suricata
detect-tls-cert-fingerprint.c
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1 /* Copyright (C) 2017-2022 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 Mats Klepsland <mats.klepsland@gmail.com>
22  *
23  * Implements support for tls_cert_fingerprint keyword.
24  */
25 
26 #include "suricata-common.h"
27 #include "threads.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"
35 #include "detect-content.h"
36 #include "detect-pcre.h"
38 
39 #include "flow.h"
40 #include "flow-util.h"
41 #include "flow-var.h"
42 
43 #include "util-debug.h"
44 #include "util-spm.h"
45 #include "util-print.h"
46 
47 #include "stream-tcp.h"
48 
49 #include "app-layer.h"
50 #include "app-layer-ssl.h"
51 
52 #include "util-unittest.h"
53 #include "util-unittest-helper.h"
54 
55 static int DetectTlsFingerprintSetup(DetectEngineCtx *, Signature *, const char *);
56 #ifdef UNITTESTS
57 static void DetectTlsFingerprintRegisterTests(void);
58 #endif
59 static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
60  const DetectEngineTransforms *transforms,
61  Flow *f, const uint8_t flow_flags,
62  void *txv, const int list_id);
63 static void DetectTlsFingerprintSetupCallback(const DetectEngineCtx *de_ctx,
64  Signature *s);
65 static bool DetectTlsFingerprintValidateCallback(const Signature *s,
66  const char **sigerror);
67 static int g_tls_cert_fingerprint_buffer_id = 0;
68 
69 /**
70  * \brief Registration function for keyword: tls.cert_fingerprint
71  */
73 {
74  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].name = "tls.cert_fingerprint";
75  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].alias = "tls_cert_fingerprint";
77  "sticky buffer to match the TLS cert fingerprint buffer";
78  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].url = "/rules/tls-keywords.html#tls-cert-fingerprint";
79  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].Setup = DetectTlsFingerprintSetup;
80 #ifdef UNITTESTS
81  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].RegisterTests = DetectTlsFingerprintRegisterTests;
82 #endif
85 
88 
89  DetectAppLayerMpmRegister("tls.cert_fingerprint", SIG_FLAG_TOCLIENT, 2,
91 
94 
95  DetectAppLayerMpmRegister("tls.cert_fingerprint", SIG_FLAG_TOSERVER, 2,
97 
98  DetectBufferTypeSetDescriptionByName("tls.cert_fingerprint",
99  "TLS certificate fingerprint");
100 
101  DetectBufferTypeRegisterSetupCallback("tls.cert_fingerprint",
102  DetectTlsFingerprintSetupCallback);
103 
104  DetectBufferTypeRegisterValidateCallback("tls.cert_fingerprint",
105  DetectTlsFingerprintValidateCallback);
106 
107  g_tls_cert_fingerprint_buffer_id = DetectBufferTypeGetByName("tls.cert_fingerprint");
108 }
109 
110 /**
111  * \brief this function setup the tls_cert_fingerprint modifier keyword used in the rule
112  *
113  * \param de_ctx Pointer to the Detection Engine Context
114  * \param s Pointer to the Signature to which the current keyword belongs
115  * \param str Should hold an empty string always
116  *
117  * \retval 0 On success
118  * \retval -1 On failure
119  */
120 static int DetectTlsFingerprintSetup(DetectEngineCtx *de_ctx, Signature *s,
121  const char *str)
122 {
123  if (DetectBufferSetActiveList(de_ctx, s, g_tls_cert_fingerprint_buffer_id) < 0)
124  return -1;
125 
127  return -1;
128 
129  return 0;
130 }
131 
132 static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
133  const DetectEngineTransforms *transforms, Flow *f,
134  const uint8_t flow_flags, void *txv, const int list_id)
