// Copyright 2018 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.

#include "cryptohome/mount_encrypted/encrypted_fs.h"

#include <fcntl.h>
#include <grp.h>
#include <memory>
#include <pwd.h>
#include <string.h>
#include <sys/mount.h>
#include <sys/statvfs.h>
#include <sys/types.h>

#include <string>

#include <base/compiler_specific.h>
#include <base/files/file_util.h>
#include <base/strings/string_number_conversions.h>
#include <brillo/process/process.h>
#include <brillo/secure_blob.h>

#include "cryptohome/cryptolib.h"
#include "cryptohome/mount_encrypted/mount_encrypted.h"
#include "cryptohome/storage/encrypted_container/backing_device.h"
#include "cryptohome/storage/encrypted_container/encrypted_container.h"
#include "cryptohome/storage/encrypted_container/encrypted_container_factory.h"
#include "cryptohome/storage/encrypted_container/filesystem_key.h"

namespace mount_encrypted {

namespace {

constexpr char kEncryptedFSType[] = "ext4";
constexpr char kCryptDevName[] = "encstateful";
constexpr char kDevMapperPath[] = "/dev/mapper";
constexpr char kDumpe2fsLogPath[] = "/run/mount_encrypted/dumpe2fs.log";
constexpr char kProcDirtyExpirePath[] = "/proc/sys/vm/dirty_expire_centisecs";
constexpr float kSizePercent = 0.3;
constexpr uint64_t kExt4BlockSize = 4096;
constexpr uint64_t kExt4MinBytes = 16 * 1024 * 1024;
constexpr unsigned int kResizeStepSeconds = 2;
constexpr uint64_t kExt4ResizeBlocks = 32768 * 10;
// Block size is 4k => Minimum free space available to try resizing is 400MB.
constexpr int64_t kMinBlocksAvailForResize = 102400;
constexpr char kExt4ExtendedOptions[] = "discard,lazy_itable_init";
constexpr char kDmCryptDefaultCipher[] = "aes-cbc-essiv:sha256";

bool CheckBind(cryptohome::Platform* platform, const BindMount& bind) {
  uid_t user;
  gid_t group;

  if (platform->Access(bind.src, R_OK) &&
      !platform->CreateDirectory(bind.src)) {
    PLOG(ERROR) << "mkdir " << bind.src;
    return false;
  }

  if (platform->Access(bind.dst, R_OK) &&
      !(platform->CreateDirectory(bind.dst) &&
        platform->SetPermissions(bind.dst, bind.mode))) {
    PLOG(ERROR) << "mkdir " << bind.dst;
    return false;
  }

  if (!platform->GetUserId(bind.owner, &user, &group)) {
    PLOG(ERROR) << "getpwnam" << bind.owner;
    return false;
  }

  // Destination may be on read-only filesystem, so skip tweaks.
  // Must do explicit chmod since mkdir()'s mode respects umask.
  if (!platform->SetPermissions(bind.src, bind.mode)) {
    PLOG(ERROR) << "chmod " << bind.src;
    return false;
  }
  if (!platform->SetOwnership(bind.src, user, group, true)) {
    PLOG(ERROR) << "chown " << bind.src;
    return false;
  }

  return true;
}

// TODO(sarthakkukreti): Evaulate resizing: it is a no-op on new encrypted
// stateful setups and would slow down boot once for legacy devices on update,
// as long as we do not iteratively resize.
// Spawns a filesystem resizing process and waits for it to finish.
void SpawnResizer(cryptohome::Platform* platform,
                  const base::FilePath& device,
                  uint64_t blocks,
                  uint64_t blocks_max) {
  // Ignore resizing if we know the filesystem was built to max size.
  if (blocks >= blocks_max) {
    PLOG(ERROR) << " Resizing aborted";
    return;
  }

  // TODO(keescook): Read superblock to find out the current size of
  // the filesystem (since statvfs does not report the correct value).
  // For now, instead of doing multi-step resizing, just resize to the
  // full size of the block device in one step.
  blocks = blocks_max;

  LOG(INFO) << "Resizing started in " << kResizeStepSeconds << " second steps.";

  do {
    blocks += kExt4ResizeBlocks;

    if (blocks > blocks_max)
      blocks = blocks_max;

    // Run the resizing function. For a fresh setup, the resize should be
    // a no-op, the only case where this might be slow is legacy devices which
    // have a smaller encrypted stateful partition.
    platform->ResizeFilesystem(device, blocks);
  } while (blocks < blocks_max);

  LOG(INFO) << "Resizing done.";
  return;
}

std::string GetMountOpts() {
  // Use vm.dirty_expire_centisecs / 100 as the commit interval.
  std::string dirty_expire;
  uint64_t dirty_expire_centisecs;
  uint64_t commit_interval = 600;

  if (base::ReadFileToString(base::FilePath(kProcDirtyExpirePath),
                             &dirty_expire) &&
      base::StringToUint64(dirty_expire, &dirty_expire_centisecs)) {
    LOG(INFO) << "Using vm.dirty_expire_centisecs/100 as the commit interval";

