Symmetric key generation for AndroidKeyStore.

This currently supports AES and HMAC with SHA-256.

Bug: 18088752
Change-Id: Ife55438cf4129b895295681bb35091cd37eb73fb

keystore/java/android/security/KeymasterUtils.java

@@ -0,0 +1,21 @@
+package android.security;
+
+import android.security.keymaster.KeymasterDefs;
+
+/**
+ * @hide
+ */
+public abstract class KeymasterUtils {
+    private KeymasterUtils() {}
+
+    public static KeymasterException getExceptionForKeymasterError(int keymasterErrorCode) {
+        switch (keymasterErrorCode) {
+            case KeymasterDefs.KM_ERROR_INVALID_AUTHORIZATION_TIMEOUT:
+                // The name of this parameter significantly differs between Keymaster and framework
+                // APIs. Use the framework wording to make life easier for developers.
+                return new KeymasterException("Invalid user authentication validity duration");
+            default:
+                return new KeymasterException(KeymasterDefs.getErrorMessage(keymasterErrorCode));
+        }
+    }
+}