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Some APs may send RSC octets in EAPOL-Key message 3 of 4-Way Handshake or in EAPOL-Key message 1 of Group Key Handshake in the opposite byte order (or by some other corrupted way). Thus, after a successful EAPOL-Key exchange the TSC values of received multicast packets, such as DHCP, don't match the RSC one and as a result these packets are dropped on replay attack TSC verification. An example of such AP is Sapido RB-1732. Work around this by setting RSC octets to 0 on GTK installation if the AP RSC value is identified as a potentially having the byte order issue. This may open a short window during which older (but valid) group-addressed frames could be replayed. However, the local receive counter will be updated on the first received group-addressed frame and the workaround is enabled only if the common invalid cases are detected, so this workaround is acceptable as not decreasing security significantly. The wpa_rsc_relaxation global configuration property allows the GTK RSC workaround to be disabled if it's not needed. Signed-off-by: Max Stepanov <Max.Stepanov@intel.com>
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