/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "FsCrypt.h"
#include "Checkpoint.h"
#include "KeyStorage.h"
#include "KeyUtil.h"
#include "Utils.h"
#include "VoldUtil.h"
#include <algorithm>
#include <map>
#include <optional>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <private/android_filesystem_config.h>
#include <private/android_projectid_config.h>
#include "android/os/IVold.h"
#define MANAGE_MISC_DIRS 0
#include <cutils/fs.h>
#include <cutils/properties.h>
#include <fscrypt/fscrypt.h>
#include <keyutils.h>
#include <libdm/dm.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <android-base/unique_fd.h>
using android::base::Basename;
using android::base::Realpath;
using android::base::StartsWith;
using android::base::StringPrintf;
using android::fs_mgr::GetEntryForMountPoint;
using android::vold::BuildDataPath;
using android::vold::IsDotOrDotDot;
using android::vold::IsFilesystemSupported;
using android::vold::kEmptyAuthentication;
using android::vold::KeyBuffer;
using android::vold::KeyGeneration;
using android::vold::retrieveKey;
using android::vold::retrieveOrGenerateKey;
using android::vold::SetDefaultAcl;
using android::vold::SetQuotaInherit;
using android::vold::SetQuotaProjectId;
using android::vold::writeStringToFile;
using namespace android::fscrypt;
using namespace android::dm;
namespace {
const std::string device_key_dir = std::string() + DATA_MNT_POINT + fscrypt_unencrypted_folder;
const std::string device_key_path = device_key_dir + "/key";
const std::string device_key_temp = device_key_dir + "/temp";
const std::string user_key_dir = std::string() + DATA_MNT_POINT + "/misc/vold/user_keys";
const std::string user_key_temp = user_key_dir + "/temp";
const std::string prepare_subdirs_path = "/system/bin/vold_prepare_subdirs";
const std::string systemwide_volume_key_dir =
std::string() + DATA_MNT_POINT + "/misc/vold/volume_keys";
const std::string data_data_dir = std::string() + DATA_MNT_POINT + "/data";
const std::string data_user_0_dir = std::string() + DATA_MNT_POINT + "/user/0";
const std::string media_obb_dir = std::string() + DATA_MNT_POINT + "/media/obb";
// The file encryption options to use on the /data filesystem
EncryptionOptions s_data_options;
// Some users are ephemeral; don't try to store or wipe their keys on disk.
std::set<userid_t> s_ephemeral_users;
// New CE keys that haven't been committed to disk yet
std::map<userid_t, KeyBuffer> s_new_ce_keys;
// The system DE encryption policy
EncryptionPolicy s_device_policy;
// Map user ids to encryption policies
std::map<userid_t, EncryptionPolicy> s_de_policies;
std::map<userid_t, EncryptionPolicy> s_ce_policies;
// CE key fixation operations that have been deferred to checkpoint commit
std::map<std::string, std::string> s_deferred_fixations;
} // namespace
// Returns KeyGeneration suitable for key as described in EncryptionOptions
static KeyGeneration makeGen(const EncryptionOptions& options) {
if (options.version == 0) {
LOG(ERROR) << "EncryptionOptions not initialized";
return android::vold::neverGen();
}
return KeyGeneration{FSCRYPT_MAX_KEY_SIZE, true, options.use_hw_wrapped_key};
}
static const char* escape_empty(const std::string& value) {
return value.empty() ? "null" : value.c_str();
}
static std::string get_de_key_path(userid_t user_id) {
return StringPrintf("%s/de/%d", user_key_dir.c_str(), user_id);
}
static std::string get_ce_key_directory_path(userid_t user_id) {
return StringPrintf("%s/ce/%d", user_key_dir.c_str(), user_id);
}
// Returns the keys newest first
static std::vector<std::string> get_ce_key_paths(const std::string& directory_path) {
auto dirp = std::unique_ptr<DIR, int (*)(DIR*)>(opendir(directory_path.c_str()), closedir);
if (!dirp) {
PLOG(ERROR) << "Unable to open ce key directory: " + directory_path;
return std::vector<std::string>();
}
std::vector<std::string> result;
for (;;) {
errno = 0;
auto const entry = readdir(dirp.get());
if (!entry) {
if (errno) {
PLOG(ERROR) << "Unable to read ce key directory: " + directory_path;
return std::vector<std::string>();
}
break;
}
if (IsDotOrDotDot(*entry)) continue;
if (entry->d_type != DT_DIR || entry->d_name[0] != 'c') {
LOG(DEBUG) << "Skipping non-key " << entry->d_name;
continue;
}
result.emplace_back(directory_path + "/" + entry->d_name);
}
std::sort(result.begin(), result.end());
std::reverse(result.begin(), result.end());
return result;
}
static std::string get_ce_key_current_path(const std::string& directory_path) {
return directory_path + "/current";
}
static bool get_ce_key_new_path(const std::string& directory_path,
const std::vector<std::string>& paths, std::string* ce_key_path) {
if (paths.empty()) {
*ce_key_path = get_ce_key_current_path(directory_path);
return true;
}
for (unsigned int i = 0; i < UINT_MAX; i++) {
auto const candidate = StringPrintf("%s/cx%010u", directory_path.c_str(), i);
if (paths[0] < candidate) {
*ce_key_path = candidate;
return true;
}
}
return false;
}
// Discard all keys but the named one; rename it to canonical name.
