504 lines
16 KiB
C
504 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: Luciano Giuseppe 'Pnluck', 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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#include <string.h>
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#include "clamav.h"
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#include "execs.h"
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#include "others.h"
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#include "rebuildpe.h"
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#include "aspack.h"
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#define ASPACK_BLOCKS_OFFSET_212 0x57c
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#define ASPACK_BLOCKS_OFFSET_OTHER 0x5d8
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#define ASPACK_BLOCKS_OFFSET_242 0x5e4
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#define ASPACK_STR_INIT_MLT_OFFSET_212 0x70e
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#define ASPACK_STR_INIT_MLT_OFFSET_OTHER 0x76a
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#define ASPACK_STR_INIT_MLT_OFFSET_242 0x776
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#define ASPACK_COMP_BLOCK_OFFSET_212 0x6d6
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#define ASPACK_COMP_BLOCK_OFFSET_OTHER 0x732
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#define ASPACK_COMP_BLOCK_OFFSET_242 0x73e
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#define ASPACK_WRKBUF_OFFSET_212 0x148
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#define ASPACK_WRKBUF_OFFSET_OTHER 0x13a
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#define ASPACK_WRKBUF_OFFSET_242 0x148
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#define ASPACK_OEP_OFFSET_212 0x39b
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#define ASPACK_OEP_OFFSET_OTHER 0x401
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#define ASPACK_OEP_OFFSET_242 0x40d
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struct DICT_HELPER {
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uint32_t *starts;
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uint8_t *ends;
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uint32_t size;
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};
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struct ASPK {
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uint32_t bitpos;
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uint32_t hash;
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uint32_t init_array[58];
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struct DICT_HELPER dict_helper[4];
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uint8_t *input;
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uint8_t *iend;
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uint8_t *decrypt_dict;
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uint32_t decarray3[4][24];
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uint32_t decarray4[4][24];
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int dict_ok;
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uint8_t array2[758];
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uint8_t array1[19];
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};
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static inline int readstream(struct ASPK *stream)
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{
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while (stream->bitpos >= 8) {
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if (stream->input >= stream->iend) return 0;
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stream->hash = (stream->hash << 8) | *stream->input;
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stream->input++;
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stream->bitpos -= 8;
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}
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return 1;
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}
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static uint32_t getdec(struct ASPK *stream, uint8_t which, int *err)
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{
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uint32_t ret;
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uint8_t pos;
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uint32_t *d3 = stream->decarray3[which];
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uint32_t *d4 = stream->decarray4[which];
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*err = 1;
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if (!readstream(stream)) return 0;
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ret = (stream->hash >> (8 - stream->bitpos)) & 0xfffe00;
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if (ret < d3[8]) {
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if ((ret >> 16) >= 0x100) return 0;
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if (!(pos = stream->dict_helper[which].ends[ret >> 16]) || pos >= 24) return 0; /* 0<pos<24 */
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} else {
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if (ret < d3[10]) {
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if (ret < d3[9])
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pos = 9;
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else
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pos = 10;
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} else {
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if (ret < d3[11])
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pos = 11;
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else {
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if (ret < d3[12])
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pos = 12;
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else {
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if (ret < d3[13])
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pos = 13;
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else {
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if (ret < d3[14])
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pos = 14;
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else
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pos = 15;
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}
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}
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}
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}
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}
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stream->bitpos += pos;
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ret = ((ret - d3[pos - 1]) >> (24 - pos)) + d4[pos];
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if (ret >= stream->dict_helper[which].size) return 0;
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ret = stream->dict_helper[which].starts[ret];
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*err = 0;
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return ret;
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}
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static uint8_t build_decrypt_array(struct ASPK *stream, uint8_t *array, uint8_t which)
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{
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uint32_t sum = 0, counter = 23, i, endoff = 0, bus[18], dict[18];
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uint32_t *d3 = stream->decarray3[which];
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uint32_t *d4 = stream->decarray4[which];
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memset(bus, 0, sizeof(bus));
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memset(dict, 0, sizeof(dict));
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for (i = 0; i < stream->dict_helper[which].size; i++) {
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/* within bounds - see comments in build_decrypt_dictionaries */
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if (array[i] > 17) return 0;
