Bootstrap token RNG seeding should be made explicit #67

New Issue

Skipper · 2026-04-05T16:23:09Z

Skipper commented

2026-04-05 16:23:09 +00:00

Info

Severity: LOW
Attack vector: network-only

Impact

Could allow bootstrap token prediction if the RNG is not actually seeded from operating-system entropy.

Description

The bootstrap token generation path uses rand::make_rng(), and the report calls out that the entropy source should be explicitly confirmed. If this ever resolved to a deterministic or incorrectly seeded RNG, bootstrap tokens would become predictable.

Example flow

Determine or influence the RNG seed if it is not OS-backed.
Predict future bootstrap tokens.
Present a predicted token before the legitimate operator uses it.
Register a malicious user-agent key.

Mitigation

Use an explicitly OS-seeded RNG path and assert that bootstrap token generation always derives entropy from the operating system.

# Info **Severity**: **LOW** Attack vector: network-only ## Impact Could allow bootstrap token prediction if the RNG is not actually seeded from operating-system entropy. ## Description The bootstrap token generation path uses `rand::make_rng()`, and the report calls out that the entropy source should be explicitly confirmed. If this ever resolved to a deterministic or incorrectly seeded RNG, bootstrap tokens would become predictable. ## Example flow 1. Determine or influence the RNG seed if it is not OS-backed. 2. Predict future bootstrap tokens. 3. Present a predicted token before the legitimate operator uses it. 4. Register a malicious user-agent key. ## Mitigation Use an explicitly OS-seeded RNG path and assert that bootstrap token generation always derives entropy from the operating system.

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Reference: MarketTakers/arbiter#67