static bool fixate_user_ce_key(const std::string& directory_path, const std::string& to_fix,
const std::vector<std::string>& paths) {
bool need_sync = false;
for (auto const other_path : paths) {
if (other_path != to_fix) {
android::vold::destroyKey(other_path);
need_sync = true;
}
}
auto const current_path = get_ce_key_current_path(directory_path);
if (to_fix != current_path) {
LOG(DEBUG) << "Renaming " << to_fix << " to " << current_path;
if (!android::vold::RenameKeyDir(to_fix, current_path)) return false;
need_sync = true;
}
if (need_sync && !android::vold::FsyncDirectory(directory_path)) return false;
return true;
}
static bool read_and_fixate_user_ce_key(userid_t user_id,
const android::vold::KeyAuthentication& auth,
KeyBuffer* ce_key) {
auto const directory_path = get_ce_key_directory_path(user_id);
auto const paths = get_ce_key_paths(directory_path);
for (auto const ce_key_path : paths) {
LOG(DEBUG) << "Trying user CE key " << ce_key_path;
if (retrieveKey(ce_key_path, auth, ce_key)) {
LOG(DEBUG) << "Successfully retrieved key";
s_deferred_fixations.erase(directory_path);
fixate_user_ce_key(directory_path, ce_key_path, paths);
return true;
}
}
LOG(ERROR) << "Failed to find working ce key for user " << user_id;
return false;
}
static bool MightBeEmmcStorage(const std::string& blk_device) {
// Handle symlinks.
std::string real_path;
if (!Realpath(blk_device, &real_path)) {
real_path = blk_device;
}
// Handle logical volumes.
auto& dm = DeviceMapper::Instance();
for (;;) {
auto parent = dm.GetParentBlockDeviceByPath(real_path);
if (!parent.has_value()) break;
real_path = *parent;
}
// Now we should have the "real" block device.
LOG(DEBUG) << "MightBeEmmcStorage(): blk_device = " << blk_device
<< ", real_path=" << real_path;
std::string name = Basename(real_path);
return StartsWith(name, "mmcblk") ||
// virtio devices may provide inline encryption support that is
// backed by eMMC inline encryption on the host, thus inheriting the
// DUN size limitation. So virtio devices must be allowed here too.
// TODO(b/207390665): check the maximum DUN size directly instead.
StartsWith(name, "vd");
}
// Sets s_data_options to the file encryption options for the /data filesystem.
static bool init_data_file_encryption_options() {
auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
if (entry == nullptr) {
LOG(ERROR) << "No mount point entry for " << DATA_MNT_POINT;
return false;
}
if (!ParseOptions(entry->encryption_options, &s_data_options)) {
LOG(ERROR) << "Unable to parse encryption options for " << DATA_MNT_POINT ": "
<< entry->encryption_options;
return false;
}
if ((s_data_options.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) &&
!MightBeEmmcStorage(entry->blk_device)) {
LOG(ERROR) << "The emmc_optimized encryption flag is only allowed on eMMC storage. Remove "
"this flag from the device's fstab";
return false;
}
return true;
}
static bool install_storage_key(const std::string& mountpoint, const EncryptionOptions& options,
const KeyBuffer& key, EncryptionPolicy* policy) {
if (options.version == 0) {
LOG(ERROR) << "EncryptionOptions not initialized";
return false;
}
KeyBuffer ephemeral_wrapped_key;
if (options.use_hw_wrapped_key) {
if (!exportWrappedStorageKey(key, &ephemeral_wrapped_key)) {
LOG(ERROR) << "Failed to get ephemeral wrapped key";
return false;
}
}
return installKey(mountpoint, options, options.use_hw_wrapped_key ? ephemeral_wrapped_key : key,
policy);
}
// Retrieve the options to use for encryption policies on adoptable storage.
static bool get_volume_file_encryption_options(EncryptionOptions* options) {
// If we give the empty string, libfscrypt will use the default (currently XTS)
auto contents_mode = android::base::GetProperty("ro.crypto.volume.contents_mode", "");
// HEH as default was always a mistake. Use the libfscrypt default (CTS)
// for devices launching on versions above Android 10.
auto first_api_level = GetFirstApiLevel();
auto filenames_mode =
android::base::GetProperty("ro.crypto.volume.filenames_mode",
first_api_level > __ANDROID_API_Q__ ? "" : "aes-256-heh");
auto options_string = android::base::GetProperty("ro.crypto.volume.options",
contents_mode + ":" + filenames_mode);
if (!ParseOptionsForApiLevel(first_api_level, options_string, options)) {
LOG(ERROR) << "Unable to parse volume encryption options: " << options_string;
return false;
}
if (options->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
LOG(ERROR) << "The emmc_optimized encryption flag is only allowed on eMMC storage. Remove "
"this flag from ro.crypto.volume.options";
return false;
}
return true;
}
static bool read_and_install_user_ce_key(userid_t user_id,
const android::vold::KeyAuthentication& auth) {
if (s_ce_policies.count(user_id) != 0) return true;
KeyBuffer ce_key;
if (!read_and_fixate_user_ce_key(user_id, auth, &ce_key)) return false;
EncryptionPolicy ce_policy;
if (!install_storage_key(DATA_MNT_POINT, s_data_options, ce_key, &ce_policy)) return false;
s_ce_policies[user_id] = ce_policy;
LOG(DEBUG) << "Installed ce key for user " << user_id;
return true;
}
// Prepare a directory without assigning it an encryption policy. The directory
// will inherit the encryption policy of its parent directory, or will be
// unencrypted if the parent directory is unencrypted.
static bool prepare_dir(const std::string& dir, mode_t mode, uid_t uid, gid_t gid) {
LOG(DEBUG) << "Preparing: " << dir;
if (android::vold::PrepareDir(dir, mode, uid, gid, 0) != 0) {
PLOG(ERROR) << "Failed to prepare " << dir;
return false;
}
return true;
}
// Prepare a directory and assign it the given encryption policy.
