Updated: 2021/Apr/14


SSL_CTX_new(3)                      OpenSSL                     SSL_CTX_new(3)



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

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/ssl.h>

        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

DESCRIPTION
       SSL_CTX_new() creates a new SSL_CTX object as framework to establish
       TLS/SSL or DTLS enabled connections. An SSL_CTX object is reference
       counted. Creating an SSL_CTX 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 SSL_CTX object are freed. SSL_CTX_up_ref() increments the reference
       count for an existing SSL_CTX structure.

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:

       TLS_method(), TLS_server_method(), TLS_client_method()
           These are the general-purpose version-flexible 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, TLSv1.2 and TLSv1.3.
           Applications should use these methods, and avoid the version-
           specific methods described below, which are deprecated.

       SSLv23_method(), SSLv23_server_method(), SSLv23_client_method()
           These functions do not exist anymore, they have been renamed to
           TLS_method(), TLS_server_method() and TLS_client_method()
           respectively.  Currently, the old function calls are renamed to the
           corresponding new ones by preprocessor macros, to ensure that
           existing code which uses the old function names still compiles.
           However, using the old function names is deprecated and new code
           should call the new functions instead.

       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. These methods are deprecated.

       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.  These methods are deprecated.

       TLSv1_method(), TLSv1_server_method(), TLSv1_client_method()
           A TLS/SSL connection established with these methods will only
           understand the TLSv1 protocol. These methods are deprecated.

       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.

       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.

       DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method()
           These are the version-specific methods for DTLSv1.2.  These methods
           are deprecated.

       DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method()
           These are the version-specific methods for DTLSv1.  These methods
           are deprecated.

       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 version-flexible
       methods.  All other methods only support one specific protocol version.
       Use the version-flexible methods instead of the version specific
       methods.

       If you want to limit the supported protocols for the version flexible
       methods you can use SSL_CTX_set_min_proto_version(3),
       SSL_set_min_proto_version(3), SSL_CTX_set_max_proto_version(3) and
       SSL_set_max_proto_version(3) 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, TLS 1.2 or TLS 1.3.

       The list of protocols available can also be limited using the
       SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1, SSL_OP_NO_TLSv1_1, SSL_OP_NO_TLSv1_3,
       SSL_OP_NO_TLSv1_2 and SSL_OP_NO_TLSv1_3 options of the
       SSL_CTX_set_options(3) or SSL_set_options(3) 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 all 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 SSL_CTX_set_min_proto_version(3) to
       set the minimum protocol to at least TLS1_VERSION.

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.

           SSL_CTX_up_ref() returns 1 for success and 0 for failure.

SEE ALSO
       SSL_CTX_set_options(3), SSL_CTX_free(3), SSL_accept(3),
       SSL_CTX_set_min_proto_version(3), ssl(7), SSL_set_connect_state(3)

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 added in OpenSSL 1.1.0.

       All version-specific methods were deprecated in OpenSSL 1.1.0.

COPYRIGHT
       Copyright 2000-2019 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
       <https://www.openssl.org/source/license.html>.



1.1.1i                            2020-01-23                    SSL_CTX_new(3)