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 /*

  * srtp.h

  *

  * interface to libsrtp

  *

  * David A. McGrew

  * Cisco Systems, Inc.

  */

 /*

  *	

  * Copyright (c) 2001-2006, Cisco Systems, Inc.

  * All rights reserved.

  * 

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions

  * are met:

  * 

  *   Redistributions of source code must retain the above copyright

  *   notice, this list of conditions and the following disclaimer.

  * 

  *   Redistributions in binary form must reproduce the above

  *   copyright notice, this list of conditions and the following

  *   disclaimer in the documentation and/or other materials provided

  *   with the distribution.

  * 

  *   Neither the name of the Cisco Systems, Inc. nor the names of its

  *   contributors may be used to endorse or promote products derived

  *   from this software without specific prior written permission.

  * 

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS

  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE

  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,

  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

  * OF THE POSSIBILITY OF SUCH DAMAGE.

  *

  */

 #ifndef SRTP_H

 #define SRTP_H

 #ifdef __cplusplus

 extern "C" {

 #endif

 #include "crypto_kernel.h" 

 /**

  * @defgroup SRTP Secure RTP

  *

  * @brief libSRTP provides functions for protecting RTP and RTCP.  See

  * Section @ref Overview for an introduction to the use of the library.

  *

  * @{

  */

 /*

  * SRTP_MASTER_KEY_LEN is the nominal master key length supported by libSRTP

  */

 #define SRTP_MASTER_KEY_LEN 30

 /*

  * SRTP_MAX_KEY_LEN is the maximum key length supported by libSRTP

  */

 #define SRTP_MAX_KEY_LEN      64

 /*

  * SRTP_MAX_TAG_LEN is the maximum tag length supported by libSRTP

  */

 #define SRTP_MAX_TAG_LEN 12 

 /**

  * SRTP_MAX_TRAILER_LEN is the maximum length of the SRTP trailer

  * (authentication tag and MKI) supported by libSRTP.  This value is

  * the maximum number of octets that will be added to an RTP packet by

  * srtp_protect().

  *

  * @brief the maximum number of octets added by srtp_protect().

  */

 #define SRTP_MAX_TRAILER_LEN SRTP_MAX_TAG_LEN 

 /* 

  * nota bene: since libSRTP doesn't support the use of the MKI, the

  * SRTP_MAX_TRAILER_LEN value is just the maximum tag length

  */

 /**

  * @brief sec_serv_t describes a set of security services. 

  *

  * A sec_serv_t enumeration is used to describe the particular

  * security services that will be applied by a particular crypto

  * policy (or other mechanism).  

  */

 typedef enum {

   sec_serv_none          = 0, /**< no services                        */

   sec_serv_conf          = 1, /**< confidentiality                    */

   sec_serv_auth          = 2, /**< authentication                     */

   sec_serv_conf_and_auth = 3  /**< confidentiality and authentication */

 } sec_serv_t;

 /** 

  * @brief crypto_policy_t describes a particular crypto policy that

  * can be applied to an SRTP stream.

  *

  * A crypto_policy_t describes a particular cryptographic policy that

  * can be applied to an SRTP or SRTCP stream.  An SRTP session policy

  * consists of a list of these policies, one for each SRTP stream 

  * in the session.

  */

 typedef struct crypto_policy_t {

   cipher_type_id_t cipher_type;    /**< An integer representing

 				    *   the type of cipher.  */

   int              cipher_key_len; /**< The length of the cipher key

 				    *   in octets.                       */

   auth_type_id_t   auth_type;      /**< An integer representing the

 				    *   authentication function.         */

   int              auth_key_len;   /**< The length of the authentication 

 				    *   function key in octets.          */

   int              auth_tag_len;   /**< The length of the authentication 

 				    *   tag in octets.                   */

   sec_serv_t       sec_serv;       /**< The flag indicating the security

 				    *   services to be applied.          */

 } crypto_policy_t;

 /** 

  * @brief ssrc_type_t describes the type of an SSRC.

  * 

  * An ssrc_type_t enumeration is used to indicate a type of SSRC.  See

  * @ref srtp_policy_t for more informataion.

