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495 lines
11 KiB
495 lines
11 KiB
/*
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* Copyright (C) 2007-2008 Sourcefire, Inc.
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*
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* Authors: Trog, Török Edvin
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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 <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#include <string.h>
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#include <ctype.h>
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#ifndef _WIN32
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#include <netinet/in.h>
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#endif
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#include <openssl/ssl.h>
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#include <openssl/err.h>
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#include "libclamav/crypto.h"
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#include "clamav.h"
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#include "others.h"
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#include "cltypes.h"
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#include "special.h"
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#include "matcher.h"
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/* NOTE: Photoshop stores data in BIG ENDIAN format, this is the opposite
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to virtually everything else */
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#define special_endian_convert_16(v) be16_to_host(v)
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#define special_endian_convert_32(v) be32_to_host(v)
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int cli_check_mydoom_log(cli_ctx *ctx)
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{
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const uint32_t *record;
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uint32_t check, key;
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fmap_t *map = *ctx->fmap;
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unsigned int blocks = map->len / (8*4);
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cli_dbgmsg("in cli_check_mydoom_log()\n");
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if(blocks<2)
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return CL_CLEAN;
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if(blocks>5)
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blocks = 5;
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record = fmap_need_off_once(map, 0, 8*4*blocks);
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if(!record)
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return CL_CLEAN;
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while(blocks) { /* This wasn't probably intended but that's what the current code does anyway */
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if(record[--blocks] == 0xffffffff)
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return CL_CLEAN;
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}
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key = ~be32_to_host(record[0]);
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check = (be32_to_host(record[1])^key) +
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(be32_to_host(record[2])^key) +
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(be32_to_host(record[3])^key) +
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(be32_to_host(record[4])^key) +
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(be32_to_host(record[5])^key) +
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(be32_to_host(record[6])^key) +
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(be32_to_host(record[7])^key);
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if ((~check) != key)
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return CL_CLEAN;
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key = ~be32_to_host(record[8]);
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check = (be32_to_host(record[9])^key) +
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(be32_to_host(record[10])^key) +
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(be32_to_host(record[11])^key) +
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(be32_to_host(record[12])^key) +
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(be32_to_host(record[13])^key) +
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(be32_to_host(record[14])^key) +
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(be32_to_host(record[15])^key);
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if ((~check) != key)
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return CL_CLEAN;
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cli_append_virus(ctx, "Heuristics.Worm.Mydoom.M.log");
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return CL_VIRUS;
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}
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static int jpeg_check_photoshop_8bim(cli_ctx *ctx, off_t *off)
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{
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const unsigned char *buf;
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uint16_t ntmp;
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uint8_t nlength, id[2];
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uint32_t size;
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off_t offset = *off;
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int retval;
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fmap_t *map = *ctx->fmap;
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if(!(buf = fmap_need_off_once(map, offset, 4 + 2 + 1))) {
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cli_dbgmsg("read bim failed\n");
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return -1;
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}
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if (memcmp(buf, "8BIM", 4) != 0) {
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cli_dbgmsg("missed 8bim\n");
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return -1;
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}
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id[0] = (uint8_t)buf[4];
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id[1] = (uint8_t)buf[5];
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cli_dbgmsg("ID: 0x%.2x%.2x\n", id[0], id[1]);
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nlength = buf[6];
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ntmp = nlength + ((((uint16_t)nlength)+1) & 0x01);
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offset += 4 + 2 + 1 + ntmp;
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if (fmap_readn(map, &size, offset, 4) != 4) {
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return -1;
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}
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size = special_endian_convert_32(size);
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if (size == 0) {
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return -1;
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}
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if ((size & 0x01) == 1) {
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size++;
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}
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*off = offset + 4 + size;
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/* Is it a thumbnail image: 0x0409 or 0x040c */
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if ((id[0] == 0x04) && ((id[1] == 0x09) || (id[1] == 0x0c))) {
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/* Yes */
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cli_dbgmsg("found thumbnail\n");
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}
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else {
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/* No - Seek past record */
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return 0;
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}
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/* Jump past header */
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offset += 4 + 28;
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retval = cli_check_jpeg_exploit(ctx, offset);
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if (retval == 1) {
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cli_dbgmsg("Exploit found in thumbnail\n");
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}
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return retval;
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}
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static int jpeg_check_photoshop(cli_ctx *ctx, off_t offset)
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{
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int retval;
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const unsigned char *buffer;
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off_t old;
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fmap_t *map = *ctx->fmap;
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if(!(buffer = fmap_need_off_once(map, offset, 14))) {
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return 0;
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}
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if (memcmp(buffer, "Photoshop 3.0", 14) != 0) {
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return 0;
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}
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offset += 14;
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cli_dbgmsg("Found Photoshop segment\n");
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do {
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old = offset;
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retval = jpeg_check_photoshop_8bim(ctx, &offset);
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if(offset <= old)
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break;
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} while (retval == 0);
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if (retval == -1) {
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retval = 0;
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}
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return retval;
