/*
* Copyright (C) 2007-2008 Sourcefire, Inc.
*
* Authors: Tomasz Kojm
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*/
#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include <string.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include "clamav.h"
#include "others.h"
#include "matcher-ac.h"
#include "matcher-bm.h"
#include "md5.h"
#include "filetypes.h"
#include "matcher.h"
#include "pe.h"
#include "elf.h"
#include "execs.h"
#include "special.h"
#include "str.h"
#include "cltypes.h"
int cli_scanbuff(const unsigned char *buffer, uint32_t length, cli_ctx *ctx, cli_file_t ftype)
{
int ret = CL_CLEAN;
unsigned int i;
struct cli_ac_data mdata;
struct cli_matcher *groot, *troot = NULL;
const char **virname=ctx->virname;
const struct cl_engine *engine=ctx->engine;
if(!engine) {
cli_errmsg("cli_scanbuff: engine == NULL\n");
return CL_ENULLARG;
}
groot = engine->root[0]; /* generic signatures */
if(ftype) {
for(i = 1; i < CLI_MTARGETS; i++) {
if(cli_mtargets[i].target == ftype) {
troot = engine->root[i];
break;
}
}
}
if(troot) {
if((ret = cli_ac_initdata(&mdata, troot->ac_partsigs, troot->ac_lsigs, AC_DEFAULT_TRACKLEN)))
return ret;
if(troot->ac_only || (ret = cli_bm_scanbuff(buffer, length, virname, troot, 0, ftype, -1)) != CL_VIRUS)
ret = cli_ac_scanbuff(buffer, length, virname, NULL, NULL, troot, &mdata, 0, ftype, -1, NULL, AC_SCAN_VIR, NULL);
cli_ac_freedata(&mdata);
if(ret == CL_VIRUS)
return ret;
}
if((ret = cli_ac_initdata(&mdata, groot->ac_partsigs, groot->ac_lsigs, AC_DEFAULT_TRACKLEN)))
return ret;
if(groot->ac_only || (ret = cli_bm_scanbuff(buffer, length, virname, groot, 0, ftype, -1)) != CL_VIRUS)
ret = cli_ac_scanbuff(buffer, length, virname, NULL, NULL, groot, &mdata, 0, ftype, -1, NULL, AC_SCAN_VIR, NULL);
cli_ac_freedata(&mdata);
return ret;
}
off_t cli_caloff(const char *offstr, struct cli_target_info *info, int fd, cli_file_t ftype, int *ret, unsigned int *maxshift)
{
int (*einfo)(int, struct cli_exe_info *) = NULL;
unsigned int n, val;
const char *pt;
off_t pos, offset;
*ret = 0;
if(!strncmp(offstr, "EP", 2) || offstr[0] == 'S') {
if(info->status == -1) {
*ret = -1;
return 0;
} else if(!info->status) {
if(ftype == CL_TYPE_MSEXE)
einfo = cli_peheader;
else if(ftype == CL_TYPE_ELF)
einfo = cli_elfheader;
if(einfo) {
if((pos = lseek(fd, 0, SEEK_CUR)) == -1) {
cli_dbgmsg("Invalid descriptor\n");
info->status = *ret = -1;
return 0;
}
lseek(fd, 0, SEEK_SET);
if(einfo(fd, &info->exeinfo)) {
lseek(fd, pos, SEEK_SET);
info->status = *ret = -1;
return 0;
}
lseek(fd, pos, SEEK_SET);
info->status = 1;
}
}
}
if((pt = strchr(offstr, ',')))
*maxshift = atoi(++pt);
if(isdigit(offstr[0])) {
return atoi(offstr);
} else if(info->status == 1 && (!strncmp(offstr, "EP+", 3) || !strncmp(offstr, "EP-", 3))) {
if(offstr[2] == '+')
return info->exeinfo.ep + atoi(offstr + 3);
else
return info->exeinfo.ep - atoi(offstr + 3);
} else if(info->status == 1 && offstr[0] == 'S') {
if(!strncmp(offstr, "SL", 2) && info->exeinfo.section[info->exeinfo.nsections - 1].rsz) {
if(sscanf(offstr, "SL+%u", &val) != 1) {
