cryptohome/homedirs.cc

// Copyright (c) 2013 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/homedirs.h"

#include <algorithm>
#include <vector>

#include <base/bind.h>
#include <base/logging.h>
#include <base/stl_util.h>
#include <base/strings/string_number_conversions.h>
#include <base/strings/stringprintf.h>
#include <chromeos/constants/cryptohome.h>
#include <chromeos/cryptohome.h>
#include <chromeos/secure_blob.h>

#include "cryptohome/credentials.h"
#include "cryptohome/cryptolib.h"
#include "cryptohome/mount.h"
#include "cryptohome/platform.h"
#include "cryptohome/user_oldest_activity_timestamp_cache.h"
#include "cryptohome/username_passkey.h"
#include "cryptohome/vault_keyset.h"

#include "key.pb.h"  // NOLINT(build/include)
#include "signed_secret.pb.h"  // NOLINT(build/include)

using base::FilePath;
using chromeos::SecureBlob;

namespace cryptohome {

const char *kShadowRoot = "/home/.shadow";
const char *kEmptyOwner = "";

HomeDirs::HomeDirs()
    : default_platform_(new Platform()),
      platform_(default_platform_.get()),
      shadow_root_(kShadowRoot),
      timestamp_cache_(NULL),
      enterprise_owned_(false),
      default_policy_provider_(new policy::PolicyProvider()),
      policy_provider_(default_policy_provider_.get()),
      crypto_(NULL),
      default_mount_factory_(new MountFactory()),
      mount_factory_(default_mount_factory_.get()),
      default_vault_keyset_factory_(new VaultKeysetFactory()),
      vault_keyset_factory_(default_vault_keyset_factory_.get()) { }

HomeDirs::~HomeDirs() { }

bool HomeDirs::Init(Platform* platform, Crypto* crypto,
                    UserOldestActivityTimestampCache *cache) {
  platform_ = platform;
  crypto_ = crypto;
  timestamp_cache_ = cache;

  LoadDevicePolicy();
  if (!platform_->DirectoryExists(shadow_root_))
    platform_->CreateDirectory(shadow_root_);
  return GetSystemSalt(NULL);
}

bool HomeDirs::FreeDiskSpace() {
  if (platform_->AmountOfFreeDiskSpace(shadow_root_) > kMinFreeSpaceInBytes) {
    return false;
  }

  // If ephemeral users are enabled, remove all cryptohomes except those
  // currently mounted or belonging to the owner.
  // |AreEphemeralUsers| will reload the policy to guarantee freshness.
  if (AreEphemeralUsersEnabled()) {
    RemoveNonOwnerCryptohomes();
    return true;
  }

  // Clean Cache directories for every user (except current one).
  DoForEveryUnmountedCryptohome(base::Bind(&HomeDirs::DeleteCacheCallback,
                                           base::Unretained(this)));

  if (platform_->AmountOfFreeDiskSpace(shadow_root_) >= kEnoughFreeSpace)
    return true;

  // Clean Cache directories for every user (except current one).
  DoForEveryUnmountedCryptohome(base::Bind(&HomeDirs::DeleteGCacheTmpCallback,
                                           base::Unretained(this)));

  if (platform_->AmountOfFreeDiskSpace(shadow_root_) >= kEnoughFreeSpace)
    return true;

  // Initialize user timestamp cache if it has not been yet. This reads the
  // last-activity time from each homedir's SerializedVaultKeyset.  This value
  // is only updated in the value keyset on unmount and every 24 hrs, so a
  // currently logged in user probably doesn't have an up to date value. This
  // is okay, since we don't delete currently logged in homedirs anyway.  (See
  // Mount::UpdateCurrentUserActivityTimestamp()).
  if (!timestamp_cache_->initialized()) {
    timestamp_cache_->Initialize();
    DoForEveryUnmountedCryptohome(base::Bind(
        &HomeDirs::AddUserTimestampToCacheCallback,
        base::Unretained(this)));
  }

  // Delete old users, the oldest first.
  // Don't delete anyone if we don't know who the owner is.
  // For consumer devices, don't delete the device owner. Enterprise-enrolled
  // devices have no owner, so don't delete the last user.
  std::string owner;
  if (enterprise_owned_ || GetOwner(&owner)) {
    int mounted_cryptohomes = CountMountedCryptohomes();
    while (!timestamp_cache_->empty()) {
      base::Time deleted_timestamp = timestamp_cache_->oldest_known_timestamp();
      FilePath deleted_user_dir = timestamp_cache_->RemoveOldestUser();

      if (enterprise_owned_) {
        // If mounted_cryptohomes== 0, then there were no mounted cryptohomes
        // and hence no logged in users.  Thus we want to skip the last user in
        // our list, since they were the most-recent user on the device.
        if (timestamp_cache_->empty() && mounted_cryptohomes == 0) {
          // Put this user back in the cache, since they shouldn't be
          // permanently skipped; they may not be most-recent the next
          // time we run, and then they should be a candidate for deletion.
          timestamp_cache_->AddExistingUser(deleted_user_dir,
                                            deleted_timestamp);

