82 lines
2.5 KiB
Plaintext
82 lines
2.5 KiB
Plaintext
=pod
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=head1 NAME
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SSL_do_handshake - perform a TLS/SSL handshake
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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int SSL_do_handshake(SSL *ssl);
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=head1 DESCRIPTION
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SSL_do_handshake() will wait for a SSL/TLS handshake to take place. If the
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connection is in client mode, the handshake will be started. The handshake
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routines may have to be explicitly set in advance using either
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L<SSL_set_connect_state(3)> or
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L<SSL_set_accept_state(3)>.
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=head1 NOTES
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The behaviour of SSL_do_handshake() depends on the underlying BIO.
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If the underlying BIO is B<blocking>, SSL_do_handshake() will only return
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once the handshake has been finished or an error occurred.
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If the underlying BIO is B<nonblocking>, SSL_do_handshake() will also return
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when the underlying BIO could not satisfy the needs of SSL_do_handshake()
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to continue the handshake. In this case a call to SSL_get_error() with the
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return value of SSL_do_handshake() will yield B<SSL_ERROR_WANT_READ> or
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B<SSL_ERROR_WANT_WRITE>. The calling process then must repeat the call after
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taking appropriate action to satisfy the needs of SSL_do_handshake().
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The action depends on the underlying BIO. When using a nonblocking socket,
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nothing is to be done, but select() can be used to check for the required
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condition. When using a buffering BIO, like a BIO pair, data must be written
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into or retrieved out of the BIO before being able to continue.
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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 Z<>0
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The TLS/SSL handshake was not successful but was shut down controlled and
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by the specifications of the TLS/SSL protocol. Call SSL_get_error() with the
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return value B<ret> to find out the reason.
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=item Z<>1
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The TLS/SSL handshake was successfully completed, a TLS/SSL connection has been
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established.
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=item E<lt>0
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The TLS/SSL handshake was not successful because a fatal error occurred either
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at the protocol level or a connection failure occurred. The shutdown was
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not clean. It can also occur if action is needed to continue the operation
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for nonblocking BIOs. Call SSL_get_error() with the return value B<ret>
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to find out the reason.
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=back
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=head1 SEE ALSO
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L<SSL_get_error(3)>, L<SSL_connect(3)>,
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L<SSL_accept(3)>, L<ssl(7)>, L<bio(7)>,
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L<SSL_set_connect_state(3)>
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=head1 COPYRIGHT
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Copyright 2002-2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (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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