mirror of https://github.com/openssl/openssl
260 lines
9.9 KiB
Plaintext
260 lines
9.9 KiB
Plaintext
=pod
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=head1 NAME
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TLSv1_2_method, TLSv1_2_server_method, TLSv1_2_client_method,
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SSL_CTX_new, SSL_CTX_new_ex, SSL_CTX_up_ref, SSLv3_method,
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SSLv3_server_method, SSLv3_client_method, TLSv1_method, TLSv1_server_method,
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TLSv1_client_method, TLSv1_1_method, TLSv1_1_server_method,
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TLSv1_1_client_method, TLS_method, TLS_server_method, TLS_client_method,
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SSLv23_method, SSLv23_server_method, SSLv23_client_method, DTLS_method,
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DTLS_server_method, DTLS_client_method, DTLSv1_method, DTLSv1_server_method,
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DTLSv1_client_method, DTLSv1_2_method, DTLSv1_2_server_method,
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DTLSv1_2_client_method
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- create a new SSL_CTX object as framework for TLS/SSL or DTLS enabled
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functions
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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SSL_CTX *SSL_CTX_new_ex(OSSL_LIB_CTX *libctx, const char *propq,
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const SSL_METHOD *method);
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SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);
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int SSL_CTX_up_ref(SSL_CTX *ctx);
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const SSL_METHOD *TLS_method(void);
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const SSL_METHOD *TLS_server_method(void);
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const SSL_METHOD *TLS_client_method(void);
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const SSL_METHOD *SSLv23_method(void);
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const SSL_METHOD *SSLv23_server_method(void);
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const SSL_METHOD *SSLv23_client_method(void);
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#ifndef OPENSSL_NO_SSL3_METHOD
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const SSL_METHOD *SSLv3_method(void);
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const SSL_METHOD *SSLv3_server_method(void);
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const SSL_METHOD *SSLv3_client_method(void);
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#endif
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#ifndef OPENSSL_NO_TLS1_METHOD
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const SSL_METHOD *TLSv1_method(void);
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const SSL_METHOD *TLSv1_server_method(void);
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const SSL_METHOD *TLSv1_client_method(void);
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#endif
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#ifndef OPENSSL_NO_TLS1_1_METHOD
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const SSL_METHOD *TLSv1_1_method(void);
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const SSL_METHOD *TLSv1_1_server_method(void);
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const SSL_METHOD *TLSv1_1_client_method(void);
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#endif
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#ifndef OPENSSL_NO_TLS1_2_METHOD
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const SSL_METHOD *TLSv1_2_method(void);
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const SSL_METHOD *TLSv1_2_server_method(void);
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const SSL_METHOD *TLSv1_2_client_method(void);
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#endif
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const SSL_METHOD *DTLS_method(void);
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const SSL_METHOD *DTLS_server_method(void);
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const SSL_METHOD *DTLS_client_method(void);
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#ifndef OPENSSL_NO_DTLS1_METHOD
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const SSL_METHOD *DTLSv1_method(void);
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const SSL_METHOD *DTLSv1_server_method(void);
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const SSL_METHOD *DTLSv1_client_method(void);
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#endif
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#ifndef OPENSSL_NO_DTLS1_2_METHOD
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const SSL_METHOD *DTLSv1_2_method(void);
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const SSL_METHOD *DTLSv1_2_server_method(void);
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const SSL_METHOD *DTLSv1_2_client_method(void);
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#endif
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=head1 DESCRIPTION
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SSL_CTX_new_ex() creates a new B<SSL_CTX> object, which holds various
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configuration and data relevant to SSL/TLS or DTLS session establishment.
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These are later inherited by the B<SSL> object representing an active session.
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The I<method> parameter specifies whether the context will be used for the
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client or server side or both - for details see the L</NOTES> below.
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The library context I<libctx> (see L<OSSL_LIB_CTX(3)>) is used to provide the
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cryptographic algorithms needed for the session. Any cryptographic algorithms
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that are used by any B<SSL> objects created from this B<SSL_CTX> will be fetched
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from the I<libctx> using the property query string I<propq> (see
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L<crypto(7)/ALGORITHM FETCHING>. Either or both the I<libctx> or I<propq>
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parameters may be NULL.
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SSL_CTX_new() does the same as SSL_CTX_new_ex() except that the default
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library context is used and no property query string is specified.
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An B<SSL_CTX> object is reference counted. Creating an B<SSL_CTX> object for the
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first time increments the reference count. Freeing the B<SSL_CTX> (using
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SSL_CTX_free) decrements it. When the reference count drops to zero, any memory
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or resources allocated to the B<SSL_CTX> object are freed. SSL_CTX_up_ref()
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increments the reference count for an existing B<SSL_CTX> structure.
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An B<SSL_CTX> object should not be changed after it is used to create any B<SSL>
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objects or from multiple threads concurrently, since the implementation does not
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provide serialization of access for these cases.
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=head1 NOTES
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On session establishment, by default, no peer credentials verification is done.
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This must be explicitly requested, typically using L<SSL_CTX_set_verify(3)>.
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For verifying peer certificates many options can be set using various functions
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such as L<SSL_CTX_load_verify_locations(3)> and L<SSL_CTX_set1_param(3)>.
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The L<X509_VERIFY_PARAM_set_purpose(3)> function can be used, also in conjunction
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with L<SSL_CTX_get0_param(3)>, to set the intended purpose of the session.