          LOG(INFO) << "Skipped deletion of the most recent device user.";
          return true;
        }
      } else {
        std::string obfuscated_username = deleted_user_dir.BaseName().value();
        if (obfuscated_username == owner) {
          // We should never delete the device owner, so we permanently skip
          // them by not adding them back to the cache.
          LOG(INFO) << "Skipped deletion of the device owner.";
          continue;
        }
      }

      std::string mountdir = deleted_user_dir.Append(kMountDir).value();
      std::string vaultdir = deleted_user_dir.Append(kVaultDir).value();
      if (platform_->IsDirectoryMountedWith(mountdir, vaultdir)) {
        LOG(INFO) << "Attempt to delete currently logged in user. Skipped...";
      } else {
        LOG(INFO) << "Freeing disk space by deleting user "
                  << deleted_user_dir.value();
        platform_->DeleteFile(deleted_user_dir.value(), true);
        if (platform_->AmountOfFreeDiskSpace(shadow_root_) >= kEnoughFreeSpace)
          return true;
      }
    }
  }

  // TODO(glotov): do further cleanup.
  return true;
}

void HomeDirs::LoadDevicePolicy() {
  policy_provider_->Reload();
}

bool HomeDirs::AreEphemeralUsersEnabled() {
  LoadDevicePolicy();
  // If the policy cannot be loaded, default to non-ephemeral users.
  bool ephemeral_users_enabled = false;
  if (policy_provider_->device_policy_is_loaded())
    policy_provider_->GetDevicePolicy().GetEphemeralUsersEnabled(
        &ephemeral_users_enabled);
  return ephemeral_users_enabled;
}

bool HomeDirs::AreCredentialsValid(const Credentials& creds) {
  scoped_ptr<VaultKeyset> vk(vault_keyset_factory()->New(platform_, crypto_));
  return GetValidKeyset(creds, vk.get());
}

bool HomeDirs::GetValidKeyset(const Credentials& creds, VaultKeyset* vk) {
  if (!vk)
    return false;

  std::string owner;
  std::string obfuscated = creds.GetObfuscatedUsername(system_salt_);
  // |AreEphemeralUsers| will reload the policy to guarantee freshness.
  if (AreEphemeralUsersEnabled() && GetOwner(&owner) && obfuscated != owner)
    return false;

  std::vector<int> key_indices;
  if (!GetVaultKeysets(obfuscated, &key_indices)) {
    LOG(WARNING) << "No valid keysets on disk for " << obfuscated;
    return false;
  }

  SecureBlob passkey;
  creds.GetPasskey(&passkey);

  for (int index : key_indices) {
    if (!vk->Load(GetVaultKeysetPath(obfuscated, index)))
      continue;
    // Skip decrypt attempts if the label doesn't match.
    // Treat an empty creds label as a wildcard.
    // Allow a creds label of "prefix<num>" for fixed indexing.
    if (!creds.key_data().label().empty() &&
        creds.key_data().label() != vk->serialized().key_data().label() &&
        creds.key_data().label() !=
          base::StringPrintf("%s%d", kKeyLegacyPrefix, index))
      continue;
    if (vk->Decrypt(passkey))
      return true;
  }
  return false;
}

bool HomeDirs::Exists(const Credentials& credentials) const {
  std::string obfuscated = credentials.GetObfuscatedUsername(system_salt_);
  std::string user_dir = FilePath(shadow_root_).Append(obfuscated).value();
  return platform_->DirectoryExists(user_dir);
}

VaultKeyset* HomeDirs::GetVaultKeyset(const Credentials& credentials) const {
  if (credentials.key_data().label().empty())
    return NULL;
  std::string obfuscated = credentials.GetObfuscatedUsername(system_salt_);

  // Walk all indices to find a match.
  // We should move to label-derived suffixes to be efficient.
  std::vector<int> key_indices;
  if (!GetVaultKeysets(obfuscated, &key_indices))
    return NULL;
  scoped_ptr<VaultKeyset> vk(vault_keyset_factory()->New(platform_, crypto_));
  for (int index : key_indices) {
    if (!LoadVaultKeysetForUser(obfuscated, index, vk.get())) {
      continue;
    }
    // Test against the label if the key has a label or create a label
    // automatically from the index number.
    std::string label = (vk->serialized().has_key_data() ?
                         vk->serialized().key_data().label() :
                         base::StringPrintf("%s%d", kKeyLegacyPrefix, index));
    if (label == credentials.key_data().label()) {
      vk->set_legacy_index(index);
      return vk.release();
    }
  }
  return NULL;
}

// TODO(wad) Figure out how this might fit in with vault_keyset.cc
bool HomeDirs::GetVaultKeysets(const std::string& obfuscated,
                               std::vector<int>* keysets) const {
  CHECK(keysets);
  std::string user_dir = FilePath(shadow_root_).Append(obfuscated).value();

  scoped_ptr<FileEnumerator> file_enumerator(
      platform_->GetFileEnumerator(user_dir, false,
                                   base::FileEnumerator::FILES));
  std::string next_path;
  while (!(next_path = file_enumerator->Next()).empty()) {
    std::string file_name = FilePath(next_path).BaseName().value();
    // Scan for "master." files.
    if (file_name.find(kKeyFile, 0, strlen(kKeyFile) == std::string::npos))
      continue;
    char *end = NULL;
    std::string index_str = file_name.substr(strlen(kKeyFile));
    const char * index_c_str = index_str.c_str();
    long index = strtol(index_c_str, &end, 10);  // NOLINT(runtime/int)
    // Ensure the entire suffix is consumed.
    if (end && *end != '\0')
      continue;
    // The test below will catch all strtol(3) error conditions.
    if (index < 0 || index >= kKeyFileMax) {
      LOG(ERROR) << "Invalid key file range: " << index;
      continue;
    }
    keysets->push_back(static_cast<int>(index));
  }

