Admin › Backups shows a verdict first (off, not set up, waiting, backed up,
overdue, failing since when), Back up now, Test destination and the latest
runs, with the settings beside them.

- backup.Service: one run at a time, bounded at 30 minutes; the schedule
  ticks every 5 minutes, catches up a slot missed while the server was down,
  and retries a failure after an hour and then after as long as it has been
  failing. Runs are recorded in backup_runs, pruned after 90 days; a run cut
  off by a shutdown is marked failed at the next start.
- A folder destination writes database/minstrel-<UTC stamp>.tar and refuses
  a folder that isn't there. An S3 destination stages the file, hashes it,
  and uploads it under database/ through a throttled reader (4 MiB/s by
  default, 0 for no limit).
- Test destination checks the form as typed and only lists.
- The bucket secret is sealed like every stored credential; backup_settings
  and backup_runs are left out of the backup itself.
- The panel polls only while a run is going, capped at the run limit plus
  five minutes.

The music switch named in the task is left to #6774, so no control ships
that does nothing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2026-11-02 14:50:55 -05:00

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Security notes

What Minstrel does to protect accounts, and the reasoning behind the decisions that look odd at first. For deployment steps, see hosting.

Accounts and sessions

Passwords are stored as bcrypt hashes.
Login, registration and password reset are rate-limited: 10 failed sign-ins per account and 50 per address per 15 minutes, with similar limits on register, forgot-password and reset. The Subsonic /rest API shares the login limits. An unknown username takes as long to reject as a wrong password, so timing doesn't reveal which accounts exist.
Sessions are random 256-bit tokens; the server stores only their SHA-256. A session ends after 30 days unused or 365 days in total. Changing your password signs out your other devices; a password reset, or an admin resetting it, signs out all of them.
API keys (the OpenSubsonic apiKey) are stored as SHA-256 too, so a key is shown once, when you generate it in Settings, and can only be replaced after that.
The first account on an empty server needs the setup token from the server log (see hosting).
Password-reset links are built only from the configured public address, never from the request's Host header.

Requests

Request bodies are capped at 4 MiB and must arrive within 30 seconds. Streams and the live-event connection are unaffected.
Every response carries X-Content-Type-Options: nosniff, Referrer-Policy: strict-origin-when-cross-origin, a restrictive Permissions-Policy and X-Frame-Options: DENY. The web app also gets a Content-Security-Policy that allows only its own scripts, by hash.
Media responses are Cache-Control: private, so a shared cache never keeps one user's audio or artwork for another.

CSRF: SameSite cookies plus JSON-only writes

There are no CSRF tokens. The session cookie is SameSite=Strict, so browsers don't send it with requests that start on another site. That leaves one gap: SameSite treats every subdomain of the same registrable domain as the same site, so a different app on other.example.com could still send a request carrying the cookie. To close it, any state-changing /api request authenticated by the cookie must have a JSON body (Content-Type: application/json) or no body at all. An HTML form or a script on another origin can't send JSON without a CORS preflight, and Minstrel answers no cross-origin preflight. Requests authenticated with a bearer token or the Subsonic query parameters carry nothing a browser attaches on its own, so they aren't checked.

Credentials Minstrel has to read back

Some credentials can't be hashed, because Minstrel has to send or compare the value itself:

the API keys and passwords for indexers, Prowlarr and download clients;
the AcoustID key, and the cover-art and tag provider keys;
the SMTP password;
the secret key of the S3 bucket backups go to;
each user's ListenBrainz token and Subsonic password.

These are encrypted in the database (AES-256-GCM). Each column has its own key, derived from the stream secret (MINSTREL_STREAM_SECRET, or the stream_secret file in the data directory), and each value is bound to its row. The stream secret is never stored in the database, so a copy of the database alone doesn't reveal any of them. None of them is ever sent back to a browser: Settings only shows whether one is set.

Keep the stream secret with the data directory, and don't change it casually. If it changes, every stored credential reads as not set, and each one has to be entered again in Settings (Subsonic passwords generated again). Minstrel logs a warning for each one that no longer opens.

Classic Subsonic clients sign in with t and s: the MD5 of the password followed by a random salt. To check that, the server has to know the password itself, so supporting this sign-in method means storing a password Minstrel can read: the Subsonic password, encrypted as described above.

The recommended way in is the API key. Clients that support the OpenSubsonic apiKey should use it. The key is stored hashed and can be replaced at any time in Settings.
The Subsonic password is never your login password. Minstrel generates it (Settings → Subsonic password), shows it once, and lets you replace or turn it off. Because it is random, even someone holding both the database and the stream secret gains access to this server's Subsonic API and nothing else: it can't be a password you also use somewhere else.
t/s and p= sign-in are off for an account until it has a Subsonic password. Plain p= sign-in is additionally off server-wide unless subsonic.allow_plaintext_password is enabled.
minstrel admin reset-password changes only the login password. Older versions also copied it into the Subsonic password; upgrading clears every Subsonic password once, so those copies are gone. An account that used t/s sign-in needs a new Subsonic password generated in Settings.

Android allows plain HTTP

The Android app permits cleartext connections, for two reasons that can't be narrowed to a list of hosts. The server address is whatever the user types, and many self-hosted servers run plain HTTP on a LAN. And UPnP, DLNA and Sonos speakers are controlled over plain HTTP at addresses that are only known once they're discovered. The reasoning lives in android/app/src/main/res/xml/network_security_config.xml.

This doesn't weaken app updates: an APK altered in transit fails the platform's signature check. It does mean a server reached over plain HTTP across the internet exposes the session cookie in transit, which is why the hosting guide puts public servers behind HTTPS.

On the phone, the session cookie is encrypted with a key held in the Android Keystore, so a copy of the app's files doesn't yield a usable session.

Build pipeline

Nothing is published unless every check passes: the Go, integration, web and Android test suites, govulncheck against the toolchain that builds the image, and npm audit on every web dependency, build tooling included. See .gitea/workflows/release.yml.

Reporting a problem

Open an issue on the repository, or contact the maintainer privately first if it's something that shouldn't be public until fixed.

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