blob: fdc0197c6e0ede067995e9ea3378ccfd73df6ddd [file] [log] [blame]
/*
* 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 "Ext4Crypt.h"
#include "KeyStorage.h"
#include "Utils.h"
#include <iomanip>
#include <map>
#include <set>
#include <string>
#include <sstream>
#include <stdio.h>
#include <errno.h>
#include <dirent.h>
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <cutils/properties.h>
#include <openssl/sha.h>
#include <selinux/android.h>
#include <private/android_filesystem_config.h>
#include "key_control.h"
#include "cryptfs.h"
#include "ext4_crypt.h"
#define EMULATED_USES_SELINUX 0
#include <cutils/fs.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/stringprintf.h>
using android::base::StringPrintf;
using android::vold::kEmptyAuthentication;
// NOTE: keep in sync with StorageManager
static constexpr int FLAG_STORAGE_DE = 1 << 0;
static constexpr int FLAG_STORAGE_CE = 1 << 1;
namespace {
const std::string device_key_dir = std::string() + DATA_MNT_POINT + "/unencrypted";
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";
bool s_global_de_initialized = false;
// Some users are ephemeral, don't try to wipe their keys from disk
std::set<userid_t> s_ephemeral_users;
// Map user ids to key references
std::map<userid_t, std::string> s_de_key_raw_refs;
std::map<userid_t, std::string> s_ce_key_raw_refs;
// TODO abolish this map. Keys should not be long-lived in user memory, only kernel memory.
// See b/26948053
std::map<userid_t, std::string> s_ce_keys;
// ext4enc:TODO get this const from somewhere good
const int EXT4_KEY_DESCRIPTOR_SIZE = 8;
// ext4enc:TODO Include structure from somewhere sensible
// MUST be in sync with ext4_crypto.c in kernel
constexpr int EXT4_ENCRYPTION_MODE_AES_256_XTS = 1;
constexpr int EXT4_AES_256_XTS_KEY_SIZE = 64;
constexpr int EXT4_MAX_KEY_SIZE = 64;
struct ext4_encryption_key {
uint32_t mode;
char raw[EXT4_MAX_KEY_SIZE];
uint32_t size;
};
}
// TODO replace with proper function to test for file encryption
bool e4crypt_is_native() {
char value[PROPERTY_VALUE_MAX];
property_get("ro.crypto.type", value, "none");
return !strcmp(value, "file");
}
static bool e4crypt_is_emulated() {
return property_get_bool("persist.sys.emulate_fbe", false);
}
static const char* escape_null(const char* value) {
return (value == nullptr) ? "null" : value;
}
// Get raw keyref - used to make keyname and to pass to ioctl
static std::string generate_key_ref(const char* key, int length)
{
SHA512_CTX c;
SHA512_Init(&c);
SHA512_Update(&c, key, length);
unsigned char key_ref1[SHA512_DIGEST_LENGTH];
SHA512_Final(key_ref1, &c);
SHA512_Init(&c);
SHA512_Update(&c, key_ref1, SHA512_DIGEST_LENGTH);
unsigned char key_ref2[SHA512_DIGEST_LENGTH];
SHA512_Final(key_ref2, &c);
return std::string((char*)key_ref2, EXT4_KEY_DESCRIPTOR_SIZE);
}
static bool fill_key(const std::string& key, ext4_encryption_key& ext4_key)
{
if (key.size() != EXT4_AES_256_XTS_KEY_SIZE) {
LOG(ERROR) << "Wrong size key " << key.size();
return false;
}
static_assert(EXT4_AES_256_XTS_KEY_SIZE <= sizeof(ext4_key.raw),
"Key too long!");
ext4_key.mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
ext4_key.size = key.size();
memset(ext4_key.raw, 0, sizeof(ext4_key.raw));
memcpy(ext4_key.raw, key.data(), key.size());
return true;
}
static std::string keyname(const std::string &raw_ref)
