331 lines
10 KiB
C
331 lines
10 KiB
C
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/*
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* Copyright (C) 2021-2022 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
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* Copyright (C) 2005-2010 Gianluigi Tiesi <sherpya@netfarm.it>
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*
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* Authors: Gianluigi Tiesi
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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 "exescanner.h"
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/* -1 = wildchar - -2 = stop here */
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sigs_t signatures[] = {
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{{0x60, 0xbe, -1, -1, -1, -1, 0x8d, 0xbe, -1, -1, -1, 0xff, 0x57, -2},
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"UPX",
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.0f},
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{{0x94, 0xbc, 0x5d, 0x07, 0x42, 0x00, 0xb9, 0x1d, 0x00, 0x00, 0x00, 0x80,
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0x34, 0x0c, 0x44, 0xe2},
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"UPXSHiT",
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.0f},
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{{0xbe, 0xa4, 0x01, 0x40, 0x00, 0xad, 0x93, 0xad, 0x97, 0xad, 0x56, 0x96,
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0xb2, 0x80, 0xa4, 0xb6},
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"FSG 1.33",
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.0f},
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{{0x4d, 0x5a, -1, -1, -1, -1, -1, -1, -1, -1, 0x00, 0x00, 0x50, 0x45, 0x00,
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0x00},
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"FSG 2.00",
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.0f},
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{{0x4d, 0x5a, 0x4b, 0x45, 0x52, 0x4e, 0x45, 0x4c, 0x33, 0x32, 0x2e, 0x44,
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0x4c, 0x4c, 0x00, 0x00},
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"WinUpack 0.39",
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.0f},
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{{0xbe, 0x88, 0x01, 0x40, 0x00, 0xad, 0x8b, 0xf8, 0x95, 0xad, 0x91, 0xf3,
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0xa5, 0xad, 0xb5, 0x1c},
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"Upack 2.4/2.9",
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.0f},
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{{0xbe, 0x48, 0x01, 0x40, 0x00, 0xad, 0x8b, 0xf8, 0x95, 0xa5, 0x33, 0xc0,
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0x33, 0xc9, 0xab, 0x48},
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"Upack 1.1/1.2",
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.0f},
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{{0x83, 0xec, 0x20, 0x53, 0x55, 0x56, 0x33, 0xdb, 0x57, 0x89, 0x5c, 0x24,
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0x18, 0xc7, 0x44, 0x24},
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"NullSoft PiMP",
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.0f},
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{{0xe9, -1, -1, -1, 0xff, 0x0c, -1, -1, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00},
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"Mew 11 1.2",
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.0f},
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{{0x60, 0xe9, 0x3d, 0x04, 0x00, 0x00, -2}, "ASPack 2.11", .0f},
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{{0x60, 0xe8, 0x03, 0x00, 0x00, 0x00, 0xe9, 0xeb, 0x04, 0x5d, 0x45, 0x55,
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0xc3, 0xe8, 0x01, 0x00},
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"ASPack 2.12",
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.0f},
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{{0x55, 0x83, 0xc4, 0x04, 0x76, 0x08, 0x7a, 0x06, 0x74, 0x04, 0x66, 0x83,
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0xea, 0x00, 0xf5, 0x50},
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"Morphine 1.4/2.7",
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.0f},
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{{0x56, 0x72, 0x05, 0x05, 0x00, 0x00, 0x00, 0x00, 0x5e, 0x0b, 0xd2, 0xf9,
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0x84, 0xdb, 0x68, 0x34},
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"Morphine 1.4/2.7 [2]",
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.0f},
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{{0x53, 0x51, 0x52, 0x56, 0x57, 0x55, 0xe8, 0x00, 0x00, 0x00, 0x00, 0x5d,
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0x8b, 0xd5, 0x81, 0xed},
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"PEDiminisher 0.1",
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.0f},
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{{0xe8, 0xf6, 0x03, 0x00, 0x00, 0xe9, 0x9e, 0xfd, 0xff, 0xff, 0xcc, 0xcc,
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0xcc, 0xcc, 0xcc, 0xcc},
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"MSVC8 Release",
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-1.0f},
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{{0xe9, -1, -1, -1, 0x00, 0xe9, -1, -1, -1, 0x00, 0xe9, -1, -1, -1, 0x00,
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0xe9},
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"MSVC8 Debug",
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-1.0f},
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{{0xe8, -1, -1, 0x00, 0x00, 0xe9, 0x16, 0xfe, 0xff, 0xff, -2},
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"MSVC6 Release",
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-2.0f},
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{{0xe9, 0x96, 0xee, 0x0e, 0x00, 0xb8, 0x6c, 0x02, 0x58, 0x00, 0xe8, 0xae,
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0xe4, 0x0e, 0x00, 0x83},
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"MSVC6 Release (2)",
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-1.0f},
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{{0x55, 0x8b, 0xec, 0x6a, 0xff, 0x68, 0xb0, 0x41, 0x40, 0x00, 0x68, 0x10,
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0x36, 0x40, 0x00, 0x64},
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"MSVC6 Release (3)",
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-1.0f},
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{{0x55, 0x8b, 0xec, 0x53, 0x8b, 0x5d, 0x08, 0x56, 0x8b, 0x75, 0x0c, 0x57,
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0x8b, 0x7d, 0x10, 0x85},
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"MSVC6 Release (4)",
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-1.0f},
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{{0x83, 0x7c, 0x24, 0x08, 0x01, 0x75, 0x05, 0xe8, -1, -1, 0x00, 0x00, 0xff,
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0x74, 0x24, 0x04},
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"MSVC6 Release DLL",
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-1.0f},
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{{0xff, 0x25, -1, -1, -1, -1, 0xcc, 0xcc, 0x03, 0x30, 0x01, 0x00, 0x07,
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0x00, 0x00, 0x00},
