Files
punktfunk/clients/android
enricobuehler 8103958169 fix(security): the plugin lane stops being a way in
Acts on the 2026-08-05 host security review. 36 of its 38 findings; the two
exceptions are recorded below and in the review doc.

The review's headline is that `plugin_may_access` was the one authorization
gate in the system that was allow-by-default — a hand-maintained denylist of
route prefixes, where every sibling gate is deny-by-default. Its own doc
comment names the two capabilities it exists to withhold, and both were
reachable one route over, because ~1450 commits of new routes were added and
the list was never one of the things anyone remembered to update.

So the gate is now an allowlist, and a test walks the live route table and
fails the build for any route that has not been deliberately classified for
both non-admin lanes. That test is the actual fix: it is what stops the next
route from arriving pre-authorized.

Route reachability and field authority turned out to be different questions.
A provider plugin has to be able to reconcile its own library entries — that
is what a scanner plugin IS — but `prep` and a `command` launch inside that
payload are handed to `/bin/sh -c` as the host user, and every execution site
documents them as operator-typed. Requests now carry the lane that authorized
them, and those two fields are refused to everyone but the operator's own
token.

The art proxy read any absolute path off disk in the host process, which on
Windows is LocalSystem, from a path the plugin lane could write and then read
back — so it yielded `mgmt-token`, which is full admin. It now serves only
real images (extension AND magic bytes, so a renamed secret fails), only from
inside an allowed root, only after canonicalization, and never over UNC; and
a path it would refuse to serve can no longer be persisted in the first place.

On Windows, the config-dir hardening was skipped exactly when it was needed —
it ran only in the branch that CREATES host.env, so the case it was written
for (a local user pre-created the directory and planted one) was the one case
it never ran in. It is now unconditional and first, an existing host.env is
re-owned, and the inheritable OWNER RIGHTS ACE that kept an attacker's files
theirs after the directory was re-owned is gone. The identity and token
readers were hardening the directory only on the path that GENERATED a new
secret, so a planted cert/key or token was adopted verbatim and permanently;
they harden before the first read now.

`ensure_admin_only_source` is implemented. The 2026-07-05 audit recorded it as
FIXED and it was in no commit in this repository's history — the local EoP it
described was live, and it is the payload half of the config-dir chain above.

Also: the three input planes are bounded and lossy like the mic plane on the
same loop already was; Android's library client no longer accepts any
publicly-trusted certificate for the pinned host; the usbip vhci nodes get
their own group instead of riding on `input`, which every packaging scriptlet
tells users to join; a registry URL can no longer inject a TOML table into
bunfig.toml; the pairing cooldown is charged before the arming state is read,
so armed/disarmed is no longer a free oracle; and the whole Low tier, of which
the two worth naming are a clipboard MIME NUL that panicked the host on one
control message, and an unauthenticated global logout that let any LAN peer
sign the operator out on a loop.

NOT fixed, deliberately:

  H-3 (plugin UIs framed allow-same-origin). Dropping allow-same-origin does
  not work: the document's origin goes opaque, its subresource requests are
  then cross-site, the SameSite=Lax session cookie is not sent, and every
  plugin asset 302s to /login. The "open in new tab" link is the same
  escalation with no iframe at all, so the sandbox attribute is not where this
  gets fixed either. It needs a second listener — a distinct origin that is
  still the same site — which changes the console's deploy model and wants
  on-glass validation. The mechanism and the dead end are written down at the
  iframe.

  H-6 registry authentication, whose other half lives in unom/infra. The
  in-repo halves are done: workflow_dispatch inputs no longer interpolate into
  run: blocks (one of them in the step holding UPDATE_MANIFEST_KEY), and the
  syft installer is pinned to its tag instead of main. Digest pinning is left
  until the registry is authenticated, because a tag — content-keyed or not —
  can simply be overwritten while anonymous pushes are accepted.

M-5 is half done: the oracle is closed, but binding the arming window needs
the console to learn the fingerprint first, which is a knock-then-bind flow
rather than an edit.

Verified: cargo fmt --all --check clean; cargo check --all-targets green on
Linux and on Windows (confirmed non-vacuous — a planted type error in
windows/install.rs fails the build); scripts/xcheck.sh windows check green;
cargo test -p punktfunk-host --bins 416 passed, the single failure being
gamestream::stream::tests::sender_delivers_batches, the known qemu-environmental
UDP-loopback flake that fails identically on clean main in the same container;
cargo test -p pf-clipboard 13 passed; web console typechecks.
2026-08-05 17:12:12 +02:00
..

punktfunk — Android client (phone & TV)

The native Android app for streaming a punktfunk host to your phone, tablet, or Android TV. A Compose app that finds hosts on your network, pairs with a PIN, and streams at the display's own resolution — with hardware HEVC decode, HDR10, and controller support, built for both touch and the couch (D-pad / gamepad focus navigation).

