diff --git a/core/java/android/os/Parcel.java b/core/java/android/os/Parcel.java
index 7425f67e17d2d..575b072732f3b 100644
--- a/core/java/android/os/Parcel.java
+++ b/core/java/android/os/Parcel.java
@@ -599,7 +599,7 @@ public final class Parcel {
      * Flatten an ArrayMap into the parcel at the current dataPosition(),
      * growing dataCapacity() if needed.  The Map keys must be String objects.
      */
-    /* package */ void writeArrayMapInternal(ArrayMap<String,Object> val) {
+    /* package */ void writeArrayMapInternal(ArrayMap<String, Object> val) {
         if (val == null) {
             writeInt(-1);
             return;
@@ -614,7 +614,7 @@ public final class Parcel {
         int startPos;
         for (int i=0; i<N; i++) {
             if (DEBUG_ARRAY_MAP) startPos = dataPosition();
-            writeValue(val.keyAt(i));
+            writeString(val.keyAt(i));
             writeValue(val.valueAt(i));
             if (DEBUG_ARRAY_MAP) Log.d(TAG, "  Write #" + i + " "
                     + (dataPosition()-startPos) + " bytes: key=0x"
@@ -623,6 +623,13 @@ public final class Parcel {
         }
     }
 
+    /**
+     * @hide For testing only.
+     */
+    public void writeArrayMap(ArrayMap<String, Object> val) {
+        writeArrayMapInternal(val);
+    }
+
     /**
      * Flatten a Bundle into the parcel at the current dataPosition(),
      * growing dataCapacity() if needed.
@@ -2321,7 +2328,7 @@ public final class Parcel {
         int startPos;
         while (N > 0) {
             if (DEBUG_ARRAY_MAP) startPos = dataPosition();
-            Object key = readValue(loader);
+            String key = readString();
             Object value = readValue(loader);
             if (DEBUG_ARRAY_MAP) Log.d(TAG, "  Read #" + (N-1) + " "
                     + (dataPosition()-startPos) + " bytes: key=0x"
@@ -2329,6 +2336,7 @@ public final class Parcel {
             outVal.append(key, value);
             N--;
         }
+        outVal.validate();
     }
 
     /* package */ void readArrayMapSafelyInternal(ArrayMap outVal, int N,
@@ -2339,7 +2347,7 @@ public final class Parcel {
             Log.d(TAG, "Reading safely " + N + " ArrayMap entries", here);
         }
         while (N > 0) {
-            Object key = readValue(loader);
+            String key = readString();
             if (DEBUG_ARRAY_MAP) Log.d(TAG, "  Read safe #" + (N-1) + ": key=0x"
                     + (key != null ? key.hashCode() : 0) + " " + key);
             Object value = readValue(loader);
@@ -2348,6 +2356,17 @@ public final class Parcel {
         }
     }
 
+    /**
+     * @hide For testing only.
+     */
+    public void readArrayMap(ArrayMap outVal, ClassLoader loader) {
+        final int N = readInt();
+        if (N < 0) {
+            return;
+        }
+        readArrayMapInternal(outVal, N, loader);
+    }
+
     private void readListInternal(List outVal, int N,
         ClassLoader loader) {
         while (N > 0) {
diff --git a/core/java/android/util/ArrayMap.java b/core/java/android/util/ArrayMap.java
index df1d4cd7047a6..8ea23ba12c5c8 100644
--- a/core/java/android/util/ArrayMap.java
+++ b/core/java/android/util/ArrayMap.java
@@ -493,6 +493,44 @@ public final class ArrayMap<K, V> implements Map<K, V> {
         mArray[index+1] = value;
     }
 
+    /**
+     * The use of the {@link #append} function can result in invalid array maps, in particular
+     * an array map where the same key appears multiple times.  This function verifies that
+     * the array map is valid, throwing IllegalArgumentException if a problem is found.  The
+     * main use for this method is validating an array map after unpacking from an IPC, to
+     * protect against malicious callers.
+     * @hide
+     */
+    public void validate() {
+        final int N = mSize;
+        if (N <= 1) {
+            // There can't be dups.
+            return;
+        }
+        int basehash = mHashes[0];
+        int basei = 0;
+        for (int i=1; i<N; i++) {
+            int hash = mHashes[i];
+            if (hash != basehash) {
+                basehash = hash;
+                basei = i;
+                continue;
+            }
+            // We are in a run of entries with the same hash code.  Go backwards through
+            // the array to see if any keys are the same.
+            final Object cur = mArray[i<<1];
+            for (int j=i-1; j>=basei; j--) {
+                final Object prev = mArray[j<<1];
+                if (cur == prev) {
+                    throw new IllegalArgumentException("Duplicate key in ArrayMap: " + cur);
+                }
+                if (cur != null && prev != null && cur.equals(prev)) {
+                    throw new IllegalArgumentException("Duplicate key in ArrayMap: " + cur);
+                }
+            }
+        }
+    }
+
     /**
      * Perform a {@link #put(Object, Object)} of all key/value pairs in <var>array</var>
      * @param array The array whose contents are to be retrieved.