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cyrusimap / cyrus-sasl

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SCRAM: Client does not check low iteration counter #811 #813

Closed GuidoKiener closed 9 months ago

GuidoKiener commented 9 months ago

Using mechanism SCRAM, a client does not abort authentication when the given iteration counter is lower than 4096.

A hostile server can send a small iteration counter (e.g. 1) and forces the client to send a ClientProof that is calculated with lowest computation time. Thus the hostile server can recover the client's password faster with an offline dictionary or brute-force attack.

This fix compares the iteration counter with the recommended minimum of 4096 and aborts the authentication if the server violates the recommended minimum.

mistotebe commented 9 months ago

PRs should be targeting master, please adjust.

GuidoKiener commented 9 months ago

PRs should be targeting master, please adjust.

Thanks. It's now reopened in #815.