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riccardom
a78d587e7a
To ensure two peers agree on a key, we need asymmetry. one peer is
the controller ("initiator") the other is the "responder".
Otherwise imagine two offers in parallel driving two answers at the same time
A B
| <----B-OFFER----- |
| -----A-OFFER----> |
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---------------------------------
|****** ICE + WG Handshake ****** |
---------------------------------
| |
| <----B-ANSWER---- |
| -----A-ANSWER---> |
PSK is derived on receive of offer, so A and B derive different PSKs.
When WG handshake takes place it picks misaligned PSKs.
So we impair the two nodes and only the offer of one of the two (the controller/initiator)
carries the KEM material.
This means that if the responder OFFER/ANSWER comes first, when the controller/initiator's one
completes (and the genuine PSK is shared between A and B, we need to force a new WG handshake with
the proper keys.
25 lines
1.4 KiB
Go
25 lines
1.4 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. It is invoked at
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// the commit point of each side: the initiator on receiving the answer, the
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// responder on receiving the confirm.
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//
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// bootstrap is true when the PSK came from a signalling exchange (initial setup or
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// a wake re-negotiation) rather than a data-path rotation. On bootstrap the consumer
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// must ensure the live channel actually adopts the PSK now (e.g. force a WireGuard
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// re-handshake) — the channel may already be up on a pre-PQ key. A rotation
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// (bootstrap=false) is adopted at the channel's next natural rekey.
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OnNewPSKReady(remoteID RemoteID, psk PSK, bootstrap bool) error
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// OnRekeyFailed fires when an exchange fails to converge within the allotted
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// time. The host should tear the peer connection down so it re-establishes, and
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// log a WARN. The library reports the event; it does not dictate the reaction.
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OnRekeyFailed(remoteID RemoteID) error
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}
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