SSL_CTX_new.pod revision 296317 
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,
12DTLSv1_method, DTLSv1_server_method, DTLSv1_client_method -
13create a new SSL_CTX object as framework for TLS/SSL enabled functions
14
15=head1 SYNOPSIS
16
17 #include <openssl/ssl.h>
18
19 SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);
20 const SSL_METHOD *SSLv23_method(void);
21 const SSL_METHOD *SSLv23_server_method(void);
22 const SSL_METHOD *SSLv23_client_method(void);
23 const SSL_METHOD *TLSv1_2_method(void);
24 const SSL_METHOD *TLSv1_2_server_method(void);
25 const SSL_METHOD *TLSv1_2_client_method(void);
26 const SSL_METHOD *TLSv1_1_method(void);
27 const SSL_METHOD *TLSv1_1_server_method(void);
28 const SSL_METHOD *TLSv1_1_client_method(void);
29 const SSL_METHOD *TLSv1_method(void);
30 const SSL_METHOD *TLSv1_server_method(void);
31 const SSL_METHOD *TLSv1_client_method(void);
32 #ifndef OPENSSL_NO_SSL3_METHOD
33 const SSL_METHOD *SSLv3_method(void);
34 const SSL_METHOD *SSLv3_server_method(void);
35 const SSL_METHOD *SSLv3_client_method(void);
36 #endif
37 #ifndef OPENSSL_NO_SSL2
38 const SSL_METHOD *SSLv2_method(void);
39 const SSL_METHOD *SSLv2_server_method(void);
40 const SSL_METHOD *SSLv2_client_method(void);
41 #endif
42
43 const SSL_METHOD *DTLSv1_method(void);
44 const SSL_METHOD *DTLSv1_server_method(void);
45 const SSL_METHOD *DTLSv1_client_method(void);
46
47=head1 DESCRIPTION
48
49SSL_CTX_new() creates a new B<SSL_CTX> object as framework to establish
50TLS/SSL enabled connections.
51
52=head1 NOTES
53
54The SSL_CTX object uses B<method> as connection method. The methods exist
55in a generic type (for client and server use), a server only type, and a
56client only type. B<method> can be of the following types:
57
58=over 4
59
60=item SSLv23_method(), SSLv23_server_method(), SSLv23_client_method()
61
62These are the general-purpose I<version-flexible> SSL/TLS methods.
63The actual protocol version used will be negotiated to the highest version
64mutually supported by the client and the server.
65The supported protocols are SSLv2, SSLv3, TLSv1, TLSv1.1 and TLSv1.2.
66Most applications should use these method, and avoid the version specific
67methods described below.
68
69The list of protocols available can be further limited using the
70B<SSL_OP_NO_SSLv2>, B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
71B<SSL_OP_NO_TLSv1_1> and B<SSL_OP_NO_TLSv1_2> options of the
72L<SSL_CTX_set_options(3)> or L<SSL_set_options(3)> functions.
73Clients should avoid creating "holes" in the set of protocols they support,
74when disabling a protocol, make sure that you also disable either all previous
75or all subsequent protocol versions.
76In clients, when a protocol version is disabled without disabling I<all>
77previous protocol versions, the effect is to also disable all subsequent
78protocol versions.
79
80The SSLv2 and SSLv3 protocols are deprecated and should generally not be used.
81Applications should typically use L<SSL_CTX_set_options(3)> in combination with
82the B<SSL_OP_NO_SSLv3> flag to disable negotiation of SSLv3 via the above
83I<version-flexible> SSL/TLS methods.
84The B<SSL_OP_NO_SSLv2> option is set by default, and would need to be cleared
85via L<SSL_CTX_clear_options(3)> in order to enable negotiation of SSLv2.
86
87=item TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method()
88
89A TLS/SSL connection established with these methods will only understand the
90TLSv1.2 protocol.  A client will send out TLSv1.2 client hello messages and
91will also indicate that it only understand TLSv1.2.  A server will only
92understand TLSv1.2 client hello messages.
93
94=item TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method()
95
96A TLS/SSL connection established with these methods will only understand the
97TLSv1.1 protocol.  A client will send out TLSv1.1 client hello messages and
98will also indicate that it only understand TLSv1.1.  A server will only
99understand TLSv1.1 client hello messages.
100
101=item TLSv1_method(), TLSv1_server_method(), TLSv1_client_method()
102
103A TLS/SSL connection established with these methods will only understand the
104TLSv1 protocol.  A client will send out TLSv1 client hello messages and will
105indicate that it only understands TLSv1.  A server will only understand TLSv1
106client hello messages.
107
108=item SSLv3_method(), SSLv3_server_method(), SSLv3_client_method()
109
110A TLS/SSL connection established with these methods will only understand the
111SSLv3 protocol.  A client will send out SSLv3 client hello messages and will
112indicate that it only understands SSLv3.  A server will only understand SSLv3
113client hello messages.  The SSLv3 protocol is deprecated and should not be
114used.
115
116=item SSLv2_method(), SSLv2_server_method(), SSLv2_client_method()
117
118A TLS/SSL connection established with these methods will only understand the
119SSLv2 protocol.  A client will send out SSLv2 client hello messages and will
120also indicate that it only understand SSLv2.  A server will only understand
121SSLv2 client hello messages.  The SSLv2 protocol offers little to no security
122and should not be used.
123As of OpenSSL 1.0.1s, EXPORT ciphers and 56-bit DES are no longer available
124with SSLv2.
125
126=item DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method()
127
128These are the version-specific methods for DTLSv1.
129
130=back
131
132SSL_CTX_new() initializes the list of ciphers, the session cache setting, the
133callbacks, the keys and certificates and the options to its default values.
134
135=head1 RETURN VALUES
136
137The following return values can occur:
138
139=over 4
140
141=item NULL
142
143The creation of a new SSL_CTX object failed. Check the error stack to find out
144the reason.
145
146=item Pointer to an SSL_CTX object
147
148The return value points to an allocated SSL_CTX object.
149
150=back
151
152=head1 SEE ALSO
153
154L<SSL_CTX_set_options(3)>, L<SSL_CTX_clear_options(3)>, L<SSL_set_options(3)>,
155L<SSL_CTX_free(3)|SSL_CTX_free(3)>, L<SSL_accept(3)|SSL_accept(3)>,
156L<ssl(3)|ssl(3)>,  L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>
157
158=cut
159