/usr/man/cat.3/SSL_set_cipher_list.3

SSL_CTX_set_cipher_list(3)   OpenSSL   SSL_CTX_set_cipher_list(3)

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 DHE
     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

1.0.2t               Last change: 2019-09-10                    1

SSL_CTX_set_cipher_list(3)   OpenSSL   SSL_CTX_set_cipher_list(3)

     cipher" (SSL_R_NO_SHARED_CIPHER) error is generated and the
     handshake will fail.

     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 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)

1.0.2t               Last change: 2019-09-10                    2

See also SSL_CTX_set_cipher_list(3)