suricata
app-layer-ssl.h
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1 /* Copyright (C) 2007-2022 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 Anoop Saldanha <anoopsaldanha@gmail.com>
22  * \author Pierre Chifflier <pierre.chifflier@ssi.gouv.fr>
23  *
24  */
25 
26 #ifndef SURICATA_APP_LAYER_SSL_H
27 #define SURICATA_APP_LAYER_SSL_H
28 
29 #include "util-ja3.h"
30 #include "rust.h"
31 
33  TLS_FRAME_PDU = 0, /**< whole PDU, so header + data */
34  TLS_FRAME_HDR, /**< only header portion */
35  TLS_FRAME_DATA, /**< only data portion */
40 };
41 
42 enum {
43  /* TLS protocol messages */
59  /* Certificates decoding messages */
74 };
75 
76 enum {
81 };
82 
83 /* Flag to indicate that server will now on send encrypted msgs */
84 #define SSL_AL_FLAG_SERVER_CHANGE_CIPHER_SPEC BIT_U32(0)
85 /* Flag to indicate that client will now on send encrypted msgs */
86 #define SSL_AL_FLAG_CLIENT_CHANGE_CIPHER_SPEC BIT_U32(1)
87 #define SSL_AL_FLAG_CHANGE_CIPHER_SPEC BIT_U32(2)
88 
89 /* SSL related flags */
90 #define SSL_AL_FLAG_SSL_CLIENT_HS BIT_U32(3)
91 #define SSL_AL_FLAG_SSL_SERVER_HS BIT_U32(4)
92 #define SSL_AL_FLAG_SSL_CLIENT_MASTER_KEY BIT_U32(5)
93 #define SSL_AL_FLAG_SSL_CLIENT_SSN_ENCRYPTED BIT_U32(6)
94 #define SSL_AL_FLAG_SSL_SERVER_SSN_ENCRYPTED BIT_U32(7)
95 #define SSL_AL_FLAG_SSL_NO_SESSION_ID BIT_U32(8)
96 
97 /* flags specific to detect-ssl-state keyword */
98 #define SSL_AL_FLAG_STATE_CLIENT_HELLO BIT_U32(9)
99 #define SSL_AL_FLAG_STATE_SERVER_HELLO BIT_U32(10)
100 #define SSL_AL_FLAG_STATE_CLIENT_KEYX BIT_U32(11)
101 #define SSL_AL_FLAG_STATE_SERVER_KEYX BIT_U32(12)
102 #define SSL_AL_FLAG_STATE_UNKNOWN BIT_U32(13)
103 
104 /* flag to indicate that session is finished */
105 #define SSL_AL_FLAG_STATE_FINISHED BIT_U32(14)
106 
107 /* flags specific to HeartBeat state */
108 #define SSL_AL_FLAG_HB_INFLIGHT BIT_U32(15)
109 #define SSL_AL_FLAG_HB_CLIENT_INIT BIT_U32(16)
110 #define SSL_AL_FLAG_HB_SERVER_INIT BIT_U32(17)
111 
112 /* flag to indicate that handshake is done */
113 #define SSL_AL_FLAG_HANDSHAKE_DONE BIT_U32(18)
114 
115 /* Session resumed without a full handshake */
116 #define SSL_AL_FLAG_SESSION_RESUMED BIT_U32(20)
117 
118 /* Encountered a supported_versions extension in client hello */
119 #define SSL_AL_FLAG_CH_VERSION_EXTENSION BIT_U32(21)
120 
121 /* Log the session even without ever seeing a certificate. This is used
122  to log TLSv1.3 sessions. */
123 #define SSL_AL_FLAG_LOG_WITHOUT_CERT BIT_U32(22)
124 
125 /* Encountered a early data extension in client hello. This extension is
126  used by 0-RTT. */
127 #define SSL_AL_FLAG_EARLY_DATA BIT_U32(23)
128 
129 /* flag to indicate that server random was filled */
130 #define TLS_TS_RANDOM_SET BIT_U32(24)
131 
132 /* flag to indicate that client random was filled */
133 #define TLS_TC_RANDOM_SET BIT_U32(25)
134 
135 #define SSL_AL_FLAG_NEED_CLIENT_CERT BIT_U32(26)
136 
137 /* config flags */
138 #define SSL_TLS_LOG_PEM (1 << 0)
139 
140 /* extensions */
141 #define SSL_EXTENSION_SNI 0x0000
142 #define SSL_EXTENSION_ELLIPTIC_CURVES 0x000a
143 #define SSL_EXTENSION_EC_POINT_FORMATS 0x000b
144 #define SSL_EXTENSION_SESSION_TICKET 0x0023
