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

3 files changed, 37 insertions, 3 deletions

diff --git a/uncrypt/bootloader_message_writer.cpp b/uncrypt/bootloader_message_writer.cpp
index 3bb106aa..42df31ef 100644
--- a/uncrypt/bootloader_message_writer.cpp
+++ b/uncrypt/bootloader_message_writer.cpp
@@ -58,7 +58,7 @@ static std::string get_misc_blk_device(std::string* err) {
   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 @@ static bool write_bootloader_message(const bootloader_message& boot, std::string
                                        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 @@ static bool write_bootloader_message(const bootloader_message& boot, std::string
   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 @@ bool write_bootloader_message(const std::vector<std::string>& options, std::stri
   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);
diff --git a/uncrypt/include/bootloader_message_writer.h b/uncrypt/include/bootloader_message_writer.h
index e0ca3f44..1344bc83 100644
--- a/uncrypt/include/bootloader_message_writer.h
+++ b/uncrypt/include/bootloader_message_writer.h
@@ -24,6 +24,7 @@
 bool clear_bootloader_message(std::string* err);
 
 bool write_bootloader_message(const std::vector<std::string>& options, std::string* err);
+bool write_wipe_package(const std::string& package_data, std::string* err);
 
 #else
 #include <stdbool.h>
diff --git a/uncrypt/uncrypt.cpp b/uncrypt/uncrypt.cpp
index d7105a01..f62d1327 100644
--- a/uncrypt/uncrypt.cpp
+++ b/uncrypt/uncrypt.cpp
@@ -503,14 +503,31 @@ static bool setup_bcb(const int socket) {
         return false;
     }
     ALOGI("  received command: [%s] (%zu)", content.c_str(), content.size());
+    std::vector<std::string> options = android::base::Split(content, "\n");
+    std::string wipe_package;
+    for (auto& option : options) {
+        if (android::base::StartsWith(option, "--wipe_package=")) {
+            std::string path = option.substr(strlen("--wipe_package="));
+            if (!android::base::ReadFileToString(path, &wipe_package)) {
+                ALOGE("failed to read %s: %s", path.c_str(), strerror(errno));
+                return false;
+            }
+            option = android::base::StringPrintf("--wipe_package_size=%zu", wipe_package.size());
+        }
+    }
 
     // c8. setup the bcb command
     std::string err;
-    if (!write_bootloader_message({content}, &err)) {
+    if (!write_bootloader_message(options, &err)) {
         ALOGE("failed to set bootloader message: %s", err.c_str());
         write_status_to_socket(-1, socket);
         return false;
     }
+    if (!wipe_package.empty() && !write_wipe_package(wipe_package, &err)) {
+        ALOGE("failed to set wipe package: %s", err.c_str());
+        write_status_to_socket(-1, socket);
+        return false;
+    }
     // c10. send "100" status
     write_status_to_socket(100, socket);
     return true;