AndroidKeyStore: Add encrypted flag

Add the encrypted flag for the KeyPairGenerator and the KeyStore so that
applications can choose to allow entries when there is no lockscreen.

Bug: 8122243
Change-Id: Ia802afe965f2377ad3f282dab8c512388c705850

keystore/java/android/security/AndroidKeyStoreParameter.java

@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.security;
+
+import android.content.Context;
+import android.security.AndroidKeyPairGeneratorSpec.Builder;
+
+import java.security.KeyPairGenerator;
+import java.security.PrivateKey;
+import java.security.KeyStore.ProtectionParameter;
+import java.security.cert.Certificate;
+
+/**
+ * This provides the optional parameters that can be specified for
+ * {@code KeyStore} entries that work with <a href="{@docRoot}
+ * guide/topics/security/keystore.html">Android KeyStore facility</a>. The
+ * Android KeyStore facility is accessed through a
+ * {@link java.security.KeyStore} API using the {@code AndroidKeyStore}
+ * provider. The {@code context} passed in may be used to pop up some UI to ask
+ * the user to unlock or initialize the Android KeyStore facility.
+ * <p>
+ * Any entries placed in the {@code KeyStore} may be retrieved later. Note that
+ * there is only one logical instance of the {@code KeyStore} per application
+ * UID so apps using the {@code sharedUid} facility will also share a
+ * {@code KeyStore}.
+ * <p>
+ * Keys may be generated using the {@link KeyPairGenerator} facility with a
+ * {@link AndroidKeyPairGeneratorSpec} to specify the entry's {@code alias}. A
+ * self-signed X.509 certificate will be attached to generated entries, but that
+ * may be replaced at a later time by a certificate signed by a real Certificate
+ * Authority.
+ */
+public final class AndroidKeyStoreParameter implements ProtectionParameter {
+    private int mFlags;
+
+    private AndroidKeyStoreParameter(int flags) {
+        mFlags = flags;
+    }
+
+    /**
+     * @hide
+     */
+    public int getFlags() {
+        return mFlags;
+    }
+
+    /**
+     * Returns {@code true} if this parameter requires entries to be encrypted
+     * on the disk.
+     */
+    public boolean isEncryptionRequired() {
+        return (mFlags & KeyStore.FLAG_ENCRYPTED) != 0;
+    }
+
+    /**
+     * Builder class for {@link AndroidKeyStoreParameter} objects.
+     * <p>
+     * This will build protection parameters for use with the <a
+     * href="{@docRoot} guide/topics/security/keystore.html">Android KeyStore
+     * facility</a>.
+     * <p>
+     * This can be used to require that KeyStore entries be stored encrypted.
+     * <p>
+     * Example:
+     *
+     * <pre class="prettyprint">
+     * AndroidKeyStoreParameter params =
+     *         new AndroidKeyStoreParameter.Builder(mContext).setEncryptionRequired().build();
+     * </pre>
+     */
+    public final static class Builder {
+        private int mFlags;
+
+        /**
+         * Creates a new instance of the {@code Builder} with the given
+         * {@code context}. The {@code context} passed in may be used to pop up
+         * some UI to ask the user to unlock or initialize the Android KeyStore
+         * facility.
+         */
+        public Builder(Context context) {
+            if (context == null) {
+                throw new NullPointerException("context == null");
+            }
+
+            // Context is currently not used, but will be in the future.
+        }
+
+        /**
+         * Indicates that this key must be encrypted at rest on storage. Note
+         * that enabling this will require that the user enable a strong lock
+         * screen (e.g., PIN, password) before creating or using the generated
+         * key is successful.
+         */
+        public Builder setEncryptionRequired() {
+            mFlags |= KeyStore.FLAG_ENCRYPTED;
+            return this;
+        }
+
+        /**
+         * Builds the instance of the {@code AndroidKeyPairGeneratorSpec}.
+         *
+         * @throws IllegalArgumentException if a required field is missing
+         * @return built instance of {@code AndroidKeyPairGeneratorSpec}
+         */
+        public AndroidKeyStoreParameter build() {
+            return new AndroidKeyStoreParameter(mFlags);
+        }
+    }
+}