  */

 typedef enum { 

   ssrc_undefined    = 0,  /**< Indicates an undefined SSRC type. */

   ssrc_specific     = 1,  /**< Indicates a specific SSRC value   */

   ssrc_any_inbound  = 2, /**< Indicates any inbound SSRC value 

 			    (i.e. a value that is used in the

 			    function srtp_unprotect())              */

   ssrc_any_outbound = 3  /**< Indicates any outbound SSRC value 

 			    (i.e. a value that is used in the 

 			    function srtp_protect())		  */

 } ssrc_type_t;

 /**

  * @brief An ssrc_t represents a particular SSRC value, or a `wildcard' SSRC.

  * 

  * An ssrc_t represents a particular SSRC value (if its type is

  * ssrc_specific), or a wildcard SSRC value that will match all

  * outbound SSRCs (if its type is ssrc_any_outbound) or all inbound

  * SSRCs (if its type is ssrc_any_inbound).  

  *

  */

 typedef struct { 

   ssrc_type_t type;   /**< The type of this particular SSRC */

   unsigned int value; /**< The value of this SSRC, if it is not a wildcard */

 } ssrc_t;

 /**

  * @brief points to an EKT policy

  */

 typedef struct ekt_policy_ctx_t *ekt_policy_t;

 /**

  * @brief points to EKT stream data

  */

 typedef struct ekt_stream_ctx_t *ekt_stream_t;

 /** 

  * @brief represents the policy for an SRTP session.  

  *

  * A single srtp_policy_t struct represents the policy for a single

  * SRTP stream, and a linked list of these elements represents the

  * policy for an entire SRTP session.  Each element contains the SRTP

  * and SRTCP crypto policies for that stream, a pointer to the SRTP

  * master key for that stream, the SSRC describing that stream, or a

  * flag indicating a `wildcard' SSRC value, and a `next' field that

  * holds a pointer to the next element in the list of policy elements,

  * or NULL if it is the last element. 

  *

  * The wildcard value SSRC_ANY_INBOUND matches any SSRC from an

  * inbound stream that for which there is no explicit SSRC entry in

  * another policy element.  Similarly, the value SSRC_ANY_OUTBOUND

  * will matches any SSRC from an outbound stream that does not appear

  * in another policy element.  Note that wildcard SSRCs &b cannot be

  * used to match both inbound and outbound traffic.  This restriction

  * is intentional, and it allows libSRTP to ensure that no security

  * lapses result from accidental re-use of SSRC values during key

  * sharing.

  * 

  * 

  * @warning The final element of the list @b must have its `next' pointer

  *          set to NULL.

  */

 typedef struct srtp_policy_t {

   ssrc_t        ssrc;        /**< The SSRC value of stream, or the 

 			      *   flags SSRC_ANY_INBOUND or 

 			      *   SSRC_ANY_OUTBOUND if key sharing

 			      *   is used for this policy element.

 			      */

   crypto_policy_t rtp;         /**< SRTP crypto policy.                  */

   crypto_policy_t rtcp;        /**< SRTCP crypto policy.                 */

   unsigned char *key;          /**< Pointer to the SRTP master key for

 				*    this stream.                        */

   ekt_policy_t ekt;            /**< Pointer to the EKT policy structure

                                 *   for this stream (if any)             */ 

   unsigned long window_size;   /**< The window size to use for replay

 				*   protection. */

   int        allow_repeat_tx;  /**< Whether retransmissions of

 				*   packets with the same sequence number

 				*   are allowed.  (Note that such repeated

 				*   transmissions must have the same RTP

 				*   payload, or a severe security weakness

 				*   is introduced!)                      */

   struct srtp_policy_t *next;  /**< Pointer to next stream policy.       */

 } srtp_policy_t;

 /**

  * @brief An srtp_t points to an SRTP session structure.

  *

  * The typedef srtp_t is a pointer to a structure that represents

  * an SRTP session.  This datatype is intentially opaque in 

  * order to separate the interface from the implementation.

  *

  * An SRTP session consists of all of the traffic sent to the RTP and

  * RTCP destination transport addresses, using the RTP/SAVP (Secure

  * Audio/Video Profile).  A session can be viewed as a set of SRTP

  * streams, each of which originates with a different participant.

  */

 typedef struct srtp_ctx_t *srtp_t;

 /**

  * @brief An srtp_stream_t points to an SRTP stream structure.

  *

  * The typedef srtp_stream_t is a pointer to a structure that

  * represents an SRTP stream.  This datatype is intentionally

  * opaque in order to separate the interface from the implementation. 