{
std::ostringstream o;
o << "ext4:";
for (auto i = raw_ref.begin(); i != raw_ref.end(); ++i) {
o << std::hex << std::setw(2) << std::setfill('0') << (int)*i;
}
return o.str();
}
// Get the keyring we store all keys in
static key_serial_t e4crypt_keyring()
{
return keyctl_search(KEY_SPEC_SESSION_KEYRING, "keyring", "e4crypt", 0);
}
// Install password into global keyring
// Return raw key reference for use in policy
static bool install_key(const std::string &key, std::string &raw_ref)
{
ext4_encryption_key ext4_key;
if (!fill_key(key, ext4_key)) return false;
raw_ref = generate_key_ref(ext4_key.raw, ext4_key.size);
auto ref = keyname(raw_ref);
key_serial_t device_keyring = e4crypt_keyring();
key_serial_t key_id = add_key("logon", ref.c_str(),
(void*)&ext4_key, sizeof(ext4_key),
device_keyring);
if (key_id == -1) {
PLOG(ERROR) << "Failed to insert key into keyring " << device_keyring;
return false;
}
LOG(INFO) << "Added key " << key_id << " (" << ref << ") to keyring "
<< device_keyring << " in process " << getpid();
return true;
}
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_path(userid_t user_id) {
return StringPrintf("%s/ce/%d/current", user_key_dir.c_str(), user_id);
}
static bool read_and_install_user_ce_key(
userid_t user_id, const android::vold::KeyAuthentication &auth) {
if (s_ce_key_raw_refs.count(user_id) != 0) return true;
const auto ce_key_path = get_ce_key_path(user_id);
std::string ce_key;
if (!android::vold::retrieveKey(ce_key_path, auth, ce_key)) return false;
std::string ce_raw_ref;
if (!install_key(ce_key, ce_raw_ref)) return false;
s_ce_keys[user_id] = ce_key;
s_ce_key_raw_refs[user_id] = ce_raw_ref;
LOG(DEBUG) << "Installed ce key for user " << user_id;
return true;
}
static bool prepare_dir(const std::string &dir, mode_t mode, uid_t uid, gid_t gid) {
LOG(DEBUG) << "Preparing: " << dir;
if (fs_prepare_dir(dir.c_str(), mode, uid, gid) != 0) {
PLOG(ERROR) << "Failed to prepare " << dir;
return false;
}
return true;
}
static bool random_key(std::string &key) {
if (android::vold::ReadRandomBytes(EXT4_AES_256_XTS_KEY_SIZE, key) != 0) {
// TODO status_t plays badly with PLOG, fix it.
LOG(ERROR) << "Random read failed";
return false;
}
return true;
}
static bool path_exists(const std::string &path) {
return access(path.c_str(), F_OK) == 0;
}
// NB this assumes that there is only one thread listening for crypt commands, because
// it creates keys in a fixed location.
static bool store_key(const std::string &key_path, const std::string &tmp_path,
const android::vold::KeyAuthentication &auth, const std::string &key) {
if (path_exists(key_path)) {
LOG(ERROR) << "Already exists, cannot create key at: " << key_path;
return false;
}
if (path_exists(tmp_path)) {
android::vold::destroyKey(tmp_path);
}
if (!android::vold::storeKey(tmp_path, auth, key)) return false;
if (rename(tmp_path.c_str(), key_path.c_str()) != 0) {
PLOG(ERROR) << "Unable to move new key to location: " << key_path;
return false;
}
LOG(DEBUG) << "Created key " << key_path;
return true;
}
static bool create_and_install_user_keys(userid_t user_id, bool create_ephemeral) {
std::string de_key, ce_key;
if (!random_key(de_key)) return false;
if (!random_key(ce_key)) return false;
if (create_ephemeral) {
// If the key should be created as ephemeral, don't store it.
