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1 /*
2  * srtp.h
3  *
4  * interface to libsrtp
5  *
6  * David A. McGrew
7  * Cisco Systems, Inc.
8  */
9 /*
10  *
11  * Copyright (c) 2001-2017, Cisco Systems, Inc.
12  * All rights reserved.
13  *
14  * Redistribution and use in source and binary forms, with or without
15  * modification, are permitted provided that the following conditions
16  * are met:
17  *
18  *   Redistributions of source code must retain the above copyright
19  *   notice, this list of conditions and the following disclaimer.
20  *
21  *   Redistributions in binary form must reproduce the above
22  *   copyright notice, this list of conditions and the following
23  *   disclaimer in the documentation and/or other materials provided
24  *   with the distribution.
25  *
26  *   Neither the name of the Cisco Systems, Inc. nor the names of its
27  *   contributors may be used to endorse or promote products derived
28  *   from this software without specific prior written permission.
29  *
30  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
31  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
32  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
33  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
34  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
35  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
36  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
37  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
41  * OF THE POSSIBILITY OF SUCH DAMAGE.
42  *
43  */
44 
45 #ifndef SRTP_SRTP_H
46 #define SRTP_SRTP_H
47 
48 #include <stdint.h>
49 
50 #ifdef __cplusplus
51 extern "C" {
52 #endif
53 
54 /**
55  * @defgroup SRTP Secure RTP
56  *
57  * @brief libSRTP provides functions for protecting RTP and RTCP.  See
58  * Section @ref Overview for an introduction to the use of the library.
59  *
60  * @{
61  */
62 
63 /*
64  * SRTP_MASTER_KEY_LEN is the nominal master key length supported by libSRTP
65  */
66 
67 #define SRTP_MASTER_KEY_LEN 30
68 
69 /*
70  * SRTP_MAX_KEY_LEN is the maximum key length supported by libSRTP
71  */
72 #define SRTP_MAX_KEY_LEN 64
73 
74 /*
75  * SRTP_MAX_TAG_LEN is the maximum tag length supported by libSRTP
76  */
77 
78 #define SRTP_MAX_TAG_LEN 16
79 
80 /**
81  * SRTP_MAX_MKI_LEN is the maximum size the MKI could be which is
82  * 128 bytes
83  */
84 #define SRTP_MAX_MKI_LEN 128
85 
86 /**
87  * SRTP_MAX_TRAILER_LEN is the maximum length of the SRTP trailer
88  * (authentication tag and MKI) supported by libSRTP.  This value is
89  * the maixmum number of octets that will be added to an RTP packet by
90  * srtp_protect().
91  *
92  * @brief the maximum number of octets added by srtp_protect().
93  */
94 #define SRTP_MAX_TRAILER_LEN (SRTP_MAX_TAG_LEN + SRTP_MAX_MKI_LEN)
95 
96 /**
97  * SRTP_MAX_NUM_MASTER_KEYS is the maximum number of Master keys for
98  * MKI supported by libSRTP.
99  *
100  */
101 #define SRTP_MAX_NUM_MASTER_KEYS 16
102 
103 #define SRTP_SALT_LEN 14
104 
105 /*
106  * SRTP_AEAD_SALT_LEN is the length of the SALT values used with
107  * GCM mode.  GCM mode requires an IV.  The SALT value is used
108  * as part of the IV formation logic applied to each RTP packet.
109  */
110 #define SRTP_AEAD_SALT_LEN 12
111 
112 #define SRTP_AES_128_KEY_LEN 16
113 #define SRTP_AES_192_KEY_LEN 24
114 #define SRTP_AES_256_KEY_LEN 32
115 
116 #define SRTP_AES_ICM_128_KEY_LEN_WSALT (SRTP_SALT_LEN + SRTP_AES_128_KEY_LEN)
117 #define SRTP_AES_ICM_192_KEY_LEN_WSALT (SRTP_SALT_LEN + SRTP_AES_192_KEY_LEN)
118 #define SRTP_AES_ICM_256_KEY_LEN_WSALT (SRTP_SALT_LEN + SRTP_AES_256_KEY_LEN)
119 
120 #define SRTP_AES_GCM_128_KEY_LEN_WSALT                                         \
121     (SRTP_AEAD_SALT_LEN + SRTP_AES_128_KEY_LEN)
122 #define SRTP_AES_GCM_192_KEY_LEN_WSALT                                         \
123     (SRTP_AEAD_SALT_LEN + SRTP_AES_192_KEY_LEN)
124 #define SRTP_AES_GCM_256_KEY_LEN_WSALT                                         \
125     (SRTP_AEAD_SALT_LEN + SRTP_AES_256_KEY_LEN)
126 
127 /**
128  *  @brief A srtp_cipher_type_id_t is an identifier for a particular cipher
129  *  type.
130  *
131  *  A srtp_cipher_type_id_t is an integer that represents a particular
132  *  cipher type, e.g. the Advanced Encryption Standard (AES).  A
133  *  SRTP_NULL_CIPHER is avaliable; this cipher leaves the data unchanged,
134  *  and can be selected to indicate that no encryption is to take
135  *  place.
136  *
137  *  @ingroup Ciphers
138  */
139 typedef uint32_t srtp_cipher_type_id_t;
140 
141 /**
142  *  @brief An srtp_auth_type_id_t is an identifier for a particular
143  * authentication
144  *   function.
145  *
146  *  An srtp_auth_type_id_t is an integer that represents a particular
147  *  authentication function type, e.g. HMAC-SHA1.  A SRTP_NULL_AUTH is
148  *  avaliable; this authentication function performs no computation,
149  *  and can be selected to indicate that no authentication is to take
150  *  place.
151  *
152  *  @ingroup Authentication
153  */
154 typedef uint32_t srtp_auth_type_id_t;
155 
156 /**
157  * @brief srtp_err_status_t defines error codes.
158  *
159  * The enumeration srtp_err_status_t defines error codes.  Note that the
160  * value of srtp_err_status_ok is equal to zero, which can simplify error
161  * checking somewhat.
162  *
163  */
164 typedef enum {
165     srtp_err_status_ok = 0,             /**< nothing to report               */
166     srtp_err_status_fail = 1,           /**< unspecified failure             */
167     srtp_err_status_bad_param = 2,      /**< unsupported parameter           */
168     srtp_err_status_alloc_fail = 3,     /**< couldn't allocate memory        */
169     srtp_err_status_dealloc_fail = 4,   /**< couldn't deallocate properly    */
170     srtp_err_status_init_fail = 5,      /**< couldn't initialize             */
171     srtp_err_status_terminus = 6,       /**< can't process as much data as   */
172                                         /**< requested                       */
173     srtp_err_status_auth_fail = 7,      /**< authentication failure          */
174     srtp_err_status_cipher_fail = 8,    /**< cipher failure                  */
175     srtp_err_status_replay_fail = 9,    /**< replay check failed (bad index) */
176     srtp_err_status_replay_old = 10,    /**< replay check failed (index too  */
177                                         /**< old)                            */
178     srtp_err_status_algo_fail = 11,     /**< algorithm failed test routine   */
179     srtp_err_status_no_such_op = 12,    /**< unsupported operation           */
180     srtp_err_status_no_ctx = 13,        /**< no appropriate context found    */
181     srtp_err_status_cant_check = 14,    /**< unable to perform desired       */
182                                         /**< validation                      */
183     srtp_err_status_key_expired = 15,   /**< can't use key any more          */
184     srtp_err_status_socket_err = 16,    /**< error in use of socket          */
185     srtp_err_status_signal_err = 17,    /**< error in use POSIX signals      */
186     srtp_err_status_nonce_bad = 18,     /**< nonce check failed              */
187     srtp_err_status_read_fail = 19,     /**< couldn't read data              */
188     srtp_err_status_write_fail = 20,    /**< couldn't write data             */
189     srtp_err_status_parse_err = 21,     /**< error parsing data              */
190     srtp_err_status_encode_err = 22,    /**< error encoding data             */
191     srtp_err_status_semaphore_err = 23, /**< error while using semaphores    */
192     srtp_err_status_pfkey_err = 24,     /**< error while using pfkey         */
193     srtp_err_status_bad_mki = 25,       /**< error MKI present in packet is  */
194                                         /**< invalid                         */
195     srtp_err_status_pkt_idx_old = 26,   /**< packet index is too old to      */
196                                         /**< consider                        */
197     srtp_err_status_pkt_idx_adv = 27    /**< packet index advanced, reset    */
198                                         /**< needed                          */
199 } srtp_err_status_t;
200 
201 typedef struct srtp_ctx_t_ srtp_ctx_t;
202 
203 /**
204  * @brief srtp_sec_serv_t describes a set of security services.
205  *
206  * A srtp_sec_serv_t enumeration is used to describe the particular
207  * security services that will be applied by a particular crypto
208  * policy (or other mechanism).
209  */
210 typedef enum {
211     sec_serv_none = 0,         /**< no services                        */
212     sec_serv_conf = 1,         /**< confidentiality                    */
213     sec_serv_auth = 2,         /**< authentication                     */
214     sec_serv_conf_and_auth = 3 /**< confidentiality and authentication */
215 } srtp_sec_serv_t;
216 
217 /**
218  * @brief srtp_crypto_policy_t describes a particular crypto policy that
219  * can be applied to an SRTP stream.
220  *
221  * A srtp_crypto_policy_t describes a particular cryptographic policy that
222  * can be applied to an SRTP or SRTCP stream.  An SRTP session policy
223  * consists of a list of these policies, one for each SRTP stream
224  * in the session.
