The SSHCopyIDInstaller used StrictHostKeyChecking=accept-new on the ssh-copy-id
and sftp-verify connections, so even though the bridge verifies the box host-key
fingerprint against the hub descriptor BEFORE installing, the actual install
connection was not pinned to that verified key — a MITM could substitute a
different key in the gap between the scan and the install (TOCTOU).
Now the bridge threads the scanner-verified known_hosts line into KeyInstaller,
which writes it to a temp known_hosts and connects with StrictHostKeyChecking=yes
+ UserKnownHostsFile — the install/verify sessions refuse any key but the one the
bridge already matched. Empty known_hosts now refuses to install.
Test asserts the installer receives the pinned known_hosts; red-proofed by passing
an empty line (the pre-fix TOFU shape) → test fails. Addresses the security-review
"host-key TOFU after verify" finding on internal/offsiteapply/seams.go.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6
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