SSL_CTX_set_cipher_list 3 2002-06-09 0.9.9-dev OpenSSL

NAME

SSL_CTX_set_cipher_list, SSL_set_cipher_list - choose list of available SSL_CIPHERs

LIBRARY

libcrypto, -lcrypto

SYNOPSIS


 #include 


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

DESCRIPTION

_S_S_L___C_T_X___s_e_t___c_i_p_h_e_r___l_i_s_t_(_) sets the list of available ciphers for ccttxx using the control string ssttrr. The format of the string is described in _o_p_e_n_s_s_l___c_i_p_h_e_r_s(1). The list of ciphers is inherited by all ssssll objects created from ccttxx.

_S_S_L___s_e_t___c_i_p_h_e_r___l_i_s_t_(_) sets the list of ciphers only for ssssll.

NOTES

The control string ssttrr 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 _S_S_L___C_T_X___s_e_t___t_m_p___r_s_a___c_a_l_l_b_a_c_k(3)). RSA ciphers using EDH need a certificate and key and additional DH-parameters (see _S_S_L___C_T_X___s_e_t___t_m_p___d_h___c_a_l_l_b_a_c_k(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 _S_S_L___C_T_X___s_e_t___t_m_p___d_h___c_a_l_l_b_a_c_k(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

_S_S_L___C_T_X___s_e_t___c_i_p_h_e_r___l_i_s_t_(_) and _S_S_L___s_e_t___c_i_p_h_e_r___l_i_s_t_(_) return 1 if any cipher could be selected and 0 on complete failure.

SEE ALSO

_s_s_l(3), _S_S_L___g_e_t___c_i_p_h_e_r_s(3), _S_S_L___C_T_X___u_s_e___c_e_r_t_i_f_i_c_a_t_e(3), _S_S_L___C_T_X___s_e_t___t_m_p___r_s_a___c_a_l_l_b_a_c_k(3), _S_S_L___C_T_X___s_e_t___t_m_p___d_h___c_a_l_l_b_a_c_k(3), _o_p_e_n_s_s_l___c_i_p_h_e_r_s(1)