SSL_CTX_SET_CIPHER_LI... BSD Library Functions Manual SSL_CTX_SET_CIPHER_LI...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);
DESCRIPTIONSSL_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
openssl(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 syn‐
tax 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 cer‐
tificate, 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 bits (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-parameters (see
SSL_CTX_set_tmp_dh_callback(3)).
When these conditions are not met for any cipher in the list (for exam‐
ple, 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 “no shared cipher” (SSL_R_NO_SHARED_CIPHER) error is generated
and the handshake will fail.
RETURN VALUESSSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any
cipher could be selected and 0 on complete failure.
SEE ALSOciphers(1), ssl(3), SSL_CTX_set_tmp_dh_callback(3),
SSL_CTX_set_tmp_rsa_callback(3), SSL_CTX_use_certificate(3),
SSL_get_ciphers(3)BSD June 1, 2024 BSD