netwerk/srtp/src/include/srtp.h

   1 /*
   2  * srtp.h
   3  *
   4  * interface to libsrtp
   5  *
   6  * David A. McGrew
   7  * Cisco Systems, Inc.
   8  */
   9 /*
  10  *
  11  * Copyright (c) 2001-2006, 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
  46 #ifndef SRTP_H
  47 #define SRTP_H
  48
  49 #ifdef __cplusplus
  50 extern "C" {
  51 #endif
  52
  53 #include "crypto_kernel.h"
  54
  55 /**
  56  * @defgroup SRTP Secure RTP
  57  *
  58  * @brief libSRTP provides functions for protecting RTP and RTCP.  See
  59  * Section @ref Overview for an introduction to the use of the library.
  60  *
  61  * @{
  62  */
  63
  64 /*
  65  * SRTP_MASTER_KEY_LEN is the nominal master key length supported by libSRTP
  66  */
  67
  68 #define SRTP_MASTER_KEY_LEN 30
  69
  70 /*
  71  * SRTP_MAX_KEY_LEN is the maximum key length supported by libSRTP
  72  */
  73 #define SRTP_MAX_KEY_LEN      64
  74
  75 /*
  76  * SRTP_MAX_TAG_LEN is the maximum tag length supported by libSRTP
  77  */
  78
  79 #define SRTP_MAX_TAG_LEN 12
  80
  81 /**
  82  * SRTP_MAX_TRAILER_LEN is the maximum length of the SRTP trailer
  83  * (authentication tag and MKI) supported by libSRTP.  This value is
  84  * the maximum number of octets that will be added to an RTP packet by
  85  * srtp_protect().
  86  *
  87  * @brief the maximum number of octets added by srtp_protect().
  88  */
  89 #define SRTP_MAX_TRAILER_LEN SRTP_MAX_TAG_LEN
  90
  91 /*
  92  * nota bene: since libSRTP doesn't support the use of the MKI, the
  93  * SRTP_MAX_TRAILER_LEN value is just the maximum tag length
  94  */
  95
  96 /**
  97  * @brief sec_serv_t describes a set of security services.
  98  *
  99  * A sec_serv_t enumeration is used to describe the particular
 100  * security services that will be applied by a particular crypto
 101  * policy (or other mechanism).
 102  */
 103
 104 typedef enum {
 105   sec_serv_none          = 0, /**< no services                        */
 106   sec_serv_conf          = 1, /**< confidentiality                    */
 107   sec_serv_auth          = 2, /**< authentication                     */
 108   sec_serv_conf_and_auth = 3  /**< confidentiality and authentication */
 109 } sec_serv_t;
 110
 111 /**
 112  * @brief crypto_policy_t describes a particular crypto policy that
 113  * can be applied to an SRTP stream.
 114  *
 115  * A crypto_policy_t describes a particular cryptographic policy that
 116  * can be applied to an SRTP or SRTCP stream.  An SRTP session policy
 117  * consists of a list of these policies, one for each SRTP stream
 118  * in the session.
 119  */
 120
 121 typedef struct crypto_policy_t {
 122   cipher_type_id_t cipher_type;    /**< An integer representing
 123                                     *   the type of cipher.  */
 124   int              cipher_key_len; /**< The length of the cipher key
 125                                     *   in octets.                       */
 126   auth_type_id_t   auth_type;      /**< An integer representing the
 127                                     *   authentication function.         */
 128   int              auth_key_len;   /**< The length of the authentication
 129                                     *   function key in octets.          */
 130   int              auth_tag_len;   /**< The length of the authentication
 131                                     *   tag in octets.                   */
 132   sec_serv_t       sec_serv;       /**< The flag indicating the security
 133                                     *   services to be applied.          */
 134 } crypto_policy_t;
 135
 136
 137 /**
 138  * @brief ssrc_type_t describes the type of an SSRC.
 139  *
 140  * An ssrc_type_t enumeration is used to indicate a type of SSRC.  See
 141  * @ref srtp_policy_t for more informataion.
 142  */
 143
 144 typedef enum {
 145   ssrc_undefined    = 0,  /**< Indicates an undefined SSRC type. */
 146   ssrc_specific     = 1,  /**< Indicates a specific SSRC value   */
 147   ssrc_any_inbound  = 2, /**< Indicates any inbound SSRC value
 148                             (i.e. a value that is used in the
 149                             function srtp_unprotect())              */
 150   ssrc_any_outbound = 3  /**< Indicates any outbound SSRC value
 151                             (i.e. a value that is used in the
 152                             function srtp_protect())              */
 153 } ssrc_type_t;
 154
 155 /**
 156  * @brief An ssrc_t represents a particular SSRC value, or a `wildcard' SSRC.
 157  *
 158  * An ssrc_t represents a particular SSRC value (if its type is
 159  * ssrc_specific), or a wildcard SSRC value that will match all
 160  * outbound SSRCs (if its type is ssrc_any_outbound) or all inbound
 161  * SSRCs (if its type is ssrc_any_inbound).
