C04-TS: Yes
Rationale
The WireGuard receive path silently discards handshake packets with an invalid MAC1. Normal handshake replies require a valid known-peer initiation. This provides a concrete defense against blind active probing of the endpoint.
Assessment method
Pinned receive-path inspection and primary protocol documentation; no runtime test
Source context
Tailscale wireguard-go dependency, MAC1 and cookie branches
Outstanding qualification
Bounded defense, not universal invisibility. A prober knowing the responder public key can form MAC1 and may obtain an under-load cookie response without being an authorized peer. Replay, timing and other exposed services require separate assessment. No active scan was executed; public DERP/control servers are not hidden by this endpoint mechanism.
Public sources
- https://raw.githubusercontent.com/tailscale/wireguard-go/e61b6b78110b/device/receive.go
- https://raw.githubusercontent.com/tailscale/wireguard-go/e61b6b78110b/device/receive.go
- https://www.wireguard.com/protocol/
- https://raw.githubusercontent.com/tailscale/tailscale/566f89e0fb2aa4b2f1ebf98761e45e62aa5ef225/wgengine/magicsock/magicsock.go
- https://raw.githubusercontent.com/tailscale/tailscale/566f89e0fb2aa4b2f1ebf98761e45e62aa5ef225/derp/derpserver/derpserver.go
- https://tailscale.com/docs/reference/derp-servers
Editorial evidence references
The following identifiers refer to research records not included in this public package; they are not public links.
- round592.html
- round592-sources.json