    // Keep commit interval as 5 seconds (default for ext4) for smaller
    // values of dirty_expire_centisecs.
    if (dirty_expire_centisecs < 600)
      commit_interval = 5;
    else
      commit_interval = dirty_expire_centisecs / 100;
  }
  return "discard,commit=" + std::to_string(commit_interval);
}

std::vector<std::string> BuildExt4FormatOpts(uint64_t block_bytes,
                                             uint64_t blocks_min,
                                             uint64_t blocks_max) {
  return {"-T", "default",
          "-b", std::to_string(block_bytes),
          "-m", "0",
          "-O", "^huge_file,^flex_bg",
          "-E", kExt4ExtendedOptions};
}

void CheckSparseFileSize(const base::FilePath& sparse_file, int64_t file_size) {
  base::File file(sparse_file, base::File::FLAG_OPEN | base::File::FLAG_WRITE);

  if (file.IsValid() && file.GetLength() < file_size) {
    LOG(INFO) << "Expanding underlying sparse file to " << file_size;
    file.SetLength(file_size);
  }
}

void Dumpe2fs(const base::FilePath& device_path) {
  brillo::ProcessImpl dumpe2fs;
  dumpe2fs.AddArg("/sbin/dumpe2fs");
  dumpe2fs.AddArg("-fh");
  dumpe2fs.AddArg(device_path.value());
  dumpe2fs.RedirectOutput(kDumpe2fsLogPath);

  dumpe2fs.Run();
}

}  // namespace

EncryptedFs::EncryptedFs(
    const base::FilePath& rootdir,
    uint64_t fs_size,
    const std::string& dmcrypt_name,
    std::unique_ptr<cryptohome::EncryptedContainer> container,
    cryptohome::Platform* platform,
    brillo::DeviceMapper* device_mapper)
    : rootdir_(rootdir),
      fs_size_(fs_size),
      dmcrypt_name_(dmcrypt_name),
      stateful_mount_(rootdir_.Append(STATEFUL_MNT)),
      block_path_(stateful_mount_.Append("encrypted.block")),
      dmcrypt_dev_(base::FilePath(kDevMapperPath).Append(dmcrypt_name_)),
      encrypted_mount_(rootdir_.Append(ENCRYPTED_MNT)),
      platform_(platform),
      device_mapper_(device_mapper),
      container_(std::move(container)),
      bind_mounts_({{rootdir_.Append(ENCRYPTED_MNT "/var"),
                     rootdir_.Append("var"), "root", "root",
                     S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH, false},
                    {rootdir_.Append(ENCRYPTED_MNT "/chronos"),
                     rootdir_.Append("home/chronos"), "chronos", "chronos",
                     S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH, true}}) {}

// static
std::unique_ptr<EncryptedFs> EncryptedFs::Generate(
    const base::FilePath& rootdir,
    cryptohome::Platform* platform,
    brillo::DeviceMapper* device_mapper,
    cryptohome::EncryptedContainerFactory* encrypted_container_factory) {
  // Calculate the maximum size of the encrypted stateful partition.
  // truncate()/ftruncate() use int64_t for file size.
  struct statvfs stateful_statbuf;
  if (!platform->StatVFS(rootdir.Append(STATEFUL_MNT), &stateful_statbuf)) {
    PLOG(ERROR) << "stat() failed on: " << rootdir.Append(STATEFUL_MNT);
    return nullptr;
  }

  int64_t fs_bytes_max = static_cast<int64_t>(stateful_statbuf.f_blocks);
  fs_bytes_max *= kSizePercent;
  fs_bytes_max *= stateful_statbuf.f_frsize;

  std::string dmcrypt_name = std::string(kCryptDevName);
  if (rootdir != base::FilePath("/")) {
    brillo::SecureBlob digest =
        cryptohome::CryptoLib::Sha256(brillo::SecureBlob(rootdir.value()));
    std::string hex = cryptohome::CryptoLib::SecureBlobToHex(digest);
    dmcrypt_name += "_" + hex.substr(0, 16);
  }

