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, which are deprecated.
99 =item SSLv23_method(), SSLv23_server_method(), SSLv23_client_method()
101 These functions do not exist anymore, they have been renamed to
102 TLS_method(), TLS_server_method() and TLS_client_method() respectively.
103 Currently, the old function calls are renamed to the corresponding new
104 ones by preprocessor macros, to ensure that existing code which uses the
105 old function names still compiles. However, using the old function names
106 is deprecated and new code should call the new functions instead.
108 =item TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method()
110 A TLS/SSL connection established with these methods will only understand the
111 TLSv1.2 protocol. These methods are deprecated.
113 =item TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method()
115 A TLS/SSL connection established with these methods will only understand the
116 TLSv1.1 protocol. These methods are deprecated.
118 =item TLSv1_method(), TLSv1_server_method(), TLSv1_client_method()
120 A TLS/SSL connection established with these methods will only understand the
121 TLSv1 protocol. These methods are deprecated.
123 =item SSLv3_method(), SSLv3_server_method(), SSLv3_client_method()
125 A TLS/SSL connection established with these methods will only understand the
127 The SSLv3 protocol is deprecated and should not be used.
129 =item DTLS_method(), DTLS_server_method(), DTLS_client_method()
131 These are the version-flexible DTLS methods.
132 Currently supported protocols are DTLS 1.0 and DTLS 1.2.
134 =item DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method()
136 These are the version-specific methods for DTLSv1.2.
137 These methods are deprecated.
139 =item DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method()
141 These are the version-specific methods for DTLSv1.
142 These methods are deprecated.
146 SSL_CTX_new() initializes the list of ciphers, the session cache setting, the
147 callbacks, the keys and certificates and the options to their default values.
149 TLS_method(), TLS_server_method(), TLS_client_method(), DTLS_method(),
150 DTLS_server_method() and DTLS_client_method() are the I<version-flexible>
152 All other methods only support one specific protocol version.
153 Use the I<version-flexible> methods instead of the version specific methods.
155 If you want to limit the supported protocols for the version flexible
156 methods you can use L<SSL_CTX_set_min_proto_version(3)>,
157 L<SSL_set_min_proto_version(3)>, L<SSL_CTX_set_max_proto_version(3)> and
158 L<SSL_set_max_proto_version(3)> functions.
159 Using these functions it is possible to choose e.g. TLS_server_method()
160 and be able to negotiate with all possible clients, but to only
161 allow newer protocols like TLS 1.0, TLS 1.1, TLS 1.2 or TLS 1.3.
163 The list of protocols available can also be limited using the
164 B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>, B<SSL_OP_NO_TLSv1_1>,
165 B<SSL_OP_NO_TLSv1_3>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
167 L<SSL_CTX_set_options(3)> or L<SSL_set_options(3)> functions, but this approach
168 is not recommended. Clients should avoid creating "holes" in the set of
169 protocols they support. When disabling a protocol, make sure that you also
170 disable either all previous or all subsequent protocol versions.
171 In clients, when a protocol version is disabled without disabling I<all>
172 previous protocol versions, the effect is to also disable all subsequent
175 The SSLv3 protocol is deprecated and should generally not be used.
176 Applications should typically use L<SSL_CTX_set_min_proto_version(3)> to set
177 the minimum protocol to at least B<TLS1_VERSION>.
181 The following return values can occur:
187 The creation of a new SSL_CTX object failed. Check the error stack to find out
190 =item Pointer to an SSL_CTX object
192 The return value points to an allocated SSL_CTX object.
194 SSL_CTX_up_ref() returns 1 for success and 0 for failure.
200 L<SSL_CTX_set_options(3)>, L<SSL_CTX_free(3)>, L<SSL_accept(3)>,
201 L<SSL_CTX_set_min_proto_version(3)>, L<ssl(7)>, L<SSL_set_connect_state(3)>
205 Support for SSLv2 and the corresponding SSLv2_method(),
206 SSLv2_server_method() and SSLv2_client_method() functions where
207 removed in OpenSSL 1.1.0.
209 SSLv23_method(), SSLv23_server_method() and SSLv23_client_method()
210 were deprecated and the preferred TLS_method(), TLS_server_method()
211 and TLS_client_method() functions were added in OpenSSL 1.1.0.
213 All version-specific methods were deprecated in OpenSSL 1.1.0.
217 Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
219 Licensed under the Apache License 2.0 (the "License"). You may not use
220 this file except in compliance with the License. You can obtain a copy
221 in the file LICENSE in the source distribution or at
222 L<https://www.openssl.org/source/license.html>.