[S2] Unsigned v1 licenses still accepted → complete Ed25519 bypass

[DsThakurRawat]

Labels: security, bug, pro, priority:high
File: src/tether/pro/license.py:212 (version not in (LICENSE_VERSION, LICENSE_VERSION_LEGACY_UNSIGNED)), :222 (signature verified only when == LICENSE_VERSION)

Description. load_license accepts both v2 (signed) and v1 (legacy unsigned). For v1 it skips signature verification entirely and only logs a warning.

Why it matters. An attacker writes ~/.tether/pro.license with license_version=1, tier="enterprise", expires_at far in the future, signature="", and a hardware_binding matching their own host (obtainable via probe_hardware_binding). No private key required — the entire v2 Ed25519 chain is bypassed by selecting the legacy version. Classic signature-downgrade; unlocks all Pro entitlements for free.

Tasks.

• Reject v1 licenses in released builds; gate acceptance behind an explicit TETHER_DEV=1 env flag.
• Require a valid signature for every accepted version.
• Add a test asserting a v1 license is refused unless the dev flag is set.

Dedup. No issue/PR covers the v1 acceptance path. PR #229 preserves signed fields on heartbeat rewrite — different concern.

[rylinjames]

The code fix has merged in PR #312. It now requires signed v2 licenses, verifies nonce-bound Ed25519 heartbeat attestations, rejects unsigned v1, and fails paid admission closed at the signed deadline (including Python 3.10 timeout behavior). All seven required CI jobs passed, including both supported Python versions. I am keeping this issue open until the Worker/client rollout and signer-key migration are verified in production; this maintenance pass did not deploy or rotate secrets.