  // Ensure it is sorted numerically and not lexigraphically.
  std::sort(keysets->begin(), keysets->end());

  return keysets->size() != 0;
}

bool HomeDirs::GetVaultKeysetLabels(const Credentials& credentials,
                                    std::vector<std::string>* labels) const {
  CHECK(labels);
  std::string obfuscated = credentials.GetObfuscatedUsername(system_salt_);
  std::string user_dir = FilePath(shadow_root_).Append(obfuscated).value();

  scoped_ptr<FileEnumerator> file_enumerator(
      platform_->GetFileEnumerator(user_dir, false /* Not recursive. */,
                                   base::FileEnumerator::FILES));
  std::string next_path;
  scoped_ptr<VaultKeyset> vk(vault_keyset_factory()->New(platform_, crypto_));
  while (!(next_path = file_enumerator->Next()).empty()) {
    std::string file_name = FilePath(next_path).BaseName().value();
    // Scan for "master." files.
    if (file_name.find(kKeyFile, 0, strlen(kKeyFile) == std::string::npos)) {
      continue;
    }
    int index = 0;
    std::string index_str = file_name.substr(strlen(kKeyFile));
    // StringToInt will only return true for a perfect conversion.
    if (!base::StringToInt(index_str, &index)) {
      continue;
    }
    if (index < 0 || index >= kKeyFileMax) {
      LOG(ERROR) << "Invalid key file range: " << index;
      continue;
    }
    // Now parse the keyset to get its label or skip it.
    if (!LoadVaultKeysetForUser(obfuscated, index, vk.get())) {
      continue;
    }
    // Test against the label if the key has a label or create a label
    // automatically from the index number.
    std::string label = (vk->serialized().has_key_data() ?
                         vk->serialized().key_data().label() :
                         base::StringPrintf("%s%d", kKeyLegacyPrefix, index));
    labels->push_back(label);
  }

  return (labels->size() > 0);
}


bool HomeDirs::CheckAuthorizationSignature(const KeyData& existing_key_data,
                                           const Key& new_key,
                                           const std::string& signature) {
  // If the existing key doesn't require authorization, then there's no
  // work to be done.
  //
  // Note, only the first authorizaton_data is honored at present.
  if (!existing_key_data.authorization_data_size() ||
      !existing_key_data.authorization_data(0).has_type())
    return true;

  if (!new_key.data().has_revision()) {
    LOG(INFO) << "CheckAuthorizationSignature called with no revision";
    return false;
  }

  const KeyAuthorizationData* existing_auth_data =
      &existing_key_data.authorization_data(0);
  const KeyAuthorizationSecret* secret;
  switch (existing_auth_data->type()) {
  // The data is passed in the clear but authenticated with a shared
  // symmetric secret.
  case KeyAuthorizationData::KEY_AUTHORIZATION_TYPE_HMACSHA256:
    // Ensure there is an accessible signing key. Only a single
    // secret is allowed until there is a reason to support more.
    secret = NULL;
    for (int secret_i = 0;
         secret_i < existing_auth_data->secrets_size();
         ++secret_i) {
      secret = &existing_auth_data->secrets(secret_i);
      if (secret->usage().sign() && !secret->wrapped())
        break;
      secret = NULL;  // Clear if the candidate doesn't match.
    }
    if (!secret) {
      LOG(ERROR) << "Could not find a valid signing key for HMACSHA256";
      return false;
    }
    break;
  // The data is passed encrypted and authenticated with dedicated
  // encrypting and signing symmetric keys.
  case KeyAuthorizationData::KEY_AUTHORIZATION_TYPE_AES256CBC_HMACSHA256:
    LOG(ERROR) << "KEY_AUTHORIZATION_TYPE_AES256CBC_HMACSHA256 not supported";
    return false;
  default:
    LOG(ERROR) << "Unknown KeyAuthorizationType seen";
    return false;
  }
  // Now we're only handling HMACSHA256.
  // Specifically, HMACSHA256 is meant for interoperating with a server-side
  // signed password change operation which only specifies the revision and
  // new passphrase.  That means that change fields must be filtered to limit
  // silent updates to fields.  At present, this is done after this call. If
  // the signed fields vary by KeyAuthorizationType in the future, it should
  // be done here.
  std::string changes_str;
  ac::chrome::managedaccounts::account::Secret new_secret;
  new_secret.set_revision(new_key.data().revision());
  new_secret.set_secret(new_key.secret());
  if (!new_secret.SerializeToString(&changes_str)) {
    LOG(ERROR) << "Failed to serialized the new key";
    return false;
  }
  // Compute the HMAC
  chromeos::SecureBlob hmac_key(secret->symmetric_key());
  chromeos::SecureBlob data(changes_str.begin(), changes_str.end());
  SecureBlob hmac = CryptoLib::HmacSha256(hmac_key, data);