*ret = -1;
return 0;
}
offset = val + info->exeinfo.section[info->exeinfo.nsections - 1].raw;
} else {
if(sscanf(offstr, "S%u+%u", &n, &val) != 2) {
*ret = -1;
return 0;
}
if(n >= info->exeinfo.nsections || !info->exeinfo.section[n].rsz) {
*ret = -1;
return 0;
}
offset = val + info->exeinfo.section[n].raw;
}
return offset;
} else if(!strncmp(offstr, "EOF-", 4)) {
struct stat sb;
if(!info->fsize) {
if(fstat(fd, &sb) == -1) {
info->status = *ret = -1;
return 0;
}
info->fsize = sb.st_size;
}
return info->fsize - atoi(offstr + 4);
}
*ret = -1;
return 0;
}
static int cli_checkfp(int fd, const struct cl_engine *engine)
{
unsigned char *digest;
const char *virname;
if(engine->md5_fp) {
if(!(digest = cli_md5digest(fd))) {
cli_errmsg("cli_checkfp(): Can't generate MD5 checksum\n");
return 0;
}
if(cli_bm_scanbuff(digest, 16, &virname, engine->md5_fp, 0, 0, -1) == CL_VIRUS) {
cli_dbgmsg("Eliminated false positive match (fp sig: %s)\n", virname);
free(digest);
return 1;
}
free(digest);
}
return 0;
}
int cli_validatesig(cli_file_t ftype, const char *offstr, off_t fileoff, struct cli_target_info *info, int desc, const char *virname)
{
off_t offset;
int ret;
unsigned int maxshift = 0;
if(offstr && desc != -1) {
offset = cli_caloff(offstr, info, desc, ftype, &ret, &maxshift);
if(ret == -1) {
cli_dbgmsg("cli_validatesig: Can't calculate offset for signature %s\n", virname);
return 0;
}
if(maxshift) {
if((fileoff < offset) || (fileoff > offset + (off_t) maxshift)) {
/* cli_dbgmsg("Signature offset: %lu, expected: [%lu..%lu] (%s)\n", (unsigned long int) fileoff, (unsigned long int) offset, (unsigned long int) (offset + maxshift), virname); */
return 0;
}
} else if(fileoff != offset) {
/* cli_dbgmsg("Signature offset: %lu, expected: %lu (%s)\n", (unsigned long int) fileoff, (unsigned long int) offset, virname); */
return 0;
}
}
return 1;
}
int cli_scandesc(int desc, cli_ctx *ctx, cli_file_t ftype, uint8_t ftonly, struct cli_matched_type **ftoffset, unsigned int acmode)
{
unsigned char *buffer, *buff, *endbl, *upt;
int ret = CL_CLEAN, type = CL_CLEAN, bytes;
unsigned int i, evalcnt;
uint32_t buffersize, length, maxpatlen, shift = 0, offset = 0;
uint64_t evalids;
struct cli_ac_data gdata, tdata;
cli_md5_ctx md5ctx;
unsigned char digest[16];
struct cli_matcher *groot = NULL, *troot = NULL;
if(!ctx->engine) {
cli_errmsg("cli_scandesc: engine == NULL\n");
return CL_ENULLARG;
}
if(!ftonly)
groot = ctx->engine->root[0]; /* generic signatures */
if(ftype) {
for(i = 1; i < CLI_MTARGETS; i++) {
if(cli_mtargets[i].target == ftype) {
troot = ctx->engine->root[i];
break;
}
}
}
if(ftonly) {
if(!troot)
return CL_CLEAN;
maxpatlen = troot->maxpatlen;
} else {
if(troot)
maxpatlen = MAX(troot->maxpatlen, groot->maxpatlen);
else
maxpatlen = groot->maxpatlen;
}
/* prepare the buffer */
buffersize = maxpatlen + SCANBUFF;
if(!(buffer = (unsigned char *) cli_calloc(buffersize, sizeof(unsigned char)))) {
cli_dbgmsg("cli_scandesc(): unable to cli_calloc(%u)\n", buffersize);
return CL_EMEM;
}