static bool prepare_dir_with_policy(const std::string& dir, mode_t mode, uid_t uid, gid_t gid,
const EncryptionPolicy& policy) {
if (!prepare_dir(dir, mode, uid, gid)) return false;
if (IsFbeEnabled() && !EnsurePolicy(policy, dir)) return false;
return true;
}
static bool destroy_dir(const std::string& dir) {
LOG(DEBUG) << "Destroying: " << dir;
if (rmdir(dir.c_str()) != 0 && errno != ENOENT) {
PLOG(ERROR) << "Failed to destroy " << dir;
return false;
}
return true;
}
// Checks whether the DE key directory exists for the given user.
static bool de_key_exists(userid_t user_id) {
return android::vold::pathExists(get_de_key_path(user_id));
}
// Checks whether at least one CE key subdirectory exists for the given user.
static bool ce_key_exists(userid_t user_id) {
auto directory_path = get_ce_key_directory_path(user_id);
// The common case is that "$dir/current" exists, so check for that first.
if (android::vold::pathExists(get_ce_key_current_path(directory_path))) return true;
// Else, there could still be another subdirectory of $dir (if a crash
// occurred during fixate_user_ce_key()), so check for one.
return android::vold::pathExists(directory_path) && !get_ce_key_paths(directory_path).empty();
}
static bool create_de_key(userid_t user_id, bool ephemeral) {
KeyBuffer de_key;
if (!generateStorageKey(makeGen(s_data_options), &de_key)) return false;
if (!ephemeral && !android::vold::storeKeyAtomically(get_de_key_path(user_id), user_key_temp,
kEmptyAuthentication, de_key))
return false;
EncryptionPolicy de_policy;
if (!install_storage_key(DATA_MNT_POINT, s_data_options, de_key, &de_policy)) return false;
s_de_policies[user_id] = de_policy;
LOG(INFO) << "Created DE key for user " << user_id;
return true;
}
static bool create_ce_key(userid_t user_id, bool ephemeral) {
KeyBuffer ce_key;
if (!generateStorageKey(makeGen(s_data_options), &ce_key)) return false;
if (!ephemeral) {
if (!prepare_dir(get_ce_key_directory_path(user_id), 0700, AID_ROOT, AID_ROOT))
return false;
// We don't store the CE key on disk here, since here we don't have the
// secret needed to do so securely. Instead, we cache it in memory for
// now, and we store it later in fscrypt_set_user_key_protection().
s_new_ce_keys.insert({user_id, ce_key});
}
EncryptionPolicy ce_policy;
if (!install_storage_key(DATA_MNT_POINT, s_data_options, ce_key, &ce_policy)) return false;
s_ce_policies[user_id] = ce_policy;
LOG(INFO) << "Created CE key for user " << user_id;
return true;
}
static bool lookup_policy(const std::map<userid_t, EncryptionPolicy>& key_map, userid_t user_id,
EncryptionPolicy* policy) {
auto refi = key_map.find(user_id);
if (refi == key_map.end()) {
return false;
}
*policy = refi->second;
return true;
}
static bool is_numeric(const char* name) {
for (const char* p = name; *p != '\0'; p++) {
if (!isdigit(*p)) return false;
}
return true;
}
static bool load_all_de_keys() {
auto de_dir = user_key_dir + "/de";
auto dirp = std::unique_ptr<DIR, int (*)(DIR*)>(opendir(de_dir.c_str()), closedir);
if (!dirp) {
PLOG(ERROR) << "Unable to read de key directory";
return false;
}
for (;;) {
errno = 0;
auto entry = readdir(dirp.get());
if (!entry) {
if (errno) {
PLOG(ERROR) << "Unable to read de key directory";
return false;
}
break;
}
if (IsDotOrDotDot(*entry)) continue;
if (entry->d_type != DT_DIR || !is_numeric(entry->d_name)) {
LOG(DEBUG) << "Skipping non-de-key " << entry->d_name;
continue;
}
userid_t user_id = std::stoi(entry->d_name);
auto key_path = de_dir + "/" + entry->d_name;
KeyBuffer de_key;
if (!retrieveKey(key_path, kEmptyAuthentication, &de_key)) {
// This is probably a partially removed user, so ignore
if (user_id != 0) continue;
return false;
}
EncryptionPolicy de_policy;
if (!install_storage_key(DATA_MNT_POINT, s_data_options, de_key, &de_policy)) return false;
auto ret = s_de_policies.insert({user_id, de_policy});
if (!ret.second && ret.first->second != de_policy) {
LOG(ERROR) << "DE policy for user" << user_id << " changed";
return false;
}
LOG(DEBUG) << "Installed de key for user " << user_id;
}
// fscrypt:TODO: go through all DE directories, ensure that all user dirs have the
// correct policy set on them, and that no rogue ones exist.
return true;
}
// Attempt to reinstall CE keys for users that we think are unlocked.
static bool try_reload_ce_keys() {
for (const auto& it : s_ce_policies) {
if (!android::vold::reloadKeyFromSessionKeyring(DATA_MNT_POINT, it.second)) {
LOG(ERROR) << "Failed to load CE key from session keyring for user " << it.first;
return false;
}
}
return true;
}
bool fscrypt_initialize_systemwide_keys() {
LOG(INFO) << "fscrypt_initialize_systemwide_keys";
if (!init_data_file_encryption_options()) return false;
KeyBuffer device_key;
if (!retrieveOrGenerateKey(device_key_path, device_key_temp, kEmptyAuthentication,
makeGen(s_data_options), &device_key))
return false;
// This initializes s_device_policy, which is a global variable so that
// fscrypt_init_user0() can access it later.
