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       SSL_CTX_set_tlsext_use_srtp, SSL_set_tlsext_use_srtp,
       SSL_get_srtp_profiles, SSL_get_selected_srtp_profile - Configure	and
       query SRTP support

	#include <openssl/srtp.h>

	int SSL_CTX_set_tlsext_use_srtp(SSL_CTX	*ctx, const char *profiles);
	int SSL_set_tlsext_use_srtp(SSL	*ssl, const char *profiles);

	STACK_OF(SRTP_PROTECTION_PROFILE) *SSL_get_srtp_profiles(SSL *ssl);
	SRTP_PROTECTION_PROFILE	*SSL_get_selected_srtp_profile(SSL *s);

       SRTP is the Secure Real-Time Transport Protocol.	OpenSSL	implements
       support for the "use_srtp" DTLS extension defined in RFC5764. This
       provides	a mechanism for	establishing SRTP keying material, algorithms
       and parameters using DTLS. This capability may be used as part of an
       implementation that conforms to RFC5763.	 OpenSSL does not implement
       SRTP itself or RFC5763. Note that OpenSSL does not support the use of
       SRTP Master Key Identifiers (MKIs). Also	note that this extension is
       only supported in DTLS. Any SRTP	configuration will be ignored if a TLS
       connection is attempted.

       An OpenSSL client wishing to send the "use_srtp"	extension should call
       SSL_CTX_set_tlsext_use_srtp() to	set its	use for	all SSL	objects
       subsequently created from an SSL_CTX. Alternatively a client may	call
       SSL_set_tlsext_use_srtp() to set	its use	for an individual SSL object.
       The profiles parameters should point to a NUL-terminated, colon
       delimited list of SRTP protection profile names.

       The currently supported protection profile names	are:

	   This	corresponds to SRTP_AES128_CM_HMAC_SHA1_80 defined in RFC5764.

	   This	corresponds to SRTP_AES128_CM_HMAC_SHA1_32 defined in RFC5764.

	   This	corresponds to the profile of the same name defined in

	   This	corresponds to the profile of the same name defined in

       Supplying an unrecognised protection profile name will result in	an

       An OpenSSL server wishing to support the	"use_srtp" extension should
       also call SSL_CTX_set_tlsext_use_srtp() or SSL_set_tlsext_use_srtp() to
       indicate	the protection profiles	that it	is willing to negotiate.

       The currently configured	list of	protection profiles for	either a
       client or a server can be obtained by calling SSL_get_srtp_profiles().
       This returns a stack of SRTP_PROTECTION_PROFILE objects.	The memory
       pointed to in the return	value of this function should not be freed by
       the caller.

       After a handshake has been completed the	negotiated SRTP	protection
       profile (if any)	can be obtained	(on the	client or the server) by
       calling SSL_get_selected_srtp_profile().	This function will return NULL
       if no SRTP protection profile was negotiated. The memory	returned from
       this function should not	be freed by the	caller.

       If an SRTP protection profile has been successfully negotiated then the
       SRTP keying material (on	both the client	and server) should be obtained
       via a call to SSL_export_keying_material(3). This call should provide a
       label value of "EXTRACTOR-dtls_srtp" and	a NULL context value
       (use_context is 0). The total length of keying material obtained	should
       be equal	to two times the sum of	the master key length and the salt
       length as defined for the protection profile in use. This provides the
       client write master key,	the server write master	key, the client	write
       master salt and the server write	master salt in that order.

       SSL_CTX_set_tlsext_use_srtp() and SSL_set_tlsext_use_srtp() return 0 on
       success or 1 on error.

       SSL_get_srtp_profiles() returns a stack of SRTP_PROTECTION_PROFILE
       objects on success or NULL on error or if no protection profiles	have
       been configured.

       SSL_get_selected_srtp_profile() returns a pointer to an
       SRTP_PROTECTION_PROFILE object if one has been negotiated or NULL


       Copyright 2017-2018 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the OpenSSL license (the "License").  You	may not	use
       this file except	in compliance with the License.	 You can obtain	a copy
       in the file LICENSE in the source distribution or at

1.1.1k				  2021-03-25	SSL_CTX_SET_TLSEXT_USE_SRTP(3)


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