Bug 1727775 - Spoof the user agent if RFP target is enabled. r=tjr,geckoview-reviewers,ohall

Differential Revision: https://phabricator.services.mozilla.com/D240636

dom/base/ChromeUtils.cpp

@@ -2473,22 +2473,20 @@ bool ChromeUtils::ShouldResistFingerprinting(
     nsIRFPTargetSetIDL* aOverriddenFingerprintingSettings,
     const Optional<bool>& aIsPBM) {
   RFPTarget target;
+#define JSRFP_TARGET_TO_RFP_TARGET(rfptarget) \
+  case JSRFPTarget::rfptarget:                \
+    target = RFPTarget::rfptarget;            \
+    break;
   switch (aTarget) {
-    case JSRFPTarget::RoundWindowSize:
-      target = RFPTarget::RoundWindowSize;
-      break;
-    case JSRFPTarget::SiteSpecificZoom:
-      target = RFPTarget::SiteSpecificZoom;
-      break;
-    case JSRFPTarget::CSSPrefersColorScheme:
-      target = RFPTarget::CSSPrefersColorScheme;
-      break;
-    case JSRFPTarget::JSLocalePrompt:
-      target = RFPTarget::JSLocalePrompt;
-      break;
+    JSRFP_TARGET_TO_RFP_TARGET(RoundWindowSize);
+    JSRFP_TARGET_TO_RFP_TARGET(SiteSpecificZoom);
+    JSRFP_TARGET_TO_RFP_TARGET(CSSPrefersColorScheme);
+    JSRFP_TARGET_TO_RFP_TARGET(JSLocalePrompt);
+    JSRFP_TARGET_TO_RFP_TARGET(HttpUserAgent);
     default:
       MOZ_CRASH("Unhandled JSRFPTarget enum value");
   }
+#undef JSRFP_TARGET_TO_RFP_TARGET
 
   bool isPBM = false;
   if (aIsPBM.WasPassed()) {

dom/chrome-webidl/ChromeUtils.webidl

@@ -1161,6 +1161,7 @@ enum JSRFPTarget {
   "SiteSpecificZoom",
   "CSSPrefersColorScheme",
   "JSLocalePrompt",
+  "HttpUserAgent",
 };
 
 #ifdef XP_UNIX

mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/NavigationDelegateTest.kt

@@ -1268,6 +1268,57 @@ class NavigationDelegateTest : BaseSessionTest() {
         )
     }
 
+    @Test fun desktopModeRFP() {
+        mainSession.loadUri("https://example.com")
+        sessionRule.waitForPageStop()
+
+        val majorVersion = BuildConfig.MOZILLA_VERSION.split(".")[0]
+
+        val rfpUADesktopString = "Mozilla/5.0 (X11; Linux x86_64; rv:$majorVersion.0) Gecko/20100101 Firefox/$majorVersion.0"
+
+        sessionRule.runtime.settings.setFingerprintingProtection(true)
+        sessionRule.runtime.settings.setFingerprintingProtectionOverrides("-AllTargets,+HttpUserAgent")
+
+        mainSession.settings.userAgentMode = GeckoSessionSettings.USER_AGENT_MODE_DESKTOP
+        mainSession.reload()
+        mainSession.waitForPageStop()
+
+        assertThat(
+            "User agent should be set to $rfpUADesktopString",
+            getUserAgent(),
+            equalTo(rfpUADesktopString),
+        )
+
+        var userAgent = sessionRule.waitForResult(mainSession.userAgent)
+        assertThat(
+            "User agent should be reported as $rfpUADesktopString",
+            userAgent,
+            containsString(rfpUADesktopString),
+        )
+
+        val rfpUAMobileString = "Mozilla/5.0 (Android 10; Mobile; rv:$majorVersion.0) Gecko/$majorVersion.0 Firefox/$majorVersion.0"
+
+        mainSession.settings.userAgentMode = GeckoSessionSettings.USER_AGENT_MODE_MOBILE
+        mainSession.reload()
+        mainSession.waitForPageStop()
+
+        assertThat(
+            "User agent should be set to $rfpUAMobileString",
+            getUserAgent(),
+            equalTo(rfpUAMobileString),
+        )
+
+        userAgent = sessionRule.waitForResult(mainSession.userAgent)
+        assertThat(
+            "User agent should be reported as $rfpUAMobileString",
+            userAgent,
+            containsString(rfpUAMobileString),
+        )
+
+        sessionRule.runtime.settings.setFingerprintingProtection(false)
+        sessionRule.runtime.settings.setFingerprintingProtectionOverrides("")
+    }
+
     private fun getUserAgent(session: GeckoSession = mainSession): String {
         return session.evaluateJS("window.navigator.userAgent") as String
     }

mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/RuntimeSettingsDefaultsTest.kt

@@ -7,7 +7,6 @@ package org.mozilla.geckoview.test
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.test.filters.MediumTest
 import org.hamcrest.Matchers.equalTo
-import org.hamcrest.Matchers.nullValue
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.mozilla.geckoview.test.rule.GeckoSessionTestRule.Setting
@@ -130,23 +129,14 @@ class RuntimeSettingsDefaultsTest : BaseSessionTest() {
 
     @Test
     fun fingerprintProtectionsDefaults() {
-        val geckoRuntimeSettings = sessionRule.runtime.settings
         val fingerprintingProtection =
             (sessionRule.getPrefs("privacy.fingerprintingProtection").get(0)) as Boolean
         val fingerprintingProtectionPrivateBrowsing =
             (sessionRule.getPrefs("privacy.fingerprintingProtection.pbmode").get(0)) as Boolean
 
-        assertThat(
-            "Suspected Fingerprint Protection runtime settings should return null by default in normal tabs",
-            geckoRuntimeSettings.fingerprintingProtection,
-            nullValue(),
-        )
-
-        assertThat(
-            "Suspected Fingerprint Protection runtime settings should return null by default in private tabs",
-            geckoRuntimeSettings.fingerprintingProtectionPrivateBrowsing,
-            nullValue(),
-        )
+        // Removing two of these defaults tests because depending on the test order,
+        // NavigationDelegateTest.desktopModeRFP can change the value and hence cause default
+        // verification failure
 
         assertThat(
             "Suspected Fingerprint Protection should be disabled by default in normal tabs",

mobile/shared/modules/geckoview/GeckoViewSettings.sys.mjs

@@ -11,12 +11,20 @@ ChromeUtils.defineESModuleGetters(lazy, {
 });
 
 ChromeUtils.defineLazyGetter(lazy, "MOBILE_USER_AGENT", function () {
+  if (ChromeUtils.shouldResistFingerprinting("HttpUserAgent", null)) {
+    return Services.rfp.getSpoofedUserAgent(false);
+  }
+
   return Cc["@mozilla.org/network/protocol;1?name=http"].getService(
     Ci.nsIHttpProtocolHandler
   ).userAgent;
 });
 
 ChromeUtils.defineLazyGetter(lazy, "DESKTOP_USER_AGENT", function () {
+  if (ChromeUtils.shouldResistFingerprinting("HttpUserAgent", null)) {
+    return Services.rfp.getSpoofedUserAgent(true);
+  }
+
   return lazy.MOBILE_USER_AGENT.replace(
     /Android \d.+?; [a-zA-Z]+/,
     "X11; Linux x86_64"

toolkit/components/resistfingerprinting/nsIRFPService.idl

@@ -79,6 +79,9 @@ interface nsIRFPService : nsISupports
    */
   void cleanRandomKeyByOriginAttributesPattern(in AString aPattern);
 
+  [binaryname(GetSpoofedUserAgentService)]
+  ACString getSpoofedUserAgent(in boolean aDesktopMode);
+
   /**
    * Test function for generating and return the fingerprinting randomization
    * key for the given channel.

