michael@0: /*
michael@0:  * srtp.h
michael@0:  *
michael@0:  * interface to libsrtp
michael@0:  *
michael@0:  * David A. McGrew
michael@0:  * Cisco Systems, Inc.
michael@0:  */
michael@0: /*
michael@0:  *	
michael@0:  * Copyright (c) 2001-2006, Cisco Systems, Inc.
michael@0:  * All rights reserved.
michael@0:  * 
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  * 
michael@0:  *   Redistributions of source code must retain the above copyright
michael@0:  *   notice, this list of conditions and the following disclaimer.
michael@0:  * 
michael@0:  *   Redistributions in binary form must reproduce the above
michael@0:  *   copyright notice, this list of conditions and the following
michael@0:  *   disclaimer in the documentation and/or other materials provided
michael@0:  *   with the distribution.
michael@0:  * 
michael@0:  *   Neither the name of the Cisco Systems, Inc. nor the names of its
michael@0:  *   contributors may be used to endorse or promote products derived
michael@0:  *   from this software without specific prior written permission.
michael@0:  * 
michael@0:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0:  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0:  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
michael@0:  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
michael@0:  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
michael@0:  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
michael@0:  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
michael@0:  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
michael@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
michael@0:  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
michael@0:  * OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: 
michael@0: #ifndef SRTP_H
michael@0: #define SRTP_H
michael@0: 
michael@0: #ifdef __cplusplus
michael@0: extern "C" {
michael@0: #endif
michael@0: 
michael@0: #include "crypto_kernel.h" 
michael@0: 
michael@0: /**
michael@0:  * @defgroup SRTP Secure RTP
michael@0:  *
michael@0:  * @brief libSRTP provides functions for protecting RTP and RTCP.  See
michael@0:  * Section @ref Overview for an introduction to the use of the library.
michael@0:  *
michael@0:  * @{
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  * SRTP_MASTER_KEY_LEN is the nominal master key length supported by libSRTP
michael@0:  */
michael@0: 
michael@0: #define SRTP_MASTER_KEY_LEN 30
michael@0: 
michael@0: /*
michael@0:  * SRTP_MAX_KEY_LEN is the maximum key length supported by libSRTP
michael@0:  */
michael@0: #define SRTP_MAX_KEY_LEN      64
michael@0: 
michael@0: /*
michael@0:  * SRTP_MAX_TAG_LEN is the maximum tag length supported by libSRTP
michael@0:  */
michael@0: 
michael@0: #define SRTP_MAX_TAG_LEN 12 
michael@0: 
michael@0: /**
michael@0:  * SRTP_MAX_TRAILER_LEN is the maximum length of the SRTP trailer
michael@0:  * (authentication tag and MKI) supported by libSRTP.  This value is
michael@0:  * the maximum number of octets that will be added to an RTP packet by
michael@0:  * srtp_protect().
michael@0:  *
michael@0:  * @brief the maximum number of octets added by srtp_protect().
michael@0:  */
michael@0: #define SRTP_MAX_TRAILER_LEN SRTP_MAX_TAG_LEN 
michael@0: 
michael@0: /* 
michael@0:  * nota bene: since libSRTP doesn't support the use of the MKI, the
michael@0:  * SRTP_MAX_TRAILER_LEN value is just the maximum tag length
michael@0:  */
michael@0: 
michael@0: /**
michael@0:  * @brief sec_serv_t describes a set of security services. 
michael@0:  *
michael@0:  * A sec_serv_t enumeration is used to describe the particular
michael@0:  * security services that will be applied by a particular crypto
michael@0:  * policy (or other mechanism).  
michael@0:  */
michael@0: 
michael@0: typedef enum {
michael@0:   sec_serv_none          = 0, /**< no services                        */
michael@0:   sec_serv_conf          = 1, /**< confidentiality                    */
michael@0:   sec_serv_auth          = 2, /**< authentication                     */
michael@0:   sec_serv_conf_and_auth = 3  /**< confidentiality and authentication */
michael@0: } sec_serv_t;
michael@0: 
michael@0: /** 
michael@0:  * @brief crypto_policy_t describes a particular crypto policy that
michael@0:  * can be applied to an SRTP stream.
michael@0:  *
michael@0:  * A crypto_policy_t describes a particular cryptographic policy that
michael@0:  * can be applied to an SRTP or SRTCP stream.  An SRTP session policy
michael@0:  * consists of a list of these policies, one for each SRTP stream 
michael@0:  * in the session.
michael@0:  */
michael@0: 
michael@0: typedef struct crypto_policy_t {
michael@0:   cipher_type_id_t cipher_type;    /**< An integer representing
michael@0: 				    *   the type of cipher.  */
michael@0:   int              cipher_key_len; /**< The length of the cipher key
michael@0: 				    *   in octets.                       */
michael@0:   auth_type_id_t   auth_type;      /**< An integer representing the
michael@0: 				    *   authentication function.         */
michael@0:   int              auth_key_len;   /**< The length of the authentication 
michael@0: 				    *   function key in octets.          */
michael@0:   int              auth_tag_len;   /**< The length of the authentication 
michael@0: 				    *   tag in octets.                   */
michael@0:   sec_serv_t       sec_serv;       /**< The flag indicating the security
michael@0: 				    *   services to be applied.          */
michael@0: } crypto_policy_t;
michael@0: 
michael@0: 
michael@0: /** 
michael@0:  * @brief ssrc_type_t describes the type of an SSRC.
