This part is missing from IEEE Std 802.11ai-2016, but the lack of DHss
here means there would not be proper PFS for the case where PMKSA
caching is used with FILS SK+PFS authentication. This was not really the
intent of the FILS design and that issue was fixed during REVmd work
with the changes proposed in
https://mentor.ieee.org/802.11/dcn/17/11-17-0906-04-000m-fils-fixes.docx
that add DHss into FILS-Key-Data (and PTK, in practice) derivation for
the PMKSA caching case so that a unique ICK, KEK, and TK are derived
even when using the same PMK.
Note: This is not backwards compatible, i.e., this breaks PMKSA caching
with FILS SK+PFS if only STA or AP side implementation is updated.
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
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