.\" $OpenBSD: SSL_renegotiate.3,v 1.8 2018/03/27 17:35:50 schwarze Exp $ .\" OpenSSL SSL_key_update.pod 4fbfe86a Feb 16 17:04:40 2017 +0000 .\" .\" This file is a derived work. .\" Some parts are covered by the following Copyright and license: .\" .\" Copyright (c) 2016, 2017 Ingo Schwarze .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" .\" Other parts were written by Matt Caswell . .\" Copyright (c) 2017 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_RENEGOTIATE 3 .Os .Sh NAME .Nm SSL_renegotiate , .Nm SSL_renegotiate_abbreviated , .Nm SSL_renegotiate_pending .Nd initiate a new TLS handshake .Sh SYNOPSIS .In openssl/ssl.h .Ft int .Fo SSL_renegotiate .Fa "SSL *ssl" .Fc .Ft int .Fo SSL_renegotiate_abbreviated .Fa "SSL *ssl" .Fc .Ft int .Fo SSL_renegotiate_pending .Fa "SSL *ssl" .Fc .Sh DESCRIPTION When called from the client side, .Fn SSL_renegotiate schedules a completely new handshake over an existing TLS connection. The next time an I/O operation such as .Fn SSL_read or .Fn SSL_write takes place on the connection, a check is performed to confirm that it is a suitable time to start a renegotiation. If so, a new handshake is initiated immediately. An existing session associated with the connection is not resumed. .Pp This function is automatically called by .Xr SSL_read 3 and .Xr SSL_write 3 whenever the renegotiation byte count set by .Xr BIO_set_ssl_renegotiate_bytes 3 or the timeout set by .Xr BIO_set_ssl_renegotiate_timeout 3 are exceeded. .Pp When called from the client side, .Fn SSL_renegotiate_abbreviated is similar to .Fn SSL_renegotiate except that resuming the session associated with the current connection is attempted in the new handshake. .Pp When called from the server side, .Fn SSL_renegotiate and .Fn SSL_renegotiate_abbreviated behave identically. They both schedule a request for a new handshake to be sent to the client. The next time an I/O operation is performed, the same checks as on the client side are performed and then, if appropriate, the request is sent. The client may or may not respond with a new handshake and it may or may not attempt to resume an existing session. If a new handshake is started, it is handled transparently during any I/O function. .Pp If a LibreSSL client receives a renegotiation request from a server, it is also handled transparently during any I/O function. The client attempts to resume the current session in the new handshake. For historical reasons, DTLS clients do not attempt to resume the session in the new handshake. .Sh RETURN VALUES .Fn SSL_renegotiate and .Fn SSL_renegotiate_abbreviated return 1 on success or 0 on error. .Pp .Fn SSL_renegotiate_pending returns 1 if a renegotiation or renegotiation request has been scheduled but not yet acted on, or 0 otherwise. .Sh SEE ALSO .Xr SSL_do_handshake 3 , .Xr SSL_num_renegotiations 3 , .Xr SSL_read 3 , .Xr SSL_write 3 .Sh HISTORY .Fn SSL_renegotiate first appeared in SSLeay 0.8.0 and has been available since .Ox 2.4 . .Pp .Fn SSL_renegotiate_pending first appeared in OpenSSL 0.9.7 and has been available since .Ox 3.2 . .Pp .Fn SSL_renegotiate_abbreviated first appeared in OpenSSL 1.0.1 and has been available since .Ox 5.3 .