Edit
IABSD.fr/src/lib/libssl/man/SSL_write.3
schwarze
- lib/libssl/man/SSL_write.3
-
.\" $OpenBSD: SSL_write.3,v 1.5 2018/03/27 17:35:50 schwarze Exp $ .\" OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400 .\" .\" This file was written by Lutz Jaenicke <jaenicke@openssl.org>. .\" Copyright (c) 2000, 2001, 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_WRITE 3 .Os .Sh NAME .Nm SSL_write .Nd write bytes to a TLS/SSL connection .Sh SYNOPSIS .In openssl/ssl.h .Ft int .Fn SSL_write "SSL *ssl" "const void *buf" "int num" .Sh DESCRIPTION .Fn SSL_write writes .Fa num bytes from the buffer .Fa buf into the specified .Fa ssl connection. .Pp If necessary, .Fn SSL_write will negotiate a TLS/SSL session, if not already explicitly performed by .Xr SSL_connect 3 or .Xr SSL_accept 3 . If the peer requests a re-negotiation, it will be performed transparently during the .Fn SSL_write operation. The behaviour of .Fn SSL_write depends on the underlying .Vt BIO . .Pp For the transparent negotiation to succeed, the .Fa ssl must have been initialized to client or server mode. This is being done by calling .Xr SSL_set_connect_state 3 or .Xr SSL_set_accept_state 3 before the first call to an .Xr SSL_read 3 or .Fn SSL_write function. .Pp If the underlying .Vt BIO is .Em blocking , .Fn SSL_write will only return once the write operation has been finished or an error occurred, except when a renegotiation take place, in which case a .Dv SSL_ERROR_WANT_READ may occur. This behaviour can be controlled with the .Dv SSL_MODE_AUTO_RETRY flag of the .Xr SSL_CTX_set_mode 3 call. .Pp If the underlying .Vt BIO is .Em non-blocking , .Fn SSL_write will also return when the underlying .Vt BIO could not satisfy the needs of .Fn SSL_write to continue the operation. In this case a call to .Xr SSL_get_error 3 with the return value of .Fn SSL_write will yield .Dv SSL_ERROR_WANT_READ or .Dv SSL_ERROR_WANT_WRITE . As at any time a re-negotiation is possible, a call to .Fn SSL_write can also cause read operations! The calling process then must repeat the call after taking appropriate action to satisfy the needs of .Fn SSL_write . 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 BIO before being able to continue. .Pp .Fn SSL_write will only return with success when the complete contents of .Fa buf of length .Fa num have been written. This default behaviour can be changed with the .Dv SSL_MODE_ENABLE_PARTIAL_WRITE option of .Xr SSL_CTX_set_mode 3 . When this flag is set, .Fn SSL_write will also return with success when a partial write has been successfully completed. In this case the .Fn SSL_write operation is considered completed. The bytes are sent and a new .Fn SSL_write operation with a new buffer (with the already sent bytes removed) must be started. A partial write is performed with the size of a message block, which is 16kB. .Pp When an .Fn SSL_write operation has to be repeated because .Xr SSL_get_error 3 returned .Dv SSL_ERROR_WANT_READ or .Dv SSL_ERROR_WANT_WRITE , it must be repeated with the same arguments. .Pp When calling .Fn SSL_write with .Fa num Ns =0 bytes to be sent, the behaviour is undefined. .Sh RETURN VALUES The following return values can occur: .Bl -tag -width Ds .It >0 The write operation was successful. The return value is the number of bytes actually written to the TLS/SSL connection. .It 0 The write operation was not successful. Probably the underlying connection was closed. Call .Xr SSL_get_error 3 with the return value to find out whether an error occurred or the connection was shut down cleanly .Pq Dv SSL_ERROR_ZERO_RETURN . .It <0 The write operation was not successful, because either an error occurred or action must be taken by the calling process. Call .Xr SSL_get_error 3 with the return value 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_CTX_new 3 , .Xr SSL_CTX_set_mode 3 , .Xr SSL_get_error 3 , .Xr SSL_read 3 , .Xr SSL_set_connect_state 3 .Sh HISTORY .Fn SSL_write appeared in SSLeay 0.4 or earlier and has been available since .Ox 2.4 .