225  */
226 typedef struct srtp_crypto_policy_t {
227     srtp_cipher_type_id_t cipher_type; /**< An integer representing          */
228                                        /**< the type of cipher.              */
229     int cipher_key_len;                /**< The length of the cipher key     */
230                                        /**< in octets.                       */
231     srtp_auth_type_id_t auth_type;     /**< An integer representing the      */
232                                        /**< authentication function.         */
233     int auth_key_len;                  /**< The length of the authentication */
234                                        /**< function key in octets.          */
235     int auth_tag_len;                  /**< The length of the authentication */
236                                        /**< tag in octets.                   */
237     srtp_sec_serv_t sec_serv;          /**< The flag indicating the security */
238                                        /**< services to be applied.          */
239 } srtp_crypto_policy_t;
240 
241 /**
242  * @brief srtp_ssrc_type_t describes the type of an SSRC.
243  *
244  * An srtp_ssrc_type_t enumeration is used to indicate a type of SSRC.  See
245  * @ref srtp_policy_t for more informataion.
246  */
247 typedef enum {
248     ssrc_undefined = 0,   /**< Indicates an undefined SSRC type.    */
249     ssrc_specific = 1,    /**< Indicates a specific SSRC value      */
250     ssrc_any_inbound = 2, /**< Indicates any inbound SSRC value     */
251                           /**< (i.e. a value that is used in the    */
252                           /**< function srtp_unprotect())           */
253     ssrc_any_outbound = 3 /**< Indicates any outbound SSRC value    */
254                           /**< (i.e. a value that is used in the    */
255                           /**< function srtp_protect())             */
256 } srtp_ssrc_type_t;
257 
258 /**
259  * @brief An srtp_ssrc_t represents a particular SSRC value, or a `wildcard'
260  * SSRC.
261  *
262  * An srtp_ssrc_t represents a particular SSRC value (if its type is
263  * ssrc_specific), or a wildcard SSRC value that will match all
264  * outbound SSRCs (if its type is ssrc_any_outbound) or all inbound
265  * SSRCs (if its type is ssrc_any_inbound).
266  */
267 typedef struct {
268     srtp_ssrc_type_t type; /**< The type of this particular SSRC */
269     unsigned int value;    /**< The value of this SSRC, if it is not a */
270                            /**< wildcard */
271 } srtp_ssrc_t;
272 
273 /**
274  * @brief points to an EKT policy
275  */
276 typedef struct srtp_ekt_policy_ctx_t *srtp_ekt_policy_t;
277 
278 /**
279  * @brief points to EKT stream data
280  */
281 typedef struct srtp_ekt_stream_ctx_t *srtp_ekt_stream_t;
282 
283 /**
284  * @brief srtp_master_key_t represents a master key.  There will
285  * be a Master Key Index and the Master Key associated with the
286  * Master Key Index.  Need to also keep track of the Master Key
287  * Index Size to correctly read it from a packet.
288  */
289 typedef struct srtp_master_key_t {
290     unsigned char *key;
291     unsigned char *mki_id;
292     unsigned int mki_size;
293 } srtp_master_key_t;
294 
295 /**
296  * @brief represents the policy for an SRTP session.
297  *
298  * A single srtp_policy_t struct represents the policy for a single
299  * SRTP stream, and a linked list of these elements represents the
300  * policy for an entire SRTP session.  Each element contains the SRTP
301  * and SRTCP crypto policies for that stream, a pointer to the SRTP
302  * master key for that stream, the SSRC describing that stream, or a
303  * flag indicating a `wildcard' SSRC value, and a `next' field that
304  * holds a pointer to the next element in the list of policy elements,
305  * or NULL if it is the last element.
306  *
307  * The wildcard value SSRC_ANY_INBOUND matches any SSRC from an
308  * inbound stream that for which there is no explicit SSRC entry in
309  * another policy element.  Similarly, the value SSRC_ANY_OUTBOUND
310  * will matches any SSRC from an outbound stream that does not appear
311  * in another policy element.  Note that wildcard SSRCs &b cannot be
312  * used to match both inbound and outbound traffic.  This restriction
313  * is intentional, and it allows libSRTP to ensure that no security
314  * lapses result from accidental re-use of SSRC values during key
315  * sharing.
316  *
317  * @warning The final element of the list @b must have its `next' pointer
318  *          set to NULL.
319  */
320 
321 typedef struct srtp_policy_t {
322     srtp_ssrc_t ssrc;              /**< The SSRC value of stream, or the    */
323                                    /**< flags SSRC_ANY_INBOUND or           */
324                                    /**< SSRC_ANY_OUTBOUND if key sharing    */
325                                    /**< is used for this policy element.    */
326     srtp_crypto_policy_t rtp;      /**< SRTP crypto policy.                 */
327     srtp_crypto_policy_t rtcp;     /**< SRTCP crypto policy.                */
328     unsigned char *key;            /**< Pointer to the SRTP master key for  */
329                                    /**< this stream.                        */
330     srtp_master_key_t **keys;      /** Array of Master Key structures       */
331     unsigned long num_master_keys; /** Number of master keys                */
332     srtp_ekt_policy_t ekt;         /**< Pointer to the EKT policy structure */
333                                    /**< for this stream (if any)            */
334     unsigned long window_size;     /**< The window size to use for replay   */
335                                    /**< protection.                         */
336     int allow_repeat_tx;           /**< Whether retransmissions of          */
337                                    /**< packets with the same sequence      */
338                                    /**< number are allowed.                 */
339                                    /**< (Note that such repeated            */
340                                    /**< transmissions must have the same    */
341                                    /**< RTP payload, or a severe security   */
342                                    /**< weakness is introduced!)            */
343     int *enc_xtn_hdr;              /**< List of header ids to encrypt.      */
344     int enc_xtn_hdr_count;         /**< Number of entries in list of header */
345                                    /**<  ids.                               */
346     struct srtp_policy_t *next;    /**< Pointer to next stream policy.      */
347 } srtp_policy_t;
348 
349 /**
350  * @brief An srtp_t points to an SRTP session structure.
351  *
352  * The typedef srtp_t is a pointer to a structure that represents
353  * an SRTP session.  This datatype is intentially opaque in
354  * order to separate the interface from the implementation.
355  *
356  * An SRTP session consists of all of the traffic sent to the RTP and
357  * RTCP destination transport addresses, using the RTP/SAVP (Secure
358  * Audio/Video Profile).  A session can be viewed as a set of SRTP
359  * streams, each of which originates with a different participant.
360  */
361 typedef srtp_ctx_t *srtp_t;
362 
363 /**
364  * @brief srtp_init() initializes the srtp library.
365  *
366  * @warning This function @b must be called before any other srtp
367  * functions.
368  */
369 srtp_err_status_t srtp_init(void);
370 
371 /**
372  * @brief srtp_shutdown() de-initializes the srtp library.
373  *
374  * @warning No srtp functions may be called after calling this function.
375  */
376 srtp_err_status_t srtp_shutdown(void);
377 
378 /**
379  * @brief srtp_protect() is the Secure RTP sender-side packet processing
380  * function.
381  *
382  * The function call srtp_protect(ctx, rtp_hdr, len_ptr) applies SRTP
383  * protection to the RTP packet rtp_hdr (which has length *len_ptr) using
384  * the SRTP context ctx.  If srtp_err_status_ok is returned, then rtp_hdr
385  * points to the resulting SRTP packet and *len_ptr is the number of
386  * octets in that packet; otherwise, no assumptions should be made
387  * about the value of either data elements.
388  *
389  * The sequence numbers of the RTP packets presented to this function
390  * need not be consecutive, but they @b must be out of order by less
391  * than 2^15 = 32,768 packets.
392  *
393  * @warning This function assumes that it can write the authentication
394  * tag into the location in memory immediately following the RTP
395  * packet, and assumes that the RTP packet is aligned on a 32-bit
396  * boundary.
397  *
398  * @warning This function assumes that it can write SRTP_MAX_TRAILER_LEN
399  * into the location in memory immediately following the RTP packet.
400  * Callers MUST ensure that this much writable memory is available in
401  * the buffer that holds the RTP packet.
402  *
403  * @param ctx is the SRTP context to use in processing the packet.
404  *
405  * @param rtp_hdr is a pointer to the RTP packet (before the call); after
406  * the function returns, it points to the srtp packet.
407  *
408  * @param len_ptr is a pointer to the length in octets of the complete
409  * RTP packet (header and body) before the function call, and of the
410  * complete SRTP packet after the call, if srtp_err_status_ok was returned.
411  * Otherwise, the value of the data to which it points is undefined.
412  *
413  * @return
414  *    - srtp_err_status_ok            no problems
415  *    - srtp_err_status_replay_fail   rtp sequence number was non-increasing
416  *    - @e other                 failure in cryptographic mechanisms
417  */
418 srtp_err_status_t srtp_protect(srtp_t ctx, void *rtp_hdr, int *len_ptr);
419 
420 /**
421  * @brief srtp_protect_mki() is the Secure RTP sender-side packet processing
422  * function that can utilize MKI.
423  *
424  * The function call srtp_protect(ctx, rtp_hdr, len_ptr) applies SRTP
425  * protection to the RTP packet rtp_hdr (which has length *len_ptr) using
426  * the SRTP context ctx.  If srtp_err_status_ok is returned, then rtp_hdr
427  * points to the resulting SRTP packet and *len_ptr is the number of
428  * octets in that packet; otherwise, no assumptions should be made
429  * about the value of either data elements.
430  *
431  * The sequence numbers of the RTP packets presented to this function
432  * need not be consecutive, but they @b must be out of order by less
433  * than 2^15 = 32,768 packets.