if (!install_storage_key(DATA_MNT_POINT, s_data_options, device_key, &s_device_policy))
return false;
std::string options_string;
if (!OptionsToString(s_device_policy.options, &options_string)) {
LOG(ERROR) << "Unable to serialize options";
return false;
}
std::string options_filename = std::string(DATA_MNT_POINT) + fscrypt_key_mode;
if (!android::vold::writeStringToFile(options_string, options_filename)) return false;
std::string ref_filename = std::string(DATA_MNT_POINT) + fscrypt_key_ref;
if (!android::vold::writeStringToFile(s_device_policy.key_raw_ref, ref_filename)) return false;
LOG(INFO) << "Wrote system DE key reference to:" << ref_filename;
KeyBuffer per_boot_key;
if (!generateStorageKey(makeGen(s_data_options), &per_boot_key)) return false;
EncryptionPolicy per_boot_policy;
if (!install_storage_key(DATA_MNT_POINT, s_data_options, per_boot_key, &per_boot_policy))
return false;
std::string per_boot_ref_filename = std::string("/data") + fscrypt_key_per_boot_ref;
if (!android::vold::writeStringToFile(per_boot_policy.key_raw_ref, per_boot_ref_filename))
return false;
LOG(INFO) << "Wrote per boot key reference to:" << per_boot_ref_filename;
return true;
}
static bool prepare_special_dirs() {
// Ensure that /data/data and its "alias" /data/user/0 exist, and create the
// bind mount of /data/data onto /data/user/0. This *should* happen in
// fscrypt_prepare_user_storage(). However, it actually must be done early,
// before the rest of user 0's CE storage is prepared. This is because
// zygote may need to set up app data isolation before then, which requires
// mounting a tmpfs over /data/data to ensure it remains hidden. This issue
// arises due to /data/data being in the top-level directory.
// /data/user/0 used to be a symlink to /data/data, so we must first delete
// the old symlink if present.
if (android::vold::IsSymlink(data_user_0_dir) && android::vold::Unlink(data_user_0_dir) != 0)
return false;
// On first boot, we'll be creating /data/data for the first time, and user
// 0's CE key will be installed already since it was just created. Take the
// opportunity to also set the encryption policy of /data/data right away.
EncryptionPolicy ce_policy;
if (lookup_policy(s_ce_policies, 0, &ce_policy)) {
if (!prepare_dir_with_policy(data_data_dir, 0771, AID_SYSTEM, AID_SYSTEM, ce_policy)) {
// Preparing /data/data failed, yet we had just generated a new CE
// key because one wasn't stored. Before erroring out, try deleting
// the directory and retrying, as it's possible that the directory
// exists with different CE policy from an interrupted first boot.
if (rmdir(data_data_dir.c_str()) != 0) {
PLOG(ERROR) << "rmdir " << data_data_dir << " failed";
}
if (!prepare_dir_with_policy(data_data_dir, 0771, AID_SYSTEM, AID_SYSTEM, ce_policy))
return false;
}
} else {
if (!prepare_dir(data_data_dir, 0771, AID_SYSTEM, AID_SYSTEM)) return false;
// EnsurePolicy() will have to happen later, in fscrypt_prepare_user_storage().
}
if (!prepare_dir(data_user_0_dir, 0700, AID_SYSTEM, AID_SYSTEM)) return false;
if (android::vold::BindMount(data_data_dir, data_user_0_dir) != 0) return false;
// If /data/media/obb doesn't exist, create it and encrypt it with the
// device policy. Normally, device-policy-encrypted directories are created
// and encrypted by init; /data/media/obb is special because it is located
// in /data/media. Since /data/media also contains per-user encrypted
// directories, by design only vold can write to it. As a side effect of
// that, vold must create /data/media/obb.
//
// We must tolerate /data/media/obb being unencrypted if it already exists
// on-disk, since it used to be unencrypted (b/64566063).
if (android::vold::pathExists(media_obb_dir)) {
if (!prepare_dir(media_obb_dir, 0770, AID_MEDIA_RW, AID_MEDIA_RW)) return false;
} else {
if (!prepare_dir_with_policy(media_obb_dir, 0770, AID_MEDIA_RW, AID_MEDIA_RW,
s_device_policy))
return false;
}
return true;
}
bool fscrypt_init_user0_done;
bool fscrypt_init_user0() {
LOG(DEBUG) << "fscrypt_init_user0";
if (IsFbeEnabled()) {
if (!prepare_dir(user_key_dir, 0700, AID_ROOT, AID_ROOT)) return false;
if (!prepare_dir(user_key_dir + "/ce", 0700, AID_ROOT, AID_ROOT)) return false;
if (!prepare_dir(user_key_dir + "/de", 0700, AID_ROOT, AID_ROOT)) return false;
// Create user 0's DE and CE keys if they don't already exist. Check
// each key independently, since if the first boot was interrupted it is
// possible that the DE key exists but the CE key does not.
if (!de_key_exists(0) && !create_de_key(0, false)) return false;
if (!ce_key_exists(0) && !create_ce_key(0, false)) return false;
// TODO: switch to loading only DE_0 here once framework makes
// explicit calls to install DE keys for secondary users
if (!load_all_de_keys()) return false;
}
// Now that user 0's CE key has been created, we can prepare /data/data.
if (!prepare_special_dirs()) return false;
// With the exception of what is done by prepare_special_dirs() above, we
// only prepare DE storage here, since user 0's CE key won't be installed
// yet unless it was just created. The framework will prepare the user's CE
// storage later, once their CE key is installed.
