suricata
detect-tcp-ack.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 Brian Rectanus <brectanu@gmail.com>
22  * \author Victor Julien <victor@inliniac.net>
23  *
24  * Implements the "ack" keyword.
25  */
26 
27 #include "suricata-common.h"
28 #include "decode.h"
29 #include "detect.h"
30 
31 #include "detect-parse.h"
32 #include "detect-engine.h"
33 #include "detect-engine-mpm.h"
36 #include "detect-engine-build.h"
37 
38 #include "detect-tcp-ack.h"
39 
40 #include "util-byte.h"
41 #include "util-unittest.h"
42 #include "util-unittest-helper.h"
43 #include "util-debug.h"
44 
45 /* prototypes */
46 static int DetectAckSetup(DetectEngineCtx *, Signature *, const char *);
47 static int DetectAckMatch(DetectEngineThreadCtx *,
48  Packet *, const Signature *, const SigMatchCtx *);
49 #ifdef UNITTESTS
50 static void DetectAckRegisterTests(void);
51 #endif
52 static void DetectAckFree(DetectEngineCtx *, void *);
53 static int PrefilterSetupTcpAck(DetectEngineCtx *de_ctx, SigGroupHead *sgh);
54 static bool PrefilterTcpAckIsPrefilterable(const Signature *s);
55 
57 {
58  sigmatch_table[DETECT_ACK].name = "tcp.ack";
60  sigmatch_table[DETECT_ACK].desc = "check for a specific TCP acknowledgement number";
61  sigmatch_table[DETECT_ACK].url = "/rules/header-keywords.html#ack";
62  sigmatch_table[DETECT_ACK].Match = DetectAckMatch;
63  sigmatch_table[DETECT_ACK].Setup = DetectAckSetup;
64  sigmatch_table[DETECT_ACK].Free = DetectAckFree;
65 
66  sigmatch_table[DETECT_ACK].SupportsPrefilter = PrefilterTcpAckIsPrefilterable;
67  sigmatch_table[DETECT_ACK].SetupPrefilter = PrefilterSetupTcpAck;
68 #ifdef UNITTESTS
69  sigmatch_table[DETECT_ACK].RegisterTests = DetectAckRegisterTests;
70 #endif
71 }
72 
73 /**
74  * \internal
75  * \brief This function is used to match packets with a given Ack number
76  *
77  * \param t pointer to thread vars
78  * \param det_ctx pointer to the pattern matcher thread
79  * \param p pointer to the current packet
80  * \param m pointer to the sigmatch that we will cast into DetectAckData
81  *
82  * \retval 0 no match
83  * \retval 1 match
84  */
85 static int DetectAckMatch(DetectEngineThreadCtx *det_ctx,
86  Packet *p, const Signature *s, const SigMatchCtx *ctx)
87 {
88  const DetectAckData *data = (const DetectAckData *)ctx;
89 
90  /* This is only needed on TCP packets */
91  if (!(PKT_IS_TCP(p)) || PKT_IS_PSEUDOPKT(p)) {
92  return 0;
93  }
94 
95  return (data->ack == TCP_GET_ACK(p)) ? 1 : 0;
96 }
97 
98 /**
99  * \internal
100  * \brief this function is used to add the ack option into the signature
101  *
102  * \param de_ctx pointer to the Detection Engine Context
103  * \param s pointer to the Current Signature
104  * \param m pointer to the Current SigMatch
105  * \param optstr pointer to the user provided options
106  *
107  * \retval 0 on Success
108  * \retval -1 on Failure
109  */
110 static int DetectAckSetup(DetectEngineCtx *de_ctx, Signature *s, const char *optstr)
111 {
112  DetectAckData *data = NULL;
113 
114  data = SCMalloc(sizeof(DetectAckData));
115  if (unlikely(data == NULL))
116  goto error;
117 
118  if (StringParseUint32(&data->ack, 10, 0, optstr) < 0) {
119  goto error;
120  }
121 
123  NULL) {
124  goto error;
125  }
127 
128  return 0;
129 
130 error:
131  if (data)
132  SCFree(data);
133  return -1;
134 
135 }
136 
137 /**
138  * \internal
139  * \brief this function will free memory associated with ack option
140  *
141  * \param data pointer to ack configuration data
142  */
143 static void DetectAckFree(DetectEngineCtx *de_ctx, void *ptr)
144 {
145  DetectAckData *data = (DetectAckData *)ptr;
146  SCFree(data);
147 }
148 
149 /* prefilter code */
150 
151 static void