michael@0:  * 
michael@0:  * An ssrc_type_t enumeration is used to indicate a type of SSRC.  See
michael@0:  * @ref srtp_policy_t for more informataion.
michael@0:  */
michael@0: 
michael@0: typedef enum { 
michael@0:   ssrc_undefined    = 0,  /**< Indicates an undefined SSRC type. */
michael@0:   ssrc_specific     = 1,  /**< Indicates a specific SSRC value   */
michael@0:   ssrc_any_inbound  = 2, /**< Indicates any inbound SSRC value 
michael@0: 			    (i.e. a value that is used in the
michael@0: 			    function srtp_unprotect())              */
michael@0:   ssrc_any_outbound = 3  /**< Indicates any outbound SSRC value 
michael@0: 			    (i.e. a value that is used in the 
michael@0: 			    function srtp_protect())		  */
michael@0: } ssrc_type_t;
michael@0: 
michael@0: /**
michael@0:  * @brief An ssrc_t represents a particular SSRC value, or a `wildcard' SSRC.
michael@0:  * 
michael@0:  * An ssrc_t represents a particular SSRC value (if its type is
michael@0:  * ssrc_specific), or a wildcard SSRC value that will match all
michael@0:  * outbound SSRCs (if its type is ssrc_any_outbound) or all inbound
michael@0:  * SSRCs (if its type is ssrc_any_inbound).  
michael@0:  *
michael@0:  */
michael@0: 
michael@0: typedef struct { 
michael@0:   ssrc_type_t type;   /**< The type of this particular SSRC */
michael@0:   unsigned int value; /**< The value of this SSRC, if it is not a wildcard */
michael@0: } ssrc_t;
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief points to an EKT policy
michael@0:  */
michael@0: typedef struct ekt_policy_ctx_t *ekt_policy_t;
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief points to EKT stream data
michael@0:  */
michael@0: typedef struct ekt_stream_ctx_t *ekt_stream_t;
michael@0: 
michael@0: 
michael@0: /** 
michael@0:  * @brief represents the policy for an SRTP session.  
michael@0:  *
michael@0:  * A single srtp_policy_t struct represents the policy for a single
michael@0:  * SRTP stream, and a linked list of these elements represents the
michael@0:  * policy for an entire SRTP session.  Each element contains the SRTP
michael@0:  * and SRTCP crypto policies for that stream, a pointer to the SRTP
michael@0:  * master key for that stream, the SSRC describing that stream, or a
michael@0:  * flag indicating a `wildcard' SSRC value, and a `next' field that
michael@0:  * holds a pointer to the next element in the list of policy elements,
michael@0:  * or NULL if it is the last element. 
michael@0:  *
michael@0:  * The wildcard value SSRC_ANY_INBOUND matches any SSRC from an
michael@0:  * inbound stream that for which there is no explicit SSRC entry in
michael@0:  * another policy element.  Similarly, the value SSRC_ANY_OUTBOUND
michael@0:  * will matches any SSRC from an outbound stream that does not appear
michael@0:  * in another policy element.  Note that wildcard SSRCs &b cannot be
michael@0:  * used to match both inbound and outbound traffic.  This restriction
michael@0:  * is intentional, and it allows libSRTP to ensure that no security
michael@0:  * lapses result from accidental re-use of SSRC values during key
michael@0:  * sharing.
michael@0:  * 
michael@0:  * 
michael@0:  * @warning The final element of the list @b must have its `next' pointer
michael@0:  *          set to NULL.
michael@0:  */
michael@0: 
michael@0: typedef struct srtp_policy_t {
michael@0:   ssrc_t        ssrc;        /**< The SSRC value of stream, or the 
michael@0: 			      *   flags SSRC_ANY_INBOUND or 
michael@0: 			      *   SSRC_ANY_OUTBOUND if key sharing
michael@0: 			      *   is used for this policy element.
michael@0: 			      */
michael@0:   crypto_policy_t rtp;         /**< SRTP crypto policy.                  */
michael@0:   crypto_policy_t rtcp;        /**< SRTCP crypto policy.                 */
michael@0:   unsigned char *key;          /**< Pointer to the SRTP master key for
michael@0: 				*    this stream.                        */
michael@0:   ekt_policy_t ekt;            /**< Pointer to the EKT policy structure
michael@0:                                 *   for this stream (if any)             */ 
michael@0:   unsigned long window_size;   /**< The window size to use for replay
michael@0: 				*   protection. */
michael@0:   int        allow_repeat_tx;  /**< Whether retransmissions of
michael@0: 				*   packets with the same sequence number
michael@0: 				*   are allowed.  (Note that such repeated
michael@0: 				*   transmissions must have the same RTP
michael@0: 				*   payload, or a severe security weakness
michael@0: 				*   is introduced!)                      */
michael@0:   struct srtp_policy_t *next;  /**< Pointer to next stream policy.       */
michael@0: } srtp_policy_t;
michael@0: 
michael@0: 
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief An srtp_t points to an SRTP session structure.
michael@0:  *
michael@0:  * The typedef srtp_t is a pointer to a structure that represents
michael@0:  * an SRTP session.  This datatype is intentially opaque in 
michael@0:  * order to separate the interface from the implementation.