434  *
435  * @warning This function assumes that it can write the authentication
436  * tag into the location in memory immediately following the RTP
437  * packet, and assumes that the RTP packet is aligned on a 32-bit
438  * boundary.
439  *
440  * @warning This function assumes that it can write SRTP_MAX_TRAILER_LEN
441  * into the location in memory immediately following the RTP packet.
442  * Callers MUST ensure that this much writable memory is available in
443  * the buffer that holds the RTP packet.
444  *
445  * @param ctx is the SRTP context to use in processing the packet.
446  *
447  * @param rtp_hdr is a pointer to the RTP packet (before the call); after
448  * the function returns, it points to the srtp packet.
449  *
450  * @param pkt_octet_len is a pointer to the length in octets of the complete
451  * RTP packet (header and body) before the function call, and of the
452  * complete SRTP packet after the call, if srtp_err_status_ok was returned.
453  * Otherwise, the value of the data to which it points is undefined.
454  *
455  * @param use_mki is a boolean to tell the system if mki is being used.  If
456  * set to false then will use the first set of session keys.  If set to true
457  * will
458  * use the session keys identified by the mki_index
459  *
460  * @param mki_index integer value specifying which set of session keys should be
461  * used if use_mki is set to true.
462  *
463  * @return
464  *    - srtp_err_status_ok            no problems
465  *    - srtp_err_status_replay_fail   rtp sequence number was non-increasing
466  *    - @e other                 failure in cryptographic mechanisms
467  */
468 srtp_err_status_t srtp_protect_mki(srtp_ctx_t *ctx,
469                                    void *rtp_hdr,
470                                    int *pkt_octet_len,
471                                    unsigned int use_mki,
472                                    unsigned int mki_index);
473 
474 /**
475  * @brief srtp_unprotect() is the Secure RTP receiver-side packet
476  * processing function.
477  *
478  * The function call srtp_unprotect(ctx, srtp_hdr, len_ptr) verifies
479  * the Secure RTP protection of the SRTP packet pointed to by srtp_hdr
480  * (which has length *len_ptr), using the SRTP context ctx.  If
481  * srtp_err_status_ok is returned, then srtp_hdr points to the resulting
482  * RTP packet and *len_ptr is the number of octets in that packet;
483  * otherwise, no assumptions should be made about the value of either
484  * data elements.
485  *
486  * The sequence numbers of the RTP packets presented to this function
487  * need not be consecutive, but they @b must be out of order by less
488  * than 2^15 = 32,768 packets.
489  *
490  * @warning This function assumes that the SRTP packet is aligned on a
491  * 32-bit boundary.
492  *
493  * @param ctx is the SRTP session which applies to the particular packet.
494  *
495  * @param srtp_hdr is a pointer to the header of the SRTP packet
496  * (before the call).  after the function returns, it points to the
497  * rtp packet if srtp_err_status_ok was returned; otherwise, the value of
498  * the data to which it points is undefined.
499  *
500  * @param len_ptr is a pointer to the length in octets of the complete
501  * srtp packet (header and body) before the function call, and of the
502  * complete rtp packet after the call, if srtp_err_status_ok was returned.
503  * Otherwise, the value of the data to which it points is undefined.
504  *
505  * @return
506  *    - srtp_err_status_ok          if the RTP packet is valid.
507  *    - srtp_err_status_auth_fail   if the SRTP packet failed the message
508  *                                  authentication check.
509  *    - srtp_err_status_replay_fail if the SRTP packet is a replay (e.g. packet
510  *                                  has already been processed and accepted).
511  *    - [other]  if there has been an error in the cryptographic mechanisms.
512  *
513  */
514 srtp_err_status_t srtp_unprotect(srtp_t ctx, void *srtp_hdr, int *len_ptr);
515 
516 /**
517  * @brief srtp_unprotect_mki() is the Secure RTP receiver-side packet
518  * processing function that checks for MKI.
519  *
520  * The function call srtp_unprotect(ctx, srtp_hdr, len_ptr) verifies
521  * the Secure RTP protection of the SRTP packet pointed to by srtp_hdr
522  * (which has length *len_ptr), using the SRTP context ctx.  If
523  * srtp_err_status_ok is returned, then srtp_hdr points to the resulting
524  * RTP packet and *len_ptr is the number of octets in that packet;
525  * otherwise, no assumptions should be made about the value of either
526  * data elements.
527  *
528  * The sequence numbers of the RTP packets presented to this function
529  * need not be consecutive, but they @b must be out of order by less
530  * than 2^15 = 32,768 packets.
531  *
532  * @warning This function assumes that the SRTP packet is aligned on a
533  * 32-bit boundary.
534  *
535  * @param ctx is the SRTP session which applies to the particular packet.
536  *
537  * @param srtp_hdr is a pointer to the header of the SRTP packet
538  * (before the call).  after the function returns, it points to the
539  * rtp packet if srtp_err_status_ok was returned; otherwise, the value of
540  * the data to which it points is undefined.
541  *
542  * @param len_ptr is a pointer to the length in octets of the complete
543  * srtp packet (header and body) before the function call, and of the
544  * complete rtp packet after the call, if srtp_err_status_ok was returned.
545  * Otherwise, the value of the data to which it points is undefined.
546  *
547  * @param use_mki is a boolean to tell the system if mki is being used.  If
548  * set to false then will use the first set of session keys.  If set to true
549  * will
550  * use the session keys identified by the mki_index
551  *
552  * @return
553  *    - srtp_err_status_ok          if the RTP packet is valid.
554  *    - srtp_err_status_auth_fail   if the SRTP packet failed the message
555  *                                  authentication check.
556  *    - srtp_err_status_replay_fail if the SRTP packet is a replay (e.g. packet
557  *                                  has already been processed and accepted).
558  *    - srtp_err_status_bad_mki if the MKI in the packet is not a known MKI id
559  *    - [other]  if there has been an error in the cryptographic mechanisms.
560  *
561  */
562 srtp_err_status_t srtp_unprotect_mki(srtp_t ctx,
563                                      void *srtp_hdr,
564                                      int *len_ptr,
565                                      unsigned int use_mki);
566 
567 /**
568  * @brief srtp_create() allocates and initializes an SRTP session.
569 
570  * The function call srtp_create(session, policy) allocates and
571  * initializes an SRTP session context, applying the given policy.
572  *
573  * @param session is a pointer to the SRTP session to which the policy is
574  * to be added.
575  *
576  * @param policy is the srtp_policy_t struct that describes the policy
577  * for the session.  The struct may be a single element, or it may be
578  * the head of a list, in which case each element of the list is
579  * processed.  It may also be NULL, in which case streams should be added
580  * later using srtp_add_stream().  The final element of the list @b must
581  * have its `next' field set to NULL.
582  *
583  * @return
584  *    - srtp_err_status_ok           if creation succeded.
585  *    - srtp_err_status_alloc_fail   if allocation failed.
586  *    - srtp_err_status_init_fail    if initialization failed.
587  */
588 srtp_err_status_t srtp_create(srtp_t *session, const srtp_policy_t *policy);
589 
590 /**
591  * @brief srtp_add_stream() allocates and initializes an SRTP stream
592  * within a given SRTP session.
593  *
594  * The function call srtp_add_stream(session, policy) allocates and
595  * initializes a new SRTP stream within a given, previously created
596  * session, applying the policy given as the other argument to that
597  * stream.
598  *
599  * @return values:
600  *    - srtp_err_status_ok           if stream creation succeded.
601  *    - srtp_err_status_alloc_fail   if stream allocation failed
602  *    - srtp_err_status_init_fail    if stream initialization failed.
603  */
604 srtp_err_status_t srtp_add_stream(srtp_t session, const srtp_policy_t *policy);
605 
606 /**
607  * @brief srtp_remove_stream() deallocates an SRTP stream.
608  *
609  * The function call srtp_remove_stream(session, ssrc) removes
610  * the SRTP stream with the SSRC value ssrc from the SRTP session
611  * context given by the argument session.
612  *
613  * @param session is the SRTP session from which the stream
614  *        will be removed.
615  *
616  * @param ssrc is the SSRC value of the stream to be removed
617  *             in network byte order.
618  *
619  * @warning Wildcard SSRC values cannot be removed from a
620  *          session.
621  *
622  * @return
623  *    - srtp_err_status_ok     if the stream deallocation succeded.
624  *    - [other]           otherwise.
625  *
626  */
627 srtp_err_status_t srtp_remove_stream(srtp_t session, unsigned int ssrc);
628 
629 /**
630  * @brief srtp_update() udpates all streams in the session.
631  *
632  * The function call srtp_update(session, policy) updates
633  * all the streams in the session applying the given policy
634  * and key. The exsisting ROC value of all streams will be
635  * preserved.
636  *
637  * @param session is the SRTP session that contains the streams
638  *        to be updated.
639  *
640  * @param policy is the srtp_policy_t struct that describes the policy
641  * for the session.  The struct may be a single element, or it may be
642  * the head of a list, in which case each element of the list is
643  * processed. The final element of the list @b must
644  * have its `next' field set to NULL.
645  *
646  * @return
647  *    - srtp_err_status_ok           if stream creation succeded.
648  *    - srtp_err_status_alloc_fail   if stream allocation failed
649  *    - srtp_err_status_init_fail    if stream initialization failed.
650  *    - [other]                 otherwise.
651  *
652  */
653 srtp_err_status_t srtp_update(srtp_t session, const srtp_policy_t *policy);
654 
655 /**
656  * @brief srtp_update_stream() udpates a SRTP stream.
657  *
658  * The function call srtp_update_stream(session, policy) updates
659  * the stream(s) in the session that match applying the given
660  * policy and key. The exsisting ROC value of all stream(s) will
661  * be preserved.
