SSL_CTX_set_cipher_list(3)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
The SSL_CTX_set_cipher_list() function 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.
The SSL_set_cipher_list() function 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 ignored. Failure is only flagged if no ciphers could be collected.
Inclusion of a cipher to be used into the list is a necessary condi‐
tion. On the client side, the inclusion into the list is also suffi‐
cient. On the server side, additional restrictions apply. All ciphers
have additional requirements. ADH ciphers do not need a certificate,
but DH-parameters must have been set. All other ciphers need a corre‐
sponding certificate and key.
An RSA cipher can only be chosen when an RSA certificate is available.
RSA export ciphers with a keylength of 512 bits. The RSA key requires a
temporary 512-bit RSA key, and 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-parame‐
ters. (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 an asymmetric key length
of 512 bits and the server is not configured to use temporary RSA
keys), the SSL_R_NO_SHARED_CIPHER error is generated and the handshake
will fail.
RETURN VALUES
The SSL_CTX_set_cipher_list() and SSL_set_cipher_list() functions
return 1 if any cipher could be selected and 0 on complete failure.
SEE ALSO
Commands: ciphers(1)
Functions: 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)SSL_CTX_set_cipher_list(3)
