summaryrefslogtreecommitdiffstats
path: root/src/openvpn/ssl.h
blob: cd7cae2eb13f62d87eea0c5d538f7c10e38103e5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single TCP/UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
 *  Copyright (C) 2010 Fox Crypto B.V. <openvpn@fox-it.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program (see the file COPYING included with this
 *  distribution); if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/**
 * @file Control Channel SSL/Data channel negotiation module
 */

#ifndef OPENVPN_SSL_H
#define OPENVPN_SSL_H

#if defined(ENABLE_CRYPTO) && defined(ENABLE_SSL)

#include "basic.h"
#include "common.h"
#include "crypto.h"
#include "packet_id.h"
#include "session_id.h"
#include "reliable.h"
#include "socket.h"
#include "mtu.h"
#include "options.h"
#include "plugin.h"

#include "ssl_common.h"
#include "ssl_verify.h"
#include "ssl_backend.h"

/* Used in the TLS PRF function */
#define KEY_EXPANSION_ID "OpenVPN"

/* packet opcode (high 5 bits) and key-id (low 3 bits) are combined in one byte */
#define P_KEY_ID_MASK                  0x07
#define P_OPCODE_SHIFT                 3

/* packet opcodes -- the V1 is intended to allow protocol changes in the future */
#define P_CONTROL_HARD_RESET_CLIENT_V1 1     /* initial key from client, forget previous state */
#define P_CONTROL_HARD_RESET_SERVER_V1 2     /* initial key from server, forget previous state */
#define P_CONTROL_SOFT_RESET_V1        3     /* new key, graceful transition from old to new key */
#define P_CONTROL_V1                   4     /* control channel packet (usually TLS ciphertext) */
#define P_ACK_V1                       5     /* acknowledgement for packets received */
#define P_DATA_V1                      6     /* data channel packet */

/* indicates key_method >= 2 */
#define P_CONTROL_HARD_RESET_CLIENT_V2 7     /* initial key from client, forget previous state */
#define P_CONTROL_HARD_RESET_SERVER_V2 8     /* initial key from server, forget previous state */

/* define the range of legal opcodes */
#define P_FIRST_OPCODE                 1
#define P_LAST_OPCODE                  8

/* Should we aggregate TLS
 * acknowledgements, and tack them onto
 * control packets? */
#define TLS_AGGREGATE_ACK

/*
 * If TLS_AGGREGATE_ACK, set the
 * max number of acknowledgments that
 * can "hitch a ride" on an outgoing
 * non-P_ACK_V1 control packet.
 */
#define CONTROL_SEND_ACK_MAX 4

/*
 * Define number of buffers for send and receive in the reliability layer.
 */
#define TLS_RELIABLE_N_SEND_BUFFERS  4 /* also window size for reliablity layer */
#define TLS_RELIABLE_N_REC_BUFFERS   8

/*
 * Various timeouts
 */
#define TLS_MULTI_REFRESH 15    /* call tls_multi_process once every n seconds */
#define TLS_MULTI_HORIZON 2     /* call tls_multi_process frequently for n seconds after
				   every packet sent/received action */

/*
 * The SSL/TLS worker thread will wait at most this many seconds for the
 * interprocess communication pipe to the main thread to be ready to accept
 * writes.
 */
#define TLS_MULTI_THREAD_SEND_TIMEOUT 5

/* Interval that tls_multi_process should call tls_authentication_status */
#define TLS_MULTI_AUTH_STATUS_INTERVAL 10

/*
 * Buffer sizes (also see mtu.h).
 */

/* Maximum length of OCC options string passed as part of auth handshake */
#define TLS_OPTIONS_LEN 512

/* Default field in X509 to be username */
#define X509_USERNAME_FIELD_DEFAULT "CN"

/*
 * Range of key exchange methods
 */
#define KEY_METHOD_MIN 1
#define KEY_METHOD_MAX 2

