commit 6faf0265c9b58db2c15b53f6d29025629d52f882
author Yabin Cui <yabinc@google.com> Thu Jun 09 14:09:39 2016 -0700
committer Yabin Cui <yabinc@google.com> Mon Jun 20 18:18:02 2016 -0700
tree fc2e067205a986071615f936e8ff7040e01520f5
parent dc1393d09bcc09ae246cd46b2248d9401605d0f5

Verify wipe package when wiping A/B device in recovery.

To increase the security of wiping A/B devices, let uncrypt write
wipe package in misc partition. Then recovery verifies the wipe
package before wiping the device.

Bug: 29159185

Change-Id: I186691bab1928d3dc036bc5542abd64a81bc2168

uncrypt/bootloader_message_writer.cpp

diff --git a/uncrypt/bootloader_message_writer.cpp b/uncrypt/bootloader_message_writer.cpp
index 3bb106a..42df31e 100644
--- a/uncrypt/bootloader_message_writer.cpp
+++ b/uncrypt/bootloader_message_writer.cpp
@@ -58,7 +58,7 @@
   return record->blk_device;
 }
 
-static bool write_bootloader_message(const bootloader_message& boot, std::string* err) {
+static bool write_misc_partition(const void* p, size_t size, size_t misc_offset, std::string* err) {
   std::string misc_blk_device = get_misc_blk_device(err);
   if (misc_blk_device.empty()) {
     return false;
@@ -69,11 +69,18 @@
                                        strerror(errno));
     return false;
   }
-  if (!android::base::WriteFully(fd.get(), &boot, sizeof(boot))) {
+  if (lseek(fd.get(), static_cast<off_t>(misc_offset), SEEK_SET) !=
+      static_cast<off_t>(misc_offset)) {
+    *err = android::base::StringPrintf("failed to lseek %s: %s", misc_blk_device.c_str(),
+                                       strerror(errno));
+    return false;
+  }
+  if (!android::base::WriteFully(fd.get(), p, size)) {
     *err = android::base::StringPrintf("failed to write %s: %s", misc_blk_device.c_str(),
                                        strerror(errno));
     return false;
   }
+
   // TODO: O_SYNC and fsync duplicates each other?
   if (fsync(fd.get()) == -1) {
     *err = android::base::StringPrintf("failed to fsync %s: %s", misc_blk_device.c_str(),
@@ -83,6 +90,10 @@
   return true;
 }
 
+static bool write_bootloader_message(const bootloader_message& boot, std::string* err) {
+  return write_misc_partition(&boot, sizeof(boot), BOOTLOADER_MESSAGE_OFFSET_IN_MISC, err);
+}
+
 bool clear_bootloader_message(std::string* err) {
   bootloader_message boot = {};
   return write_bootloader_message(boot, err);
@@ -101,6 +112,11 @@
   return write_bootloader_message(boot, err);
 }
 
+bool write_wipe_package(const std::string& package_data, std::string* err) {
+  return write_misc_partition(package_data.data(), package_data.size(),
+                              WIPE_PACKAGE_OFFSET_IN_MISC, err);
+}
+
 extern "C" bool write_bootloader_message(const char* options) {
   std::string err;
   return write_bootloader_message({options}, &err);