 162  *
 163  */
 164
 165 typedef struct {
 166   ssrc_type_t type;   /**< The type of this particular SSRC */
 167   unsigned int value; /**< The value of this SSRC, if it is not a wildcard */
 168 } ssrc_t;
 169
 170
 171 /**
 172  * @brief points to an EKT policy
 173  */
 174 typedef struct ekt_policy_ctx_t *ekt_policy_t;
 175
 176
 177 /**
 178  * @brief points to EKT stream data
 179  */
 180 typedef struct ekt_stream_ctx_t *ekt_stream_t;
 181
 182
 183 /**
 184  * @brief represents the policy for an SRTP session.
 185  *
 186  * A single srtp_policy_t struct represents the policy for a single
 187  * SRTP stream, and a linked list of these elements represents the
 188  * policy for an entire SRTP session.  Each element contains the SRTP
 189  * and SRTCP crypto policies for that stream, a pointer to the SRTP
 190  * master key for that stream, the SSRC describing that stream, or a
 191  * flag indicating a `wildcard' SSRC value, and a `next' field that
 192  * holds a pointer to the next element in the list of policy elements,
 193  * or NULL if it is the last element.
 194  *
 195  * The wildcard value SSRC_ANY_INBOUND matches any SSRC from an
 196  * inbound stream that for which there is no explicit SSRC entry in
 197  * another policy element.  Similarly, the value SSRC_ANY_OUTBOUND
 198  * will matches any SSRC from an outbound stream that does not appear
 199  * in another policy element.  Note that wildcard SSRCs &b cannot be
 200  * used to match both inbound and outbound traffic.  This restriction
 201  * is intentional, and it allows libSRTP to ensure that no security
 202  * lapses result from accidental re-use of SSRC values during key
 203  * sharing.
 204  *
 205  *
 206  * @warning The final element of the list @b must have its `next' pointer
 207  *          set to NULL.
 208  */
 209
 210 typedef struct srtp_policy_t {
 211   ssrc_t        ssrc;        /**< The SSRC value of stream, or the
 212                               *   flags SSRC_ANY_INBOUND or
 213                               *   SSRC_ANY_OUTBOUND if key sharing
 214                               *   is used for this policy element.
 215                               */
 216   crypto_policy_t rtp;         /**< SRTP crypto policy.                  */
 217   crypto_policy_t rtcp;        /**< SRTCP crypto policy.                 */
 218   unsigned char *key;          /**< Pointer to the SRTP master key for
 219                                 *    this stream.                        */
 220   ekt_policy_t ekt;            /**< Pointer to the EKT policy structure
 221                                 *   for this stream (if any)             */
 222   unsigned long window_size;   /**< The window size to use for replay
 223                                 *   protection. */
 224   int        allow_repeat_tx;  /**< Whether retransmissions of
 225                                 *   packets with the same sequence number
 226                                 *   are allowed.  (Note that such repeated
 227                                 *   transmissions must have the same RTP
 228                                 *   payload, or a severe security weakness
 229                                 *   is introduced!)                      */
 230   struct srtp_policy_t *next;  /**< Pointer to next stream policy.       */
 231 } srtp_policy_t;
 232
 233
 234
 235
 236 /**
 237  * @brief An srtp_t points to an SRTP session structure.
 238  *
 239  * The typedef srtp_t is a pointer to a structure that represents
 240  * an SRTP session.  This datatype is intentially opaque in
 241  * order to separate the interface from the implementation.
 242  *
 243  * An SRTP session consists of all of the traffic sent to the RTP and
 244  * RTCP destination transport addresses, using the RTP/SAVP (Secure
 245  * Audio/Video Profile).  A session can be viewed as a set of SRTP
 246  * streams, each of which originates with a different participant.
 247  */
 248
 249 typedef struct srtp_ctx_t *srtp_t;
 250
 251
 252 /**
 253  * @brief An srtp_stream_t points to an SRTP stream structure.
 254  *
 255  * The typedef srtp_stream_t is a pointer to a structure that
 256  * represents an SRTP stream.  This datatype is intentionally
 257  * opaque in order to separate the interface from the implementation.
 258  *
 259  * An SRTP stream consists of all of the traffic sent to an SRTP
 260  * session by a single participant.  A session can be viewed as
 261  * a set of streams.
 262  *
 263  */
 264 typedef struct srtp_stream_ctx_t *srtp_stream_t;
 265
 266
 267
 268 /**
 269  * @brief srtp_init() initializes the srtp library.
 270  *
 271  * @warning This function @b must be called before any other srtp
 272  * functions.
 273  */
 274
 275 err_status_t
 276 srtp_init(void);
 277
 278 /**
 279  * @brief srtp_shutdown() de-initializes the srtp library.
 280  *
 281  * @warning No srtp functions may be called after calling this function.
 282  */
 283
 284 err_status_t
 285 srtp_shutdown(void);
 286
 287 /**
 288  * @brief srtp_protect() is the Secure RTP sender-side packet processing
 289  * function.