  // Check the HMAC
  if (signature.length() != hmac.size() ||
      chromeos::SecureMemcmp(signature.data(), hmac.data(),
                             std::min(signature.size(), hmac.size()))) {
    LOG(ERROR) << "Supplied authorization signature was invalid.";
    return false;
  }

  if (existing_key_data.has_revision() &&
      existing_key_data.revision() >= new_key.data().revision()) {
    LOG(ERROR) << "The supplied key revision was too old.";
    return false;
  }

  return true;
}

CryptohomeErrorCode HomeDirs::UpdateKeyset(
    const Credentials& credentials,
    const Key* key_changes,
    const std::string& authorization_signature) {

  scoped_ptr<VaultKeyset> vk(vault_keyset_factory()->New(platform_, crypto_));
  if (!GetValidKeyset(credentials, vk.get())) {
    // Differentiate between failure and non-existent.
    if (!credentials.key_data().label().empty()) {
      vk.reset(GetVaultKeyset(credentials));
      if (!vk.get()) {
        LOG(WARNING) << "UpdateKeyset: key not found";
        return CRYPTOHOME_ERROR_AUTHORIZATION_KEY_NOT_FOUND;
      }
    }
    LOG(WARNING) << "UpdateKeyset: invalid authentication provided";
    return CRYPTOHOME_ERROR_AUTHORIZATION_KEY_FAILED;
  }

  SerializedVaultKeyset *key = vk->mutable_serialized();

  // Check the privileges to ensure Update is allowed.
  // [In practice, Add/Remove could be used to override if present.]
  bool authorized_update = false;
  if (key->has_key_data()) {
    authorized_update = key->key_data().privileges().authorized_update();
    if (!key->key_data().privileges().update() && !authorized_update) {
      LOG(WARNING) << "UpdateKeyset: no update() privilege";
      return CRYPTOHOME_ERROR_AUTHORIZATION_KEY_DENIED;
    }
  }

  // Check the signature first so the rest of the function is untouched.
  if (authorized_update) {
    if (authorization_signature.empty() ||
        !CheckAuthorizationSignature(key->key_data(),
                                     *key_changes,
                                     authorization_signature)) {
      LOG(INFO) << "Unauthorized update attempted";
      return CRYPTOHOME_ERROR_UPDATE_SIGNATURE_INVALID;
    }
  }

  // Walk through each field and update the value.
  KeyData* merged_data = key->mutable_key_data();

  // Note! Revisions aren't tracked in general.
  if (key_changes->data().has_revision()) {
    merged_data->set_revision(key_changes->data().revision());
  }

  // TODO(wad,dkrahn): Add privilege dropping.
  SecureBlob passkey;
  credentials.GetPasskey(&passkey);
  if (key_changes->has_secret()) {
    SecureBlob new_passkey(key_changes->secret().begin(),
                           key_changes->secret().end());
    passkey.swap(new_passkey);
  }

  // Only merge additional KeyData if the update is not restricted.
  if (!authorized_update) {
    if (key_changes->data().has_type()) {
      merged_data->set_type(key_changes->data().type());
    }
    if (key_changes->data().has_label()) {
      merged_data->set_label(key_changes->data().label());
    }
    // Do not allow authorized_updates to change their keys unless we add
    // a new signature type.  This can be done in the future by adding
    // the authorization_data() to the new key_data, and changing the
    // CheckAuthorizationSignature() to check for a compatible "upgrade".
    if (key_changes->data().authorization_data_size() > 0) {
      // Only the first will be merged for now.
      *(merged_data->add_authorization_data()) =
          key_changes->data().authorization_data(0);
    }
  }

  if (!vk->Encrypt(passkey) || !vk->Save(vk->source_file())) {
    LOG(ERROR) << "Failed to encrypt and write the updated keyset";
    return CRYPTOHOME_ERROR_BACKING_STORE_FAILURE;
  }
  return CRYPTOHOME_ERROR_NOT_SET;
}

CryptohomeErrorCode HomeDirs::AddKeyset(
                         const Credentials& existing_credentials,
                         const SecureBlob& new_passkey,
                         const KeyData* new_data,  // NULLable
                         bool clobber,
                         int* index) {
  // TODO(wad) Determine how to best bubble up the failures MOUNT_ERROR
  //           encapsulate wrt the TPM behavior.
  std::string obfuscated = existing_credentials.GetObfuscatedUsername(
    system_salt_);

  scoped_ptr<VaultKeyset> vk(vault_keyset_factory()->New(platform_, crypto_));
  if (!GetValidKeyset(existing_credentials, vk.get())) {
    // Differentiate between failure and non-existent.
    if (!existing_credentials.key_data().label().empty()) {
      vk.reset(GetVaultKeyset(existing_credentials));
      if (!vk.get()) {
        LOG(WARNING) << "AddKeyset: key not found";
        return CRYPTOHOME_ERROR_AUTHORIZATION_KEY_NOT_FOUND;
      }
    }
    LOG(WARNING) << "AddKeyset: invalid authentication provided";
    return CRYPTOHOME_ERROR_AUTHORIZATION_KEY_FAILED;
  }

