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1=pod
2
3=head1 NAME
4
5SSL_CTX_set_cipher_list,
6SSL_set_cipher_list,
7SSL_CTX_set_ciphersuites,
8SSL_set_ciphersuites,
9OSSL_default_cipher_list,
10OSSL_default_ciphersuites
11- choose list of available SSL_CIPHERs
12
13=head1 SYNOPSIS
14
15 #include <openssl/ssl.h>
16
17 int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
18 int SSL_set_cipher_list(SSL *ssl, const char *str);
19
20 int SSL_CTX_set_ciphersuites(SSL_CTX *ctx, const char *str);
21 int SSL_set_ciphersuites(SSL *s, const char *str);
22
23 const char *OSSL_default_cipher_list(void);
24 const char *OSSL_default_ciphersuites(void);
25
26=head1 DESCRIPTION
27
28SSL_CTX_set_cipher_list() sets the list of available ciphers (TLSv1.2 and below)
29for B<ctx> using the control string B<str>. The format of the string is described
30in L<openssl-ciphers(1)>. The list of ciphers is inherited by all
31B<ssl> objects created from B<ctx>. This function does not impact TLSv1.3
32ciphersuites. Use SSL_CTX_set_ciphersuites() to configure those.
33
34SSL_set_cipher_list() sets the list of ciphers (TLSv1.2 and below) only for
35B<ssl>.
36
37SSL_CTX_set_ciphersuites() is used to configure the available TLSv1.3
38ciphersuites for B<ctx>. This is a simple colon (":") separated list of TLSv1.3
39ciphersuite names in order of preference. Valid TLSv1.3 ciphersuite names are:
40
41=over 4
42
43=item TLS_AES_128_GCM_SHA256
44
45=item TLS_AES_256_GCM_SHA384
46
47=item TLS_CHACHA20_POLY1305_SHA256
48
49=item TLS_AES_128_CCM_SHA256
50
51=item TLS_AES_128_CCM_8_SHA256
52
53=back
54
55An empty list is permissible. The default value for the this setting is:
56
57"TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256"
58
59SSL_set_ciphersuites() is the same as SSL_CTX_set_ciphersuites() except it
60configures the ciphersuites for B<ssl>.
61
62OSSL_default_cipher_list() returns the default cipher string for TLSv1.2
63(and earlier) ciphers. OSSL_default_ciphersuites() returns the default
64cipher string for TLSv1.3 ciphersuites.
65
66=head1 NOTES
67
68The control string B<str> for SSL_CTX_set_cipher_list(), SSL_set_cipher_list(),
69SSL_CTX_set_ciphersuites() and SSL_set_ciphersuites() should be universally
70usable and not depend on details of the library configuration (ciphers compiled
71in). Thus no syntax checking takes place. Items that are not recognized, because
72the corresponding ciphers are not compiled in or because they are mistyped,
73are simply ignored. Failure is only flagged if no ciphers could be collected
74at all.
75
76It should be noted, that inclusion of a cipher to be used into the list is
77a necessary condition. On the client side, the inclusion into the list is
78also sufficient unless the security level excludes it. On the server side,
79additional restrictions apply. All ciphers have additional requirements.
80ADH ciphers don't need a certificate, but DH-parameters must have been set.
81All other ciphers need a corresponding certificate and key.
82
83An RSA cipher can only be chosen, when an RSA certificate is available.
84RSA ciphers using DHE need a certificate and key and additional DH-parameters
85(see L<SSL_CTX_set_tmp_dh_callback(3)>).
86
87A DSA cipher can only be chosen, when a DSA certificate is available.
88DSA ciphers always use DH key exchange and therefore need DH-parameters
89(see L<SSL_CTX_set_tmp_dh_callback(3)>).
90
91When these conditions are not met for any cipher in the list (e.g. a
92client only supports export RSA ciphers with an asymmetric key length
93of 512 bits and the server is not configured to use temporary RSA
94keys), the "no shared cipher" (SSL_R_NO_SHARED_CIPHER) error is generated
95and the handshake will fail.
96
97OSSL_default_cipher_list() and OSSL_default_ciphersuites() replace
98SSL_DEFAULT_CIPHER_LIST and TLS_DEFAULT_CIPHERSUITES, respectively. The
99cipher list defines are deprecated as of 3.0.
100
101=head1 RETURN VALUES
102
103SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher
104could be selected and 0 on complete failure.
105
106SSL_CTX_set_ciphersuites() and SSL_set_ciphersuites() return 1 if the requested
107ciphersuite list was configured, and 0 otherwise.
108
109=head1 SEE ALSO
110
111L<ssl(7)>, L<SSL_get_ciphers(3)>,
112L<SSL_CTX_use_certificate(3)>,
113L<SSL_CTX_set_tmp_dh_callback(3)>,
114L<openssl-ciphers(1)>
115
116=head1 HISTORY
117
118OSSL_default_cipher_list() and OSSL_default_ciphersites() are new in 3.0.
119
120=head1 COPYRIGHT
121
122Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
123
124Licensed under the Apache License 2.0 (the "License").  You may not use
125this file except in compliance with the License.  You can obtain a copy
126in the file LICENSE in the source distribution or at
127L<https://www.openssl.org/source/license.html>.
128
129=cut
130