662  *
663  * @param session is the SRTP session that contains the streams
664  *        to be updated.
665  *
666  * @param policy is the srtp_policy_t struct that describes the policy
667  * for the session.
668  *
669  * @return
670  *    - srtp_err_status_ok           if stream creation succeded.
671  *    - srtp_err_status_alloc_fail   if stream allocation failed
672  *    - srtp_err_status_init_fail    if stream initialization failed.
673  *    - [other]                      otherwise.
674  *
675  */
676 srtp_err_status_t srtp_update_stream(srtp_t session,
677                                      const srtp_policy_t *policy);
678 
679 /**
680  * @brief srtp_crypto_policy_set_rtp_default() sets a crypto policy
681  * structure to the SRTP default policy for RTP protection.
682  *
683  * @param p is a pointer to the policy structure to be set
684  *
685  * The function call srtp_crypto_policy_set_rtp_default(&p) sets the
686  * srtp_crypto_policy_t at location p to the SRTP default policy for RTP
687  * protection, as defined in the specification.  This function is a
688  * convenience that helps to avoid dealing directly with the policy
689  * data structure.  You are encouraged to initialize policy elements
690  * with this function call.  Doing so may allow your code to be
691  * forward compatible with later versions of libSRTP that include more
692  * elements in the srtp_crypto_policy_t datatype.
693  *
694  * @return void.
695  *
696  */
697 void srtp_crypto_policy_set_rtp_default(srtp_crypto_policy_t *p);
698 
699 /**
700  * @brief srtp_crypto_policy_set_rtcp_default() sets a crypto policy
701  * structure to the SRTP default policy for RTCP protection.
702  *
703  * @param p is a pointer to the policy structure to be set
704  *
705  * The function call srtp_crypto_policy_set_rtcp_default(&p) sets the
706  * srtp_crypto_policy_t at location p to the SRTP default policy for RTCP
707  * protection, as defined in the specification.  This function is a
708  * convenience that helps to avoid dealing directly with the policy
709  * data structure.  You are encouraged to initialize policy elements
710  * with this function call.  Doing so may allow your code to be
711  * forward compatible with later versions of libSRTP that include more
712  * elements in the srtp_crypto_policy_t datatype.
713  *
714  * @return void.
715  *
716  */
717 void srtp_crypto_policy_set_rtcp_default(srtp_crypto_policy_t *p);
718 
719 /**
720  * @brief srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80() sets a crypto
721  * policy structure to the SRTP default policy for RTP protection.
722  *
723  * @param p is a pointer to the policy structure to be set
724  *
725  * The function srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80() is a
726  * synonym for srtp_crypto_policy_set_rtp_default().  It conforms to the
727  * naming convention used in RFC 4568 (SDP Security Descriptions for
728  * Media Streams).
729  *
730  * @return void.
731  *
732  */
733 #define srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(p)                      \
734     srtp_crypto_policy_set_rtp_default(p)
735 
736 /**
737  * @brief srtp_crypto_policy_set_aes_cm_128_hmac_sha1_32() sets a crypto
738  * policy structure to a short-authentication tag policy
739  *
740  * @param p is a pointer to the policy structure to be set
741  *
742  * The function call srtp_crypto_policy_set_aes_cm_128_hmac_sha1_32(&p)
743  * sets the srtp_crypto_policy_t at location p to use policy
744  * AES_CM_128_HMAC_SHA1_32 as defined in RFC 4568.
745  * This policy uses AES-128
746  * Counter Mode encryption and HMAC-SHA1 authentication, with an
747  * authentication tag that is only 32 bits long.  This length is
748  * considered adequate only for protecting audio and video media that
749  * use a stateless playback function.  See Section 7.5 of RFC 3711
750  * (http://www.ietf.org/rfc/rfc3711.txt).
751  *
752  * This function is a convenience that helps to avoid dealing directly
753  * with the policy data structure.  You are encouraged to initialize
754  * policy elements with this function call.  Doing so may allow your
755  * code to be forward compatible with later versions of libSRTP that
756  * include more elements in the srtp_crypto_policy_t datatype.
757  *
758  * @warning This crypto policy is intended for use in SRTP, but not in
759  * SRTCP.  It is recommended that a policy that uses longer
760  * authentication tags be used for SRTCP.  See Section 7.5 of RFC 3711
761  * (http://www.ietf.org/rfc/rfc3711.txt).
762  *
763  * @return void.
764  *
765  */
766 void srtp_crypto_policy_set_aes_cm_128_hmac_sha1_32(srtp_crypto_policy_t *p);
767 
768 /**
769  * @brief srtp_crypto_policy_set_aes_cm_128_null_auth() sets a crypto
770  * policy structure to an encryption-only policy
771  *
772  * @param p is a pointer to the policy structure to be set
773  *
774  * The function call srtp_crypto_policy_set_aes_cm_128_null_auth(&p) sets
775  * the srtp_crypto_policy_t at location p to use the SRTP default cipher
776  * (AES-128 Counter Mode), but to use no authentication method.  This
777  * policy is NOT RECOMMENDED unless it is unavoidable; see Section 7.5
778  * of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
779  *
780  * This function is a convenience that helps to avoid dealing directly
781  * with the policy data structure.  You are encouraged to initialize
782  * policy elements with this function call.  Doing so may allow your
783  * code to be forward compatible with later versions of libSRTP that
784  * include more elements in the srtp_crypto_policy_t datatype.
785  *
786  * @warning This policy is NOT RECOMMENDED for SRTP unless it is
787  * unavoidable, and it is NOT RECOMMENDED at all for SRTCP; see
788  * Section 7.5 of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
789  *
790  * @return void.
791  *
792  */
793 void srtp_crypto_policy_set_aes_cm_128_null_auth(srtp_crypto_policy_t *p);
794 
795 /**
796  * @brief srtp_crypto_policy_set_null_cipher_hmac_sha1_80() sets a crypto
797  * policy structure to an authentication-only policy
798  *
799  * @param p is a pointer to the policy structure to be set
800  *
801  * The function call srtp_crypto_policy_set_null_cipher_hmac_sha1_80(&p)
802  * sets the srtp_crypto_policy_t at location p to use HMAC-SHA1 with an 80
803  * bit authentication tag to provide message authentication, but to
804  * use no encryption.  This policy is NOT RECOMMENDED for SRTP unless
805  * there is a requirement to forego encryption.
806  *
807  * This function is a convenience that helps to avoid dealing directly
808  * with the policy data structure.  You are encouraged to initialize
809  * policy elements with this function call.  Doing so may allow your
810  * code to be forward compatible with later versions of libSRTP that
811  * include more elements in the srtp_crypto_policy_t datatype.
812  *
813  * @warning This policy is NOT RECOMMENDED for SRTP unless there is a
814  * requirement to forego encryption.
815  *
816  * @return void.
817  *
818  */
819 void srtp_crypto_policy_set_null_cipher_hmac_sha1_80(srtp_crypto_policy_t *p);
820 
821 /**
822  * @brief srtp_crypto_policy_set_null_cipher_hmac_null() sets a crypto
823  * policy structure to use no encryption or authentication.
824  *
825  * @param p is a pointer to the policy structure to be set
826  *
827  * The function call srtp_crypto_policy_set_null_cipher_hmac_null(&p)
828  * sets the srtp_crypto_policy_t at location p to use no encryption and
829  * no authentication.  This policy should only be used for testing and
830  * troubleshootingl.
831  *
832  * This function is a convenience that helps to avoid dealing directly
833  * with the policy data structure.  You are encouraged to initialize
834  * policy elements with this function call.  Doing so may allow your
835  * code to be forward compatible with later versions of libSRTP that
836  * include more elements in the srtp_crypto_policy_t datatype.
837  *
838  * @warning This policy is NOT RECOMMENDED for SRTP unless there is a
839  * requirement to forego encryption and authentication.
840  *
841  * @return void.
842  *
843  */
844 void srtp_crypto_policy_set_null_cipher_hmac_null(srtp_crypto_policy_t *p);
845 
846 /**
847  * @brief srtp_crypto_policy_set_aes_cm_256_hmac_sha1_80() sets a crypto
848  * policy structure to a encryption and authentication policy using AES-256
849  * for RTP protection.
850  *
851  * @param p is a pointer to the policy structure to be set
852  *
853  * The function call srtp_crypto_policy_set_aes_cm_256_hmac_sha1_80(&p)
854  * sets the srtp_crypto_policy_t at location p to use policy
855  * AES_CM_256_HMAC_SHA1_80 as defined in RFC 6188.  This policy uses AES-256
856  * Counter Mode encryption and HMAC-SHA1 authentication, with an 80 bit
857  * authentication tag.
858  *
859  * This function is a convenience that helps to avoid dealing directly
860  * with the policy data structure.  You are encouraged to initialize
861  * policy elements with this function call.  Doing so may allow your
862  * code to be forward compatible with later versions of libSRTP that
863  * include more elements in the srtp_crypto_policy_t datatype.
864  *
865  * @return void.
866  *
867  */
868 void srtp_crypto_policy_set_aes_cm_256_hmac_sha1_80(srtp_crypto_policy_t *p);
869 
870 /**
871  * @brief srtp_crypto_policy_set_aes_cm_256_hmac_sha1_32() sets a crypto
872  * policy structure to a short-authentication tag policy using AES-256
873  * encryption.
