.\" $OpenBSD: SSL_CTX_new.3,v 1.17 2022/07/13 22:05:53 schwarze Exp $ .\" full merge up to: OpenSSL 21cd6e00 Oct 21 14:40:15 2015 +0100 .\" selective merge up to: OpenSSL 8f75443f May 24 14:04:26 2019 +0200 .\" .\" This file was written by Lutz Jaenicke . .\" Copyright (c) 2000, 2005, 2012, 2013, 2015, 2016 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: July 13 2022 $ .Dt SSL_CTX_NEW 3 .Os .Sh NAME .Nm SSL_CTX_new , .Nm SSL_CTX_up_ref , .Nm TLS_method , .Nm TLS_server_method , .Nm TLS_client_method , .Nm SSLv23_method , .Nm SSLv23_server_method , .Nm SSLv23_client_method , .Nm TLSv1_method , .Nm TLSv1_server_method , .Nm TLSv1_client_method , .Nm TLSv1_1_method , .Nm TLSv1_1_server_method , .Nm TLSv1_1_client_method , .Nm TLSv1_2_method , .Nm TLSv1_2_server_method , .Nm TLSv1_2_client_method , .Nm DTLS_method , .Nm DTLS_server_method , .Nm DTLS_client_method , .Nm DTLSv1_method , .Nm DTLSv1_server_method , .Nm DTLSv1_client_method , .Nm DTLSv1_2_method , .Nm DTLSv1_2_server_method , .Nm DTLSv1_2_client_method .Nd create a new SSL_CTX object as a framework for TLS enabled functions .Sh SYNOPSIS .In openssl/ssl.h .Ft SSL_CTX * .Fn SSL_CTX_new "const SSL_METHOD *method" .Ft int .Fn SSL_CTX_up_ref "SSL_CTX *ctx" .Ft const SSL_METHOD * .Fn TLS_method void .Ft const SSL_METHOD * .Fn TLS_server_method void .Ft const SSL_METHOD * .Fn TLS_client_method void .Ft const SSL_METHOD * .Fn SSLv23_method void .Ft const SSL_METHOD * .Fn SSLv23_server_method void .Ft const SSL_METHOD * .Fn SSLv23_client_method void .Ft const SSL_METHOD * .Fn TLSv1_method void .Ft const SSL_METHOD * .Fn TLSv1_server_method void .Ft const SSL_METHOD * .Fn TLSv1_client_method void .Ft const SSL_METHOD * .Fn TLSv1_1_method void .Ft const SSL_METHOD * .Fn TLSv1_1_server_method void .Ft const SSL_METHOD * .Fn TLSv1_1_client_method void .Ft const SSL_METHOD * .Fn TLSv1_2_method void .Ft const SSL_METHOD * .Fn TLSv1_2_server_method void .Ft const SSL_METHOD * .Fn TLSv1_2_client_method void .Ft const SSL_METHOD * .Fn DTLS_method void .Ft const SSL_METHOD * .Fn DTLS_server_method void .Ft const SSL_METHOD * .Fn DTLS_client_method void .Ft const SSL_METHOD * .Fn DTLSv1_method void .Ft const SSL_METHOD * .Fn DTLSv1_server_method void .Ft const SSL_METHOD * .Fn DTLSv1_client_method void .Ft const SSL_METHOD * .Fn DTLSv1_2_method void .Ft const SSL_METHOD * .Fn DTLSv1_2_server_method void .Ft const SSL_METHOD * .Fn DTLSv1_2_client_method void .Sh DESCRIPTION .Fn SSL_CTX_new creates a new .Vt SSL_CTX object as a framework to establish TLS or DTLS enabled connections. It initializes the list of ciphers, the session cache setting, the callbacks, the keys and certificates, the options, and the security level to its default values. .Pp An .Vt SSL_CTX object is reference counted. Creating a new .Vt SSL_CTX object sets its reference count to 1. Calling .Fn SSL_CTX_up_ref on it increments the reference count by 1. Calling .Xr SSL_CTX_free 3 on it decrements the reference count by 1. When the reference count drops to zero, any memory or resources allocated to the .Vt SSL_CTX object are freed. .Pp The .Vt SSL_CTX object uses .Fa method as its connection method, which can be: .Bl -tag -width Ds .It Fn TLS_method The general-purpose version-flexible TLS method. The protocol version used will be negotiated to the highest version mutually supported by the client and the server. The supported protocols are TLSv1, TLSv1.1, TLSv1.2, and TLSv1.3. .It Fn DTLS_method The version-flexible DTLS method. The currently supported protocols are DTLSv1 and DTLSv1.2. .El .Pp The following .Fa method arguments are deprecated: .Bl -tag -width Ds .It Xo .Fn TLS_server_method , .Fn TLS_client_method , .Fn SSLv23_method , .Fn SSLv23_server_method , .Fn SSLv23_client_method .Xc Deprecated aliases for .Fn TLS_method . .It Xo .Fn DTLS_server_method , .Fn DTLS_client_method .Xc Deprecated aliases for .Fn DTLS_method . .It Xo .Fn TLSv1_method , .Fn TLSv1_server_method , .Fn TLSv1_client_method .Xc A connection established with these methods will only understand the TLSv1 protocol. .It Xo .Fn TLSv1_1_method , .Fn TLSv1_1_server_method , .Fn TLSv1_1_client_method .Xc A connection established with these methods will only understand the TLSv1.1 protocol. .It Xo .Fn TLSv1_2_method , .Fn TLSv1_2_server_method , .Fn TLSv1_2_client_method .Xc A connection established with these methods will only understand the TLSv1.2 protocol. .It Xo .Fn DTLSv1_method , .Fn DTLSv1_server_method , .Fn DTLSv1_client_method .Xc These are the version-specific methods for DTLSv1. .It Xo .Fn DTLSv1_2_method , .Fn DTLSv1_2_server_method , .Fn DTLSv1_2_client_method These are the version-specific methods for DTLSv1.2. .Xc .El .Pp In LibreSSL, the methods containing the substrings .Dq _server or .Dq _client in their names return the same objects as the methods without these substrings. .Pp The list of protocols available can also be limited using the .Dv SSL_OP_NO_TLSv1 , .Dv SSL_OP_NO_TLSv1_1 , and .Dv SSL_OP_NO_TLSv1_2 options of the .Xr SSL_CTX_set_options 3 or .Xr SSL_set_options 3 functions, but this approach is not recommended. Clients should avoid creating "holes" in the set of protocols they support. When disabling a protocol, make sure that you also disable either all previous or all subsequent protocol versions. In clients, when a protocol version is disabled without disabling all previous protocol versions, the effect is to also disable all subsequent protocol versions. .Pp DTLSv1 and DTLSv1.2 can be disabled with .Xr SSL_CTX_set_options 3 or .Xr SSL_set_options 3 using the .Dv SSL_OP_NO_DTLSv1 and .Dv SSL_OP_NO_DTLSv1_2 options, respectively. .Sh RETURN VALUES .Fn SSL_CTX_new returns a pointer to the newly allocated object or .Dv NULL on failure. Check the error stack to find out the reason for failure. .Pp .Fn SSL_CTX_up_ref returns 1 for success or 0 for failure. .Pp .Fn TLS_method and the other .Fn *_method functions return pointers to constant static objects. .Sh SEE ALSO .Xr ssl 3 , .Xr SSL_accept 3 , .Xr SSL_CTX_free 3 , .Xr SSL_CTX_set_min_proto_version 3 , .Xr SSL_CTX_set_options 3 , .Xr SSL_CTX_set_security_level 3 , .Xr SSL_set_connect_state 3 .Sh HISTORY .Fn SSL_CTX_new first appeared in SSLeay 0.5.1. .Fn SSLv23_method , .Fn SSLv23_server_method , and .Fn SSLv23_client_method first appeared in SSLeay 0.8.0. .Fn TLSv1_method , .Fn TLSv1_server_method , and .Fn TLSv1_client_method first appeared in SSLeay 0.9.0. All these functions have been available since .Ox 2.4 . .Pp .Fn DTLSv1_method , .Fn DTLSv1_server_method , and .Fn DTLSv1_client_method first appeared in OpenSSL 0.9.8 and have been available since .Ox 4.5 . .Pp .Fn TLSv1_1_method , .Fn TLSv1_1_server_method , .Fn TLSv1_1_client_method , .Fn TLSv1_2_method , .Fn TLSv1_2_server_method , and .Fn TLSv1_2_client_method first appeared in OpenSSL 1.0.1 and have been available since .Ox 5.3 . .Pp .Fn DTLS_method , .Fn DTLS_server_method , and .Fn DTLS_client_method first appeared in OpenSSL 1.0.2 and have been available since .Ox 6.5 . .Pp .Fn TLS_method , .Fn TLS_server_method , and .Fn TLS_client_method first appeared in OpenSSL 1.1.0 and have been available since .Ox 5.8 . .Pp .Fn SSL_CTX_up_ref first appeared in OpenSSL 1.1.0 and has been available since .Ox 6.3 . .Pp .Fn DTLSv1_2_method , .Fn DTLSv1_2_server_method , and .Fn DTLSv1_2_client_method first appeared in OpenSSL 1.1.0 and have been available since .Ox 6.9 .