Add WifiKeystore to allow Wifi framework access legacykeystore

Add the WifiKeystore API for Wifi framework in mainline module,
to access the legacy keystore for Wifi private key blobs.

Bug: 205764502
Test: adb shell cmd wifi keystore
Change-Id: Ibe3f3d5611c8de26c2aa37b3b9dee49351cbe3c5

core/api/module-lib-current.txt

@@ -296,6 +296,17 @@ package android.net.netstats {
 
 }
 
+package android.net.wifi {
+
+  public final class WifiKeystore {
+    method @NonNull public static byte[] get(@NonNull String);
+    method @NonNull public static String[] list(@NonNull String);
+    method public static boolean put(@NonNull String, @NonNull byte[]);
+    method public static boolean remove(@NonNull String);
+  }
+
+}
+
 package android.os {
 
   public class ArtModuleServiceManager {

wifi/java/src/android/net/wifi/WifiKeystore.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright (C) 2022 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.net.wifi;
+
+import android.annotation.NonNull;
+import android.annotation.SystemApi;
+import android.os.Process;
+import android.os.ServiceManager;
+import android.os.ServiceSpecificException;
+import android.security.legacykeystore.ILegacyKeystore;
+import android.util.Log;
+
+/**
+ * @hide This class allows wifi framework to store and access wifi certificate blobs.
+ */
+@SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
+public final class WifiKeystore {
+    private static final String TAG = "WifiKeystore";
+    private static final String LEGACY_KEYSTORE_SERVICE_NAME = "android.security.legacykeystore";
+
+    private static ILegacyKeystore getService() {
+        return ILegacyKeystore.Stub.asInterface(
+                ServiceManager.checkService(LEGACY_KEYSTORE_SERVICE_NAME));
+    }
+
+    /** @hide */
+    WifiKeystore() {
+    }
+
+    /**
+     * Stores the blob under the alias in the keystore database. Existing blobs by the
+     * same name will be replaced.
+     * @param alias The name of the blob
+     * @param blob The blob.
+     * @return true if the blob was successfully added. False otherwise.
+     * @hide
+     */
+    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
+    public static boolean put(@NonNull String alias, @NonNull byte[] blob) {
+        try {
+            Log.i(TAG, "put blob. alias " + alias);
+            getService().put(alias, Process.WIFI_UID, blob);
+            return true;
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to put blob.", e);
+            return false;
+        }
+    }
+
+    /**
+     * Retrieves a blob by the name alias from the blob database.
+     * @param alias Name of the blob to retrieve.
+     * @return The unstructured blob, that is the blob that was stored using
+     *         {@link android.net.wifi.WifiKeystore#put}.
+     *         Returns null if no blob was found.
+     * @hide
+     */
+    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
+    public static @NonNull byte[] get(@NonNull String alias) {
+        try {
+            Log.i(TAG, "get blob. alias " + alias);
+            return getService().get(alias, Process.WIFI_UID);
+        } catch (ServiceSpecificException e) {
+            if (e.errorCode != ILegacyKeystore.ERROR_ENTRY_NOT_FOUND) {
+                Log.e(TAG, "Failed to get blob.", e);
+            }
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to get blob.", e);
+        }
+        return null;
+    }
+
+    /**
+     * Removes a blob by the name alias from the database.
+     * @param alias Name of the blob to be removed.
+     * @return True if a blob was removed. False if no such blob was found.
+     * @hide
+     */
+    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
+    public static boolean remove(@NonNull String alias) {
+        try {
+            getService().remove(alias, Process.WIFI_UID);
+            return true;
+        } catch (ServiceSpecificException e) {
+            if (e.errorCode != ILegacyKeystore.ERROR_ENTRY_NOT_FOUND) {
+                Log.e(TAG, "Failed to remove blob.", e);
+            }
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to remove blob.", e);
+        }
+        return false;
+    }
+
+    /**
+     * Lists the blobs stored in the database.
+     * @return An array of strings representing the aliases stored in the database.
+     *         The return value may be empty but never null.
+     * @hide
+     */
+    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
+    public static @NonNull String[] list(@NonNull String prefix) {
+        try {
+            final String[] aliases = getService().list(prefix, Process.WIFI_UID);
+            for (int i = 0; i < aliases.length; ++i) {
+                aliases[i] = aliases[i].substring(prefix.length());
+            }
+            return aliases;
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to list blobs.", e);
+        }
+        return new String[0];
+    }
+}