if(!ftonly && (ret = cli_ac_initdata(&gdata, groot->ac_partsigs, groot->ac_lsigs, AC_DEFAULT_TRACKLEN)))
return ret;
if(troot) {
if((ret = cli_ac_initdata(&tdata, troot->ac_partsigs, troot->ac_lsigs, AC_DEFAULT_TRACKLEN)))
return ret;
}
if(!ftonly && ctx->engine->md5_hdb)
cli_md5_init(&md5ctx);
buff = buffer;
buff += maxpatlen; /* pointer to read data block */
endbl = buff + SCANBUFF - maxpatlen; /* pointer to the last block
* length of maxpatlen
*/
upt = buff;
while((bytes = cli_readn(desc, buff + shift, SCANBUFF - shift)) > 0) {
if(ctx->scanned)
*ctx->scanned += bytes / CL_COUNT_PRECISION;
length = shift + bytes;
if(upt == buffer)
length += maxpatlen;
if(troot) {
if(troot->ac_only || (ret = cli_bm_scanbuff(upt, length, ctx->virname, troot, offset, ftype, desc)) != CL_VIRUS)
ret = cli_ac_scanbuff(upt, length, ctx->virname, NULL, NULL, troot, &tdata, offset, ftype, desc, ftoffset, acmode, NULL);
if(ret == CL_VIRUS) {
free(buffer);
if(!ftonly)
cli_ac_freedata(&gdata);
cli_ac_freedata(&tdata);
lseek(desc, 0, SEEK_SET);
if(cli_checkfp(desc, ctx->engine))
return CL_CLEAN;
else
return CL_VIRUS;
}
}
if(!ftonly) {
if(groot->ac_only || (ret = cli_bm_scanbuff(upt, length, ctx->virname, groot, offset, ftype, desc)) != CL_VIRUS)
ret = cli_ac_scanbuff(upt, length, ctx->virname, NULL, NULL, groot, &gdata, offset, ftype, desc, ftoffset, acmode, NULL);
if(ret == CL_VIRUS) {
free(buffer);
cli_ac_freedata(&gdata);
if(troot)
cli_ac_freedata(&tdata);
lseek(desc, 0, SEEK_SET);
if(cli_checkfp(desc, ctx->engine))
return CL_CLEAN;
else
return CL_VIRUS;
} else if((acmode & AC_SCAN_FT) && ret >= CL_TYPENO) {
if(ret > type)
type = ret;
}
if(ctx->engine->md5_hdb)
cli_md5_update(&md5ctx, buff + shift, bytes);
}
if(bytes + shift == SCANBUFF) {
memmove(buffer, endbl, maxpatlen);
offset += SCANBUFF;
if(upt == buff) {
upt = buffer;
offset -= maxpatlen;
}
shift = 0;
} else {
shift += bytes;
}
}
free(buffer);
if(troot) {
for(i = 0; i < troot->ac_lsigs; i++) {
evalcnt = 0;
evalids = 0;
if(cli_ac_chklsig(troot->ac_lsigtable[i]->logic, troot->ac_lsigtable[i]->logic + strlen(troot->ac_lsigtable[i]->logic), tdata.lsigcnt[i], &evalcnt, &evalids, 0) == 1) {
if(ctx->virname)
*ctx->virname = troot->ac_lsigtable[i]->virname;
ret = CL_VIRUS;
break;
}
}
cli_ac_freedata(&tdata);
}
if(groot) {
if(ret != CL_VIRUS) for(i = 0; i < groot->ac_lsigs; i++) {
evalcnt = 0;
evalids = 0;
if(cli_ac_chklsig(groot->ac_lsigtable[i]->logic, groot->ac_lsigtable[i]->logic + strlen(groot->ac_lsigtable[i]->logic), gdata.lsigcnt[i], &evalcnt, &evalids, 0) == 1) {
if(ctx->virname)
*ctx->virname = groot->ac_lsigtable[i]->virname;
ret = CL_VIRUS;
break;
}
}
cli_ac_freedata(&gdata);
}
if(ret == CL_VIRUS) {
lseek(desc, 0, SEEK_SET);
if(cli_checkfp(desc, ctx->engine))
return CL_CLEAN;
else
return CL_VIRUS;
}
if(!ftonly && ctx->engine->md5_hdb) {
cli_md5_final(digest, &md5ctx);
if(cli_bm_scanbuff(digest, 16, ctx->virname, ctx->engine->md5_hdb, 0, 0, -1) == CL_VIRUS && (cli_bm_scanbuff(digest, 16, NULL, ctx->engine->md5_fp, 0, 0, -1) != CL_VIRUS))
return CL_VIRUS;
}
return (acmode & AC_SCAN_FT) ? type : CL_CLEAN;
}