Add SecretKeyFactory backed by AndroidKeyStore.

This factory provides a way to obtain information about a SecretKey
backed by AndroidKeyStore. The information is provided in a form of an
instance of KeyStoreKeySpec class.

EXAMPLE

SecretKeyFactory factory = SecretKeyFactory.getInstance(
        key.getAlgorithm(), "AndroidKeyStore");
KeyStoreKeySpec keySpec =
    factory.getKeySpec(key, KeyStoreKeySpec.class);

Bug: 18088752
Change-Id: I26c9dd544f80230fe7039501eeb471eaf875452b

keystore/java/android/security/KeymasterUtils.java

@@ -1,7 +1,12 @@
 package android.security;
 
+import android.security.keymaster.KeyCharacteristics;
 import android.security.keymaster.KeymasterDefs;
 
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.List;
+
 /**
  * @hide
  */
@@ -20,4 +25,37 @@ public abstract class KeymasterUtils {
                         KeymasterDefs.getErrorMessage(keymasterErrorCode));
         }
     }
+
+    public static Integer getInt(KeyCharacteristics keyCharacteristics, int tag) {
+        if (keyCharacteristics.hwEnforced.containsTag(tag)) {
+            return keyCharacteristics.hwEnforced.getInt(tag, -1);
+        } else if (keyCharacteristics.swEnforced.containsTag(tag)) {
+            return keyCharacteristics.swEnforced.getInt(tag, -1);
+        } else {
+            return null;
+        }
+    }
+
+    public static List<Integer> getInts(KeyCharacteristics keyCharacteristics, int tag) {
+        List<Integer> result = new ArrayList<Integer>();
+        result.addAll(keyCharacteristics.hwEnforced.getInts(tag));
+        result.addAll(keyCharacteristics.swEnforced.getInts(tag));
+        return result;
+    }
+
+    public static Date getDate(KeyCharacteristics keyCharacteristics, int tag) {
+        Date result = keyCharacteristics.hwEnforced.getDate(tag, null);
+        if (result == null) {
+            result = keyCharacteristics.swEnforced.getDate(tag, null);
+        }
+        return result;
+    }
+
+    public static boolean getBoolean(KeyCharacteristics keyCharacteristics, int tag) {
+        if (keyCharacteristics.hwEnforced.containsTag(tag)) {
+            return keyCharacteristics.hwEnforced.getBoolean(tag, false);
+        } else {
+            return keyCharacteristics.swEnforced.getBoolean(tag, false);
+        }
+    }
 }