s_ephemeral_users.insert(user_id);
} else {
if (!store_key(get_de_key_path(user_id), user_key_temp,
kEmptyAuthentication, de_key)) return false;
if (!prepare_dir(user_key_dir + "/ce/" + std::to_string(user_id),
0700, AID_ROOT, AID_ROOT)) return false;
if (!store_key(get_ce_key_path(user_id), user_key_temp,
kEmptyAuthentication, ce_key)) return false;
}
std::string de_raw_ref;
if (!install_key(de_key, de_raw_ref)) return false;
s_de_key_raw_refs[user_id] = de_raw_ref;
std::string ce_raw_ref;
if (!install_key(ce_key, ce_raw_ref)) return false;
s_ce_keys[user_id] = ce_key;
s_ce_key_raw_refs[user_id] = ce_raw_ref;
LOG(DEBUG) << "Created keys for user " << user_id;
return true;
}
static bool lookup_key_ref(const std::map<userid_t, std::string> &key_map,
userid_t user_id, std::string &raw_ref) {
auto refi = key_map.find(user_id);
if (refi == key_map.end()) {
LOG(ERROR) << "Cannot find key for " << user_id;
return false;
}
raw_ref = refi->second;
return true;
}
static bool ensure_policy(const std::string &raw_ref, const std::string& path) {
if (e4crypt_policy_ensure(path.c_str(), raw_ref.data(), raw_ref.size()) != 0) {
LOG(ERROR) << "Failed to set policy on: " << path;
return false;
}
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 (entry->d_type != DT_DIR || !is_numeric(entry->d_name)) {
LOG(DEBUG) << "Skipping non-de-key " << entry->d_name;
continue;
}
userid_t user_id = atoi(entry->d_name);
if (s_de_key_raw_refs.count(user_id) == 0) {
auto key_path = de_dir + "/" + entry->d_name;
std::string key;
if (!android::vold::retrieveKey(key_path, kEmptyAuthentication, key)) return false;
std::string raw_ref;
if (!install_key(key, raw_ref)) return false;
s_de_key_raw_refs[user_id] = raw_ref;
LOG(DEBUG) << "Installed de key for user " << user_id;
}
}
// ext4enc: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;
}
bool e4crypt_initialize_global_de()
{
LOG(INFO) << "e4crypt_initialize_global_de";
if (s_global_de_initialized) {
LOG(INFO) << "Already initialized";
return true;
}
std::string device_key;
if (path_exists(device_key_path)) {
if (!android::vold::retrieveKey(device_key_path,
kEmptyAuthentication, device_key)) return false;
} else {
LOG(INFO) << "Creating new key";
if (!random_key(device_key)) return false;
if (!store_key(device_key_path, device_key_temp,
kEmptyAuthentication, device_key)) return false;
}
std::string device_key_ref;
if (!install_key(device_key, device_key_ref)) {
LOG(ERROR) << "Failed to install device key";
return false;
}
std::string ref_filename = std::string("/data") + e4crypt_key_ref;
if (!android::base::WriteStringToFile(device_key_ref, ref_filename)) {
PLOG(ERROR) << "Cannot save key reference";
return false;
}
s_global_de_initialized = true;
return true;
}
bool e4crypt_init_user0() {
LOG(DEBUG) << "e4crypt_init_user0";
if (e4crypt_is_native()) {
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;
auto de_path = get_de_key_path(0);
auto ce_path = get_ce_key_path(0);
if (!path_exists(de_path) || !path_exists(ce_path)) {
if (path_exists(de_path)) {
android::vold::destroyKey(de_path); // Ignore failure
}
if (path_exists(ce_path)) {
android::vold::destroyKey(ce_path); // Ignore failure
}
if (!create_and_install_user_keys(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;
}
// We can only safely prepare DE storage here, since CE keys are probably
// entangled with user credentials. The framework will always prepare CE
// storage once CE keys are installed.
if (!e4crypt_prepare_user_storage(nullptr, 0, 0, FLAG_STORAGE_DE)) {
LOG(ERROR) << "Failed to prepare user 0 storage";
return false;
}
// If this is a non-FBE device that recently left an emulated mode,
// restore user data directories to known-good state.
if (!e4crypt_is_native() && !e4crypt_is_emulated()) {
e4crypt_unlock_user_key(0, 0, "!", "!");
}
return true;
}
bool e4crypt_vold_create_user_key(userid_t user_id, int serial, bool ephemeral) {
LOG(DEBUG) << "e4crypt_vold_create_user_key for " << user_id << " serial " << serial;
if (!e4crypt_is_native()) {
return true;
}
// FIXME test for existence of key that is not loaded yet
if (s_ce_key_raw_refs.count(user_id) != 0) {
LOG(ERROR) << "Already exists, can't e4crypt_vold_create_user_key for "
<< user_id << " serial " << serial;
// FIXME should we fail the command?