 290  *
 291  * The function call srtp_protect(ctx, rtp_hdr, len_ptr) applies SRTP
 292  * protection to the RTP packet rtp_hdr (which has length *len_ptr) using
 293  * the SRTP context ctx.  If err_status_ok is returned, then rtp_hdr
 294  * points to the resulting SRTP packet and *len_ptr is the number of
 295  * octets in that packet; otherwise, no assumptions should be made
 296  * about the value of either data elements.
 297  *
 298  * The sequence numbers of the RTP packets presented to this function
 299  * need not be consecutive, but they @b must be out of order by less
 300  * than 2^15 = 32,768 packets.
 301  *
 302  * @warning This function assumes that it can write the authentication
 303  * tag into the location in memory immediately following the RTP
 304  * packet, and assumes that the RTP packet is aligned on a 32-bit
 305  * boundary.
 306  *
 307  * @param ctx is the SRTP context to use in processing the packet.
 308  *
 309  * @param rtp_hdr is a pointer to the RTP packet (before the call); after
 310  * the function returns, it points to the srtp packet.
 311  *
 312  * @param len_ptr is a pointer to the length in octets of the complete
 313  * RTP packet (header and body) before the function call, and of the
 314  * complete SRTP packet after the call, if err_status_ok was returned.
 315  * Otherwise, the value of the data to which it points is undefined.
 316  *
 317  * @return
 318  *    - err_status_ok            no problems
 319  *    - err_status_replay_fail   rtp sequence number was non-increasing
 320  *    - @e other                 failure in cryptographic mechanisms
 321  */
 322
 323 err_status_t
 324 srtp_protect(srtp_t ctx, void *rtp_hdr, int *len_ptr);
 325
 326 /**
 327  * @brief srtp_unprotect() is the Secure RTP receiver-side packet
 328  * processing function.
 329  *
 330  * The function call srtp_unprotect(ctx, srtp_hdr, len_ptr) verifies
 331  * the Secure RTP protection of the SRTP packet pointed to by srtp_hdr
 332  * (which has length *len_ptr), using the SRTP context ctx.  If
 333  * err_status_ok is returned, then srtp_hdr points to the resulting
 334  * RTP packet and *len_ptr is the number of octets in that packet;
 335  * otherwise, no assumptions should be made about the value of either
 336  * data elements.
 337  *
 338  * The sequence numbers of the RTP packets presented to this function
 339  * need not be consecutive, but they @b must be out of order by less
 340  * than 2^15 = 32,768 packets.
 341  *
 342  * @warning This function assumes that the SRTP packet is aligned on a
 343  * 32-bit boundary.
 344  *
 345  * @param ctx is a pointer to the srtp_t which applies to the
 346  * particular packet.
 347  *
 348  * @param srtp_hdr is a pointer to the header of the SRTP packet
 349  * (before the call).  after the function returns, it points to the
 350  * rtp packet if err_status_ok was returned; otherwise, the value of
 351  * the data to which it points is undefined.
 352  *
 353  * @param len_ptr is a pointer to the length in octets of the complete
 354  * srtp packet (header and body) before the function call, and of the
 355  * complete rtp packet after the call, if err_status_ok was returned.
 356  * Otherwise, the value of the data to which it points is undefined.
 357  *
 358  * @return
 359  *    - err_status_ok          if the RTP packet is valid.
 360  *    - err_status_auth_fail   if the SRTP packet failed the message
 361  *                             authentication check.
 362  *    - err_status_replay_fail if the SRTP packet is a replay (e.g. packet has
 363  *                             already been processed and accepted).
 364  *    - [other]  if there has been an error in the cryptographic mechanisms.
 365  *
 366  */
 367
 368 err_status_t
 369 srtp_unprotect(srtp_t ctx, void *srtp_hdr, int *len_ptr);
 370
 371
 372 /**
 373  * @brief srtp_create() allocates and initializes an SRTP session.
 374
 375  * The function call srtp_create(session, policy, key) allocates and
 376  * initializes an SRTP session context, applying the given policy and
 377  * key.
 378  *
 379  * @param session is the SRTP session to which the policy is to be added.
 380  *
 381  * @param policy is the srtp_policy_t struct that describes the policy
 382  * for the session.  The struct may be a single element, or it may be
 383  * the head of a list, in which case each element of the list is
 384  * processed.  It may also be NULL, in which case streams should be added
 385  * later using srtp_add_stream().  The final element of the list @b must
 386  * have its `next' field set to NULL.
 387  *
 388  * @return
 389  *    - err_status_ok           if creation succeded.
 390  *    - err_status_alloc_fail   if allocation failed.
 391  *    - err_status_init_fail    if initialization failed.
 392  */
 393
 394 err_status_t
 395 srtp_create(srtp_t *session, const srtp_policy_t *policy);
 396
 397
 398 /**
 399  * @brief srtp_add_stream() allocates and initializes an SRTP stream
 400  * within a given SRTP session.
