53ba8ea42e919ead06bc36c5e445f2affb741947
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Commits
| Author | SHA1 | Message | Date | |
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 Paul HittandClaude Opus 5
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5f983c1455 |
Android: the app, and the two things only a phone could tell us
There is now a Flamenet Messenger app that installs, launches, creates an account on a self-hosted relay, registers a device, publishes prekeys, and stores all of it in an Android Keystore-backed vault. Verified on an emulator through the actual screens, not by unit test. 92 JVM tests, 37 cross-engine, 9 on-device, 3 against live relays. Two findings, both of which the JVM suite was structurally incapable of producing. **Android has no ordinary Ed25519 provider.** `KeyPairGenerator.Ed25519` and `KeyFactory.Ed25519` come from `AndroidKeyStore` and from nowhere else -- probed on API 35 rather than assumed -- and Keystore only makes keys it keeps. Every Ed25519 key in this engine is one we must hold: a device identity in our own vault, an account key derived from a passphrase. So the JCA route could never have worked. It compiled, passed 81 tests on a laptop, and threw "Not initialized" on the first launch on a phone. Worse, it was LATENT: a wrong password failed before any key was minted, so the error path worked perfectly while the happy path was broken. Ed25519 now uses BouncyCastle's `math.ec.rfc8032` core directly -- the engine's one real dependency, present because the platform leaves a hole, and a strictly better answer than the non-constant-time keygen it replaces. ProviderProbeTest records the measurement so nobody guesses again. **The prekey field is `prekeys`, not `opks`.** I guessed. The relay accepted the registration, returned 200, and stored nothing -- so the device was published and could not be started with, a failure with no error anywhere. Caught by a live test against the throwaway fleet, which exists because the same path through the emulator takes four minutes to say "timed out" and nothing about where. Two testing traps, recorded where they bite: An indeterminate progress spinner animates for ever, so Compose's test clock never goes idle and `waitUntil` never evaluates its condition -- it fails on the full timeout, reading as "sign-up is broken" when sign-up works. Auto-advance is now disabled around the wait only; disabling it for the whole test is the next mistake, because the app opens on a spinner while it reads the vault. Wiping the Keystore in `@Before` deletes the key the already-launched activity is holding, and every later write fails against a key that no longer exists. The test signs out through the UI instead, which is both safe and what a person does. Failure messages now include what the screen was showing. A bare timeout sends you to the network, the relay and the crypto in turn while the app has been displaying the reason the whole time. Also corrects a note that said this Mac had no Android SDK. It does. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |
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Paul HittandClaude Opus 5
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8a3770f1d1 |
Kotlin: the session layer, verified across the wire
An app does not use X3DH and a ratchet, it uses "send this string to that person". This is that layer: device identities with prekeys and rotation, envelopes as the relay actually carries them, and sessions that survive being put away and taken out again. 11 unit tests, and the interop harness grows from 23 assertions to 37 -- the new ones at the envelope level, which is where this protocol's one shipped bug lived. A client and a relay disagreed about a field name and nothing caught it until a live round trip; hand-assembled arguments to X3DH would not have. Kotlin now builds a whole envelope, the web engine's own session layer parses it, and both directions agree on the associated data. Three decisions worth stating. Retired signed prekeys are kept for longer than the relay keeps undelivered mail. A sender fetches a bundle, encrypts against that prekey id, and the envelope can then sit in a queue for the relay's full retention window. Discarding the private half at rotation turns every one of those into an AEAD failure -- which the receiving client cannot distinguish from an attack. A prekey retired past retention is refused outright rather than guessed at, for the same reason: guessing derives a garbage secret and reports it as tampering. The handshake block rides every message until one is answered, not until one is sent. Any message may be the first to arrive. Sessions archive with their skipped message keys, and the harness proves it against the peer rather than against our own bytes. Those keys are the messages already in flight; an archive that drops them loses exactly the mail that was in the air when the app was killed. The failure this whole path exists to prevent is a client that loses session state, re-registers a device, and shows every contact "security keys changed" -- the warning that is supposed to mean an attack. `org.json` is compileOnly: it is in the Android framework, so it costs nothing on a phone and bundling a copy would shadow the platform's. Safe only because the two encodings that must match byte-for-byte -- the ratchet header and the canonical log leaf -- are built by hand; Android's implementation preserves key order and the reference one does not. Also adds PARITY.md: what the iOS app does, what Android does, what is left. It is the definition of done, and a row moves only when something tests it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |
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Paul HittandClaude Opus 5
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06b97ca69b |
Start Android with the engine, held to the published vectors
Android does not exist, and the first thing it needs is not a screen. It needs the protocol implemented a third time — which is only worth anything if the third implementation is checked against the spec and the published vectors rather than against a reading of our own Swift. So `android/engine` is a plain Kotlin/JVM library with no Android in it: no SDK, no emulator, no device, and therefore gateable in CI on Linux like everything else. It reads engine/test/vectors/protocol-v1.json from its one location rather than carrying a copy, because a vector transcribed into the test that checks it is a vector that agrees with itself. Covered so far: safety numbers (§7) and key transparency verification (§19) — RFC 6962 leaf and node hashing, the unbalanced split, and bottom-up audit paths. Nine tests, all green against the same file the JavaScript and Swift engines answer to. The §19 tests are the ones worth having. A top-down reading of a bottom-up audit path yields the correct root for every left-spine index, so it passes any suite that only checks index 0 — the vectors pin a right-descending index, and the tests assert both that the published path verifies and that the same path reversed does not. android/README.md lists what is missing — X25519, X3DH, the ratchet, sealed sender, both post-quantum halves, the relay client, the app — as a table rather than as an omission. Android stays honestly marked "not started" on the site until that list is shorter. Bytecode targets 17 without demanding a JDK 17 be installed: a jvmToolchain(17) fails on any newer JDK, which is a poor trade for a library with no JDK 17-specific behaviour. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |