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

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>.

3.0.13                                             2025-02-05                      SSL_CTX_SET_CIPHER_LIST(3SSL)