 401  *
 402  * The function call srtp_add_stream(session, policy) allocates and
 403  * initializes a new SRTP stream within a given, previously created
 404  * session, applying the policy given as the other argument to that
 405  * stream.
 406  *
 407  * @return values:
 408  *    - err_status_ok           if stream creation succeded.
 409  *    - err_status_alloc_fail   if stream allocation failed
 410  *    - err_status_init_fail    if stream initialization failed.
 411  */
 412
 413 err_status_t
 414 srtp_add_stream(srtp_t session,
 415                 const srtp_policy_t *policy);
 416
 417
 418 /**
 419  * @brief srtp_remove_stream() deallocates an SRTP stream.
 420  *
 421  * The function call srtp_remove_stream(session, ssrc) removes
 422  * the SRTP stream with the SSRC value ssrc from the SRTP session
 423  * context given by the argument session.
 424  *
 425  * @param session is the SRTP session from which the stream
 426  *        will be removed.
 427  *
 428  * @param ssrc is the SSRC value of the stream to be removed.
 429  *
 430  * @warning Wildcard SSRC values cannot be removed from a
 431  *          session.
 432  *
 433  * @return
 434  *    - err_status_ok     if the stream deallocation succeded.
 435  *    - [other]           otherwise.
 436  *
 437  */
 438
 439 err_status_t
 440 srtp_remove_stream(srtp_t session, unsigned int ssrc);
 441
 442 /**
 443  * @brief crypto_policy_set_rtp_default() sets a crypto policy
 444  * structure to the SRTP default policy for RTP protection.
 445  *
 446  * @param p is a pointer to the policy structure to be set
 447  *
 448  * The function call crypto_policy_set_rtp_default(&p) sets the
 449  * crypto_policy_t at location p to the SRTP default policy for RTP
 450  * protection, as defined in the specification.  This function is a
 451  * convenience that helps to avoid dealing directly with the policy
 452  * data structure.  You are encouraged to initialize policy elements
 453  * with this function call.  Doing so may allow your code to be
 454  * forward compatible with later versions of libSRTP that include more
 455  * elements in the crypto_policy_t datatype.
 456  *
 457  * @return void.
 458  *
 459  */
 460
 461 void
 462 crypto_policy_set_rtp_default(crypto_policy_t *p);
 463
 464 /**
 465  * @brief crypto_policy_set_rtcp_default() sets a crypto policy
 466  * structure to the SRTP default policy for RTCP protection.
 467  *
 468  * @param p is a pointer to the policy structure to be set
 469  *
 470  * The function call crypto_policy_set_rtcp_default(&p) sets the
 471  * crypto_policy_t at location p to the SRTP default policy for RTCP
 472  * protection, as defined in the specification.  This function is a
 473  * convenience that helps to avoid dealing directly with the policy
 474  * data structure.  You are encouraged to initialize policy elements
 475  * with this function call.  Doing so may allow your code to be
 476  * forward compatible with later versions of libSRTP that include more
 477  * elements in the crypto_policy_t datatype.
 478  *
 479  * @return void.
 480  *
 481  */
 482
 483 void
 484 crypto_policy_set_rtcp_default(crypto_policy_t *p);
 485
 486 /**
 487  * @brief crypto_policy_set_aes_cm_128_hmac_sha1_80() sets a crypto
 488  * policy structure to the SRTP default policy for RTP protection.
 489  *
 490  * @param p is a pointer to the policy structure to be set
 491  *
 492  * The function crypto_policy_set_aes_cm_128_hmac_sha1_80() is a
 493  * synonym for crypto_policy_set_rtp_default().  It conforms to the
 494  * naming convention used in RFC 4568 (SDP Security Descriptions for
 495  * Media Streams).
 496  *
 497  * @return void.
 498  *
 499  */
 500
 501 #define crypto_policy_set_aes_cm_128_hmac_sha1_80(p) crypto_policy_set_rtp_default(p)
 502
 503
 504 /**
 505  * @brief crypto_policy_set_aes_cm_128_hmac_sha1_32() sets a crypto
 506  * policy structure to a short-authentication tag policy
 507  *
 508  * @param p is a pointer to the policy structure to be set
 509  *
 510  * The function call crypto_policy_set_aes_cm_128_hmac_sha1_32(&p)
 511  * sets the crypto_policy_t at location p to use policy
 512  * AES_CM_128_HMAC_SHA1_32 as defined in RFC 4568.
 513  * This policy uses AES-128
 514  * Counter Mode encryption and HMAC-SHA1 authentication, with an
 515  * authentication tag that is only 32 bits long.  This length is
 516  * considered adequate only for protecting audio and video media that
 517  * use a stateless playback function.  See Section 7.5 of RFC 3711
 518  * (http://www.ietf.org/rfc/rfc3711.txt).
