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riccardom
1182239faa
OnNewPSKReady could be applied out of order: two exchanges for a peer can derive concurrently (one over signal, one over the data path), and the callbacks run outside the manager lock, so an older exchange's apply could land after a newer one and restore a stale WireGuard PSK, splitting the tunnel. Give each exchange a per-peer monotonic generation, assigned under the lock at creation so a later exchange always carries a higher one, and pass it to OnNewPSKReady. The host adapter records the newest generation applied per peer and drops any callback that is not newer, with the check-and-record atomic so the slow SetPresharedKey call stays off that lock. Found in cubic review on #7098 (client/internal/pqkem/callbacks.go:12).
28 lines
1.6 KiB
Go
28 lines
1.6 KiB
Go
package pqkem
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// CallbackHandler is implemented by the host and invoked by the library. The
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// library only reports events; the host owns the reaction. Keeping this an
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// interface — rather than touching the transport or keying directly — is what lets
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// the KEM code be extracted as a standalone library.
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type CallbackHandler interface {
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// OnNewPSKReady fires when a fresh post-quantum PSK has been derived for a peer
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// and must be programmed into the consumer's secure channel. The protocol has no
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// explicit confirm: the initiator fires it on receiving the answer, the responder
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// fires it right after deriving the PSK from the offer and before sending that
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// answer. A fired callback therefore means the key is derived locally, not that the
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// peer has confirmed it — the next offer is the later acknowledgement.
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//
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// gen is a per-peer monotonic generation: a later exchange always carries a higher
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// gen. Callbacks can be applied out of order (two exchanges deriving concurrently),
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// so the host must ignore a call whose gen is not newer than the one it last applied
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// for that peer, or it may restore an older PSK over a newer one and split the tunnel.
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OnNewPSKReady(remoteID RemoteID, gen uint64, psk PSK) error
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// OnRekeyFailed fires when an exchange fails to converge within the allotted time.
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// Recovery is host-defined: the library reports the event and does not dictate the
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// reaction. The shipped NetBird host, for instance, re-bootstraps the KEM over
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// signalling and keeps the tunnel on its previous PSK rather than tearing the
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// connection down.
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OnRekeyFailed(remoteID RemoteID) error
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}
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