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freeswitch/libs/srtp/include/srtp.h

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/*
* srtp.h
*
* interface to libsrtp
*
* David A. McGrew
* Cisco Systems, Inc.
*/
/*
*
* Copyright (c) 2001-2005, 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
#ifdef _MSC_VER
#pragma warning(disable:4214)
#endif
#include "crypto_kernel.h"
#include "rdbx.h"
#include "rdb.h"
#include "integers.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 */
uint32_t value; /**< The value of this SSRC, if it is not a wildcard */
} ssrc_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. */
uint8_t *key; /**< Pointer to the SRTP master key for
* this stream. */
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_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, uint32_t 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 strucutre to be set to the
* default policy.
*
* 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 strucutre to be set to the
* default policy.
*
* 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 strucutre to be set to the
* default policy.
*
* 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
* http://www.ietf.org/internet-drafts/draft-ietf-mmusic-sdescriptions-12.txt
*
* @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 strucutre to be set to the
* default policy.
*
* 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
* draft-ietf-mmusic-sdescriptions-12.txt. 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 strucutre to be set to the
* default policy.
*
* 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 strucutre to be set to the
* default policy.
*
* 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 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);
/**
* @}
*/
/*
* the following declarations are libSRTP internal functions
*/
/*
* srtp_get_stream(ssrc) returns a pointer to the stream corresponding
* to ssrc, or NULL if no stream exists for that ssrc
*/
srtp_stream_t
srtp_get_stream(srtp_t srtp, uint32_t ssrc);
/*
* libsrtp internal datatypes
*/
typedef enum direction_t {
dir_unknown = 0,
dir_srtp_sender = 1,
dir_srtp_receiver = 2
} direction_t;
/*
* an srtp_stream_t has its own SSRC, encryption key, authentication
* key, sequence number, and replay database
*
* note that the keys might not actually be unique, in which case the
* cipher_t and auth_t pointers will point to the same structures
*/
typedef struct srtp_stream_ctx_t {
uint32_t ssrc;
cipher_t *rtp_cipher;
auth_t *rtp_auth;
rdbx_t rtp_rdbx;
sec_serv_t rtp_services;
cipher_t *rtcp_cipher;
auth_t *rtcp_auth;
rdb_t rtcp_rdb;
sec_serv_t rtcp_services;
key_limit_ctx_t *limit;
direction_t direction;
struct srtp_stream_ctx_t *next; /* linked list of streams */
} srtp_stream_ctx_t;
/*
* an srtp_ctx_t holds a stream list and a service description
*/
typedef struct srtp_ctx_t {
srtp_stream_ctx_t *stream_list; /* linked list of streams */
srtp_stream_ctx_t *stream_template; /* act as template for other streams */
} srtp_ctx_t;
/**
* @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);
/**
* @}
*/
/*
* srtp_handle_event(srtp, srtm, evnt) calls the event handling
* function, if there is one.
*
* This macro is not included in the documentation as it is
* an internal-only function.
*/
#define srtp_handle_event(srtp, strm, evnt) \
if(srtp_event_handler) { \
srtp_event_data_t data; \
data.session = srtp; \
data.stream = strm; \
data.event = evnt; \
srtp_event_handler(&data); \
}
/*
* an srtp_hdr_t represents the srtp header
*
* in this implementation, an srtp_hdr_t is assumed to be 32-bit aligned
*
* (note that this definition follows that of RFC 1889 Appendix A, but
* is not identical)
*/
#ifdef _MSC_VER
#pragma pack(push, r1, 1)
#endif
#ifndef WORDS_BIGENDIAN
typedef struct {
unsigned cc:4; /* CSRC count */
unsigned x:1; /* header extension flag */
unsigned p:1; /* padding flag */
unsigned version:2; /* protocol version */
unsigned pt:7; /* payload type */
unsigned m:1; /* marker bit */
unsigned seq:16; /* sequence number */
unsigned ts:32; /* timestamp */
unsigned ssrc:32; /* synchronization source */
} srtp_hdr_t;
#else /* BIG_ENDIAN */
typedef struct {
unsigned version:2; /* protocol version */
unsigned p:1; /* padding flag */
unsigned x:1; /* header extension flag */
unsigned cc:4; /* CSRC count */
unsigned m:1; /* marker bit */
unsigned pt:7; /* payload type */
unsigned seq:16; /* sequence number */
unsigned ts:32; /* timestamp */
unsigned ssrc:32; /* synchronization source */
} srtp_hdr_t;
#endif
typedef struct {
uint16_t profile_specific; /* profile-specific info */
uint16_t length; /* number of 32-bit words in extension */
} srtp_hdr_xtnd_t;
/*
* srtcp_hdr_t represents a secure rtcp header
*
* in this implementation, an srtcp header is assumed to be 32-bit
* alinged
*/
#ifndef WORDS_BIGENDIAN
typedef struct {
unsigned rc:5; /* reception report count */
unsigned p:1; /* padding flag */
unsigned version:2; /* protocol version */
unsigned pt:8; /* payload type */
unsigned len:16; /* length */
unsigned ssrc:32; /* synchronization source */
} srtcp_hdr_t;
typedef struct {
unsigned int index:31; /* srtcp packet index in network order! */
unsigned int e:1; /* encrypted? 1=yes */
/* optional mikey/etc go here */
/* and then the variable-length auth tag */
} srtcp_trailer_t;
#else /* BIG_ENDIAN */
typedef struct {
unsigned version:2; /* protocol version */
unsigned p:1; /* padding flag */
unsigned rc:5; /* reception report count */
unsigned pt:8; /* payload type */
unsigned len:16; /* length */
unsigned ssrc:32; /* synchronization source */
} srtcp_hdr_t;
typedef struct {
unsigned int version:2; /* protocol version */
unsigned int p:1; /* padding flag */
unsigned int count:5; /* varies by packet type */
unsigned int pt:8; /* payload type */
unsigned length:16; /* len of uint32s of packet less header */
} rtcp_common_t;
typedef struct {
unsigned int e:1; /* encrypted? 1=yes */
unsigned int index:31; /* srtcp packet index */
/* optional mikey/etc go here */
/* and then the variable-length auth tag */
} srtcp_trailer_t;
#endif
/* 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 _MSC_VER
#pragma pack(pop, r1)
#endif
#ifdef __cplusplus
}
#endif
#endif /* SRTP_H */
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