 519  *
 520  * This function is a convenience that helps to avoid dealing directly
 521  * with the policy data structure.  You are encouraged to initialize
 522  * policy elements with this function call.  Doing so may allow your
 523  * code to be forward compatible with later versions of libSRTP that
 524  * include more elements in the crypto_policy_t datatype.
 525  *
 526  * @warning This crypto policy is intended for use in SRTP, but not in
 527  * SRTCP.  It is recommended that a policy that uses longer
 528  * authentication tags be used for SRTCP.  See Section 7.5 of RFC 3711
 529  * (http://www.ietf.org/rfc/rfc3711.txt).
 530  *
 531  * @return void.
 532  *
 533  */
 534
 535 void
 536 crypto_policy_set_aes_cm_128_hmac_sha1_32(crypto_policy_t *p);
 537
 538
 539
 540 /**
 541  * @brief crypto_policy_set_aes_cm_128_null_auth() sets a crypto
 542  * policy structure to an encryption-only policy
 543  *
 544  * @param p is a pointer to the policy structure to be set
 545  *
 546  * The function call crypto_policy_set_aes_cm_128_null_auth(&p) sets
 547  * the crypto_policy_t at location p to use the SRTP default cipher
 548  * (AES-128 Counter Mode), but to use no authentication method.  This
 549  * policy is NOT RECOMMENDED unless it is unavoidable; see Section 7.5
 550  * of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
 551  *
 552  * This function is a convenience that helps to avoid dealing directly
 553  * with the policy data structure.  You are encouraged to initialize
 554  * policy elements with this function call.  Doing so may allow your
 555  * code to be forward compatible with later versions of libSRTP that
 556  * include more elements in the crypto_policy_t datatype.
 557  *
 558  * @warning This policy is NOT RECOMMENDED for SRTP unless it is
 559  * unavoidable, and it is NOT RECOMMENDED at all for SRTCP; see
 560  * Section 7.5 of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
 561  *
 562  * @return void.
 563  *
 564  */
 565
 566 void
 567 crypto_policy_set_aes_cm_128_null_auth(crypto_policy_t *p);
 568
 569
 570 /**
 571  * @brief crypto_policy_set_null_cipher_hmac_sha1_80() sets a crypto
 572  * policy structure to an authentication-only policy
 573  *
 574  * @param p is a pointer to the policy structure to be set
 575  *
 576  * The function call crypto_policy_set_null_cipher_hmac_sha1_80(&p)
 577  * sets the crypto_policy_t at location p to use HMAC-SHA1 with an 80
 578  * bit authentication tag to provide message authentication, but to
 579  * use no encryption.  This policy is NOT RECOMMENDED for SRTP unless
 580  * there is a requirement to forego encryption.
 581  *
 582  * This function is a convenience that helps to avoid dealing directly
 583  * with the policy data structure.  You are encouraged to initialize
 584  * policy elements with this function call.  Doing so may allow your
 585  * code to be forward compatible with later versions of libSRTP that
 586  * include more elements in the crypto_policy_t datatype.
 587  *
 588  * @warning This policy is NOT RECOMMENDED for SRTP unless there is a
 589  * requirement to forego encryption.
 590  *
 591  * @return void.
 592  *
 593  */
 594
 595 void
 596 crypto_policy_set_null_cipher_hmac_sha1_80(crypto_policy_t *p);
 597
 598
 599 /**
 600  * @brief crypto_policy_set_aes_cm_256_hmac_sha1_80() sets a crypto
 601  * policy structure to a encryption and authentication policy using AES-256
 602  * for RTP protection.
 603  *
 604  * @param p is a pointer to the policy structure to be set
 605  *
 606  * The function call crypto_policy_set_aes_cm_256_hmac_sha1_80(&p)
 607  * sets the crypto_policy_t at location p to use policy
 608  * AES_CM_256_HMAC_SHA1_80 as defined in
 609  * draft-ietf-avt-srtp-big-aes-03.txt.  This policy uses AES-256
 610  * Counter Mode encryption and HMAC-SHA1 authentication, with an 80 bit
 611  * authentication tag.
 612  *
 613  * This function is a convenience that helps to avoid dealing directly
 614  * with the policy data structure.  You are encouraged to initialize
 615  * policy elements with this function call.  Doing so may allow your
 616  * code to be forward compatible with later versions of libSRTP that
 617  * include more elements in the crypto_policy_t datatype.
 618  *
 619  * @return void.
 620  *
 621  */
 622
 623 void crypto_policy_set_aes_cm_256_hmac_sha1_80(crypto_policy_t *p);
 624
 625
 626 /**
 627  * @brief crypto_policy_set_aes_cm_256_hmac_sha1_32() sets a crypto
 628  * policy structure to a short-authentication tag policy using AES-256
 629  * encryption.
