SSL_CTX_new

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_new_ex, 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

SYNOPSIS
        #include <openssl/ssl.h>

        SSL_CTX *SSL_CTX_new_ex(OSSL_LIB_CTX *libctx, const char *propq,
                                const SSL_METHOD *method);
        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_ex() creates a new SSL_CTX object, which holds various
       configuration and data relevant to TLS/SSL or DTLS session establishment.
       The library context libctx (see OSSL_LIB_CTX(3)) is used to provide the
       cryptographic algorithms needed for the session. Any cryptographic
       algorithms that are used by any SSL objects created from this SSL_CTX
       will be fetched from the libctx using the property query string propq
       (see "Fetching algorithms" in provider(7). Either or both the libctx or
       propq parameters may be NULL.

       SSL_CTX_new() does the same as SSL_CTX_new_ex() except that the default
       library context is used and no property query string is specified.

       An SSL_CTX object is reference counted. Creating an SSL_CTX object for
       the first time increments the reference count. Freeing the SSL_CTX (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.

       An SSL_CTX object should not be changed after it is used to create any
       SSL objects or from multiple threads concurrently, since the
       implementation does not provide serialization of access for these cases.

NOTES
       The SSL_CTX object uses method as the 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 one 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.

       SSL_CTX_new_ex() was added in OpenSSL 3.0.

COPYRIGHT
       Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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>.



3.0.0-alpha12                      2021-02-18                     SSL_CTX_NEW(3)