5 TLSv1_2_method, TLSv1_2_server_method, TLSv1_2_client_method,
6 SSL_CTX_new, SSL_CTX_up_ref, SSLv3_method, SSLv3_server_method,
7 SSLv3_client_method, TLSv1_method, TLSv1_server_method, TLSv1_client_method,
8 TLSv1_1_method, TLSv1_1_server_method, TLSv1_1_client_method, TLS_method,
9 TLS_server_method, TLS_client_method, SSLv23_method, SSLv23_server_method,
10 SSLv23_client_method, DTLS_method, DTLS_server_method, DTLS_client_method,
11 DTLSv1_method, DTLSv1_server_method, DTLSv1_client_method,
12 DTLSv1_2_method, DTLSv1_2_server_method, DTLSv1_2_client_method
13 - create a new SSL_CTX object as framework for TLS/SSL or DTLS enabled
18 #include <openssl/ssl.h>
20 SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);
21 int SSL_CTX_up_ref(SSL_CTX *ctx);
23 const SSL_METHOD *TLS_method(void);
24 const SSL_METHOD *TLS_server_method(void);
25 const SSL_METHOD *TLS_client_method(void);
27 const SSL_METHOD *SSLv23_method(void);
28 const SSL_METHOD *SSLv23_server_method(void);
29 const SSL_METHOD *SSLv23_client_method(void);
31 #ifndef OPENSSL_NO_SSL3_METHOD
32 const SSL_METHOD *SSLv3_method(void);
33 const SSL_METHOD *SSLv3_server_method(void);
34 const SSL_METHOD *SSLv3_client_method(void);
37 #ifndef OPENSSL_NO_TLS1_METHOD
38 const SSL_METHOD *TLSv1_method(void);
39 const SSL_METHOD *TLSv1_server_method(void);
40 const SSL_METHOD *TLSv1_client_method(void);
43 #ifndef OPENSSL_NO_TLS1_1_METHOD
44 const SSL_METHOD *TLSv1_1_method(void);
45 const SSL_METHOD *TLSv1_1_server_method(void);
46 const SSL_METHOD *TLSv1_1_client_method(void);
49 #ifndef OPENSSL_NO_TLS1_2_METHOD
50 const SSL_METHOD *TLSv1_2_method(void);
51 const SSL_METHOD *TLSv1_2_server_method(void);
52 const SSL_METHOD *TLSv1_2_client_method(void);
55 const SSL_METHOD *DTLS_method(void);
56 const SSL_METHOD *DTLS_server_method(void);
57 const SSL_METHOD *DTLS_client_method(void);
59 #ifndef OPENSSL_NO_DTLS1_METHOD
60 const SSL_METHOD *DTLSv1_method(void);
61 const SSL_METHOD *DTLSv1_server_method(void);
62 const SSL_METHOD *DTLSv1_client_method(void);
65 #ifndef OPENSSL_NO_DTLS1_2_METHOD
66 const SSL_METHOD *DTLSv1_2_method(void);
67 const SSL_METHOD *DTLSv1_2_server_method(void);
68 const SSL_METHOD *DTLSv1_2_client_method(void);
73 SSL_CTX_new() creates a new B<SSL_CTX> object as framework to
74 establish TLS/SSL or DTLS enabled connections. An B<SSL_CTX> object is
75 reference counted. Creating an B<SSL_CTX> object for the first time increments
76 the reference count. Freeing it (using SSL_CTX_free) decrements it. When the
77 reference count drops to zero, any memory or resources allocated to the
78 B<SSL_CTX> object are freed. SSL_CTX_up_ref() increments the reference count for
79 an existing B<SSL_CTX> structure.
83 The SSL_CTX object uses B<method> as connection method.
84 The methods exist in a generic type (for client and server use), a server only
85 type, and a client only type.
86 B<method> can be of the following types:
90 =item TLS_method(), TLS_server_method(), TLS_client_method()
92 These are the general-purpose I<version-flexible> SSL/TLS methods.
93 The actual protocol version used will be negotiated to the highest version
94 mutually supported by the client and the server.
95 The supported protocols are SSLv3, TLSv1, TLSv1.1, TLSv1.2 and TLSv1.3.
96 Applications should use these methods, and avoid the version-specific
97 methods described below.