michael@0:  *
michael@0:  * An SRTP session consists of all of the traffic sent to the RTP and
michael@0:  * RTCP destination transport addresses, using the RTP/SAVP (Secure
michael@0:  * Audio/Video Profile).  A session can be viewed as a set of SRTP
michael@0:  * streams, each of which originates with a different participant.
michael@0:  */
michael@0: 
michael@0: typedef struct srtp_ctx_t *srtp_t;
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief An srtp_stream_t points to an SRTP stream structure.
michael@0:  *
michael@0:  * The typedef srtp_stream_t is a pointer to a structure that
michael@0:  * represents an SRTP stream.  This datatype is intentionally
michael@0:  * opaque in order to separate the interface from the implementation. 
michael@0:  * 
michael@0:  * An SRTP stream consists of all of the traffic sent to an SRTP
michael@0:  * session by a single participant.  A session can be viewed as
michael@0:  * a set of streams.  
michael@0:  *
michael@0:  */
michael@0: typedef struct srtp_stream_ctx_t *srtp_stream_t;
michael@0: 
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_init() initializes the srtp library.  
michael@0:  *
michael@0:  * @warning This function @b must be called before any other srtp
michael@0:  * functions.
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_init(void);
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_shutdown() de-initializes the srtp library.
michael@0:  *
michael@0:  * @warning No srtp functions may be called after calling this function.
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_shutdown(void);
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_protect() is the Secure RTP sender-side packet processing
michael@0:  * function.
michael@0:  * 
michael@0:  * The function call srtp_protect(ctx, rtp_hdr, len_ptr) applies SRTP
michael@0:  * protection to the RTP packet rtp_hdr (which has length *len_ptr) using
michael@0:  * the SRTP context ctx.  If err_status_ok is returned, then rtp_hdr
michael@0:  * points to the resulting SRTP packet and *len_ptr is the number of
michael@0:  * octets in that packet; otherwise, no assumptions should be made
michael@0:  * about the value of either data elements.
michael@0:  * 
michael@0:  * The sequence numbers of the RTP packets presented to this function
michael@0:  * need not be consecutive, but they @b must be out of order by less
michael@0:  * than 2^15 = 32,768 packets.
michael@0:  *
michael@0:  * @warning This function assumes that it can write the authentication
michael@0:  * tag into the location in memory immediately following the RTP
michael@0:  * packet, and assumes that the RTP packet is aligned on a 32-bit
michael@0:  * boundary.
michael@0:  *
michael@0:  * @param ctx is the SRTP context to use in processing the packet.
michael@0:  *
michael@0:  * @param rtp_hdr is a pointer to the RTP packet (before the call); after
michael@0:  * the function returns, it points to the srtp packet.
michael@0:  *
michael@0:  * @param len_ptr is a pointer to the length in octets of the complete
michael@0:  * RTP packet (header and body) before the function call, and of the
michael@0:  * complete SRTP packet after the call, if err_status_ok was returned.
michael@0:  * Otherwise, the value of the data to which it points is undefined.
michael@0:  *
michael@0:  * @return 
michael@0:  *    - err_status_ok            no problems
michael@0:  *    - err_status_replay_fail   rtp sequence number was non-increasing
michael@0:  *    - @e other                 failure in cryptographic mechanisms
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_protect(srtp_t ctx, void *rtp_hdr, int *len_ptr);
michael@0: 	     
michael@0: /**
michael@0:  * @brief srtp_unprotect() is the Secure RTP receiver-side packet
michael@0:  * processing function.
michael@0:  *
michael@0:  * The function call srtp_unprotect(ctx, srtp_hdr, len_ptr) verifies
michael@0:  * the Secure RTP protection of the SRTP packet pointed to by srtp_hdr
michael@0:  * (which has length *len_ptr), using the SRTP context ctx.  If
michael@0:  * err_status_ok is returned, then srtp_hdr points to the resulting
michael@0:  * RTP packet and *len_ptr is the number of octets in that packet;
michael@0:  * otherwise, no assumptions should be made about the value of either
michael@0:  * data elements.  
michael@0:  * 
michael@0:  * The sequence numbers of the RTP packets presented to this function
michael@0:  * need not be consecutive, but they @b must be out of order by less
michael@0:  * than 2^15 = 32,768 packets.
michael@0:  * 
michael@0:  * @warning This function assumes that the SRTP packet is aligned on a
michael@0:  * 32-bit boundary.
michael@0:  *
michael@0:  * @param ctx is a pointer to the srtp_t which applies to the
michael@0:  * particular packet.
michael@0:  *
michael@0:  * @param srtp_hdr is a pointer to the header of the SRTP packet
michael@0:  * (before the call).  after the function returns, it points to the
michael@0:  * rtp packet if err_status_ok was returned; otherwise, the value of
michael@0:  * the data to which it points is undefined.
michael@0:  *
michael@0:  * @param len_ptr is a pointer to the length in octets of the complete
michael@0:  * srtp packet (header and body) before the function call, and of the
michael@0:  * complete rtp packet after the call, if err_status_ok was returned.
michael@0:  * Otherwise, the value of the data to which it points is undefined.
michael@0:  *
michael@0:  * @return 
michael@0:  *    - err_status_ok          if the RTP packet is valid.
michael@0:  *    - err_status_auth_fail   if the SRTP packet failed the message 
michael@0:  *                             authentication check.
michael@0:  *    - err_status_replay_fail if the SRTP packet is a replay (e.g. packet has
michael@0:  *                             already been processed and accepted).
