In Tailnet Lock, there is an implicit limit on the number of rotation
signatures that can be chained before the signature becomes too long.
This program helps tailnet admins to identify nodes that have signatures
with long chains and prints commands to re-sign those node keys with a
fresh direct signature. It's a temporary mitigation measure, and we will
remove this tool as we design and implement a long-term approach for
rotation signatures.
Example output:
```
2024/08/20 18:25:03 Self: does not need re-signing
2024/08/20 18:25:03 Visible peers with valid signatures:
2024/08/20 18:25:03 Peer xxx2.yy.ts.net. (100.77.192.34) nodeid=nyDmhiZiGA11KTM59, current signature kind=direct: does not need re-signing
2024/08/20 18:25:03 Peer xxx3.yy.ts.net. (100.84.248.22) nodeid=ndQ64mDnaB11KTM59, current signature kind=direct: does not need re-signing
2024/08/20 18:25:03 Peer xxx4.yy.ts.net. (100.85.253.53) nodeid=nmZfVygzkB21KTM59, current signature kind=rotation: chain length 4, printing command to re-sign
tailscale lock sign nodekey:530bddbfbe69e91fe15758a1d6ead5337aa6307e55ac92dafad3794f8b3fc661 tlpub:4bf07597336703395f2149dce88e7c50dd8694ab5bbde3d7c2a1c7b3e231a3c2
```
To support this, the NetworkLockStatus localapi response now includes
information about signatures of all peers rather than just the invalid
ones. This is not displayed by default in `tailscale lock status`, but
will be surfaced in `tailscale lock status --json`.
Updates #13185
Signed-off-by: Anton Tolchanov <anton@tailscale.com>
151b77f9d6