  * 

  * An SRTP stream consists of all of the traffic sent to an SRTP

  * session by a single participant.  A session can be viewed as

  * a set of streams.  

  *

  */

 typedef struct srtp_stream_ctx_t *srtp_stream_t;

 /**

  * @brief srtp_init() initializes the srtp library.  

  *

  * @warning This function @b must be called before any other srtp

  * functions.

  */

 err_status_t

 srtp_init(void);

 /**

  * @brief srtp_shutdown() de-initializes the srtp library.

  *

  * @warning No srtp functions may be called after calling this function.

  */

 err_status_t

 srtp_shutdown(void);

 /**

  * @brief srtp_protect() is the Secure RTP sender-side packet processing

  * function.

  * 

  * The function call srtp_protect(ctx, rtp_hdr, len_ptr) applies SRTP

  * protection to the RTP packet rtp_hdr (which has length *len_ptr) using

  * the SRTP context ctx.  If err_status_ok is returned, then rtp_hdr

  * points to the resulting SRTP packet and *len_ptr is the number of

  * octets in that packet; otherwise, no assumptions should be made

  * about the value of either data elements.

  * 

  * The sequence numbers of the RTP packets presented to this function

  * need not be consecutive, but they @b must be out of order by less

  * than 2^15 = 32,768 packets.

  *

  * @warning This function assumes that it can write the authentication

  * tag into the location in memory immediately following the RTP

  * packet, and assumes that the RTP packet is aligned on a 32-bit

  * boundary.

  *

  * @param ctx is the SRTP context to use in processing the packet.

  *

  * @param rtp_hdr is a pointer to the RTP packet (before the call); after

  * the function returns, it points to the srtp packet.

  *

  * @param len_ptr is a pointer to the length in octets of the complete

  * RTP packet (header and body) before the function call, and of the

  * complete SRTP packet after the call, if err_status_ok was returned.

  * Otherwise, the value of the data to which it points is undefined.

  *

  * @return 

  *    - err_status_ok            no problems

  *    - err_status_replay_fail   rtp sequence number was non-increasing

  *    - @e other                 failure in cryptographic mechanisms

  */

 err_status_t

 srtp_protect(srtp_t ctx, void *rtp_hdr, int *len_ptr);

 /**

  * @brief srtp_unprotect() is the Secure RTP receiver-side packet

  * processing function.

  *

  * The function call srtp_unprotect(ctx, srtp_hdr, len_ptr) verifies

  * the Secure RTP protection of the SRTP packet pointed to by srtp_hdr

  * (which has length *len_ptr), using the SRTP context ctx.  If

  * err_status_ok is returned, then srtp_hdr points to the resulting

  * RTP packet and *len_ptr is the number of octets in that packet;

  * otherwise, no assumptions should be made about the value of either

  * data elements.  

  * 

  * The sequence numbers of the RTP packets presented to this function

  * need not be consecutive, but they @b must be out of order by less

  * than 2^15 = 32,768 packets.

  * 

  * @warning This function assumes that the SRTP packet is aligned on a

  * 32-bit boundary.

  *

  * @param ctx is a pointer to the srtp_t which applies to the

  * particular packet.

  *

  * @param srtp_hdr is a pointer to the header of the SRTP packet

  * (before the call).  after the function returns, it points to the

  * rtp packet if err_status_ok was returned; otherwise, the value of

  * the data to which it points is undefined.

  *

  * @param len_ptr is a pointer to the length in octets of the complete

  * srtp packet (header and body) before the function call, and of the

  * complete rtp packet after the call, if err_status_ok was returned.

  * Otherwise, the value of the data to which it points is undefined.

  *

  * @return 

  *    - err_status_ok          if the RTP packet is valid.

  *    - err_status_auth_fail   if the SRTP packet failed the message 

  *                             authentication check.

  *    - err_status_replay_fail if the SRTP packet is a replay (e.g. packet has

  *                             already been processed and accepted).

  *    - [other]  if there has been an error in the cryptographic mechanisms.

  *

  */

 err_status_t

 srtp_unprotect(srtp_t ctx, void *srtp_hdr, int *len_ptr);

 /**

  * @brief srtp_create() allocates and initializes an SRTP session.

  * The function call srtp_create(session, policy, key) allocates and

  * initializes an SRTP session context, applying the given policy and

  * key.

  *

  * @param session is the SRTP session to which the policy is to be added.

