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)