SSL_CTX_set_cipher_list
Section: OpenSSL (3)
Updated: 2017-05-25
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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 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)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- NOTES
-
- RETURN VALUES
-
- SEE ALSO
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