michael@0:  *    - [other]  if there has been an error in the cryptographic mechanisms.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_unprotect(srtp_t ctx, void *srtp_hdr, int *len_ptr);
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_create() allocates and initializes an SRTP session.
michael@0: 
michael@0:  * The function call srtp_create(session, policy, key) allocates and
michael@0:  * initializes an SRTP session context, applying the given policy and
michael@0:  * key.
michael@0:  *
michael@0:  * @param session is the SRTP session to which the policy is to be added.
michael@0:  * 
michael@0:  * @param policy is the srtp_policy_t struct that describes the policy
michael@0:  * for the session.  The struct may be a single element, or it may be
michael@0:  * the head of a list, in which case each element of the list is
michael@0:  * processed.  It may also be NULL, in which case streams should be added
michael@0:  * later using srtp_add_stream().  The final element of the list @b must
michael@0:  * have its `next' field set to NULL.
michael@0:  * 
michael@0:  * @return
michael@0:  *    - err_status_ok           if creation succeded.
michael@0:  *    - err_status_alloc_fail   if allocation failed.
michael@0:  *    - err_status_init_fail    if initialization failed.
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_create(srtp_t *session, const srtp_policy_t *policy);
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_add_stream() allocates and initializes an SRTP stream
michael@0:  * within a given SRTP session.
michael@0:  * 
michael@0:  * The function call srtp_add_stream(session, policy) allocates and
michael@0:  * initializes a new SRTP stream within a given, previously created
michael@0:  * session, applying the policy given as the other argument to that
michael@0:  * stream.
michael@0:  *
michael@0:  * @return values:
michael@0:  *    - err_status_ok           if stream creation succeded.
michael@0:  *    - err_status_alloc_fail   if stream allocation failed
michael@0:  *    - err_status_init_fail    if stream initialization failed.
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_add_stream(srtp_t session, 
michael@0: 		const srtp_policy_t *policy);
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_remove_stream() deallocates an SRTP stream.
michael@0:  * 
michael@0:  * The function call srtp_remove_stream(session, ssrc) removes
michael@0:  * the SRTP stream with the SSRC value ssrc from the SRTP session
michael@0:  * context given by the argument session.
michael@0:  *
michael@0:  * @param session is the SRTP session from which the stream
michael@0:  *        will be removed.
michael@0:  *
michael@0:  * @param ssrc is the SSRC value of the stream to be removed.
michael@0:  *
michael@0:  * @warning Wildcard SSRC values cannot be removed from a
michael@0:  *          session.
michael@0:  * 
michael@0:  * @return
michael@0:  *    - err_status_ok     if the stream deallocation succeded.
michael@0:  *    - [other]           otherwise.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_remove_stream(srtp_t session, unsigned int ssrc);
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_rtp_default() sets a crypto policy
michael@0:  * structure to the SRTP default policy for RTP protection.
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function call crypto_policy_set_rtp_default(&p) sets the
michael@0:  * crypto_policy_t at location p to the SRTP default policy for RTP
michael@0:  * protection, as defined in the specification.  This function is a
michael@0:  * convenience that helps to avoid dealing directly with the policy
michael@0:  * data structure.  You are encouraged to initialize policy elements
michael@0:  * with this function call.  Doing so may allow your code to be
michael@0:  * forward compatible with later versions of libSRTP that include more
michael@0:  * elements in the crypto_policy_t datatype.
michael@0:  * 
michael@0:  * @return void.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: void
michael@0: crypto_policy_set_rtp_default(crypto_policy_t *p);
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_rtcp_default() sets a crypto policy
michael@0:  * structure to the SRTP default policy for RTCP protection.
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function call crypto_policy_set_rtcp_default(&p) sets the
michael@0:  * crypto_policy_t at location p to the SRTP default policy for RTCP
michael@0:  * protection, as defined in the specification.  This function is a
michael@0:  * convenience that helps to avoid dealing directly with the policy
michael@0:  * data structure.  You are encouraged to initialize policy elements
michael@0:  * with this function call.  Doing so may allow your code to be
michael@0:  * forward compatible with later versions of libSRTP that include more
michael@0:  * elements in the crypto_policy_t datatype.
michael@0:  * 
michael@0:  * @return void.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: void
michael@0: crypto_policy_set_rtcp_default(crypto_policy_t *p);
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_aes_cm_128_hmac_sha1_80() sets a crypto
michael@0:  * policy structure to the SRTP default policy for RTP protection.
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function crypto_policy_set_aes_cm_128_hmac_sha1_80() is a
michael@0:  * synonym for crypto_policy_set_rtp_default().  It conforms to the
michael@0:  * naming convention used in RFC 4568 (SDP Security Descriptions for
michael@0:  * Media Streams).
michael@0:  * 
michael@0:  * @return void.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: #define crypto_policy_set_aes_cm_128_hmac_sha1_80(p) crypto_policy_set_rtp_default(p)
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_aes_cm_128_hmac_sha1_32() sets a crypto
michael@0:  * policy structure to a short-authentication tag policy
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function call crypto_policy_set_aes_cm_128_hmac_sha1_32(&p)
michael@0:  * sets the crypto_policy_t at location p to use policy
michael@0:  * AES_CM_128_HMAC_SHA1_32 as defined in RFC 4568.