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bus[array[i]]++;
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}
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d3[0] = 0;
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d4[0] = 0;
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i = 0;
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while (counter >= 9) { /* 0<=i<=14 */
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sum += (bus[i + 1] << counter);
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if (sum > 0x1000000) return 0;
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d3[i + 1] = sum;
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d4[i + 1] = dict[i + 1] = bus[i] + d4[i];
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if (counter >= 0x10) {
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uint32_t old = endoff;
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endoff = d3[i + 1] >> 0x10;
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if (endoff - old) {
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if (!CLI_ISCONTAINED(stream->dict_helper[which].ends, 0x100, stream->dict_helper[which].ends + old, endoff - old)) return 0;
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memset((stream->dict_helper[which].ends + old), i + 1, endoff - old);
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}
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}
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i++;
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counter--;
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}
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if (sum != 0x1000000) return 0;
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i = 0;
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for (i = 0; i < stream->dict_helper[which].size; i++) {
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if (array[i]) { /* within bounds - see above */
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if (array[i] > 17) return 0;
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if (dict[array[i]] >= stream->dict_helper[which].size) return 0;
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stream->dict_helper[which].starts[dict[array[i]]] = i;
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dict[array[i]]++;
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}
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}
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return 1;
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}
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static uint8_t getbits(struct ASPK *stream, uint32_t num, int *err)
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{
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uint8_t retvalue;
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if (!readstream(stream)) {
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*err = 1;
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return 0;
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}
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*err = 0;
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retvalue = ((stream->hash >> (8 - stream->bitpos)) & 0xffffff) >> (24 - num);
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stream->bitpos += num;
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return retvalue;
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}
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static int build_decrypt_dictionaries(struct ASPK *stream)
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{
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unsigned int counter;
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uint32_t ret;
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int oob;
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if (!getbits(stream, 1, &oob)) memset(stream->decrypt_dict, 0, 0x2f5);
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if (oob) return 0;
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for (counter = 0; counter < 19; counter++) {
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stream->array1[counter] = getbits(stream, 4, &oob);
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if (oob) return 0;
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}
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if (!build_decrypt_array(stream, stream->array1, 3)) return 0; /* array1[19] - [3].size=19 */
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counter = 0;
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while (counter < 757) {
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ret = getdec(stream, 3, &oob);
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if (oob) return 0;
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if (ret >= 16) {
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if (ret != 16) {
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if (ret == 17)
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ret = 3 + getbits(stream, 3, &oob);
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else
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ret = 11 + getbits(stream, 7, &oob);
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if (oob) return 0;
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while (ret) {
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if (counter >= 757) break;
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stream->array2[1 + counter] = 0;
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counter++;
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ret--;
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}
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} else {
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ret = 3 + getbits(stream, 2, &oob);
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if (oob) return 0;
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while (ret) {
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if (counter >= 757) break;
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stream->array2[1 + counter] = stream->array2[counter];
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counter++;
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ret--;
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}
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}
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} else {
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stream->array2[1 + counter] = (stream->decrypt_dict[counter] + ret) & 0xF;
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counter++;
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}
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}
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if (!build_decrypt_array(stream, &stream->array2[1], 0) /* array2[758-1=757] - [0].size=721 */ || !build_decrypt_array(stream, &stream->array2[722], 1) /* array2[758-722=36] - [1].size=28 */ || !build_decrypt_array(stream, &stream->array2[750], 2) /* array2[758-750=8] - [2].size=8 */) return 0;
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stream->dict_ok = 0;
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for (counter = 0; counter < 8; counter++) {
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if (stream->array2[750 + counter] != 3) {
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stream->dict_ok = 1;
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break;
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}
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}
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memcpy(stream->decrypt_dict, &stream->array2[1], 757);
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return 1;
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}
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static int decrypt(struct ASPK *stream, uint8_t *stuff, uint32_t size, uint8_t *output)
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{
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/* ep+6d6 -> ep+748 = 0x72*/
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uint32_t gen, backsize, backbytes, useold, counter = 0;