135 {
136  InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
137  if (buffer->inspect == NULL) {
138  const SSLState *ssl_state = (SSLState *)f->alstate;
139  const SSLStateConnp *connp;
140 
141  if (flow_flags & STREAM_TOSERVER) {
142  connp = &ssl_state->client_connp;
143  } else {
144  connp = &ssl_state->server_connp;
145  }
146 
147  if (connp->cert0_fingerprint == NULL) {
148  return NULL;
149  }
150 
151  const uint32_t data_len = strlen(connp->cert0_fingerprint);
152  const uint8_t *data = (uint8_t *)connp->cert0_fingerprint;
153 
154  InspectionBufferSetup(det_ctx, list_id, buffer, data, data_len);
155  InspectionBufferApplyTransforms(buffer, transforms);
156  }
157 
158  return buffer;
159 }
160 
161 static bool DetectTlsFingerprintValidateCallback(const Signature *s,
162  const char **sigerror)
163 {
164  for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
165  if (s->init_data->buffers[x].id != (uint32_t)g_tls_cert_fingerprint_buffer_id)
166  continue;
167  const SigMatch *sm = s->init_data->buffers[x].head;
168  for (; sm != NULL; sm = sm->next) {
169  if (sm->type != DETECT_CONTENT)
170  continue;
171 
172  const DetectContentData *cd = (DetectContentData *)sm->ctx;
173 
174  if (cd->content_len != 59) {
175  *sigerror = "Invalid length of the specified fingerprint. "
176  "This rule will therefore never match.";
177  SCLogWarning("rule %u: %s", s->id, *sigerror);
178  return false;
179  }
180 
181  bool have_delimiters = false;
182  uint32_t u;
183  for (u = 0; u < cd->content_len; u++) {
184  if (cd->content[u] == ':') {
185  have_delimiters = true;
186  break;
187  }
188  }
189 
190  if (!have_delimiters) {
191  *sigerror = "No colon delimiters ':' detected in content after "
192  "tls.cert_fingerprint. This rule will therefore "
193  "never match.";
194  SCLogWarning("rule %u: %s", s->id, *sigerror);
195  return false;
196  }
197 
198  if (cd->flags & DETECT_CONTENT_NOCASE) {
199  *sigerror = "tls.cert_fingerprint should not be used together "
200  "with nocase, since the rule is automatically "
201  "lowercased anyway which makes nocase redundant.";
202  SCLogWarning("rule %u: %s", s->id, *sigerror);
203  }
204  }
205  }
206  return true;
207 }
208 
209 static void DetectTlsFingerprintSetupCallback(const DetectEngineCtx *de_ctx,
210  Signature *s)
211 {
212  for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
213  if (s->init_data->buffers[x].id != (uint32_t)g_tls_cert_fingerprint_buffer_id)
214  continue;
215  SigMatch *sm = s->init_data->buffers[x].head;
216  for (; sm != NULL; sm = sm->next) {
217  if (sm->type != DETECT_CONTENT)
218  continue;
219 
221 
222  bool changed = false;
223  uint32_t u;
224  for (u = 0; u < cd->content_len; u++) {
225  if (isupper(cd->content[u])) {
226  cd->content[u] = u8_tolower(cd->content[u]);
227  changed = true;
228  }
229  }
230 
231  /* recreate the context if changes were made */
232  if (changed) {
233  SpmDestroyCtx(cd->spm_ctx);
234  cd->spm_ctx =
236  }
237  }
238  }
239 }
240 
241 #ifdef UNITTESTS
242 #include "detect-engine-alert.h"
244 #endif
DETECT_CONTENT_NOCASE
#define DETECT_CONTENT_NOCASE
Definition: detect-content.h:29
SigTableElmt_::url
const char * url
Definition: detect.h:1296
DetectSignatureSetAppProto
int DetectSignatureSetAppProto(Signature *s, AppProto alproto)
Definition: detect-parse.c:1753
SignatureInitDataBuffer_::head
SigMatch * head
Definition: detect.h:527
SSLState_
SSLv[2.0|3.[0|1|2|3]] state structure.