return true;
}
if (!create_and_install_user_keys(user_id, ephemeral)) {
return false;
}
// TODO: create second key for user_de data
return true;
}
static bool evict_key(const std::string &raw_ref) {
auto ref = keyname(raw_ref);
auto key_serial = keyctl_search(e4crypt_keyring(), "logon", ref.c_str(), 0);
if (keyctl_revoke(key_serial) != 0) {
PLOG(ERROR) << "Failed to revoke key with serial " << key_serial << " ref " << ref;
return false;
}
LOG(DEBUG) << "Revoked key with serial " << key_serial << " ref " << ref;
return true;
}
bool e4crypt_destroy_user_key(userid_t user_id) {
LOG(DEBUG) << "e4crypt_destroy_user_key(" << user_id << ")";
if (!e4crypt_is_native()) {
return true;
}
bool success = true;
s_ce_keys.erase(user_id);
std::string raw_ref;
success &= lookup_key_ref(s_ce_key_raw_refs, user_id, raw_ref) && evict_key(raw_ref);
s_ce_key_raw_refs.erase(user_id);
success &= lookup_key_ref(s_de_key_raw_refs, user_id, raw_ref) && evict_key(raw_ref);
s_de_key_raw_refs.erase(user_id);
auto it = s_ephemeral_users.find(user_id);
if (it != s_ephemeral_users.end()) {
s_ephemeral_users.erase(it);
} else {
success &= android::vold::destroyKey(get_ce_key_path(user_id));
success &= android::vold::destroyKey(get_de_key_path(user_id));
}
return success;
}
static bool emulated_lock(const std::string& path) {
if (chmod(path.c_str(), 0000) != 0) {
PLOG(ERROR) << "Failed to chmod " << path;
return false;
}
#if EMULATED_USES_SELINUX
if (setfilecon(path.c_str(), "u:object_r:storage_stub_file:s0") != 0) {
PLOG(WARNING) << "Failed to setfilecon " << path;
return false;
}
#endif
return true;
}
static bool emulated_unlock(const std::string& path, mode_t mode) {
if (chmod(path.c_str(), mode) != 0) {
PLOG(ERROR) << "Failed to chmod " << path;
// FIXME temporary workaround for b/26713622
if (e4crypt_is_emulated()) return false;
}
#if EMULATED_USES_SELINUX
if (selinux_android_restorecon(path.c_str(), SELINUX_ANDROID_RESTORECON_FORCE) != 0) {
PLOG(WARNING) << "Failed to restorecon " << path;
// FIXME temporary workaround for b/26713622
if (e4crypt_is_emulated()) return false;
}
#endif
return true;
}
static bool parse_hex(const char *hex, std::string &result) {
if (strcmp("!", hex) == 0) {
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;
}
bool e4crypt_change_user_key(userid_t user_id, int serial,
const char* token_hex, const char* old_secret_hex, const char* new_secret_hex) {
LOG(DEBUG) << "e4crypt_change_user_key " << user_id << " serial=" << serial <<
" token_present=" << (strcmp(token_hex, "!") != 0);
if (!e4crypt_is_native()) return true;
if (s_ephemeral_users.count(user_id) != 0) return true;
std::string token, old_secret, new_secret;
if (!parse_hex(token_hex, token)) return false;
if (!parse_hex(old_secret_hex, old_secret)) return false;
if (!parse_hex(new_secret_hex, new_secret)) return false;
auto old_auth = old_secret.empty()
? kEmptyAuthentication
: android::vold::KeyAuthentication(token, old_secret);
auto new_auth = new_secret.empty()
? kEmptyAuthentication
: android::vold::KeyAuthentication(token, new_secret);
auto it = s_ce_keys.find(user_id);
if (it == s_ce_keys.end()) {
LOG(ERROR) << "Key not loaded into memory, can't change for user " << user_id;
return false;
}
auto ce_key = it->second;
auto ce_key_path = get_ce_key_path(user_id);
std::string trial_key;
if (!android::vold::retrieveKey(ce_key_path, old_auth, trial_key)) {
LOG(WARNING) << "change_user_key wasn't given enough info to reconstruct the key";
} else if (ce_key != trial_key) {
LOG(WARNING) << "Reconstructed key != stored key";
}
android::vold::destroyKey(ce_key_path);
if (!store_key(ce_key_path, user_key_temp, new_auth, ce_key)) return false;
return true;
}
// TODO: rename to 'install' for consistency, and take flags to know which keys to install
bool e4crypt_unlock_user_key(userid_t user_id, int serial,
const char* token_hex, const char* secret_hex) {
LOG(DEBUG) << "e4crypt_unlock_user_key " << user_id << " serial=" << serial <<
" token_present=" << (strcmp(token_hex, "!") != 0);
if (e4crypt_is_native()) {
if (s_ce_key_raw_refs.count(user_id) != 0) {
LOG(WARNING) << "Tried to unlock already-unlocked key for user " << user_id;
return true;
}
std::string token, secret;
if (!parse_hex(token_hex, token)) return false;
if (!parse_hex(secret_hex, secret)) return false;
android::vold::KeyAuthentication auth(token, secret);
if (!read_and_install_user_ce_key(user_id, auth)) {
LOG(ERROR) << "Couldn't read key for " << user_id;
return false;
}
} else {
// When in emulation mode, we just use chmod. However, we also
// unlock directories when not in emulation mode, to bring devices
// back into a known-good state.
