SSL_CTX_set_cipher_list, SSL_set_cipher_list - choose list of available
int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
int SSL_set_cipher_list(SSL *ssl, const char *str);
sets the list of available ciphers for
using the control string str
. The format of the string is
described in openssl_ciphers
(1). The list of ciphers is inherited by
objects created from ctx
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 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
(3)). RSA ciphers using DHE 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
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
If the cipher list does not contain any SSLv2 cipher suites (this is the
default) then SSLv2 is effectively disabled and neither clients nor servers
will attempt to use SSLv2.
return 1 if
any cipher could be selected and 0 on complete failure.