874  *
875  * @param p is a pointer to the policy structure to be set
876  *
877  * The function call srtp_crypto_policy_set_aes_cm_256_hmac_sha1_32(&p)
878  * sets the srtp_crypto_policy_t at location p to use policy
879  * AES_CM_256_HMAC_SHA1_32 as defined in RFC 6188.  This policy uses AES-256
880  * Counter Mode encryption and HMAC-SHA1 authentication, with an
881  * authentication tag that is only 32 bits long.  This length is
882  * considered adequate only for protecting audio and video media that
883  * use a stateless playback function.  See Section 7.5 of RFC 3711
884  * (http://www.ietf.org/rfc/rfc3711.txt).
885  *
886  * This function is a convenience that helps to avoid dealing directly
887  * with the policy data structure.  You are encouraged to initialize
888  * policy elements with this function call.  Doing so may allow your
889  * code to be forward compatible with later versions of libSRTP that
890  * include more elements in the srtp_crypto_policy_t datatype.
891  *
892  * @warning This crypto policy is intended for use in SRTP, but not in
893  * SRTCP.  It is recommended that a policy that uses longer
894  * authentication tags be used for SRTCP.  See Section 7.5 of RFC 3711
895  * (http://www.ietf.org/rfc/rfc3711.txt).
896  *
897  * @return void.
898  *
899  */
900 void srtp_crypto_policy_set_aes_cm_256_hmac_sha1_32(srtp_crypto_policy_t *p);
901 
902 /**
903  * @brief srtp_crypto_policy_set_aes_cm_256_null_auth() sets a crypto
904  * policy structure to an encryption-only policy
905  *
906  * @param p is a pointer to the policy structure to be set
907  *
908  * The function call srtp_crypto_policy_set_aes_cm_256_null_auth(&p) sets
909  * the srtp_crypto_policy_t at location p to use the SRTP default cipher
910  * (AES-256 Counter Mode), but to use no authentication method.  This
911  * policy is NOT RECOMMENDED unless it is unavoidable; see Section 7.5
912  * of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
913  *
914  * This function is a convenience that helps to avoid dealing directly
915  * with the policy data structure.  You are encouraged to initialize
916  * policy elements with this function call.  Doing so may allow your
917  * code to be forward compatible with later versions of libSRTP that
918  * include more elements in the srtp_crypto_policy_t datatype.
919  *
920  * @warning This policy is NOT RECOMMENDED for SRTP unless it is
921  * unavoidable, and it is NOT RECOMMENDED at all for SRTCP; see
922  * Section 7.5 of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
923  *
924  * @return void.
925  *
926  */
927 void srtp_crypto_policy_set_aes_cm_256_null_auth(srtp_crypto_policy_t *p);
928 
929 /**
930  * @brief srtp_crypto_policy_set_aes_cm_192_hmac_sha1_80() sets a crypto
931  * policy structure to a encryption and authentication policy using AES-192
932  * for RTP protection.
933  *
934  * @param p is a pointer to the policy structure to be set
935  *
936  * The function call srtp_crypto_policy_set_aes_cm_192_hmac_sha1_80(&p)
937  * sets the srtp_crypto_policy_t at location p to use policy
938  * AES_CM_192_HMAC_SHA1_80 as defined in RFC 6188.  This policy uses AES-192
939  * Counter Mode encryption and HMAC-SHA1 authentication, with an 80 bit
940  * authentication tag.
941  *
942  * This function is a convenience that helps to avoid dealing directly
943  * with the policy data structure.  You are encouraged to initialize
944  * policy elements with this function call.  Doing so may allow your
945  * code to be forward compatible with later versions of libSRTP that
946  * include more elements in the srtp_crypto_policy_t datatype.
947  *
948  * @return void.
949  *
950  */
951 void srtp_crypto_policy_set_aes_cm_192_hmac_sha1_80(srtp_crypto_policy_t *p);
952 
953 /**
954  * @brief srtp_crypto_policy_set_aes_cm_192_hmac_sha1_32() sets a crypto
955  * policy structure to a short-authentication tag policy using AES-192
956  * encryption.
957  *
958  * @param p is a pointer to the policy structure to be set
959  *
960  * The function call srtp_crypto_policy_set_aes_cm_192_hmac_sha1_32(&p)
961  * sets the srtp_crypto_policy_t at location p to use policy
962  * AES_CM_192_HMAC_SHA1_32 as defined in RFC 6188.  This policy uses AES-192
963  * Counter Mode encryption and HMAC-SHA1 authentication, with an
964  * authentication tag that is only 32 bits long.  This length is
965  * considered adequate only for protecting audio and video media that
966  * use a stateless playback function.  See Section 7.5 of RFC 3711
967  * (http://www.ietf.org/rfc/rfc3711.txt).
968  *
969  * This function is a convenience that helps to avoid dealing directly
970  * with the policy data structure.  You are encouraged to initialize
971  * policy elements with this function call.  Doing so may allow your
972  * code to be forward compatible with later versions of libSRTP that
973  * include more elements in the srtp_crypto_policy_t datatype.
974  *
975  * @warning This crypto policy is intended for use in SRTP, but not in
976  * SRTCP.  It is recommended that a policy that uses longer
977  * authentication tags be used for SRTCP.  See Section 7.5 of RFC 3711
978  * (http://www.ietf.org/rfc/rfc3711.txt).
979  *
980  * @return void.
981  *
982  */
983 void srtp_crypto_policy_set_aes_cm_192_hmac_sha1_32(srtp_crypto_policy_t *p);
984 
985 /**
986  * @brief srtp_crypto_policy_set_aes_cm_192_null_auth() sets a crypto
987  * policy structure to an encryption-only policy
988  *
989  * @param p is a pointer to the policy structure to be set
990  *
991  * The function call srtp_crypto_policy_set_aes_cm_192_null_auth(&p) sets
992  * the srtp_crypto_policy_t at location p to use the SRTP default cipher
993  * (AES-192 Counter Mode), but to use no authentication method.  This
994  * policy is NOT RECOMMENDED unless it is unavoidable; see Section 7.5
995  * of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
996  *
997  * This function is a convenience that helps to avoid dealing directly
998  * with the policy data structure.  You are encouraged to initialize
999  * policy elements with this function call.  Doing so may allow your
1000  * code to be forward compatible with later versions of libSRTP that
1001  * include more elements in the srtp_crypto_policy_t datatype.
1002  *
1003  * @warning This policy is NOT RECOMMENDED for SRTP unless it is
1004  * unavoidable, and it is NOT RECOMMENDED at all for SRTCP; see
1005  * Section 7.5 of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
1006  *
1007  * @return void.
1008  *
1009  */
1010 void srtp_crypto_policy_set_aes_cm_192_null_auth(srtp_crypto_policy_t *p);
1011 
1012 /**
1013  * @brief srtp_crypto_policy_set_aes_gcm_128_8_auth() sets a crypto
1014  * policy structure to an AEAD encryption policy.
1015  *
1016  * @param p is a pointer to the policy structure to be set
1017  *
1018  * The function call srtp_crypto_policy_set_aes_gcm_128_8_auth(&p) sets
1019  * the srtp_crypto_policy_t at location p to use the SRTP default cipher
1020  * (AES-128 Galois Counter Mode) with 8 octet auth tag.  This
1021  * policy applies confidentiality and authentication to both the
1022  * RTP and RTCP packets.
1023  *
1024  * This function is a convenience that helps to avoid dealing directly
1025  * with the policy data structure.  You are encouraged to initialize
1026  * policy elements with this function call.  Doing so may allow your
1027  * code to be forward compatible with later versions of libSRTP that
1028  * include more elements in the srtp_crypto_policy_t datatype.
1029  *
1030  * @return void.
1031  *
1032  */
1033 void srtp_crypto_policy_set_aes_gcm_128_8_auth(srtp_crypto_policy_t *p);
1034 
1035 /**
1036  * @brief srtp_crypto_policy_set_aes_gcm_256_8_auth() sets a crypto
1037  * policy structure to an AEAD encryption policy
1038  *
1039  * @param p is a pointer to the policy structure to be set
1040  *
1041  * The function call srtp_crypto_policy_set_aes_gcm_256_8_auth(&p) sets
1042  * the srtp_crypto_policy_t at location p to use the SRTP default cipher
1043  * (AES-256 Galois Counter Mode) with 8 octet auth tag.  This
1044  * policy applies confidentiality and authentication to both the
1045  * RTP and RTCP packets.
1046  *
1047  * This function is a convenience that helps to avoid dealing directly
1048  * with the policy data structure.  You are encouraged to initialize
1049  * policy elements with this function call.  Doing so may allow your
1050  * code to be forward compatible with later versions of libSRTP that
1051  * include more elements in the srtp_crypto_policy_t datatype.
1052  *
1053  * @return void.
1054  *
1055  */
1056 void srtp_crypto_policy_set_aes_gcm_256_8_auth(srtp_crypto_policy_t *p);
1057 
1058 /**
1059  * @brief srtp_crypto_policy_set_aes_gcm_128_8_only_auth() sets a crypto
1060  * policy structure to an AEAD authentication-only policy
1061  *
1062  * @param p is a pointer to the policy structure to be set
1063  *
1064  * The function call srtp_crypto_policy_set_aes_gcm_128_8_only_auth(&p) sets
1065  * the srtp_crypto_policy_t at location p to use the SRTP default cipher
1066  * (AES-128 Galois Counter Mode) with 8 octet auth tag.  This policy
1067  * applies confidentiality and authentication to the RTP packets,
1068  * but only authentication to the RTCP packets.
1069  *
1070  * This function is a convenience that helps to avoid dealing directly
1071  * with the policy data structure.  You are encouraged to initialize
1072  * policy elements with this function call.  Doing so may allow your
1073  * code to be forward compatible with later versions of libSRTP that
1074  * include more elements in the srtp_crypto_policy_t datatype.