if (!emulated_unlock(android::vold::BuildDataSystemCePath(user_id), 0771) ||
!emulated_unlock(android::vold::BuildDataMiscCePath(user_id), 01771) ||
!emulated_unlock(android::vold::BuildDataMediaPath(nullptr, user_id), 0770) ||
!emulated_unlock(android::vold::BuildDataUserPath(nullptr, user_id), 0771)) {
LOG(ERROR) << "Failed to unlock user " << user_id;
return false;
}
}
return true;
}
// TODO: rename to 'evict' for consistency
bool e4crypt_lock_user_key(userid_t user_id) {
if (e4crypt_is_native()) {
// TODO: remove from kernel keyring
} else if (e4crypt_is_emulated()) {
// When in emulation mode, we just use chmod
if (!emulated_lock(android::vold::BuildDataSystemCePath(user_id)) ||
!emulated_lock(android::vold::BuildDataMiscCePath(user_id)) ||
!emulated_lock(android::vold::BuildDataMediaPath(nullptr, user_id)) ||
!emulated_lock(android::vold::BuildDataUserPath(nullptr, user_id))) {
LOG(ERROR) << "Failed to lock user " << user_id;
return false;
}
}
return true;
}
bool e4crypt_prepare_user_storage(const char* volume_uuid, userid_t user_id,
int serial, int flags) {
LOG(DEBUG) << "e4crypt_prepare_user_storage for volume " << escape_null(volume_uuid)
<< ", user " << user_id << ", serial " << serial << ", flags " << flags;
if (flags & FLAG_STORAGE_DE) {
auto system_de_path = android::vold::BuildDataSystemDePath(user_id);
auto misc_de_path = android::vold::BuildDataMiscDePath(user_id);
auto user_de_path = android::vold::BuildDataUserDePath(volume_uuid, user_id);
if (!prepare_dir(system_de_path, 0770, AID_SYSTEM, AID_SYSTEM)) return false;
if (!prepare_dir(misc_de_path, 01771, AID_SYSTEM, AID_MISC)) return false;
if (!prepare_dir(user_de_path, 0771, AID_SYSTEM, AID_SYSTEM)) return false;
if (volume_uuid == nullptr) {
// Prepare profile directories only for the internal storage.
// For now, we do not store profiles on the adopted storage.
auto profiles_de_path = android::vold::BuildDataProfilesDePath(user_id);
auto foreign_dex_profiles_de_path =
android::vold::BuildDataProfilesForeignDexDePath(user_id);
if (!prepare_dir(profiles_de_path, 0771, AID_SYSTEM, AID_SYSTEM)) return false;
if (!prepare_dir(foreign_dex_profiles_de_path, 0773, AID_SYSTEM, AID_SYSTEM)) {
return false;
}
}
if (e4crypt_is_native()) {
std::string de_raw_ref;
if (!lookup_key_ref(s_de_key_raw_refs, user_id, de_raw_ref)) return false;
if (!ensure_policy(de_raw_ref, system_de_path)) return false;
if (!ensure_policy(de_raw_ref, misc_de_path)) return false;
if (!ensure_policy(de_raw_ref, user_de_path)) return false;
// No need to set the policy for profiles_de_path. The parent directory (/data/misc)
// already has a DE_sys policy set.
}
}
if (flags & FLAG_STORAGE_CE) {
auto system_ce_path = android::vold::BuildDataSystemCePath(user_id);
auto misc_ce_path = android::vold::BuildDataMiscCePath(user_id);
auto media_ce_path = android::vold::BuildDataMediaPath(volume_uuid, user_id);
auto user_ce_path = android::vold::BuildDataUserPath(volume_uuid, user_id);
if (!prepare_dir(system_ce_path, 0770, AID_SYSTEM, AID_SYSTEM)) return false;
if (!prepare_dir(misc_ce_path, 01771, AID_SYSTEM, AID_MISC)) return false;
if (!prepare_dir(media_ce_path, 0770, AID_MEDIA_RW, AID_MEDIA_RW)) return false;
if (!prepare_dir(user_ce_path, 0771, AID_SYSTEM, AID_SYSTEM)) return false;
if (e4crypt_is_native()) {
std::string ce_raw_ref;
if (!lookup_key_ref(s_ce_key_raw_refs, user_id, ce_raw_ref)) return false;
if (!ensure_policy(ce_raw_ref, system_ce_path)) return false;
if (!ensure_policy(ce_raw_ref, misc_ce_path)) return false;
if (!ensure_policy(ce_raw_ref, media_ce_path)) return false;
if (!ensure_policy(ce_raw_ref, user_ce_path)) return false;
}
}
return true;
}