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"DotNet",
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-1.0f},
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{{0x55, 0x89, 0xe5, -2}, "MinGW", -1.0f},
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{{0}, 0, 0}};
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int sigcmp(const uint8_t *data, const int16_t *sig, size_t n)
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{
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uint8_t *d = (uint8_t *)data;
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int16_t *s = (int16_t *)sig;
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while (n-- != 0) {
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if (*s == -2)
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return 0;
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if ((*s != -1) && (*d != *s))
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return (*d < *s) ? -1 : +1;
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d++;
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s++;
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}
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return 0;
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}
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sigs_t *checksig(uint8_t *data)
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{
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int i = 0;
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while (signatures[i].name) {
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if (!sigcmp(data, signatures[i].sig, 16))
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return &signatures[i];
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i++;
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}
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return NULL;
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}
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double calc_entropy(const unsigned char *data, size_t size)
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{
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double entropy = .0f;
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size_t p[256];
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size_t c, i;
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memset(p, 0, sizeof(p));
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for (c = 0; c < size; c++)
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p[data[c]]++;
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for (i = 0; i < 256; i++)
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if (p[i])
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entropy -= ((double)p[i] / size) * log((double)p[i] / size);
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return entropy;
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}
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#define FILLBYTES(dst) \
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if (IsBadReadPtr(seek, sizeof(dst))) { \
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logg(LOGG_ERROR, "exeScanner: Bad pointer!!!\n"); \
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goto cleanup; \
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} \
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memcpy(&dst, seek, sizeof(dst));
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/* Packed exe heuristic detection, errors are handled as like of non packed data
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*/
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int is_packed(const char *filename)
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{
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int packed = 0;
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int i = 0, c = 0;
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int badsection = 0;
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double entropy = 0.0;
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sigs_t *sig = NULL;
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uint16_t e_mz;
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uint32_t e_lfanew, e_magic;
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uint32_t epoff = 0;
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unsigned char *seek = NULL, *s_start = NULL, *ep = NULL, *lpMapAddress = NULL;
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PIMAGE_FILE_HEADER pehdr;
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PIMAGE_OPTIONAL_HEADER32 opthdr;
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PIMAGE_SECTION_HEADER sechdr;
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char secname[IMAGE_SIZEOF_SHORT_NAME];
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HANDLE hFile = INVALID_HANDLE_VALUE, hMapFile = NULL;
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hFile = CreateFileA(filename, GENERIC_READ, 0, NULL, OPEN_ALWAYS,
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FILE_ATTRIBUTE_NORMAL, NULL);
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if (hFile == INVALID_HANDLE_VALUE) {
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elogg(LOGG_INFO, "exeScanner: CreateFileA failed %lu\n", GetLastError());
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return packed; /* Returning packed, the module is loaded so it must exists
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on disk */
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}
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hMapFile = CreateFileMappingA(hFile, NULL, PAGE_READONLY, 0, 0, "exeScanner");
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if (!hMapFile) {
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elogg(LOGG_INFO, "exeScanner: CreateFileMappingA() failed %lu\n", GetLastError());
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goto cleanup;
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}
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lpMapAddress = (LPBYTE)MapViewOfFile(hMapFile, FILE_MAP_READ, 0, 0, 0);
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if (!lpMapAddress) {
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elogg(LOGG_INFO, "exeScanner: MapViewOfFile() failed %lu\n", GetLastError());
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goto cleanup;
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}
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seek = lpMapAddress;
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/* DOS Signature 'MZ' */
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FILLBYTES(e_mz);
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if (e_mz != IMAGE_DOS_SIGNATURE) {
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elogg(LOGG_INFO, "exeScanner: DOS Signature not found\n");
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goto cleanup;
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}
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seek += 0x3c;
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FILLBYTES(e_lfanew);
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if (!e_lfanew) {
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elogg(LOGG_INFO, "exeScanner: Invalid PE offset\n");
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goto cleanup;