 630  *
 631  * @param p is a pointer to the policy structure to be set
 632  *
 633  * The function call crypto_policy_set_aes_cm_256_hmac_sha1_32(&p)
 634  * sets the crypto_policy_t at location p to use policy
 635  * AES_CM_256_HMAC_SHA1_32 as defined in
 636  * draft-ietf-avt-srtp-big-aes-03.txt.  This policy uses AES-256
 637  * Counter Mode encryption and HMAC-SHA1 authentication, with an
 638  * authentication tag that is only 32 bits long.  This length is
 639  * considered adequate only for protecting audio and video media that
 640  * use a stateless playback function.  See Section 7.5 of RFC 3711
 641  * (http://www.ietf.org/rfc/rfc3711.txt).
 642  *
 643  * This function is a convenience that helps to avoid dealing directly
 644  * with the policy data structure.  You are encouraged to initialize
 645  * policy elements with this function call.  Doing so may allow your
 646  * code to be forward compatible with later versions of libSRTP that
 647  * include more elements in the crypto_policy_t datatype.
 648  *
 649  * @warning This crypto policy is intended for use in SRTP, but not in
 650  * SRTCP.  It is recommended that a policy that uses longer
 651  * authentication tags be used for SRTCP.  See Section 7.5 of RFC 3711
 652  * (http://www.ietf.org/rfc/rfc3711.txt).
 653  *
 654  * @return void.
 655  *
 656  */
 657
 658 void
 659 crypto_policy_set_aes_cm_256_hmac_sha1_32(crypto_policy_t *p);
 660
 661
 662 /**
 663  * @brief srtp_dealloc() deallocates storage for an SRTP session
 664  * context.
 665  *
 666  * The function call srtp_dealloc(s) deallocates storage for the
 667  * SRTP session context s.  This function should be called no more
 668  * than one time for each of the contexts allocated by the function
 669  * srtp_create().
 670  *
 671  * @param s is the srtp_t for the session to be deallocated.
 672  *
 673  * @return
 674  *    - err_status_ok             if there no problems.
 675  *    - err_status_dealloc_fail   a memory deallocation failure occured.
 676  */
 677
 678 err_status_t
 679 srtp_dealloc(srtp_t s);
 680
 681
 682 /*
 683  * @brief identifies a particular SRTP profile
 684  *
 685  * An srtp_profile_t enumeration is used to identify a particular SRTP
 686  * profile (that is, a set of algorithms and parameters).  These
 687  * profiles are defined in the DTLS-SRTP draft.
 688  */
 689
 690 typedef enum {
 691   srtp_profile_reserved           = 0,
 692   srtp_profile_aes128_cm_sha1_80  = 1,
 693   srtp_profile_aes128_cm_sha1_32  = 2,
 694   srtp_profile_aes256_cm_sha1_80  = 3,
 695   srtp_profile_aes256_cm_sha1_32  = 4,
 696   srtp_profile_null_sha1_80       = 5,
 697   srtp_profile_null_sha1_32       = 6,
 698 } srtp_profile_t;
 699
 700
 701 /**
 702  * @brief crypto_policy_set_from_profile_for_rtp() sets a crypto policy
 703  * structure to the appropriate value for RTP based on an srtp_profile_t
 704  *
 705  * @param p is a pointer to the policy structure to be set
 706  *
 707  * The function call crypto_policy_set_rtp_default(&policy, profile)
 708  * sets the crypto_policy_t at location policy to the policy for RTP
 709  * protection, as defined by the srtp_profile_t profile.
 710  *
 711  * This function is a convenience that helps to avoid dealing directly
 712  * with the policy data structure.  You are encouraged to initialize
 713  * policy elements with this function call.  Doing so may allow your
 714  * code to be forward compatible with later versions of libSRTP that
 715  * include more elements in the crypto_policy_t datatype.
 716  *
 717  * @return values
 718  *     - err_status_ok         no problems were encountered
 719  *     - err_status_bad_param  the profile is not supported
 720  *
 721  */
 722 err_status_t
 723 crypto_policy_set_from_profile_for_rtp(crypto_policy_t *policy,
 724                                        srtp_profile_t profile);
 725
 726
 727
 728
 729 /**
 730  * @brief crypto_policy_set_from_profile_for_rtcp() sets a crypto policy
 731  * structure to the appropriate value for RTCP based on an srtp_profile_t
 732  *
 733  * @param p is a pointer to the policy structure to be set
 734  *
 735  * The function call crypto_policy_set_rtcp_default(&policy, profile)
 736  * sets the crypto_policy_t at location policy to the policy for RTCP
 737  * protection, as defined by the srtp_profile_t profile.
 738  *
 739  * This function is a convenience that helps to avoid dealing directly
 740  * with the policy data structure.  You are encouraged to initialize
 741  * policy elements with this function call.  Doing so may allow your
 742  * code to be forward compatible with later versions of libSRTP that
 743  * include more elements in the crypto_policy_t datatype.