  * 

  * @param policy is the srtp_policy_t struct that describes the policy

  * for the session.  The struct may be a single element, or it may be

  * the head of a list, in which case each element of the list is

  * processed.  It may also be NULL, in which case streams should be added

  * later using srtp_add_stream().  The final element of the list @b must

  * have its `next' field set to NULL.

  * 

  * @return

  *    - err_status_ok           if creation succeded.

  *    - err_status_alloc_fail   if allocation failed.

  *    - err_status_init_fail    if initialization failed.

  */

 err_status_t

 srtp_create(srtp_t *session, const srtp_policy_t *policy);

 /**

  * @brief srtp_add_stream() allocates and initializes an SRTP stream

  * within a given SRTP session.

  * 

  * The function call srtp_add_stream(session, policy) allocates and

  * initializes a new SRTP stream within a given, previously created

  * session, applying the policy given as the other argument to that

  * stream.

  *

  * @return values:

  *    - err_status_ok           if stream creation succeded.

  *    - err_status_alloc_fail   if stream allocation failed

  *    - err_status_init_fail    if stream initialization failed.

  */

 err_status_t

 srtp_add_stream(srtp_t session, 

 		const srtp_policy_t *policy);

 /**

  * @brief srtp_remove_stream() deallocates an SRTP stream.

  * 

  * The function call srtp_remove_stream(session, ssrc) removes

  * the SRTP stream with the SSRC value ssrc from the SRTP session

  * context given by the argument session.

  *

  * @param session is the SRTP session from which the stream

  *        will be removed.

  *

  * @param ssrc is the SSRC value of the stream to be removed.

  *

  * @warning Wildcard SSRC values cannot be removed from a

  *          session.

  * 

  * @return

  *    - err_status_ok     if the stream deallocation succeded.

  *    - [other]           otherwise.

  *

  */

 err_status_t

 srtp_remove_stream(srtp_t session, unsigned int ssrc);

 /**

  * @brief crypto_policy_set_rtp_default() sets a crypto policy

  * structure to the SRTP default policy for RTP protection.

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function call crypto_policy_set_rtp_default(&p) sets the

  * crypto_policy_t at location p to the SRTP default policy for RTP

  * protection, as defined in the specification.  This function is a

  * convenience that helps to avoid dealing directly with the policy

  * data structure.  You are encouraged to initialize policy elements

  * with this function call.  Doing so may allow your code to be

  * forward compatible with later versions of libSRTP that include more

  * elements in the crypto_policy_t datatype.

  * 

  * @return void.

  * 

  */

 void

 crypto_policy_set_rtp_default(crypto_policy_t *p);

 /**

  * @brief crypto_policy_set_rtcp_default() sets a crypto policy

  * structure to the SRTP default policy for RTCP protection.

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function call crypto_policy_set_rtcp_default(&p) sets the

  * crypto_policy_t at location p to the SRTP default policy for RTCP

  * protection, as defined in the specification.  This function is a

  * convenience that helps to avoid dealing directly with the policy

  * data structure.  You are encouraged to initialize policy elements

  * with this function call.  Doing so may allow your code to be

  * forward compatible with later versions of libSRTP that include more

  * elements in the crypto_policy_t datatype.

  * 

  * @return void.

  * 

  */

 void

 crypto_policy_set_rtcp_default(crypto_policy_t *p);

 /**

  * @brief crypto_policy_set_aes_cm_128_hmac_sha1_80() sets a crypto

  * policy structure to the SRTP default policy for RTP protection.

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function crypto_policy_set_aes_cm_128_hmac_sha1_80() is a

  * synonym for crypto_policy_set_rtp_default().  It conforms to the

  * naming convention used in RFC 4568 (SDP Security Descriptions for

  * Media Streams).

  * 

  * @return void.

  * 

  */

 #define crypto_policy_set_aes_cm_128_hmac_sha1_80(p) crypto_policy_set_rtp_default(p)

 /**

  * @brief crypto_policy_set_aes_cm_128_hmac_sha1_32() sets a crypto

  * policy structure to a short-authentication tag policy

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function call crypto_policy_set_aes_cm_128_hmac_sha1_32(&p)

  * sets the crypto_policy_t at location p to use policy

  * AES_CM_128_HMAC_SHA1_32 as defined in RFC 4568.

