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https://github.com/Cisco-Talos/clamav.git
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libclamav: added APM parsing for raw DMGs
This commit is contained in:
Kevin Lin
parent
97fbb02b58
commit
87b71f20d7
2 changed files with 433 additions and 0 deletions
316
libclamav/apm.c
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316
libclamav/apm.c
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/*
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* Copyright (C) 2014 Cisco Systems, Inc.
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*
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* Authors: Kevin Lin <kevlin2@cisco.com>
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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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#if HAVE_CONFIG_H
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#include "clamav-config.h"
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#endif
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#include <stdio.h>
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#include <errno.h>
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#if HAVE_STRING_H
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#include <string.h>
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#endif
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#include <ctype.h>
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#include <fcntl.h>
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#include "cltypes.h"
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#include "others.h"
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#include "apm.h"
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#include "prtn_intxn.h"
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#include "scanners.h"
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#define DEBUG_APM_PARSE
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#ifdef DEBUG_APM_PARSE
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# define apm_parsemsg(...) cli_dbgmsg( __VA_ARGS__)
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#else
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# define apm_parsemsg(...) ;
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#endif
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static int apm_prtn_intxn(cli_ctx *ctx, struct apm_partition_info aptable, size_t sectorsize, int old_school);
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int cli_scanapm(cli_ctx *ctx)
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{
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struct apm_driver_desc_map ddm;
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struct apm_partition_info aptable, apentry;
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int ret = 0, old_school = 0;
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size_t sectorsize, maplen, partsize, sectorcheck;;
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off_t pos = 0, partoff = 0;
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unsigned i;
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uint32_t max_prtns = 0;
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if (!ctx || !ctx->fmap) {
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cli_errmsg("cli_scanapm: Invalid context\n");
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return CL_ENULLARG;
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}
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/* read driver description map at sector 0 */
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if (fmap_readn(*ctx->fmap, &ddm, pos, sizeof(ddm)) != sizeof(ddm)) {
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cli_dbgmsg("cli_scanapm: Invalid Apple driver description map\n");
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return CL_EFORMAT;
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}
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/* convert driver description map big-endian to host */
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ddm.signature = be16_to_host(ddm.signature);
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ddm.blockSize = be16_to_host(ddm.blockSize);
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ddm.blockCount = be32_to_host(ddm.blockCount);
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/* check DDM signature */
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if (ddm.signature != DDM_SIGNATURE) {
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cli_dbgmsg("cli_scanapm: Apple driver description map signature mismatch\n");
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return CL_EFORMAT;
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}
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/* sector size is determined by the ddm */
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sectorsize = ddm.blockSize;
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/* size of total file must be described by the ddm */
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maplen = (*ctx->fmap)->real_len;
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if ((ddm.blockSize * ddm.blockCount) != maplen) {
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cli_dbgmsg("cli_scanapm: File described %u size does not match %u actual size\n",
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(ddm.blockSize * ddm.blockCount), maplen);
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return CL_EFORMAT;
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}
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/* check for old-school partition map */
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if (sectorsize == 2048) {
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if (fmap_readn(*ctx->fmap, &aptable, APM_FALLBACK_SECTOR_SIZE, sizeof(aptable)) != sizeof(aptable)) {
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cli_dbgmsg("cli_scanapm: Invalid Apple partition entry\n");
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return CL_EFORMAT;
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}
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aptable.signature = be16_to_host(aptable.signature);
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if (aptable.signature == APM_SIGNATURE) {
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sectorsize = APM_FALLBACK_SECTOR_SIZE;
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old_school = 1;
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}
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}
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/* read partition table at sector 1 (or after the ddm if old-school) */
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pos = APM_PTABLE_BLOCK * sectorsize;
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if (fmap_readn(*ctx->fmap, &aptable, pos, sizeof(aptable)) != sizeof(aptable)) {
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cli_dbgmsg("cli_scanapm: Invalid Apple partition table\n");
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return CL_EFORMAT;
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}
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/* convert partition table big endian to host */
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aptable.signature = be16_to_host(aptable.signature);
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aptable.numPartitions = be32_to_host(aptable.numPartitions);
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aptable.pBlockStart = be32_to_host(aptable.pBlockStart);