145 #define SSL_EXTENSION_EARLY_DATA 0x002a
146 #define SSL_EXTENSION_SUPPORTED_VERSIONS 0x002b
147 
148 /* SNI types */
149 #define SSL_SNI_TYPE_HOST_NAME 0
150 
151 /* Max string length of the TLS version string */
152 #define SSL_VERSION_MAX_STRLEN 20
153 
154 /* TLS random bytes for the sticky buffer */
155 #define TLS_RANDOM_LEN 32
156 
157 /* SSL versions. We'll use a unified format for all, with the top byte
158  * holding the major version and the lower byte the minor version */
159 enum {
161  SSL_VERSION_2 = 0x0200,
162  SSL_VERSION_3 = 0x0300,
163  TLS_VERSION_10 = 0x0301,
164  TLS_VERSION_11 = 0x0302,
165  TLS_VERSION_12 = 0x0303,
166  TLS_VERSION_13 = 0x0304,
186 };
187 
188 static inline bool TLSVersionValid(const uint16_t version)
189 {
190  switch (version) {
191  case TLS_VERSION_13:
192  case TLS_VERSION_12:
193  case TLS_VERSION_11:
194  case TLS_VERSION_10:
195  case SSL_VERSION_3:
196 
216  return true;
217  }
218  return false;
219 }
220 
221 typedef struct SSLCertsChain_ {
222  uint8_t *cert_data;
223  uint32_t cert_len;
226 
227 
228 typedef struct SSLStateConnp_ {
229  /* record length */
230  uint32_t record_length;
231  /* record length's length for SSLv2 */
233 
234  /* offset of the beginning of the current message (including header) */
235  uint32_t message_length;
236 
237  uint16_t version;
238  uint8_t content_type;
239 
240  uint8_t handshake_type;
241 
242  /* the no of bytes processed in the currently parsed record */
243  uint32_t bytes_processed;
244 
246 
254 
255  /* ssl server name indication extension */
256  char *sni;
257 
258  char *session_id;
259 
261 
262  uint8_t *certs_buffer;
264 
265  uint32_t cert_log_flag;
266 
268  char *ja3_hash;
269 
270  /* handshake tls fragmentation buffer. Handshake messages can be fragmented over multiple
271  * TLS records. */
272  uint8_t *hs_buffer;
275  uint32_t hs_buffer_size; /**< allocation size */
276  uint32_t hs_buffer_offset; /**< write offset */
278 
279 /**
280  * \brief SSLv[2.0|3.[0|1|2|3]] state structure.
281  *
282  * Structure to store the SSL state values.
283  */
284 typedef struct SSLState_ {
285  Flow *f;
286 
287  AppLayerStateData state_data;
289 
290  /* holds some state flags we need */
291  uint32_t flags;
292 
293  /* there might be a better place to store this*/
294  uint32_t hb_record_len;
295 
296  uint16_t events;
297 
298  uint32_t current_flags;
299 
301 
305 
306 void RegisterSSLParsers(void);
307 void SSLVersionToString(uint16_t, char *);
308 void SSLEnableJA3(void);
309 bool SSLJA3IsEnabled(void);
310 
311 #endif /* SURICATA_APP_LAYER_SSL_H */
TLS_VERSION_10
@ TLS_VERSION_10
Definition: app-layer-ssl.h:163
TLS_DECODER_EVENT_DATALEAK_HEARTBEAT_MISMATCH
@ TLS_DECODER_EVENT_DATALEAK_HEARTBEAT_MISMATCH
Definition: app-layer-ssl.h:53
TLS_VERSION_13_DRAFT20
@ TLS_VERSION_13_DRAFT20
Definition: app-layer-ssl.h:175
SSLStateConnp_::cert0_subject
char * cert0_subject
Definition: app-layer-ssl.h:248
TLS_DECODER_EVENT_CERTIFICATE_INVALID_SUBJECT
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_SUBJECT
Definition: app-layer-ssl.h:69
SSLState_
SSLv[2.0|3.[0|1|2|3]] state structure.