  * This policy uses AES-128

  * Counter Mode encryption and HMAC-SHA1 authentication, with an

  * authentication tag that is only 32 bits long.  This length is

  * considered adequate only for protecting audio and video media that

  * use a stateless playback function.  See Section 7.5 of RFC 3711

  * (http://www.ietf.org/rfc/rfc3711.txt).

  * 

  * This function is a convenience that helps to avoid dealing directly

  * with the policy data structure.  You are encouraged to initialize

  * policy elements with this function call.  Doing so may allow your

  * code to be forward compatible with later versions of libSRTP that

  * include more elements in the crypto_policy_t datatype.

  *

  * @warning This crypto policy is intended for use in SRTP, but not in

  * SRTCP.  It is recommended that a policy that uses longer

  * authentication tags be used for SRTCP.  See Section 7.5 of RFC 3711

  * (http://www.ietf.org/rfc/rfc3711.txt).

  *

  * @return void.

  * 

  */

 void

 crypto_policy_set_aes_cm_128_hmac_sha1_32(crypto_policy_t *p);

 /**

  * @brief crypto_policy_set_aes_cm_128_null_auth() sets a crypto

  * policy structure to an encryption-only policy

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function call crypto_policy_set_aes_cm_128_null_auth(&p) sets

  * the crypto_policy_t at location p to use the SRTP default cipher

  * (AES-128 Counter Mode), but to use no authentication method.  This

  * policy is NOT RECOMMENDED unless it is unavoidable; see Section 7.5

  * of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).

  * 

  * This function is a convenience that helps to avoid dealing directly

  * with the policy data structure.  You are encouraged to initialize

  * policy elements with this function call.  Doing so may allow your

  * code to be forward compatible with later versions of libSRTP that

  * include more elements in the crypto_policy_t datatype.

  *

  * @warning This policy is NOT RECOMMENDED for SRTP unless it is

  * unavoidable, and it is NOT RECOMMENDED at all for SRTCP; see

  * Section 7.5 of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).

  *

  * @return void.

  * 

  */

 void

 crypto_policy_set_aes_cm_128_null_auth(crypto_policy_t *p);

 /**

  * @brief crypto_policy_set_null_cipher_hmac_sha1_80() sets a crypto

  * policy structure to an authentication-only policy

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function call crypto_policy_set_null_cipher_hmac_sha1_80(&p)

  * sets the crypto_policy_t at location p to use HMAC-SHA1 with an 80

  * bit authentication tag to provide message authentication, but to

  * use no encryption.  This policy is NOT RECOMMENDED for SRTP unless

  * there is a requirement to forego encryption.  

  * 

  * This function is a convenience that helps to avoid dealing directly

  * with the policy data structure.  You are encouraged to initialize

  * policy elements with this function call.  Doing so may allow your

  * code to be forward compatible with later versions of libSRTP that

  * include more elements in the crypto_policy_t datatype.

  *

  * @warning This policy is NOT RECOMMENDED for SRTP unless there is a

  * requirement to forego encryption.  

  *

  * @return void.

  * 

  */

 void

 crypto_policy_set_null_cipher_hmac_sha1_80(crypto_policy_t *p);

 /**

  * @brief crypto_policy_set_aes_cm_256_hmac_sha1_80() sets a crypto

  * policy structure to a encryption and authentication policy using AES-256 

  * for RTP protection.

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function call crypto_policy_set_aes_cm_256_hmac_sha1_80(&p)

  * sets the crypto_policy_t at location p to use policy

  * AES_CM_256_HMAC_SHA1_80 as defined in

  * draft-ietf-avt-srtp-big-aes-03.txt.  This policy uses AES-256

  * Counter Mode encryption and HMAC-SHA1 authentication, with an 80 bit

  * authentication tag.

  * 

  * This function is a convenience that helps to avoid dealing directly

  * with the policy data structure.  You are encouraged to initialize

  * policy elements with this function call.  Doing so may allow your

  * code to be forward compatible with later versions of libSRTP that

  * include more elements in the crypto_policy_t datatype.

  *

  * @return void.

  * 

  */

 void crypto_policy_set_aes_cm_256_hmac_sha1_80(crypto_policy_t *p);

 /**

  * @brief crypto_policy_set_aes_cm_256_hmac_sha1_32() sets a crypto

  * policy structure to a short-authentication tag policy using AES-256

  * encryption.