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aptable.pBlockCount = be32_to_host(aptable.pBlockCount);
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/* check the partition entry signature */
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if (aptable.signature != APM_SIGNATURE) {
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cli_dbgmsg("cli_scanapm: Apple partition table signature mismatch\n");
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return CL_EFORMAT;
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}
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/* check if partition table partition */
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if (strncmp((char*)aptable.type, "Apple_Partition_Map", 32) &&
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strncmp((char*)aptable.type, "Apple_partition_map", 32) &&
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strncmp((char*)aptable.type, "Apple_patition_map", 32)){
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cli_dbgmsg("cli_scanapm: Initial Apple Partition Map partition is not detected\n");
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return CL_EFORMAT;
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}
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/* check that the partition table fits in the space specified - HEURISTICS */
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if (ctx->options & CL_SCAN_PARTITION_INTXN) {
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ret = apm_prtn_intxn(ctx, aptable, sectorsize, old_school);
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if ((ret != CL_CLEAN) &&
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!((ctx->options & CL_SCAN_ALLMATCHES) && (ret == CL_VIRUS))) {
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return ret;
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}
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}
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/* print debugging info on partition tables */
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cli_dbgmsg("APM Partition Table:\n");
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cli_dbgmsg("Name: %s\n", (char*)aptable.name);
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cli_dbgmsg("Type: %s\n", (char*)aptable.type);
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cli_dbgmsg("Signature: %x\n", aptable.signature);
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cli_dbgmsg("Partition Count: %u\n", aptable.numPartitions);
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cli_dbgmsg("Blocks: [%u, +%u), ([%u, +%u))\n",
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aptable.pBlockStart, aptable.pBlockCount,
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(aptable.pBlockStart * sectorsize),
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(aptable.pBlockCount * sectorsize));
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/* check engine maxpartitions limit */
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if (aptable.numPartitions < ctx->engine->maxpartitions) {
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max_prtns = aptable.numPartitions;
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}
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else {
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max_prtns = ctx->engine->maxpartitions;
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}
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/* partition table is a partition [at index 1], so skip it */
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for (i = 2; i <= max_prtns; ++i) {
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/* read partition table entry */
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pos = i * sectorsize;
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if (fmap_readn(*ctx->fmap, &apentry, pos, sizeof(apentry)) != sizeof(apentry)) {
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cli_dbgmsg("cli_scanapm: Invalid Apple partition entry\n");
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return CL_EFORMAT;
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}
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/* convert partition entry big endian to host */
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apentry.signature = be16_to_host(apentry.signature);
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apentry.reserved = be16_to_host(apentry.reserved);
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apentry.numPartitions = be32_to_host(apentry.numPartitions);
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apentry.pBlockStart = be32_to_host(apentry.pBlockStart);
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apentry.pBlockCount = be32_to_host(apentry.pBlockCount);
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/* check the partition entry signature */
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if (aptable.signature != APM_SIGNATURE) {
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cli_dbgmsg("cli_scanapm: Apple partition entry signature mismatch\n");
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return CL_EFORMAT;
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}
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/* check if a out-of-order partition map */
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if (!strncmp((char*)apentry.type, "Apple_Partition_Map", 32) ||
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!strncmp((char*)apentry.type, "Apple_partition_map", 32) ||
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!strncmp((char*)apentry.type, "Apple_patition_map", 32)) {
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cli_dbgmsg("cli_scanapm: Out of order Apple Partition Map partition\n");
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continue;
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}
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partoff = apentry.pBlockStart * sectorsize;
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partsize = apentry.pBlockCount * sectorsize;
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/* re-calculate if old_school and aligned [512 * 4 => 2048] */
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if (old_school && ((i % 4) == 0)) {
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if (!strncmp((char*)apentry.type, "Apple_Driver", 32) ||
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!strncmp((char*)apentry.type, "Apple_Driver43", 32) ||
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!strncmp((char*)apentry.type, "Apple_Driver43_CD", 32) ||
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!strncmp((char*)apentry.type, "Apple_Driver_ATA", 32) ||
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!strncmp((char*)apentry.type, "Apple_Driver_ATAPI", 32) ||
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!strncmp((char*)apentry.type, "Apple_Patches", 32)) {
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partsize = apentry.pBlockCount * 2048;;
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}
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}
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/* check if invalid partition */
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if ((partoff == 0) || (partoff+partsize > maplen)) {
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cli_dbgmsg("cli_scanapm: Detected invalid Apple partition entry\n");
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continue;
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}