Definition: app-layer-ssl.h:284
JA3Buffer_
Definition: util-ja3.h:31
SSLCertsChain_::cert_len
uint32_t cert_len
Definition: app-layer-ssl.h:223
TLS_STATE_CERT_READY
@ TLS_STATE_CERT_READY
Definition: app-layer-ssl.h:78
TLS_DECODER_EVENT_TOO_MANY_RECORDS_IN_PACKET
@ TLS_DECODER_EVENT_TOO_MANY_RECORDS_IN_PACKET
Definition: app-layer-ssl.h:58
SSL_VERSION_3
@ SSL_VERSION_3
Definition: app-layer-ssl.h:162
TLS_VERSION_13_DRAFT21
@ TLS_VERSION_13_DRAFT21
Definition: app-layer-ssl.h:174
SSLState_::hb_record_len
uint32_t hb_record_len
Definition: app-layer-ssl.h:294
SSLStateConnp_::message_length
uint32_t message_length
Definition: app-layer-ssl.h:235
SSLState_::client_connp
SSLStateConnp client_connp
Definition: app-layer-ssl.h:302
TLS_FRAME_DATA
@ TLS_FRAME_DATA
Definition: app-layer-ssl.h:35
TLS_VERSION_13_DRAFT19
@ TLS_VERSION_13_DRAFT19
Definition: app-layer-ssl.h:176
SSLStateConnp_::bytes_processed
uint32_t bytes_processed
Definition: app-layer-ssl.h:243
next
struct HtpBodyChunk_ * next
Definition: app-layer-htp.h:0
SSLState_::server_connp
SSLStateConnp server_connp
Definition: app-layer-ssl.h:303
SSLStateConnp_::cert0_not_before
int64_t cert0_not_before
Definition: app-layer-ssl.h:251
TLS_DECODER_EVENT_CERTIFICATE_INVALID_ALGORITHMIDENTIFIER
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_ALGORITHMIDENTIFIER
Definition: app-layer-ssl.h:64
SSLStateConnp_
Definition: app-layer-ssl.h:228
TLS_DECODER_EVENT_CERTIFICATE_INVALID_DER
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_DER
Definition: app-layer-ssl.h:68
TLS_DECODER_EVENT_INVALID_RECORD_TYPE
@ TLS_DECODER_EVENT_INVALID_RECORD_TYPE
Definition: app-layer-ssl.h:47
SSLStateConnp_::ja3_hash
char * ja3_hash
Definition: app-layer-ssl.h:268
SSLStateConnp_::session_id_length
uint16_t session_id_length
Definition: app-layer-ssl.h:245
Flow_
Flow data structure.