 744  *
 745  * @return values
 746  *     - err_status_ok         no problems were encountered
 747  *     - err_status_bad_param  the profile is not supported
 748  *
 749  */
 750 err_status_t
 751 crypto_policy_set_from_profile_for_rtcp(crypto_policy_t *policy,
 752                                        srtp_profile_t profile);
 753
 754 /**
 755  * @brief returns the master key length for a given SRTP profile
 756  */
 757 unsigned int
 758 srtp_profile_get_master_key_length(srtp_profile_t profile);
 759
 760
 761 /**
 762  * @brief returns the master salt length for a given SRTP profile
 763  */
 764 unsigned int
 765 srtp_profile_get_master_salt_length(srtp_profile_t profile);
 766
 767 /**
 768  * @brief appends the salt to the key
 769  *
 770  * The function call append_salt_to_key(k, klen, s, slen)
 771  * copies the string s to the location at klen bytes following
 772  * the location k.
 773  *
 774  * @warning There must be at least bytes_in_salt + bytes_in_key bytes
 775  *          available at the location pointed to by key.
 776  *
 777  */
 778
 779 void
 780 append_salt_to_key(unsigned char *key, unsigned int bytes_in_key,
 781                    unsigned char *salt, unsigned int bytes_in_salt);
 782
 783
 784
 785 /**
 786  * @}
 787  */
 788
 789
 790
 791 /**
 792  * @defgroup SRTCP Secure RTCP
 793  * @ingroup  SRTP
 794  *
 795  * @brief Secure RTCP functions are used to protect RTCP traffic.
 796  *
 797  * RTCP is the control protocol for RTP.  libSRTP protects RTCP
 798  * traffic in much the same way as it does RTP traffic.  The function
 799  * srtp_protect_rtcp() applies cryptographic protections to outbound
 800  * RTCP packets, and srtp_unprotect_rtcp() verifies the protections on
 801  * inbound RTCP packets.
 802  *
 803  * A note on the naming convention: srtp_protect_rtcp() has an srtp_t
 804  * as its first argument, and thus has `srtp_' as its prefix.  The
 805  * trailing `_rtcp' indicates the protocol on which it acts.
 806  *
 807  * @{
 808  */
 809
 810 /**
 811  * @brief srtp_protect_rtcp() is the Secure RTCP sender-side packet
 812  * processing function.
 813  *
 814  * The function call srtp_protect_rtcp(ctx, rtp_hdr, len_ptr) applies
 815  * SRTCP protection to the RTCP packet rtcp_hdr (which has length
 816  * *len_ptr) using the SRTP session context ctx.  If err_status_ok is
 817  * returned, then rtp_hdr points to the resulting SRTCP packet and
 818  * *len_ptr is the number of octets in that packet; otherwise, no
 819  * assumptions should be made about the value of either data elements.
 820  *
 821  * @warning This function assumes that it can write the authentication
 822  * tag into the location in memory immediately following the RTCP
 823  * packet, and assumes that the RTCP packet is aligned on a 32-bit
 824  * boundary.
 825  *
 826  * @param ctx is the SRTP context to use in processing the packet.
 827  *
 828  * @param rtcp_hdr is a pointer to the RTCP packet (before the call); after
 829  * the function returns, it points to the srtp packet.
 830  *
 831  * @param pkt_octet_len is a pointer to the length in octets of the
 832  * complete RTCP packet (header and body) before the function call,
 833  * and of the complete SRTCP packet after the call, if err_status_ok
 834  * was returned.  Otherwise, the value of the data to which it points
 835  * is undefined.
 836  *
 837  * @return
 838  *    - err_status_ok            if there were no problems.
 839  *    - [other]                  if there was a failure in
 840  *                               the cryptographic mechanisms.
 841  */
 842
 843
 844 err_status_t
 845 srtp_protect_rtcp(srtp_t ctx, void *rtcp_hdr, int *pkt_octet_len);
 846
 847 /**
 848  * @brief srtp_unprotect_rtcp() is the Secure RTCP receiver-side packet
 849  * processing function.
 850  *
 851  * The function call srtp_unprotect_rtcp(ctx, srtp_hdr, len_ptr)
 852  * verifies the Secure RTCP protection of the SRTCP packet pointed to
 853  * by srtcp_hdr (which has length *len_ptr), using the SRTP session
 854  * context ctx.  If err_status_ok is returned, then srtcp_hdr points
 855  * to the resulting RTCP packet and *len_ptr is the number of octets
 856  * in that packet; otherwise, no assumptions should be made about the
 857  * value of either data elements.
 858  *
 859  * @warning This function assumes that the SRTCP packet is aligned on a
 860  * 32-bit boundary.
 861  *
 862  * @param ctx is a pointer to the srtp_t which applies to the
 863  * particular packet.
 864  *
 865  * @param srtcp_hdr is a pointer to the header of the SRTCP packet
 866  * (before the call).  After the function returns, it points to the
 867  * rtp packet if err_status_ok was returned; otherwise, the value of
 868  * the data to which it points is undefined.
 869  *
 870  * @param pkt_octet_len is a pointer to the length in octets of the
 871  * complete SRTCP packet (header and body) before the function call,
 872  * and of the complete rtp packet after the call, if err_status_ok was
 873  * returned.  Otherwise, the value of the data to which it points is
 874  * undefined.