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}
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seek = lpMapAddress + e_lfanew;
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/* PE Signature 'PE' */
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FILLBYTES(e_magic);
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if (e_magic != IMAGE_NT_SIGNATURE) {
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elogg(LOGG_INFO, "exeScanner: PE Signature not found\n");
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goto cleanup;
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}
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seek += sizeof(e_magic);
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if (IsBadReadPtr(seek, sizeof(IMAGE_FILE_HEADER)))
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goto cleanup;
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pehdr = (PIMAGE_FILE_HEADER)seek;
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seek += sizeof(IMAGE_FILE_HEADER);
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if (IsBadReadPtr(seek, sizeof(IMAGE_OPTIONAL_HEADER32)))
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goto cleanup;
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opthdr = (PIMAGE_OPTIONAL_HEADER32)seek;
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seek += sizeof(IMAGE_OPTIONAL_HEADER32);
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if (pehdr->Machine != IMAGE_FILE_MACHINE_I386) {
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elogg(LOGG_INFO, "exeScanner: Not an x86 executable\n");
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goto cleanup;
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}
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/* Invalid sections number */
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if ((pehdr->NumberOfSections < 1) || (pehdr->NumberOfSections > 32)) {
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elogg(LOGG_INFO, "exeScanner: Invalid sections number\n");
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packed = 1;
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goto cleanup;
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}
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for (i = 0; i < pehdr->NumberOfSections; i++) {
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double section_entropy = .0f;
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if (IsBadReadPtr(seek, sizeof(IMAGE_SECTION_HEADER)))
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goto cleanup;
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sechdr = (PIMAGE_SECTION_HEADER)seek;
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seek += sizeof(IMAGE_SECTION_HEADER);
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if (opthdr->AddressOfEntryPoint >= sechdr->VirtualAddress)
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epoff = opthdr->AddressOfEntryPoint - sechdr->VirtualAddress +
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sechdr->PointerToRawData;
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s_start = lpMapAddress + sechdr->PointerToRawData;
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if (!IsBadReadPtr(s_start, sechdr->SizeOfRawData))
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section_entropy = calc_entropy(s_start, sechdr->SizeOfRawData);
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entropy = MAX(entropy, section_entropy);
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/* Sanitize the section name */
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memcpy(secname, sechdr->Name, IMAGE_SIZEOF_SHORT_NAME);
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for (c = 0; (c < IMAGE_SIZEOF_SHORT_NAME) && secname[c]; c++)
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if (!isprint(secname[c]))
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secname[c] = '?';
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secname[IMAGE_SIZEOF_SHORT_NAME - 1] = 0;
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elogg(LOGG_INFO, "exeScanner: Section name: [%s] - Entropy %f\n", secname,
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section_entropy);
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if (!sechdr->SizeOfRawData)
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badsection = 1;
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}
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elogg(LOGG_INFO, "exeScanner: Max entropy = %f\n", entropy);
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/* EP Check */
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elogg(LOGG_INFO, "exeScanner: Entry Point rva: 0x%lx - raw: 0x%lx\n",
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opthdr->AddressOfEntryPoint, epoff);
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ep = lpMapAddress + epoff;
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if (!IsBadReadPtr(ep, EP_SIGNATURE_SIZE)) {
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#ifdef DUMP_SIGNATURE
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int i;
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for (i = 0; i < EP_SIGNATURE_SIZE; i++)
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elogg(LOGG_INFO, "%02x ", ep[i]);
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elogg(LOGG_INFO, "\n[C Code]: ");
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for (i = 0; i < EP_SIGNATURE_SIZE - 1; i++)
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elogg(LOGG_INFO, "0x%02x, ", ep[i]);
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elogg(LOGG_INFO, "0x%02x\n", ep[i]);
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#endif
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if ((sig = checksig(ep))) {
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elogg(LOGG_INFO, "exeScanner: Signature check: %s\n", sig->name);
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entropy += sig->score;
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packed = (sig->score >= .0f);
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if (sig->score < .0f)
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elogg(
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"exeScanner: Whitelisted signature found, lowering entropy to %f\n",
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entropy);
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} else
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elogg(LOGG_INFO, "exeScanner: Signature check: Nothing found\n");
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} else
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elogg(LOGG_INFO, "exeScanner: Invalid address of Entry Point\n");
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if (badsection) {
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if ((entropy == .0f) || (entropy > ENTROPY_THRESHOLD)) {
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elogg(LOGG_INFO, "exeScanner: found zero SizeOfRawData and entropy %f\n", entropy);
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|
|
packed = 1;
|
||
|
|
goto cleanup;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
cleanup:
|
||
|
|
if (lpMapAddress)
|
||
|
|
UnmapViewOfFile(lpMapAddress);
|
||
|
|
if (hMapFile)
|
||
|
|
CloseHandle(hMapFile);
|
||
|
|
CloseHandle(hFile);
|
||
|
|
return packed;
|
||
|
|
}
|