michael@0:  * This policy uses AES-128
michael@0:  * Counter Mode encryption and HMAC-SHA1 authentication, with an
michael@0:  * authentication tag that is only 32 bits long.  This length is
michael@0:  * considered adequate only for protecting audio and video media that
michael@0:  * use a stateless playback function.  See Section 7.5 of RFC 3711
michael@0:  * (http://www.ietf.org/rfc/rfc3711.txt).
michael@0:  * 
michael@0:  * This function is a convenience that helps to avoid dealing directly
michael@0:  * with the policy data structure.  You are encouraged to initialize
michael@0:  * policy elements with this function call.  Doing so may allow your
michael@0:  * code to be forward compatible with later versions of libSRTP that
michael@0:  * include more elements in the crypto_policy_t datatype.
michael@0:  *
michael@0:  * @warning This crypto policy is intended for use in SRTP, but not in
michael@0:  * SRTCP.  It is recommended that a policy that uses longer
michael@0:  * authentication tags be used for SRTCP.  See Section 7.5 of RFC 3711
michael@0:  * (http://www.ietf.org/rfc/rfc3711.txt).
michael@0:  *
michael@0:  * @return void.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: void
michael@0: crypto_policy_set_aes_cm_128_hmac_sha1_32(crypto_policy_t *p);
michael@0: 
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_aes_cm_128_null_auth() sets a crypto
michael@0:  * policy structure to an encryption-only policy
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function call crypto_policy_set_aes_cm_128_null_auth(&p) sets
michael@0:  * the crypto_policy_t at location p to use the SRTP default cipher
michael@0:  * (AES-128 Counter Mode), but to use no authentication method.  This
michael@0:  * policy is NOT RECOMMENDED unless it is unavoidable; see Section 7.5
michael@0:  * of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
michael@0:  * 
michael@0:  * This function is a convenience that helps to avoid dealing directly
michael@0:  * with the policy data structure.  You are encouraged to initialize
michael@0:  * policy elements with this function call.  Doing so may allow your
michael@0:  * code to be forward compatible with later versions of libSRTP that
michael@0:  * include more elements in the crypto_policy_t datatype.
michael@0:  *
michael@0:  * @warning This policy is NOT RECOMMENDED for SRTP unless it is
michael@0:  * unavoidable, and it is NOT RECOMMENDED at all for SRTCP; see
michael@0:  * Section 7.5 of RFC 3711 (http://www.ietf.org/rfc/rfc3711.txt).
michael@0:  *
michael@0:  * @return void.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: void
michael@0: crypto_policy_set_aes_cm_128_null_auth(crypto_policy_t *p);
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_null_cipher_hmac_sha1_80() sets a crypto
michael@0:  * policy structure to an authentication-only policy
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function call crypto_policy_set_null_cipher_hmac_sha1_80(&p)
michael@0:  * sets the crypto_policy_t at location p to use HMAC-SHA1 with an 80
michael@0:  * bit authentication tag to provide message authentication, but to
michael@0:  * use no encryption.  This policy is NOT RECOMMENDED for SRTP unless
michael@0:  * there is a requirement to forego encryption.  
michael@0:  * 
michael@0:  * This function is a convenience that helps to avoid dealing directly
michael@0:  * with the policy data structure.  You are encouraged to initialize
michael@0:  * policy elements with this function call.  Doing so may allow your
michael@0:  * code to be forward compatible with later versions of libSRTP that
michael@0:  * include more elements in the crypto_policy_t datatype.
michael@0:  *
michael@0:  * @warning This policy is NOT RECOMMENDED for SRTP unless there is a
michael@0:  * requirement to forego encryption.  
michael@0:  *
michael@0:  * @return void.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: void
michael@0: crypto_policy_set_null_cipher_hmac_sha1_80(crypto_policy_t *p);
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_aes_cm_256_hmac_sha1_80() sets a crypto
michael@0:  * policy structure to a encryption and authentication policy using AES-256 
michael@0:  * for RTP protection.
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function call crypto_policy_set_aes_cm_256_hmac_sha1_80(&p)
michael@0:  * sets the crypto_policy_t at location p to use policy
michael@0:  * AES_CM_256_HMAC_SHA1_80 as defined in
michael@0:  * draft-ietf-avt-srtp-big-aes-03.txt.  This policy uses AES-256
michael@0:  * Counter Mode encryption and HMAC-SHA1 authentication, with an 80 bit
michael@0:  * authentication tag.
michael@0:  * 
michael@0:  * This function is a convenience that helps to avoid dealing directly
michael@0:  * with the policy data structure.  You are encouraged to initialize
michael@0:  * policy elements with this function call.  Doing so may allow your
michael@0:  * code to be forward compatible with later versions of libSRTP that
michael@0:  * include more elements in the crypto_policy_t datatype.
michael@0:  *
michael@0:  * @return void.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: void crypto_policy_set_aes_cm_256_hmac_sha1_80(crypto_policy_t *p);
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_aes_cm_256_hmac_sha1_32() sets a crypto
michael@0:  * policy structure to a short-authentication tag policy using AES-256
michael@0:  * encryption.