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The default is B<X509_PURPOSE_SSL_SERVER> on the client side
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and B<X509_PURPOSE_SSL_CLIENT> on the server side.
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The SSL_CTX object uses I<method> as the connection method.
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Three method variants are available: a generic method (for either client or
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server use), a server-only method, and a client-only method.
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The I<method> parameter of SSL_CTX_new_ex() and SSL_CTX_new()
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can be one of the following:
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=over 4
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=item TLS_method(), TLS_server_method(), TLS_client_method()
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These are the general-purpose I<version-flexible> SSL/TLS methods.
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The actual protocol version used will be negotiated to the highest version
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mutually supported by the client and the server.
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The supported protocols are SSLv3, TLSv1, TLSv1.1, TLSv1.2 and TLSv1.3.
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Applications should use these methods, and avoid the version-specific
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methods described below, which are deprecated.
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=item SSLv23_method(), SSLv23_server_method(), SSLv23_client_method()
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These functions do not exist anymore, they have been renamed to
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TLS_method(), TLS_server_method() and TLS_client_method() respectively.
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Currently, the old function calls are renamed to the corresponding new
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ones by preprocessor macros, to ensure that existing code which uses the
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old function names still compiles. However, using the old function names
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is deprecated and new code should call the new functions instead.
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=item TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method()
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A TLS/SSL connection established with these methods will only understand the
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TLSv1.2 protocol. These methods are deprecated.
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=item TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method()
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A TLS/SSL connection established with these methods will only understand the
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TLSv1.1 protocol. These methods are deprecated.
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=item TLSv1_method(), TLSv1_server_method(), TLSv1_client_method()
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A TLS/SSL connection established with these methods will only understand the
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TLSv1 protocol. These methods are deprecated.
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=item SSLv3_method(), SSLv3_server_method(), SSLv3_client_method()
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A TLS/SSL connection established with these methods will only understand the
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SSLv3 protocol.
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The SSLv3 protocol is deprecated and should not be used.
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=item DTLS_method(), DTLS_server_method(), DTLS_client_method()
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These are the version-flexible DTLS methods.
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Currently supported protocols are DTLS 1.0 and DTLS 1.2.
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=item DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method()
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These are the version-specific methods for DTLSv1.2.
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These methods are deprecated.
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=item DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method()
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These are the version-specific methods for DTLSv1.
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These methods are deprecated.
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=back
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SSL_CTX_new() initializes the list of ciphers, the session cache setting, the
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callbacks, the keys and certificates and the options to their default values.
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TLS_method(), TLS_server_method(), TLS_client_method(), DTLS_method(),
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DTLS_server_method() and DTLS_client_method() are the I<version-flexible>
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methods.
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All other methods only support one specific protocol version.
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Use the I<version-flexible> methods instead of the version specific methods.
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If you want to limit the supported protocols for the version flexible
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methods you can use L<SSL_CTX_set_min_proto_version(3)>,
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L<SSL_set_min_proto_version(3)>, L<SSL_CTX_set_max_proto_version(3)> and
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L<SSL_set_max_proto_version(3)> functions.
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Using these functions it is possible to choose e.g. TLS_server_method()
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and be able to negotiate with all possible clients, but to only
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allow newer protocols like TLS 1.0, TLS 1.1, TLS 1.2 or TLS 1.3.
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The list of protocols available can also be limited using the
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B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>, B<SSL_OP_NO_TLSv1_1>,
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B<SSL_OP_NO_TLSv1_3>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
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options of the
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L<SSL_CTX_set_options(3)> or L<SSL_set_options(3)> functions, but this approach
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is not recommended. Clients should avoid creating "holes" in the set of
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protocols they support. When disabling a protocol, make sure that you also
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disable either all previous or all subsequent protocol versions.
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In clients, when a protocol version is disabled without disabling I<all>
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previous protocol versions, the effect is to also disable all subsequent
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protocol versions.
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The SSLv3 protocol is deprecated and should generally not be used.
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Applications should typically use L<SSL_CTX_set_min_proto_version(3)> to set
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the minimum protocol to at least B<TLS1_VERSION>.
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=head1 RETURN VALUES
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The following return values can occur:
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=over 4
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=item NULL
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The creation of a new SSL_CTX object failed. Check the error stack to find out
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the reason.
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=item Pointer to an SSL_CTX object
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The return value points to an allocated SSL_CTX object.
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SSL_CTX_up_ref() returns 1 for success and 0 for failure.
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=back
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=head1 SEE ALSO
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L<SSL_CTX_set_options(3)>, L<SSL_CTX_free(3)>,
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SSL_CTX_set_verify(3), L<SSL_CTX_set1_param(3)>, L<SSL_CTX_get0_param(3)>,
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L<SSL_connect(3)>, L<SSL_accept(3)>,
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L<SSL_CTX_set_min_proto_version(3)>, L<ssl(7)>, L<SSL_set_connect_state(3)>
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=head1 HISTORY
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Support for SSLv2 and the corresponding SSLv2_method(),
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SSLv2_server_method() and SSLv2_client_method() functions where
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removed in OpenSSL 1.1.0.
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SSLv23_method(), SSLv23_server_method() and SSLv23_client_method()
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were deprecated and the preferred TLS_method(), TLS_server_method()
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and TLS_client_method() functions were added in OpenSSL 1.1.0.
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All version-specific methods were deprecated in OpenSSL 1.1.0.
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SSL_CTX_new_ex() was added in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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