152 PrefilterPacketAckMatch(DetectEngineThreadCtx *det_ctx, Packet *p, const void *pectx)
153 {
154  const PrefilterPacketHeaderCtx *ctx = pectx;
155 
156  if (!PrefilterPacketHeaderExtraMatch(ctx, p))
157  return;
158 
159  if ((p->proto) == IPPROTO_TCP && !(PKT_IS_PSEUDOPKT(p)) &&
160  (p->tcph != NULL) && (TCP_GET_ACK(p) == ctx->v1.u32[0]))
161  {
162  SCLogDebug("packet matches TCP ack %u", ctx->v1.u32[0]);
163  PrefilterAddSids(&det_ctx->pmq, ctx->sigs_array, ctx->sigs_cnt);
164  }
165 }
166 
167 static void
168 PrefilterPacketAckSet(PrefilterPacketHeaderValue *v, void *smctx)
169 {
170  const DetectAckData *a = smctx;
171  v->u32[0] = a->ack;
172 }
173 
174 static bool
175 PrefilterPacketAckCompare(PrefilterPacketHeaderValue v, void *smctx)
176 {
177  const DetectAckData *a = smctx;
178  if (v.u32[0] == a->ack)
179  return true;
180  return false;
181 }
182 
183 static int PrefilterSetupTcpAck(DetectEngineCtx *de_ctx, SigGroupHead *sgh)
184 {
186  PrefilterPacketAckSet,
187  PrefilterPacketAckCompare,
188  PrefilterPacketAckMatch);
189 }
190 
191 static bool PrefilterTcpAckIsPrefilterable(const Signature *s)
192 {
193  const SigMatch *sm;
194  for (sm = s->init_data->smlists[DETECT_SM_LIST_MATCH] ; sm != NULL; sm = sm->next) {
195  switch (sm->type) {
196  case DETECT_ACK:
197  return true;
198  }
199  }
200  return false;
201 }
202 
203 #ifdef UNITTESTS
204 #include "detect-engine-alert.h"
205 /**
206  * \internal
207  * \brief This test tests sameip success and failure.
208  */
209 static int DetectAckSigTest01(void)
210 {
211  Packet *p1 = NULL;
212  Packet *p2 = NULL;
213  Packet *p3 = NULL;
214  ThreadVars th_v;
215  DetectEngineThreadCtx *det_ctx;
216  int result = 0;
217 
218  memset(&th_v, 0, sizeof(th_v));
219 
220  /* TCP w/ack=42 */
221  p1 = UTHBuildPacket(NULL, 0, IPPROTO_TCP);
222  p1->tcph->th_ack = htonl(42);
223 
224  /* TCP w/ack=100 */
225  p2 = UTHBuildPacket(NULL, 0, IPPROTO_TCP);
226  p2->tcph->th_ack = htonl(100);
227 
228  /* ICMP */
229  p3 = UTHBuildPacket(NULL, 0, IPPROTO_ICMP);
230 
232  if (de_ctx == NULL) {
233  goto end;
234  }
235 
236  de_ctx->flags |= DE_QUIET;
237 
238  /* These three are crammed in here as there is no Parse */
239  if (SigInit(de_ctx,
240  "alert tcp any any -> any any "
241  "(msg:\"Testing ack\";ack:foo;sid:1;)") != NULL)
242  {
243  printf("invalid ack accepted: ");
244  goto cleanup_engine;
245  }
246  if (SigInit(de_ctx,
247  "alert tcp any any -> any any "
248  "(msg:\"Testing ack\";ack:9999999999;sid:1;)") != NULL)
249  {
250  printf("overflowing ack accepted: ");
251  goto cleanup_engine;
252  }
253  if (SigInit(de_ctx,
254  "alert tcp any any -> any any "
255  "(msg:\"Testing ack\";ack:-100;sid:1;)") != NULL)
256  {
257  printf("negative ack accepted: ");
258  goto cleanup_engine;
259  }
260 
262  "alert tcp any any -> any any "
263  "(msg:\"Testing ack\";ack:41;sid:1;)");
264  if (de_ctx->sig_list == NULL) {
265  goto cleanup_engine;
266  }
267 
269  "alert tcp any any -> any any "
270  "(msg:\"Testing ack\";ack:42;sid:2;)");
271  if (de_ctx->sig_list->next == NULL) {
272  goto cleanup_engine;
273  }
274 
276  DetectEngineThreadCtxInit(&th_v, (void *)de_ctx, (void *)&det_ctx);
277 
278  SigMatchSignatures(&th_v, de_ctx, det_ctx, p1);
279  if (PacketAlertCheck(p1, 1) != 0) {
280  printf("sid 1 alerted, but should not have: ");
281  goto cleanup;
282  }
283  if (PacketAlertCheck(p1, 2) == 0) {
284  printf("sid 2 did not alert, but should have: ");
285  goto cleanup;
286  }
287 
288  SigMatchSignatures(&th_v, de_ctx, det_ctx, p2);
289  if (PacketAlertCheck(p2, 1) != 0) {
290  printf("sid 1 alerted, but should not have: ");
291  goto cleanup;
292  }
293  if (PacketAlertCheck(p2, 2) != 0) {
294  printf("sid 2 alerted, but should not have: ");