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function call crypto_policy_set_aes_cm_256_hmac_sha1_32(&p)
michael@0:  * sets the crypto_policy_t at location p to use policy
michael@0:  * AES_CM_256_HMAC_SHA1_32 as defined in
michael@0:  * draft-ietf-avt-srtp-big-aes-03.txt.  This policy uses AES-256
michael@0:  * Counter Mode encryption and HMAC-SHA1 authentication, with an
michael@0:  * authentication tag that is only 32 bits long.  This length is
michael@0:  * considered adequate only for protecting audio and video media that
michael@0:  * use a stateless playback function.  See Section 7.5 of RFC 3711
michael@0:  * (http://www.ietf.org/rfc/rfc3711.txt).
michael@0:  * 
michael@0:  * This function is a convenience that helps to avoid dealing directly
michael@0:  * with the policy data structure.  You are encouraged to initialize
michael@0:  * policy elements with this function call.  Doing so may allow your
michael@0:  * code to be forward compatible with later versions of libSRTP that
michael@0:  * include more elements in the crypto_policy_t datatype.
michael@0:  *
michael@0:  * @warning This crypto policy is intended for use in SRTP, but not in
michael@0:  * SRTCP.  It is recommended that a policy that uses longer
michael@0:  * authentication tags be used for SRTCP.  See Section 7.5 of RFC 3711
michael@0:  * (http://www.ietf.org/rfc/rfc3711.txt).
michael@0:  *
michael@0:  * @return void.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: void
michael@0: crypto_policy_set_aes_cm_256_hmac_sha1_32(crypto_policy_t *p);
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_dealloc() deallocates storage for an SRTP session
michael@0:  * context.
michael@0:  * 
michael@0:  * The function call srtp_dealloc(s) deallocates storage for the
michael@0:  * SRTP session context s.  This function should be called no more
michael@0:  * than one time for each of the contexts allocated by the function
michael@0:  * srtp_create().
michael@0:  *
michael@0:  * @param s is the srtp_t for the session to be deallocated.
michael@0:  *
michael@0:  * @return
michael@0:  *    - err_status_ok             if there no problems.
michael@0:  *    - err_status_dealloc_fail   a memory deallocation failure occured.
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_dealloc(srtp_t s);
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * @brief identifies a particular SRTP profile 
michael@0:  *
michael@0:  * An srtp_profile_t enumeration is used to identify a particular SRTP
michael@0:  * profile (that is, a set of algorithms and parameters).  These
michael@0:  * profiles are defined in the DTLS-SRTP draft.
michael@0:  */
michael@0: 
michael@0: typedef enum {
michael@0:   srtp_profile_reserved           = 0,
michael@0:   srtp_profile_aes128_cm_sha1_80  = 1,
michael@0:   srtp_profile_aes128_cm_sha1_32  = 2,
michael@0:   srtp_profile_aes256_cm_sha1_80  = 3,
michael@0:   srtp_profile_aes256_cm_sha1_32  = 4,
michael@0:   srtp_profile_null_sha1_80       = 5,
michael@0:   srtp_profile_null_sha1_32       = 6,
michael@0: } srtp_profile_t;
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_from_profile_for_rtp() sets a crypto policy
michael@0:  * structure to the appropriate value for RTP based on an srtp_profile_t
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function call crypto_policy_set_rtp_default(&policy, profile)
michael@0:  * sets the crypto_policy_t at location policy to the policy for RTP
michael@0:  * protection, as defined by the srtp_profile_t profile.
michael@0:  * 
michael@0:  * This function is a convenience that helps to avoid dealing directly
michael@0:  * with the policy data structure.  You are encouraged to initialize
michael@0:  * policy elements with this function call.  Doing so may allow your
michael@0:  * code to be forward compatible with later versions of libSRTP that
michael@0:  * include more elements in the crypto_policy_t datatype.
michael@0:  * 
michael@0:  * @return values
michael@0:  *     - err_status_ok         no problems were encountered
michael@0:  *     - err_status_bad_param  the profile is not supported 
michael@0:  * 
michael@0:  */
michael@0: err_status_t
michael@0: crypto_policy_set_from_profile_for_rtp(crypto_policy_t *policy, 
michael@0: 				       srtp_profile_t profile);
michael@0: 
michael@0: 
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief crypto_policy_set_from_profile_for_rtcp() sets a crypto policy
michael@0:  * structure to the appropriate value for RTCP based on an srtp_profile_t
michael@0:  *
michael@0:  * @param p is a pointer to the policy structure to be set 
michael@0:  * 
michael@0:  * The function call crypto_policy_set_rtcp_default(&policy, profile)
michael@0:  * sets the crypto_policy_t at location policy to the policy for RTCP
michael@0:  * protection, as defined by the srtp_profile_t profile.
michael@0:  * 
michael@0:  * This function is a convenience that helps to avoid dealing directly
michael@0:  * with the policy data structure.  You are encouraged to initialize
michael@0:  * policy elements with this function call.  Doing so may allow your
michael@0:  * code to be forward compatible with later versions of libSRTP that
michael@0:  * include more elements in the crypto_policy_t datatype.
michael@0:  * 
michael@0:  * @return values
michael@0:  *     - err_status_ok         no problems were encountered
michael@0:  *     - err_status_bad_param  the profile is not supported 
michael@0:  * 
michael@0:  */
michael@0: err_status_t
michael@0: crypto_policy_set_from_profile_for_rtcp(crypto_policy_t *policy, 
michael@0: 				       srtp_profile_t profile);
michael@0: 
michael@0: /**
michael@0:  * @brief returns the master key length for a given SRTP profile
michael@0:  */
michael@0: unsigned int
michael@0: srtp_profile_get_master_key_length(srtp_profile_t profile);
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @brief returns the master salt length for a given SRTP profile
michael@0:  */
michael@0: unsigned int
michael@0: srtp_profile_get_master_salt_length(srtp_profile_t profile);
michael@0: 
michael@0: /**
michael@0:  * @brief appends the salt to the key
michael@0:  *
michael@0:  * The function call append_salt_to_key(k, klen, s, slen) 
michael@0:  * copies the string s to the location at klen bytes following
michael@0:  * the location k.  
