[PATCH v2 0/2] SME: Fall back from PMKSA caching on deauthentication

[Louis Kotze]

Some APs reject an association attempt that uses SAE PMKSA caching by
deauthenticating the STA instead of responding to the Association
Request frame with an error status code. wpa_supplicant keeps the PMKSA
cache entry on that path, so every following attempt retries PMKSA
caching and is deauthenticated again, and the connection never falls
back to a full SAE authentication. Observed with a TP-Link Deco BE65
AP MLD deauthenticating with reason code 9.

Patch 1 mirrors the PMKSA cache handling that sme_event_assoc_reject()
already does for the error-status-code case. Patch 2 adds hwsim
coverage.

The deauthentication acted on here is necessarily unprotected, since it
arrives while the STA is still in WPA_AUTHENTICATING or WPA_ASSOCIATING
and no PTK is in place. A forged frame can therefore make the STA
discard a valid PMKSA cache entry, which costs the fast-reconnect
optimization on the next attempt but does not change what is
negotiated; an attacker who can inject at that point can already
prevent the association outright.

Changes in v2:
- Rebased on current main. No functional change: patch 1 is unchanged
  and patch 2 only moves to the new end of tests/hwsim/test_sae.py
  after commit b57ee6cfc added a test there.
- Shortened patch 1's subject and noted in its commit message why the
  new handler does not repeat the reconnection that
  sme_event_assoc_reject() performs.

Louis Kotze (2):
  SME: Fall back from PMKSA caching if the AP deauthenticates
  tests: SAE PMKSA caching attempt rejected with deauthentication

 tests/hwsim/test_sae.py | 48 +++++++++++++++++++++++++++++++++++++++++
 wpa_supplicant/events.c |  3 +++
 wpa_supplicant/sme.c    | 33 ++++++++++++++++++++++++++++
 wpa_supplicant/sme.h    |  7 ++++++
 4 files changed, 91 insertions(+)


base-commit: dcfb7053840087a943873e9a034b69cd79abaac2
-- 
2.55.0