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/* print debugging info on partition */
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cli_dbgmsg("APM Partition Entry %u:\n", i);
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cli_dbgmsg("Name: %s\n", (char*)apentry.name);
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cli_dbgmsg("Type: %s\n", (char*)apentry.type);
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cli_dbgmsg("Signature: %x\n", apentry.signature);
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cli_dbgmsg("Partition Count: %u\n", apentry.numPartitions);
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cli_dbgmsg("Blocks: [%u, +%u), ([%u, +%u))\n",
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apentry.pBlockStart, apentry.pBlockCount, partoff, partsize);
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/* send the partition to cli_map_scan */
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ret = cli_map_scan(*ctx->fmap, partoff, partsize, ctx, CL_TYPE_PART_ANY);
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if ((ret != CL_CLEAN) &&
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!((ctx->options & CL_SCAN_ALLMATCHES) && (ret == CL_VIRUS))) {
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return ret;
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}
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}
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if (i < aptable.numPartitions) {
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cli_dbgmsg("cli_scanapm: max partitions exceeded\n");
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}
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return ret;
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}
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static int apm_prtn_intxn(cli_ctx *ctx, struct apm_partition_info aptable, size_t sectorsize, int old_school)
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{
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prtn_intxn_list_t prtncheck;
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struct apm_partition_info apentry;
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unsigned i, pitxn;
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int ret = 0, tmp = 0;
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off_t pos;
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uint32_t max_prtns = 0;
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prtn_intxn_list_init(&prtncheck);
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/* check engine maxpartitions limit */
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if (aptable.numPartitions < ctx->engine->maxpartitions) {
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max_prtns = aptable.numPartitions;
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}
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else {
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max_prtns = ctx->engine->maxpartitions;
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}
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for (i = 1; i <= max_prtns; ++i) {
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/* read partition table entry */
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pos = i * sectorsize;
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if (fmap_readn(*ctx->fmap, &apentry, pos, sizeof(apentry)) != sizeof(apentry)) {
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cli_dbgmsg("cli_scanapm: Invalid Apple partition entry\n");
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prtn_intxn_list_free(&prtncheck);
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return CL_EFORMAT;
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}
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/* convert necessary info big endian to host */
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apentry.pBlockStart = be32_to_host(apentry.pBlockStart);
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apentry.pBlockCount = be32_to_host(apentry.pBlockCount);
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/* re-calculate if old_school and aligned [512 * 4 => 2048] */
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if (old_school && ((i % 4) == 0)) {
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if (!strncmp((char*)apentry.type, "Apple_Driver", 32) ||
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!strncmp((char*)apentry.type, "Apple_Driver43", 32) ||
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!strncmp((char*)apentry.type, "Apple_Driver43_CD", 32) ||
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!strncmp((char*)apentry.type, "Apple_Driver_ATA", 32) ||
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!strncmp((char*)apentry.type, "Apple_Driver_ATAPI", 32) ||
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!strncmp((char*)apentry.type, "Apple_Patches", 32)) {
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apentry.pBlockCount = apentry.pBlockCount * 4;;
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}
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}
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tmp = prtn_intxn_list_check(&prtncheck, &pitxn, apentry.pBlockStart, apentry.pBlockCount);
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if (tmp != CL_CLEAN) {
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if ((ctx->options & CL_SCAN_ALLMATCHES) && (tmp == CL_VIRUS)) {
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apm_parsemsg("Name: %s\n", (char*)aptable.name);
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apm_parsemsg("Type: %s\n", (char*)aptable.type);
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cli_dbgmsg("cli_scanapm: detected intersection with partitions "
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"[%u, %u]\n", pitxn, i);
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cli_append_virus(ctx, "Heuristic.PartitionIntersection");
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ret = tmp;
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tmp = 0;
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}
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else if (tmp == CL_VIRUS) {
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apm_parsemsg("Name: %s\n", (char*)aptable.name);
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apm_parsemsg("Type: %s\n", (char*)aptable.type);
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cli_dbgmsg("cli_scanapm: detected intersection with partitions "
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"[%u, %u]\n", pitxn, i);
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cli_append_virus(ctx, "Heuristic.PartitionIntersection");
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prtn_intxn_list_free(&prtncheck);
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return CL_VIRUS;
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}
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else {
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prtn_intxn_list_free(&prtncheck);
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return tmp;
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}
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}
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pos += sectorsize;
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}
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prtn_intxn_list_free(&prtncheck);
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return ret;
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}
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