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.\" $OpenBSD: SSL_do_handshake.3,v 1.6 2018/03/27 17:35:50 schwarze Exp $
.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Martin Sjoegren <martin@strakt.com>.
.\" Copyright (c) 2002 The OpenSSL Project. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\"
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in
.\" the documentation and/or other materials provided with the
.\" distribution.
.\"
.\" 3. All advertising materials mentioning features or use of this
.\" software must display the following acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\" endorse or promote products derived from this software without
.\" prior written permission. For written permission, please contact
.\" openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\" nor may "OpenSSL" appear in their names without prior written
.\" permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\" acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: March 27 2018 $
.Dt SSL_DO_HANDSHAKE 3
.Os
.Sh NAME
.Nm SSL_do_handshake
.Nd perform a TLS/SSL handshake
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft int
.Fn SSL_do_handshake "SSL *ssl"
.Sh DESCRIPTION
.Fn SSL_do_handshake
will wait for a SSL/TLS handshake to take place.
If the connection is in client mode, the handshake will be started.
The handshake routines may have to be explicitly set in advance using either
.Xr SSL_set_connect_state 3
or
.Xr SSL_set_accept_state 3 .
.Pp
The behaviour of
.Fn SSL_do_handshake
depends on the underlying
.Vt BIO .
.Pp
If the underlying
.Vt BIO
is
.Em blocking ,
.Fn SSL_do_handshake
will only return once the handshake has been finished or an error occurred.
.Pp
If the underlying
.Vt BIO
is
.Em non-blocking ,
.Fn SSL_do_handshake
will also return when the underlying
.Vt BIO
could not satisfy the needs of
.Fn SSL_do_handshake
to continue the handshake.
In this case a call to
.Xr SSL_get_error 3
with the return value of
.Fn SSL_do_handshake
will yield
.Dv SSL_ERROR_WANT_READ
or
.Dv SSL_ERROR_WANT_WRITE .
The calling process then must repeat the call after taking appropriate action
to satisfy the needs of
.Fn SSL_do_handshake .
The action depends on the underlying
.Vt BIO .
When using a non-blocking socket, nothing is to be done, but
.Xr select 2
can be used to check for the required condition.
When using a buffering
.Vt BIO ,
like a
.Vt BIO
pair, data must be written into or retrieved out of the
.Vt BIO
before being able to continue.
.Sh RETURN VALUES
The following return values can occur:
.Bl -tag -width Ds
.It 0
The TLS/SSL handshake was not successful but was shut down controlled and
by the specifications of the TLS/SSL protocol.
Call
.Xr SSL_get_error 3
with the return value
.Fa ret
to find out the reason.
.It 1
The TLS/SSL handshake was successfully completed,
and a TLS/SSL connection has been established.
.It <0
The TLS/SSL handshake was not successful because either a fatal error occurred
at the protocol level or a connection failure occurred.
The shutdown was not clean.
It can also occur if action is needed to continue the operation for
non-blocking
.Vt BIO Ns s .
Call
.Xr SSL_get_error 3
with the return value
.Fa ret
to find out the reason.
.El
.Sh SEE ALSO
.Xr BIO_new 3 ,
.Xr ssl 3 ,
.Xr SSL_accept 3 ,
.Xr SSL_connect 3 ,
.Xr SSL_get_error 3 ,
.Xr SSL_set_connect_state 3
.Sh HISTORY
.Fn SSL_do_handshake
first appeared in SSLeay 0.8.0 and has been available since
.Ox 2.4 .
|
