=pod =head1 NAME TLSv1_2_method, TLSv1_2_server_method, TLSv1_2_client_method, SSL_CTX_new, SSL_CTX_up_ref, 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, TLS_method, TLS_server_method, TLS_client_method, SSLv23_method, SSLv23_server_method, SSLv23_client_method, DTLS_method, DTLS_server_method, DTLS_client_method, DTLSv1_method, DTLSv1_server_method, DTLSv1_client_method, DTLSv1_2_method, DTLSv1_2_server_method, DTLSv1_2_client_method - create a new SSL_CTX object as framework for TLS/SSL or DTLS enabled functions =head1 SYNOPSIS #include SSL_CTX *SSL_CTX_new(const SSL_METHOD *method); int SSL_CTX_up_ref(SSL_CTX *ctx); const SSL_METHOD *TLS_method(void); const SSL_METHOD *TLS_server_method(void); const SSL_METHOD *TLS_client_method(void); const SSL_METHOD *SSLv23_method(void); const SSL_METHOD *SSLv23_server_method(void); const SSL_METHOD *SSLv23_client_method(void); #ifndef OPENSSL_NO_SSL3_METHOD const SSL_METHOD *SSLv3_method(void); const SSL_METHOD *SSLv3_server_method(void); const SSL_METHOD *SSLv3_client_method(void); #endif #ifndef OPENSSL_NO_TLS1_METHOD const SSL_METHOD *TLSv1_method(void); const SSL_METHOD *TLSv1_server_method(void); const SSL_METHOD *TLSv1_client_method(void); #endif #ifndef OPENSSL_NO_TLS1_1_METHOD const SSL_METHOD *TLSv1_1_method(void); const SSL_METHOD *TLSv1_1_server_method(void); const SSL_METHOD *TLSv1_1_client_method(void); #endif #ifndef OPENSSL_NO_TLS1_2_METHOD const SSL_METHOD *TLSv1_2_method(void); const SSL_METHOD *TLSv1_2_server_method(void); const SSL_METHOD *TLSv1_2_client_method(void); #endif const SSL_METHOD *DTLS_method(void); const SSL_METHOD *DTLS_server_method(void); const SSL_METHOD *DTLS_client_method(void); #ifndef OPENSSL_NO_DTLS1_METHOD const SSL_METHOD *DTLSv1_method(void); const SSL_METHOD *DTLSv1_server_method(void); const SSL_METHOD *DTLSv1_client_method(void); #endif #ifndef OPENSSL_NO_DTLS1_2_METHOD const SSL_METHOD *DTLSv1_2_method(void); const SSL_METHOD *DTLSv1_2_server_method(void); const SSL_METHOD *DTLSv1_2_client_method(void); #endif =head1 DESCRIPTION SSL_CTX_new() creates a new B object as framework to establish TLS/SSL or DTLS enabled connections. An B object is reference counted. Creating an B object for the first time increments the reference count. Freeing it (using SSL_CTX_free) decrements it. When the reference count drops to zero, any memory or resources allocated to the B object are freed. SSL_CTX_up_ref() increments the reference count for an existing B structure. =head1 NOTES The SSL_CTX object uses B as connection method. The methods exist in a generic type (for client and server use), a server only type, and a client only type. B can be of the following types: =over 4 =item TLS_method(), TLS_server_method(), TLS_client_method() These are the general-purpose I SSL/TLS methods. The actual protocol version used will be negotiated to the highest version mutually supported by the client and the server. The supported protocols are SSLv3, TLSv1, TLSv1.1 and TLSv1.2. Applications should use these methods, and avoid the version-specific methods described below. =item SSLv23_method(), SSLv23_server_method(), SSLv23_client_method() Use of these functions is deprecated. They have been replaced with the above TLS_method(), TLS_server_method() and TLS_client_method() respectively. New code should use those functions instead. =item TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method() A TLS/SSL connection established with these methods will only understand the TLSv1.2 protocol. =item TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method() A TLS/SSL connection established with these methods will only understand the TLSv1.1 protocol. =item TLSv1_method(), TLSv1_server_method(), TLSv1_client_method() A TLS/SSL connection established with these methods will only understand the TLSv1 protocol. =item SSLv3_method(), SSLv3_server_method(), SSLv3_client_method() A TLS/SSL connection established with these methods will only understand the SSLv3 protocol. The SSLv3 protocol is deprecated and should not be used. =item DTLS_method(), DTLS_server_method(), DTLS_client_method() These are the version-flexible DTLS methods. Currently supported protocols are DTLS 1.0 and DTLS 1.2. =item DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method() These are the version-specific methods for DTLSv1.2. =item DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method() These are the version-specific methods for DTLSv1. =back SSL_CTX_new() initializes the list of ciphers, the session cache setting, the callbacks, the keys and certificates and the options to their default values. TLS_method(), TLS_server_method(), TLS_client_method(), DTLS_method(), DTLS_server_method() and DTLS_client_method() are the I methods. All other methods only support one specific protocol version. Use the I methods instead of the version specific methods. If you want to limit the supported protocols for the version flexible methods you can use L, L, L and L functions. Using these functions it is possible to choose e.g. TLS_server_method() and be able to negotiate with all possible clients, but to only allow newer protocols like TLS 1.0, TLS 1.1 or TLS 1.2. The list of protocols available can also be limited using the B, B, B, B and B options of the L or L functions, but this approach is not recommended. Clients should avoid creating "holes" in the set of protocols they support. When disabling a protocol, make sure that you also disable either all previous or all subsequent protocol versions. In clients, when a protocol version is disabled without disabling I previous protocol versions, the effect is to also disable all subsequent protocol versions. The SSLv3 protocol is deprecated and should generally not be used. Applications should typically use L to set the minimum protocol to at least B. =head1 RETURN VALUES The following return values can occur: =over 4 =item NULL The creation of a new SSL_CTX object failed. Check the error stack to find out the reason. =item Pointer to an SSL_CTX object The return value points to an allocated SSL_CTX object. SSL_CTX_up_ref() returns 1 for success and 0 for failure. =back =head1 HISTORY Support for SSLv2 and the corresponding SSLv2_method(), SSLv2_server_method() and SSLv2_client_method() functions where removed in OpenSSL 1.1.0. SSLv23_method(), SSLv23_server_method() and SSLv23_client_method() were deprecated and the preferred TLS_method(), TLS_server_method() and TLS_client_method() functions were introduced in OpenSSL 1.1.0. All version-specific methods were deprecated in OpenSSL 1.1.0. =head1 SEE ALSO L, L, L, L, L, L =head1 COPYRIGHT Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L. =cut