  // Initialize the encrypted container.
  cryptohome::BackingDeviceConfig backing_device_config(
      {.type = cryptohome::BackingDeviceType::kLoopbackDevice,
       .name = dmcrypt_name,
       .size = fs_bytes_max,
       .loopback = {.backing_file_path =
                        rootdir.Append(STATEFUL_MNT "/encrypted.block")}});

  cryptohome::EncryptedContainerConfig container_config(
      {.type = cryptohome::EncryptedContainerType::kDmcrypt,
       .dmcrypt_config = {.backing_device_config = backing_device_config,
                          .dmcrypt_device_name = dmcrypt_name,
                          .dmcrypt_cipher = std::string(kDmCryptDefaultCipher),
                          .mkfs_opts = BuildExt4FormatOpts(
                              kExt4BlockSize, kExt4MinBytes / kExt4BlockSize,
                              fs_bytes_max / kExt4BlockSize),
                          .tune2fs_opts = {}}});

  std::unique_ptr<cryptohome::EncryptedContainer> container =
      encrypted_container_factory->Generate(container_config, {});

  return std::make_unique<EncryptedFs>(rootdir, fs_bytes_max, dmcrypt_name,
                                       std::move(container), platform,
                                       device_mapper);
}

bool EncryptedFs::Purge() {
  LOG(INFO) << "Purging block device";
  return container_->Purge();
}

// Do all the work needed to actually set up the encrypted partition.
result_code EncryptedFs::Setup(const cryptohome::FileSystemKey& encryption_key,
                               bool rebuild) {
  result_code rc = RESULT_FAIL_FATAL;
  struct statvfs stateful_statbuf;

  // Get stateful partition statistics. This acts as an indicator of how large
  // we want the encrypted stateful partition to be.
  if (!platform_->StatVFS(stateful_mount_, &stateful_statbuf)) {
    PLOG(ERROR) << "stat() failed on: " << stateful_mount_;
    return rc;
  }

  // b/131123943: Check the size of the sparse file and resize if necessary.
  // Resizing the sparse file via truncate() should be a no-op but resizing
  // the filesystem residing on the file is a bit more involved and may need
  // to write metadata to several blocks. If there aren't enough blocks
  // available, we might succeed here but eventually fail to resize and corrupt
  // the encrypted stateful file system. Check if there are at least a few
  // blocks available on the stateful partition.
  if (stateful_statbuf.f_bfree > kMinBlocksAvailForResize)
    CheckSparseFileSize(block_path_, fs_size_);
  else
    LOG(WARNING) << "Low space on stateful partition; not attempting to resize "
                 << "the underlying block file.";

  if (rebuild) {
    // Wipe out the old files, and ignore errors.
    Purge();

    // Create new sparse file.
    LOG(INFO) << "Creating sparse backing file with size " << fs_size_;
  }

  if (!container_->Setup(encryption_key, rebuild)) {
    LOG(ERROR) << "Failed to set up encrypted container";
    TeardownByStage(TeardownStage::kTeardownContainer, true);
    return rc;
  }

  // Mount the dm-crypt partition finally.
  LOG(INFO) << "Mounting " << dmcrypt_dev_ << " onto " << encrypted_mount_;
  if (platform_->Access(encrypted_mount_, R_OK) &&
      !(platform_->CreateDirectory(encrypted_mount_) &&
        platform_->SetPermissions(encrypted_mount_,
                                  S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH))) {
    PLOG(ERROR) << dmcrypt_dev_;
    TeardownByStage(TeardownStage::kTeardownContainer, true);
    return rc;
  }
  if (!platform_->Mount(dmcrypt_dev_, encrypted_mount_, kEncryptedFSType,
                        MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_NOATIME,
                        GetMountOpts().c_str())) {
    PLOG(ERROR) << "mount: " << dmcrypt_dev_ << ", " << encrypted_mount_;
    // On failure to mount, use dumpe2fs to collect debugging data about
    // the unencrypted block device that failed to mount. Since mount-encrypted
    // cleans up afterwards, this is the only point where this data can be
    // collected.
    Dumpe2fs(dmcrypt_dev_);
    TeardownByStage(TeardownStage::kTeardownContainer, true);
    return rc;
  }

  // Always spawn filesystem resizer, in case growth was interrupted.
  // TODO(keescook): if already full size, don't resize.
  SpawnResizer(platform_, dmcrypt_dev_, kExt4MinBytes / kExt4BlockSize,
               fs_size_);

  // Perform bind mounts.
  for (auto& bind : bind_mounts_) {
    LOG(INFO) << "Bind mounting " << bind.src << " onto " << bind.dst;
    if (!CheckBind(platform_, bind)) {
      TeardownByStage(TeardownStage::kTeardownUnbind, true);
      return rc;
    }
    if (!platform_->Bind(bind.src, bind.dst)) {
      PLOG(ERROR) << "mount: " << bind.src << ", " << bind.dst;
      TeardownByStage(TeardownStage::kTeardownUnbind, true);
      return rc;
    }
  }

