1 files changed, 210 insertions, 0 deletions
diff --git a/browser/extensions/webcompat/lib/ua_overrides.js b/browser/extensions/webcompat/lib/ua_overrides.js
new file mode 100644
index 0000000000..2426293f3f
--- /dev/null
+++ b/browser/extensions/webcompat/lib/ua_overrides.js
@@ -0,0 +1,210 @@
+/* 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/. */
+
+"use strict";
+
+/* globals browser, module */
+
+class UAOverrides {
+  constructor(availableOverrides) {
+    this.OVERRIDE_PREF = "perform_ua_overrides";
+
+    this._overridesEnabled = true;
+
+    this._availableOverrides = availableOverrides;
+    this._activeListeners = new Map();
+  }
+
+  bindAboutCompatBroker(broker) {
+    this._aboutCompatBroker = broker;
+  }
+
+  bootup() {
+    browser.aboutConfigPrefs.onPrefChange.addListener(() => {
+      this.checkOverridePref();
+    }, this.OVERRIDE_PREF);
+    this.checkOverridePref();
+  }
+
+  checkOverridePref() {
+    browser.aboutConfigPrefs.getPref(this.OVERRIDE_PREF).then(value => {
+      if (value === undefined) {
+        browser.aboutConfigPrefs.setPref(this.OVERRIDE_PREF, true);
+      } else if (value === false) {
+        this.unregisterUAOverrides();
+      } else {
+        this.registerUAOverrides();
+      }
+    });
+  }
+
+  getAvailableOverrides() {
+    return this._availableOverrides;
+  }
+
+  isEnabled() {
+    return this._overridesEnabled;
+  }
+
+  enableOverride(override) {
+    if (override.active) {
+      return;
+    }
+
+    const { blocks, matches, uaTransformer } = override.config;
+    const listener = details => {
+      // Don't actually override the UA for an experiment if the user is not
+      // part of the experiment (unless they force-enabed the override).
+      if (
+        !override.config.experiment ||
+        override.permanentPrefEnabled === true
+      ) {
+        for (const header of details.requestHeaders) {
+          if (header.name.toLowerCase() === "user-agent") {
+            // Don't override the UA if we're on a mobile device that has the
+            // "Request Desktop Site" mode enabled. The UA for the desktop mode
+            // is set inside Gecko with a simple string replace, so we can use
+            // that as a check, see https://searchfox.org/mozilla-central/rev/89d33e1c3b0a57a9377b4815c2f4b58d933b7c32/mobile/android/chrome/geckoview/GeckoViewSettingsChild.js#23-28
+            let isMobileWithDesktopMode =
+              override.currentPlatform == "android" &&
+              header.value.includes("X11; Linux x86_64");
+
+            if (!isMobileWithDesktopMode) {
+              header.value = uaTransformer(header.value);
+            }
+          }
+        }
+      }
+      return { requestHeaders: details.requestHeaders };
+    };
+
+    browser.webRequest.onBeforeSendHeaders.addListener(
+      listener,
+      { urls: matches },
+      ["blocking", "requestHeaders"]
+    );
+
+    const listeners = { onBeforeSendHeaders: listener };
+    if (blocks) {
+      const blistener = details => {
+        return { cancel: true };
+      };
+
+      browser.webRequest.onBeforeRequest.addListener(
+        blistener,
+        { urls: blocks },
+        ["blocking"]
+      );
+
+      listeners.onBeforeRequest = blistener;
+    }
+    this._activeListeners.set(override, listeners);
+    override.active = true;
+  }
+
+  onOverrideConfigChanged(override) {
+    // Check whether the override should be hidden from about:compat.
+    override.hidden = override.config.hidden;
+
+    // Setting the override's permanent pref overrules whether it is hidden.
+    if (override.permanentPrefEnabled !== undefined) {
+      override.hidden = !override.permanentPrefEnabled;
+    }
+
+    // Also check whether the override should be active.
+    let shouldBeActive = true;
+
+    // Overrides can be force-deactivated by their permanent preference.
+    if (override.permanentPrefEnabled === false) {
+      shouldBeActive = false;
+    }
+
+    // Overrides gated behind an experiment the user is not part of do not
+    // have to be activated, unless they are gathering telemetry, or the
+    // user has force-enabled them with their permanent pref.
+    if (override.config.experiment && override.permanentPrefEnabled !== true) {
+      shouldBeActive = false;
+    }
+
+    if (shouldBeActive) {
+      this.enableOverride(override);
+    } else {
+      this.disableOverride(override);
+    }
+
+    if (this._overridesEnabled) {
+      this._aboutCompatBroker.portsToAboutCompatTabs.broadcast({
+        overridesChanged: this._aboutCompatBroker.filterOverrides(
+          this._availableOverrides
+        ),
+      });
+    }
+  }
+
+  async registerUAOverrides() {
+    const platformMatches = ["all"];
+    let platformInfo = await browser.runtime.getPlatformInfo();
+    platformMatches.push(platformInfo.os == "android" ? "android" : "desktop");
+
+    for (const override of this._availableOverrides) {
+      if (platformMatches.includes(override.platform)) {
+        override.availableOnPlatform = true;
+        override.currentPlatform = platformInfo.os;
+
+        // If there is a specific about:config preference governing
+        // this override, monitor its state.
+        const pref = override.config.permanentPref;
+        override.permanentPrefEnabled =
+          pref && (await browser.aboutConfigPrefs.getPref(pref));
+        if (pref) {
+          const checkOverridePref = () => {
+            browser.aboutConfigPrefs.getPref(pref).then(value => {
+              override.permanentPrefEnabled = value;
+              this.onOverrideConfigChanged(override);
+            });
+          };
+          browser.aboutConfigPrefs.onPrefChange.addListener(
+            checkOverridePref,
+            pref
+          );
+        }
+
+        this.onOverrideConfigChanged(override);
+      }
+    }
+
+    this._overridesEnabled = true;
+    this._aboutCompatBroker.portsToAboutCompatTabs.broadcast({
+      overridesChanged: this._aboutCompatBroker.filterOverrides(
+        this._availableOverrides
+      ),
+    });
+  }
+
+  unregisterUAOverrides() {
+    for (const override of this._availableOverrides) {
+      this.disableOverride(override);
+    }
+
+    this._overridesEnabled = false;
+    this._aboutCompatBroker.portsToAboutCompatTabs.broadcast({
+      overridesChanged: false,
+    });
+  }
+
+  disableOverride(override) {
+    if (!override.active) {
+      return;
+    }
+
+    const listeners = this._activeListeners.get(override);
+    for (const [name, listener] of Object.entries(listeners)) {
+      browser.webRequest[name].removeListener(listener);
+    }
+    override.active = false;
+    this._activeListeners.delete(override);
+  }
+}
+
+module.exports = UAOverrides;