1075  *
1076  * @return void.
1077  *
1078  */
1079 void srtp_crypto_policy_set_aes_gcm_128_8_only_auth(srtp_crypto_policy_t *p);
1080 
1081 /**
1082  * @brief srtp_crypto_policy_set_aes_gcm_256_8_only_auth() sets a crypto
1083  * policy structure to an AEAD authentication-only policy
1084  *
1085  * @param p is a pointer to the policy structure to be set
1086  *
1087  * The function call srtp_crypto_policy_set_aes_gcm_256_8_only_auth(&p) sets
1088  * the srtp_crypto_policy_t at location p to use the SRTP default cipher
1089  * (AES-256 Galois Counter Mode) with 8 octet auth tag.  This policy
1090  * applies confidentiality and authentication to the RTP packets,
1091  * but only authentication to the RTCP packets.
1092  *
1093  * This function is a convenience that helps to avoid dealing directly
1094  * with the policy data structure.  You are encouraged to initialize
1095  * policy elements with this function call.  Doing so may allow your
1096  * code to be forward compatible with later versions of libSRTP that
1097  * include more elements in the srtp_crypto_policy_t datatype.
1098  *
1099  * @return void.
1100  *
1101  */
1102 void srtp_crypto_policy_set_aes_gcm_256_8_only_auth(srtp_crypto_policy_t *p);
1103 
1104 /**
1105  * @brief srtp_crypto_policy_set_aes_gcm_128_16_auth() sets a crypto
1106  * policy structure to an AEAD encryption policy.
1107  *
1108  * @param p is a pointer to the policy structure to be set
1109  *
1110  * The function call srtp_crypto_policy_set_aes_gcm_128_16_auth(&p) sets
1111  * the srtp_crypto_policy_t at location p to use the SRTP default cipher
1112  * (AES-128 Galois Counter Mode) with 16 octet auth tag.  This
1113  * policy applies confidentiality and authentication to both the
1114  * RTP and RTCP packets.
1115  *
1116  * This function is a convenience that helps to avoid dealing directly
1117  * with the policy data structure.  You are encouraged to initialize
1118  * policy elements with this function call.  Doing so may allow your
1119  * code to be forward compatible with later versions of libSRTP that
1120  * include more elements in the srtp_crypto_policy_t datatype.
1121  *
1122  * @return void.
1123  *
1124  */
1125 void srtp_crypto_policy_set_aes_gcm_128_16_auth(srtp_crypto_policy_t *p);
1126 
1127 /**
1128  * @brief srtp_crypto_policy_set_aes_gcm_256_16_auth() sets a crypto
1129  * policy structure to an AEAD encryption policy
1130  *
1131  * @param p is a pointer to the policy structure to be set
1132  *
1133  * The function call srtp_crypto_policy_set_aes_gcm_256_16_auth(&p) sets
1134  * the srtp_crypto_policy_t at location p to use the SRTP default cipher
1135  * (AES-256 Galois Counter Mode) with 16 octet auth tag.  This
1136  * policy applies confidentiality and authentication to both the
1137  * RTP and RTCP packets.
1138  *
1139  * This function is a convenience that helps to avoid dealing directly
1140  * with the policy data structure.  You are encouraged to initialize
1141  * policy elements with this function call.  Doing so may allow your
1142  * code to be forward compatible with later versions of libSRTP that
1143  * include more elements in the srtp_crypto_policy_t datatype.
1144  *
1145  * @return void.
1146  *
1147  */
1148 void srtp_crypto_policy_set_aes_gcm_256_16_auth(srtp_crypto_policy_t *p);
1149 
1150 /**
1151  * @brief srtp_dealloc() deallocates storage for an SRTP session
1152  * context.
1153  *
1154  * The function call srtp_dealloc(s) deallocates storage for the
1155  * SRTP session context s.  This function should be called no more
1156  * than one time for each of the contexts allocated by the function
1157  * srtp_create().
1158  *
1159  * @param s is the srtp_t for the session to be deallocated.
1160  *
1161  * @return
1162  *    - srtp_err_status_ok             if there no problems.
1163  *    - srtp_err_status_dealloc_fail   a memory deallocation failure occured.
1164  */
1165 srtp_err_status_t srtp_dealloc(srtp_t s);
1166 
1167 /*
1168  * @brief identifies a particular SRTP profile
1169  *
1170  * An srtp_profile_t enumeration is used to identify a particular SRTP
1171  * profile (that is, a set of algorithms and parameters). These profiles
1172  * are defined for DTLS-SRTP:
1173  * https://www.iana.org/assignments/srtp-protection/srtp-protection.xhtml
1174  */
1175 typedef enum {
1176     srtp_profile_reserved = 0,
1177     srtp_profile_aes128_cm_sha1_80 = 1,
1178     srtp_profile_aes128_cm_sha1_32 = 2,
1179     srtp_profile_null_sha1_80 = 5,
1180     srtp_profile_null_sha1_32 = 6,
1181     srtp_profile_aead_aes_128_gcm = 7,
1182     srtp_profile_aead_aes_256_gcm = 8,
1183 } srtp_profile_t;
1184 
1185 /**
1186  * @brief srtp_crypto_policy_set_from_profile_for_rtp() sets a crypto policy
1187  * structure to the appropriate value for RTP based on an srtp_profile_t
1188  *
1189  * @param policy is a pointer to the policy structure to be set
1190  *
1191  * @param profile is an enumeration for the policy to be set
1192  *
1193  * The function call srtp_crypto_policy_set_rtp_default(&policy, profile)
1194  * sets the srtp_crypto_policy_t at location policy to the policy for RTP
1195  * protection, as defined by the srtp_profile_t profile.
1196  *
1197  * This function is a convenience that helps to avoid dealing directly
1198  * with the policy data structure.  You are encouraged to initialize
1199  * policy elements with this function call.  Doing so may allow your
1200  * code to be forward compatible with later versions of libSRTP that
1201  * include more elements in the srtp_crypto_policy_t datatype.
1202  *
1203  * @return values
1204  *     - srtp_err_status_ok         no problems were encountered
1205  *     - srtp_err_status_bad_param  the profile is not supported
1206  *
1207  */
1208 srtp_err_status_t srtp_crypto_policy_set_from_profile_for_rtp(
1209     srtp_crypto_policy_t *policy,
1210     srtp_profile_t profile);
1211 
1212 /**
1213  * @brief srtp_crypto_policy_set_from_profile_for_rtcp() sets a crypto policy
1214  * structure to the appropriate value for RTCP based on an srtp_profile_t
1215  *
1216  * @param policy is a pointer to the policy structure to be set
1217  *
1218  * @param profile is an enumeration for the policy to be set
1219  *
1220  * The function call srtp_crypto_policy_set_rtcp_default(&policy, profile)
1221  * sets the srtp_crypto_policy_t at location policy to the policy for RTCP
1222  * protection, as defined by the srtp_profile_t profile.
1223  *
1224  * This function is a convenience that helps to avoid dealing directly
1225  * with the policy data structure.  You are encouraged to initialize
1226  * policy elements with this function call.  Doing so may allow your
1227  * code to be forward compatible with later versions of libSRTP that
1228  * include more elements in the srtp_crypto_policy_t datatype.
1229  *
1230  * @return values
1231  *     - srtp_err_status_ok         no problems were encountered
1232  *     - srtp_err_status_bad_param  the profile is not supported
1233  *
1234  */
1235 srtp_err_status_t srtp_crypto_policy_set_from_profile_for_rtcp(
1236     srtp_crypto_policy_t *policy,
1237     srtp_profile_t profile);
1238 
1239 /**
1240  * @brief returns the master key length for a given SRTP profile
1241  */
1242 unsigned int srtp_profile_get_master_key_length(srtp_profile_t profile);
1243 
1244 /**
1245  * @brief returns the master salt length for a given SRTP profile
1246  */
1247 unsigned int srtp_profile_get_master_salt_length(srtp_profile_t profile);
1248 
1249 /**
1250  * @brief appends the salt to the key
1251  *
1252  * The function call srtp_append_salt_to_key(k, klen, s, slen)
1253  * copies the string s to the location at klen bytes following
1254  * the location k.
1255  *
1256  * @warning There must be at least bytes_in_salt + bytes_in_key bytes
1257  *          available at the location pointed to by key.
1258  *
1259  */
1260 void srtp_append_salt_to_key(unsigned char *key,
1261                              unsigned int bytes_in_key,
1262                              unsigned char *salt,
1263                              unsigned int bytes_in_salt);
1264 
1265 /**
1266  * @}
1267  */
1268 
1269 /**
1270  * @defgroup SRTCP Secure RTCP
1271  * @ingroup  SRTP
1272  *
1273  * @brief Secure RTCP functions are used to protect RTCP traffic.
1274  *
1275  * RTCP is the control protocol for RTP.  libSRTP protects RTCP
1276  * traffic in much the same way as it does RTP traffic.  The function
1277  * srtp_protect_rtcp() applies cryptographic protections to outbound
1278  * RTCP packets, and srtp_unprotect_rtcp() verifies the protections on
1279  * inbound RTCP packets.
1280  *
1281  * A note on the naming convention: srtp_protect_rtcp() has an srtp_t
1282  * as its first argument, and thus has `srtp_' as its prefix.  The
1283  * trailing `_rtcp' indicates the protocol on which it acts.
1284  *
1285  * @{
1286  */
1287 
1288 /**
1289  * @brief srtp_protect_rtcp() is the Secure RTCP sender-side packet
1290  * processing function.