295  goto cleanup;
296  }
297 
298  SigMatchSignatures(&th_v, de_ctx, det_ctx, p3);
299  if (PacketAlertCheck(p3, 1) != 0) {
300  printf("sid 1 alerted, but should not have: ");
301  goto cleanup;
302  }
303  if (PacketAlertCheck(p3, 2) != 0) {
304  printf("sid 2 alerted, but should not have: ");
305  goto cleanup;
306  }
307 
308  result = 1;
309 
310 cleanup:
313 
314  DetectEngineThreadCtxDeinit(&th_v, (void *)det_ctx);
315 
316 cleanup_engine:
318 
319 end:
320  return result;
321 }
322 
323 /**
324  * \internal
325  * \brief This function registers unit tests for DetectAck
326  */
327 static void DetectAckRegisterTests(void)
328 {
329  UtRegisterTest("DetectAckSigTest01", DetectAckSigTest01);
330 }
331 #endif /* UNITTESTS */
util-byte.h
SigTableElmt_::url
const char * url
Definition: detect.h:1296
Packet_::proto
uint8_t proto
Definition: decode.h:459
detect-engine.h
SignatureInitData_::smlists
struct SigMatch_ * smlists[DETECT_SM_LIST_MAX]
Definition: detect.h:578
SigTableElmt_::desc
const char * desc
Definition: detect.h:1295
SigTableElmt_::Free
void(* Free)(DetectEngineCtx *, void *)
Definition: detect.h:1283
SigTableElmt_::name
const char * name
Definition: detect.h:1293
PKT_IS_PSEUDOPKT
#define PKT_IS_PSEUDOPKT(p)
return 1 if the packet is a pseudo packet
Definition: decode.h:1074
SigGroupHead_
Container for matching data for a signature group.
Definition: detect.h:1445
unlikely
#define unlikely(expr)
Definition: util-optimize.h:35
UtRegisterTest
void UtRegisterTest(const char *name, int(*TestFn)(void))
Register unit test.
Definition: util-unittest.c:103
SCLogDebug
#define SCLogDebug(...)
Definition: util-debug.h:269
PacketAlertCheck
int PacketAlertCheck(Packet *p, uint32_t sid)
Check if a certain sid alerted, this is used in the test functions.
Definition: detect-engine-alert.c:141
DetectEngineThreadCtx_::pmq
PrefilterRuleStore pmq
Definition: detect.h:1201
DetectEngineCtx_
main detection engine ctx
Definition: detect.h:836
PrefilterPacketHeaderCtx_::sigs_array
SigIntId * sigs_array
Definition: detect-engine-prefilter-common.h:43
DetectEngineCtxFree
void DetectEngineCtxFree(DetectEngineCtx *)
Free a DetectEngineCtx::
Definition: detect-engine.c:2580
DE_QUIET
#define DE_QUIET
Definition: detect.h:321
UTHBuildPacket
Packet * UTHBuildPacket(uint8_t *payload, uint16_t payload_len, uint8_t ipproto)
UTHBuildPacket is a wrapper that build packets with default ip and port fields.
Definition: util-unittest-helper.c:340
SigMatchSignatures
void SigMatchSignatures(ThreadVars *tv, DetectEngineCtx *de_ctx, DetectEngineThreadCtx *det_ctx, Packet *p)
wrapper for old tests
Definition: detect.c:1884
PrefilterPacketHeaderCtx_::sigs_cnt
uint32_t sigs_cnt
Definition: detect-engine-prefilter-common.h:42
SigCleanSignatures
void SigCleanSignatures(DetectEngineCtx *de_ctx)
Definition: detect-engine-build.c:54
SigTableElmt_::Setup
int(* Setup)(DetectEngineCtx *, Signature *, const char *)
Definition: detect.h:1278
detect-engine-prefilter.h
util-unittest.h
util-unittest-helper.h
TCPHdr_::th_ack
uint32_t th_ack
Definition: decode-tcp.h:146
SigTableElmt_::SetupPrefilter
int(* SetupPrefilter)(DetectEngineCtx *de_ctx, struct SigGroupHead_ *sgh)
Definition: detect.h:1281
Signature_::next
struct Signature_ * next
Definition: detect.h:665
PKT_IS_TCP
#define PKT_IS_TCP(p)
Definition: decode.h:248
PrefilterPacketHeaderCtx_
Definition: detect-engine-prefilter-common.h:35
decode.h
util-debug.h
de_ctx
DetectEngineCtx * de_ctx
Definition: fuzz_siginit.c:17
DetectEngineThreadCtx_
Definition: detect.h:1092
PrefilterPacketHeaderValue::u32
uint32_t u32[4]
Definition: detect-engine-prefilter-common.h:26
detect-engine-mpm.h
detect.h
ThreadVars_
Per thread variable structure.
