5 TLSv1_2_method, TLSv1_2_server_method, TLSv1_2_client_method,
6 SSL_CTX_new, SSL_CTX_new_ex, SSL_CTX_up_ref, SSLv3_method,
7 SSLv3_server_method, SSLv3_client_method, TLSv1_method, TLSv1_server_method,
8 TLSv1_client_method, TLSv1_1_method, TLSv1_1_server_method,
9 TLSv1_1_client_method, TLS_method, TLS_server_method, TLS_client_method,
10 SSLv23_method, SSLv23_server_method, SSLv23_client_method, DTLS_method,
11 DTLS_server_method, DTLS_client_method, DTLSv1_method, DTLSv1_server_method,
12 DTLSv1_client_method, DTLSv1_2_method, DTLSv1_2_server_method,
13 DTLSv1_2_client_method
14 - create a new SSL_CTX object as framework for TLS/SSL or DTLS enabled
19 #include <openssl/ssl.h>
21 SSL_CTX *SSL_CTX_new_ex(OSSL_LIB_CTX *libctx, const char *propq,
22 const SSL_METHOD *method);
23 SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);
24 int SSL_CTX_up_ref(SSL_CTX *ctx);
26 const SSL_METHOD *TLS_method(void);
27 const SSL_METHOD *TLS_server_method(void);
28 const SSL_METHOD *TLS_client_method(void);
30 const SSL_METHOD *SSLv23_method(void);
31 const SSL_METHOD *SSLv23_server_method(void);
32 const SSL_METHOD *SSLv23_client_method(void);
34 #ifndef OPENSSL_NO_SSL3_METHOD
35 const SSL_METHOD *SSLv3_method(void);
36 const SSL_METHOD *SSLv3_server_method(void);
37 const SSL_METHOD *SSLv3_client_method(void);
40 #ifndef OPENSSL_NO_TLS1_METHOD
41 const SSL_METHOD *TLSv1_method(void);
42 const SSL_METHOD *TLSv1_server_method(void);
43 const SSL_METHOD *TLSv1_client_method(void);
46 #ifndef OPENSSL_NO_TLS1_1_METHOD
47 const SSL_METHOD *TLSv1_1_method(void);
48 const SSL_METHOD *TLSv1_1_server_method(void);
49 const SSL_METHOD *TLSv1_1_client_method(void);
52 #ifndef OPENSSL_NO_TLS1_2_METHOD
53 const SSL_METHOD *TLSv1_2_method(void);
54 const SSL_METHOD *TLSv1_2_server_method(void);
55 const SSL_METHOD *TLSv1_2_client_method(void);
58 const SSL_METHOD *DTLS_method(void);
59 const SSL_METHOD *DTLS_server_method(void);
60 const SSL_METHOD *DTLS_client_method(void);
62 #ifndef OPENSSL_NO_DTLS1_METHOD
63 const SSL_METHOD *DTLSv1_method(void);
64 const SSL_METHOD *DTLSv1_server_method(void);
65 const SSL_METHOD *DTLSv1_client_method(void);
68 #ifndef OPENSSL_NO_DTLS1_2_METHOD
69 const SSL_METHOD *DTLSv1_2_method(void);
70 const SSL_METHOD *DTLSv1_2_server_method(void);
71 const SSL_METHOD *DTLSv1_2_client_method(void);
76 SSL_CTX_new_ex() creates a new B<SSL_CTX> object, which holds various
77 configuration and data relevant to TLS/SSL or DTLS session establishment. The
78 library context I<libctx> (see L<OSSL_LIB_CTX(3)>) is used to provide the
79 cryptographic algorithms needed for the session. Any cryptographic algorithms
80 that are used by any B<SSL> objects created from this B<SSL_CTX> will be fetched
81 from the I<libctx> using the property query string I<propq> (see
82 L<provider(7)/Fetching algorithms>. Either or both the I<libctx> or I<propq>
83 parameters may be NULL.
85 SSL_CTX_new() does the same as SSL_CTX_new_ex() except that the default
86 library context is used and no property query string is specified.
88 An B<SSL_CTX> object is reference counted. Creating an B<SSL_CTX> object for the
89 first time increments the reference count. Freeing the B<SSL_CTX> (using
90 SSL_CTX_free) decrements it. When the reference count drops to zero, any memory
91 or resources allocated to the B<SSL_CTX> object are freed. SSL_CTX_up_ref()
92 increments the reference count for an existing B<SSL_CTX> structure.
94 An B<SSL_CTX> object should not be changed after it is used to create any B<SSL>
95 objects or from multiple threads concurrently, since the implementation does not
96 provide serialization of access for these cases.
100 The SSL_CTX object uses I<method> as the connection method.
101 The methods exist in a generic type (for client and server use), a server only
102 type, and a client only type.
103 B<method> can be one of the following types:
107 =item TLS_method(), TLS_server_method(), TLS_client_method()
109 These are the general-purpose I<version-flexible> SSL/TLS methods.
110 The actual protocol version used will be negotiated to the highest version
111 mutually supported by the client and the server.
