1=pod
2
3=head1 NAME
4
5SSL_CTX_set_tlsext_use_srtp,
6SSL_set_tlsext_use_srtp,
7SSL_get_srtp_profiles,
8SSL_get_selected_srtp_profile
9- Configure and query SRTP support
10
11=head1 SYNOPSIS
12
13 #include <openssl/srtp.h>
14
15 int SSL_CTX_set_tlsext_use_srtp(SSL_CTX *ctx, const char *profiles);
16 int SSL_set_tlsext_use_srtp(SSL *ssl, const char *profiles);
17
18 STACK_OF(SRTP_PROTECTION_PROFILE) *SSL_get_srtp_profiles(SSL *ssl);
19 SRTP_PROTECTION_PROFILE *SSL_get_selected_srtp_profile(SSL *s);
20
21=head1 DESCRIPTION
22
23SRTP is the Secure Real-Time Transport Protocol. OpenSSL implements support for
24the "use_srtp" DTLS extension defined in RFC5764. This provides a mechanism for
25establishing SRTP keying material, algorithms and parameters using DTLS. This
26capability may be used as part of an implementation that conforms to RFC5763.
27OpenSSL does not implement SRTP itself or RFC5763. Note that OpenSSL does not
28support the use of SRTP Master Key Identifiers (MKIs). Also note that this
29extension is only supported in DTLS. Any SRTP configuration will be ignored if a
30TLS connection is attempted.
31
32An OpenSSL client wishing to send the "use_srtp" extension should call
33SSL_CTX_set_tlsext_use_srtp() to set its use for all SSL objects subsequently
34created from an SSL_CTX. Alternatively a client may call
35SSL_set_tlsext_use_srtp() to set its use for an individual SSL object. The
36B<profiles> parameters should point to a NUL-terminated, colon delimited list of
37SRTP protection profile names.
38
39The currently supported protection profile names are:
40
41=over 4
42
43=item SRTP_AES128_CM_SHA1_80
44
45This corresponds to SRTP_AES128_CM_HMAC_SHA1_80 defined in RFC5764.
46
47=item SRTP_AES128_CM_SHA1_32
48
49This corresponds to SRTP_AES128_CM_HMAC_SHA1_32 defined in RFC5764.
50
51=item SRTP_AEAD_AES_128_GCM
52
53This corresponds to the profile of the same name defined in RFC7714.
54
55=item SRTP_AEAD_AES_256_GCM
56
57This corresponds to the profile of the same name defined in RFC7714.
58
59=item SRTP_DOUBLE_AEAD_AES_128_GCM_AEAD_AES_128_GCM
60
61This corresponds to the profile of the same name defined in RFC8723.
62
63=item SRTP_DOUBLE_AEAD_AES_256_GCM_AEAD_AES_256_GCM
64
65This corresponds to the profile of the same name defined in RFC8723.
66
67=item SRTP_ARIA_128_CTR_HMAC_SHA1_80
68
69This corresponds to the profile of the same name defined in RFC8269.
70
71=item SRTP_ARIA_128_CTR_HMAC_SHA1_32
72
73This corresponds to the profile of the same name defined in RFC8269.
74
75=item SRTP_ARIA_256_CTR_HMAC_SHA1_80
76
77This corresponds to the profile of the same name defined in RFC8269.
78
79=item SRTP_ARIA_256_CTR_HMAC_SHA1_32
80
81This corresponds to the profile of the same name defined in RFC8269.
82
83=item SRTP_AEAD_ARIA_128_GCM
84
85This corresponds to the profile of the same name defined in RFC8269.
86
87=item SRTP_AEAD_ARIA_256_GCM
88
89This corresponds to the profile of the same name defined in RFC8269.
90
91=back
92
93Supplying an unrecognised protection profile name will result in an error.
94
95An OpenSSL server wishing to support the "use_srtp" extension should also call
96SSL_CTX_set_tlsext_use_srtp() or SSL_set_tlsext_use_srtp() to indicate the
97protection profiles that it is willing to negotiate.
98
99The currently configured list of protection profiles for either a client or a
100server can be obtained by calling SSL_get_srtp_profiles(). This returns a stack
101of SRTP_PROTECTION_PROFILE objects. The memory pointed to in the return value of
102this function should not be freed by the caller.
103
104After a handshake has been completed the negotiated SRTP protection profile (if
105any) can be obtained (on the client or the server) by calling
106SSL_get_selected_srtp_profile(). This function will return NULL if no SRTP
107protection profile was negotiated. The memory returned from this function should
108not be freed by the caller.
109
110If an SRTP protection profile has been successfully negotiated then the SRTP
111keying material (on both the client and server) should be obtained via a call to
112L<SSL_export_keying_material(3)>. This call should provide a label value of
113"EXTRACTOR-dtls_srtp" and a NULL context value (use_context is 0). The total
114length of keying material obtained should be equal to two times the sum of the
115master key length and the salt length as defined for the protection profile in
116use. This provides the client write master key, the server write master key, the
117client write master salt and the server write master salt in that order.
118
119These functions cannot be used with QUIC SSL objects.
120SSL_CTX_set_tlsext_use_srtp() fails if called on a QUIC SSL context.
121SSL_set_tlsext_use_srtp() fails if called on a QUIC SSL object.
122
123=head1 RETURN VALUES
124
125SSL_CTX_set_tlsext_use_srtp() and SSL_set_tlsext_use_srtp() return 0 on success
126or 1 on error.
127
128SSL_get_srtp_profiles() returns a stack of SRTP_PROTECTION_PROFILE objects on
129success or NULL on error or if no protection profiles have been configured.
130
131SSL_get_selected_srtp_profile() returns a pointer to an SRTP_PROTECTION_PROFILE
132object if one has been negotiated or NULL otherwise.
133
134=head1 SEE ALSO
135
136L<ssl(7)>,
137L<SSL_export_keying_material(3)>
138
139=head1 COPYRIGHT
140
141Copyright 2017-2023 The OpenSSL Project Authors. All Rights Reserved.
142
143Licensed under the Apache License 2.0 (the "License").  You may not use
144this file except in compliance with the License.  You can obtain a copy
145in the file LICENSE in the source distribution or at
146L<https://www.openssl.org/source/license.html>.
147
148=cut
149