Definition: app-layer-ssl.h:288
detect-content.h
detect-engine.h
SIGMATCH_INFO_STICKY_BUFFER
#define SIGMATCH_INFO_STICKY_BUFFER
Definition: detect.h:1497
SigTableElmt_::desc
const char * desc
Definition: detect.h:1295
TLS_STATE_CERT_READY
@ TLS_STATE_CERT_READY
Definition: app-layer-ssl.h:78
DetectEngineInspectBufferGeneric
uint8_t DetectEngineInspectBufferGeneric(DetectEngineCtx *de_ctx, DetectEngineThreadCtx *det_ctx, const DetectEngineAppInspectionEngine *engine, const Signature *s, Flow *f, uint8_t flags, void *alstate, void *txv, uint64_t tx_id)
Do the content inspection & validation for a signature.
Definition: detect-engine.c:2122
flow-util.h
SigTableElmt_::name
const char * name
Definition: detect.h:1293
stream-tcp.h
DetectEngineTransforms
Definition: detect.h:406
DetectTlsFingerprintRegister
void DetectTlsFingerprintRegister(void)
Registration function for keyword: tls.cert_fingerprint.
Definition: detect-tls-cert-fingerprint.c:72
detect-tls-cert-fingerprint.h
SSLState_::client_connp
SSLStateConnp client_connp
Definition: app-layer-ssl.h:306
DETECT_CONTENT
@ DETECT_CONTENT
Definition: detect-engine-register.h:62
ALPROTO_TLS
@ ALPROTO_TLS
Definition: app-layer-protos.h:33
SSLState_::server_connp
SSLStateConnp server_connp
Definition: app-layer-ssl.h:307
DetectBufferSetActiveList
int DetectBufferSetActiveList(DetectEngineCtx *de_ctx, Signature *s, const int list)
Definition: detect-engine.c:1335
SSLStateConnp_
Definition: app-layer-ssl.h:230
InspectionBuffer
Definition: detect.h:371
threads.h
Flow_
Flow data structure.
Definition: flow.h:351
DetectBufferTypeRegisterSetupCallback
void DetectBufferTypeRegisterSetupCallback(const char *name, void(*SetupCallback)(const DetectEngineCtx *, Signature *))
Definition: detect-engine.c:1266
SigTableElmt_::flags
uint16_t flags
Definition: detect.h:1287
DetectEngineCtx_
main detection engine ctx
Definition: detect.h:836
u8_tolower
#define u8_tolower(c)
Definition: suricata-common.h:436
DetectContentData_
Definition: detect-content.h:93
SIG_FLAG_TOCLIENT
#define SIG_FLAG_TOCLIENT
Definition: detect.h:264
SigTableElmt_::Setup
int(* Setup)(DetectEngineCtx *, Signature *, const char *)
Definition: detect.h:1278
detect-pcre.h
detect-engine-prefilter.h
util-unittest.h
InspectionBufferGet
InspectionBuffer * InspectionBufferGet(DetectEngineThreadCtx *det_ctx, const int list_id)
Definition: detect-engine.c:1479
util-unittest-helper.h
DetectBufferTypeGetByName
int DetectBufferTypeGetByName(const char *name)
Definition: detect-engine.c:1072
SIG_FLAG_TOSERVER
#define SIG_FLAG_TOSERVER
Definition: detect.h:263
decode.h
util-debug.h
DetectBufferTypeRegisterValidateCallback
void DetectBufferTypeRegisterValidateCallback(const char *name, bool(*ValidateCallback)(const Signature *, const char **sigerror))
Definition: detect-engine.c:1284
de_ctx
DetectEngineCtx * de_ctx
Definition: fuzz_siginit.c:17
detect-tls-cert-fingerprint.c
DetectEngineThreadCtx_
Definition: detect.h:1092
util-print.h
detect-engine-mpm.h
detect.h
SigMatch_::next
struct SigMatch_ * next
Definition: detect.h:351
PrefilterGenericMpmRegister
int PrefilterGenericMpmRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh, MpmCtx *mpm_ctx, const DetectBufferMpmRegistry *mpm_reg, int list_id)
Definition: detect-engine-prefilter.c:745
SCLogWarning
#define SCLogWarning(...)