Features

  • Hardware decode — NDK AMediaCodec HEVC → SurfaceView, including HDR10 (Main10 / BT.2020 PQ), with low-latency tuning and a live stats HUD.
  • Audio both ways — Opus + AAudio playback with a jitter ring, plus mic uplink to the host.
  • Controller support — buttons + axes with rumble and HID feedback (lightbar / adaptive triggers); D-pad / gamepad focus navigation for TV and phone.
  • Find hosts automatically — native mDNS discovery; first connect does a one-time SPAKE2 PIN pairing (or TOFU on trusted LANs), then reconnects on a Keystore-wrapped, pinned identity.
  • Compose UI — Connect / Settings / Stream screens with Material You theming.

Built for arm64-v8a + armeabi-v7a + x86_64 — the 32-bit armeabi-v7a slice is what keeps the app installable on the many 32-bit Google TV / Android TV streamers (Walmart onn. 4K, Chromecast with Google TV, budget Amlogic boxes) that otherwise reject a 64-bit-only build as "not compatible".

Get it

Published to Google Play (Internal Testing) — join the beta via the Discord. Per-device setup and pairing: docs.punktfunk.unom.io/docs/install-client.

How it's built — Rust-heavy

Kotlin can't import the cbindgen C header the way Swift can, so a native bridge is unavoidable. We write it in Rust and link punktfunk-core directly — so the Android client reuses the Linux client's orchestration (audio jitter ring, VK keymap inverse, latency/skew math, capture state machine, trust logic) instead of re-porting it into Kotlin.

Side Owns
Rust (native/libpunktfunk_android.so) the JNI seam, NativeClient (QUIC control + UDP data plane), AnnexB → AMediaCodec decode (incl. HDR10), Opus + AAudio audio + mic, controller feedback, latency math, trust/pairing, mdns-sd discovery
Kotlin (app/, kit/) Compose UI, SurfaceView lifecycle, input capture, the Wi-Fi MulticastLock + permission UX, Keystore identity

The single seam is io.unom.punktfunk.kit.NativeBridgeJava_io_unom_punktfunk_kit_NativeBridge_*.

native/           Rust cdylib (workspace member) — links punktfunk-core directly
  src/lib.rs        crate doc · JNI_OnLoad · version probes
  src/session/      session lifecycle: connect/pair + trust, plane start/stop, input shims
  src/decode.rs     AnnexB → AMediaCodec HEVC hardware decode → SurfaceView (incl. HDR10)
  src/audio.rs · src/mic.rs   Opus + AAudio playback / mic uplink
  src/feedback.rs · src/stats.rs   rumble + HID feedback; live video stats
  src/discovery.rs  native mdns-sd browse of the host's _punktfunk._udp advert
app/              :app — Compose UI: Connect / Settings / Stream (phone + TV)
kit/              :kit — NativeBridge · native mDNS discovery · Gamepad · Keymap · Keystore identity

Build & run

Prerequisites: Android SDK + NDK r30 (30.0.14904198), platforms;android-37.0, build-tools;37.0.0, cmake;3.22.1 (builds libopus); JDK 21 (AGP 9.2 runs on JDK 1721, not a newer default); Rust with rustup target add aarch64-linux-android armv7-linux-androideabi x86_64-linux-android and cargo install cargo-ndk. Toolchain is pinned (AGP 9.2 · Gradle 9.4.1 · Kotlin 2.3.21 · Compose BOM 2026.05.01 · compileSdk 37 · minSdk 28).

Android Studio: open clients/android — it uses its bundled JBR 21, and the cargoNdk* task builds the .so as part of the normal build.

CLI (point Gradle at JDK 21 if your machine default is newer):

export JAVA_HOME="$(/usr/libexec/java_home -v 21)"   # or your Temurin 21 path
cd clients/android
./gradlew :app:assembleDebug     # cargo-ndk cross-compiles libpunktfunk_android.so first
./gradlew :app:installDebug      # onto a running emulator/device
# emulators from env setup:  emulator -avd pf_phone   |   emulator -avd pf_tv

The debug APK lands in app/build/outputs/apk/debug/. Launch it, pick a host, pair, and stream.