)cli_malloc(EC32(sections[j].VirtualSize))) != NULL ) {
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memcpy(curr, src + EC32(sections[j].PointerToRawData), key32 - EC32(sections[j].VirtualAddress)); /* Uncompressed part */
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memset(curr + key32 - EC32(sections[j].VirtualAddress), 0, EC32(sections[j].VirtualSize) - (key32 - EC32(sections[j].VirtualAddress))); /* bzero */
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if ( cli_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)), NULL, NULL) ) {
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free(curr);
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cli_dbgmsg("spin: Failed to grow resources, continuing anyway\n");
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blobsz+=EC32(sections[j].SizeOfRawData);
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} else {
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sects[j]=curr;
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bitman|=1<<j;
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cli_dbgmsg("spin: Resources grown\n");
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blobsz+=EC32(sections[j].VirtualSize);
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}
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} else {
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/* malloc failed but i'm too deep into this crap to quit without leaking more :( */
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blobsz+=EC32(sections[j].SizeOfRawData);
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}
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} else {
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cli_dbgmsg("spin: No res?!\n");
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}
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}
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bitmap=bitman; /* save as a free() bitmap */
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if ( (ep = (char *) cli_malloc(blobsz)) != NULL ) {
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struct cli_exe_section *rebhlp;
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if ( (rebhlp = (struct cli_exe_section *) cli_malloc(sizeof(struct cli_exe_section)*(sectcnt))) != NULL ) {
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char *to = ep;
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int retval = 0;
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for (j = 0; j < sectcnt; j++) {
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rebhlp[j].raw = (j>0)*(rebhlp[j-1].raw + rebhlp[j-1].rsz);
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rebhlp[j].rsz = (bitmap &1) ? EC32(sections[j].VirtualSize) : EC32(sections[j].SizeOfRawData);
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rebhlp[j].rva = EC32(sections[j].VirtualAddress);
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rebhlp[j].vsz = EC32(sections[j].VirtualSize);
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memcpy(to, sects[j], rebhlp[j].rsz);
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to+=rebhlp[j].rsz;
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if ( bitmap & 1 ) free(sects[j]);
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bitmap = bitmap >>1;
|
|
}
|
|
|
|
if (! cli_rebuildpe(ep, rebhlp, sectcnt, 0x400000, 0x1000, 0, 0, desc)) { /* can't be bothered fixing those values: the rebuilt exe is completely broken anyway. */
|
|
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; /* :( */
|
|
}
|
|
|