doc/man3/SSL_CTX_set_cipher_list.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 SSL_CTX_set_cipher_list,
   6 SSL_set_cipher_list,
   7 SSL_CTX_set_ciphersuites,
   8 SSL_set_ciphersuites,
   9 OSSL_default_cipher_list,
  10 OSSL_default_ciphersuites
  11 - choose list of available SSL_CIPHERs
  12
  13 =head1 SYNOPSIS
  14
  15  #include <openssl/ssl.h>
  16
  17  int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
  18  int SSL_set_cipher_list(SSL *ssl, const char *str);
  19
  20  int SSL_CTX_set_ciphersuites(SSL_CTX *ctx, const char *str);
  21  int SSL_set_ciphersuites(SSL *s, const char *str);
  22
  23  const char *OSSL_default_cipher_list(void);
  24  const char *OSSL_default_ciphersuites(void);
  25
  26 =head1 DESCRIPTION
  27
  28 SSL_CTX_set_cipher_list() sets the list of available ciphers (TLSv1.2 and below)
  29 for B<ctx> using the control string B<str>. The format of the string is described
  30 in L<openssl-ciphers(1)>. The list of ciphers is inherited by all
  31 B<ssl> objects created from B<ctx>. This function does not impact TLSv1.3
  32 ciphersuites. Use SSL_CTX_set_ciphersuites() to configure those.
  33
  34 SSL_set_cipher_list() sets the list of ciphers (TLSv1.2 and below) only for
  35 B<ssl>.
  36
  37 SSL_CTX_set_ciphersuites() is used to configure the available TLSv1.3
  38 ciphersuites for B<ctx>. This is a simple colon (":") separated list of TLSv1.3
  39 ciphersuite names in order of preference. Valid TLSv1.3 ciphersuite names are:
  40
  41 =over 4
  42
  43 =item TLS_AES_128_GCM_SHA256
  44
  45 =item TLS_AES_256_GCM_SHA384
  46
  47 =item TLS_CHACHA20_POLY1305_SHA256
  48
  49 =item TLS_AES_128_CCM_SHA256
  50
  51 =item TLS_AES_128_CCM_8_SHA256
  52
  53 =item TLS_SHA384_SHA384 - integrity-only
  54
  55 =item TLS_SHA256_SHA256 - integrity-only
  56
  57 =back
  58
  59 An empty list is permissible. The default value for the this setting is:
  60
  61 "TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256"
  62
  63 SSL_set_ciphersuites() is the same as SSL_CTX_set_ciphersuites() except it
  64 configures the ciphersuites for B<ssl>.
  65
  66 OSSL_default_cipher_list() returns the default cipher string for TLSv1.2
  67 (and earlier) ciphers. OSSL_default_ciphersuites() returns the default
  68 cipher string for TLSv1.3 ciphersuites.
  69
  70 =head1 NOTES
  71
  72 The control string B<str> for SSL_CTX_set_cipher_list(), SSL_set_cipher_list(),
  73 SSL_CTX_set_ciphersuites() and SSL_set_ciphersuites() should be universally
  74 usable and not depend on details of the library configuration (ciphers compiled
  75 in). Thus no syntax checking takes place. Items that are not recognized, because
  76 the corresponding ciphers are not compiled in or because they are mistyped,
  77 are simply ignored. Failure is only flagged if no ciphers could be collected
  78 at all.
  79
  80 It should be noted, that inclusion of a cipher to be used into the list is
  81 a necessary condition. On the client side, the inclusion into the list is
  82 also sufficient unless the security level excludes it. On the server side,
  83 additional restrictions apply. All ciphers have additional requirements.
  84 ADH ciphers don't need a certificate, but DH-parameters must have been set.
  85 All other ciphers need a corresponding certificate and key.
  86
  87 An RSA cipher can only be chosen, when an RSA certificate is available.
  88 RSA ciphers using DHE need a certificate and key and additional DH-parameters
  89 (see L<SSL_CTX_set_tmp_dh_callback(3)>).
  90
  91 A DSA cipher can only be chosen, when a DSA certificate is available.
  92 DSA ciphers always use DH key exchange and therefore need DH-parameters
  93 (see L<SSL_CTX_set_tmp_dh_callback(3)>).
  94
  95 When these conditions are not met for any cipher in the list (e.g. a
  96 client only supports export RSA ciphers with an asymmetric key length
  97 of 512 bits and the server is not configured to use temporary RSA
  98 keys), the "no shared cipher" (SSL_R_NO_SHARED_CIPHER) error is generated
  99 and the handshake will fail.
 100
 101 OSSL_default_cipher_list() and OSSL_default_ciphersuites() replace
 102 SSL_DEFAULT_CIPHER_LIST and TLS_DEFAULT_CIPHERSUITES, respectively. The
 103 cipher list defines are deprecated as of 3.0.
 104
 105 =head1 RETURN VALUES
 106
 107 SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher
 108 could be selected and 0 on complete failure.
 109
 110 SSL_CTX_set_ciphersuites() and SSL_set_ciphersuites() return 1 if the requested
 111 ciphersuite list was configured, and 0 otherwise.
 112
 113 =head1 SEE ALSO
 114
 115 L<ssl(7)>, L<SSL_get_ciphers(3)>,
 116 L<SSL_CTX_use_certificate(3)>,
 117 L<SSL_CTX_set_tmp_dh_callback(3)>,
 118 L<openssl-ciphers(1)>
 119
 120 =head1 HISTORY
 121
 122 OSSL_default_cipher_list() and OSSL_default_ciphersites() are new in 3.0.
 123
 124 =head1 COPYRIGHT
 125
 126 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
 127
 128 Licensed under the Apache License 2.0 (the "License").  You may not use
 129 this file except in compliance with the License.  You can obtain a copy
 130 in the file LICENSE in the source distribution or at
 131 L<https://www.openssl.org/source/license.html>.
 132
 133 =cut