if (!fscrypt_prepare_user_storage("", 0, 0, android::os::IVold::STORAGE_FLAG_DE)) {
LOG(ERROR) << "Failed to prepare user 0 storage";
return false;
}
// In some scenarios (e.g. userspace reboot) we might unmount userdata
// without doing a hard reboot. If CE keys were stored in fs keyring then
// they will be lost after unmount. Attempt to re-install them.
if (IsFbeEnabled() && android::vold::isFsKeyringSupported()) {
if (!try_reload_ce_keys()) return false;
}
fscrypt_init_user0_done = true;
return true;
}
bool fscrypt_vold_create_user_key(userid_t user_id, int serial, bool ephemeral) {
LOG(DEBUG) << "fscrypt_vold_create_user_key for " << user_id << " serial " << serial;
if (!IsFbeEnabled()) {
return true;
}
// FIXME test for existence of key that is not loaded yet
if (s_ce_policies.count(user_id) != 0) {
LOG(ERROR) << "Already exists, can't fscrypt_vold_create_user_key for " << user_id
<< " serial " << serial;
// FIXME should we fail the command?
return true;
}
if (!create_de_key(user_id, ephemeral)) return false;
if (!create_ce_key(user_id, ephemeral)) return false;
if (ephemeral) s_ephemeral_users.insert(user_id);
return true;
}
// "Lock" all encrypted directories whose key has been removed. This is needed
// in the case where the keys are being put in the session keyring (rather in
// the newer filesystem-level keyrings), because removing a key from the session
// keyring doesn't affect inodes in the kernel's inode cache whose per-file key
// was already set up. So to remove the per-file keys and make the files
// "appear encrypted", these inodes must be evicted.
//
// To do this, sync() to clean all dirty inodes, then drop all reclaimable slab
// objects systemwide. This is overkill, but it's the best available method
// currently. Don't use drop_caches mode "3" because that also evicts pagecache
// for in-use files; all files relevant here are already closed and sync'ed.
static void drop_caches_if_needed() {
if (android::vold::isFsKeyringSupported()) {
return;
}
sync();
if (!writeStringToFile("2", "/proc/sys/vm/drop_caches")) {
PLOG(ERROR) << "Failed to drop caches during key eviction";
}
}
static bool evict_ce_key(userid_t user_id) {
bool success = true;
EncryptionPolicy policy;
// If we haven't loaded the CE key, no need to evict it.
if (lookup_policy(s_ce_policies, user_id, &policy)) {
success &= android::vold::evictKey(DATA_MNT_POINT, policy);
drop_caches_if_needed();
}
s_ce_policies.erase(user_id);
s_new_ce_keys.erase(user_id);
return success;
}
bool fscrypt_destroy_user_key(userid_t user_id) {
LOG(DEBUG) << "fscrypt_destroy_user_key(" << user_id << ")";
if (!IsFbeEnabled()) {
return true;
}
bool success = true;
success &= evict_ce_key(user_id);
EncryptionPolicy de_policy;
success &= lookup_policy(s_de_policies, user_id, &de_policy) &&
android::vold::evictKey(DATA_MNT_POINT, de_policy);
s_de_policies.erase(user_id);
if (!s_ephemeral_users.erase(user_id)) {
auto ce_path = get_ce_key_directory_path(user_id);
if (!s_new_ce_keys.erase(user_id)) {
for (auto const path : get_ce_key_paths(ce_path)) {
success &= android::vold::destroyKey(path);
}
}
s_deferred_fixations.erase(ce_path);
success &= destroy_dir(ce_path);
auto de_key_path = get_de_key_path(user_id);
if (android::vold::pathExists(de_key_path)) {
success &= android::vold::destroyKey(de_key_path);
} else {
LOG(INFO) << "Not present so not erasing: " << de_key_path;
}
}
return success;
}
static bool parse_hex(const std::string& hex, std::string* result) {
if (hex == "!") {
*result = "";
return true;
}
if (android::vold::HexToStr(hex, *result) != 0) {
LOG(ERROR) << "Invalid FBE hex string"; // Don't log the string for security reasons
return false;
}
return true;
}
static std::optional<android::vold::KeyAuthentication> authentication_from_hex(
const std::string& secret_hex) {
std::string secret;
if (!parse_hex(secret_hex, &secret)) return std::optional<android::vold::KeyAuthentication>();
if (secret.empty()) {
return kEmptyAuthentication;
} else {
return android::vold::KeyAuthentication(secret);
}
}
static std::string volkey_path(const std::string& misc_path, const std::string& volume_uuid) {
return misc_path + "/vold/volume_keys/" + volume_uuid + "/default";
}
static std::string volume_secdiscardable_path(const std::string& volume_uuid) {
return systemwide_volume_key_dir + "/" + volume_uuid + "/secdiscardable";
}
static bool read_or_create_volkey(const std::string& misc_path, const std::string& volume_uuid,
EncryptionPolicy* policy) {
auto secdiscardable_path = volume_secdiscardable_path(volume_uuid);
std::string secdiscardable_hash;
if (android::vold::pathExists(secdiscardable_path)) {
if (!android::vold::readSecdiscardable(secdiscardable_path, &secdiscardable_hash))
return false;
} else {
if (!android::vold::MkdirsSync(secdiscardable_path, 0700)) return false;
if (!android::vold::createSecdiscardable(secdiscardable_path, &secdiscardable_hash))
return false;
}
auto key_path = volkey_path(misc_path, volume_uuid);
if (!android::vold::MkdirsSync(key_path, 0700)) return false;
android::vold::KeyAuthentication auth(secdiscardable_hash);
EncryptionOptions options;
if (!get_volume_file_encryption_options(&options)) return false;
KeyBuffer key;
if (!retrieveOrGenerateKey(key_path, key_path + "_tmp", auth, makeGen(options), &key))
return false;
if (!install_storage_key(BuildDataPath(volume_uuid), options, key, policy)) return false;
return true;
}
static bool destroy_volkey(const std::string& misc_path, const std::string& volume_uuid) {
auto path = volkey_path(misc_path, volume_uuid);
if (!android::vold::pathExists(path)) return true;
return android::vold::destroyKey(path);
}
// (Re-)encrypts the user's CE key with the given secret. This function handles
// storing the CE key for a new user for the first time. It also handles
// re-encrypting the CE key upon upgrade from an Android version where the CE
// key was stored with kEmptyAuthentication when the user didn't have an LSKF.
