Fix permission check when registering an audio policy

The current checks were allowing public apps to register an audio policy
with an APC mix as intended, but the policy could also have focus
listener and volume controller which are not intended to be used by
public apps.

Test: atest android.media.cts.AudioPlaybackCaptureTest
Bug: 129948989
Change-Id: I97d41ed08faff05e59ae6b495ee62ae11f4a09c1

services/core/java/com/android/server/audio/AudioService.java

@@ -6698,7 +6698,10 @@ public class AudioService extends IAudioService.Stub
             boolean isVolumeController, IMediaProjection projection) {
         AudioSystem.setDynamicPolicyCallback(mDynPolicyCallback);
 
-        if (!isPolicyRegisterAllowed(policyConfig, projection)) {
+        if (!isPolicyRegisterAllowed(policyConfig,
+                                     isFocusPolicy || isTestFocusPolicy || hasFocusListener,
+                                     isVolumeController,
+                                     projection)) {
             Slog.w(TAG, "Permission denied to register audio policy for pid "
                     + Binder.getCallingPid() + " / uid " + Binder.getCallingUid()
                     + ", need MODIFY_AUDIO_ROUTING or MediaProjection that can project audio");
@@ -6739,13 +6742,18 @@ public class AudioService extends IAudioService.Stub
      * as those policy do not modify the audio routing.
      */
     private boolean isPolicyRegisterAllowed(AudioPolicyConfig policyConfig,
-             IMediaProjection projection) {
+                                            boolean hasFocusAccess,
+                                            boolean isVolumeController,
+                                            IMediaProjection projection) {
 
         boolean requireValidProjection = false;
         boolean requireCaptureAudioOrMediaOutputPerm = false;
         boolean requireModifyRouting = false;
 
-        if (policyConfig.getMixes().isEmpty()) {
+        if (hasFocusAccess || isVolumeController) {
+            requireModifyRouting |= true;
+        } else if (policyConfig.getMixes().isEmpty()) {
+            // An empty policy could be used to lock the focus or add mixes later
             requireModifyRouting |= true;
         }
         for (AudioMix mix : policyConfig.getMixes()) {