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Series B — Session 06: IPC & Middleware Security (Auth, Integrity, Replay)

Objective - Explain how to secure IPC channels and middleware in IVI stacks: authenticated encryption, replay protection, and per‑message binding.

Prereqs - Familiarity with the IPC mechanisms used (dbus, sockets, binder, custom RPC).

Correct Path (pattern)

  1. Use AEAD for message confidentiality and integrity (per-message nonce derived from monotonic counter + connection ID).
  2. Include sequence numbers or nonces inside associated data and maintain per-peer state to prevent replays.
  3. Authenticate peers (mutual TLS, token exchange via TEE, or authenticated IPC frameworks).

Break Case (single-variable change) - Remove sequence numbers from messages; attacker replays previously captured messages and triggers unauthorized actions.

Observation - Without replay protection, valid messages can be reused to cause state changes.

Why - IPC channels are often trusted implicitly; cryptographic bindings and authentication are required to preserve invariants.

Hard Rules - Bind each IPC channel to authentication and encrypt messages with AEAD. - Include and verify monotonic counters or timestamps for replay protection. - Fail closed: reject messages with missing/invalid authentication metadata.

Homework - Design an IPC message envelope schema containing AEAD ciphertext, AD (sender ID, seq), and verification rules.