suricata
detect-tls-cert-fingerprint.c
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1 /* Copyright (C) 2017 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 "debug.h"
29 #include "decode.h"
30 #include "detect.h"
31 
32 #include "detect-parse.h"
33 #include "detect-engine.h"
34 #include "detect-engine-mpm.h"
36 #include "detect-content.h"
37 #include "detect-pcre.h"
39 
40 #include "flow.h"
41 #include "flow-util.h"
42 #include "flow-var.h"
43 
44 #include "util-debug.h"
45 #include "util-unittest.h"
46 #include "util-spm.h"
47 #include "util-print.h"
48 
49 #include "stream-tcp.h"
50 
51 #include "app-layer.h"
52 #include "app-layer-ssl.h"
53 
54 #include "util-unittest.h"
55 #include "util-unittest-helper.h"
56 
57 static int DetectTlsFingerprintSetup(DetectEngineCtx *, Signature *, const char *);
58 #ifdef UNITTESTS
59 static void DetectTlsFingerprintRegisterTests(void);
60 #endif
61 static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
62  const DetectEngineTransforms *transforms,
63  Flow *f, const uint8_t flow_flags,
64  void *txv, const int list_id);
65 static void DetectTlsFingerprintSetupCallback(const DetectEngineCtx *de_ctx,
66  Signature *s);
67 static _Bool DetectTlsFingerprintValidateCallback(const Signature *s,
68  const char **sigerror);
69 static int g_tls_cert_fingerprint_buffer_id = 0;
70 
71 /**
72  * \brief Registration function for keyword: tls.cert_fingerprint
73  */
75 {
76  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].name = "tls.cert_fingerprint";
77  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].alias = "tls_cert_fingerprint";
78  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].desc = "match on the TLS cert fingerprint buffer";
79  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].url = DOC_URL DOC_VERSION "/rules/tls-keywords.html#tls-cert-fingerprint";
80  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].Setup = DetectTlsFingerprintSetup;
81 #ifdef UNITTESTS
82  sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].RegisterTests = DetectTlsFingerprintRegisterTests;
83 #endif
86 
87  DetectAppLayerInspectEngineRegister2("tls.cert_fingerprint", ALPROTO_TLS,
90 
91  DetectAppLayerMpmRegister2("tls.cert_fingerprint", SIG_FLAG_TOCLIENT, 2,
94 
95  DetectBufferTypeSetDescriptionByName("tls.cert_fingerprint",
96  "TLS certificate fingerprint");
97 
98  DetectBufferTypeRegisterSetupCallback("tls.cert_fingerprint",
99  DetectTlsFingerprintSetupCallback);
100 
101  DetectBufferTypeRegisterValidateCallback("tls.cert_fingerprint",
102  DetectTlsFingerprintValidateCallback);
103 
104  g_tls_cert_fingerprint_buffer_id = DetectBufferTypeGetByName("tls.cert_fingerprint");
105 }
106 
107 /**
108  * \brief this function setup the tls_cert_fingerprint modifier keyword used in the rule
109  *
110  * \param de_ctx Pointer to the Detection Engine Context
111  * \param s Pointer to the Signature to which the current keyword belongs
112  * \param str Should hold an empty string always
113  *
114  * \retval 0 On success
115  * \retval -1 On failure
116  */
117 static int DetectTlsFingerprintSetup(DetectEngineCtx *de_ctx, Signature *s,
118  const char *str)
119 {
120  if (DetectBufferSetActiveList(s, g_tls_cert_fingerprint_buffer_id) < 0)
121  return -1;
122 
124  return -1;
125 
126  return 0;
127 }
128 
129 static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
130  const DetectEngineTransforms *transforms, Flow *f,
131  const uint8_t flow_flags, void *txv, const int list_id)
132 {
133  InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
134  if (buffer->inspect == NULL) {
135  const SSLState *ssl_state = (SSLState *)f->alstate;
136 
137  if (ssl_state->server_connp.cert0_fingerprint == NULL) {
138  return NULL;
139  }
140 
141  const uint32_t data_len = strlen(ssl_state->server_connp.cert0_fingerprint);
142  const uint8_t *data = (uint8_t *)ssl_state->server_connp.cert0_fingerprint;
143 
144  InspectionBufferSetup(buffer, data, data_len);
145  InspectionBufferApplyTransforms(buffer, transforms);
146  }
147 
148  return buffer;
149 }
150 
151 static _Bool DetectTlsFingerprintValidateCallback(const Signature *s,
152  const char **sigerror)
153 {
154  const SigMatch *sm = s->init_data->smlists[g_tls_cert_fingerprint_buffer_id];
155  for ( ; sm != NULL; sm = sm->next)
156  {
157  if (sm->type != DETECT_CONTENT)
158  continue;
159 
160  const DetectContentData *cd = (DetectContentData *)sm->ctx;
161 
162  if (cd->content_len != 59) {
163  *sigerror = "Invalid length of the specified fingerprint. "
164  "This rule will therefore never match.";
165  SCLogWarning(SC_WARN_POOR_RULE, "rule %u: %s", s->id, *sigerror);
166  return FALSE;
167  }
168 
169  _Bool have_delimiters = FALSE;
170  uint32_t u;
171  for (u = 0; u < cd->content_len; u++)
172  {
173  if (cd->content[u] == ':') {
174  have_delimiters = TRUE;
175  break;
