Validate package name passed to setApplicationRestrictions. (Reland)

This adds validation that the package name passed to
setApplicationRestrictions is in the correct format. This will avoid
an issue where a path could be entered resulting in a file being
written to an unexpected place.

Bug: 239701237
Merged-In: I1ab2b7228470f10ec26fe3a608ae540cfc9e9a96
Change-Id: I56c2fc14f906cdad80181ab577e2ebc276c151c1

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

@@ -88,6 +88,7 @@ import android.stats.devicepolicy.DevicePolicyEnums;
 import android.util.ArrayMap;
 import android.util.ArraySet;
 import android.util.AtomicFile;
+import android.util.EventLog;
 import android.util.IndentingPrintWriter;
 import android.util.IntArray;
 import android.util.Slog;
@@ -4499,6 +4500,13 @@ public class UserManagerService extends IUserManager.Stub {
     public void setApplicationRestrictions(String packageName, Bundle restrictions,
             @UserIdInt int userId) {
         checkSystemOrRoot("set application restrictions");
+        String validationResult = validateName(packageName);
+        if (validationResult != null) {
+            if (packageName.contains("../")) {
+                EventLog.writeEvent(0x534e4554, "239701237", -1, "");
+            }
+            throw new IllegalArgumentException("Invalid package name: " + validationResult);
+        }
         if (restrictions != null) {
             restrictions.setDefusable(true);
         }
@@ -4525,6 +4533,39 @@ public class UserManagerService extends IUserManager.Stub {
         mContext.sendBroadcastAsUser(changeIntent, UserHandle.of(userId));
     }
 
+    /**
+     * Check if the given name is valid.
+     *
+     * Note: the logic is taken from FrameworkParsingPackageUtils in master, edited to remove
+     * unnecessary parts. Copied here for a security fix.
+     *
+     * @param name The name to check.
+     * @return null if it's valid, error message if not
+     */
+    @VisibleForTesting
+    static String validateName(String name) {
+        final int n = name.length();
+        boolean front = true;
+        for (int i = 0; i < n; i++) {
+            final char c = name.charAt(i);
+            if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) {
+                front = false;
+                continue;
+            }
+            if (!front) {
+                if ((c >= '0' && c <= '9') || c == '_') {
+                    continue;
+                }
+                if (c == '.') {
+                    front = true;
+                    continue;
+                }
+            }
+            return "bad character '" + c + "'";
+        }
+        return null;
+    }
+
     private int getUidForPackage(String packageName) {
         final long ident = Binder.clearCallingIdentity();
         try {