  // Check the privileges to ensure Add is allowed.
  // Keys without extended data are considered fully privileged.
  if (vk->serialized().has_key_data() &&
      !vk->serialized().key_data().privileges().add()) {
    // TODO(wad) Ensure this error can be returned as a KEY_DENIED error
    //           for AddKeyEx.
    LOG(WARNING) << "AddKeyset: no add() privilege";
    return CRYPTOHOME_ERROR_AUTHORIZATION_KEY_DENIED;
  }

  // Walk the namespace looking for the first free spot.
  // Optimizations can come later.
  // Note, nothing is stopping simultaenous access to these files
  // or enforcing mandatory locking.
  int new_index = 0;
  FILE* vk_file = NULL;
  std::string vk_path;
  for ( ; new_index < kKeyFileMax; ++new_index) {
    vk_path = GetVaultKeysetPath(obfuscated, new_index);
    // Rely on fopen()'s O_EXCL|O_CREAT behavior to fail
    // repeatedly until there is an opening.
    // TODO(wad) Add a clean-up-0-byte-keysets helper to c-home startup
    vk_file = platform_->OpenFile(vk_path, "wx");
    if (vk_file)  // got one
      break;
  }

  if (!vk_file) {
    LOG(WARNING) << "Failed to find an available keyset slot";
    return CRYPTOHOME_ERROR_KEY_QUOTA_EXCEEDED;
  }
  // Once the file has been claimed, we can release the handle.
  platform_->CloseFile(vk_file);

  // Before persisting, check, in a racy-way, if there is
  // an existing labeled credential.
  if (new_data) {
    UsernamePasskey search_cred(existing_credentials.username().c_str(),
                                SecureBlob());
    search_cred.set_key_data(*new_data);
    scoped_ptr<VaultKeyset> match(GetVaultKeyset(search_cred));
    if (match.get()) {
      LOG(INFO) << "Label already exists.";
      platform_->DeleteFile(vk_path, false);
      if (!clobber) {
        return CRYPTOHOME_ERROR_KEY_LABEL_EXISTS;
      }
      new_index = match->legacy_index();
      vk_path = match->source_file();
    }
  }
  // Since we're reusing the authorizing VaultKeyset, be careful with the
  // metadata.
  vk->mutable_serialized()->clear_key_data();
  if (new_data) {
    *(vk->mutable_serialized()->mutable_key_data()) = *new_data;
  }

  // Repersist the VK with the new creds.
  CryptohomeErrorCode added = CRYPTOHOME_ERROR_NOT_SET;
  if (!vk->Encrypt(new_passkey) || !vk->Save(vk_path)) {
    LOG(WARNING) << "Failed to encrypt or write the new keyset";
    added = CRYPTOHOME_ERROR_BACKING_STORE_FAILURE;
    // If we're clobbering, don't delete on error.
    if (!clobber) {
      platform_->DeleteFile(vk_path, false);
    }
  } else {
    *index = new_index;
  }
  return added;
}

CryptohomeErrorCode HomeDirs::RemoveKeyset(
  const Credentials& credentials,
  const KeyData& key_data) {
  // This error condition should be caught by the caller.
  if (key_data.label().empty())
    return CRYPTOHOME_ERROR_KEY_NOT_FOUND;

  scoped_ptr<VaultKeyset> vk(vault_keyset_factory()->New(platform_, crypto_));
  if (!GetValidKeyset(credentials, vk.get())) {
    // Differentiate between failure and non-existent.
    if (!credentials.key_data().label().empty()) {
      vk.reset(GetVaultKeyset(credentials));
      if (!vk.get()) {
        LOG(WARNING) << "RemoveKeyset: key not found";
        return CRYPTOHOME_ERROR_AUTHORIZATION_KEY_NOT_FOUND;
      }
    }
    LOG(WARNING) << "RemoveKeyset: invalid authentication provided";
    return CRYPTOHOME_ERROR_AUTHORIZATION_KEY_FAILED;
  }

  // Legacy keys can remove any other key. Otherwise a key needs explicit
  // privileges.
  if (vk->serialized().has_key_data() &&
      !vk->serialized().key_data().privileges().remove()) {
    LOG(WARNING) << "RemoveKeyset: no remove() privilege";
    return CRYPTOHOME_ERROR_AUTHORIZATION_KEY_DENIED;
  }