 875  *
 876  * @return
 877  *    - err_status_ok          if the RTCP packet is valid.
 878  *    - err_status_auth_fail   if the SRTCP packet failed the message
 879  *                             authentication check.
 880  *    - err_status_replay_fail if the SRTCP packet is a replay (e.g. has
 881  *                             already been processed and accepted).
 882  *    - [other]  if there has been an error in the cryptographic mechanisms.
 883  *
 884  */
 885
 886 err_status_t
 887 srtp_unprotect_rtcp(srtp_t ctx, void *srtcp_hdr, int *pkt_octet_len);
 888
 889 /**
 890  * @}
 891  */
 892
 893 /**
 894  * @defgroup SRTPevents SRTP events and callbacks
 895  * @ingroup  SRTP
 896  *
 897  * @brief libSRTP can use a user-provided callback function to
 898  * handle events.
 899  *
 900  *
 901  * libSRTP allows a user to provide a callback function to handle
 902  * events that need to be dealt with outside of the data plane (see
 903  * the enum srtp_event_t for a description of these events).  Dealing
 904  * with these events is not a strict necessity; they are not
 905  * security-critical, but the application may suffer if they are not
 906  * handled.  The function srtp_set_event_handler() is used to provide
 907  * the callback function.
 908  *
 909  * A default event handler that merely reports on the events as they
 910  * happen is included.  It is also possible to set the event handler
 911  * function to NULL, in which case all events will just be silently
 912  * ignored.
 913  *
 914  * @{
 915  */
 916
 917 /**
 918  * @brief srtp_event_t defines events that need to be handled
 919  *
 920  * The enum srtp_event_t defines events that need to be handled
 921  * outside the `data plane', such as SSRC collisions and
 922  * key expirations.
 923  *
 924  * When a key expires or the maximum number of packets has been
 925  * reached, an SRTP stream will enter an `expired' state in which no
 926  * more packets can be protected or unprotected.  When this happens,
 927  * it is likely that you will want to either deallocate the stream
 928  * (using srtp_stream_dealloc()), and possibly allocate a new one.
 929  *
 930  * When an SRTP stream expires, the other streams in the same session
 931  * are unaffected, unless key sharing is used by that stream.  In the
 932  * latter case, all of the streams in the session will expire.
 933  */
 934
 935 typedef enum {
 936   event_ssrc_collision,    /**<
 937                             * An SSRC collision occured.
 938                             */
 939   event_key_soft_limit,    /**< An SRTP stream reached the soft key
 940                             *   usage limit and will expire soon.
 941                             */
 942   event_key_hard_limit,    /**< An SRTP stream reached the hard
 943                             *   key usage limit and has expired.
 944                             */
 945   event_packet_index_limit /**< An SRTP stream reached the hard
 946                             * packet limit (2^48 packets).
 947                             */
 948 } srtp_event_t;
 949
 950 /**
 951  * @brief srtp_event_data_t is the structure passed as a callback to
 952  * the event handler function
 953  *
 954  * The struct srtp_event_data_t holds the data passed to the event
 955  * handler function.
 956  */
 957
 958 typedef struct srtp_event_data_t {
 959   srtp_t        session;  /**< The session in which the event happend. */
 960   srtp_stream_t stream;   /**< The stream in which the event happend.  */
 961   srtp_event_t  event;    /**< An enum indicating the type of event.   */
 962 } srtp_event_data_t;
 963
 964 /**
 965  * @brief srtp_event_handler_func_t is the function prototype for
 966  * the event handler.
 967  *
 968  * The typedef srtp_event_handler_func_t is the prototype for the
 969  * event handler function.  It has as its only argument an
 970  * srtp_event_data_t which describes the event that needs to be handled.
 971  * There can only be a single, global handler for all events in
 972  * libSRTP.
 973  */
 974
 975 typedef void (srtp_event_handler_func_t)(srtp_event_data_t *data);
 976
 977 /**
 978  * @brief sets the event handler to the function supplied by the caller.
 979  *
 980  * The function call srtp_install_event_handler(func) sets the event
 981  * handler function to the value func.  The value NULL is acceptable
 982  * as an argument; in this case, events will be ignored rather than
 983  * handled.
 984  *
 985  * @param func is a pointer to a fuction that takes an srtp_event_data_t
 986  *             pointer as an argument and returns void.  This function
 987  *             will be used by libSRTP to handle events.
 988  */
 989
 990 err_status_t
 991 srtp_install_event_handler(srtp_event_handler_func_t func);
 992
 993 /**
 994  * @}
 995  */
 996 /* in host order, so outside the #if */
 997 #define SRTCP_E_BIT      0x80000000
 998 /* for byte-access */
 999 #define SRTCP_E_BYTE_BIT 0x80
1000 #define SRTCP_INDEX_MASK 0x7fffffff
1001
1002 #ifdef __cplusplus
1003 }
1004 #endif
1005
1006 #endif /* SRTP_H */