Add update_verifier for A/B OTA update.

update_verifier checks the integrity of the updated system and vendor
partitions on the first boot post an A/B OTA update. It marks the
current slot as having booted successfully if it passes the verification.

This CL doesn't perform any actual verification work which will be
addressed in follow-up CLs.

Bug: 26039641
Change-Id: Ia5504ed25b799b48b5886c2fc68073a360127f42

Android.mk

@@ -134,4 +134,5 @@ include $(LOCAL_PATH)/minui/Android.mk \
     $(LOCAL_PATH)/edify/Android.mk \
     $(LOCAL_PATH)/uncrypt/Android.mk \
     $(LOCAL_PATH)/updater/Android.mk \
+    $(LOCAL_PATH)/update_verifier/Android.mk \
     $(LOCAL_PATH)/applypatch/Android.mk

update_verifier/Android.mk

@@ -0,0 +1,24 @@
+# Copyright (C) 2015 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.
+
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+
+LOCAL_CLANG := true
+LOCAL_SRC_FILES := update_verifier.cpp
+LOCAL_MODULE := update_verifier
+LOCAL_SHARED_LIBRARIES := libcutils libhardware
+
+include $(BUILD_EXECUTABLE)

update_verifier/update_verifier.cpp

@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2015 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.
+ */
+
+/*
+ * This program verifies the integrity of the partitions after an A/B OTA
+ * update. It gets invoked by init, and will only perform the verification if
+ * it's the first boot post an A/B OTA update.
+ *
+ * It relies on dm-verity to capture any corruption on the partitions being
+ * verified. dm-verity must be in enforcing mode, so that it will reboot the
+ * device on dm-verity failures. When that happens, the bootloader should
+ * mark the slot as unbootable and stops trying. We should never see a device
+ * started in dm-verity logging mode but with isSlotBootable equals to 0.
+ *
+ * The current slot will be marked as having booted successfully if the
+ * verifier reaches the end after the verification.
+ *
+ * TODO: The actual verification part will be added later after we have the
+ * A/B OTA package format in place.
+ */
+
+#include <cutils/klog.h>
+#include <string.h>
+
+#include <hardware/boot_control.h>
+
+#define LOG_TAG       "update_verifier"
+#define INFO(x...)    KLOG_INFO(LOG_TAG, x)
+#define ERROR(x...)   KLOG_ERROR(LOG_TAG, x)
+
+int main(int argc, char** argv) {
+  klog_init();
+  klog_set_level(6);
+  for (int i = 1; i < argc; i++) {
+    INFO("Started with arg %d: %s\n", i, argv[i]);
+  }
+
+  const hw_module_t* hw_module;
+  if (hw_get_module("bootctrl", &hw_module) != 0) {
+    ERROR("Error getting bootctrl module.\n");
+    return -1;
+  }
+
+  boot_control_module_t* module = reinterpret_cast<boot_control_module_t*>(
+      const_cast<hw_module_t*>(hw_module));
+  module->init(module);
+
+  unsigned current_slot = module->getCurrentSlot(module);
+  int bootable = module->isSlotBootable(module, current_slot);
+  INFO("Booting slot %u: isSlotBootable=%d\n", current_slot, bootable);
+
+  if (bootable == 0) {
+    // The current slot has not booted successfully.
+
+    // TODO: Add the actual verification after we have the A/B OTA package
+    // format in place.
+
+    // TODO: Assert the dm-verity mode. Bootloader should never boot a newly
+    // flashed slot (isSlotBootable == 0) with dm-verity logging mode.
+
+    int ret = module->markBootSuccessful(module);
+    if (ret != 0) {
+      ERROR("Error marking booted successfully: %s\n", strerror(-ret));
+      return -1;
+    }
+    INFO("Marked slot %u as booted successfully.\n", current_slot);
+  }
+
+  INFO("Leaving update_verifier.\n");
+  return 0;
+}