Macro used to log WARNING messages.
Definition: util-debug.h:249
DetectAppLayerMpmRegister
void DetectAppLayerMpmRegister(const char *name, int direction, int priority, PrefilterRegisterFunc PrefilterRegister, InspectionBufferGetDataPtr GetData, AppProto alproto, int tx_min_progress)
register a MPM engine
Definition: detect-engine-mpm.c:89
SigMatch_::ctx
SigMatchCtx * ctx
Definition: detect.h:350
detect-engine-alert.h
DetectContentData_::flags
uint32_t flags
Definition: detect-content.h:104
Signature_::init_data
SignatureInitData * init_data
Definition: detect.h:662
DETECT_AL_TLS_CERT_FINGERPRINT
@ DETECT_AL_TLS_CERT_FINGERPRINT
Definition: detect-engine-register.h:242
SigTableElmt_::alias
const char * alias
Definition: detect.h:1294
suricata-common.h
SigMatch_::type
uint16_t type
Definition: detect.h:348
InspectionBufferApplyTransforms
void InspectionBufferApplyTransforms(InspectionBuffer *buffer, const DetectEngineTransforms *transforms)
Definition: detect-engine.c:1678
sigmatch_table
SigTableElmt sigmatch_table[DETECT_TBLSIZE]
Definition: detect-parse.c:127
util-spm.h
DetectContentData_::content
uint8_t * content
Definition: detect-content.h:94
DetectContentData_::spm_ctx
SpmCtx * spm_ctx
Definition: detect-content.h:111
SignatureInitData_::buffers
SignatureInitDataBuffer * buffers
Definition: detect.h:583
InspectionBuffer::inspect
const uint8_t * inspect
Definition: detect.h:372
str
#define str(s)
Definition: suricata-common.h:291
InspectionBufferSetup
void InspectionBufferSetup(DetectEngineThreadCtx *det_ctx, const int list_id, InspectionBuffer *buffer, const uint8_t *data, const uint32_t data_len)
setup the buffer with our initial data
Definition: detect-engine.c:1574
Flow_::alstate
void * alstate
Definition: flow.h:476
Signature_::id
uint32_t id
Definition: detect.h:628
detect-parse.h
SignatureInitDataBuffer_::id
uint32_t id
Definition: detect.h:520
Signature_
Signature container.
Definition: detect.h:593
SigMatch_
a single match condition for a signature
Definition: detect.h:347
DetectContentData_::content_len
uint16_t content_len
Definition: detect-content.h:95
SIGMATCH_NOOPT
#define SIGMATCH_NOOPT
Definition: detect.h:1473
DetectAppLayerInspectEngineRegister
void DetectAppLayerInspectEngineRegister(const char *name, AppProto alproto, uint32_t dir, int progress, InspectEngineFuncPtr Callback, InspectionBufferGetDataPtr GetData)
register inspect engine at start up time
Definition: detect-engine.c:169
DetectEngineCtx_::spm_global_thread_ctx
SpmGlobalThreadCtx * spm_global_thread_ctx
Definition: detect.h:888
DetectBufferTypeSetDescriptionByName
void DetectBufferTypeSetDescriptionByName(const char *name, const char *desc)
Definition: detect-engine.c:1169
flow.h
SpmDestroyCtx
void SpmDestroyCtx(SpmCtx *ctx)
Definition: util-spm.c:183
SignatureInitData_::buffer_index
uint32_t buffer_index
Definition: detect.h:584
flow-var.h
SpmInitCtx
SpmCtx * SpmInitCtx(const uint8_t *needle, uint16_t needle_len, int nocase, SpmGlobalThreadCtx *global_thread_ctx)
Definition: util-spm.c:173
app-layer-ssl.h
SigTableElmt_::RegisterTests
void(* RegisterTests)(void)
Definition: detect.h:1285
app-layer.h