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/RebootEscrow.cpp b/rebootescrow/aidl/default/RebootEscrow.cpp
new file mode 100644
index 0000000..94d0901
--- /dev/null
+++ b/rebootescrow/aidl/default/RebootEscrow.cpp
@@ -0,0 +1,75 @@
+/*
+ * 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.
+ */
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/unique_fd.h>
+
+#include "HadamardUtils.h"
+#include "rebootescrow-impl/RebootEscrow.h"
+
+namespace aidl {
+namespace android {
+namespace hardware {
+namespace rebootescrow {
+
+using ::android::base::unique_fd;
+
+ndk::ScopedAStatus RebootEscrow::storeKey(const std::vector<int8_t>& kek) {
+ int rawFd = TEMP_FAILURE_RETRY(::open(REBOOT_ESCROW_DEVICE, O_WRONLY | O_NOFOLLOW | O_CLOEXEC));
+ unique_fd fd(rawFd);
+ if (fd.get() < 0) {
+ LOG(WARNING) << "Could not open reboot escrow device";
+ return ndk::ScopedAStatus(AStatus_fromExceptionCode(EX_UNSUPPORTED_OPERATION));
+ }
+
+ std::vector<uint8_t> ukek(kek.begin(), kek.end());
+ auto encoded = hadamard::EncodeKey(ukek);
+
+ if (!::android::base::WriteFully(fd, encoded.data(), encoded.size())) {
+ LOG(WARNING) << "Could not write data fully to character device";
+ return ndk::ScopedAStatus(AStatus_fromExceptionCode(EX_UNSUPPORTED_OPERATION));
+ }
+
+ return ndk::ScopedAStatus::ok();
+}
+
+ndk::ScopedAStatus RebootEscrow::retrieveKey(std::vector<int8_t>* _aidl_return) {
+ int rawFd = TEMP_FAILURE_RETRY(::open(REBOOT_ESCROW_DEVICE, O_RDONLY | O_NOFOLLOW | O_CLOEXEC));
+ unique_fd fd(rawFd);
+ if (fd.get() < 0) {
+ LOG(WARNING) << "Could not open reboot escrow device";
+ return ndk::ScopedAStatus(AStatus_fromExceptionCode(EX_UNSUPPORTED_OPERATION));
+ }
+
+ std::string encodedString;
+ if (!::android::base::ReadFdToString(fd, &encodedString)) {
+ LOG(WARNING) << "Could not read device to string";
+ return ndk::ScopedAStatus(AStatus_fromExceptionCode(EX_UNSUPPORTED_OPERATION));
+ }
+
+ std::vector<uint8_t> encodedBytes(encodedString.begin(), encodedString.end());
+ auto keyBytes = hadamard::DecodeKey(encodedBytes);
+
+ std::vector<int8_t> signedKeyBytes(keyBytes.begin(), keyBytes.end());
+ *_aidl_return = signedKeyBytes;
+ return ndk::ScopedAStatus::ok();
+}
+
+} // namespace rebootescrow
+} // namespace hardware
+} // namespace android
+} // namespace aidl