  UsernamePasskey removal_creds(credentials.username().c_str(), SecureBlob());
  removal_creds.set_key_data(key_data);
  scoped_ptr<VaultKeyset> remove_vk(GetVaultKeyset(removal_creds));
  if (!remove_vk.get()) {
    LOG(WARNING) << "RemoveKeyset: key to remove not found";
    return CRYPTOHOME_ERROR_KEY_NOT_FOUND;
  }

  std::string obfuscated = credentials.GetObfuscatedUsername(
    system_salt_);
  if (!ForceRemoveKeyset(obfuscated, remove_vk->legacy_index())) {
    LOG(ERROR) << "RemoveKeyset: failed to remove keyset file";
    return CRYPTOHOME_ERROR_BACKING_STORE_FAILURE;
  }
  return  CRYPTOHOME_ERROR_NOT_SET;
}

bool HomeDirs::ForceRemoveKeyset(const std::string& obfuscated, int index) {
  // Note, external callers should check credentials.
  if (index < 0 || index >= kKeyFileMax)
    return false;

  std::string path = GetVaultKeysetPath(obfuscated, index);
  if (!platform_->FileExists(path)) {
    LOG(WARNING) << "ForceRemoveKeyset: keyset " << index << " for "
                 << obfuscated << " does not exist";
    // Since it doesn't exist, then we're done.
    return true;
  }
  // TODO(wad) Add file zeroing here or centralize with other code.
  return platform_->DeleteFile(path, false);
}

bool HomeDirs::MoveKeyset(const std::string& obfuscated, int src, int dst) {
  if (src < 0 || dst < 0 || src >= kKeyFileMax || dst >= kKeyFileMax)
    return false;

  std::string src_path = GetVaultKeysetPath(obfuscated, src);
  std::string dst_path = GetVaultKeysetPath(obfuscated, dst);
  if (!platform_->FileExists(src_path))
    return false;
  if (platform_->FileExists(dst_path))
    return false;
  // Grab the destination exclusively
  FILE* vk_file = platform_->OpenFile(dst_path, "wx");
  if (!vk_file)
    return false;
  // The creation occurred so there's no reason to keep the handle.
  platform_->CloseFile(vk_file);
  if (!platform_->Rename(src_path, dst_path))
    return false;
  return true;
}

std::string HomeDirs::GetVaultKeysetPath(const std::string& obfuscated,
                                         int index) const {
  return base::StringPrintf("%s/%s/%s%d",
                            shadow_root_.c_str(),
                            obfuscated.c_str(),
                            kKeyFile,
                            index);
}

void HomeDirs::RemoveNonOwnerCryptohomesCallback(const FilePath& vault) {
  if (!enterprise_owned_) {  // Enterprise owned? Delete it all.
    std::string owner;
    if (!GetOwner(&owner) ||  // No owner? bail.
        // Don't delete the owner's vault!
        // TODO(wad,ellyjones) Add GetUser*Path-helpers
        vault == FilePath(shadow_root_).Append(owner).Append(kVaultDir))
    return;
  }
  // Once we're sure this is not the owner vault, delete it.
  platform_->DeleteFile(vault.DirName().value(), true);
}

void HomeDirs::RemoveNonOwnerCryptohomes() {
  std::string owner;
  if (!enterprise_owned_ && !GetOwner(&owner))
    return;

  DoForEveryUnmountedCryptohome(base::Bind(
      &HomeDirs::RemoveNonOwnerCryptohomesCallback,
      base::Unretained(this)));
  // TODO(ellyjones): is this valuable? These two directories should just be
  // mountpoints.
  RemoveNonOwnerDirectories(chromeos::cryptohome::home::GetUserPathPrefix());
  RemoveNonOwnerDirectories(chromeos::cryptohome::home::GetRootPathPrefix());
}

void HomeDirs::DoForEveryUnmountedCryptohome(
    const CryptohomeCallback& cryptohome_cb) {
  std::vector<std::string> entries;
  if (!platform_->EnumerateDirectoryEntries(shadow_root_, false, &entries)) {
    return;
  }
  for (std::vector<std::string>::iterator it = entries.begin();
       it != entries.end(); ++it) {
    FilePath path(*it);
    const std::string dir_name = path.BaseName().value();
    if (!chromeos::cryptohome::home::IsSanitizedUserName(dir_name)) {
      continue;
    }
    std::string vault_path = path.Append(kVaultDir).value();
    std::string mount_path = path.Append(kMountDir).value();
    if (!platform_->DirectoryExists(vault_path)) {
      continue;
    }
    if (platform_->IsDirectoryMountedWith(mount_path, vault_path)) {
      continue;
    }
    cryptohome_cb.Run(FilePath(vault_path));
  }
}

int HomeDirs::CountMountedCryptohomes() const {
  std::vector<std::string> entries;
  int mounts = 0;
  if (!platform_->EnumerateDirectoryEntries(shadow_root_, false, &entries)) {
    return 0;
  }
  for (std::vector<std::string>::iterator it = entries.begin();
       it != entries.end(); ++it) {
    FilePath path(*it);
    const std::string dir_name = path.BaseName().value();
    if (!chromeos::cryptohome::home::IsSanitizedUserName(dir_name)) {
      continue;
    }
    std::string vault_path = path.Append(kVaultDir).value();
    std::string mount_path = path.Append(kMountDir).value();
    if (!platform_->DirectoryExists(vault_path)) {
      continue;
    }
    if (!platform_->IsDirectoryMountedWith(mount_path, vault_path)) {
      continue;
    }
    mounts++;
  }
  return mounts;
}