// See the comments below for the different cases handled.
bool fscrypt_set_user_key_protection(userid_t user_id, const std::string& secret_hex) {
LOG(DEBUG) << "fscrypt_set_user_key_protection " << user_id;
if (!IsFbeEnabled()) return true;
auto auth = authentication_from_hex(secret_hex);
if (!auth) return false;
if (auth->secret.empty()) {
LOG(ERROR) << "fscrypt_set_user_key_protection: secret must be nonempty";
return false;
}
// We shouldn't store any keys for ephemeral users.
if (s_ephemeral_users.count(user_id) != 0) {
LOG(DEBUG) << "Not storing key because user is ephemeral";
return true;
}
KeyBuffer ce_key;
auto it = s_new_ce_keys.find(user_id);
if (it != s_new_ce_keys.end()) {
// If the key exists in s_new_ce_keys, then the key is a
// not-yet-committed key for a new user, and we are committing it here.
// This happens when the user's synthetic password is created.
ce_key = it->second;
} else if (ce_key_exists(user_id)) {
// If the key doesn't exist in s_new_ce_keys but does exist on-disk,
// then we are setting the protection on an existing key. This happens
// at upgrade time, when CE keys that were previously protected by
// kEmptyAuthentication are encrypted by the user's synthetic password.
LOG(DEBUG) << "CE key already exists on-disk; re-protecting it with the given secret";
if (!read_and_fixate_user_ce_key(user_id, kEmptyAuthentication, &ce_key)) {
LOG(ERROR) << "Failed to retrieve CE key for user " << user_id << " using empty auth";
// Before failing, also check whether the key is already protected
// with the given secret. This isn't expected, but in theory it
// could happen if an upgrade is requested for a user more than once
// due to a power-off or other interruption.
if (read_and_fixate_user_ce_key(user_id, *auth, &ce_key)) {
LOG(WARNING) << "CE key is already protected by given secret";
return true;
}
// The key isn't protected by either kEmptyAuthentication or by
// |auth|. This should never happen, and there's nothing we can do
// besides return an error.
return false;
}
} else {
// If the key doesn't exist in memory or on-disk, then we need to
// generate it here, then commit it to disk. This is needed after the
// unusual case where a non-system user was created during early boot,
// and then the device was force-rebooted before the boot completed. In
// that case, the Android user record was committed but the CE key was
// not. So the CE key was lost, and we need to regenerate it. This
// should be fine, since the key should not have been used yet.
LOG(WARNING) << "CE key not found! Regenerating it";
if (!create_ce_key(user_id, false)) return false;
ce_key = s_new_ce_keys.find(user_id)->second;
}
auto const directory_path = get_ce_key_directory_path(user_id);
auto const paths = get_ce_key_paths(directory_path);
std::string ce_key_path;
if (!get_ce_key_new_path(directory_path, paths, &ce_key_path)) return false;
if (!android::vold::storeKeyAtomically(ce_key_path, user_key_temp, *auth, ce_key)) return false;
// Fixate the key, i.e. delete all other bindings of it. (In practice this
// just means the kEmptyAuthentication binding, if there is one.) However,
// if a userdata filesystem checkpoint is pending, then we need to delay the
// fixation until the checkpoint has been committed, since deleting keys
// from Keystore cannot be rolled back.
if (android::vold::cp_needsCheckpoint()) {
LOG(INFO) << "Deferring fixation of " << directory_path << " until checkpoint is committed";
s_deferred_fixations[directory_path] = ce_key_path;
} else {
s_deferred_fixations.erase(directory_path);
if (!fixate_user_ce_key(directory_path, ce_key_path, paths)) return false;
}
if (s_new_ce_keys.erase(user_id)) {
LOG(INFO) << "Stored CE key for new user " << user_id;
}
return true;
}
void fscrypt_deferred_fixate_ce_keys() {
for (const auto& it : s_deferred_fixations) {
const auto& directory_path = it.first;
const auto& to_fix = it.second;
LOG(INFO) << "Doing deferred fixation of " << directory_path;
fixate_user_ce_key(directory_path, to_fix, get_ce_key_paths(directory_path));
// Continue on error.