Definition: flow.h:350
SSLState_::f
Flow * f
Definition: app-layer-ssl.h:285
TLS_DECODER_EVENT_INVALID_SSL_RECORD
@ TLS_DECODER_EVENT_INVALID_SSL_RECORD
Definition: app-layer-ssl.h:73
TLS_DECODER_EVENT_INVALID_RECORD_VERSION
@ TLS_DECODER_EVENT_INVALID_RECORD_VERSION
Definition: app-layer-ssl.h:46
TLS_VERSION_11
@ TLS_VERSION_11
Definition: app-layer-ssl.h:164
SSLState_::tx_data
AppLayerTxData tx_data
Definition: app-layer-ssl.h:288
SSLState_::curr_connp
SSLStateConnp * curr_connp
Definition: app-layer-ssl.h:300
rust.h
util-ja3.h
TLS_DECODER_EVENT_INVALID_SNI_TYPE
@ TLS_DECODER_EVENT_INVALID_SNI_TYPE
Definition: app-layer-ssl.h:56
SSLState_::state_data
AppLayerStateData state_data
Definition: app-layer-ssl.h:287
SSL_VERSION_2
@ SSL_VERSION_2
Definition: app-layer-ssl.h:161
SSLStateConnp_::sni
char * sni
Definition: app-layer-ssl.h:256
TLS_DECODER_EVENT_INVALID_TLS_HEADER
@ TLS_DECODER_EVENT_INVALID_TLS_HEADER
Definition: app-layer-ssl.h:45
SSLVersionToString
void SSLVersionToString(uint16_t, char *)
Definition: app-layer-ssl.c:340
TLS_DECODER_EVENT_INVALID_SNI_LENGTH
@ TLS_DECODER_EVENT_INVALID_SNI_LENGTH
Definition: app-layer-ssl.h:57
SSLStateConnp_::hs_buffer_message_type
uint8_t hs_buffer_message_type
Definition: app-layer-ssl.h:273
SSLStateConnp_::record_lengths_length
uint32_t record_lengths_length
Definition: app-layer-ssl.h:232
TLS_FRAME_SSLV2_HDR
@ TLS_FRAME_SSLV2_HDR
Definition: app-layer-ssl.h:38
SSLStateConnp_::cert0_issuerdn
char * cert0_issuerdn
Definition: app-layer-ssl.h:249
TLS_DECODER_EVENT_CERTIFICATE_INVALID_DATE
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_DATE
Definition: app-layer-ssl.h:66
TLS_VERSION_13_PRE_DRAFT16
@ TLS_VERSION_13_PRE_DRAFT16
Definition: app-layer-ssl.h:180
SSLStateConnp_::hs_buffer_size
uint32_t hs_buffer_size
Definition: app-layer-ssl.h:275
TLS_FRAME_HB_DATA
@ TLS_FRAME_HB_DATA
Definition: app-layer-ssl.h:37
SSLStateConnp_::cert0_not_after
int64_t cert0_not_after
Definition: app-layer-ssl.h:252
SSLStateConnp
struct SSLStateConnp_ SSLStateConnp
SSLState_::current_flags
uint32_t current_flags
Definition: app-layer-ssl.h:298
TLS_DECODER_EVENT_MULTIPLE_SNI_EXTENSIONS
@ TLS_DECODER_EVENT_MULTIPLE_SNI_EXTENSIONS
Definition: app-layer-ssl.h:55
TLS_DECODER_EVENT_ERROR_MSG_ENCOUNTERED
@ TLS_DECODER_EVENT_ERROR_MSG_ENCOUNTERED
Definition: app-layer-ssl.h:72
TLS_DECODER_EVENT_CERTIFICATE_INVALID_LENGTH
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_LENGTH
Definition: app-layer-ssl.h:61
TLS_DECODER_EVENT_CERTIFICATE_INVALID_VALIDITY
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_VALIDITY
Definition: app-layer-ssl.h:71
TLS_DECODER_EVENT_INVALID_SSLV2_HEADER
@ TLS_DECODER_EVENT_INVALID_SSLV2_HEADER
Definition: app-layer-ssl.h:44
TLS_VERSION_13_DRAFT28
@ TLS_VERSION_13_DRAFT28
Definition: app-layer-ssl.h:167
