Resume on Reboot default implementation

A default implementation of the RebootEscrow HAL which relies on RAM
retention to keep a key around during a reboot to apply an OTA. This
should work on devices that use a "warm reboot" and most likely will
work on devices that use a "cold reboot" as well.

DRAM will retain information for several seconds depending on the
temperature and other factors. This is enough to survive a reboot. With
the Hadamard code used in this change for error recovery, many errors
can be recovered.

Bug: 63928581
Test: make
Test: atest VtsHalRebootEscrowTargetTest
Change-Id: Ib8db7888d64fee8d827d7c06892b9a1f2af87add
diff --git a/rebootescrow/aidl/default/include/rebootescrow-impl/RebootEscrow.h b/rebootescrow/aidl/default/include/rebootescrow-impl/RebootEscrow.h
new file mode 100644
index 0000000..1ed7397
--- /dev/null
+++ b/rebootescrow/aidl/default/include/rebootescrow-impl/RebootEscrow.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+
+#pragma once
+
+#include <aidl/android/hardware/rebootescrow/BnRebootEscrow.h>
+
+namespace aidl {
+namespace android {
+namespace hardware {
+namespace rebootescrow {
+
+static const char* REBOOT_ESCROW_DEVICE = "/dev/access-kregistry";
+
+class RebootEscrow : public BnRebootEscrow {
+    ndk::ScopedAStatus storeKey(const std::vector<int8_t>& kek) override;
+    ndk::ScopedAStatus retrieveKey(std::vector<int8_t>* _aidl_return) override;
+};
+
+}  // namespace rebootescrow
+}  // namespace hardware
+}  // namespace android
+}  // namespace aidl