Downlink replay protection rework - #335
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As reported in #314, the downlink replay protection can be disarmed by pushing an invalid downlink session, as the SESSION_VALID flag gets cleared at the start of each session, which disables the `is_valid_downlink` check. The fix #314 only addresses the invalid sequence number decrement. This bug also disables replay protection for sessions that follow a session with only corrupted pouches, though which has to be addressed separately. We also reinitialize the session for every received pouch, which resets the session pouch ID, preventing the pouch ID replay check from working correctly. This patch addresses the core issue that causes the bug addressed in #314, and is intended to supersede #314. It additionally adds a check for the block size log parameter, and adds a `server.has_seqnum` flag that replaces the validation check for `server.seqnum` the `SESSION_VALID` flag previously covered. Note: As replay protection is not implemented on the server side, the session replay protection defect does not affect any active deployments, but all the while this code exists in this repo, it needs to be correct. Signed-off-by: Trond Snekvik <trond.snekvik@canonical.com>
Adds a downlink_session test that runs through the rules in the downlink session creation and validation. Signed-off-by: Trond Snekvik <trond.snekvik@canonical.com>
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As reported in #314, the downlink replay protection can be disarmed by
pushing an invalid downlink session, as the SESSION_VALID flag gets cleared
at the start of each session, which disables the
is_valid_downlinkcheck.The fix #314 only addresses the invalid sequence number decrement. This bug
also disables replay protection for sessions that follow a session with
only corrupted pouches, though which has to be addressed separately. We
also reinitialize the session for every received pouch, which resets the
session pouch ID, preventing the pouch ID replay check from working
correctly.
This patch addresses the core issue that causes the bug addressed in #314,
and is intended to supersede #314. It additionally adds a check for the
block size log parameter, and adds a
server.has_seqnumflag that replacesthe validation check for
server.seqnumtheSESSION_VALIDflagpreviously covered.
Note
As replay protection is not implemented on the server side, the
session replay protection defect does not affect any active deployments,
but all the while this code exists in this repo, it needs to be correct.
Adds a quick test that verifies the ruleset.