514 lines
16 KiB
C
514 lines
16 KiB
C
/*
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* Copyright (C) 2013-2022 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
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* Copyright (C) 2007-2013 Sourcefire, Inc.
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*
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* Authors: Alberto Wu
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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 version 2 as
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* published by the Free Software Foundation.
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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 "clamav.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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static char exec86(uint8_t aelle, uint8_t cielle, char *curremu, int *retval)
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{
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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')
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aelle++;
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else
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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)
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CLI_ROL(aelle, curremu[len]);
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else
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CLI_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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CLI_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 cli_exe_section *sections, int sectcnt, uint32_t nep, int desc, cli_ctx *ctx)
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{
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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(sections[sectcnt].rsz)) == NULL) {
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cli_dbgmsg("spin: Unable to allocate memory for spinned\n");
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return 1;
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}
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memcpy(spinned, src + sections[sectcnt].raw, sections[sectcnt].rsz);
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ep = spinned + nep - sections[sectcnt].rva;
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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, sections[sectcnt].rsz, 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, sections[sectcnt].rsz, 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 + sections[sectcnt].raw, spinned, sections[sectcnt].rsz);
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free(spinned); /* done CRC'ing - can have a dirty buffer now */
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ep = src + nep + sections[sectcnt].raw - sections[sectcnt].rva; /* 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 = sections[j].rsz;
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char *ptr = src + sections[j].raw;
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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 = sections[j].rsz;
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emu = src + sections[j].raw;
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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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/* FIXMELIMITS: possibly rewrite to use the limits api */
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if (ctx->engine->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->engine->maxfilesize || sections[j].vsz > ctx->engine->maxfilesize - filesize)
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return 2;
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filesize += sections[j].vsz;
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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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cli_dbgmsg("spin: malloc(%zu) failed\n", (size_t)sectcnt * sizeof(char *));
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return 1;
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}
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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(sections[j].vsz)) == NULL) {
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cli_dbgmsg("spin: malloc(%u) failed\n", sections[j].vsz);
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len = 1;
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break;
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}
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blobsz += sections[j].vsz;
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memset(sects[j], 0, sections[j].vsz);
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cli_dbgmsg("spin: Growing sect%d: was %x will be %x\n", j, sections[j].rsz, sections[j].vsz);
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if (cli_unfsg(src + sections[j].raw, sects[j], sections[j].rsz, sections[j].vsz, 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 += sections[j].rsz;
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sects[j] = src + sections[j].raw;
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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 (sections[j].rva <= key32 && key32 - sections[j].rva < sections[j].vsz && CLI_ISCONTAINED(src + sections[j].raw, sections[j].rsz, src + sections[j].raw, key32 - sections[j].rva))
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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 headaches */
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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, sections[j].rva, key32 - sections[j].rva, key32, sections[j].vsz - (key32 - sections[j].rva));
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if ((curr = (char *)cli_malloc(sections[j].vsz)) != NULL) {
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memcpy(curr, src + sections[j].raw, key32 - sections[j].rva); /* Uncompressed part */
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memset(curr + key32 - sections[j].rva, 0, sections[j].vsz - (key32 - sections[j].rva)); /* bzero */
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if (cli_unfsg(src + sections[j].raw + key32 - sections[j].rva, curr + key32 - sections[j].rva, sections[j].rsz - (key32 - sections[j].rva), sections[j].vsz - (key32 - sections[j].rva), 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 += sections[j].rsz;
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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 += sections[j].vsz;
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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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cli_dbgmsg("spin: memory allocation failed, continuing anyway\n");
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blobsz += sections[j].rsz;
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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) : 0;
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rebhlp[j].rsz = (bitmap & 1) ? sections[j].vsz : sections[j].rsz;
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rebhlp[j].rva = sections[j].rva;
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rebhlp[j].vsz = sections[j].vsz;
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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)
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free(sects[j]);
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bitmap = bitmap >> 1;
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}
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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. */
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cli_dbgmsg("spin: Cannot write unpacked file\n");
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retval = 1;
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}
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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; /* :( */
|
|
}
|