NAME

       SSL_CTX_set_cipher_list, SSL_set_cipher_list - choose list of available SSL_CIPHERs

SYNOPSIS

        #include <openssl/ssl.h>

        int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
        int SSL_set_cipher_list(SSL *ssl, const char *str);

DESCRIPTION

       SSL_CTX_set_cipher_list() sets the list of available ciphers for ctx using the control string str. The
       format of the string is described in ciphers(1). The list of ciphers is inherited by all ssl objects
       created from ctx.

       SSL_set_cipher_list() sets the list of ciphers only for ssl.

NOTES

       The control string str should be universally usable and not depend on details of the library
       configuration (ciphers compiled in). Thus no syntax checking takes place. Items that are not recognized,
       because the corresponding ciphers are not compiled in or because they are mistyped, are simply ignored.
       Failure is only flagged if no ciphers could be collected at all.

       It should be noted, that inclusion of a cipher to be used into the list is a necessary condition. On the
       client side, the inclusion into the list is also sufficient. On the server side, additional restrictions
       apply. All ciphers have additional requirements. ADH ciphers don't need a certificate, but DH-parameters
       must have been set. All other ciphers need a corresponding certificate and key.

       A RSA cipher can only be chosen, when a RSA certificate is available.  RSA export ciphers with a
       keylength of 512 bits for the RSA key require a temporary 512 bit RSA key, as typically the supplied key
       has a length of 1024 bit (see SSL_CTX_set_tmp_rsa_callback(3)).  RSA ciphers using EDH need a certificate
       and key and additional DH-parameters (see SSL_CTX_set_tmp_dh_callback(3)).

       A DSA cipher can only be chosen, when a DSA certificate is available.  DSA ciphers always use DH key
       exchange and therefore need DH-parameters (see SSL_CTX_set_tmp_dh_callback(3)).

       When these conditions are not met for any cipher in the list (e.g. a client only supports export RSA
       ciphers with a asymmetric key length of 512 bits and the server is not configured to use temporary RSA
       keys), the "no shared cipher" (SSL_R_NO_SHARED_CIPHER) error is generated and the handshake will fail.

RETURN VALUES

       SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher could be selected and 0 on
       complete failure.

SEE ALSO

       ssl(3), SSL_get_ciphers(3), SSL_CTX_use_certificate(3), SSL_CTX_set_tmp_rsa_callback(3),
       SSL_CTX_set_tmp_dh_callback(3), ciphers(1)