1=pod
2
3=head1 NAME
4
5SSL_CTX_new,
6SSLv23_method, SSLv23_server_method, SSLv23_client_method,
7TLSv1_2_method, TLSv1_2_server_method, TLSv1_2_client_method,
8TLSv1_1_method, TLSv1_1_server_method, TLSv1_1_client_method,
9TLSv1_method, TLSv1_server_method, TLSv1_client_method,
10SSLv3_method, SSLv3_server_method, SSLv3_client_method,
11SSLv2_method, SSLv2_server_method, SSLv2_client_method,
12DTLS_method, DTLS_server_method, DTLS_client_method,
13DTLSv1_2_method, DTLSv1_2_server_method, DTLSv1_2_client_method,
14DTLSv1_method, DTLSv1_server_method, DTLSv1_client_method -
15create a new SSL_CTX object as framework for TLS/SSL enabled functions
16
17=head1 SYNOPSIS
18
19 #include <openssl/ssl.h>
20
21 SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);
22 const SSL_METHOD *SSLv23_method(void);
23 const SSL_METHOD *SSLv23_server_method(void);
24 const SSL_METHOD *SSLv23_client_method(void);
25 const SSL_METHOD *TLSv1_2_method(void);
26 const SSL_METHOD *TLSv1_2_server_method(void);
27 const SSL_METHOD *TLSv1_2_client_method(void);
28 const SSL_METHOD *TLSv1_1_method(void);
29 const SSL_METHOD *TLSv1_1_server_method(void);
30 const SSL_METHOD *TLSv1_1_client_method(void);
31 const SSL_METHOD *TLSv1_method(void);
32 const SSL_METHOD *TLSv1_server_method(void);
33 const SSL_METHOD *TLSv1_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);
38 #endif
39 #ifndef OPENSSL_NO_SSL2
40 const SSL_METHOD *SSLv2_method(void);
41 const SSL_METHOD *SSLv2_server_method(void);
42 const SSL_METHOD *SSLv2_client_method(void);
43 #endif
44
45 const SSL_METHOD *DTLS_method(void);
46 const SSL_METHOD *DTLS_server_method(void);
47 const SSL_METHOD *DTLS_client_method(void);
48 const SSL_METHOD *DTLSv1_2_method(void);
49 const SSL_METHOD *DTLSv1_2_server_method(void);
50 const SSL_METHOD *DTLSv1_2_client_method(void);
51 const SSL_METHOD *DTLSv1_method(void);
52 const SSL_METHOD *DTLSv1_server_method(void);
53 const SSL_METHOD *DTLSv1_client_method(void);
54
55=head1 DESCRIPTION
56
57SSL_CTX_new() creates a new B<SSL_CTX> object as framework to establish
58TLS/SSL enabled connections.
59
60=head1 NOTES
61
62The SSL_CTX object uses B<method> as connection method. The methods exist
63in a generic type (for client and server use), a server only type, and a
64client only type. B<method> can be of the following types:
65
66=over 4
67
68=item SSLv23_method(), SSLv23_server_method(), SSLv23_client_method()
69
70These are the general-purpose I<version-flexible> SSL/TLS methods.
71The actual protocol version used will be negotiated to the highest version
72mutually supported by the client and the server.
73The supported protocols are SSLv2, SSLv3, TLSv1, TLSv1.1 and TLSv1.2.
74Most applications should use these method, and avoid the version specific
75methods described below.
76
77The list of protocols available can be further limited using the
78B<SSL_OP_NO_SSLv2>, B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
79B<SSL_OP_NO_TLSv1_1> and B<SSL_OP_NO_TLSv1_2> options of the
80L<SSL_CTX_set_options(3)> or L<SSL_set_options(3)> functions.
81Clients should avoid creating "holes" in the set of protocols they support,
82when disabling a protocol, make sure that you also disable either all previous
83or all subsequent protocol versions.
84In clients, when a protocol version is disabled without disabling I<all>
85previous protocol versions, the effect is to also disable all subsequent
86protocol versions.
87
88The SSLv2 and SSLv3 protocols are deprecated and should generally not be used.
89Applications should typically use L<SSL_CTX_set_options(3)> in combination with
90the B<SSL_OP_NO_SSLv3> flag to disable negotiation of SSLv3 via the above
91I<version-flexible> SSL/TLS methods.
92The B<SSL_OP_NO_SSLv2> option is set by default, and would need to be cleared
93via L<SSL_CTX_clear_options(3)> in order to enable negotiation of SSLv2.
94
95=item TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method()
96
97A TLS/SSL connection established with these methods will only understand the
98TLSv1.2 protocol.  A client will send out TLSv1.2 client hello messages and
99will also indicate that it only understand TLSv1.2.  A server will only
100understand TLSv1.2 client hello messages.
101
102=item TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method()
103
104A TLS/SSL connection established with these methods will only understand the
105TLSv1.1 protocol.  A client will send out TLSv1.1 client hello messages and
106will also indicate that it only understand TLSv1.1.  A server will only
107understand TLSv1.1 client hello messages.
108
109=item TLSv1_method(), TLSv1_server_method(), TLSv1_client_method()
110
111A TLS/SSL connection established with these methods will only understand the
112TLSv1 protocol.  A client will send out TLSv1 client hello messages and will
113indicate that it only understands TLSv1.  A server will only understand TLSv1
114client hello messages.
115
116=item SSLv3_method(), SSLv3_server_method(), SSLv3_client_method()
117
118A TLS/SSL connection established with these methods will only understand the
119SSLv3 protocol.  A client will send out SSLv3 client hello messages and will
120indicate that it only understands SSLv3.  A server will only understand SSLv3
121client hello messages.  The SSLv3 protocol is deprecated and should not be
122used.
123
124=item SSLv2_method(), SSLv2_server_method(), SSLv2_client_method()
125
126A TLS/SSL connection established with these methods will only understand the
127SSLv2 protocol.  A client will send out SSLv2 client hello messages and will
128also indicate that it only understand SSLv2.  A server will only understand
129SSLv2 client hello messages.  The SSLv2 protocol offers little to no security
130and should not be used.
131As of OpenSSL 1.0.2g, EXPORT ciphers and 56-bit DES are no longer available
132with SSLv2.
133
134=item DTLS_method(), DTLS_server_method(), DTLS_client_method()
135
136These are the version-flexible DTLS methods.
137
138=item DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method()
139
140These are the version-specific methods for DTLSv1.2.
141
142=item DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method()
143
144These are the version-specific methods for DTLSv1.
145
146=back
147
148SSL_CTX_new() initializes the list of ciphers, the session cache setting, the
149callbacks, the keys and certificates and the options to its default values.
150
151=head1 RETURN VALUES
152
153The following return values can occur:
154
155=over 4
156
157=item NULL
158
159The creation of a new SSL_CTX object failed. Check the error stack to find out
160the reason.
161
162=item Pointer to an SSL_CTX object
163
164The return value points to an allocated SSL_CTX object.
165
166=back
167
168=head1 SEE ALSO
169
170L<SSL_CTX_set_options(3)>, L<SSL_CTX_clear_options(3)>, L<SSL_set_options(3)>,
171L<SSL_CTX_free(3)|SSL_CTX_free(3)>, L<SSL_accept(3)|SSL_accept(3)>,
172L<ssl(3)|ssl(3)>,  L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>
173
174=cut
175