Limit enumerateDevices() fingerprinting vector ahead of (and after) g…

…etUserMedia success, to spec.

Updates enumerateDevices() to limit exposure of privacy sensitive
information ahead of actual camera or microphone use.

It also implements the "creating a device info object" algorithm correctly
after getUserMedia success, which only exposes information on cameras or
microphones (but not both) if only one or the other kind has successfully
been used.

Includes the latest privacy improvements to the spec:
- w3c/mediacapture-main#632
- w3c/mediacapture-main#641
- w3c/mediacapture-main#773

This also fixes media.navigator.permission.disabled leaking labels.

Differential Revision: https://phabricator.services.mozilla.com/D100378

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1528042
gecko-commit: 55c6b85b37c1fb8d6d0b6a273e237b4921672743
gecko-reviewers: karlt

mediacapture-streams/MediaDevices-enumerateDevices.https.html

@@ -23,36 +23,71 @@ <h1 class="instructions">Description</h1>
 
 promise_test(async () => {
   assert_not_equals(navigator.mediaDevices.enumerateDevices, undefined, "navigator.mediaDevices.enumerateDevices exists");
-  const deviceList =  await navigator.mediaDevices.enumerateDevices();
-  for (const mediaInfo of deviceList) {
-    assert_not_equals(mediaInfo.kind, undefined, "mediaInfo's kind should exist.");
-    assert_equals(mediaInfo.deviceId, "", "mediaInfo's deviceId should exist and be empty if getUserMedia was never called successfully.");
-    assert_equals(mediaInfo.label, "", "mediaInfo's label should exist and be empty if getUserMedia was never called successfully.");
-    assert_equals(mediaInfo.groupId, "", "mediaInfo's groupId  should exist and be empty if getUserMedia was never called successfully.");
-    assert_in_array(mediaInfo.kind, ["videoinput", "audioinput", "audiooutput"]);
+  const devices = await navigator.mediaDevices.enumerateDevices();
+  for (const {kind, deviceId, label, groupId} of devices) {
+    assert_in_array(kind, ["videoinput", "audioinput", "audiooutput"]);
+    assert_equals(deviceId, "", "deviceId should be empty string if getUserMedia was never called successfully.");
+    assert_equals(label, "", "label should be empty string if getUserMedia was never called successfully.");
+    assert_equals(groupId, "", "groupId should be empty string if getUserMedia was never called successfully.");
   }
-  assert_less_than_equal(deviceList.filter((item) => { return item.kind == "audioinput"; }).length, 1, "there should be zero or one audio input device ");
-  assert_less_than_equal(deviceList.filter((item) => { return item.kind == "videoinput"; }).length, 1, "there should be zero or one video input device ");
-
+  assert_less_than_equal(devices.filter(({kind}) => kind == "audioinput").length,
+                         1, "there should be zero or one audio input device.");
+  assert_less_than_equal(devices.filter(({kind}) => kind == "videoinput").length,
+                         1, "there should be zero or one video input device.");
 }, "mediaDevices.enumerateDevices() is present and working - before capture");
 
-promise_test(async () => {
-  await setMediaPermission("granted", ["microphone"]);
-  await navigator.mediaDevices.getUserMedia({ audio : true });
-  const deviceList =  await navigator.mediaDevices.enumerateDevices();
-  for (const mediaInfo of deviceList) {
-    assert_not_equals(mediaInfo.kind, undefined, "mediaInfo's kind should exist.");
-    assert_not_equals(mediaInfo.deviceId, "", "mediaInfo's deviceId should exist and not be empty.");
-    assert_in_array(mediaInfo.kind, ["videoinput", "audioinput", "audiooutput"]);
+promise_test(async t => {
+  await setMediaPermission("granted");
+  const stream = await navigator.mediaDevices.getUserMedia({ video: true });
+  stream.getTracks()[0].stop();
+
+  const devices = await navigator.mediaDevices.enumerateDevices();
+  const kinds = ["audioinput", "videoinput"];
+  for (const {kind, deviceId} of devices) {
+    assert_in_array(kind, kinds, "camera doesn't expose audiooutput");
+    assert_equals(typeof deviceId, "string", "deviceId is a string.");
+    switch (kind) {
+      case "videoinput":
+        assert_greater_than(deviceId.length, 0, "video deviceId should not be empty.");
+        break;
+      case "audioinput":
+        assert_equals(deviceId.length, 0, "audio deviceId should be empty.");
+        break;
+    }
+  }
+}, "mediaDevices.enumerateDevices() is working - after video capture");
+
+// This test is designed to come after its video counterpart directly above
+promise_test(async t => {
+  const devices1 = await navigator.mediaDevices.enumerateDevices();
+  const stream = await navigator.mediaDevices.getUserMedia({ audio: true });
+  stream.getTracks()[0].stop();
+  const devices = await navigator.mediaDevices.enumerateDevices();
+  assert_equals(devices.filter(({kind}) => kind != "audiooutput").length,
+                devices1.filter(({kind}) => kind != "audiooutput").length,
+                "same number of input devices");
+  const kinds = ["audioinput", "videoinput", "audiooutput"];
+  for (const {kind, deviceId} of devices) {
+    assert_in_array(kind, kinds, "expected kind");
+    assert_equals(typeof deviceId, "string", "deviceId is a string.");
+    switch (kind) {
+      case "videoinput":
+        assert_greater_than(deviceId.length, 0, "video deviceId should not be empty.");
+        break;
+      case "audioinput":
+        assert_greater_than(deviceId.length, 0, "audio deviceId should not be empty.");
+        break;
+    }
   }
-}, "mediaDevices.enumerateDevices() is present and working - after capture");
+}, "mediaDevices.enumerateDevices() is working - after video then audio capture");
 
 promise_test(async () => {
-  const deviceList =  await navigator.mediaDevices.enumerateDevices();
-  for (const mediaInfo of deviceList) {
+  const devices = await navigator.mediaDevices.enumerateDevices();
+  for (const mediaInfo of devices) {
     if (mediaInfo.kind == "audioinput" || mediaInfo.kind == "videoinput") {
+      assert_true("InputDeviceInfo" in window, "InputDeviceInfo exists");
       assert_true(mediaInfo instanceof InputDeviceInfo);
-    } else if ( mediaInfo.kind == "audiooutput" ) {
+    } else if (mediaInfo.kind == "audiooutput") {
       assert_true(mediaInfo instanceof MediaDeviceInfo);
     } else {
       assert_unreached("mediaInfo.kind should be one of 'audioinput', 'videoinput', or 'audiooutput'.")