}
s_deferred_fixations.clear();
}
std::vector<int> fscrypt_get_unlocked_users() {
std::vector<int> user_ids;
for (const auto& it : s_ce_policies) {
user_ids.push_back(it.first);
}
return user_ids;
}
// TODO: rename to 'install' for consistency, and take flags to know which keys to install
bool fscrypt_unlock_user_key(userid_t user_id, int serial, const std::string& secret_hex) {
LOG(DEBUG) << "fscrypt_unlock_user_key " << user_id << " serial=" << serial;
if (IsFbeEnabled()) {
if (s_ce_policies.count(user_id) != 0) {
LOG(WARNING) << "Tried to unlock already-unlocked key for user " << user_id;
return true;
}
auto auth = authentication_from_hex(secret_hex);
if (!auth) return false;
if (!read_and_install_user_ce_key(user_id, *auth)) {
LOG(ERROR) << "Couldn't read key for " << user_id;
return false;
}
}
return true;
}
// TODO: rename to 'evict' for consistency
bool fscrypt_lock_user_key(userid_t user_id) {
LOG(DEBUG) << "fscrypt_lock_user_key " << user_id;
if (IsFbeEnabled()) {
return evict_ce_key(user_id);
}
return true;
}
static bool prepare_subdirs(const std::string& action, const std::string& volume_uuid,
userid_t user_id, int flags) {
if (0 != android::vold::ForkExecvp(
std::vector<std::string>{prepare_subdirs_path, action, volume_uuid,
std::to_string(user_id), std::to_string(flags)})) {
LOG(ERROR) << "vold_prepare_subdirs failed";
return false;
}
return true;
}
bool fscrypt_prepare_user_storage(const std::string& volume_uuid, userid_t user_id, int serial,
int flags) {
LOG(DEBUG) << "fscrypt_prepare_user_storage for volume " << escape_empty(volume_uuid)
<< ", user " << user_id << ", serial " << serial << ", flags " << flags;
// Internal storage must be prepared before adoptable storage, since the
// user's volume keys are stored in their internal storage.
if (!volume_uuid.empty()) {
if ((flags & android::os::IVold::STORAGE_FLAG_DE) &&
!android::vold::pathExists(android::vold::BuildDataMiscDePath("", user_id))) {
LOG(ERROR) << "Cannot prepare DE storage for user " << user_id << " on volume "
<< volume_uuid << " before internal storage";
return false;
}
if ((flags & android::os::IVold::STORAGE_FLAG_CE) &&
!android::vold::pathExists(android::vold::BuildDataMiscCePath("", user_id))) {
LOG(ERROR) << "Cannot prepare CE storage for user " << user_id << " on volume "
<< volume_uuid << " before internal storage";
return false;
}
}
if (flags & android::os::IVold::STORAGE_FLAG_DE) {
// DE_sys key
auto system_legacy_path = android::vold::BuildDataSystemLegacyPath(user_id);
auto misc_legacy_path = android::vold::BuildDataMiscLegacyPath(user_id);
auto profiles_de_path = android::vold::BuildDataProfilesDePath(user_id);
// DE_n key
EncryptionPolicy de_policy;
auto system_de_path = android::vold::BuildDataSystemDePath(user_id);
auto misc_de_path = android::vold::BuildDataMiscDePath(volume_uuid, user_id);
auto vendor_de_path = android::vold::BuildDataVendorDePath(user_id);
auto user_de_path = android::vold::BuildDataUserDePath(volume_uuid, user_id);
if (IsFbeEnabled()) {
if (volume_uuid.empty()) {
if (!lookup_policy(s_de_policies, user_id, &de_policy)) {
LOG(ERROR) << "Cannot find DE policy for user " << user_id;
return false;
}
} else {
auto misc_de_empty_volume_path = android::vold::BuildDataMiscDePath("", user_id);
if (!read_or_create_volkey(misc_de_empty_volume_path, volume_uuid, &de_policy)) {
return false;
}
}
}
if (volume_uuid.empty()) {
if (!prepare_dir(system_legacy_path, 0700, AID_SYSTEM, AID_SYSTEM)) return false;
#if MANAGE_MISC_DIRS
if (!prepare_dir(misc_legacy_path, 0750, multiuser_get_uid(user_id, AID_SYSTEM),
multiuser_get_uid(user_id, AID_EVERYBODY)))
return false;
#endif
if (!prepare_dir(profiles_de_path, 0771, AID_SYSTEM, AID_SYSTEM)) return false;
if (!prepare_dir_with_policy(system_de_path, 0770, AID_SYSTEM, AID_SYSTEM, de_policy))
return false;
if (!prepare_dir_with_policy(vendor_de_path, 0771, AID_ROOT, AID_ROOT, de_policy))
return false;
}
if (!prepare_dir_with_policy(misc_de_path, 01771, AID_SYSTEM, AID_MISC, de_policy))
return false;
if (!prepare_dir_with_policy(user_de_path, 0771, AID_SYSTEM, AID_SYSTEM, de_policy))
return false;
}
if (flags & android::os::IVold::STORAGE_FLAG_CE) {
// CE_n key
EncryptionPolicy ce_policy;
auto system_ce_path = android::vold::BuildDataSystemCePath(user_id);
auto misc_ce_path = android::vold::BuildDataMiscCePath(volume_uuid, user_id);
auto vendor_ce_path = android::vold::BuildDataVendorCePath(user_id);
auto media_ce_path = android::vold::BuildDataMediaCePath(volume_uuid, user_id);
auto user_ce_path = android::vold::BuildDataUserCePath(volume_uuid, user_id);
if (IsFbeEnabled()) {
if (volume_uuid.empty()) {
if (!lookup_policy(s_ce_policies, user_id, &ce_policy)) {
LOG(ERROR) << "Cannot find CE policy for user " << user_id;
return false;
}
} else {
auto misc_ce_empty_volume_path = android::vold::BuildDataMiscCePath("", user_id);
if (!read_or_create_volkey(misc_ce_empty_volume_path, volume_uuid, &ce_policy)) {
return false;
}
}
}
if (volume_uuid.empty()) {
if (!prepare_dir_with_policy(system_ce_path, 0770, AID_SYSTEM, AID_SYSTEM, ce_policy))
return false;
if (!prepare_dir_with_policy(vendor_ce_path, 0771, AID_ROOT, AID_ROOT, ce_policy))
return false;
}
if (!prepare_dir_with_policy(media_ce_path, 02770, AID_MEDIA_RW, AID_MEDIA_RW, ce_policy))
return false;
// On devices without sdcardfs (kernel 5.4+), the path permissions aren't fixed
// up automatically; therefore, use a default ACL, to ensure apps with MEDIA_RW
// can keep reading external storage; in particular, this allows app cloning
// scenarios to work correctly on such devices.
