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.\" ========================================================================
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.IX Title "SSL_CTX_SET_TLSEXT_USE_SRTP 3ossl"
.TH SSL_CTX_SET_TLSEXT_USE_SRTP 3ossl "2023-09-19" "3.0.11" "OpenSSL"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "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
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\s-1SRTP\s0 is the Secure Real-Time Transport Protocol. OpenSSL implements support for
the \*(L"use_srtp\*(R" \s-1DTLS\s0 extension defined in \s-1RFC5764.\s0 This provides a mechanism for
establishing \s-1SRTP\s0 keying material, algorithms and parameters using \s-1DTLS.\s0 This
capability may be used as part of an implementation that conforms to \s-1RFC5763.\s0
OpenSSL does not implement \s-1SRTP\s0 itself or \s-1RFC5763.\s0 Note that OpenSSL does not
support the use of \s-1SRTP\s0 Master Key Identifiers (MKIs). Also note that this
extension is only supported in \s-1DTLS.\s0 Any \s-1SRTP\s0 configuration will be ignored if a
\&\s-1TLS\s0 connection is attempted.
.PP
An OpenSSL client wishing to send the \*(L"use_srtp\*(R" extension should call
\&\fBSSL_CTX_set_tlsext_use_srtp()\fR to set its use for all \s-1SSL\s0 objects subsequently
created from an \s-1SSL_CTX.\s0 Alternatively a client may call
\&\fBSSL_set_tlsext_use_srtp()\fR to set its use for an individual \s-1SSL\s0 object. The
\&\fBprofiles\fR parameters should point to a NUL-terminated, colon delimited list of
\&\s-1SRTP\s0 protection profile names.
.PP
The currently supported protection profile names are:
.IP "\s-1SRTP_AES128_CM_SHA1_80\s0" 4
.IX Item "SRTP_AES128_CM_SHA1_80"
This corresponds to \s-1SRTP_AES128_CM_HMAC_SHA1_80\s0 defined in \s-1RFC5764.\s0
.IP "\s-1SRTP_AES128_CM_SHA1_32\s0" 4
.IX Item "SRTP_AES128_CM_SHA1_32"
This corresponds to \s-1SRTP_AES128_CM_HMAC_SHA1_32\s0 defined in \s-1RFC5764.\s0
.IP "\s-1SRTP_AEAD_AES_128_GCM\s0" 4
.IX Item "SRTP_AEAD_AES_128_GCM"
This corresponds to the profile of the same name defined in \s-1RFC7714.\s0
.IP "\s-1SRTP_AEAD_AES_256_GCM\s0" 4
.IX Item "SRTP_AEAD_AES_256_GCM"
This corresponds to the profile of the same name defined in \s-1RFC7714.\s0
.PP
Supplying an unrecognised protection profile name will result in an error.
.PP
An OpenSSL server wishing to support the \*(L"use_srtp\*(R" extension should also call
\&\fBSSL_CTX_set_tlsext_use_srtp()\fR or \fBSSL_set_tlsext_use_srtp()\fR to indicate the
protection profiles that it is willing to negotiate.
.PP
The currently configured list of protection profiles for either a client or a
server can be obtained by calling \fBSSL_get_srtp_profiles()\fR. This returns a stack
of \s-1SRTP_PROTECTION_PROFILE\s0 objects. The memory pointed to in the return value of
this function should not be freed by the caller.
.PP
After a handshake has been completed the negotiated \s-1SRTP\s0 protection profile (if
any) can be obtained (on the client or the server) by calling
\&\fBSSL_get_selected_srtp_profile()\fR. This function will return \s-1NULL\s0 if no \s-1SRTP\s0
protection profile was negotiated. The memory returned from this function should
not be freed by the caller.
.PP
If an \s-1SRTP\s0 protection profile has been successfully negotiated then the \s-1SRTP\s0
keying material (on both the client and server) should be obtained via a call to
\&\fBSSL_export_keying_material\fR\|(3). This call should provide a label value of
\&\*(L"EXTRACTOR\-dtls_srtp\*(R" and a \s-1NULL\s0 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.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBSSL_CTX_set_tlsext_use_srtp()\fR and \fBSSL_set_tlsext_use_srtp()\fR return 0 on success
or 1 on error.
.PP
\&\fBSSL_get_srtp_profiles()\fR returns a stack of \s-1SRTP_PROTECTION_PROFILE\s0 objects on
success or \s-1NULL\s0 on error or if no protection profiles have been configured.
.PP
\&\fBSSL_get_selected_srtp_profile()\fR returns a pointer to an \s-1SRTP_PROTECTION_PROFILE\s0
object if one has been negotiated or \s-1NULL\s0 otherwise.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBssl\fR\|(7),
\&\fBSSL_export_keying_material\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2017\-2018 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.
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