Updated: 2022/Sep/29

Please read Privacy Policy. It's for your privacy.

SSL_CTX_set_cipher_list(3)          OpenSSL         SSL_CTX_set_cipher_list(3)



NAME
       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

LIBRARY
       libcrypto, -lcrypto

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);

        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);

DESCRIPTION
       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.

NOTES
       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.

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.

       SSL_CTX_set_ciphersuites() and SSL_set_ciphersuites() return 1 if the
       requested ciphersuite list was configured, and 0 otherwise.

SEE ALSO
       ssl(7), SSL_get_ciphers(3), SSL_CTX_use_certificate(3),
       SSL_CTX_set_tmp_dh_callback(3), openssl-ciphers(1)

HISTORY
       OSSL_default_cipher_list() and OSSL_default_ciphersites() are new in
       3.0.

COPYRIGHT
       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>.



3.0.12                            2023-05-07        SSL_CTX_set_cipher_list(3)