SSL_CTX_new.pod revision 76866 
1=pod
2
3=head1 NAME
4
5SSL_CTX_new - create a new SSL_CTX object as framework for TLS/SSL enabled functions
6
7=head1 SYNOPSIS
8
9 #include <openssl/ssl.h>
10
11 SSL_CTX *SSL_CTX_new(SSL_METHOD *method);
12
13=head1 DESCRIPTION
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15SSL_CTX_new() creates a new B<SSL_CTX> object as framework to establish
16TLS/SSL enabled connections.
17
18=head1 NOTES
19
20The SSL_CTX object uses B<method> as connection method. The methods exist
21in a generic type (for client and server use), a server only type, and a
22client only type. B<method> can be of the following types:
23
24=over 4
25
26=item SSLv2_method(void), SSLv2_server_method(void), SSLv2_client_method(void)
27
28A TLS/SSL connection established with these methods will only understand
29the SSLv2 protocol. A client will send out SSLv2 client hello messages
30and will also indicate that it only understand SSLv2. A server will only
31understand SSLv2 client hello messages.
32
33=item SSLv3_method(void), SSLv3_server_method(void), SSLv3_client_method(void)
34
35A TLS/SSL connection established with these methods will only understand the
36SSLv3 protocol. A client will send out SSLv3 client hello messages
37and will indicate that it only understands SSLv3. A server will only understand
38SSLv3 client hello messages. This especially means, that it will
39not understand SSLv2 client hello messages which are widely used for
40compatibility reasons, see SSLv23_*_method().
41
42=item TLSv1_method(void), TLSv1_server_method(void), TLSv1_client_method(void)
43
44A TLS/SSL connection established with these methods will only understand the
45TLSv1 protocol. A client will send out TLSv1 client hello messages
46and will indicate that it only understands TLSv1. A server will only understand
47TLSv1 client hello messages. This especially means, that it will
48not understand SSLv2 client hello messages which are widely used for
49compatibility reasons, see SSLv23_*_method(). It will also not understand
50SSLv3 client hello messages.
51
52=item SSLv23_method(void), SSLv23_server_method(void), SSLv23_client_method(void)
53
54A TLS/SSL connection established with these methods will understand the SSLv2,
55SSLv3, and TLSv1 protocol. A client will send out SSLv2 client hello messages
56and will indicate that it also understands SSLv3 and TLSv1. A server will
57understand SSLv2, SSLv3, and TLSv1 client hello messages. This is the best
58choice when compatibility is a concern.
59
60=back
61
62If a generic method is used, it is necessary to explicitly set client or
63server mode with L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>
64or SSL_set_accept_state().
65
66The list of protocols available can later be limited using the SSL_OP_NO_SSLv2,
67SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1 options of the B<SSL_CTX_set_options()> or
68B<SSL_set_options()> functions. Using these options it is possible to choose
69e.g. SSLv23_server_method() and be able to negotiate with all possible
70clients, but to only allow newer protocols like SSLv3 or TLSv1.
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72SSL_CTX_new() initializes the list of ciphers, the session cache setting,
73the callbacks, the keys and certificates, and the options to its default
74values.
75
76=head1 RETURN VALUES
77
78The following return values can occur:
79
80=over 4
81
82=item NULL
83
84The creation of a new SSL_CTX object failed. Check the error stack to
85find out the reason.
86
87=item Pointer to an SSL_CTX object
88
89The return value points to an allocated SSL_CTX object.
90
91=back
92
93=head1 SEE ALSO
94
95L<SSL_CTX_free(3)|SSL_CTX_free(3)>, L<SSL_accept(3)|SSL_accept(3)>,
96L<ssl(3)|ssl(3)>,  L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>
97
98=cut
99