1 files changed, 342 insertions, 0 deletions
diff --git a/browser/components/doh/DoHConfig.sys.mjs b/browser/components/doh/DoHConfig.sys.mjs
new file mode 100644
index 0000000000..a8736bdc2e
--- /dev/null
+++ b/browser/components/doh/DoHConfig.sys.mjs
@@ -0,0 +1,342 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * This module provides an interface to access DoH configuration - e.g. whether
+ * DoH is enabled, whether capabilities are enabled, etc. The configuration is
+ * sourced from either Remote Settings or pref values, with Remote Settings
+ * being preferred.
+ */
+
+import { RemoteSettings } from "resource://services-settings/remote-settings.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  Preferences: "resource://gre/modules/Preferences.sys.mjs",
+  Region: "resource://gre/modules/Region.sys.mjs",
+});
+
+const kGlobalPrefBranch = "doh-rollout";
+var kRegionPrefBranch;
+
+const kConfigPrefs = {
+  kEnabledPref: "enabled",
+  kProvidersPref: "provider-list",
+  kTRRSelectionEnabledPref: "trr-selection.enabled",
+  kTRRSelectionProvidersPref: "trr-selection.provider-list",
+  kTRRSelectionCommitResultPref: "trr-selection.commit-result",
+  kProviderSteeringEnabledPref: "provider-steering.enabled",
+  kProviderSteeringListPref: "provider-steering.provider-list",
+};
+
+const kPrefChangedTopic = "nsPref:changed";
+
+const gProvidersCollection = RemoteSettings("doh-providers");
+const gConfigCollection = RemoteSettings("doh-config");
+
+function getPrefValueRegionFirst(prefName) {
+  let regionalPrefName = `${kRegionPrefBranch}.${prefName}`;
+  let regionalPrefValue = lazy.Preferences.get(regionalPrefName);
+  if (regionalPrefValue !== undefined) {
+    return regionalPrefValue;
+  }
+  return lazy.Preferences.get(`${kGlobalPrefBranch}.${prefName}`);
+}
+
+function getProviderListFromPref(prefName) {
+  let prefVal = getPrefValueRegionFirst(prefName);
+  if (prefVal) {
+    try {
+      return JSON.parse(prefVal);
+    } catch (e) {
+      console.error(`DoH provider list not a valid JSON array: ${prefName}`);
+    }
+  }
+  return undefined;
+}
+
+// Generate a base config object with getters that return pref values. When
+// Remote Settings values become available, a new config object will be
+// generated from this and specific fields will be replaced by the RS value.
+// If we use a class to store base config and instantiate new config objects
+// from it, we lose the ability to override getters because they are defined
+// as non-configureable properties on class instances. So just use a function.
+function makeBaseConfigObject() {
+  function makeConfigProperty({
+    obj,
+    propName,
+    defaultVal,
+    prefName,
+    isProviderList,
+  }) {
+    let prefFn = isProviderList
+      ? getProviderListFromPref
+      : getPrefValueRegionFirst;
+
+    let overridePropName = "_" + propName;
+
+    Object.defineProperty(obj, propName, {
+      get() {
+        // If a pref value exists, it gets top priority. Otherwise, if it has an
+        // explicitly set value (from Remote Settings), we return that.
+        let prefVal = prefFn(prefName);
+        if (prefVal !== undefined) {
+          return prefVal;
+        }
+        if (this[overridePropName] !== undefined) {
+          return this[overridePropName];
+        }
+        return defaultVal;
+      },
+      set(val) {
+        this[overridePropName] = val;
+      },
+    });
+  }
+  let newConfig = {
+    get fallbackProviderURI() {
+      return this.providerList[0]?.uri;
+    },
+    trrSelection: {},
+    providerSteering: {},
+  };
+  makeConfigProperty({
+    obj: newConfig,
+    propName: "enabled",
+    defaultVal: false,
+    prefName: kConfigPrefs.kEnabledPref,
+    isProviderList: false,
+  });
+  makeConfigProperty({
+    obj: newConfig,
+    propName: "providerList",
+    defaultVal: [],
+    prefName: kConfigPrefs.kProvidersPref,
+    isProviderList: true,
+  });
+  makeConfigProperty({
+    obj: newConfig.trrSelection,
+    propName: "enabled",
+    defaultVal: false,
+    prefName: kConfigPrefs.kTRRSelectionEnabledPref,
+    isProviderList: false,
+  });
+  makeConfigProperty({
+    obj: newConfig.trrSelection,
+    propName: "commitResult",
+    defaultVal: false,
+    prefName: kConfigPrefs.kTRRSelectionCommitResultPref,
+    isProviderList: false,
+  });
+  makeConfigProperty({
+    obj: newConfig.trrSelection,
+    propName: "providerList",
+    defaultVal: [],
+    prefName: kConfigPrefs.kTRRSelectionProvidersPref,
+    isProviderList: true,
+  });
+  makeConfigProperty({
+    obj: newConfig.providerSteering,
+    propName: "enabled",
+    defaultVal: false,
+    prefName: kConfigPrefs.kProviderSteeringEnabledPref,
+    isProviderList: false,
+  });
+  makeConfigProperty({
+    obj: newConfig.providerSteering,
+    propName: "providerList",
+    defaultVal: [],
+    prefName: kConfigPrefs.kProviderSteeringListPref,
+    isProviderList: true,
+  });
+  return newConfig;
+}
+
+export const DoHConfigController = {
+  initComplete: null,
+  _resolveInitComplete: null,
+
+  // This field always contains the current config state, for
+  // consumer use.
+  currentConfig: makeBaseConfigObject(),
+
+  // Loads the client's region via Region.sys.mjs. This might mean waiting
+  // until the region is available.
