Firefox/RemoteSettings

Firefox Remote Settings

Remote Settings is a Mozilla service that makes it easy to manage evergreen settings data in Firefox. Firefox/Kinto is used for syncing of data. A simple API is available in Firefox for accessing the synchronized data.

Key Features

• Admin UI (generated from data schema)
• Data history
• Preview data (QA)
• Sign-off (review)
• File attachments
• Email notifications
• Content signature (Autograph integration)
• Single endpoint for polling for changes
• Client synchronization (diff based, local db)
• Client Telemetry
• Robust protocol (retry, precondition headers, backoff, …)

const { RemoteSettings } = ChromeUtils.import("resource://services-settings/remote-settings.js", {});

RemoteSettings("my-collection")
  .on("sync", (e) => {
    // e.data.current = [ Record, Record, ... ]
  });

Resources

• API client docs (How to use RemoteSettings in Gecko)
• OPs and staff documentation (How to create new collections etc.)
• RemoteSettings server bugs list
• RemoteSettings client bugs list
• Project milestones

about:remotesettings

A tool is available to diagnose remote settings synchronization and state. See https://github.com/leplatrem/aboutremotesettings

Use Cases

Main bucket

List	Collection	Description
Activity Stream Tippytop	tippytop	Hi-res icons for Topsites in Activity Stream
Focus experiments	focus-experiments	A/B testing of Focus features

Fennec

List	Bucket	Collection	Description
Assets catalog	fennec	catalog	The goal is to remove the static assets (fonts, hyphenation dicts, etc.) from the distribution package and download them asynchronously using a remote catalog
Experiments	fennec	experiments	A/B testing of Fennec features

See https://bugzilla.mozilla.org/show_bug.cgi?id=1201059

Security state

List	Bucket	Collection	Description
Cert intermediates constraints	security-state	intermediates	https://bugzilla.mozilla.org/show_bug.cgi?id=1361118

Certificates Pinning

List	Bucket	Collection	Description
Certificates pinning (HPKP)	pinning	pins	https://bugzilla.mozilla.org/show_bug.cgi?id=787133

Blocklists

The goal is to replace the current system — based on a single XML file downloaded everyday — by several collections.

List	Bucket	Collection	Description
OneCRL	blocklists	certificates	SSL certificates blocking / invalidation
Add-ons	blocklists	addons	Malicious blocked extensions
Plugins	blocklists	plugins	Unstable/malicious plugins
Gfx	blocklists	gfx	Unstable graphical drivers

From AMO to Kinto

Blocklists used to be managed via the addons server.

Now, the blocklist XML is generated on the Kinto server and a lambda pulls the JSON and generates the Web pages shown at https://blocked.cdn.mozilla.net

Source code: https://github.com/mozilla-services/amo2kinto/

Transition from XML to RemoteSettings

Currently the blocklist system relies on a big XML file that is downloaded every day. It contains block entries for certificates to be revoked, addons and plugins to be disabled, and gfx environments that cause problems or crashes.

Firefox (and derivatives like Thunderbird, Seamonkey, ...) downloads it on an URL that contains client information (eg. https://blocklist.addons.mozilla.org/blocklist/3/%7Bec8030f7-c20a-464f-9b0e-13a3a9e97384%7D/44.0a1/)

• phase 1: DONE: Both mechanisms run in parallel but only the legacy one will be used.
• phase 2: DONE: The source of truth for blocklist is Kinto but produces the same XML as the legacy one.
• phase 3: DONE: The nsBlocklistService should become asynchronous in order to be able to fetch info from remote settings local database
• phase 4: Eventually, blocking mechanism will rely on RemoteSettings entirely and the old XML client will be decommissioned.