media-device-spoofing.patch

diff --git a/dom/media/MediaDevices.cpp b/dom/media/MediaDevices.cpp
index 067094cb6b..9088f71793 100644
--- a/dom/media/MediaDevices.cpp
+++ b/dom/media/MediaDevices.cpp
@@ -26,6 +26,7 @@
 #include "nsPIDOMWindow.h"
 #include "nsGlobalWindowInner.h"
 #include "nsQueryObject.h"
+#include "MaskConfig.hpp"
 
 namespace mozilla::dom {
 
@@ -329,52 +330,52 @@ RefPtr<MediaDeviceSetRefCnt> MediaDevices::FilterExposedDevices(
     exposed->AppendElement(device);
   }
 
-  if (doc->ShouldResistFingerprinting(RFPTarget::MediaDevices)) {
-    // We expose a single device of each kind.
-    // Legacy mode also achieves the same thing, except for speakers.
-    nsTHashSet<MediaDeviceKind> seenKinds;
+  // Replaces the RFP-based device count spoofing with one that controls the
+  // number of devices exposed.
 
-    for (uint32_t i = 0; i < exposed->Length(); i++) {
-      RefPtr<mozilla::MediaDevice> device = exposed->ElementAt(i);
-      if (seenKinds.Contains(device->mKind)) {
-        exposed->RemoveElementAt(i);
-        i--;
-        continue;
-      }
-      seenKinds.Insert(device->mKind);
-    }
+  if (!MaskConfig::GetBool("mediaDevices:enabled")) {
+    return exposed;
+  }
 
-    // We haven't seen at least one of each kind of device.
-    // Audioinput, Videoinput, Audiooutput.
-    // Insert fake devices.
-    if (seenKinds.Count() != 3) {
-      RefPtr fakeEngine = new MediaEngineFake();
-      RefPtr fakeDevices = new MediaDeviceSetRefCnt();
-      // The order in which we insert the fake devices is important.
-      // Microphone is inserted first, then camera, then speaker.
-      // If we haven't seen a microphone, insert a fake one.
-      if (!seenKinds.Contains(MediaDeviceKind::Audioinput)) {
-        fakeEngine->EnumerateDevices(MediaSourceEnum::Microphone,
-                                     MediaSinkEnum::Other, fakeDevices);
-        exposed->InsertElementAt(0, fakeDevices->LastElement());
-      }
-      // If we haven't seen a camera, insert a fake one.
-      if (!seenKinds.Contains(MediaDeviceKind::Videoinput)) {
-        fakeEngine->EnumerateDevices(MediaSourceEnum::Camera,
-                                     MediaSinkEnum::Other, fakeDevices);
-        exposed->InsertElementAt(1, fakeDevices->LastElement());
-      }
-      // If we haven't seen a speaker, insert a fake one.
-      if (!seenKinds.Contains(MediaDeviceKind::Audiooutput) &&
-          mCanExposeMicrophoneInfo) {
-        RefPtr info = new AudioDeviceInfo(
-            nullptr, u""_ns, u""_ns, u""_ns, CUBEB_DEVICE_TYPE_OUTPUT,
-            CUBEB_DEVICE_STATE_ENABLED, CUBEB_DEVICE_PREF_ALL,
-            CUBEB_DEVICE_FMT_ALL, CUBEB_DEVICE_FMT_S16NE, 2, 44100, 44100,
-            44100, 128, 128);
-        exposed->AppendElement(
-            new MediaDevice(new MediaEngineFake(), info, u""_ns));
-      }
+  uint32_t numMics = MaskConfig::GetUint32("mediaDevices:micros").value_or(3);
+  uint32_t numWebcams =
+      MaskConfig::GetUint32("mediaDevices:webcams").value_or(1);
+  uint32_t numSpeakers =
+      MaskConfig::GetUint32("mediaDevices:speakers").value_or(1);
+
+  // Clear existing devices. We'll add our own
+  exposed->Clear();
+
+  // We haven't seen at least one of each kind of device.
+  // Audioinput, Videoinput, Audiooutput.
+  // Insert fake devices.
+  RefPtr fakeEngine = new MediaEngineFake();
+  RefPtr fakeDevices = new MediaDeviceSetRefCnt();
+  // The order in which we insert the fake devices is important.
+  // Microphone is inserted first, then camera, then speaker
+
+  // Insert fake microphones
+  for (uint32_t i = 0; i < numMics; ++i) {
+    fakeEngine->EnumerateDevices(MediaSourceEnum::Microphone,
+                                 MediaSinkEnum::Other, fakeDevices);
+    exposed->InsertElementAt(0, fakeDevices->LastElement());
+  }
+  // Insert fake cameras
+  for (uint32_t i = 0; i < numWebcams; ++i) {
+    fakeEngine->EnumerateDevices(MediaSourceEnum::Camera, MediaSinkEnum::Other,
+                                 fakeDevices);
+    exposed->InsertElementAt(1, fakeDevices->LastElement());
+  }
+  // Insert fake speakers (this is only accessed if the site has permission)
+  if (mCanExposeMicrophoneInfo) {
+    for (uint32_t i = 0; i < numSpeakers; ++i) {
+      RefPtr info = new AudioDeviceInfo(
+          nullptr, u""_ns, u""_ns, u""_ns, CUBEB_DEVICE_TYPE_OUTPUT,
+          CUBEB_DEVICE_STATE_ENABLED, CUBEB_DEVICE_PREF_ALL,
+          CUBEB_DEVICE_FMT_ALL, CUBEB_DEVICE_FMT_S16NE, 2, 44100, 44100, 44100,
+          128, 128);
+      exposed->AppendElement(
+          new MediaDevice(new MediaEngineFake(), info, u""_ns));
     }
   }