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uint32_t hist[4] = {0, 0, 0, 0};
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int oob;
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cli_dbgmsg("Aspack: decrypt size:%x\n", size);
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while (counter < size) {
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gen = getdec(stream, 0, &oob);
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if (oob) return 0;
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if (gen < 256) { /* implied within bounds */
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output[counter] = (uint8_t)gen;
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counter++;
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continue;
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}
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if (gen >= 720) {
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if (!build_decrypt_dictionaries(stream)) return 0;
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continue;
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}
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if ((backbytes = (gen - 256) >> 3) >= 58) return 0; /* checks init_array + stuff */
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backsize = ((gen - 256) & 7) + 2;
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if ((backsize - 2) == 7) {
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uint8_t hlp;
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gen = getdec(stream, 1, &oob);
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if (oob || gen >= 0x56) return 0;
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hlp = stuff[gen + 0x1c];
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if (!readstream(stream)) return 0;
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backsize += stuff[gen] + (((stream->hash >> (8 - stream->bitpos)) & 0xffffff) >> (0x18 - hlp));
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stream->bitpos += hlp;
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}
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useold = stream->init_array[backbytes];
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gen = stuff[backbytes + 0x38];
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if (!stream->dict_ok || gen < 3) {
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if (!readstream(stream)) return 0;
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useold += ((stream->hash >> (8 - stream->bitpos)) & 0xffffff) >> (24 - gen);
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stream->bitpos += gen;
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} else {
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gen -= 3;
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if (!readstream(stream)) return 0;
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useold += ((((stream->hash >> (8 - stream->bitpos)) & 0xffffff) >> (24 - gen)) * 8);
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stream->bitpos += gen;
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useold += getdec(stream, 2, &oob);
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if (oob) return 0;
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}
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if (useold < 3) {
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backbytes = hist[useold];
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if (useold != 0) {
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hist[useold] = hist[0];
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hist[0] = backbytes;
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}
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} else {
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hist[2] = hist[1];
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hist[1] = hist[0];
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hist[0] = backbytes = useold - 3;
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}
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backbytes++;
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if (!backbytes || backbytes > counter || backsize > size - counter) return 0;
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while (backsize--) {
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output[counter] = output[counter - backbytes];
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counter++;
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}
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}
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return 1;
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}
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static int decomp_block(struct ASPK *stream, uint32_t size, uint8_t *stuff, uint8_t *output)
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{
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memset(stream->decarray3, 0, sizeof(stream->decarray3));
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memset(stream->decarray4, 0, sizeof(stream->decarray4));
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memset(stream->decrypt_dict, 0, 757);
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stream->bitpos = 0x20;
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if (!build_decrypt_dictionaries(stream)) return 0;
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return decrypt(stream, stuff, size, output);
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}
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#define INIT_DICT_HELPER(n, sz) \
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stream.dict_helper[n].starts = (uint32_t *)wrkbuf; \
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stream.dict_helper[n].ends = &wrkbuf[sz * sizeof(uint32_t)]; \
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stream.dict_helper[n].size = sz; \
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wrkbuf = &wrkbuf[sz * sizeof(uint32_t) + 0x100];
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int unaspack(uint8_t *image, unsigned int size, struct cli_exe_section *sections, uint16_t sectcount, uint32_t ep, uint32_t base, int f, aspack_version_t version)
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{
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struct ASPK stream;
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uint32_t i = 0, j = 0;
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uint8_t *blocks = NULL, *wrkbuf;
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uint32_t block_rva = 1, block_size;
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struct cli_exe_section *outsects;
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uint32_t blocks_offset, stream_init_multiplier_offset, comp_block_offset, wrkbuf_offset, oep_offset;
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switch (version) {
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case ASPACK_VER_212:
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cli_dbgmsg("Aspack: Attempting to unpack Aspack 2.12.\n");
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blocks_offset = ASPACK_BLOCKS_OFFSET_212;
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stream_init_multiplier_offset = ASPACK_STR_INIT_MLT_OFFSET_212;
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comp_block_offset = ASPACK_COMP_BLOCK_OFFSET_212;
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wrkbuf_offset = ASPACK_WRKBUF_OFFSET_212;
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oep_offset = ASPACK_OEP_OFFSET_212;
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break;
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case ASPACK_VER_OTHER:
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cli_dbgmsg("Aspack: Attempting to unpack Aspack >2.12, <2.42.\n");
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blocks_offset = ASPACK_BLOCKS_OFFSET_OTHER;
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stream_init_multiplier_offset = ASPACK_STR_INIT_MLT_OFFSET_OTHER;
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comp_block_offset = ASPACK_COMP_BLOCK_OFFSET_OTHER;