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}
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int cli_check_jpeg_exploit(cli_ctx *ctx, off_t offset)
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{
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const unsigned char *buffer;
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int retval;
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fmap_t *map = *ctx->fmap;
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cli_dbgmsg("in cli_check_jpeg_exploit()\n");
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if(ctx->recursion > ctx->engine->maxreclevel)
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return CL_EMAXREC;
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if(!(buffer = fmap_need_off_once(map, offset, 2)))
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return 0;
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if ((buffer[0] != 0xff) || (buffer[1] != 0xd8)) {
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return 0;
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}
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offset += 2;
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for (;;) {
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off_t new_off;
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if(!(buffer = fmap_need_off_once(map, offset, 4))) {
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return 0;
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}
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/* Check for multiple 0xFF values, we need to skip them */
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if ((buffer[0] == 0xff) && (buffer[1] == 0xff)) {
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offset++;
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continue;
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}
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offset += 4;
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if ((buffer[0] == 0xff) && (buffer[1] == 0xfe)) {
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if (buffer[2] == 0x00) {
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if ((buffer[3] == 0x00) || (buffer[3] == 0x01)) {
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return 1;
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}
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}
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}
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if (buffer[0] != 0xff) {
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return -1;
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}
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if (buffer[1] == 0xda) {
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/* End of Image marker */
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return 0;
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}
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new_off = ((unsigned int) buffer[2] << 8) + buffer[3];
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if (new_off < 2) {
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return -1;
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}
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new_off -= 2;
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new_off += offset;
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if (buffer[1] == 0xed) {
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/* Possible Photoshop file */
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ctx->recursion++;
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retval=jpeg_check_photoshop(ctx, offset);
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ctx->recursion--;
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if (retval != 0)
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return retval;
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}
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offset = new_off;
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}
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}
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static uint32_t riff_endian_convert_32(uint32_t value, int big_endian)
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{
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if (big_endian)
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return be32_to_host(value);
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else
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return le32_to_host(value);
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}
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static int riff_read_chunk(fmap_t *map, off_t *offset, int big_endian, int rec_level)
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{
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const uint32_t *buf;
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uint32_t chunk_size;
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off_t cur_offset = *offset;
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if (rec_level > 1000) {
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cli_dbgmsg("riff_read_chunk: recursion level exceeded\n");
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return 0;
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}
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if(!(buf = fmap_need_off_once(map, cur_offset, 4*2)))
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return 0;
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cur_offset += 4*2;
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chunk_size = riff_endian_convert_32(buf[1], big_endian);
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if(!memcmp(buf, "anih", 4) && chunk_size != 36)
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return 2;
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if (memcmp(buf, "RIFF", 4) == 0) {
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return 0;
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} else if (memcmp(buf, "RIFX", 4) == 0) {
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return 0;
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}
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if ((memcmp(buf, "LIST", 4) == 0) ||
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(memcmp(buf, "PROP", 4) == 0) ||
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(memcmp(buf, "FORM", 4) == 0) ||
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(memcmp(buf, "CAT ", 4) == 0)) {
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if (!fmap_need_ptr_once(map, buf+2, 4)) {
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cli_dbgmsg("riff_read_chunk: read list type failed\n");
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return 0;
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}
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*offset = cur_offset+4;
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return riff_read_chunk(map, offset, big_endian, ++rec_level);
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}
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*offset = cur_offset + chunk_size + (chunk_size&1);
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if (*offset < cur_offset) {
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return 0;
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}
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/* FIXME: WTF!?
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if (lseek(fd, offset, SEEK_SET) != offset) {
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return 2;
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}
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*/
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return 1;
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}
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int cli_check_riff_exploit(cli_ctx *ctx)
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{
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const uint32_t *buf;
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int big_endian, retval;
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off_t offset;
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fmap_t *map = *ctx->fmap;
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cli_dbgmsg("in cli_check_riff_exploit()\n");
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if(!(buf = fmap_need_off_once(map, 0, 4*3)))
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return 0;
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if (memcmp(buf, "RIFF", 4) == 0) {
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big_endian = FALSE;
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} else if (memcmp(buf, "RIFX", 4) == 0) {
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big_endian = TRUE;
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} else {
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/* Not a RIFF file */
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return 0;
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}
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if (memcmp(&buf[2], "ACON", 4) != 0) {
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/* Only scan MS animated icon files */
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/* There is a *lot* of broken software out there that produces bad RIFF files */
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return 0;
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}
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offset = 4*3;
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do {
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retval = riff_read_chunk(map, &offset, big_endian, 1);
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} while (retval == 1);
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return retval;
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}
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static inline int swizz_j48(const uint16_t n[])
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{
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cli_dbgmsg("swizz_j48: %u, %u, %u\n",n[0],n[1],n[2]);
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/* rules based on J48 tree */
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if (n[0] <= 961 || !n[1])
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return 0;
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if (n[0] <= 1006)
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return (n[2] > 0 && n[2] <= 6);
