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a9af1da0b5
Add a 16-bit token index into the anti-clogging token. This can be used to enforce only a single use of each issued anti-clogging token request. The token value is now token-index | last-30-octets-of(HMAC-SHA256(sae_token_key, STA-MAC-address | token-index)), i.e., the first two octets of the SHA256 hash value are replaced with the token-index and token-index itself is protected as part of the HMAC context data. Track the used 16-bit token index values and accept received tokens only if they use an index value that has been requested, but has not yet been used. This makes it a bit more difficult for an attacker to perform DoS attacks against the heavy CPU operations needed for processing SAE commit since the attacker cannot simply replay the same frame multiple times and instead, needs to request each token separately. While this does not add significant extra processing/CPU need for the attacker, this can be helpful in combination with the queued processing of SAE commit messages in enforcing more delay during flooding of SAE commit messages since the new anti-clogging token values are not returned before the new message goes through the processing queue. Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
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