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/* Copyright (C) 2007-2010 Open Information Security Foundation
*
* You can copy, redistribute or modify this Program 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
* version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
/**
* \file
*
* \author Victor Julien <victor@inliniac.net>
* \author Anoop Saldanha <anoopsaldanha@gmail.com>
*
* Implements the offset keyword.
*/
#include "suricata-common.h"
#include "decode.h"
#include "detect.h"
#include "detect-parse.h"
#include "detect-content.h"
#include "detect-uricontent.h"
#include "detect-byte-extract.h"
#include "app-layer.h"
#include "flow-var.h"
#include "util-debug.h"
static int DetectOffsetSetup(DetectEngineCtx *, Signature *, char *);
void DetectOffsetRegister (void)
{
sigmatch_table[DETECT_OFFSET].name = "offset";
sigmatch_table[DETECT_OFFSET].desc = "designate from which byte in the payload will be checked to find a match";
sigmatch_table[DETECT_OFFSET].url = "https://redmine.openinfosecfoundation.org/projects/suricata/wiki/Payload_keywords#Offset";
sigmatch_table[DETECT_OFFSET].Match = NULL;
sigmatch_table[DETECT_OFFSET].Setup = DetectOffsetSetup;
sigmatch_table[DETECT_OFFSET].Free = NULL;
sigmatch_table[DETECT_OFFSET].RegisterTests = NULL;
sigmatch_table[DETECT_OFFSET].flags |= SIGMATCH_PAYLOAD;
}
int DetectOffsetSetup (DetectEngineCtx *de_ctx, Signature *s, char *offsetstr)
{
char *str = offsetstr;
char dubbed = 0;
SigMatch *pm = NULL;
int ret = -1;
/* strip "'s */
if (offsetstr[0] == '\"' && offsetstr[strlen(offsetstr)-1] == '\"') {
str = SCStrdup(offsetstr+1);
if (unlikely(str == NULL))
goto end;
str[strlen(offsetstr) - 2] = '\0';
dubbed = 1;
}
/* retrive the sm to apply the depth against */
if (s->list != DETECT_SM_LIST_NOTSET) {
pm = SigMatchGetLastSMFromLists(s, 2, DETECT_CONTENT, s->sm_lists_tail[s->list]);
} else {
pm = SigMatchGetLastSMFromLists(s, 28,
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_PMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_UMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HRUDMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HCBDMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_FILEDATA],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HHDMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HRHDMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HMDMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HCDMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HSCDMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HSMDMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HUADMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HHHDMATCH],
DETECT_CONTENT, s->sm_lists_tail[DETECT_SM_LIST_HRHHDMATCH]);
}
if (pm == NULL) {
SCLogError(SC_ERR_OFFSET_MISSING_CONTENT, "offset needs "
"preceding content, uricontent option, http_client_body, "
"http_server_body, http_header option, http_raw_header option, "
"http_method option, http_cookie, http_raw_uri, "
"http_stat_msg, http_stat_code, http_user_agent or "
"file_data/dce_stub_data sticky buffer options");
goto end;
}
/* verify other conditions */
DetectContentData *cd = (DetectContentData *)pm->ctx;
if (cd->flags & DETECT_CONTENT_OFFSET) {
SCLogError(SC_ERR_INVALID_SIGNATURE, "can't use multiple offsets for the same content. ");
goto end;
}
if ((cd->flags & DETECT_CONTENT_WITHIN) || (cd->flags & DETECT_CONTENT_DISTANCE)) {
SCLogError(SC_ERR_INVALID_SIGNATURE, "can't use a relative "
"keyword like within/distance with a absolute "
"relative keyword like depth/offset for the same "
"content." );
goto end;
}
if (cd->flags & DETECT_CONTENT_NEGATED && cd->flags & DETECT_CONTENT_FAST_PATTERN) {
SCLogError(SC_ERR_INVALID_SIGNATURE, "can't have a relative "
"negated keyword set along with a fast_pattern");
goto end;
}
if (cd->flags & DETECT_CONTENT_FAST_PATTERN_ONLY) {
SCLogError(SC_ERR_INVALID_SIGNATURE, "can't have a relative "
"keyword set along with a fast_pattern:only;");
goto end;
}
if (str[0] != '-' && isalpha((unsigned char)str[0])) {
SigMatch *bed_sm =
DetectByteExtractRetrieveSMVar(str, s);
if (bed_sm == NULL) {
SCLogError(SC_ERR_INVALID_SIGNATURE, "unknown byte_extract var "
"seen in offset - %s\n", str);
goto end;
}
cd->offset = ((DetectByteExtractData *)bed_sm->ctx)->local_id;
cd->flags |= DETECT_CONTENT_OFFSET_BE;
} else {
cd->offset = (uint32_t)atoi(str);
if (cd->depth != 0) {
if (cd->depth < cd->content_len) {
SCLogDebug("depth increased to %"PRIu32" to match pattern len",
cd->content_len);
cd->depth = cd->content_len;
}
/* Updating the depth as is relative to the offset */
cd->depth += cd->offset;
}
}
cd->flags |= DETECT_CONTENT_OFFSET;
ret = 0;
end:
if (dubbed)
SCFree(str);
return ret;
}
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