  // Everything completed without error.
  return RESULT_SUCCESS;
}

// Clean up all bind mounts, mounts, attaches, etc. Only the final
// action informs the return value. This makes it so that failures
// can be cleaned up from, and continue the shutdown process on a
// second call. If the loopback cannot be found, claim success.
result_code EncryptedFs::Teardown() {
  return TeardownByStage(TeardownStage::kTeardownUnbind, false);
}

result_code EncryptedFs::TeardownByStage(TeardownStage stage,
                                         bool ignore_errors) {
  switch (stage) {
    case TeardownStage::kTeardownUnbind:
      for (auto& bind : bind_mounts_) {
        LOG(INFO) << "Unmounting " << bind.dst;
        errno = 0;
        // Allow either success or a "not mounted" failure.
        if (!platform_->Unmount(bind.dst, false, nullptr) && !ignore_errors) {
          if (errno != EINVAL) {
            PLOG(ERROR) << "umount " << bind.dst;
            return RESULT_FAIL_FATAL;
          }
        }
      }

      LOG(INFO) << "Unmounting " << encrypted_mount_;
      errno = 0;
      // Allow either success or a "not mounted" failure.
      if (!platform_->Unmount(encrypted_mount_, false, nullptr) &&
          !ignore_errors) {
        if (errno != EINVAL) {
          PLOG(ERROR) << "umount " << encrypted_mount_;
          return RESULT_FAIL_FATAL;
        }
      }

      // Force syncs to make sure we don't tickle racey/buggy kernel
      // routines that might be causing crosbug.com/p/17610.
      platform_->Sync();

      // Intentionally fall through here to teardown the lower dmcrypt device.
      FALLTHROUGH;
    case TeardownStage::kTeardownContainer:
      LOG(INFO) << "Removing " << dmcrypt_dev_;
      if (!container_->Teardown() && !ignore_errors) {
        LOG(ERROR) << "Failed to teardown encrypted container";
        return RESULT_FAIL_FATAL;
      }
      platform_->Sync();
      return RESULT_SUCCESS;
  }

  LOG(ERROR) << "Teardown failed.";
  return RESULT_FAIL_FATAL;
}

result_code EncryptedFs::CheckStates(void) {
  // Verify stateful partition exists.
  if (platform_->Access(stateful_mount_, R_OK)) {
    LOG(INFO) << stateful_mount_ << "does not exist.";
    return RESULT_FAIL_FATAL;
  }
  // Verify stateful is either a separate mount, or that the
  // root directory is writable (i.e. a factory install, dev mode
  // where root remounted rw, etc).
  if (platform_->SameVFS(stateful_mount_, rootdir_) &&
      platform_->Access(rootdir_, W_OK)) {
    LOG(INFO) << stateful_mount_ << " is not mounted.";
    return RESULT_FAIL_FATAL;
  }

  // Verify encrypted partition is missing or not already mounted.
  if (platform_->Access(encrypted_mount_, R_OK) == 0 &&
      !platform_->SameVFS(encrypted_mount_, stateful_mount_)) {
    LOG(INFO) << encrypted_mount_ << " already appears to be mounted.";
    return RESULT_SUCCESS;
  }

  // Verify that bind mount targets exist.
  for (auto& bind : bind_mounts_) {
    if (platform_->Access(bind.dst, R_OK)) {
      PLOG(ERROR) << bind.dst << " mount point is missing.";
      return RESULT_FAIL_FATAL;
    }
  }

  // Verify that old bind mounts on stateful haven't happened yet.
  for (auto& bind : bind_mounts_) {
    if (bind.submount)
      continue;

    if (platform_->SameVFS(bind.dst, stateful_mount_)) {
      LOG(INFO) << bind.dst << " already bind mounted.";
      return RESULT_FAIL_FATAL;
    }
  }

  LOG(INFO) << "VFS mount state validity check ok.";
  return RESULT_SUCCESS;
}

result_code EncryptedFs::ReportInfo(void) const {
  printf("rootdir: %s\n", rootdir_.value().c_str());
  printf("stateful_mount: %s\n", stateful_mount_.value().c_str());
  printf("block_path: %s\n", block_path_.value().c_str());
  printf("encrypted_mount: %s\n", encrypted_mount_.value().c_str());
  printf("dmcrypt_name: %s\n", dmcrypt_name_.c_str());
  printf("dmcrypt_dev: %s\n", dmcrypt_dev_.value().c_str());
  printf("bind mounts:\n");
  for (auto& mnt : bind_mounts_) {
    printf("\tsrc:%s\n", mnt.src.value().c_str());
    printf("\tdst:%s\n", mnt.dst.value().c_str());
    printf("\towner:%s\n", mnt.owner.c_str());
    printf("\tmode:%o\n", mnt.mode);
    printf("\tsubmount:%d\n", mnt.submount);
    printf("\n");
  }
  return RESULT_SUCCESS;
}

brillo::SecureBlob EncryptedFs::GetKey() const {
  brillo::DevmapperTable dm_table = device_mapper_->GetTable(dmcrypt_name_);
  return dm_table.CryptGetKey();
}

}  // namespace mount_encrypted