SSL_CTX_new(3)
- NetBSD Manual Pages
SSL_CTX_new(3) OpenSSL SSL_CTX_new(3)
NAME
SSL_CTX_new - create a new SSL_CTX object as framework for TLS/SSL
enabled functions
LIBRARY
libcrypto, -lcrypto
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 may understand
the SSLv2, SSLv3, TLSv1, TLSv1.1 and TLSv1.2 protocols.
If the cipher list does not contain any SSLv2 ciphersuites (the
default cipher list does not) or extensions are required (for
example server name) 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.
If any SSLv2 ciphersuites are included in the cipher list and no
extensions are required then SSLv2 compatible client hellos will be
used by clients and SSLv2 will be accepted by servers. This is not
recommended due to the insecurity of SSLv2 and the limited nature
of the SSLv2 client hello prohibiting the use of extensions.
The list of protocols available can later be limited using the
SSL_OP_NO_SSLv2, 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 e.g. 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.
Applications which never want to support SSLv2 (even is the cipher
string is configured to use SSLv2 ciphersuites) can set
SSL_OP_NO_SSLv2.
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)
1.0.1p 2014-08-10 SSL_CTX_new(3)
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