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0b25b1d79b79bc4d45dfff2aaf575e10bd24ef2d
android_bootable_recovery/crypto/ext4crypt/Ext4CryptPie.cpp
Noah Jacobson 0b25b1d79b Add support for multi-user decryption 
* Add CLI support using the command "twrp decrypt <PASSWORD> [USER ID]"
* Add GUI support using the menu Advanced --> Decrypt User

Change-Id: Id2681bc2b1012a0571417f7a6e0b980b1b25c61c
(cherry picked from commit 5a79f67a1b1bd1bcadeca0a4896a871646652534)
2020-05-20 19:11:15 -04:00

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/*
* 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 "Ext4CryptPie.h"
#include "Keymaster4.h"
#include "KeyStorage4.h"
#include "KeyUtil.h"
#include "Utils.h"
#include "Decrypt.h"
//#include "VoldUtil.h"
#include <algorithm>
#include <map>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <limits.h>
#include <selinux/android.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <private/android_filesystem_config.h>
//#include "android/os/IVold.h"
//#include "cryptfs.h"
#define EMULATED_USES_SELINUX 0
#define MANAGE_MISC_DIRS 0
#include <cutils/fs.h>
#include <cutils/properties.h>
#include <ext4_utils/ext4_crypt.h>
#include <keyutils.h>
#include <android-base/file.h>
//#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/stringprintf.h>
#include <iostream>
#define LOG(x) std::cout
#define PLOG(x) std::cout
#define DATA_MNT_POINT "/data"
using android::base::StringPrintf;
using android::base::WriteStringToFile;
using android::vold::kEmptyAuthentication;
using android::vold::KeyBuffer;
using android::vold::Keymaster;
using android::hardware::keymaster::V4_0::KeyFormat;
// Store main DE raw ref / policy
std::string de_raw_ref;
// 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, per b/26948053
std::map<userid_t, KeyBuffer> s_ce_keys;
namespace {
struct PolicyKeyRef {
std::string contents_mode;
std::string filenames_mode;
std::string key_raw_ref;
};
const std::string device_key_dir = std::string() + DATA_MNT_POINT + e4crypt_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";
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;
}
static bool e4crypt_is_emulated() {
return property_get_bool("persist.sys.emulate_fbe", false);
}
/*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 << std::endl;
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 << std::endl;
return std::vector<std::string>();
}
break;
}
if (entry->d_type != DT_DIR || entry->d_name[0] != 'c') {
LOG(DEBUG) << "Skipping non-key " << entry->d_name << std::endl;
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";
}
// Discard all keys but the named one; rename it to canonical name.
// No point in acting on errors in this; ignore them.
static void fixate_user_ce_key(const std::string& directory_path, const std::string &to_fix,
const std::vector<std::string>& paths) {
for (auto const other_path: paths) {
if (other_path != to_fix) {
android::vold::destroyKey(other_path);
}
}
auto const current_path = get_ce_key_current_path(directory_path);
if (to_fix != current_path) {
LOG(DEBUG) << "Renaming " << to_fix << " to " << current_path << std::endl;
if (rename(to_fix.c_str(), current_path.c_str()) != 0) {
PLOG(WARNING) << "Unable to rename " << to_fix << " to " << current_path << std::endl;
}
}
}
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 << std::endl;
if (android::vold::retrieveKey(ce_key_path, auth, ce_key)) {
LOG(DEBUG) << "Successfully retrieved key" << std::endl;
fixate_user_ce_key(directory_path, ce_key_path, paths);
return true;
}
}
LOG(ERROR) << "Failed to find working ce key for user " << user_id << std::endl;
return false;
}
static bool is_wrapped_key_supported_common(const std::string& mount_point) {