112 The supported protocols are SSLv3, TLSv1, TLSv1.1, TLSv1.2 and TLSv1.3.
113 Applications should use these methods, and avoid the version-specific
114 methods described below, which are deprecated.
116 =item SSLv23_method(), SSLv23_server_method(), SSLv23_client_method()
118 These functions do not exist anymore, they have been renamed to
119 TLS_method(), TLS_server_method() and TLS_client_method() respectively.
120 Currently, the old function calls are renamed to the corresponding new
121 ones by preprocessor macros, to ensure that existing code which uses the
122 old function names still compiles. However, using the old function names
123 is deprecated and new code should call the new functions instead.
125 =item TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method()
127 A TLS/SSL connection established with these methods will only understand the
128 TLSv1.2 protocol. These methods are deprecated.
130 =item TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method()
132 A TLS/SSL connection established with these methods will only understand the
133 TLSv1.1 protocol. These methods are deprecated.
135 =item TLSv1_method(), TLSv1_server_method(), TLSv1_client_method()
137 A TLS/SSL connection established with these methods will only understand the
138 TLSv1 protocol. These methods are deprecated.
140 =item SSLv3_method(), SSLv3_server_method(), SSLv3_client_method()
142 A TLS/SSL connection established with these methods will only understand the
144 The SSLv3 protocol is deprecated and should not be used.
146 =item DTLS_method(), DTLS_server_method(), DTLS_client_method()
148 These are the version-flexible DTLS methods.
149 Currently supported protocols are DTLS 1.0 and DTLS 1.2.
151 =item DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method()
153 These are the version-specific methods for DTLSv1.2.
154 These methods are deprecated.
156 =item DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method()
158 These are the version-specific methods for DTLSv1.
159 These methods are deprecated.
163 SSL_CTX_new() initializes the list of ciphers, the session cache setting, the
164 callbacks, the keys and certificates and the options to their default values.
166 TLS_method(), TLS_server_method(), TLS_client_method(), DTLS_method(),
167 DTLS_server_method() and DTLS_client_method() are the I<version-flexible>
169 All other methods only support one specific protocol version.
170 Use the I<version-flexible> methods instead of the version specific methods.
172 If you want to limit the supported protocols for the version flexible
173 methods you can use L<SSL_CTX_set_min_proto_version(3)>,
174 L<SSL_set_min_proto_version(3)>, L<SSL_CTX_set_max_proto_version(3)> and
175 L<SSL_set_max_proto_version(3)> functions.
176 Using these functions it is possible to choose e.g. TLS_server_method()
177 and be able to negotiate with all possible clients, but to only
178 allow newer protocols like TLS 1.0, TLS 1.1, TLS 1.2 or TLS 1.3.
180 The list of protocols available can also be limited using the
181 B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>, B<SSL_OP_NO_TLSv1_1>,
182 B<SSL_OP_NO_TLSv1_3>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
184 L<SSL_CTX_set_options(3)> or L<SSL_set_options(3)> functions, but this approach
185 is not recommended. Clients should avoid creating "holes" in the set of
186 protocols they support. When disabling a protocol, make sure that you also
187 disable either all previous or all subsequent protocol versions.
188 In clients, when a protocol version is disabled without disabling I<all>
189 previous protocol versions, the effect is to also disable all subsequent
192 The SSLv3 protocol is deprecated and should generally not be used.
193 Applications should typically use L<SSL_CTX_set_min_proto_version(3)> to set
194 the minimum protocol to at least B<TLS1_VERSION>.
198 The following return values can occur:
204 The creation of a new SSL_CTX object failed. Check the error stack to find out
207 =item Pointer to an SSL_CTX object
209 The return value points to an allocated SSL_CTX object.
211 SSL_CTX_up_ref() returns 1 for success and 0 for failure.
217 L<SSL_CTX_set_options(3)>, L<SSL_CTX_free(3)>, L<SSL_accept(3)>,
218 L<SSL_CTX_set_min_proto_version(3)>, L<ssl(7)>, L<SSL_set_connect_state(3)>
222 Support for SSLv2 and the corresponding SSLv2_method(),
223 SSLv2_server_method() and SSLv2_client_method() functions where
224 removed in OpenSSL 1.1.0.
226 SSLv23_method(), SSLv23_server_method() and SSLv23_client_method()
227 were deprecated and the preferred TLS_method(), TLS_server_method()
228 and TLS_client_method() functions were added in OpenSSL 1.1.0.
230 All version-specific methods were deprecated in OpenSSL 1.1.0.
232 SSL_CTX_new_ex() was added in OpenSSL 3.0.
236 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
238 Licensed under the Apache License 2.0 (the "License"). You may not use
239 this file except in compliance with the License. You can obtain a copy
240 in the file LICENSE in the source distribution or at
241 L<https://www.openssl.org/source/license.html>.