michael@0:  *
michael@0:  * @warning There must be at least bytes_in_salt + bytes_in_key bytes
michael@0:  *          available at the location pointed to by key.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: void
michael@0: append_salt_to_key(unsigned char *key, unsigned int bytes_in_key,
michael@0: 		   unsigned char *salt, unsigned int bytes_in_salt);
michael@0: 
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @}
michael@0:  */
michael@0: 
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * @defgroup SRTCP Secure RTCP
michael@0:  * @ingroup  SRTP 
michael@0:  *
michael@0:  * @brief Secure RTCP functions are used to protect RTCP traffic.
michael@0:  *
michael@0:  * RTCP is the control protocol for RTP.  libSRTP protects RTCP
michael@0:  * traffic in much the same way as it does RTP traffic.  The function
michael@0:  * srtp_protect_rtcp() applies cryptographic protections to outbound
michael@0:  * RTCP packets, and srtp_unprotect_rtcp() verifies the protections on
michael@0:  * inbound RTCP packets.  
michael@0:  *
michael@0:  * A note on the naming convention: srtp_protect_rtcp() has an srtp_t
michael@0:  * as its first argument, and thus has `srtp_' as its prefix.  The
michael@0:  * trailing `_rtcp' indicates the protocol on which it acts.  
michael@0:  * 
michael@0:  * @{
michael@0:  */
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_protect_rtcp() is the Secure RTCP sender-side packet
michael@0:  * processing function.
michael@0:  * 
michael@0:  * The function call srtp_protect_rtcp(ctx, rtp_hdr, len_ptr) applies
michael@0:  * SRTCP protection to the RTCP packet rtcp_hdr (which has length
michael@0:  * *len_ptr) using the SRTP session context ctx.  If err_status_ok is
michael@0:  * returned, then rtp_hdr points to the resulting SRTCP packet and
michael@0:  * *len_ptr is the number of octets in that packet; otherwise, no
michael@0:  * assumptions should be made about the value of either data elements.
michael@0:  * 
michael@0:  * @warning This function assumes that it can write the authentication
michael@0:  * tag into the location in memory immediately following the RTCP
michael@0:  * packet, and assumes that the RTCP packet is aligned on a 32-bit
michael@0:  * boundary.
michael@0:  *
michael@0:  * @param ctx is the SRTP context to use in processing the packet.
michael@0:  *
michael@0:  * @param rtcp_hdr is a pointer to the RTCP packet (before the call); after
michael@0:  * the function returns, it points to the srtp packet.
michael@0:  *
michael@0:  * @param pkt_octet_len is a pointer to the length in octets of the
michael@0:  * complete RTCP packet (header and body) before the function call,
michael@0:  * and of the complete SRTCP packet after the call, if err_status_ok
michael@0:  * was returned.  Otherwise, the value of the data to which it points
michael@0:  * is undefined.
michael@0:  *
michael@0:  * @return 
michael@0:  *    - err_status_ok            if there were no problems.
michael@0:  *    - [other]                  if there was a failure in 
michael@0:  *                               the cryptographic mechanisms.
michael@0:  */
michael@0: 	     
michael@0: 
michael@0: err_status_t 
michael@0: srtp_protect_rtcp(srtp_t ctx, void *rtcp_hdr, int *pkt_octet_len);
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_unprotect_rtcp() is the Secure RTCP receiver-side packet
michael@0:  * processing function.
michael@0:  *
michael@0:  * The function call srtp_unprotect_rtcp(ctx, srtp_hdr, len_ptr)
michael@0:  * verifies the Secure RTCP protection of the SRTCP packet pointed to
michael@0:  * by srtcp_hdr (which has length *len_ptr), using the SRTP session
michael@0:  * context ctx.  If err_status_ok is returned, then srtcp_hdr points
michael@0:  * to the resulting RTCP packet and *len_ptr is the number of octets
michael@0:  * in that packet; otherwise, no assumptions should be made about the
michael@0:  * value of either data elements.
michael@0:  * 
michael@0:  * @warning This function assumes that the SRTCP packet is aligned on a
michael@0:  * 32-bit boundary.
michael@0:  *
michael@0:  * @param ctx is a pointer to the srtp_t which applies to the
michael@0:  * particular packet.
michael@0:  *
michael@0:  * @param srtcp_hdr is a pointer to the header of the SRTCP packet
michael@0:  * (before the call).  After the function returns, it points to the
michael@0:  * rtp packet if err_status_ok was returned; otherwise, the value of
michael@0:  * the data to which it points is undefined.
michael@0:  *
michael@0:  * @param pkt_octet_len is a pointer to the length in octets of the
michael@0:  * complete SRTCP packet (header and body) before the function call,
michael@0:  * and of the complete rtp packet after the call, if err_status_ok was
michael@0:  * returned.  Otherwise, the value of the data to which it points is
michael@0:  * undefined.
michael@0:  *
michael@0:  * @return 
michael@0:  *    - err_status_ok          if the RTCP packet is valid.
michael@0:  *    - err_status_auth_fail   if the SRTCP packet failed the message 
michael@0:  *                             authentication check.