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function call crypto_policy_set_aes_cm_256_hmac_sha1_32(&p)

  * sets the crypto_policy_t at location p to use policy

  * AES_CM_256_HMAC_SHA1_32 as defined in

  * draft-ietf-avt-srtp-big-aes-03.txt.  This policy uses AES-256

  * Counter Mode encryption and HMAC-SHA1 authentication, with an

  * authentication tag that is only 32 bits long.  This length is

  * considered adequate only for protecting audio and video media that

  * use a stateless playback function.  See Section 7.5 of RFC 3711

  * (http://www.ietf.org/rfc/rfc3711.txt).

  * 

  * This function is a convenience that helps to avoid dealing directly

  * with the policy data structure.  You are encouraged to initialize

  * policy elements with this function call.  Doing so may allow your

  * code to be forward compatible with later versions of libSRTP that

  * include more elements in the crypto_policy_t datatype.

  *

  * @warning This crypto policy is intended for use in SRTP, but not in

  * SRTCP.  It is recommended that a policy that uses longer

  * authentication tags be used for SRTCP.  See Section 7.5 of RFC 3711

  * (http://www.ietf.org/rfc/rfc3711.txt).

  *

  * @return void.

  * 

  */

 void

 crypto_policy_set_aes_cm_256_hmac_sha1_32(crypto_policy_t *p);

 /**

  * @brief srtp_dealloc() deallocates storage for an SRTP session

  * context.

  * 

  * The function call srtp_dealloc(s) deallocates storage for the

  * SRTP session context s.  This function should be called no more

  * than one time for each of the contexts allocated by the function

  * srtp_create().

  *

  * @param s is the srtp_t for the session to be deallocated.

  *

  * @return

  *    - err_status_ok             if there no problems.

  *    - err_status_dealloc_fail   a memory deallocation failure occured.

  */

 err_status_t

 srtp_dealloc(srtp_t s);

 /*

  * @brief identifies a particular SRTP profile 

  *

  * An srtp_profile_t enumeration is used to identify a particular SRTP

  * profile (that is, a set of algorithms and parameters).  These

  * profiles are defined in the DTLS-SRTP draft.

  */

 typedef enum {

   srtp_profile_reserved           = 0,

   srtp_profile_aes128_cm_sha1_80  = 1,

   srtp_profile_aes128_cm_sha1_32  = 2,

   srtp_profile_aes256_cm_sha1_80  = 3,

   srtp_profile_aes256_cm_sha1_32  = 4,

   srtp_profile_null_sha1_80       = 5,

   srtp_profile_null_sha1_32       = 6,

 } srtp_profile_t;

 /**

  * @brief crypto_policy_set_from_profile_for_rtp() sets a crypto policy

  * structure to the appropriate value for RTP based on an srtp_profile_t

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function call crypto_policy_set_rtp_default(&policy, profile)

  * sets the crypto_policy_t at location policy to the policy for RTP

  * protection, as defined by the srtp_profile_t profile.

  * 

  * This function is a convenience that helps to avoid dealing directly

  * with the policy data structure.  You are encouraged to initialize

  * policy elements with this function call.  Doing so may allow your

  * code to be forward compatible with later versions of libSRTP that

  * include more elements in the crypto_policy_t datatype.

  * 

  * @return values

  *     - err_status_ok         no problems were encountered

  *     - err_status_bad_param  the profile is not supported 

  * 

  */

 err_status_t

 crypto_policy_set_from_profile_for_rtp(crypto_policy_t *policy, 

 				       srtp_profile_t profile);

 /**

  * @brief crypto_policy_set_from_profile_for_rtcp() sets a crypto policy

  * structure to the appropriate value for RTCP based on an srtp_profile_t

  *

  * @param p is a pointer to the policy structure to be set 

  * 

  * The function call crypto_policy_set_rtcp_default(&policy, profile)

  * sets the crypto_policy_t at location policy to the policy for RTCP

  * protection, as defined by the srtp_profile_t profile.

  * 

  * This function is a convenience that helps to avoid dealing directly

  * with the policy data structure.  You are encouraged to initialize

  * policy elements with this function call.  Doing so may allow your

  * code to be forward compatible with later versions of libSRTP that

  * include more elements in the crypto_policy_t datatype.