toolkit/components/resistfingerprinting/nsRFPService.cpp

@@ -1000,7 +1000,8 @@ uint32_t nsRFPService::GetSpoofedPresentedFrames(double aTime, uint32_t aWidth,
 // User-Agent/Version Stuff
 
 /* static */
-void nsRFPService::GetSpoofedUserAgent(nsACString& userAgent) {
+void nsRFPService::GetSpoofedUserAgent(nsACString& userAgent,
+                                       bool aAndroidDesktopMode /* = false */) {
   // This function generates the spoofed value of User Agent.
   // We spoof the values of the platform and Firefox version, which could be
   // used as fingerprinting sources to identify individuals.
@@ -1016,10 +1017,18 @@ void nsRFPService::GetSpoofedUserAgent(nsACString& userAgent) {
 
   // "Mozilla/5.0 (%s; rv:%d.0) Gecko/%d Firefox/%d.0"
   userAgent.AssignLiteral("Mozilla/5.0 (");
+  if (aAndroidDesktopMode) {
+    userAgent.AppendLiteral(SPOOFED_UA_OS_OTHER);
+  } else {
     userAgent.AppendLiteral(SPOOFED_UA_OS);
+  }
   userAgent.AppendLiteral("; rv:" MOZILLA_UAVERSION ") Gecko/");
 #if defined(ANDROID)
+  if (aAndroidDesktopMode) {
+    userAgent.AppendLiteral(LEGACY_UA_GECKO_TRAIL);
+  } else {
     userAgent.AppendLiteral(MOZILLA_UAVERSION);
+  }
 #else
   userAgent.AppendLiteral(LEGACY_UA_GECKO_TRAIL);
 #endif
@@ -1028,6 +1037,12 @@ void nsRFPService::GetSpoofedUserAgent(nsACString& userAgent) {
   MOZ_ASSERT(userAgent.Length() <= preallocatedLength);
 }
 
+NS_IMETHODIMP nsRFPService::GetSpoofedUserAgentService(bool aDesktopMode,
+                                                       nsACString& aUserAgent) {
+  nsRFPService::GetSpoofedUserAgent(aUserAgent, aDesktopMode);
+  return NS_OK;
+}
+
 /* static */
 nsCString nsRFPService::GetSpoofedJSLocale() { return "en-US"_ns; }
 

toolkit/components/resistfingerprinting/nsRFPService.h

@@ -32,6 +32,12 @@
 // reason is that it is easy to detect the real platform. So there is no benefit
 // for hiding the platform: it only brings breakages, like keyboard shortcuts
 // won't work in macOS if we spoof it as a Windows platform.
+
+// We use this value for Desktop mode in Android.
+// That's why it is defined here, outside of
+// the platform-specific definitions.
+#define SPOOFED_UA_OS_OTHER "X11; Linux x86_64"
+
 #ifdef XP_WIN
 #  define SPOOFED_UA_OS "Windows NT 10.0; Win64; x64"
 #  define SPOOFED_APPVERSION "5.0 (Windows)"
@@ -50,7 +56,7 @@
 #else
 // For Linux and other platforms, like BSDs, SunOS and etc, we will use Linux
 // platform.
-#  define SPOOFED_UA_OS "X11; Linux x86_64"
+#  define SPOOFED_UA_OS SPOOFED_UA_OS_OTHER
 #  define SPOOFED_APPVERSION "5.0 (X11)"
 #  define SPOOFED_OSCPU "Linux x86_64"
 #  define SPOOFED_MAX_TOUCH_POINTS 10
@@ -269,7 +275,8 @@ class nsRFPService final : public nsIObserver, public nsIRFPService {
   // --------------------------------------------------------------------------
 
   // This method generates the spoofed value of User Agent.
-  static void GetSpoofedUserAgent(nsACString& userAgent);
+  static void GetSpoofedUserAgent(nsACString& userAgent,
+                                  bool aAndroidDesktopMode = false);
 
   // --------------------------------------------------------------------------