TLS_DECODER_EVENT_INVALID_HEARTBEAT
@ TLS_DECODER_EVENT_INVALID_HEARTBEAT
Definition: app-layer-ssl.h:51
SSLEnableJA3
void SSLEnableJA3(void)
if not explicitly disabled in config, enable ja3 support
Definition: app-layer-ssl.c:3090
SSLStateConnp_::handshake_type
uint8_t handshake_type
Definition: app-layer-ssl.h:240
TLS_VERSION_12
@ TLS_VERSION_12
Definition: app-layer-ssl.h:165
TLS_VERSION_13
@ TLS_VERSION_13
Definition: app-layer-ssl.h:166
SSLStateConnp_::hs_buffer_offset
uint32_t hs_buffer_offset
Definition: app-layer-ssl.h:276
SSLStateConnp_::certs_buffer
uint8_t * certs_buffer
Definition: app-layer-ssl.h:262
TLS_HANDSHAKE_DONE
@ TLS_HANDSHAKE_DONE
Definition: app-layer-ssl.h:79
SSLCertsChain_
Definition: app-layer-ssl.h:221
TlsFrameTypes
TlsFrameTypes
Definition: app-layer-ssl.h:32
TLS_DECODER_EVENT_CERTIFICATE_INVALID_EXTENSIONS
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_EXTENSIONS
Definition: app-layer-ssl.h:67
TLS_STATE_FINISHED
@ TLS_STATE_FINISHED
Definition: app-layer-ssl.h:80
TLS_RANDOM_LEN
#define TLS_RANDOM_LEN
Definition: app-layer-ssl.h:155
SSLState_::events
uint16_t events
Definition: app-layer-ssl.h:296
TLS_FRAME_SSLV2_PDU
@ TLS_FRAME_SSLV2_PDU
Definition: app-layer-ssl.h:39
TLS_DECODER_EVENT_CERTIFICATE_INVALID_VERSION
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_VERSION
Definition: app-layer-ssl.h:62
RegisterSSLParsers
void RegisterSSLParsers(void)
Function to register the SSL protocol parser and other functions.
Definition: app-layer-ssl.c:2955
TLS_DECODER_EVENT_CERTIFICATE_INVALID_SERIAL
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_SERIAL
Definition: app-layer-ssl.h:63
TLS_DECODER_EVENT_INVALID_HANDSHAKE_MESSAGE
@ TLS_DECODER_EVENT_INVALID_HANDSHAKE_MESSAGE
Definition: app-layer-ssl.h:49
TLS_VERSION_13_DRAFT24
@ TLS_VERSION_13_DRAFT24
Definition: app-layer-ssl.h:171
SSLStateConnp_::record_length
uint32_t record_length
Definition: app-layer-ssl.h:230
TLS_VERSION_13_DRAFT22_FB
@ TLS_VERSION_13_DRAFT22_FB
Definition: app-layer-ssl.h:183
TLS_VERSION_UNKNOWN
@ TLS_VERSION_UNKNOWN
Definition: app-layer-ssl.h:160
SSLCertsChain_::cert_data
uint8_t * cert_data
Definition: app-layer-ssl.h:222
SSLStateConnp_::certs_buffer_size
uint32_t certs_buffer_size
Definition: app-layer-ssl.h:263
TLS_VERSION_13_DRAFT23
@ TLS_VERSION_13_DRAFT23
Definition: app-layer-ssl.h:172
TLS_VERSION_13_DRAFT20_FB
@ TLS_VERSION_13_DRAFT20_FB
Definition: app-layer-ssl.h:181
TLS_VERSION_13_DRAFT26
@ TLS_VERSION_13_DRAFT26
Definition: app-layer-ssl.h:169
TLS_DECODER_EVENT_OVERFLOW_HEARTBEAT
@ TLS_DECODER_EVENT_OVERFLOW_HEARTBEAT
Definition: app-layer-ssl.h:52
AppLayerTxData
struct AppLayerTxData AppLayerTxData
Definition: detect.h:1355
SSLStateConnp_::random
uint8_t random[TLS_RANDOM_LEN]
Definition: app-layer-ssl.h:247
TLS_FRAME_PDU
@ TLS_FRAME_PDU
Definition: app-layer-ssl.h:33
