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/* Copyright (C) 2007-2019 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 depth 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.h"
#include "detect-byte-extract.h"
#include "detect-depth.h"
#include "flow-var.h"
#include "app-layer.h"
#include "util-byte.h"
#include "util-debug.h"
static int DetectDepthSetup (DetectEngineCtx *, Signature *, const char *);
static int DetectStartsWithSetup (DetectEngineCtx *, Signature *, const char *);
void DetectDepthRegister (void)
{
sigmatch_table[DETECT_DEPTH].name = "depth";
sigmatch_table[DETECT_DEPTH].desc = "designate how many bytes from the beginning of the payload will be checked";
sigmatch_table[DETECT_DEPTH].url = "/rules/payload-keywords.html#depth";
sigmatch_table[DETECT_DEPTH].Match = NULL;
sigmatch_table[DETECT_DEPTH].Setup = DetectDepthSetup;
sigmatch_table[DETECT_DEPTH].Free = NULL;
sigmatch_table[DETECT_STARTS_WITH].name = "startswith";
sigmatch_table[DETECT_STARTS_WITH].desc = "pattern must be at the start of a buffer (same as 'depth:<pattern len>')";
sigmatch_table[DETECT_STARTS_WITH].url = "/rules/payload-keywords.html#startswith";
sigmatch_table[DETECT_STARTS_WITH].Setup = DetectStartsWithSetup;
sigmatch_table[DETECT_STARTS_WITH].flags |= SIGMATCH_NOOPT;
}
static int DetectDepthSetup (DetectEngineCtx *de_ctx, Signature *s, const char *depthstr)
{
const char *str = depthstr;
SigMatch *pm = NULL;
int ret = -1;
/* retrieve the sm to apply the depth against */
pm = DetectGetLastSMFromLists(s, DETECT_CONTENT, -1);
if (pm == NULL) {
SCLogError("depth 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, "
"http_host, http_raw_host or "
"file_data/dce_stub_data sticky buffer options.");
goto end;
}
/* verify other conditions. */
DetectContentData *cd = (DetectContentData *)pm->ctx;
if (cd->flags & DETECT_CONTENT_DEPTH) {
SCLogError("can't use multiple depths for the same content.");
goto end;
}
if ((cd->flags & DETECT_CONTENT_WITHIN) || (cd->flags & DETECT_CONTENT_DISTANCE)) {
SCLogError("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("can't have a relative "
"negated keyword set along with 'fast_pattern'.");
goto end;
}
if (cd->flags & DETECT_CONTENT_FAST_PATTERN_ONLY) {
SCLogError("can't have a relative "
"keyword set along with 'fast_pattern:only;'.");
goto end;
}
if (str[0] != '-' && isalpha((unsigned char)str[0])) {
DetectByteIndexType index;
if (!DetectByteRetrieveSMVar(str, s, &index)) {
SCLogError("unknown byte_ keyword var "
"seen in depth - %s.",
str);
goto end;
}
cd->depth = index;
cd->flags |= DETECT_CONTENT_DEPTH_VAR;
} else {
if (StringParseUint16(&cd->depth, 0, 0, str) < 0)
{
SCLogError("invalid value for depth: %s.", str);
goto end;
}
if (cd->depth < cd->content_len) {
SCLogError("depth:%u smaller than "
"content of len %u.",
cd->depth, cd->content_len);
return -1;
}
/* Now update the real limit, as depth is relative to the offset */
cd->depth += cd->offset;
}
cd->flags |= DETECT_CONTENT_DEPTH;
ret = 0;
end:
return ret;
}
static int DetectStartsWithSetup (DetectEngineCtx *de_ctx, Signature *s, const char *unused)
{
SigMatch *pm = NULL;
int ret = -1;
/* retrieve the sm to apply the depth against */
pm = DetectGetLastSMFromLists(s, DETECT_CONTENT, -1);
if (pm == NULL) {
SCLogError("startswith needs a "
"preceding content option.");
goto end;
}
/* verify other conditions. */
DetectContentData *cd = (DetectContentData *)pm->ctx;
if (cd->flags & DETECT_CONTENT_DEPTH) {
SCLogError("can't use multiple "
"depth/startswith settings for the same content.");
goto end;
}
if ((cd->flags & DETECT_CONTENT_WITHIN) || (cd->flags & DETECT_CONTENT_DISTANCE)) {
SCLogError("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("can't have a relative "
"negated keyword set along with a 'fast_pattern'.");
goto end;
}
if (cd->flags & DETECT_CONTENT_FAST_PATTERN_ONLY) {
SCLogError("can't have a relative "
"keyword set along with 'fast_pattern:only;'.");
goto end;
}
if (cd->flags & DETECT_CONTENT_OFFSET) {
SCLogError("can't mix offset "
"with startswith.");
goto end;
}
cd->depth = cd->content_len;
cd->flags |= DETECT_CONTENT_DEPTH;
cd->flags |= DETECT_CONTENT_STARTS_WITH;
ret = 0;
end:
return ret;
}
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