1.\" $OpenBSD: SSL_CTX_set_cipher_list.3,v 1.4 2017/08/19 23:47:33 schwarze Exp $ 2.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100 3.\" 4.\" This file was written by Lutz Jaenicke <jaenicke@openssl.org>. 5.\" Copyright (c) 2000, 2001, 2013 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. All advertising materials mentioning features or use of this 20.\" software must display the following acknowledgment: 21.\" "This product includes software developed by the OpenSSL Project 22.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 23.\" 24.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 25.\" endorse or promote products derived from this software without 26.\" prior written permission. For written permission, please contact 27.\" openssl-core@openssl.org. 28.\" 29.\" 5. Products derived from this software may not be called "OpenSSL" 30.\" nor may "OpenSSL" appear in their names without prior written 31.\" permission of the OpenSSL Project. 32.\" 33.\" 6. Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: August 19 2017 $ 52.Dt SSL_CTX_SET_CIPHER_LIST 3 53.Os 54.Sh NAME 55.Nm SSL_CTX_set_cipher_list , 56.Nm SSL_set_cipher_list 57.Nd choose list of available SSL_CIPHERs 58.Sh SYNOPSIS 59.In openssl/ssl.h 60.Ft int 61.Fn SSL_CTX_set_cipher_list "SSL_CTX *ctx" "const char *str" 62.Ft int 63.Fn SSL_set_cipher_list "SSL *ssl" "const char *str" 64.Sh DESCRIPTION 65.Fn SSL_CTX_set_cipher_list 66sets the list of available ciphers for 67.Fa ctx 68using the control string 69.Fa str . 70The format of the string is described 71in 72.Xr openssl 1 . 73The list of ciphers is inherited by all 74.Fa ssl 75objects created from 76.Fa ctx . 77.Pp 78.Fn SSL_set_cipher_list 79sets the list of ciphers only for 80.Fa ssl . 81.Pp 82The control string 83.Fa str 84should be universally usable and not depend on details of the library 85configuration (ciphers compiled in). 86Thus no syntax checking takes place. 87Items that are not recognized, because the corresponding ciphers are not 88compiled in or because they are mistyped, are simply ignored. 89Failure is only flagged if no ciphers could be collected at all. 90.Pp 91It should be noted that inclusion of a cipher to be used into the list is a 92necessary condition. 93On the client side, the inclusion into the list is also sufficient. 94On the server side, additional restrictions apply. 95All ciphers have additional requirements. 96ADH ciphers don't need a certificate, but DH-parameters must have been set. 97All other ciphers need a corresponding certificate and key. 98.Pp 99A RSA cipher can only be chosen when a RSA certificate is available. 100RSA ciphers using DHE need a certificate and key and additional DH-parameters 101(see 102.Xr SSL_CTX_set_tmp_dh_callback 3 ) . 103.Pp 104A DSA cipher can only be chosen when a DSA certificate is available. 105DSA ciphers always use DH key exchange and therefore need DH-parameters (see 106.Xr SSL_CTX_set_tmp_dh_callback 3 ) . 107.Pp 108When these conditions are not met for any cipher in the list (for example, a 109client only supports export RSA ciphers with an asymmetric key length of 512 110bits and the server is not configured to use temporary RSA keys), the 111.Dq no shared cipher 112.Pq Dv SSL_R_NO_SHARED_CIPHER 113error is generated and the handshake will fail. 114.Sh RETURN VALUES 115.Fn SSL_CTX_set_cipher_list 116and 117.Fn SSL_set_cipher_list 118return 1 if any cipher could be selected and 0 on complete failure. 119.Sh SEE ALSO 120.Xr ssl 3 , 121.Xr SSL_CTX_set1_groups 3 , 122.Xr SSL_CTX_set_tmp_dh_callback 3 , 123.Xr SSL_CTX_use_certificate 3 , 124.Xr SSL_get_ciphers 3 125