1291  *
1292  * The function call srtp_protect_rtcp(ctx, rtp_hdr, len_ptr) applies
1293  * SRTCP protection to the RTCP packet rtcp_hdr (which has length
1294  * *len_ptr) using the SRTP session context ctx.  If srtp_err_status_ok is
1295  * returned, then rtp_hdr points to the resulting SRTCP packet and
1296  * *len_ptr is the number of octets in that packet; otherwise, no
1297  * assumptions should be made about the value of either data elements.
1298  *
1299  * @warning This function assumes that it can write the authentication
1300  * tag into the location in memory immediately following the RTCP
1301  * packet, and assumes that the RTCP packet is aligned on a 32-bit
1302  * boundary.
1303  *
1304  * @warning This function assumes that it can write SRTP_MAX_TRAILER_LEN+4
1305  * into the location in memory immediately following the RTCP packet.
1306  * Callers MUST ensure that this much writable memory is available in
1307  * the buffer that holds the RTCP packet.
1308  *
1309  * @param ctx is the SRTP context to use in processing the packet.
1310  *
1311  * @param rtcp_hdr is a pointer to the RTCP packet (before the call); after
1312  * the function returns, it points to the srtp packet.
1313  *
1314  * @param pkt_octet_len is a pointer to the length in octets of the
1315  * complete RTCP packet (header and body) before the function call,
1316  * and of the complete SRTCP packet after the call, if srtp_err_status_ok
1317  * was returned.  Otherwise, the value of the data to which it points
1318  * is undefined.
1319  *
1320  * @return
1321  *    - srtp_err_status_ok            if there were no problems.
1322  *    - [other]                  if there was a failure in
1323  *                               the cryptographic mechanisms.
1324  */
1325 srtp_err_status_t srtp_protect_rtcp(srtp_t ctx,
1326                                     void *rtcp_hdr,
1327                                     int *pkt_octet_len);
1328 
1329 /**
1330  * @brief srtp_protect_rtcp_mki() is the Secure RTCP sender-side packet
1331  * processing function that can utilize mki.
1332  *
1333  * The function call srtp_protect_rtcp(ctx, rtp_hdr, len_ptr) applies
1334  * SRTCP protection to the RTCP packet rtcp_hdr (which has length
1335  * *len_ptr) using the SRTP session context ctx.  If srtp_err_status_ok is
1336  * returned, then rtp_hdr points to the resulting SRTCP packet and
1337  * *len_ptr is the number of octets in that packet; otherwise, no
1338  * assumptions should be made about the value of either data elements.
1339  *
1340  * @warning This function assumes that it can write the authentication
1341  * tag into the location in memory immediately following the RTCP
1342  * packet, and assumes that the RTCP packet is aligned on a 32-bit
1343  * boundary.
1344  *
1345  * @warning This function assumes that it can write SRTP_MAX_TRAILER_LEN+4
1346  * into the location in memory immediately following the RTCP packet.
1347  * Callers MUST ensure that this much writable memory is available in
1348  * the buffer that holds the RTCP packet.
1349  *
1350  * @param ctx is the SRTP context to use in processing the packet.
1351  *
1352  * @param rtcp_hdr is a pointer to the RTCP packet (before the call); after
1353  * the function returns, it points to the srtp packet.
1354  *
1355  * @param pkt_octet_len is a pointer to the length in octets of the
1356  * complete RTCP packet (header and body) before the function call,
1357  * and of the complete SRTCP packet after the call, if srtp_err_status_ok
1358  * was returned.  Otherwise, the value of the data to which it points
1359  * is undefined.
1360  *
1361  * @param use_mki is a boolean to tell the system if mki is being used.  If
1362  * set to false then will use the first set of session keys.  If set to true
1363  * will
1364  * use the session keys identified by the mki_index
1365  *
1366  * @param mki_index integer value specifying which set of session kesy should be
1367  * used if use_mki is set to true.
1368  *
1369  * @return
1370  *    - srtp_err_status_ok            if there were no problems.
1371  *    - [other]                  if there was a failure in
1372  *                               the cryptographic mechanisms.
1373  */
1374 srtp_err_status_t srtp_protect_rtcp_mki(srtp_t ctx,
1375                                         void *rtcp_hdr,
1376                                         int *pkt_octet_len,
1377                                         unsigned int use_mki,
1378                                         unsigned int mki_index);
1379 
1380 /**
1381  * @brief srtp_unprotect_rtcp() is the Secure RTCP receiver-side packet
1382  * processing function.
1383  *
1384  * The function call srtp_unprotect_rtcp(ctx, srtp_hdr, len_ptr)
1385  * verifies the Secure RTCP protection of the SRTCP packet pointed to
1386  * by srtcp_hdr (which has length *len_ptr), using the SRTP session
1387  * context ctx.  If srtp_err_status_ok is returned, then srtcp_hdr points
1388  * to the resulting RTCP packet and *len_ptr is the number of octets
1389  * in that packet; otherwise, no assumptions should be made about the
1390  * value of either data elements.
1391  *
1392  * @warning This function assumes that the SRTCP packet is aligned on a
1393  * 32-bit boundary.
1394  *
1395  * @param ctx is a pointer to the srtp_t which applies to the
1396  * particular packet.
1397  *
1398  * @param srtcp_hdr is a pointer to the header of the SRTCP packet
1399  * (before the call).  After the function returns, it points to the
1400  * rtp packet if srtp_err_status_ok was returned; otherwise, the value of
1401  * the data to which it points is undefined.
1402  *
1403  * @param pkt_octet_len is a pointer to the length in octets of the
1404  * complete SRTCP packet (header and body) before the function call,
1405  * and of the complete rtp packet after the call, if srtp_err_status_ok was
1406  * returned.  Otherwise, the value of the data to which it points is
1407  * undefined.
1408  *
1409  * @return
1410  *    - srtp_err_status_ok          if the RTCP packet is valid.
1411  *    - srtp_err_status_auth_fail   if the SRTCP packet failed the message
1412  *                             authentication check.
1413  *    - srtp_err_status_replay_fail if the SRTCP packet is a replay (e.g. has
1414  *                             already been processed and accepted).
1415  *    - [other]  if there has been an error in the cryptographic mechanisms.
1416  *
1417  */
1418 srtp_err_status_t srtp_unprotect_rtcp(srtp_t ctx,
1419                                       void *srtcp_hdr,
1420                                       int *pkt_octet_len);
1421 
1422 /**
1423  * @brief srtp_unprotect_rtcp() is the Secure RTCP receiver-side packet
1424  * processing function.
1425  *
1426  * The function call srtp_unprotect_rtcp(ctx, srtp_hdr, len_ptr)
1427  * verifies the Secure RTCP protection of the SRTCP packet pointed to
1428  * by srtcp_hdr (which has length *len_ptr), using the SRTP session
1429  * context ctx.  If srtp_err_status_ok is returned, then srtcp_hdr points
1430  * to the resulting RTCP packet and *len_ptr is the number of octets
1431  * in that packet; otherwise, no assumptions should be made about the
1432  * value of either data elements.
1433  *
1434  * @warning This function assumes that the SRTCP packet is aligned on a
1435  * 32-bit boundary.
1436  *
1437  * @param ctx is a pointer to the srtp_t which applies to the
1438  * particular packet.
1439  *
1440  * @param srtcp_hdr is a pointer to the header of the SRTCP packet
1441  * (before the call).  After the function returns, it points to the
1442  * rtp packet if srtp_err_status_ok was returned; otherwise, the value of
1443  * the data to which it points is undefined.
1444  *
1445  * @param pkt_octet_len is a pointer to the length in octets of the
1446  * complete SRTCP packet (header and body) before the function call,
1447  * and of the complete rtp packet after the call, if srtp_err_status_ok was
1448  * returned.  Otherwise, the value of the data to which it points is
1449  * undefined.
1450  *
1451  * @param use_mki is a boolean to tell the system if mki is being used.  If
1452  * set to false then will use the first set of session keys.  If set to true
1453  * will use the session keys identified by the mki_index
1454  *
1455  * @return
1456  *    - srtp_err_status_ok          if the RTCP packet is valid.
1457  *    - srtp_err_status_auth_fail   if the SRTCP packet failed the message
1458  *                                  authentication check.
1459  *    - srtp_err_status_replay_fail if the SRTCP packet is a replay (e.g. has
1460  *                                  already been processed and accepted).
1461  *    - srtp_err_status_bad_mki     if the MKI in the packet is not a known MKI
1462  *                                  id
1463  *    - [other]                     if there has been an error in the
1464  *                                  cryptographic mechanisms.
1465  *
1466  */
1467 srtp_err_status_t srtp_unprotect_rtcp_mki(srtp_t ctx,
1468                                           void *srtcp_hdr,
1469                                           int *pkt_octet_len,
1470                                           unsigned int use_mki);
1471 
1472 /**
1473  * @}
1474  */
1475 
1476 /**
1477  * @defgroup User data associated to a SRTP session.
1478  * @ingroup  SRTP
1479  *
1480  * @brief Store custom user data within a SRTP session.
1481  *
1482  * @{
1483  */
1484 
1485 /**
1486  * @brief srtp_set_user_data() stores the given pointer into the SRTP
1487  * session for later retrieval.
1488  *
1489  * @param ctx is the srtp_t context in which the given data pointer is
1490  * stored.
1491  *
1492  * @param data is a pointer to the custom information (struct, function,
1493  * etc) associated with the SRTP session.
1494  *
1495  * @return void.
1496  *
1497  */
1498 void srtp_set_user_data(srtp_t ctx, void *data);
1499 
1500 /**
1501  * @brief srtp_get_user_data() retrieves the pointer to the custom data
1502  * previously stored with srtp_set_user_data().
