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Title "SSL_key_update 3"
way too many mistakes in technical documents.
.nh
\fBSSL_key_update() must only be called after the initial handshake has been completed and TLSv1.3 has been negotiated. The key update will not take place until the next time an \s-1IO\s0 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.
\fBSSL_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 \s-1SSL_KEY_UPDATE_NONE\s0 otherwise.
\fBSSL_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 \s-1SSL/TLS\s0 connection. The next time an \s-1IO\s0 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 \fBSSL_renegotiate_abbreviated() behave identically. They both schedule a request for a new handshake to be sent to the client. The next time an \s-1IO\s0 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 \s-1IO\s0 function.
If an OpenSSL client receives a renegotiation request from a server then again this will be handled transparently through calling any OpenSSL \s-1IO\s0 function. For a \s-1TLS\s0 connection the client will attempt to resume the current session in the new handshake. For historical reasons, \s-1DTLS\s0 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.
\fBSSL_get_key_update_type() returns the update type of the pending key update operation or \s-1SSL_KEY_UPDATE_NONE\s0 if there is none.
\fBSSL_renegotiate_pending() returns 1 if a renegotiation or renegotiation request has been scheduled but not yet acted on, or 0 otherwise.
Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.
Indexes created Wed Apr 29 00:23:26 UTC 2026