+  async loadRegion() {
+    await new Promise(resolve => {
+      let homeRegion = lazy.Preferences.get(`${kGlobalPrefBranch}.home-region`);
+      if (homeRegion) {
+        kRegionPrefBranch = `${kGlobalPrefBranch}.${homeRegion.toLowerCase()}`;
+        resolve();
+        return;
+      }
+
+      let updateRegionAndResolve = () => {
+        kRegionPrefBranch = `${kGlobalPrefBranch}.${lazy.Region.home.toLowerCase()}`;
+        lazy.Preferences.set(
+          `${kGlobalPrefBranch}.home-region`,
+          lazy.Region.home
+        );
+        resolve();
+      };
+
+      if (lazy.Region.home) {
+        updateRegionAndResolve();
+        return;
+      }
+
+      Services.obs.addObserver(function obs(sub, top, data) {
+        Services.obs.removeObserver(obs, lazy.Region.REGION_TOPIC);
+        updateRegionAndResolve();
+      }, lazy.Region.REGION_TOPIC);
+    });
+
+    // Finally, reload config.
+    await this.updateFromRemoteSettings();
+  },
+
+  async init() {
+    await this.loadRegion();
+
+    Services.prefs.addObserver(`${kGlobalPrefBranch}.`, this, true);
+
+    gProvidersCollection.on("sync", this.updateFromRemoteSettings);
+    gConfigCollection.on("sync", this.updateFromRemoteSettings);
+
+    this._resolveInitComplete();
+  },
+
+  // Useful for tests to set prior state before init()
+  async _uninit() {
+    await this.initComplete;
+
+    Services.prefs.removeObserver(`${kGlobalPrefBranch}`, this);
+
+    gProvidersCollection.off("sync", this.updateFromRemoteSettings);
+    gConfigCollection.off("sync", this.updateFromRemoteSettings);
+
+    this.initComplete = new Promise(resolve => {
+      this._resolveInitComplete = resolve;
+    });
+  },
+
+  observe(subject, topic, data) {
+    switch (topic) {
+      case kPrefChangedTopic:
+        let allowedPrefs = Object.getOwnPropertyNames(kConfigPrefs).map(
+          k => kConfigPrefs[k]
+        );
+        if (
+          !allowedPrefs.some(pref =>
+            [
+              `${kRegionPrefBranch}.${pref}`,
+              `${kGlobalPrefBranch}.${pref}`,
+            ].includes(data)
+          )
+        ) {
+          break;
+        }
+        this.notifyNewConfig();
+        break;
+    }
+  },
+
+  QueryInterface: ChromeUtils.generateQI([
+    "nsIObserver",
+    "nsISupportsWeakReference",
+  ]),
+
+  // Creates new config object from currently available
+  // Remote Settings values.
+  async updateFromRemoteSettings() {
+    let providers = await gProvidersCollection.get();
+    let config = await gConfigCollection.get();
+
+    let providersById = new Map();
+    providers.forEach(p => providersById.set(p.id, p));
+
+    let configByRegion = new Map();
+    config.forEach(c => {
+      c.id = c.id.toLowerCase();
+      configByRegion.set(c.id, c);
+    });
+
+    let homeRegion = lazy.Preferences.get(`${kGlobalPrefBranch}.home-region`);
+    let localConfig =
+      configByRegion.get(homeRegion?.toLowerCase()) ||
+      configByRegion.get("global");
+
+    // Make a new config object first, mutate it as needed, then synchronously
+    // replace the currentConfig object at the end to ensure atomicity.
+    let newConfig = makeBaseConfigObject();
+
+    if (!localConfig) {
+      DoHConfigController.currentConfig = newConfig;
+      DoHConfigController.notifyNewConfig();
+      return;
+    }
+
+    if (localConfig.rolloutEnabled) {
+      newConfig.enabled = true;
+    }
+
+    let parseProviderList = (list, checkFn) => {
+      let parsedList = [];
+      list?.split(",")?.forEach(p => {
+        p = p.trim();
+        if (!p.length) {
+          return;
+        }
+        p = providersById.get(p);
+        if (!p || (checkFn && !checkFn(p))) {
+          return;
+        }
+        parsedList.push(p);
+      });
+      return parsedList;
+    };
+
+    let regionalProviders = parseProviderList(localConfig.providers);
+    if (regionalProviders?.length) {
+      newConfig.providerList = regionalProviders;
+    }
+
+    if (localConfig.steeringEnabled) {
+      let steeringProviders = parseProviderList(
+        localConfig.steeringProviders,
+        p => p.canonicalName?.length
+      );
+      if (steeringProviders?.length) {
+        newConfig.providerSteering.providerList = steeringProviders;
+        newConfig.providerSteering.enabled = true;
+      }
+    }
+
+    if (localConfig.autoDefaultEnabled) {
+      let defaultProviders = parseProviderList(
+        localConfig.autoDefaultProviders
+      );
+      if (defaultProviders?.length) {
+        newConfig.trrSelection.providerList = defaultProviders;
+        newConfig.trrSelection.enabled = true;
+      }
+    }
+
+    // Finally, update the currentConfig object synchronously.
+    DoHConfigController.currentConfig = newConfig;
+
+    DoHConfigController.notifyNewConfig();
+  },
+
+  kConfigUpdateTopic: "doh-config-updated",
+  notifyNewConfig() {
+    Services.obs.notifyObservers(null, this.kConfigUpdateTopic);
+  },
+};
+
+DoHConfigController.initComplete = new Promise(resolve => {
+  DoHConfigController._resolveInitComplete = resolve;
+});
+DoHConfigController.init();