SSL_CTX_set_cipher_list.pod revision 279264 
1=pod
2
3=head1 NAME
4
5SSL_CTX_set_cipher_list, SSL_set_cipher_list - choose list of available SSL_CIPHERs
6
7=head1 SYNOPSIS
8
9 #include <openssl/ssl.h>
10
11 int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
12 int SSL_set_cipher_list(SSL *ssl, const char *str);
13
14=head1 DESCRIPTION
15
16SSL_CTX_set_cipher_list() sets the list of available ciphers for B<ctx>
17using the control string B<str>. The format of the string is described
18in L<ciphers(1)|ciphers(1)>. The list of ciphers is inherited by all
19B<ssl> objects created from B<ctx>.
20
21SSL_set_cipher_list() sets the list of ciphers only for B<ssl>.
22
23=head1 NOTES
24
25The control string B<str> should be universally usable and not depend
26on details of the library configuration (ciphers compiled in). Thus no
27syntax checking takes place. Items that are not recognized, because the
28corresponding ciphers are not compiled in or because they are mistyped,
29are simply ignored. Failure is only flagged if no ciphers could be collected
30at all.
31
32It should be noted, that inclusion of a cipher to be used into the list is
33a necessary condition. On the client side, the inclusion into the list is
34also sufficient. On the server side, additional restrictions apply. All ciphers
35have additional requirements. ADH ciphers don't need a certificate, but
36DH-parameters must have been set. All other ciphers need a corresponding
37certificate and key.
38
39A RSA cipher can only be chosen, when a RSA certificate is available.
40RSA export ciphers with a keylength of 512 bits for the RSA key require
41a temporary 512 bit RSA key, as typically the supplied key has a length
42of 1024 bit (see
43L<SSL_CTX_set_tmp_rsa_callback(3)|SSL_CTX_set_tmp_rsa_callback(3)>).
44RSA ciphers using EDH need a certificate and key and additional DH-parameters
45(see L<SSL_CTX_set_tmp_dh_callback(3)|SSL_CTX_set_tmp_dh_callback(3)>).
46
47A DSA cipher can only be chosen, when a DSA certificate is available.
48DSA ciphers always use DH key exchange and therefore need DH-parameters
49(see L<SSL_CTX_set_tmp_dh_callback(3)|SSL_CTX_set_tmp_dh_callback(3)>).
50
51When these conditions are not met for any cipher in the list (e.g. a
52client only supports export RSA ciphers with a asymmetric key length
53of 512 bits and the server is not configured to use temporary RSA
54keys), the "no shared cipher" (SSL_R_NO_SHARED_CIPHER) error is generated
55and the handshake will fail.
56
57If the cipher list does not contain any SSLv2 cipher suites (this is the
58default) then SSLv2 is effectively disabled and neither clients nor servers
59will attempt to use SSLv2.
60
61=head1 RETURN VALUES
62
63SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher
64could be selected and 0 on complete failure.
65
66=head1 SEE ALSO
67
68L<ssl(3)|ssl(3)>, L<SSL_get_ciphers(3)|SSL_get_ciphers(3)>,
69L<SSL_CTX_use_certificate(3)|SSL_CTX_use_certificate(3)>,
70L<SSL_CTX_set_tmp_rsa_callback(3)|SSL_CTX_set_tmp_rsa_callback(3)>,
71L<SSL_CTX_set_tmp_dh_callback(3)|SSL_CTX_set_tmp_dh_callback(3)>,
72L<ciphers(1)|ciphers(1)>
73
74=cut
75