int ret = SetDefaultAcl(media_ce_path, 02770, AID_MEDIA_RW, AID_MEDIA_RW, {AID_MEDIA_RW});
if (ret != android::OK) {
return false;
}
if (!prepare_dir_with_policy(misc_ce_path, 01771, AID_SYSTEM, AID_MISC, ce_policy))
return false;
if (!prepare_dir_with_policy(user_ce_path, 0771, AID_SYSTEM, AID_SYSTEM, ce_policy))
return false;
if (volume_uuid.empty()) {
// Now that credentials have been installed, we can run restorecon
// over these paths
// NOTE: these paths need to be kept in sync with libselinux
android::vold::RestoreconRecursive(system_ce_path);
android::vold::RestoreconRecursive(vendor_ce_path);
android::vold::RestoreconRecursive(misc_ce_path);
}
}
if (!prepare_subdirs("prepare", volume_uuid, user_id, flags)) return false;
return true;
}
bool fscrypt_destroy_user_storage(const std::string& volume_uuid, userid_t user_id, int flags) {
LOG(DEBUG) << "fscrypt_destroy_user_storage for volume " << escape_empty(volume_uuid)
<< ", user " << user_id << ", flags " << flags;
bool res = true;
res &= prepare_subdirs("destroy", volume_uuid, user_id, flags);
if (flags & android::os::IVold::STORAGE_FLAG_CE) {
// CE_n key
auto system_ce_path = android::vold::BuildDataSystemCePath(user_id);
auto misc_ce_path = android::vold::BuildDataMiscCePath(volume_uuid, user_id);
auto vendor_ce_path = android::vold::BuildDataVendorCePath(user_id);
auto media_ce_path = android::vold::BuildDataMediaCePath(volume_uuid, user_id);
auto user_ce_path = android::vold::BuildDataUserCePath(volume_uuid, user_id);
res &= destroy_dir(media_ce_path);
res &= destroy_dir(misc_ce_path);
res &= destroy_dir(user_ce_path);
if (volume_uuid.empty()) {
res &= destroy_dir(system_ce_path);
res &= destroy_dir(vendor_ce_path);
} else {
if (IsFbeEnabled()) {
auto misc_ce_empty_volume_path = android::vold::BuildDataMiscCePath("", user_id);
res &= destroy_volkey(misc_ce_empty_volume_path, volume_uuid);
}
}
}
if (flags & android::os::IVold::STORAGE_FLAG_DE) {
// DE_sys key
auto system_legacy_path = android::vold::BuildDataSystemLegacyPath(user_id);
auto misc_legacy_path = android::vold::BuildDataMiscLegacyPath(user_id);
auto profiles_de_path = android::vold::BuildDataProfilesDePath(user_id);
// DE_n key
auto system_de_path = android::vold::BuildDataSystemDePath(user_id);
auto misc_de_path = android::vold::BuildDataMiscDePath(volume_uuid, user_id);
auto vendor_de_path = android::vold::BuildDataVendorDePath(user_id);
auto user_de_path = android::vold::BuildDataUserDePath(volume_uuid, user_id);
res &= destroy_dir(user_de_path);
res &= destroy_dir(misc_de_path);
if (volume_uuid.empty()) {
res &= destroy_dir(system_legacy_path);
#if MANAGE_MISC_DIRS
res &= destroy_dir(misc_legacy_path);
#endif
res &= destroy_dir(profiles_de_path);
res &= destroy_dir(system_de_path);
res &= destroy_dir(vendor_de_path);
} else {
if (IsFbeEnabled()) {
auto misc_de_empty_volume_path = android::vold::BuildDataMiscDePath("", user_id);
res &= destroy_volkey(misc_de_empty_volume_path, volume_uuid);
}
}
}
return res;
}
static bool destroy_volume_keys(const std::string& directory_path, const std::string& volume_uuid) {
auto dirp = std::unique_ptr<DIR, int (*)(DIR*)>(opendir(directory_path.c_str()), closedir);
if (!dirp) {
PLOG(ERROR) << "Unable to open directory: " + directory_path;
return false;
}
bool res = true;
for (;;) {
errno = 0;
auto const entry = readdir(dirp.get());
if (!entry) {
if (errno) {
PLOG(ERROR) << "Unable to read directory: " + directory_path;
return false;
}
break;
}
if (IsDotOrDotDot(*entry)) continue;
if (entry->d_type != DT_DIR || entry->d_name[0] == '.') {
LOG(DEBUG) << "Skipping non-user " << entry->d_name;
continue;
}
res &= destroy_volkey(directory_path + "/" + entry->d_name, volume_uuid);
}
return res;
}
bool fscrypt_destroy_volume_keys(const std::string& volume_uuid) {
bool res = true;
LOG(DEBUG) << "fscrypt_destroy_volume_keys for volume " << escape_empty(volume_uuid);
auto secdiscardable_path = volume_secdiscardable_path(volume_uuid);
res &= android::vold::runSecdiscardSingle(secdiscardable_path);
res &= destroy_volume_keys("/data/misc_ce", volume_uuid);
res &= destroy_volume_keys("/data/misc_de", volume_uuid);
return res;
}