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https://github.com/openssl/openssl.git
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a18a31e49d
The SSL and SSL_CTX structures are reference counted. However since libssl was made opaque there is no way for users of the library to manipulate the reference counts. This adds functions to enable that. Reviewed-by: Stephen Henson <steve@openssl.org>
193 lines
6.5 KiB
Plaintext
193 lines
6.5 KiB
Plaintext
=pod
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=head1 NAME
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SSL_CTX_new, SSL_CTX_up_ref, SSLv3_method, SSLv3_server_method,
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SSLv3_client_method, TLSv1_method, TLSv1_server_method, TLSv1_client_method,
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TLSv1_1_method, TLSv1_1_server_method, TLSv1_1_client_method, TLS_method,
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TLS_server_method, TLS_client_method, SSLv23_method, SSLv23_server_method,
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SSLv23_client_method, DTLS_method, DTLS_server_method, DTLS_client_method,
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DTLSv1_method, DTLSv1_server_method, DTLSv1_client_method,
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DTLSv1_2_method, DTLSv1_2_server_method, 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(const SSL_METHOD *method);
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void 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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#define SSLv23_method TLS_method
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#define SSLv23_server_method TLS_server_method
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#define SSLv23_client_method TLS_client_method
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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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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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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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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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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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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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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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=head1 DESCRIPTION
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SSL_CTX_new() creates a new B<SSL_CTX> object as framework to
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establish TLS/SSL or DTLS enabled connections. An B<SSL_CTX> object is
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reference counted. Creating an B<SSL_CTX> object for the first time increments
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the reference count. Freeing it (using SSL_CTX_free) decrements it. When the
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reference count drops to zero, any memory or resources allocated to the
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B<SSL_CTX> object are freed. SSL_CTX_up_ref() increments the reference count for
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an existing B<SSL_CTX> structure.
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=head1 NOTES
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The SSL_CTX object uses B<method> as connection method.
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The methods exist in a generic type (for client and server use), a server only
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type, and a client only type.
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B<method> can be of the following types:
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=over 4
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=item SSLv3_method(), SSLv3_server_method(), SSLv3_client_method()
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An SSL connection established with these methods will only understand
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the SSLv3 protocol.
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A client will send out a SSLv3 client hello messages and will
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indicate that it supports SSLv3.
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A server will only understand SSLv3 client hello message and only
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support the SSLv3 protocol.
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=item TLSv1_method(), TLSv1_server_method(), TLSv1_client_method()
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A TLS connection established with these methods will only understand
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the TLS 1.0 protocol.
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=item TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method()
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A TLS connection established with these methods will only understand
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the TLS 1.1 protocol.
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=item TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method()
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A TLS connection established with these methods will only understand
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the TLS 1.2 protocol.
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=item TLS_method(), TLS_server_method(), TLS_client_method()
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A TLS/SSL connection established with these methods may understand
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the SSLv3, TLSv1, TLSv1.1 and TLSv1.2 protocols.
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If extensions are required (for example server name)
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a client will send out TLSv1 client hello messages including extensions and
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will indicate that it also understands TLSv1.1, TLSv1.2 and permits a
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fallback to SSLv3. A server will support SSLv3, TLSv1, TLSv1.1 and TLSv1.2
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protocols. This is the best choice when compatibility is a concern.
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=item SSLv23_method(), SSLv23_server_method(), SSLv23_client_method()
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Use of these functions is deprecated. They have been replaced with TLS_method(),
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TLS_server_method() and TLS_client_method() respectively. New code should use
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those functions instead.
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=item DTLS_method(), DTLS_server_method(), DTLS_client_method()
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A DTLS connection established with those methods understands all
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supported DTLS protocols.
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Currently supported protocols are DTLS 1.0 and DTLS 1.2.
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=item DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method()
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A DTLS connection established with these methods will only understand
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the DTLS 1.0 protocol.
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=item DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method()
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A DTLS connection established with these methods will only understand
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the DTLS 1.2 protocol.
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=back
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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 version
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flexible methods.
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All other methods only support one specific protocol version.
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Use these methods instead of the other 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 SSL_CTX_set_min_proto_version(),
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SSL_set_min_proto_version(), SSL_CTX_set_max_proto_version() and
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SSL_set_max_proto_version() functions.
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They can also be limited by setting an option like B<SSL_OP_NO_SSLv3>
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via the L<SSL_CTX_set_options(3)> or L<SSL_set_options(3)> functions,
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but that's not recommended.
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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 or TLS 1.2.
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SSL_CTX_new() initializes the list of ciphers, the session cache
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setting, the callbacks, the keys and certificates and the options
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to its default values.
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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
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find out 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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=back
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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 introduced in OpenSSL 1.1.0.
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=head1 SEE ALSO
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L<SSL_CTX_free(3)>, L<SSL_accept(3)>,
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L<SSL_CTX_set_min_proto_version(3)>,
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L<ssl(3)>, L<SSL_set_connect_state(3)>
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=cut
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