/* key method taken from lower 4 bits */
#define KEY_METHOD_MASK 0x0F

/*
 * Measure success rate of TLS handshakes, for debugging only
 */
/* #define MEASURE_TLS_HANDSHAKE_STATS */

/*
 * Used in --mode server mode to check tls-auth signature on initial
 * packets received from new clients.
 */
struct tls_auth_standalone
{
  struct key_ctx_bi tls_auth_key;
  struct crypto_options tls_auth_options;
  struct frame frame;
};

/*
 * Prepare the SSL library for use
 */
void init_ssl_lib (void);

/*
 * Free any internal state that the SSL library might have
 */
void free_ssl_lib (void);

/**
 * Build master SSL context object that serves for the whole of OpenVPN
 * instantiation
 */
void init_ssl (const struct options *options, struct tls_root_ctx *ctx);

/** @addtogroup control_processor
 *  @{ */

/** @name Functions for initialization and cleanup of tls_multi structures
 *  @{ */

/**
 * Allocate and initialize a \c tls_multi structure.
 * @ingroup control_processor
 *
 * This function allocates a new \c tls_multi structure, and performs some
 * amount of initialization.  Afterwards, the \c tls_multi_init_finalize()
 * function must be called to finalize the structure's initialization
 * process.
 *
 * @param tls_options  - The configuration options to be used for this VPN
 *                       tunnel.
 *
 * @return A newly allocated and initialized \c tls_multi structure.
 */
struct tls_multi *tls_multi_init (struct tls_options *tls_options);

/**
 * Finalize initialization of a \c tls_multi structure.
 * @ingroup control_processor
 *
 * This function initializes the \c TM_ACTIVE \c tls_session, and in
 * server mode also the \c TM_UNTRUSTED \c tls_session, associated with
 * this \c tls_multi structure.  It also configures the control channel's
 * \c frame structure based on the data channel's \c frame given in
 * argument \a frame.
 *
 * @param multi        - The \c tls_multi structure of which to finalize
 *                       initialization.
 * @param frame        - The data channel's \c frame structure.
 */
void tls_multi_init_finalize(struct tls_multi *multi,
			     const struct frame *frame);

/*
 * Initialize a standalone tls-auth verification object.
 */
struct tls_auth_standalone *tls_auth_standalone_init (struct tls_options *tls_options,
						      struct gc_arena *gc);

/*
 * Finalize a standalone tls-auth verification object.
 */
void tls_auth_standalone_finalize (struct tls_auth_standalone *tas,
				   const struct frame *frame);

/*
 * Set local and remote option compatibility strings.
 * Used to verify compatibility of local and remote option
 * sets.
 */
void tls_multi_init_set_options(struct tls_multi* multi,
				const char *local,
				const char *remote);

/**
 * Cleanup a \c tls_multi structure and free associated memory
 * allocations.
 * @ingroup control_processor
 *
 * This function cleans up a \c tls_multi structure.  This includes
 * cleaning up all associated \c tls_session structures.
 *
 * @param multi        - The \c tls_multi structure to clean up in free.
 * @param clear        - Whether the memory allocated for the \a multi
 *                       object should be overwritten with 0s.
 */
void tls_multi_free (struct tls_multi *multi, bool clear);

/** @} name Functions for initialization and cleanup of tls_multi structures */

/** @} addtogroup control_processor */

#define TLSMP_INACTIVE 0
#define TLSMP_ACTIVE   1
#define TLSMP_KILL     2

/*
 * Called by the top-level event loop.
 *
 * Basically decides if we should call tls_process for
 * the active or untrusted sessions.
 */
int tls_multi_process (struct tls_multi *multi,
		       struct buffer *to_link,
		       struct link_socket_actual **to_link_addr,
		       struct link_socket_info *to_link_socket_info,
		       interval_t *wakeup);


