Added a new configuration option, wpa_ptk_rekey, that can be used to
enforce frequent PTK rekeying, e.g., to mitigate some attacks against TKIP
deficiencies. This can be set either by the Authenticator (to initiate
periodic 4-way handshake to rekey PTK) or by the Supplicant (to request
Authenticator to rekey PTK).
With both wpa_ptk_rekey and wpa_group_rekey (in hostapd) set to 600, TKIP
keys will not be used for more than 10 minutes which may make some attacks
against TKIP more difficult to implement.
This avoids getting stuck in state where wpa_supplicant has canceled scans,
but the driver is actually in disassociated state. The previously used code
that controlled scan timeout from WPA module is not really needed anymore
(and has not been needed for past four years since authentication timeout
was separated from scan request timeout), so this can simply be removed to
resolved the race condition. As an extra bonus, this simplifies the
interface to WPA module.
[Bug 261]
