SSL_CTX_set_cipher_list, SSL_set_cipher_list, SSL_CTX_set_ciphersuites,
SSL_set_ciphersuites, OSSL_default_cipher_list, OSSL_default_ciphersuites -
choose list of available SSL_CIPHERs
#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);
int SSL_CTX_set_ciphersuites(SSL_CTX *ctx, const char *str);
int SSL_set_ciphersuites(SSL *s, const char *str);
const char *OSSL_default_cipher_list(void);
const char *OSSL_default_ciphersuites(void);
SSL_CTX_set_cipher_list() sets the list of available ciphers (TLSv1.2 and
below) for
ctx using the control string
str. The format of the
string is described in
openssl-ciphers(1). The list of ciphers is
inherited by all
ssl objects created from
ctx. This function
does not impact TLSv1.3 ciphersuites. Use
SSL_CTX_set_ciphersuites() to
configure those.
SSL_set_cipher_list() sets the list of ciphers (TLSv1.2 and below) only
for
ssl.
SSL_CTX_set_ciphersuites() is used to configure the available TLSv1.3
ciphersuites for
ctx. This is a simple colon (":") separated
list of TLSv1.3 ciphersuite names in order of preference. Valid TLSv1.3
ciphersuite names are:
- TLS_AES_128_GCM_SHA256
- TLS_AES_256_GCM_SHA384
- TLS_CHACHA20_POLY1305_SHA256
- TLS_AES_128_CCM_SHA256
- TLS_AES_128_CCM_8_SHA256
An empty list is permissible. The default value for the this setting is:
"TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256"
SSL_set_ciphersuites() is the same as
SSL_CTX_set_ciphersuites()
except it configures the ciphersuites for
ssl.
OSSL_default_cipher_list() returns the default cipher string for TLSv1.2
(and earlier) ciphers.
OSSL_default_ciphersuites() returns the default
cipher string for TLSv1.3 ciphersuites.
The control string
str for
SSL_CTX_set_cipher_list(),
SSL_set_cipher_list(),
SSL_CTX_set_ciphersuites() and
SSL_set_ciphersuites() 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 unless the security level excludes it. 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.
An RSA cipher can only be chosen, when an RSA certificate is available. 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 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.
OSSL_default_cipher_list() and
OSSL_default_ciphersuites() replace
SSL_DEFAULT_CIPHER_LIST and TLS_DEFAULT_CIPHERSUITES, respectively. The cipher
list defines are deprecated as of 3.0.
SSL_CTX_set_cipher_list() and
SSL_set_cipher_list() return 1 if
any cipher could be selected and 0 on complete failure.
SSL_CTX_set_ciphersuites() and
SSL_set_ciphersuites() return 1 if
the requested ciphersuite list was configured, and 0 otherwise.
ssl(7),
SSL_get_ciphers(3),
SSL_CTX_use_certificate(3),
SSL_CTX_set_tmp_dh_callback(3),
openssl-ciphers(1)
OSSL_default_cipher_list() and
OSSL_default_ciphersites() are new
in 3.0.
Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy in the
file LICENSE in the source distribution or at
<
https://www.openssl.org/source/license.html>.