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wrkbuf_offset = ASPACK_WRKBUF_OFFSET_OTHER;
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oep_offset = ASPACK_OEP_OFFSET_OTHER;
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break;
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case ASPACK_VER_242:
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cli_dbgmsg("Aspack: Attempting to unpack Aspack 2.42.\n");
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blocks_offset = ASPACK_BLOCKS_OFFSET_242;
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stream_init_multiplier_offset = ASPACK_STR_INIT_MLT_OFFSET_242;
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comp_block_offset = ASPACK_COMP_BLOCK_OFFSET_242;
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wrkbuf_offset = ASPACK_WRKBUF_OFFSET_242;
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oep_offset = ASPACK_OEP_OFFSET_242;
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break;
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default:
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cli_dbgmsg("Aspack: Unexpected/Unknown version number.\n");
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return 0;
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}
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blocks = image + ep + blocks_offset;
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if (!(wrkbuf = cli_calloc(0x1800, sizeof(uint8_t)))) {
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cli_dbgmsg("Aspack: Unable to allocate dictionary\n");
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return 0;
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}
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INIT_DICT_HELPER(0, 721); /* dictionary -> dictionary + b44 */
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INIT_DICT_HELPER(1, 28); /* dictionary + c44 -> dictionary + cb4 */
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INIT_DICT_HELPER(2, 8); /* dictionary + db4 -> dictionary + dd4 */
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INIT_DICT_HELPER(3, 19); /* dictionary + ed4 -> dictionary + f20 */
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stream.decrypt_dict = wrkbuf;
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stream.hash = 0x10000;
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for (i = 0; i < 58; i++) {
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stream.init_array[i] = j;
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if (ep + i + stream_init_multiplier_offset < size) {
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j += (1 << image[ep + i + stream_init_multiplier_offset]);
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}
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}
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memset(stream.array1, 0, sizeof(stream.array1));
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memset(stream.array2, 0, sizeof(stream.array2));
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i = 0;
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while (CLI_ISCONTAINED(image, size, blocks, 8) && (block_rva = cli_readint32(blocks)) && (block_size = cli_readint32(blocks + 4)) && CLI_ISCONTAINED(image, size, image + block_rva, block_size)) {
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cli_dbgmsg("Aspack: unpacking block rva:%x - sz:%x\n", block_rva, block_size);
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wrkbuf = (uint8_t *)cli_calloc(block_size + 0x10e, sizeof(uint8_t));
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if (!wrkbuf) {
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cli_dbgmsg("Aspack: Null work buff\n");
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break;
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}
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stream.input = wrkbuf;
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stream.iend = &wrkbuf[block_size + 0x10e];
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memcpy(wrkbuf, image + block_rva, block_size);
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if (!decomp_block(&stream, block_size, &image[ep + comp_block_offset], image + block_rva)) {
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cli_dbgmsg("Aspack: decomp_block failed\n");
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free(wrkbuf);
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break;
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} else
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cli_dbgmsg("Aspack: decomp block succeed\n");
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free(wrkbuf);
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if (i == 0 && block_size > 7) { /* first sect j/c unrolling */
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while (i < block_size - 6) {
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uint8_t curbyte = image[block_rva + i];
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if (curbyte == 0xe8 || curbyte == 0xe9) {
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wrkbuf = &image[block_rva + i + 1];
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if (*wrkbuf == image[ep + wrkbuf_offset]) {
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uint32_t target = cli_readint32(wrkbuf) & 0xffffff00;
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CLI_ROL(target, 0x18);
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cli_writeint32(wrkbuf, target - i);
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i += 4;
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}
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}
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i++;
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}
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}
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if (version == ASPACK_VER_212) {
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blocks += 8;
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} else {
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blocks += 12;
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block_size = cli_readint32(blocks + 4);
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while (!((block_size + 0x10e) & 0xffffffff)) {
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blocks += 12;
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block_size = cli_readint32(blocks + 4);
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}
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}
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}
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cli_dbgmsg("Aspack: leaving loop all uncompressed\n");
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free(stream.dict_helper[0].starts);
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if (block_rva) {
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cli_dbgmsg("Aspack: unpacking failure\n");
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return 0;
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}
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if (sectcount > 2 && ep == sections[sectcount - 2].rva && !sections[sectcount - 1].rsz) {
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sectcount -= 2;
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}
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if (!(outsects = cli_malloc(sizeof(struct cli_exe_section) * sectcount))) {
|
|
cli_dbgmsg("Aspack: OOM - rebuild failed\n");
|
|
cli_writen(f, image, size);
|
|
return 1; /* No whatsoheader - won't infloop in pe.c */
|
|
}
|
|
memcpy(outsects, sections, sizeof(struct cli_exe_section) * sectcount);
|
|
for (i = 0; i < sectcount; i++) {
|
|
outsects[i].raw = outsects[i].rva;
|
|
outsects[i].rsz = outsects[i].vsz;
|
|
}
|
|
|
|
if (!cli_rebuildpe((char *)image, outsects, sectcount, base, cli_readint32(image + ep + oep_offset), 0, 0, f)) {
|
|
cli_dbgmsg("Aspack: rebuild failed\n");
|
|
cli_writen(f, image, size);
|
|
} else {
|
|
cli_dbgmsg("Aspack: successfully rebuilt\n");
|
|
}
|
|
free(outsects);
|
|
return 1;
|
|
}
|