  * 

  * @return values

  *     - err_status_ok         no problems were encountered

  *     - err_status_bad_param  the profile is not supported 

  * 

  */

 err_status_t

 crypto_policy_set_from_profile_for_rtcp(crypto_policy_t *policy, 

 				       srtp_profile_t profile);

 /**

  * @brief returns the master key length for a given SRTP profile

  */

 unsigned int

 srtp_profile_get_master_key_length(srtp_profile_t profile);

 /**

  * @brief returns the master salt length for a given SRTP profile

  */

 unsigned int

 srtp_profile_get_master_salt_length(srtp_profile_t profile);

 /**

  * @brief appends the salt to the key

  *

  * The function call append_salt_to_key(k, klen, s, slen) 

  * copies the string s to the location at klen bytes following

  * the location k.  

  *

  * @warning There must be at least bytes_in_salt + bytes_in_key bytes

  *          available at the location pointed to by key.

  * 

  */

 void

 append_salt_to_key(unsigned char *key, unsigned int bytes_in_key,

 		   unsigned char *salt, unsigned int bytes_in_salt);

 /**

  * @}

  */

 /**

  * @defgroup SRTCP Secure RTCP

  * @ingroup  SRTP 

  *

  * @brief Secure RTCP functions are used to protect RTCP traffic.

  *

  * RTCP is the control protocol for RTP.  libSRTP protects RTCP

  * traffic in much the same way as it does RTP traffic.  The function

  * srtp_protect_rtcp() applies cryptographic protections to outbound

  * RTCP packets, and srtp_unprotect_rtcp() verifies the protections on

  * inbound RTCP packets.  

  *

  * A note on the naming convention: srtp_protect_rtcp() has an srtp_t

  * as its first argument, and thus has `srtp_' as its prefix.  The

  * trailing `_rtcp' indicates the protocol on which it acts.  

  * 

  * @{

  */

 /**

  * @brief srtp_protect_rtcp() is the Secure RTCP sender-side packet

  * processing function.

  * 

  * The function call srtp_protect_rtcp(ctx, rtp_hdr, len_ptr) applies

  * SRTCP protection to the RTCP packet rtcp_hdr (which has length

  * *len_ptr) using the SRTP session context ctx.  If err_status_ok is

  * returned, then rtp_hdr points to the resulting SRTCP packet and

  * *len_ptr is the number of octets in that packet; otherwise, no

  * assumptions should be made about the value of either data elements.

  * 

  * @warning This function assumes that it can write the authentication

  * tag into the location in memory immediately following the RTCP

  * packet, and assumes that the RTCP packet is aligned on a 32-bit

  * boundary.

  *

  * @param ctx is the SRTP context to use in processing the packet.

  *

  * @param rtcp_hdr is a pointer to the RTCP packet (before the call); after

  * the function returns, it points to the srtp packet.

  *

  * @param pkt_octet_len is a pointer to the length in octets of the

  * complete RTCP packet (header and body) before the function call,

  * and of the complete SRTCP packet after the call, if err_status_ok

  * was returned.  Otherwise, the value of the data to which it points

  * is undefined.

  *

  * @return 

  *    - err_status_ok            if there were no problems.

  *    - [other]                  if there was a failure in 

  *                               the cryptographic mechanisms.

  */

 err_status_t 

 srtp_protect_rtcp(srtp_t ctx, void *rtcp_hdr, int *pkt_octet_len);

 /**

  * @brief srtp_unprotect_rtcp() is the Secure RTCP receiver-side packet

  * processing function.

  *

  * The function call srtp_unprotect_rtcp(ctx, srtp_hdr, len_ptr)

  * verifies the Secure RTCP protection of the SRTCP packet pointed to

  * by srtcp_hdr (which has length *len_ptr), using the SRTP session

  * context ctx.  If err_status_ok is returned, then srtcp_hdr points

  * to the resulting RTCP packet and *len_ptr is the number of octets

  * in that packet; otherwise, no assumptions should be made about the

  * value of either data elements.

  * 

  * @warning This function assumes that the SRTCP packet is aligned on a

  * 32-bit boundary.

  *

  * @param ctx is a pointer to the srtp_t which applies to the

  * particular packet.

  *

  * @param srtcp_hdr is a pointer to the header of the SRTCP packet

  * (before the call).  After the function returns, it points to the

  * rtp packet if err_status_ok was returned; otherwise, the value of

  * the data to which it points is undefined.

  *

  * @param pkt_octet_len is a pointer to the length in octets of the

  * complete SRTCP packet (header and body) before the function call,

  * and of the complete rtp packet after the call, if err_status_ok was

  * returned.  Otherwise, the value of the data to which it points is

  * undefined.

