NAME
SSL_CTX_new,
SSLv3_method,
SSLv3_server_method,
SSLv3_client_method,
TLSv1_method,
TLSv1_server_method,
TLSv1_client_method,
TLSv1_1_method,
TLSv1_1_server_method,
TLSv1_1_client_method,
SSLv23_method,
SSLv23_server_method,
SSLv23_client_method —
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 its 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:
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. Importantly, this 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. Importantly, this 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 may understand the
SSLv3, TLSv1, TLSv1.1 and TLSv1.2 protocols.
A client will send out TLSv1 client hello messages including extensions and will indicate that it also understands TLSv1.1, TLSv1.2 and permits a fallback to SSLv3. A server will support SSLv3, TLSv1, TLSv1.1 and TLSv1.2 protocols. This is the best choice when compatibility is a concern.
The list of protocols available can later
be limited using the SSL_OP_NO_SSLv3,
SSL_OP_NO_TLSv1,
SSL_OP_NO_TLSv1_1, and
SSL_OP_NO_TLSv1_2 options of the
SSL_CTX_set_options()
or
SSL_set_options()
functions. Using these options it is possible to choose, for example,
SSLv23_server_method()
and be able to negotiate with all possible clients, but to only allow newer
protocols like TLSv1, TLSv1.1 or TLS v1.2.
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(3), SSL_accept(3), SSL_CTX_free(3), SSL_set_connect_state(3)