/**************************************************************************/
/**
 * Determine whether an incoming packet is a data channel or control
 * channel packet, and process accordingly.
 * @ingroup external_multiplexer
 *
 * When OpenVPN is in TLS mode, this is the first function to process an
 * incoming packet.  It inspects the packet's one-byte header which
 * contains the packet's opcode and key ID.  Depending on the opcode, the
 * packet is processed as a data channel or as a control channel packet.
 *
 * @par Data channel packets
 *
 * If the opcode indicates the packet is a data channel packet, then the
 * packet's key ID is used to find the local TLS state it is associated
 * with.  This state is checked whether it is active, authenticated, and
 * its remote peer is the source of this packet.  If these checks passed,
 * the state's security parameters are loaded into the \a opt crypto
 * options so that \p openvpn_decrypt() can later use them to authenticate
 * and decrypt the packet.
 *
 * This function then returns false.  The \a buf buffer has not been
 * modified, except for removing the header.
 *
 * @par Control channel packets
 *
 * If the opcode indicates the packet is a control channel packet, then
 * this function will process it based on its plaintext header. depending
 * on the packet's opcode and session ID this function determines if it is
 * destined for an active TLS session, or whether a new TLS session should
 * be started.  This function also initiates data channel session key
 * renegotiation if the received opcode requests that.
 *
 * If the incoming packet is destined for an active TLS session, then the
 * packet is inserted into the Reliability Layer and will be handled
 * later.
 *
 * @param multi - The TLS multi structure associated with the VPN tunnel
 *     of this packet.
 * @param from - The source address of the packet.
 * @param buf - A buffer structure containing the incoming packet.
 * @param opt - A crypto options structure that will be loaded with the
 *     appropriate security parameters to handle the packet if it is a
 *     data channel packet.
 *
 * @return
 * @li True if the packet is a control channel packet that has been
 *     processed successfully.
 * @li False if the packet is a data channel packet, or if an error
 *     occurred during processing of a control channel packet.
 */
bool tls_pre_decrypt (struct tls_multi *multi,
		      const struct link_socket_actual *from,
		      struct buffer *buf,
		      struct crypto_options *opt);


/**************************************************************************/
/** @name Functions for managing security parameter state for data channel packets
 *  @{ */

/**
 * Inspect an incoming packet for which no VPN tunnel is active, and
 * determine whether a new VPN tunnel should be created.
 * @ingroup data_crypto
 *
 * This function receives the initial incoming packet from a client that
 * wishes to establish a new VPN tunnel, and determines the packet is a
 * valid initial packet.  It is only used when OpenVPN is running in
 * server mode.
 *
 * The tests performed by this function are whether the packet's opcode is
 * correct for establishing a new VPN tunnel, whether its key ID is 0, and
 * whether its size is not too large.  This function also performs the
 * initial HMAC firewall test, if configured to do so.
 *
 * The incoming packet and the local VPN tunnel state are not modified by
 * this function.  Its sole purpose is to inspect the packet and determine
 * whether a new VPN tunnel should be created.  If so, that new VPN tunnel
 * instance will handle processing of the packet.
 *
 * @param tas - The standalone TLS authentication setting structure for
 *     this process.
 * @param from - The source address of the packet.
 * @param buf - A buffer structure containing the incoming packet.
 *
 * @return
 * @li True if the packet is valid and a new VPN tunnel should be created
 *     for this client.
 * @li False if the packet is not valid, did not pass the HMAC firewall
 *     test, or some other error occurred.
 */
bool tls_pre_decrypt_lite (const struct tls_auth_standalone *tas,
			   const struct link_socket_actual *from,
			   const struct buffer *buf);


/**
 * Choose the appropriate security parameters with which to process an
 * outgoing packet.
 * @ingroup data_crypto
 *
 * If no appropriate security parameters can be found, or if some other
 * error occurs, then the buffer is set to empty.
 *
 * @param multi - The TLS state for this packet's destination VPN tunnel.
 * @param buf - The buffer containing the outgoing packet.
 * @param opt - The crypto options structure into which the appropriate
 *     security parameters should be loaded.
 */
void tls_pre_encrypt (struct tls_multi *multi,
		      struct buffer *buf, struct crypto_options *opt);


