suricata
detect-prefilter.c
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1 /* Copyright (C) 2007-2016 Open Information Security Foundation
2  *
3  * You can copy, redistribute or modify this Program under the terms of
4  * the GNU General Public License version 2 as published by the Free
5  * Software Foundation.
6  *
7  * This program is distributed in the hope that it will be useful,
8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10  * GNU General Public License for more details.
11  *
12  * You should have received a copy of the GNU General Public License
13  * version 2 along with this program; if not, write to the Free Software
14  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
15  * 02110-1301, USA.
16  */
17 
18 /**
19  * \file
20  *
21  * \author Victor Julien <victor@inliniac.net>
22  *
23  * Implements the prefilter keyword
24  */
25 
26 #include "suricata-common.h"
27 #include "decode.h"
28 
29 #include "detect.h"
30 #include "detect-parse.h"
31 #include "detect-content.h"
32 #include "detect-prefilter.h"
33 #include "util-debug.h"
34 
35 static int DetectPrefilterSetup (DetectEngineCtx *, Signature *, const char *);
36 
38 {
39  sigmatch_table[DETECT_PREFILTER].name = "prefilter";
40  sigmatch_table[DETECT_PREFILTER].desc = "force a condition to be used as prefilter";
41  sigmatch_table[DETECT_PREFILTER].url = "/rules/prefilter-keywords.html#prefilter";
42  sigmatch_table[DETECT_PREFILTER].Setup = DetectPrefilterSetup;
44 }
45 
46 /**
47  * \internal
48  * \brief Apply the prefilter keyword to the last match
49  * \param det_ctx detection engine ctx
50  * \param s signature
51  * \param nullstr should be null
52  * \retval 0 ok
53  * \retval -1 failure
54  */
55 static int DetectPrefilterSetup (DetectEngineCtx *de_ctx, Signature *s, const char *nullstr)
56 {
57  SCEnter();
58 
59  if (nullstr != NULL) {
60  SCLogError(SC_ERR_INVALID_VALUE, "prefilter has value");
61  SCReturnInt(-1);
62  }
63 
64  if (s->flags & SIG_FLAG_PREFILTER) {
65  SCLogError(SC_ERR_INVALID_SIGNATURE, "prefilter already set");
66  SCReturnInt(-1);
67  }
68 
69  SigMatch *sm = DetectGetLastSM(s);
70  if (sm == NULL) {
71  SCLogError(SC_ERR_INVALID_SIGNATURE, "prefilter needs preceding match");
72  SCReturnInt(-1);
73  }
74 
75  /* if the sig match is content, prefilter should act like
76  * 'fast_pattern' w/o options. */
77  if (sm->type == DETECT_CONTENT) {
79  if ((cd->flags & DETECT_CONTENT_NEGATED) &&
80  ((cd->flags & DETECT_CONTENT_DISTANCE) ||
81  (cd->flags & DETECT_CONTENT_WITHIN) ||
82  (cd->flags & DETECT_CONTENT_OFFSET) ||
83  (cd->flags & DETECT_CONTENT_DEPTH)))
84  {
85  SCLogError(SC_ERR_INVALID_SIGNATURE, "prefilter; cannot be "
86  "used with negated content, along with relative modifiers");
87  SCReturnInt(-1);
88  }
90  } else {
91  if (sigmatch_table[sm->type].SupportsPrefilter == NULL) {
92  SCLogError(SC_ERR_INVALID_SIGNATURE, "prefilter is not supported for %s",
93  sigmatch_table[sm->type].name);
94  SCReturnInt(-1);
95  }
97 
98  /* make sure setup function runs for this type. */
99  de_ctx->sm_types_prefilter[sm->type] = true;
100  }
101 
102  s->init_data->prefilter_sm = sm;
103 
104  SCReturnInt(0);
105 }
SigTableElmt_::url
const char * url
Definition: detect.h:1238
detect-content.h
SigTableElmt_::desc
const char * desc
Definition: detect.h:1237
SC_ERR_INVALID_VALUE
@ SC_ERR_INVALID_VALUE
Definition: util-error.h:160
SigTableElmt_::name
const char * name
Definition: detect.h:1235
DETECT_CONTENT
@ DETECT_CONTENT
Definition: detect-engine-register.h:62
SignatureInitData_::prefilter_sm
SigMatch * prefilter_sm
Definition: detect.h:513
SigTableElmt_::flags
uint16_t flags
Definition: detect.h:1229
DetectEngineCtx_
main detection engine ctx
Definition: detect.h:784
DETECT_PREFILTER
@ DETECT_PREFILTER
Definition: detect-engine-register.h:313
SC_ERR_INVALID_SIGNATURE
@ SC_ERR_INVALID_SIGNATURE
Definition: util-error.h:69
DetectContentData_
Definition: detect-content.h:86
SigTableElmt_::Setup
int(* Setup)(DetectEngineCtx *, Signature *, const char *)
Definition: detect.h:1220
decode.h
util-debug.h
DETECT_CONTENT_DISTANCE
#define DETECT_CONTENT_DISTANCE
Definition: detect-content.h:30
de_ctx
DetectEngineCtx * de_ctx
Definition: fuzz_siginit.c:17
DETECT_CONTENT_DEPTH
#define DETECT_CONTENT_DEPTH
Definition: detect-content.h:33
SCEnter
#define SCEnter(...)
Definition: util-debug.h:298
detect.h
detect-prefilter.h
DETECT_CONTENT_NEGATED
#define DETECT_CONTENT_NEGATED
Definition: detect-content.h:40
SigMatch_::ctx
SigMatchCtx * ctx
Definition: detect.h:316
Signature_::flags
uint32_t flags
Definition: detect.h:540
DetectContentData_::flags
uint32_t flags
Definition: detect-content.h:97
Signature_::init_data
SignatureInitData * init_data
Definition: detect.h:610
DetectPrefilterRegister
void DetectPrefilterRegister(void)
Definition: detect-prefilter.c:37
DetectGetLastSM
SigMatch * DetectGetLastSM(const Signature *s)
Returns the sm with the largest index (added latest) from this sig.
Definition: detect-parse.c:578
suricata-common.h
SigMatch_::type
uint16_t type
Definition: detect.h:314
sigmatch_table
SigTableElmt sigmatch_table[DETECT_TBLSIZE]
Definition: detect-parse.c:76
SCLogError
#define SCLogError(err_code,...)
Macro used to log ERROR messages.
Definition: util-debug.h:255
DetectEngineCtx_::sm_types_prefilter
bool sm_types_prefilter[DETECT_TBLSIZE]
Definition: detect.h:972
SigTableElmt_::SupportsPrefilter
bool(* SupportsPrefilter)(const Signature *s)
Definition: detect.h:1222
DETECT_CONTENT_OFFSET
#define DETECT_CONTENT_OFFSET
Definition: detect-content.h:32
detect-parse.h
Signature_
Signature container.
Definition: detect.h:539
SigMatch_
a single match condition for a signature
Definition: detect.h:313
SIGMATCH_NOOPT
#define SIGMATCH_NOOPT
Definition: detect.h:1421
DETECT_CONTENT_FAST_PATTERN
#define DETECT_CONTENT_FAST_PATTERN
Definition: detect-content.h:34
SCReturnInt
#define SCReturnInt(x)
Definition: util-debug.h:302
SIG_FLAG_PREFILTER
#define SIG_FLAG_PREFILTER
Definition: detect.h:235
DETECT_CONTENT_WITHIN
#define DETECT_CONTENT_WITHIN
Definition: detect-content.h:31