void HomeDirs::DeleteDirectoryContents(const FilePath& dir) {
  scoped_ptr<FileEnumerator> subdir_enumerator(platform_->GetFileEnumerator(
      dir.value(),
      false,
      base::FileEnumerator::FILES |
          base::FileEnumerator::DIRECTORIES |
          base::FileEnumerator::SHOW_SYM_LINKS));
  for (std::string subdir_path = subdir_enumerator->Next();
       !subdir_path.empty();
       subdir_path = subdir_enumerator->Next()) {
    platform_->DeleteFile(subdir_path, true);
  }
}

void HomeDirs::RemoveNonOwnerDirectories(const FilePath& prefix) {
  std::vector<std::string> dirents;
  if (!platform_->EnumerateDirectoryEntries(prefix.value(), false, &dirents))
    return;
  std::string owner;
  if (!enterprise_owned_ && !GetOwner(&owner))
    return;
  for (std::vector<std::string>::iterator it = dirents.begin();
       it != dirents.end(); ++it) {
    FilePath path(*it);
    const std::string basename = path.BaseName().value();
    if (!enterprise_owned_ && !strcasecmp(basename.c_str(), owner.c_str()))
      continue;  // Skip the owner's directory.
    if (!chromeos::cryptohome::home::IsSanitizedUserName(basename))
      continue;  // Skip any directory whose name is not an obfuscated user
                 // name.
    if (platform_->IsDirectoryMounted(path.value()))
      continue;  // Skip any directory that is currently mounted.
    platform_->DeleteFile(path.value(), true);
  }
}

void HomeDirs::DeleteCacheCallback(const FilePath& vault) {
  const FilePath cache = vault.Append(kUserHomeSuffix).Append(kCacheDir);
  LOG(WARNING) << "Deleting Cache " << cache.value();
  DeleteDirectoryContents(cache);
}

void HomeDirs::DeleteGCacheTmpCallback(const FilePath& vault) {
  const FilePath gcachetmp = vault.Append(kUserHomeSuffix).Append(kGCacheDir)
      .Append(kGCacheVersionDir).Append(kGCacheTmpDir);
  LOG(WARNING) << "Deleting GCache " << gcachetmp.value();
  DeleteDirectoryContents(gcachetmp);
}

void HomeDirs::AddUserTimestampToCacheCallback(const FilePath& vault) {
  const FilePath user_dir = vault.DirName();
  const std::string obfuscated_username = user_dir.BaseName().value();
  //  Add a timestamp for every key.
  std::vector<int> key_indices;
  // Failure is okay since the loop falls through.
  GetVaultKeysets(obfuscated_username, &key_indices);
  scoped_ptr<VaultKeyset> keyset(
      vault_keyset_factory()->New(platform_, crypto_));
  // Collect the most recent time for a given user by walking all
  // vaults.  This avoids trying to keep them in sync atomically.
  // TODO(wad,?) Move non-key vault metadata to a standalone file.
  base::Time timestamp = base::Time();
  for (int index : key_indices) {
    if (LoadVaultKeysetForUser(obfuscated_username, index, keyset.get()) &&
        keyset->serialized().has_last_activity_timestamp()) {
      const base::Time t = base::Time::FromInternalValue(
          keyset->serialized().last_activity_timestamp());
      if (t > timestamp)
        timestamp = t;
    }
  }
  if (!timestamp.is_null()) {
      timestamp_cache_->AddExistingUser(user_dir, timestamp);
  } else {
      timestamp_cache_->AddExistingUserNotime(user_dir);
  }
}

bool HomeDirs::LoadVaultKeysetForUser(const std::string& obfuscated_user,
                                      int index,
                                      VaultKeyset* keyset) const {
  // Load the encrypted keyset
  std::string user_key_file = GetVaultKeysetPath(obfuscated_user, index);
  // We don't have keys yet, so just load it.
  // TODO(wad) Move to passing around keysets and not serialized versions.
  if (!keyset->Load(user_key_file)) {
    LOG(ERROR) << "Failed to read keyset file for user " << obfuscated_user;
    return false;
  }
  return true;
}

bool HomeDirs::GetPlainOwner(std::string* owner) {
  LoadDevicePolicy();
  if (!policy_provider_->device_policy_is_loaded())
    return false;
  policy_provider_->GetDevicePolicy().GetOwner(owner);
  return true;
}

bool HomeDirs::GetOwner(std::string* owner) {
  std::string plain_owner;
  if (!GetPlainOwner(&plain_owner) || plain_owner.empty())
    return false;

  if (!GetSystemSalt(NULL))
    return false;
  *owner = UsernamePasskey(plain_owner.c_str(), chromeos::Blob())
      .GetObfuscatedUsername(system_salt_);
  return true;
}

bool HomeDirs::GetSystemSalt(SecureBlob* blob) {
  FilePath salt_file = FilePath(shadow_root_).Append("salt");
  if (!crypto_->GetOrCreateSalt(salt_file, CRYPTOHOME_DEFAULT_SALT_LENGTH,
                                false, &system_salt_)) {
    LOG(ERROR) << "Failed to create system salt.";
    return false;
  }
  if (blob)
    *blob = system_salt_;
  return true;
}

