Fix using to_link buffer after freed

Fix using to_link buffer after freed

When I refactored the tls_state_change method in
9a7b95fda5 I accidentally changed a break into
a return true while it should return a false.

The code here is extremely fragile in the sense
that it assumes that settings a keystate to S_ERROR
cannot have any outgoing buffer or we will have a
use after free.  The previous break and now restored
return false ensure this by skipping any further
tls_process_state loops that might set to ks->S_ERROR
and ensure that the to_link is sent out and cleared
before having more loops in tls_state_change.

CVE: 2023-46850

This affects everyone, even with tls-auth/tls-crypt enabled.

Change-Id: I2a0f1c665d992da8e24a421ff0ddcb40f7945ea8
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: David Sommerseth <davids@openvpn.net>
Acked-by: Heiko Hund <heiko@ist.eigentlich.net>
Message-Id: <20231108124947.76816-3-gert@greenie.muc.de>
URL: https://www.mail-archive.com/search?l=mid&q=20231108124947.76816-3-gert@greenie.muc.de
Signed-off-by: Gert Doering <gert@greenie.muc.de>