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95 lines
3.2 KiB
Plaintext
95 lines
3.2 KiB
Plaintext
=pod
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=head1 NAME
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SSL_CTX_new - create a new SSL_CTX object as framework for TLS/SSL enabled 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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=head1 DESCRIPTION
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SSL_CTX_new() creates a new B<SSL_CTX> object as framework to establish
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TLS/SSL enabled connections.
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=head1 NOTES
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The SSL_CTX object uses B<method> as connection method. The methods exist
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in a generic type (for client and server use), a server only type, and a
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client only type. B<method> can be of the following types:
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=over 4
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=item SSLv2_method(void), SSLv2_server_method(void), SSLv2_client_method(void)
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A TLS/SSL connection established with these methods will only understand
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the SSLv2 protocol. A client will send out SSLv2 client hello messages
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and will also indicate that it only understand SSLv2. A server will only
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understand SSLv2 client hello messages.
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=item SSLv3_method(void), SSLv3_server_method(void), SSLv3_client_method(void)
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A TLS/SSL connection established with these methods will only understand the
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SSLv3 protocol. A client will send out SSLv3 client hello messages
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and will indicate that it only understands SSLv3. A server will only understand
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SSLv3 client hello messages. This especially means, that it will
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not understand SSLv2 client hello messages which are widely used for
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compatibility reasons, see SSLv23_*_method().
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=item TLSv1_method(void), TLSv1_server_method(void), TLSv1_client_method(void)
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A TLS/SSL connection established with these methods will only understand the
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TLSv1 protocol. A client will send out TLSv1 client hello messages
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and will indicate that it only understands TLSv1. A server will only understand
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TLSv1 client hello messages. This especially means, that it will
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not understand SSLv2 client hello messages which are widely used for
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compatibility reasons, see SSLv23_*_method(). It will also not understand
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SSLv3 client hello messages.
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=item SSLv23_method(void), SSLv23_server_method(void), SSLv23_client_method(void)
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A TLS/SSL connection established with these methods will understand the SSLv2,
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SSLv3, and TLSv1 protocol. A client will send out SSLv2 client hello messages
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and will indicate that it also understands SSLv3 and TLSv1. A server will
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understand SSLv2, SSLv3, and TLSv1 client hello messages. This is the best
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choice when compatibility is a concern.
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=back
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The list of protocols available can later be limited using the SSL_OP_NO_SSLv2,
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SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1 options of the B<SSL_CTX_set_options()> or
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B<SSL_set_options()> functions. Using these options it is possible to choose
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e.g. SSLv23_server_method() and be able to negotiate with all possible
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clients, but to only allow newer protocols like SSLv3 or TLSv1.
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SSL_CTX_new() initializes the list of ciphers, the session cache setting,
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the callbacks, the keys and certificates, and the options to its default
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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 SEE ALSO
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L<SSL_CTX_free(3)|SSL_CTX_free(3)>, L<SSL_accept(3)|SSL_accept(3)>,
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L<ssl(3)|ssl(3)>, L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>
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=cut
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