Definition: threadvars.h:57
SigMatch_::next
struct SigMatch_ * next
Definition: detect.h:351
StringParseUint32
int StringParseUint32(uint32_t *res, int base, size_t len, const char *str)
Definition: util-byte.c:313
DETECT_SM_LIST_MATCH
@ DETECT_SM_LIST_MATCH
Definition: detect.h:111
SigInit
Signature * SigInit(DetectEngineCtx *de_ctx, const char *sigstr)
Parses a signature and adds it to the Detection Engine Context.
Definition: detect-parse.c:2314
DetectAckData_::ack
uint32_t ack
Definition: detect-tcp-ack.h:31
DETECT_ACK
@ DETECT_ACK
Definition: detect-engine-register.h:36
SigGroupCleanup
int SigGroupCleanup(DetectEngineCtx *de_ctx)
Definition: detect-engine-build.c:2218
Signature_::flags
uint32_t flags
Definition: detect.h:594
Packet_
Definition: decode.h:437
detect-engine-build.h
detect-engine-alert.h
Signature_::init_data
SignatureInitData * init_data
Definition: detect.h:662
SigTableElmt_::Match
int(* Match)(DetectEngineThreadCtx *, Packet *, const Signature *, const SigMatchCtx *)
Definition: detect.h:1261
SigGroupBuild
int SigGroupBuild(DetectEngineCtx *de_ctx)
Convert the signature list into the runtime match structure.
Definition: detect-engine-build.c:2149
PrefilterPacketHeaderCtx_::v1
PrefilterPacketHeaderValue v1
Definition: detect-engine-prefilter-common.h:36
SigMatchCtx_
Used to start a pointer to SigMatch context Should never be dereferenced without casting to something...
Definition: detect.h:342
DetectAckRegister
void DetectAckRegister(void)
Registration function for ack: keyword.
Definition: detect-tcp-ack.c:56
DetectEngineThreadCtxInit
TmEcode DetectEngineThreadCtxInit(ThreadVars *, void *, void **)
initialize thread specific detection engine context
Definition: detect-engine.c:3291
SigTableElmt_::alias
const char * alias
Definition: detect.h:1294
suricata-common.h
DetectEngineThreadCtxDeinit
TmEcode DetectEngineThreadCtxDeinit(ThreadVars *, void *)
Definition: detect-engine.c:3501
SigMatch_::type
uint16_t type
Definition: detect.h:348
Packet_::tcph
TCPHdr * tcph
Definition: decode.h:567
sigmatch_table
SigTableElmt sigmatch_table[DETECT_TBLSIZE]
Definition: detect-parse.c:127
DetectEngineCtx_::sig_list
Signature * sig_list
Definition: detect.h:844
PrefilterSetupPacketHeader
int PrefilterSetupPacketHeader(DetectEngineCtx *de_ctx, SigGroupHead *sgh, int sm_type, void(*Set)(PrefilterPacketHeaderValue *v, void *), bool(*Compare)(PrefilterPacketHeaderValue v, void *), void(*Match)(DetectEngineThreadCtx *det_ctx, Packet *p, const void *pectx))
Definition: detect-engine-prefilter-common.c:417
SCMalloc
#define SCMalloc(sz)
Definition: util-mem.h:47
detect-tcp-ack.h
SCFree
#define SCFree(p)
Definition: util-mem.h:61
SigTableElmt_::SupportsPrefilter
bool(* SupportsPrefilter)(const Signature *s)
Definition: detect.h:1280
detect-parse.h
Signature_
Signature container.
Definition: detect.h:593
SigMatch_
a single match condition for a signature
Definition: detect.h:347
DetectEngineCtxInit
DetectEngineCtx * DetectEngineCtxInit(void)
Definition: detect-engine.c:2541
PrefilterPacketHeaderValue
Definition: detect-engine-prefilter-common.h:23
SigMatchAppendSMToList
SigMatch * SigMatchAppendSMToList(DetectEngineCtx *de_ctx, Signature *s, uint16_t type, SigMatchCtx *ctx, const int list)
Append a SigMatch to the list type.
Definition: detect-parse.c:447
TCP_GET_ACK
#define TCP_GET_ACK(p)
Definition: decode-tcp.h:115
DetectEngineCtx_::flags
uint8_t flags
Definition: detect.h:838
detect-engine-prefilter-common.h
DetectAckData_
ack data
Definition: detect-tcp-ack.h:30
SigTableElmt_::RegisterTests
void(* RegisterTests)(void)
Definition: detect.h:1285
SIG_FLAG_REQUIRE_PACKET
#define SIG_FLAG_REQUIRE_PACKET
Definition: detect.h:246