LOG(DEBUG) << "Determining wrapped-key support for " << mount_point << std::endl;
std::string wrapped_key_supported = android::base::GetProperty("fbe.data.wrappedkey", "false");
LOG(DEBUG) << "fbe.data.wrappedkey = " << wrapped_key_supported << std::endl;
if (mount_point == DATA_MNT_POINT && wrapped_key_supported == "true") {
LOG(DEBUG) << "Wrapped key supported on " << mount_point << std::endl;
return true;
} else {
return false;
}
}
bool is_wrapped_key_supported() {
return is_wrapped_key_supported_common(DATA_MNT_POINT);
}
bool is_wrapped_key_supported_external() {
return false;
}
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;
KeyBuffer ce_key;
if (!read_and_fixate_user_ce_key(user_id, auth, &ce_key)) return false;
std::string ce_raw_ref;
if (is_wrapped_key_supported()) {
KeyBuffer ephemeral_wrapped_key;
if (!getEphemeralWrappedKey(KeyFormat::RAW, ce_key, &ephemeral_wrapped_key)) {
LOG(ERROR) << "Failed to export ce key";
return false;
}
ce_key = std::move(ephemeral_wrapped_key);
}
if (!android::vold::installKey(ce_key, &ce_raw_ref)) return false;
s_ce_keys[user_id] = std::move(ce_key);
s_ce_key_raw_refs[user_id] = ce_raw_ref;
LOG(DEBUG) << "Installed ce key for user " << user_id << std::endl;
return true;
}
static bool prepare_dir(const std::string& dir, mode_t mode, uid_t uid, gid_t gid) {
LOG(DEBUG) << "Preparing: " << dir << std::endl;
if (fs_prepare_dir(dir.c_str(), mode, uid, gid) != 0) {
PLOG(ERROR) << "Failed to prepare " << dir << std::endl;
return false;
}
return true;
}
// NB this assumes that there is only one thread listening for crypt commands, because
// it creates keys in a fixed location.
static bool create_and_install_user_keys(userid_t user_id, bool create_ephemeral) {
/*KeyBuffer de_key, ce_key;
if (!android::vold::randomKey(&de_key)) return false;
if (!android::vold::randomKey(&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 {
auto const directory_path = get_ce_key_directory_path(user_id);
if (!prepare_dir(directory_path, 0700, AID_ROOT, AID_ROOT)) return false;
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,
kEmptyAuthentication, ce_key)) return false;
fixate_user_ce_key(directory_path, ce_key_path, paths);
// Write DE key second; once this is written, all is good.
if (!android::vold::storeKeyAtomically(get_de_key_path(user_id), user_key_temp,
kEmptyAuthentication, de_key)) return false;
}
std::string de_raw_ref;
if (!android::vold::installKey(de_key, &de_raw_ref)) return false;
s_de_key_raw_refs[user_id] = de_raw_ref;
std::string ce_raw_ref;
if (!android::vold::installKey(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;*/
LOG(DEBUG) << "TWRP not doing create_and_install_user_keys\n";
return true;
}
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 << std::endl;
return false;
}
*raw_ref = refi->second;
return true;
}
static void get_data_file_encryption_modes(PolicyKeyRef* key_ref) {
/*struct fstab_rec* rec = fs_mgr_get_entry_for_mount_point(fstab_default, DATA_MNT_POINT);
char const* contents_mode = strdup("ice");
char const* filenames_mode = strdup("aes-256-heh");
fs_mgr_get_file_encryption_modes(rec, &contents_mode, &filenames_mode);
key_ref->contents_mode = contents_mode;
key_ref->filenames_mode = filenames_mode;*/
LOG(INFO) << "contents mode '" << android::base::GetProperty("fbe.contents", "aes-256-xts") << "' filenames '" << android::base::GetProperty("fbe.filenames", "aes-256-heh") << "'\n";
key_ref->contents_mode =
android::base::GetProperty("fbe.contents", "aes-256-xts");
key_ref->filenames_mode =
android::base::GetProperty("fbe.filenames", "aes-256-heh");
}
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" << std::endl;
return false;
}
for (;;) {
errno = 0;
auto entry = readdir(dirp.get());
if (!entry) {
