Report a vulnerability in private, with a GitHub security advisory:

1. Open https://github.com/codemyriad/cassini-android/security/advisories/new.
2. Write what the problem is, which version has it and the steps that show it.
3. Send the report.

Do not open a public issue or pull request for a vulnerability. Do not attach private recordings, transcripts or voiceprints. If the report needs audio, use audio that you made for the report.

If the link does not open a form, open a public issue that asks for a private contact. Do not put details of the problem in that issue.

We reply to each report. When a fix is in a release, we publish the advisory. If you agree, the advisory gives your name.

Cassini for Android is beta software. Only the latest release gets security fixes. We do not put fixes into older releases.

We publish the APK only on the GitHub Releases page. Each release has these files:

• cassini-android-VERSION.apk: the APK.
• cassini-android-VERSION.apk.sha256: the SHA-256 of the APK.

All release APKs have the same signing key, the beta key. Thus an update installs over the earlier version without an uninstall, and the downloaded models stay. Version 0.2 does not show the notes of 0.1.x. Before you update from 0.1.x, transcribe each note that has no transcript. Then save each note as a Cassini document (.opus), and open these files in 0.2. Version 0.1.x cannot save a recording without a transcript as a Cassini document, and there is no other way to move such a recording to 0.2. The update does not delete the files of 0.1.x, which include the 0.1.x voiceprints. PRIVACY.md tells how to delete them. The SHA-256 digest of the signing certificate is in scripts/beta-signing-cert.sha256:

06b2a95b3a6e6e7cdef618999d37631a18216307def007102980db71cf2387ec

If the APK has a different certificate or is debuggable, the release job of CI stops.

To make sure that you have a genuine APK, do these steps:

1. Run sha256sum -c cassini-android-VERSION.apk.sha256 in the directory of the two files.
2. Run apksigner verify --print-certs cassini-android-VERSION.apk (apksigner is in the Android SDK build tools).
3. Compare the line Signer #1 certificate SHA-256 digest with the digest in scripts/beta-signing-cert.sha256.

The repository does not contain the keystore. The Gradle files contain no passwords. The build reads the passwords from the environment variables CASSINI_RELEASE_STORE_PASSWORD, CASSINI_RELEASE_KEY_PASSWORD and CASSINI_RELEASE_KEY_ALIAS. CI gets the keystore from a repository secret. Until the owner sets new passwords, CI and scripts/device-smoke.sh use the standard passwords of the Android debug keystore (android, androiddebugkey) as a fallback. Thus the keystore file is the only secret. docs/release.md gives the details.

A later stable release can have a different signing key. If the key changes, Android does not install the update over the beta version. You must then uninstall the beta version, and the uninstall erases the notes and the downloaded models. Before you uninstall, save each note as a Cassini document (.opus).

The APK does not contain the speech models. The app downloads them only after the user agrees to the download. The app downloads the models from these hosts:

These hosts can send the download to a different download host (a redirect). The app follows a redirect only to a host in the list ModelCatalog.DOWNLOAD_HOSTS. PRIVACY.md gives this list.

ModelCatalog.kt pins the URL, the size and the SHA-256 of each model file. The app compares the size and the SHA-256 of each downloaded file with the pin before it installs the file. If they are not equal, the app deletes the partial file and does not install it. The Nemotron model is a Zstandard file. The app compares the hash of the compressed file before decompression, and the hash of the model after decompression.

If a host gives a file with a different hash, the app stops the download. Report this to us, because it can show that a host is not safe.

The app contains a sherpa-onnx AAR that we build from a pinned source and scripts/streaming-diarization.patch. scripts/native-dependencies.json pins the SHA-256 of the source archives, of the patch and of the prebuilt AAR on the GitHub release native-sherpa-onnx-1.13.7-nemotron.3. scripts/setup.sh and scripts/verify-native-runtime.sh compare the AAR with the pin. Each week, and after a change to the native inputs, CI builds the AAR from source and compares its SHA-256 with the pin. docs/native-runtime.md gives more detail.

These parts are in scope: the app, its build, the scripts in this repository and the model pins. If you find a vulnerability in an upstream project (sherpa-onnx, ONNX Runtime, libopus, zstd-jni), report it to that project. If the vulnerability also affects Cassini, tell us too.