cros-disks/mount_options.h

// Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CROS_DISKS_MOUNT_OPTIONS_H_
#define CROS_DISKS_MOUNT_OPTIONS_H_

#include <string>
#include <utility>
#include <vector>

#include <base/strings/string_piece.h>

#include "cros-disks/platform.h"

namespace cros_disks {

// A class for holding and manipulating mount options.
class MountOptions {
 public:
  using Flags = unsigned long;  // NOLINT(runtime/int)

  // The bare minimum of flags to be used on any cros-disks mount.
  static constexpr Flags kMountFlags = MS_NODEV | MS_NOEXEC | MS_NOSUID;

  static const char kOptionBind[];
  static const char kOptionDirSync[];
  static const char kOptionFlush[];
  static const char kOptionNoDev[];
  static const char kOptionNoExec[];
  static const char kOptionNoSuid[];
  static const char kOptionNoSymFollow[];
  static const char kOptionReadOnly[];
  static const char kOptionReadWrite[];
  static const char kOptionRemount[];
  static const char kOptionSynchronous[];
  static const char kOptionUtf8[];

  MountOptions();
  ~MountOptions();

  // Allows additional options for particular mount invocations.
  // Some filesystems have required uncommon options. Must be set up before
  // options are initialized.
  void AllowOption(const std::string& option);
  void AllowOptionPrefix(const std::string& prefix);

  // Enforces option to be included regardless of what was provided in the
  // Initialize(). Implicitly allows this option.
  // Useful for options like foo=bar to prevent changing 'bar' to user input.
  void EnforceOption(const std::string& option);

  // Initializes the mount options with a list of option strings.
  //
  // If set_user_and_group_id is set to true, uid and gid options are set
  // if provided.
  //
  // If default_user_id is set to a non-empty value, it is added to the
  // mount options if no uid option is found in the option strings.
  // default_group_id is handled similarly.
  void Initialize(const std::vector<std::string>& options,
                  bool set_user_and_group_id,
                  const std::string& default_user_id,
                  const std::string& default_group_id);

  // Returns true if the read-only option is set.
  bool IsReadOnlyOptionSet() const;

  // Forces the read-only option to be set.
  void SetReadOnlyOption();

  // Converts the mount options into mount flags and data that are used by
  // the mount() library call.
  std::pair<Flags, std::string> ToMountFlagsAndData() const;

  // Converts the mount options into a comma-separated string to be passed to
  // the FUSE mounter program. This filters out the nosymfollow option.
  std::string ToFuseMounterOptions() const;

  // Converts the mount options into a comma-separated string.
  std::string ToString() const;

  // Returns true if |option| has been set.
  bool HasOption(const std::string& option) const;

  const std::vector<std::string>& options() const { return options_; }

 private:
  // Allowed mount options.
  std::vector<std::string> allow_exact_;
  std::vector<std::string> allow_prefix_;
  std::vector<std::string> enforced_options_;

  // List of mount options.
  std::vector<std::string> options_;
};

// Checks if after applying all the "ro and "rw" options
// in order, the resulting mount should be read-only.
bool IsReadOnlyMount(const std::vector<std::string>& options);

// Finds the last value assigned to a parameter named |name|. Returns true if
// found.
bool GetParamValue(const std::vector<std::string>& params,
                   base::StringPiece name,
                   std::string* value);

// Adds a '|name|=|value|' parameter to the container.
void SetParamValue(std::vector<std::string>* params,
                   base::StringPiece name,
                   base::StringPiece value);

}  // namespace cros_disks

#endif  // CROS_DISKS_MOUNT_OPTIONS_H_