/**
 * Prepend the one-byte OpenVPN header to the packet, and perform some
 * accounting for the key state used.
 * @ingroup data_crypto
 *
 * @param multi - The TLS state for this packet's destination VPN tunnel.
 * @param buf - The buffer containing the outgoing packet.
 */
void tls_post_encrypt (struct tls_multi *multi, struct buffer *buf);

/** @} name Functions for managing security parameter state for data channel packets */

/*
 * Setup private key file password. If auth_file is given, use the
 * credentials stored in the file.
 */
void pem_password_setup (const char *auth_file);

/*
 * Setup authentication username and password. If auth_file is given, use the
 * credentials stored in the file.
 */
void auth_user_pass_setup (const char *auth_file, const struct static_challenge_info *sc_info);

/*
 * Ensure that no caching is performed on authentication information
 */
void ssl_set_auth_nocache (void);

/*
 * Purge any stored authentication information, both for key files and tunnel
 * authentication. If PCKS #11 is enabled, purge authentication for that too.
 */
void ssl_purge_auth (const bool auth_user_pass_only);

void ssl_set_auth_token (const char *token);

#ifdef ENABLE_CLIENT_CR
/*
 * ssl_get_auth_challenge will parse the server-pushed auth-failed
 * reason string and return a dynamically allocated
 * auth_challenge_info struct.
 */
void ssl_purge_auth_challenge (void);
void ssl_put_auth_challenge (const char *cr_str);
#endif

/*
 * Reserve any extra space required on frames.
 */
void tls_adjust_frame_parameters(struct frame *frame);

/*
 * Send a payload over the TLS control channel
 */
bool tls_send_payload (struct tls_multi *multi,
		       const uint8_t *data,
		       int size);

/*
 * Receive a payload through the TLS control channel
 */
bool tls_rec_payload (struct tls_multi *multi,
		      struct buffer *buf);

#ifdef MANAGEMENT_DEF_AUTH
static inline char *
tls_get_peer_info(const struct tls_multi *multi)
{
  return multi->peer_info;
}
#endif

/*
 * inline functions
 */

static inline bool
tls_initial_packet_received (const struct tls_multi *multi)
{
  return multi->n_sessions > 0;
}

static inline bool
tls_test_auth_deferred_interval (const struct tls_multi *multi)
{
  if (multi)
    {
      const struct key_state *ks = &multi->session[TM_ACTIVE].key[KS_PRIMARY];
      return now < ks->auth_deferred_expire;
    }
  return false;
}

static inline int
tls_test_payload_len (const struct tls_multi *multi)
{
  if (multi)
    {
      const struct key_state *ks = &multi->session[TM_ACTIVE].key[KS_PRIMARY];
      if (ks->state >= S_ACTIVE)
	return BLEN (&ks->plaintext_read_buf);
    }
  return 0;
}

static inline void
tls_set_single_session (struct tls_multi *multi)
{
  if (multi)
    multi->opt.single_session = true;
}

/*
 * protocol_dump() flags
 */
#define PD_TLS_AUTH_HMAC_SIZE_MASK 0xFF
#define PD_SHOW_DATA               (1<<8)
#define PD_TLS                     (1<<9)
#define PD_VERBOSE                 (1<<10)

const char *protocol_dump (struct buffer *buffer,
			   unsigned int flags,
			   struct gc_arena *gc);

/*
 * debugging code
 */

#ifdef MEASURE_TLS_HANDSHAKE_STATS
void show_tls_performance_stats(void);
#endif

/*#define EXTRACT_X509_FIELD_TEST*/
void extract_x509_field_test (void);

#endif /* ENABLE_CRYPTO && ENABLE_SSL */

#endif