/* * 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. * * @warning This function assumes that it can write SRTP_MAX_TRAILER_LEN * into the location in memory immediately following the RTP packet. * Callers MUST ensure that this much writable memory is available in * the buffer that holds the RTP packet. * * @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. * * @warning This function assumes that it can write SRTP_MAX_TRAILER_LEN+4 * into the location in memory immediately following the RTCP packet. * Callers MUST ensure that this much writable memory is available in * the buffer that holds the RTCP packet. * * @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 */