Updated: 2022/Sep/29

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SSL_key_update(3)                   OpenSSL                  SSL_key_update(3)



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

LIBRARY
       libcrypto, -lcrypto

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.

       When called from the server side, SSL_renegotiate() and
       SSL_renegotiate_abbreviated() behave identically. They both schedule a
       request for a new handshake to be sent to the client. The next time an
       IO operation is performed then 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
       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>.



3.0.12                            2023-05-07                 SSL_key_update(3)