michael@0:  *    - err_status_replay_fail if the SRTCP packet is a replay (e.g. has
michael@0:  *                             already been processed and accepted).
michael@0:  *    - [other]  if there has been an error in the cryptographic mechanisms.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: err_status_t 
michael@0: srtp_unprotect_rtcp(srtp_t ctx, void *srtcp_hdr, int *pkt_octet_len);
michael@0: 
michael@0: /**
michael@0:  * @}
michael@0:  */
michael@0: 
michael@0: /**
michael@0:  * @defgroup SRTPevents SRTP events and callbacks
michael@0:  * @ingroup  SRTP
michael@0:  *
michael@0:  * @brief libSRTP can use a user-provided callback function to 
michael@0:  * handle events.
michael@0:  *
michael@0:  * 
michael@0:  * libSRTP allows a user to provide a callback function to handle
michael@0:  * events that need to be dealt with outside of the data plane (see
michael@0:  * the enum srtp_event_t for a description of these events).  Dealing
michael@0:  * with these events is not a strict necessity; they are not
michael@0:  * security-critical, but the application may suffer if they are not
michael@0:  * handled.  The function srtp_set_event_handler() is used to provide
michael@0:  * the callback function.
michael@0:  *
michael@0:  * A default event handler that merely reports on the events as they
michael@0:  * happen is included.  It is also possible to set the event handler
michael@0:  * function to NULL, in which case all events will just be silently
michael@0:  * ignored.
michael@0:  *
michael@0:  * @{
michael@0:  */
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_event_t defines events that need to be handled
michael@0:  *
michael@0:  * The enum srtp_event_t defines events that need to be handled
michael@0:  * outside the `data plane', such as SSRC collisions and 
michael@0:  * key expirations.  
michael@0:  *
michael@0:  * When a key expires or the maximum number of packets has been
michael@0:  * reached, an SRTP stream will enter an `expired' state in which no
michael@0:  * more packets can be protected or unprotected.  When this happens,
michael@0:  * it is likely that you will want to either deallocate the stream
michael@0:  * (using srtp_stream_dealloc()), and possibly allocate a new one.
michael@0:  *
michael@0:  * When an SRTP stream expires, the other streams in the same session
michael@0:  * are unaffected, unless key sharing is used by that stream.  In the
michael@0:  * latter case, all of the streams in the session will expire.
michael@0:  */
michael@0: 
michael@0: typedef enum { 
michael@0:   event_ssrc_collision,    /**<
michael@0: 			    * An SSRC collision occured.             
michael@0: 			    */
michael@0:   event_key_soft_limit,    /**< An SRTP stream reached the soft key
michael@0: 			    *   usage limit and will expire soon.	   
michael@0: 			    */
michael@0:   event_key_hard_limit,    /**< An SRTP stream reached the hard 
michael@0: 			    *   key usage limit and has expired.
michael@0: 			    */
michael@0:   event_packet_index_limit /**< An SRTP stream reached the hard 
michael@0: 			    * packet limit (2^48 packets).             
michael@0: 			    */
michael@0: } srtp_event_t;
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_event_data_t is the structure passed as a callback to 
michael@0:  * the event handler function
michael@0:  *
michael@0:  * The struct srtp_event_data_t holds the data passed to the event
michael@0:  * handler function.  
michael@0:  */
michael@0: 
michael@0: typedef struct srtp_event_data_t {
michael@0:   srtp_t        session;  /**< The session in which the event happend. */
michael@0:   srtp_stream_t stream;   /**< The stream in which the event happend.  */
michael@0:   srtp_event_t  event;    /**< An enum indicating the type of event.   */
michael@0: } srtp_event_data_t;
michael@0: 
michael@0: /**
michael@0:  * @brief srtp_event_handler_func_t is the function prototype for
michael@0:  * the event handler.
michael@0:  *
michael@0:  * The typedef srtp_event_handler_func_t is the prototype for the
michael@0:  * event handler function.  It has as its only argument an
michael@0:  * srtp_event_data_t which describes the event that needs to be handled.
michael@0:  * There can only be a single, global handler for all events in
michael@0:  * libSRTP.
michael@0:  */
michael@0: 
michael@0: typedef void (srtp_event_handler_func_t)(srtp_event_data_t *data);
michael@0: 
michael@0: /**
michael@0:  * @brief sets the event handler to the function supplied by the caller.
michael@0:  * 
michael@0:  * The function call srtp_install_event_handler(func) sets the event
michael@0:  * handler function to the value func.  The value NULL is acceptable
michael@0:  * as an argument; in this case, events will be ignored rather than
michael@0:  * handled.
michael@0:  *
michael@0:  * @param func is a pointer to a fuction that takes an srtp_event_data_t
michael@0:  *             pointer as an argument and returns void.  This function
michael@0:  *             will be used by libSRTP to handle events.
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_install_event_handler(srtp_event_handler_func_t func);
michael@0: 
michael@0: /**
michael@0:  * @}
michael@0:  */
michael@0: /* in host order, so outside the #if */
michael@0: #define SRTCP_E_BIT      0x80000000
michael@0: /* for byte-access */
michael@0: #define SRTCP_E_BYTE_BIT 0x80
michael@0: #define SRTCP_INDEX_MASK 0x7fffffff
michael@0: 
michael@0: #ifdef __cplusplus
michael@0: }
michael@0: #endif
michael@0: 
michael@0: #endif /* SRTP_H */