1503  *
1504  * This function is mostly useful for retrieving data associated to a
1505  * SRTP session when an event fires. The user can then get such a custom
1506  * data by calling this function with the session field of the
1507  * srtp_event_data_t struct as argument.
1508  *
1509  * @param ctx is the srtp_t context in which the given data pointer was
1510  * stored.
1511  *
1512  * @return void* pointer to the user data.
1513  *
1514  */
1515 void *srtp_get_user_data(srtp_t ctx);
1516 
1517 /**
1518  * @}
1519  */
1520 
1521 /**
1522  * @defgroup SRTPevents SRTP events and callbacks
1523  * @ingroup  SRTP
1524  *
1525  * @brief libSRTP can use a user-provided callback function to
1526  * handle events.
1527  *
1528  *
1529  * libSRTP allows a user to provide a callback function to handle
1530  * events that need to be dealt with outside of the data plane (see
1531  * the enum srtp_event_t for a description of these events).  Dealing
1532  * with these events is not a strict necessity; they are not
1533  * security-critical, but the application may suffer if they are not
1534  * handled.  The function srtp_set_event_handler() is used to provide
1535  * the callback function.
1536  *
1537  * A default event handler that merely reports on the events as they
1538  * happen is included.  It is also possible to set the event handler
1539  * function to NULL, in which case all events will just be silently
1540  * ignored.
1541  *
1542  * @{
1543  */
1544 
1545 /**
1546  * @brief srtp_event_t defines events that need to be handled
1547  *
1548  * The enum srtp_event_t defines events that need to be handled
1549  * outside the `data plane', such as SSRC collisions and
1550  * key expirations.
1551  *
1552  * When a key expires or the maximum number of packets has been
1553  * reached, an SRTP stream will enter an `expired' state in which no
1554  * more packets can be protected or unprotected.  When this happens,
1555  * it is likely that you will want to either deallocate the stream
1556  * (using srtp_remove_stream()), and possibly allocate a new one.
1557  *
1558  * When an SRTP stream expires, the other streams in the same session
1559  * are unaffected, unless key sharing is used by that stream.  In the
1560  * latter case, all of the streams in the session will expire.
1561  */
1562 typedef enum {
1563     event_ssrc_collision,    /**< An SSRC collision occured.            */
1564     event_key_soft_limit,    /**< An SRTP stream reached the soft key   */
1565                              /**< usage limit and will expire soon.     */
1566     event_key_hard_limit,    /**< An SRTP stream reached the hard       */
1567                              /**< key usage limit and has expired.      */
1568     event_packet_index_limit /**< An SRTP stream reached the hard       */
1569                              /**< packet limit (2^48 packets).          */
1570 } srtp_event_t;
1571 
1572 /**
1573  * @brief srtp_event_data_t is the structure passed as a callback to
1574  * the event handler function
1575  *
1576  * The struct srtp_event_data_t holds the data passed to the event
1577  * handler function.
1578  */
1579 typedef struct srtp_event_data_t {
1580     srtp_t session;     /**< The session in which the event happend.        */
1581     uint32_t ssrc;      /**< The ssrc in host order of the stream in which  */
1582                         /**< the event happend                              */
1583     srtp_event_t event; /**< An enum indicating the type of event.          */
1584 } srtp_event_data_t;
1585 
1586 /**
1587  * @brief srtp_event_handler_func_t is the function prototype for
1588  * the event handler.
1589  *
1590  * The typedef srtp_event_handler_func_t is the prototype for the
1591  * event handler function.  It has as its only argument an
1592  * srtp_event_data_t which describes the event that needs to be handled.
1593  * There can only be a single, global handler for all events in
1594  * libSRTP.
1595  */
1596 typedef void(srtp_event_handler_func_t)(srtp_event_data_t *data);
1597 
1598 /**
1599  * @brief sets the event handler to the function supplied by the caller.
1600  *
1601  * The function call srtp_install_event_handler(func) sets the event
1602  * handler function to the value func.  The value NULL is acceptable
1603  * as an argument; in this case, events will be ignored rather than
1604  * handled.
1605  *
1606  * @param func is a pointer to a fuction that takes an srtp_event_data_t
1607  *             pointer as an argument and returns void.  This function
1608  *             will be used by libSRTP to handle events.
1609  */
1610 srtp_err_status_t srtp_install_event_handler(srtp_event_handler_func_t func);
1611 
1612 /**
1613  * @brief Returns the version string of the library.
1614  *
1615  */
1616 const char *srtp_get_version_string(void);
1617 
1618 /**
1619  * @brief Returns the numeric representation of the library version.
1620  *
1621  */
1622 unsigned int srtp_get_version(void);
1623 
1624 /**
1625  * @brief srtp_set_debug_module(mod_name, v)
1626  *
1627  * sets dynamic debugging to the value v (0 for off, 1 for on) for the
1628  * debug module with the name mod_name
1629  *
1630  * returns err_status_ok on success, err_status_fail otherwise
1631  */
1632 srtp_err_status_t srtp_set_debug_module(const char *mod_name, int v);
1633 
1634 /**
1635  * @brief srtp_list_debug_modules() outputs a list of debugging modules
1636  *
1637  */
1638 srtp_err_status_t srtp_list_debug_modules(void);
1639 
1640 /**
1641  * @brief srtp_log_level_t defines log levels.
1642  *
1643  * The enumeration srtp_log_level_t defines log levels reported
1644  * in the srtp_log_handler_func_t.
1645  *
1646  */
1647 typedef enum {
1648     srtp_log_level_error,   /**< log level is reporting an error message  */
1649     srtp_log_level_warning, /**< log level is reporting a warning message */
1650     srtp_log_level_info,    /**< log level is reporting an info message   */
1651     srtp_log_level_debug    /**< log level is reporting a debug message   */
1652 } srtp_log_level_t;
1653 
1654 /**
1655  * @brief srtp_log_handler_func_t is the function prototype for
1656  * the log handler.
1657  *
1658  * The typedef srtp_event_handler_func_t is the prototype for the
1659  * event handler function.  It has as srtp_log_level_t, log
1660  * message and data as arguments.
1661  * There can only be a single, global handler for all log messages in
1662  * libSRTP.
1663  */
1664 typedef void(srtp_log_handler_func_t)(srtp_log_level_t level,
1665                                       const char *msg,
1666                                       void *data);
1667 
1668 /**
1669  * @brief sets the log handler to the function supplied by the caller.
1670  *
1671  * The function call srtp_install_log_handler(func) sets the log
1672  * handler function to the value func.  The value NULL is acceptable
1673  * as an argument; in this case, log messages will be ignored.
1674  * This function can be called before srtp_init() inorder to capture
1675  * any logging during start up.
1676  *
1677  * @param func is a pointer to a fuction of type srtp_log_handler_func_t.
1678  *             This function will be used by libSRTP to output log messages.
1679  * @param data is a user pointer that will be returned as the data argument in
1680  * func.
1681  */
1682 srtp_err_status_t srtp_install_log_handler(srtp_log_handler_func_t func,
1683                                            void *data);
1684 
1685 /**
1686  * @brief srtp_get_protect_trailer_length(session, use_mki, mki_index, length)
1687  *
1688  * Determines the length of the amount of data Lib SRTP will add to the
1689  * packet during the protect process. The length is returned in the length
1690  * parameter
1691  *
1692  * returns err_status_ok on success, err_status_bad_mki if the MKI index is
1693  * invalid
1694  *
1695  */
1696 srtp_err_status_t srtp_get_protect_trailer_length(srtp_t session,
1697                                                   uint32_t use_mki,
1698                                                   uint32_t mki_index,
1699                                                   uint32_t *length);
1700 
1701 /**
1702  * @brief srtp_get_protect_rtcp_trailer_length(session, use_mki, mki_index,
1703  * length)
1704  *
1705  * Determines the length of the amount of data Lib SRTP will add to the
1706  * packet during the protect process. The length is returned in the length
1707  * parameter
1708  *
1709  * returns err_status_ok on success, err_status_bad_mki if the MKI index is
1710  * invalid
1711  *
1712  */
1713 srtp_err_status_t srtp_get_protect_rtcp_trailer_length(srtp_t session,
1714                                                        uint32_t use_mki,
1715                                                        uint32_t mki_index,
1716                                                        uint32_t *length);
1717 
1718 /**
1719  * @brief srtp_set_stream_roc(session, ssrc, roc)
1720  *
1721  * Set the roll-over-counter on a session for a given SSRC
1722  *
1723  * returns err_status_ok on success, srtp_err_status_bad_param if there is no
1724  * stream found
1725  *
1726  */
1727 srtp_err_status_t srtp_set_stream_roc(srtp_t session,
1728                                       uint32_t ssrc,
1729                                       uint32_t roc);
1730 
1731 /**
1732  * @brief srtp_get_stream_roc(session, ssrc, roc)
1733  *
1734  * Get the roll-over-counter on a session for a given SSRC
1735  *
1736  * returns err_status_ok on success, srtp_err_status_bad_param if there is no
1737  * stream found
1738  *
1739  */
1740 srtp_err_status_t srtp_get_stream_roc(srtp_t session,
1741                                       uint32_t ssrc,
1742                                       uint32_t *roc);
1743 
1744 /**
1745  * @}
1746  */
1747 
1748 /* in host order, so outside the #if */
1749 #define SRTCP_E_BIT 0x80000000
1750 
1751 /* for byte-access */
1752 #define SRTCP_E_BYTE_BIT 0x80
1753 #define SRTCP_INDEX_MASK 0x7fffffff
1754 
1755 #ifdef __cplusplus
1756 }
1757 #endif
1758 
1759 #endif /* SRTP_SRTP_H */
1760