176  }
177  }
178 
179  if (have_delimiters == FALSE) {
180  *sigerror = "No colon delimiters ':' detected in content after "
181  "tls.cert_fingerprint. This rule will therefore "
182  "never match.";
183  SCLogWarning(SC_WARN_POOR_RULE, "rule %u: %s", s->id, *sigerror);
184  return FALSE;
185  }
186 
187  if (cd->flags & DETECT_CONTENT_NOCASE) {
188  *sigerror = "tls.cert_fingerprint should not be used together "
189  "with nocase, since the rule is automatically "
190  "lowercased anyway which makes nocase redundant.";
191  SCLogWarning(SC_WARN_POOR_RULE, "rule %u: %s", s->id, *sigerror);
192  }
193  }
194 
195  return TRUE;
196 }
197 
198 static void DetectTlsFingerprintSetupCallback(const DetectEngineCtx *de_ctx,
199  Signature *s)
200 {
201  SigMatch *sm = s->init_data->smlists[g_tls_cert_fingerprint_buffer_id];
202  for ( ; sm != NULL; sm = sm->next)
203  {
204  if (sm->type != DETECT_CONTENT)
205  continue;
206 
208 
209  _Bool changed = FALSE;
210  uint32_t u;
211  for (u = 0; u < cd->content_len; u++)
212  {
213  if (isupper(cd->content[u])) {
214  cd->content[u] = tolower(cd->content[u]);
215  changed = TRUE;
216  }
217  }
218 
219  /* recreate the context if changes were made */
220  if (changed) {
221  SpmDestroyCtx(cd->spm_ctx);
222  cd->spm_ctx = SpmInitCtx(cd->content, cd->content_len, 1,
223  de_ctx->spm_global_thread_ctx);
224  }
225  }
226 }
227 
228 #ifdef UNITTESTS
230 #endif
SigTableElmt sigmatch_table[DETECT_TBLSIZE]
Definition: detect.h:1448
SignatureInitData * init_data
Definition: detect.h:591
int(* Setup)(DetectEngineCtx *, Signature *, const char *)
Definition: detect.h:1186
SpmGlobalThreadCtx * spm_global_thread_ctx
Definition: detect.h:815
int DetectSignatureSetAppProto(Signature *s, AppProto alproto)
uint32_t id
Definition: detect.h:555
#define FALSE
char * cert0_fingerprint
SSLStateConnp server_connp
void DetectBufferTypeRegisterSetupCallback(const char *name, void(*SetupCallback)(const DetectEngineCtx *, Signature *))
InspectionBuffer * InspectionBufferGet(DetectEngineThreadCtx *det_ctx, const int list_id)
const char * name
Definition: detect.h:1200
Signature container.
Definition: detect.h:522
#define TRUE
void DetectAppLayerMpmRegister2(const char *name, int direction, int priority, int(*PrefilterRegister)(DetectEngineCtx *de_ctx, SigGroupHead *sgh, MpmCtx *mpm_ctx, const DetectBufferMpmRegistery *mpm_reg, int list_id), InspectionBufferGetDataPtr GetData, AppProto alproto, int tx_min_progress)
register a MPM engine
struct SigMatch_ * next
Definition: detect.h:322
main detection engine ctx
Definition: detect.h:761
SSLv[2.0|3.[0|1|2|3]] state structure.
void * alstate
Definition: flow.h:438
int DetectBufferTypeGetByName(const char *name)
#define str(s)
#define SIG_FLAG_TOCLIENT
Definition: detect.h:237
#define SIGMATCH_INFO_STICKY_BUFFER
Definition: detect.h:1393
SpmCtx * SpmInitCtx(const uint8_t *needle, uint16_t needle_len, int nocase, SpmGlobalThreadCtx *global_thread_ctx)
Definition: util-spm.c:166
void DetectAppLayerInspectEngineRegister2(const char *name, AppProto alproto, uint32_t dir, int progress, InspectEngineFuncPtr2 Callback2, InspectionBufferGetDataPtr GetData)
register inspect engine at start up time
void DetectTlsFingerprintRegister(void)
Registration function for keyword: tls.cert_fingerprint.
uint8_t type
Definition: detect.h:319
int 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.
#define SCLogWarning(err_code,...)
Macro used to log WARNING messages.
Definition: util-debug.h:281
const char * desc
Definition: detect.h:1202
struct SigMatch_ ** smlists
Definition: detect.h:516
int PrefilterGenericMpmRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh, MpmCtx *mpm_ctx, const DetectBufferMpmRegistery *mpm_reg, int list_id)
SigMatchCtx * ctx
Definition: detect.h:321
const char * alias
Definition: detect.h:1201
void InspectionBufferSetup(InspectionBuffer *buffer, const uint8_t *data, const uint32_t data_len)
setup the buffer with our initial data
void InspectionBufferApplyTransforms(InspectionBuffer *buffer, const DetectEngineTransforms *transforms)
#define SIGMATCH_NOOPT
Definition: detect.h:1369
void SpmDestroyCtx(SpmCtx *ctx)
Definition: util-spm.c:176
const char * url
Definition: detect.h:1203
int DetectBufferSetActiveList(Signature *s, const int list)
const uint8_t * inspect
Definition: detect.h:343
#define DOC_URL
Definition: suricata.h:86
void DetectBufferTypeSetDescriptionByName(const char *name, const char *desc)
#define DETECT_CONTENT_NOCASE
void DetectBufferTypeRegisterValidateCallback(const char *name, _Bool(*ValidateCallback)(const Signature *, const char **sigerror))
#define DOC_VERSION
Definition: suricata.h:91
uint16_t flags
Definition: detect.h:1194
Flow data structure.
Definition: flow.h:325
void(* RegisterTests)(void)
Definition: detect.h:1192
a single match condition for a signature
Definition: detect.h:318