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SSL_KEY_UPDATE(3ossl) OpenSSL SSL_KEY_UPDATE(3ossl)
NAME
SSL_key_update, SSL_get_key_update_type, SSL_renegotiate,
SSL_renegotiate_abbreviated, SSL_renegotiate_pending - initiate and
obtain information about updating connection keys
SYNOPSIS
#include <openssl/ssl.h>
int SSL_key_update(SSL *s, int updatetype);
int SSL_get_key_update_type(const SSL *s);
int SSL_renegotiate(SSL *s);
int SSL_renegotiate_abbreviated(SSL *s);
int SSL_renegotiate_pending(const SSL *s);
DESCRIPTION
SSL_key_update() schedules an update of the keys for the current TLS
connection. If the updatetype parameter is set to
SSL_KEY_UPDATE_NOT_REQUESTED then the sending keys for this connection
will be updated and the peer will be informed of the change. If the
updatetype parameter is set to SSL_KEY_UPDATE_REQUESTED then the
sending keys for this connection will be updated and the peer will be
informed of the change along with a request for the peer to
additionally update its sending keys. It is an error if updatetype is
set to SSL_KEY_UPDATE_NONE.
SSL_key_update() must only be called after the initial handshake has
been completed and TLSv1.3 has been negotiated, at the same time, the
application needs to ensure that the writing of data has been
completed. The key update will not take place until the next time an IO
operation such as SSL_read_ex() or SSL_write_ex() takes place on the
connection. Alternatively SSL_do_handshake() can be called to force the
update to take place immediately.
SSL_get_key_update_type() can be used to determine whether a key update
operation has been scheduled but not yet performed. The type of the
pending key update operation will be returned if there is one, or
SSL_KEY_UPDATE_NONE otherwise.
SSL_renegotiate() and SSL_renegotiate_abbreviated() should only be
called for connections that have negotiated TLSv1.2 or less. Calling
them on any other connection will result in an error.
When called from the client side, SSL_renegotiate() schedules a
completely new handshake over an existing SSL/TLS connection. The next
time an IO operation such as SSL_read_ex() or SSL_write_ex() takes
place on the connection a check will be performed to confirm that it is
a suitable time to start a renegotiation. If so, then it will be
initiated immediately. OpenSSL will not attempt to resume any session
associated with the connection in the new handshake.
When called from the client side, SSL_renegotiate_abbreviated() works
in the same was as SSL_renegotiate() except that OpenSSL will attempt
to resume the session associated with the current connection in the new
handshake.
then this will be handled transparently by calling any OpenSSL IO
function.
If an OpenSSL client receives a renegotiation request from a server
then again this will be handled transparently through calling any
OpenSSL IO function. For a TLS connection the client will attempt to
resume the current session in the new handshake. For historical
reasons, DTLS clients will not attempt to resume the session in the new
handshake.
The SSL_renegotiate_pending() function returns 1 if a renegotiation or
renegotiation request has been scheduled but not yet acted on, or 0
otherwise.
RETURN VALUES
SSL_key_update(), SSL_renegotiate() and SSL_renegotiate_abbreviated()
return 1 on success or 0 on error.
SSL_get_key_update_type() returns the update type of the pending key
update operation or SSL_KEY_UPDATE_NONE if there is none.
SSL_renegotiate_pending() returns 1 if a renegotiation or renegotiation
request has been scheduled but not yet acted on, or 0 otherwise.
SEE ALSO
ssl(7), SSL_read_ex(3), SSL_write_ex(3), SSL_do_handshake(3)
HISTORY
The SSL_key_update() and SSL_get_key_update_type() functions were added
in OpenSSL 1.1.1.
COPYRIGHT
Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
3.0.11 2023-09-19 SSL_KEY_UPDATE(3ossl)