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else
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return n[1] <= 10 && n[2];
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}
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void cli_detect_swizz_str(const unsigned char *str, uint32_t len, struct swizz_stats *stats, int blob)
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{
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unsigned char stri[4096];
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uint32_t i, j = 0;
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int bad = 0;
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int lastalnum = 0;
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uint8_t ngrams[17576];
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uint16_t all=0;
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uint16_t ngram_cnts[3];
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uint16_t words = 0;
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int ret;
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stats->entries++;
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for(i=0;i<len-1 && j < sizeof(stri)-2;i += 2) {
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unsigned char c = str[i];
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if (str[i+1] || !c) {
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bad++;
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continue;
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}
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if (!isalnum(c)) {
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if (!lastalnum)
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continue;
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lastalnum = 0;
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c = ' ';
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} else {
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lastalnum = 1;
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if (isdigit(c))
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continue;
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}
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stri[j++] = tolower(c);
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}
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stri[j++] = '\0';
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if ((!blob && (bad >= 8)) || j < 4)
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return;
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memset(ngrams, 0, sizeof(ngrams));
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memset(ngram_cnts, 0, sizeof(ngram_cnts));
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for(i=0;i<j-2;i++) {
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if (stri[i] != ' ' && stri[i+1] != ' ' && stri[i+2] != ' ') {
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uint16_t idx = (stri[i] - 'a')*676 + (stri[i+1] - 'a')*26 + (stri[i+2] - 'a');
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if (idx < sizeof(ngrams)) {
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ngrams[idx]++;
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stats->gngrams[idx]++;
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}
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} else if (stri[i] == ' ')
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words++;
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}
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for(i=0;i<sizeof(ngrams);i++) {
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uint8_t v = ngrams[i];
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if (v > 3) v = 3;
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if (v) {
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ngram_cnts[v-1]++;
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all++;
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}
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}
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if (!all)
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return;
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cli_dbgmsg("cli_detect_swizz_str: %u, %u, %u\n",ngram_cnts[0],ngram_cnts[1],ngram_cnts[2]);
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/* normalize */
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for(i=0;i<sizeof(ngram_cnts)/sizeof(ngram_cnts[0]);i++) {
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uint32_t v = ngram_cnts[i];
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ngram_cnts[i] = (v<<10)/all;
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}
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ret = swizz_j48(ngram_cnts) ? CL_VIRUS : CL_CLEAN;
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if (words < 3) ret = CL_CLEAN;
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cli_dbgmsg("cli_detect_swizz_str: %s, %u words\n", ret == CL_VIRUS ? "suspicious" : "ok", words);
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if (ret == CL_VIRUS) {
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stats->suspicious += j;
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cli_dbgmsg("cli_detect_swizz_str: %s\n", stri);
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}
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stats->total += j;
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}
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static inline int swizz_j48_global(const uint32_t gn[])
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{
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if (gn[0] <= 24185) {
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return gn[0] > 22980 && gn[8] > 0 && gn[8] <= 97;
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}
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if (!gn[8]) {
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if (gn[4] <= 311) {
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if (!gn[4]) {
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return gn[1] > 0 &&
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((gn[0] <= 26579 && gn[3] > 0) ||
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(gn[0] > 28672 && gn[0] <= 30506));
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}
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if (gn[5] <= 616) {
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if (gn[6] <= 104) {
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return gn[9] <= 167;
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}
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return gn[6] <= 286;
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}
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}
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return 0;
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}
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return 1;
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}
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int cli_detect_swizz(struct swizz_stats *stats)
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{
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uint32_t gn[10];
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uint32_t all = 0;
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unsigned i;
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int global_swizz = CL_CLEAN;
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cli_dbgmsg("cli_detect_swizz: %lu/%lu, version:%d, manifest: %d \n",
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(unsigned long)stats->suspicious, (unsigned long)stats->total,
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stats->has_version, stats->has_manifest);
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memset(gn, 0, sizeof(gn));
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for(i=0;i<17576;i++) {
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uint8_t v = stats->gngrams[i];
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if (v > 10) v = 10;
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if (v) {
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gn[v-1]++;
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all++;
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}
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}
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if (all) {
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/* normalize */
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cli_dbgmsg("cli_detect_swizz: gn: ");
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for(i=0;i<sizeof(gn)/sizeof(gn[0]);i++) {
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uint32_t v = gn[i];
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gn[i] = (v<<15)/all;
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if (cli_debug_flag)
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fprintf(stderr, "%lu, ", (unsigned long)gn[i]);
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}
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global_swizz = swizz_j48_global(gn) ? CL_VIRUS : CL_CLEAN;
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if (cli_debug_flag) {
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fprintf(stderr, "\n");
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cli_dbgmsg("cli_detect_swizz: global: %s\n", global_swizz ? "suspicious" : "clean");
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}
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}
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if (stats->errors > stats->entries || stats->errors >= SWIZZ_MAXERRORS) {
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cli_dbgmsg("cli_detect_swizz: resources broken, ignoring\n");
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return CL_CLEAN;
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}
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if (stats->total <= 337)
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return CL_CLEAN;
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if (stats->suspicious<<10 > 40*stats->total)
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return CL_VIRUS;
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if (!stats->suspicious)
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return CL_CLEAN;
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return global_swizz;
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}
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