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

rebootescrow/aidl/default/Android.bp

@@ -14,6 +14,47 @@
 // limitations under the License.
 //
 
+cc_library_static {
+    name: "librebootescrowdefaultimpl",
+    vendor: true,
+    shared_libs: [
+        "libbase",
+        "libbinder_ndk",
+        "vintf-rebootescrow-ndk_platform",
+    ],
+    export_include_dirs: ["include"],
+    srcs: [
+        "RebootEscrow.cpp",
+    ],
+    visibility: [
+        ":__subpackages__",
+    ],
+}
+
+cc_binary {
+    name: "android.hardware.rebootescrow-service.default",
+    init_rc: ["rebootescrow-default.rc"],
+    relative_install_path: "hw",
+    vintf_fragments: ["rebootescrow-default.xml"],
+    vendor: true,
+    srcs: [
+        "service.cpp",
+    ],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+    shared_libs: [
+        "libbase",
+        "libbinder_ndk",
+        "vintf-rebootescrow-ndk_platform",
+    ],
+    static_libs: [
+        "libhadamardutils",
+        "librebootescrowdefaultimpl",
+    ],
+}
+
 cc_library_static {
     name: "libhadamardutils",
     vendor_available: true,

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

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

rebootescrow/aidl/default/rebootescrow-default.rc

@@ -0,0 +1,9 @@
+service vendor.rebootescrow-default /vendor/bin/hw/android.hardware.rebootescrow-service.default
+    interface aidl android.hardware.rebootescrow.IRebootEscrow/default
+    class hal
+    user system
+    group system
+
+on boot
+    chmod 770 /dev/access-kregistry
+    chown system system /dev/access-kregistry

rebootescrow/aidl/default/rebootescrow-default.xml

@@ -0,0 +1,6 @@
+<manifest version="1.0" type="device">
+    <hal format="aidl">
+        <name>android.hardware.rebootescrow</name>
+        <fqname>IRebootEscrow/default</fqname>
+    </hal>
+</manifest>

rebootescrow/aidl/default/service.cpp

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.1 (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-2.1
+ *
+ * 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 "rebootescrow-impl/RebootEscrow.h"
+
+#include <android-base/logging.h>
+#include <android/binder_manager.h>
+#include <android/binder_process.h>
+
+using aidl::android::hardware::rebootescrow::RebootEscrow;
+
+int main() {
+    ABinderProcess_setThreadPoolMaxThreadCount(0);
+
+    auto re = ndk::SharedRefBase::make<RebootEscrow>();
+    const std::string instance = std::string() + RebootEscrow::descriptor + "/default";
+    binder_status_t status = AServiceManager_addService(re->asBinder().get(), instance.c_str());
+    CHECK(status == STATUS_OK);
+
+    ABinderProcess_joinThreadPool();
+    return EXIT_FAILURE;
+}