init/startup/mount_helper.h

// Copyright 2022 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef INIT_STARTUP_MOUNT_HELPER_H_
#define INIT_STARTUP_MOUNT_HELPER_H_

#include <memory>
#include <stack>
#include <string>
#include <vector>

#include <base/files/file_path.h>
#include <base/values.h>

#include "init/startup/flags.h"
#include "init/startup/platform_impl.h"

namespace startup {

// An enum to specify what type of MountHelper is being used.
enum class MountHelperType {
  kStandardMode,
  kTestMode,
  kFactoryMode,
};

// MountHelper contains the functionality for maintaining the mount stack
// and the mounting and umounting of /var and /home/chronos.
// This is the base class for the MountHelper classes. The pure virtual
// functions are defined within the StandardMountHelper, FactoryMountHelper,
// and StandardMountHelper classes.
class MountHelper {
 public:
  MountHelper(std::unique_ptr<Platform> platform,
              const Flags& flags,
              const base::FilePath& root,
              const base::FilePath& stateful,
              const bool dev_mode);
  virtual ~MountHelper() = default;

  // Add mount to mount stack.
  void RememberMount(const base::FilePath& mount);
  // On failure unmount all saved mount points and repair stateful.
  void CleanupMountsStack(std::vector<base::FilePath>* mnts);
  // Unmounts the incomplete mount setup during the failure path.
  void CleanupMounts(const std::string& msg);
  // Tries to mount, clobbers the stateful partition on failure.
  void MountOrFail(const base::FilePath& source,
                   const base::FilePath& target,
                   const std::string& type,
                   const int32_t& flags,
                   const std::string& data);
  // Sets up a mount stack for testing.
  void SetMountStackForTest(const std::stack<base::FilePath>& mount_stack);
  // Gets the mount stack for testing.
  std::stack<base::FilePath> GetMountStackForTest() { return mount_stack_; }

  // Unmount bind mounts for /var and /home/chronos when encrypted.
  bool UmountVarAndHomeChronosEncrypted();
  // Unmount bind mounts for /var and /home/chronos when unencrypted.
  bool UmountVarAndHomeChronosUnencrypted();
  bool MountVarAndHomeChronosEncrypted();
  bool MountVarAndHomeChronosUnencrypted();
  bool MountVarAndHomeChronos();

  Flags GetFlags();
  base::FilePath GetRoot();
  base::FilePath GetStateful();
  Platform* GetPlatform();

  // Checks for encstateful flag, then calls the appropriate
  // UmountVarAndHomeChronos function.
  bool DoUmountVarAndHomeChronos();

  // Bind mount the /var and /home/chronos mounts. The implementation
  // is different for test images and when in factory mode. It also
  // changes depending on the encrypted stateful USE flag.
  virtual bool DoMountVarAndHomeChronos() = 0;

  // Returns a string representation of the MountHelper derived class
  // used, for test purposes.
  virtual MountHelperType GetMountHelperType() const = 0;

 protected:
  std::unique_ptr<Platform> platform_;
  const startup::Flags flags_;
  const base::FilePath root_;
  const base::FilePath stateful_;
  const bool dev_mode_;
  std::stack<base::FilePath> mount_stack_;
};

}  // namespace startup

#endif  // INIT_STARTUP_MOUNT_HELPER_H_