bool HomeDirs::Remove(const std::string& username) {
  UsernamePasskey passkey(username.c_str(), SecureBlob());
  std::string obfuscated = passkey.GetObfuscatedUsername(system_salt_);
  FilePath user_dir = FilePath(shadow_root_).Append(obfuscated);
  FilePath user_path = chromeos::cryptohome::home::GetUserPath(username);
  FilePath root_path = chromeos::cryptohome::home::GetRootPath(username);
  return platform_->DeleteFile(user_dir.value(), true) &&
         platform_->DeleteFile(user_path.value(), true) &&
         platform_->DeleteFile(root_path.value(), true);
}

bool HomeDirs::Migrate(const Credentials& newcreds,
                       const SecureBlob& oldkey) {
  SecureBlob newkey;
  newcreds.GetPasskey(&newkey);
  UsernamePasskey oldcreds(newcreds.username().c_str(), oldkey);
  scoped_refptr<Mount> mount = mount_factory_->New();
  mount->Init(platform_, crypto_, timestamp_cache_);
  std::string obfuscated = newcreds.GetObfuscatedUsername(system_salt_);
  if (!mount->MountCryptohome(oldcreds, Mount::MountArgs(), NULL)) {
    LOG(ERROR) << "Migrate: Mount failed";
    // Fail as early as possible. Note that we don't have to worry about leaking
    // this mount - Mount unmounts itself if it's still mounted in the
    // destructor.
    return false;
  }
  int key_index = mount->CurrentKey();
  if (key_index == -1) {
    LOG(ERROR) << "Attempted migration of key-less mount.";
    return false;
  }

  // Grab the current key and check its permissions early.
  // add() and remove() are required.  mount() was checked
  // already during MountCryptohome().
  scoped_ptr<VaultKeyset> vk(
    vault_keyset_factory()->New(platform_, crypto_));
  if (!LoadVaultKeysetForUser(obfuscated, key_index, vk.get())) {
    LOG(ERROR) << "Migrate: failed to reload the active keyset";
    return false;
  }
  const KeyData *key_data = NULL;
  if (vk->serialized().has_key_data()) {
    key_data = &(vk->serialized().key_data());
    // legacy keys are full privs
    if (!vk->serialized().key_data().privileges().add() ||
        !vk->serialized().key_data().privileges().remove()) {
      LOG(ERROR) << "Migrate: key lacks sufficient privileges()";
      return false;
    }
  }

  SecureBlob old_auth_data;
  SecureBlob auth_data;
  std::string username = newcreds.username();
  FilePath salt_file = GetChapsTokenSaltPath(username);
  if (!crypto_->PasskeyToTokenAuthData(newkey, salt_file, &auth_data) ||
      !crypto_->PasskeyToTokenAuthData(oldkey, salt_file, &old_auth_data)) {
    // On failure, token data may be partially migrated. Ideally, the user
    // will re-attempt with the same passphrase.
    return false;
  }
  chaps_client_.ChangeTokenAuthData(
      GetChapsTokenDir(username),
      old_auth_data,
      auth_data);

  int new_key_index = -1;
  // For a labeled key with the same label as the old key,
  //  this will overwrite the existing keyset file.
  if (AddKeyset(oldcreds, newkey, key_data, true, &new_key_index) !=
      CRYPTOHOME_ERROR_NOT_SET) {
    LOG(ERROR) << "Migrate: failed to add the new keyset";
    return false;
  }

  // For existing unlabeled keys, we need to remove the old key and swap
  // the slot.  If the key was labeled and clobbered, the key indices will
  // match.
  if (new_key_index != key_index) {
    if (!ForceRemoveKeyset(obfuscated, key_index)) {
      LOG(ERROR) << "Migrate: unable to delete the old keyset: " << key_index;
      // TODO(wad) Should we zero it or move it into space?
      // Fallthrough
    }
    // Put the new one in its slot.
    if (!MoveKeyset(obfuscated, new_key_index, key_index)) {
      // This is bad, but non-terminal since we have a valid, migrated key.
      LOG(ERROR) << "Migrate: failed to move the new key to the old slot";
      key_index = new_key_index;
    }
  }

  // Remove all other keysets during a "migration".
  std::vector<int> key_indices;
  if (!GetVaultKeysets(obfuscated, &key_indices)) {
    LOG(WARNING) << "Failed to enumerate keysets after adding one. Weird.";
    // Fallthrough: The user is migrated, but something else changed keys.
  }
  for (int index : key_indices) {
    if (index == key_index)
      continue;
    LOG(INFO) << "Removing keyset " << index << " due to migration.";
    ForceRemoveKeyset(obfuscated, index);  // Failure is ok.
  }

  return true;
}

namespace {
  const char *kChapsDaemonName = "chaps";
  const char *kChapsDirName = ".chaps";
  const char *kChapsSaltName = "auth_data_salt";
}

FilePath HomeDirs::GetChapsTokenDir(const std::string& user) const {
  return chromeos::cryptohome::home::GetDaemonPath(user, kChapsDaemonName);
}

FilePath HomeDirs::GetLegacyChapsTokenDir(const std::string& user) const {
  return chromeos::cryptohome::home::GetUserPath(user).Append(kChapsDirName);
}

FilePath HomeDirs::GetChapsTokenSaltPath(const std::string& user) const {
  return GetChapsTokenDir(user).Append(kChapsSaltName);
}

}  // namespace cryptohome