  *

  * @return 

  *    - err_status_ok          if the RTCP packet is valid.

  *    - err_status_auth_fail   if the SRTCP packet failed the message 

  *                             authentication check.

  *    - err_status_replay_fail if the SRTCP packet is a replay (e.g. has

  *                             already been processed and accepted).

  *    - [other]  if there has been an error in the cryptographic mechanisms.

  *

  */

 err_status_t 

 srtp_unprotect_rtcp(srtp_t ctx, void *srtcp_hdr, int *pkt_octet_len);

 /**

  * @}

  */

 /**

  * @defgroup SRTPevents SRTP events and callbacks

  * @ingroup  SRTP

  *

  * @brief libSRTP can use a user-provided callback function to 

  * handle events.

  *

  * 

  * libSRTP allows a user to provide a callback function to handle

  * events that need to be dealt with outside of the data plane (see

  * the enum srtp_event_t for a description of these events).  Dealing

  * with these events is not a strict necessity; they are not

  * security-critical, but the application may suffer if they are not

  * handled.  The function srtp_set_event_handler() is used to provide

  * the callback function.

  *

  * A default event handler that merely reports on the events as they

  * happen is included.  It is also possible to set the event handler

  * function to NULL, in which case all events will just be silently

  * ignored.

  *

  * @{

  */

 /**

  * @brief srtp_event_t defines events that need to be handled

  *

  * The enum srtp_event_t defines events that need to be handled

  * outside the `data plane', such as SSRC collisions and 

  * key expirations.  

  *

  * When a key expires or the maximum number of packets has been

  * reached, an SRTP stream will enter an `expired' state in which no

  * more packets can be protected or unprotected.  When this happens,

  * it is likely that you will want to either deallocate the stream

  * (using srtp_stream_dealloc()), and possibly allocate a new one.

  *

  * When an SRTP stream expires, the other streams in the same session

  * are unaffected, unless key sharing is used by that stream.  In the

  * latter case, all of the streams in the session will expire.

  */

 typedef enum { 

   event_ssrc_collision,    /**<

 			    * An SSRC collision occured.             

 			    */

   event_key_soft_limit,    /**< An SRTP stream reached the soft key

 			    *   usage limit and will expire soon.	   

 			    */

   event_key_hard_limit,    /**< An SRTP stream reached the hard 

 			    *   key usage limit and has expired.

 			    */

   event_packet_index_limit /**< An SRTP stream reached the hard 

 			    * packet limit (2^48 packets).             

 			    */

 } srtp_event_t;

 /**

  * @brief srtp_event_data_t is the structure passed as a callback to 

  * the event handler function

  *

  * The struct srtp_event_data_t holds the data passed to the event

  * handler function.  

  */

 typedef struct srtp_event_data_t {

   srtp_t        session;  /**< The session in which the event happend. */

   srtp_stream_t stream;   /**< The stream in which the event happend.  */

   srtp_event_t  event;    /**< An enum indicating the type of event.   */

 } srtp_event_data_t;

 /**

  * @brief srtp_event_handler_func_t is the function prototype for

  * the event handler.

  *

  * The typedef srtp_event_handler_func_t is the prototype for the

  * event handler function.  It has as its only argument an

  * srtp_event_data_t which describes the event that needs to be handled.

  * There can only be a single, global handler for all events in

  * libSRTP.

  */

 typedef void (srtp_event_handler_func_t)(srtp_event_data_t *data);

 /**

  * @brief sets the event handler to the function supplied by the caller.

  * 

  * The function call srtp_install_event_handler(func) sets the event

  * handler function to the value func.  The value NULL is acceptable

  * as an argument; in this case, events will be ignored rather than

  * handled.

  *

  * @param func is a pointer to a fuction that takes an srtp_event_data_t

  *             pointer as an argument and returns void.  This function

  *             will be used by libSRTP to handle events.

  */

 err_status_t

 srtp_install_event_handler(srtp_event_handler_func_t func);

 /**

  * @}

  */

 /* in host order, so outside the #if */

 #define SRTCP_E_BIT      0x80000000

 /* for byte-access */

 #define SRTCP_E_BYTE_BIT 0x80

 #define SRTCP_INDEX_MASK 0x7fffffff

 #ifdef __cplusplus

 }

 #endif

 #endif /* SRTP_H */