1.\" $OpenBSD: SSL_accept.3,v 1.6 2019/06/08 15:25:43 schwarze Exp $ 2.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100 3.\" 4.\" This file was written by Lutz Jaenicke <jaenicke@openssl.org>. 5.\" Copyright (c) 2000, 2001, 2002, 2003 The OpenSSL Project. 6.\" All rights reserved. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in 17.\" the documentation and/or other materials provided with the 18.\" distribution. 19.\" 20.\" 3. All advertising materials mentioning features or use of this 21.\" software must display the following acknowledgment: 22.\" "This product includes software developed by the OpenSSL Project 23.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 24.\" 25.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 26.\" endorse or promote products derived from this software without 27.\" prior written permission. For written permission, please contact 28.\" openssl-core@openssl.org. 29.\" 30.\" 5. Products derived from this software may not be called "OpenSSL" 31.\" nor may "OpenSSL" appear in their names without prior written 32.\" permission of the OpenSSL Project. 33.\" 34.\" 6. Redistributions of any form whatsoever must retain the following 35.\" acknowledgment: 36.\" "This product includes software developed by the OpenSSL Project 37.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 38.\" 39.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 40.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 41.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 42.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 43.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 44.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 45.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 46.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 47.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 48.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 49.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 50.\" OF THE POSSIBILITY OF SUCH DAMAGE. 51.\" 52.Dd $Mdocdate: June 8 2019 $ 53.Dt SSL_ACCEPT 3 54.Os 55.Sh NAME 56.Nm SSL_accept 57.Nd wait for a TLS/SSL client to initiate a TLS/SSL handshake 58.Sh SYNOPSIS 59.In openssl/ssl.h 60.Ft int 61.Fn SSL_accept "SSL *ssl" 62.Sh DESCRIPTION 63.Fn SSL_accept 64waits for a TLS/SSL client to initiate the TLS/SSL handshake. 65The communication channel must already have been set and assigned to the 66.Fa ssl 67object by setting an underlying 68.Vt BIO . 69.Pp 70The behaviour of 71.Fn SSL_accept 72depends on the underlying 73.Vt BIO . 74.Pp 75If the underlying 76.Vt BIO 77is 78.Em blocking , 79.Fn SSL_accept 80will only return once the handshake has been finished or an error occurred. 81.Pp 82If the underlying 83.Vt BIO 84is 85.Em non-blocking , 86.Fn SSL_accept 87will also return when the underlying 88.Vt BIO 89could not satisfy the needs of 90.Fn SSL_accept 91to continue the handshake, indicating the problem by the return value \(mi1. 92In this case a call to 93.Xr SSL_get_error 3 94with the 95return value of 96.Fn SSL_accept 97will yield 98.Dv SSL_ERROR_WANT_READ 99or 100.Dv SSL_ERROR_WANT_WRITE . 101The calling process then must repeat the call after taking appropriate action 102to satisfy the needs of 103.Fn SSL_accept . 104The action depends on the underlying 105.Dv BIO . 106When using a non-blocking socket, nothing is to be done, but 107.Xr select 2 108can be used to check for the required condition. 109When using a buffering 110.Vt BIO , 111like a 112.Vt BIO 113pair, data must be written into or retrieved out of the 114.Vt BIO 115before being able to continue. 116.Sh RETURN VALUES 117The following return values can occur: 118.Bl -tag -width Ds 119.It 0 120The TLS/SSL handshake was not successful but was shut down controlled and by 121the specifications of the TLS/SSL protocol. 122Call 123.Xr SSL_get_error 3 124with the return value 125.Fa ret 126to find out the reason. 127.It 1 128The TLS/SSL handshake was successfully completed, 129and a TLS/SSL connection has been established. 130.It <0 131The TLS/SSL handshake was not successful because a fatal error occurred either 132at the protocol level or a connection failure occurred. 133The shutdown was not clean. 134It can also occur of action is need to continue the operation for non-blocking 135.Vt BIO Ns 136s. 137Call 138.Xr SSL_get_error 3 139with the return value 140.Fa ret 141to find out the reason. 142.El 143.Sh SEE ALSO 144.Xr BIO_new 3 , 145.Xr ssl 3 , 146.Xr SSL_connect 3 , 147.Xr SSL_CTX_new 3 , 148.Xr SSL_do_handshake 3 , 149.Xr SSL_get_error 3 , 150.Xr SSL_set_connect_state 3 , 151.Xr SSL_shutdown 3 152.Sh HISTORY 153.Fn SSL_accept 154appeared in SSLeay 0.4 or earlier and has been available since 155.Ox 2.4 . 156