Allow application to inspect query-ability of other package

This CL creates a new API PackageManager#mayPackageQuery for
applications that share details about other applications to
determine if those details should be withheld from callers
that do not otherwise have visibility of them.

Bug: 145916881
Test: atest AppEnumerationTests
Change-Id: I2dfba1169bce3d9fa88a75c92a22f53e1efe01b5

core/api/current.txt

@@ -12631,6 +12631,7 @@ package android.content.pm {
     method public boolean isPackageSuspended();
     method @CheckResult public abstract boolean isPermissionRevokedByPolicy(@NonNull String, @NonNull String);
     method public abstract boolean isSafeMode();
+    method public boolean mayPackageQuery(@NonNull String, @NonNull String) throws android.content.pm.PackageManager.NameNotFoundException;
     method @NonNull public java.util.List<android.content.pm.PackageManager.Property> queryActivityProperty(@NonNull String);
     method @NonNull public java.util.List<android.content.pm.PackageManager.Property> queryApplicationProperty(@NonNull String);
     method @NonNull public abstract java.util.List<android.content.pm.ResolveInfo> queryBroadcastReceivers(@NonNull android.content.Intent, int);

core/java/android/app/ApplicationPackageManager.java

@@ -3575,4 +3575,19 @@ public class ApplicationPackageManager extends PackageManager {
             throw e.rethrowAsRuntimeException();
         }
     }
+
+    @Override
+    public boolean mayPackageQuery(@NonNull String sourcePackageName,
+            @NonNull String targetPackageName) throws NameNotFoundException {
+        Objects.requireNonNull(sourcePackageName);
+        Objects.requireNonNull(targetPackageName);
+        try {
+            return mPM.mayPackageQuery(sourcePackageName, targetPackageName, getUserId());
+        } catch (ParcelableException e) {
+            e.maybeRethrow(PackageManager.NameNotFoundException.class);
+            throw new RuntimeException(e);
+        } catch (RemoteException re) {
+            throw re.rethrowAsRuntimeException();
+        }
+    }
 }

core/java/android/content/pm/IPackageManager.aidl

@@ -818,4 +818,6 @@ interface IPackageManager {
     ParceledListSlice queryProperty(String propertyName, int componentType);
 
     void setKeepUninstalledPackages(in List<String> packageList);
+
+    boolean mayPackageQuery(String sourcePackageName, String targetPackageName, int userId);
 }

core/java/android/content/pm/PackageManager.java

@@ -9329,6 +9329,31 @@ public abstract class PackageManager {
                 "qeuryServiceProperty not implemented in subclass");
     }
 
+    /**
+     * Returns {@code true} if the source package is able to query for details about the
+     * target package. Applications that share details about other applications should
+     * use this API to determine if those details should be withheld from callers that
+     * do not otherwise have visibility of them.
+     * <p>
+     * Note: The caller must be able to query for details about the source and target
+     * package. A {@link NameNotFoundException} is thrown if it isn't.
+     *
+     * @param sourcePackageName The source package that would receive details about the
+     *                          target package.
+     * @param targetPackageName The target package whose details would be shared with the
+     *                          source package.
+     * @return {@code true} if the source package is able to query for details about the
+     * target package.
+     * @throws NameNotFoundException if either a given package can not be found on the
+     * system, or if the caller is not able to query for details about the source or
+     * target package.
+     */
+    public boolean mayPackageQuery(@NonNull String sourcePackageName,
+            @NonNull String targetPackageName) throws NameNotFoundException {
+        throw new UnsupportedOperationException(
+                "mayPackageQuery not implemented in subclass");
+    }
+
     /**
      * Grants implicit visibility of the package that provides an authority to a querying UID.
      *

services/core/java/com/android/server/pm/PackageManagerService.java

@@ -23388,6 +23388,37 @@ public class PackageManagerService extends IPackageManager.Stub
         return new IntentSender(target);
     }
 
+    @Override
+    public boolean mayPackageQuery(String sourcePackageName, String targetPackageName, int userId) {
+        if (!mUserManager.exists(userId)) return false;
+        final int callingUid = Binder.getCallingUid();
+        enforceCrossUserPermission(callingUid, userId, false /*requireFullPermission*/,
+                false /*checkShell*/, "may package query");
+        synchronized (mLock) {
+            final PackageSetting sourceSetting = getPackageSetting(sourcePackageName);
+            final PackageSetting targetSetting = getPackageSetting(targetPackageName);
+            if (sourceSetting == null || targetSetting == null) {
+                throw new ParcelableException(new PackageManager.NameNotFoundException("Package(s) "
+                        + (sourceSetting == null ? sourcePackageName + " " : "")
+                        + (targetSetting == null ? targetPackageName + " " : "")
+                        + "not found."));
+            }
+            final boolean filterSource =
+                    shouldFilterApplicationLocked(sourceSetting, callingUid, userId);
+            final boolean filterTarget =
+                    shouldFilterApplicationLocked(targetSetting, callingUid, userId);
+            // The caller must have visibility of the both packages
+            if (filterSource || filterTarget) {
+                throw new ParcelableException(new PackageManager.NameNotFoundException("Package(s) "
+                        + (filterSource ? sourcePackageName + " " : "")
+                        + (filterTarget ? targetPackageName + " " : "")
+                        + "not found."));
+            }
+            final int sourcePackageUid = UserHandle.getUid(userId, sourceSetting.appId);
+            return !shouldFilterApplicationLocked(targetSetting, sourcePackageUid, userId);
+        }
+    }
+
     private static class TempUserState {
         public final int enabledState;
         @Nullable