TLS_VERSION_13_DRAFT27
@ TLS_VERSION_13_DRAFT27
Definition: app-layer-ssl.h:168
TLS_DECODER_EVENT_HEARTBEAT
@ TLS_DECODER_EVENT_HEARTBEAT
Definition: app-layer-ssl.h:50
version
uint8_t version
Definition: decode-gre.h:1
SSLStateConnp_::content_type
uint8_t content_type
Definition: app-layer-ssl.h:238
SSLStateConnp_::hs_buffer_message_size
uint32_t hs_buffer_message_size
Definition: app-layer-ssl.h:274
TLS_DECODER_EVENT_CERTIFICATE_INVALID_X509NAME
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_X509NAME
Definition: app-layer-ssl.h:65
TLS_VERSION_13_DRAFT21_FB
@ TLS_VERSION_13_DRAFT21_FB
Definition: app-layer-ssl.h:182
TLS_DECODER_EVENT_INVALID_RECORD_LENGTH
@ TLS_DECODER_EVENT_INVALID_RECORD_LENGTH
Definition: app-layer-ssl.h:48
TLS_STATE_IN_PROGRESS
@ TLS_STATE_IN_PROGRESS
Definition: app-layer-ssl.h:77
TLS_DECODER_EVENT_INVALID_CERTIFICATE
@ TLS_DECODER_EVENT_INVALID_CERTIFICATE
Definition: app-layer-ssl.h:60
TLS_VERSION_13_DRAFT26_FB
@ TLS_VERSION_13_DRAFT26_FB
Definition: app-layer-ssl.h:185
TLS_DECODER_EVENT_HANDSHAKE_INVALID_LENGTH
@ TLS_DECODER_EVENT_HANDSHAKE_INVALID_LENGTH
Definition: app-layer-ssl.h:54
SSLJA3IsEnabled
bool SSLJA3IsEnabled(void)
Definition: app-layer-ssl.c:3101
SSLStateConnp_::TAILQ_HEAD
TAILQ_HEAD(, SSLCertsChain_) certs
SSLStateConnp_::cert_log_flag
uint32_t cert_log_flag
Definition: app-layer-ssl.h:265
TLS_VERSION_13_DRAFT16
@ TLS_VERSION_13_DRAFT16
Definition: app-layer-ssl.h:179
TLS_FRAME_ALERT_DATA
@ TLS_FRAME_ALERT_DATA
Definition: app-layer-ssl.h:36
SSLCertsChain_::TAILQ_ENTRY
TAILQ_ENTRY(SSLCertsChain_) next
SSLStateConnp_::session_id
char * session_id
Definition: app-layer-ssl.h:258
TLS_FRAME_HDR
@ TLS_FRAME_HDR
Definition: app-layer-ssl.h:34
SSLStateConnp_::cert0_fingerprint
char * cert0_fingerprint
Definition: app-layer-ssl.h:253
SSLStateConnp_::ja3_str
JA3Buffer * ja3_str
Definition: app-layer-ssl.h:267
TLS_VERSION_13_DRAFT17
@ TLS_VERSION_13_DRAFT17
Definition: app-layer-ssl.h:178
SSLState
struct SSLState_ SSLState
SSLv[2.0|3.[0|1|2|3]] state structure.
SSLCertsChain
struct SSLCertsChain_ SSLCertsChain
TLS_VERSION_13_DRAFT18
@ TLS_VERSION_13_DRAFT18
Definition: app-layer-ssl.h:177
TLS_VERSION_13_DRAFT23_FB
@ TLS_VERSION_13_DRAFT23_FB
Definition: app-layer-ssl.h:184
SSLStateConnp_::hs_buffer
uint8_t * hs_buffer
Definition: app-layer-ssl.h:272
SSLStateConnp_::cert0_serial
char * cert0_serial
Definition: app-layer-ssl.h:250
TLS_VERSION_13_DRAFT25
@ TLS_VERSION_13_DRAFT25
Definition: app-layer-ssl.h:170
TLS_DECODER_EVENT_CERTIFICATE_INVALID_ISSUER
@ TLS_DECODER_EVENT_CERTIFICATE_INVALID_ISSUER
Definition: app-layer-ssl.h:70
TLS_VERSION_13_DRAFT22
@ TLS_VERSION_13_DRAFT22
Definition: app-layer-ssl.h:173
SSLState_::flags
uint32_t flags
Definition: app-layer-ssl.h:291
SSLStateConnp_::version
uint16_t version
Definition: app-layer-ssl.h:237