if (errno) {
PLOG(ERROR) << "Unable to read de key directory" << std::endl;
return false;
}
break;
}
if (entry->d_type != DT_DIR || !is_numeric(entry->d_name)) {
LOG(DEBUG) << "Skipping non-de-key " << entry->d_name << std::endl;
continue;
}
userid_t user_id = std::stoi(entry->d_name);
if (s_de_key_raw_refs.count(user_id) == 0) {
auto key_path = de_dir + "/" + entry->d_name;
KeyBuffer key;
if (!android::vold::retrieveKey(key_path, kEmptyAuthentication, &key)) return false;
std::string raw_ref;
if (is_wrapped_key_supported()) {
KeyBuffer ephemeral_wrapped_key;
if (!getEphemeralWrappedKey(KeyFormat::RAW, key, &ephemeral_wrapped_key)) {
LOG(ERROR) << "Failed to export de_key in create_and_install_user_keys";
return false;
}
key = std::move(ephemeral_wrapped_key);
}
if (!android::vold::installKey(key, &raw_ref)) return false;
s_de_key_raw_refs[user_id] = raw_ref;
LOG(DEBUG) << "Installed de key for user " << user_id << std::endl;
std::string user_prop = "twrp.user." + std::to_string(user_id) + ".decrypt";
property_set(user_prop.c_str(), "0");
}
}
// 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" << std::endl;
bool wrapped_key_supported = false;
if (s_global_de_initialized) {
LOG(INFO) << "Already initialized" << std::endl;
return true;
}
PolicyKeyRef device_ref;
wrapped_key_supported = is_wrapped_key_supported();
LOG(INFO) << "calling retrieveAndInstallKey\n";
if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication, device_key_path,
device_key_temp, &device_ref.key_raw_ref, wrapped_key_supported))
return false;
get_data_file_encryption_modes(&device_ref);
std::string modestring = device_ref.contents_mode + ":" + device_ref.filenames_mode;
std::string mode_filename = std::string("/data") + e4crypt_key_mode;
if (!android::base::WriteStringToFile(modestring, mode_filename)) {
PLOG(ERROR) << "Cannot save type" << std::endl;
return false;
}
std::string ref_filename = std::string("/data") + e4crypt_key_ref;
if (!android::base::WriteStringToFile(device_ref.key_raw_ref, ref_filename)) {
PLOG(ERROR) << "Cannot save key reference to:" << ref_filename << std::endl;
return false;
}
LOG(INFO) << "Wrote system DE key reference to:" << ref_filename << std::endl;
s_global_de_initialized = true;
de_raw_ref = device_ref.key_raw_ref;
return true;
}
bool e4crypt_init_user0() {
LOG(DEBUG) << "e4crypt_init_user0\n";
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;
if (!android::vold::pathExists(get_de_key_path(0))) {
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;
}
// 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;
}
static bool emulated_unlock(const std::string& path, mode_t mode) {
if (chmod(path.c_str(), mode) != 0) {
PLOG(ERROR) << "Failed to chmod " << path << std::endl;
// 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 << std::endl;
// FIXME temporary workaround for b/26713622
if (e4crypt_is_emulated()) return false;
}
#endif
return true;
}
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" << std::endl; // Don't log the string for security reasons
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 std::string& token_hex,
const std::string& secret_hex) {
LOG(DEBUG) << "e4crypt_unlock_user_key " << user_id << " serial=" << serial
<< " token_present=" << (token_hex != "!") << std::endl;
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 << std::endl;
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 << std::endl;
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::BuildDataMediaCePath("", user_id), 0770) ||
!emulated_unlock(android::vold::BuildDataUserCePath("", user_id), 0771)) {
LOG(ERROR) << "Failed to unlock user " << user_id << std::endl;
return false;
}
}
return true;
}
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