99 =item SSLv23_method(), SSLv23_server_method(), SSLv23_client_method()
101 Use of these functions is deprecated. They have been replaced with the above
102 TLS_method(), TLS_server_method() and TLS_client_method() respectively. New
103 code should use those functions instead.
105 =item TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method()
107 A TLS/SSL connection established with these methods will only understand the
110 =item TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method()
112 A TLS/SSL connection established with these methods will only understand the
115 =item TLSv1_method(), TLSv1_server_method(), TLSv1_client_method()
117 A TLS/SSL connection established with these methods will only understand the
120 =item SSLv3_method(), SSLv3_server_method(), SSLv3_client_method()
122 A TLS/SSL connection established with these methods will only understand the
124 The SSLv3 protocol is deprecated and should not be used.
126 =item DTLS_method(), DTLS_server_method(), DTLS_client_method()
128 These are the version-flexible DTLS methods.
129 Currently supported protocols are DTLS 1.0 and DTLS 1.2.
131 =item DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method()
133 These are the version-specific methods for DTLSv1.2.
135 =item DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method()
137 These are the version-specific methods for DTLSv1.
141 SSL_CTX_new() initializes the list of ciphers, the session cache setting, the
142 callbacks, the keys and certificates and the options to their default values.
144 TLS_method(), TLS_server_method(), TLS_client_method(), DTLS_method(),
145 DTLS_server_method() and DTLS_client_method() are the I<version-flexible>
147 All other methods only support one specific protocol version.
148 Use the I<version-flexible> methods instead of the version specific methods.
150 If you want to limit the supported protocols for the version flexible
151 methods you can use L<SSL_CTX_set_min_proto_version(3)>,
152 L<SSL_set_min_proto_version(3)>, L<SSL_CTX_set_max_proto_version(3)> and
153 L<SSL_set_max_proto_version(3)> functions.
154 Using these functions it is possible to choose e.g. TLS_server_method()
155 and be able to negotiate with all possible clients, but to only
156 allow newer protocols like TLS 1.0, TLS 1.1, TLS 1.2 or TLS 1.3.
158 The list of protocols available can also be limited using the
159 B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>, B<SSL_OP_NO_TLSv1_1>,
160 B<SSL_OP_NO_TLSv1_3>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
162 L<SSL_CTX_set_options(3)> or L<SSL_set_options(3)> functions, but this approach
163 is not recommended. Clients should avoid creating "holes" in the set of
164 protocols they support. When disabling a protocol, make sure that you also
165 disable either all previous or all subsequent protocol versions.
166 In clients, when a protocol version is disabled without disabling I<all>
167 previous protocol versions, the effect is to also disable all subsequent
170 The SSLv3 protocol is deprecated and should generally not be used.
171 Applications should typically use L<SSL_CTX_set_min_proto_version(3)> to set
172 the minimum protocol to at least B<TLS1_VERSION>.
176 The following return values can occur:
182 The creation of a new SSL_CTX object failed. Check the error stack to find out
185 =item Pointer to an SSL_CTX object
187 The return value points to an allocated SSL_CTX object.
189 SSL_CTX_up_ref() returns 1 for success and 0 for failure.
195 Support for SSLv2 and the corresponding SSLv2_method(),
196 SSLv2_server_method() and SSLv2_client_method() functions where
197 removed in OpenSSL 1.1.0.
199 SSLv23_method(), SSLv23_server_method() and SSLv23_client_method()
200 were deprecated and the preferred TLS_method(), TLS_server_method()
201 and TLS_client_method() functions were introduced in OpenSSL 1.1.0.
203 All version-specific methods were deprecated in OpenSSL 1.1.0.
207 L<SSL_CTX_set_options(3)>, L<SSL_CTX_free(3)>, L<SSL_accept(3)>,
208 L<SSL_CTX_set_min_proto_version(3)>, L<ssl(7)>, L<SSL_set_connect_state(3)>
212 Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
214 Licensed under the OpenSSL license (the "License"). You may not use
215 this file except in compliance with the License. You can obtain a copy
216 in the file LICENSE in the source distribution or at
217 L<https://www.openssl.org/source/license.html>.