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)