SSL_CTX_set_cipher_list(3) OpenSSL SSL_CTX_set_cipher_list(3)
SSL_CTX_set_cipher_list, SSL_set_cipher_list - choose list of available SSL_CIPHERs
int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
int SSL_set_cipher_list(SSL *ssl, const char *str);
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.
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 col-
lected 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 typi-
cally 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
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 config-
ured to use temporary RSA keys), the "no shared cipher" (SSL_R_NO_SHARED_CIPHER) error is
generated and the handshake will fail.
SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher could be
selected and 0 on complete failure.
ssl(3), SSL_get_ciphers(3), SSL_CTX_use_certificate(3), SSL_CTX_set_tmp_rsa_callback(3),
0.9.7a 2001-07-23 SSL_CTX_set_cipher_list(3)