Keyhole

Security Notes ​

Ed25519 only ​

RSA and ECDSA keys are rejected at authentication. Ed25519 signatures are deterministic, which is required for reproducible key derivation. RSA signatures are probabilistic — the same input produces different signatures each time — so they cannot be used to derive stable encryption keys.

Path isolation ​

Secrets are namespaced per user; one user cannot access another's secrets. Paths containing .., ., or any component starting with . are rejected.

Secret size limit ​

Secrets are capped at 64 KB.

Agent required for get/set ​

If the SSH agent is not forwarded, the server returns an error immediately rather than hanging.

No shell ​

The server accepts only structured commands; there is no shell access.

Vault key wrapping ​

Vault keys are individually wrapped per member using their SSH agent signature, so revoking a member does not require re-encrypting all vault secrets.

Two-phase vault invite ​

Invite tokens wrap the vault key with a temporary HKDF-derived key; on accept, the vault key is re-wrapped with the member's agent key. The HKDF info parameter includes the vault name and target username for domain separation. See Encryption for details.

Invite expiration ​

Both user invite codes and vault invite tokens expire after 72 hours. Expired invites are rejected. User invite codes are consumed atomically using a filesystem rename to prevent race conditions.

Server secret ​

The server secret must be at least 64 characters. The server will refuse to start with a shorter value. On first run, keyhole auto-generates a 64-character alphanumeric secret; if you provide your own via the config file, it must meet the same minimum length.

DEPRECATED

KEYHOLE_SERVER_SECRET is deprecated and will be removed in a future release. Environment variables are visible through /proc, ps, and are inherited by child processes. Use the server_secret field in your HCL config file (with 0600 permissions) or let keyhole auto-generate the secret file in the data directory instead.

DANGER

Store server_secret somewhere safe and separate from the data directory. Without it, every stored secret is permanently inaccessible.