NAME

       SSL_CTX_new - create a new SSL_CTX object as framework for TLS/SSL enabled functions

SYNOPSIS

        #include <openssl/ssl.h>

        SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);

DESCRIPTION

       SSL_CTX_new() creates a new SSL_CTX object as framework to establish TLS/SSL enabled
       connections.

NOTES

       The SSL_CTX object uses method as connection method. The methods exist in a generic type
       (for client and server use), a server only type, and a client only type. method can be of
       the following types:

       SSLv2_method(void), SSLv2_server_method(void), SSLv2_client_method(void)
           A TLS/SSL connection established with these methods will only understand the SSLv2
           protocol. A client will send out SSLv2 client hello messages and will also indicate
           that it only understand SSLv2. A server will only understand SSLv2 client hello
           messages.

       SSLv3_method(void), SSLv3_server_method(void), SSLv3_client_method(void)
           A TLS/SSL connection established with these methods will only understand the SSLv3
           protocol. A client will send out SSLv3 client hello messages and will indicate that it
           only understands SSLv3. A server will only understand SSLv3 client hello messages.
           This especially means, that it will not understand SSLv2 client hello messages which
           are widely used for compatibility reasons, see SSLv23_*_method().

       TLSv1_method(void), TLSv1_server_method(void), TLSv1_client_method(void)
           A TLS/SSL connection established with these methods will only understand the TLSv1
           protocol. A client will send out TLSv1 client hello messages and will indicate that it
           only understands TLSv1. A server will only understand TLSv1 client hello messages.
           This especially means, that it will not understand SSLv2 client hello messages which
           are widely used for compatibility reasons, see SSLv23_*_method(). It will also not
           understand SSLv3 client hello messages.

       SSLv23_method(void), SSLv23_server_method(void), SSLv23_client_method(void)
           A TLS/SSL connection established with these methods will understand the SSLv2, SSLv3,
           and TLSv1 protocol. A client will send out SSLv2 client hello messages and will
           indicate that it also understands SSLv3 and TLSv1. A server will understand SSLv2,
           SSLv3, and TLSv1 client hello messages. This is the best choice when compatibility is
           a concern.

       The list of protocols available can later be limited using the SSL_OP_NO_SSLv2,
       SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1 options of the SSL_CTX_set_options() or SSL_set_options()
       functions. Using these options it is possible to choose e.g. SSLv23_server_method() and be
       able to negotiate with all possible clients, but to only allow newer protocols like SSLv3
       or TLSv1.

       SSL_CTX_new() initializes the list of ciphers, the session cache setting, the callbacks,
       the keys and certificates, and the options to its default values.

RETURN VALUES

       The following return values can occur:

       NULL
           The creation of a new SSL_CTX object failed. Check the error stack to find out the
           reason.

       Pointer to an SSL_CTX object
           The return value points to an allocated SSL_CTX object.

SEE ALSO

       SSL_CTX_free(3), SSL_accept(3), ssl(3),  SSL_set_connect_state(3)