SSL_set_tlsext_use_srtp (3)
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NAME
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
SYNOPSIS
#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);
DESCRIPTION
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:
SRTP_AES128_CM_SHA1_80
-
This corresponds to
SRTP_AES128_CM_HMAC_SHA1_80
defined in RFC5764.
SRTP_AES128_CM_SHA1_32
-
This corresponds to
SRTP_AES128_CM_HMAC_SHA1_32
defined in RFC5764.
SRTP_AEAD_AES_128_GCM
-
This corresponds to the profile of the same name defined in
RFC7714.
SRTP_AEAD_AES_256_GCM
-
This corresponds to the profile of the same name defined in
RFC7714.
Supplying an unrecognised protection profile name will result in an error.
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 sucessfully 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.
RETURN VALUES
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
otherwise.
SEE ALSO
SSL_export_keying_material(3)
COPYRIGHT
Copyright 2017 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
<
www.openssl.org/source/license.html>.