blob: 0807c2ce4ec334fba4ca550c94fcc05d13c9a559 [file] [log] [blame]
#include "Ext4Crypt.h"
#include <iomanip>
#include <map>
#include <fstream>
#include <string>
#include <sstream>
#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 <private/android_filesystem_config.h>
#include "unencrypted_properties.h"
#include "key_control.h"
#include "cryptfs.h"
#include "ext4_crypt_init_extensions.h"
#define LOG_TAG "Ext4Crypt"
#include "cutils/log.h"
#include <cutils/klog.h>
#include <android-base/file.h>
#include <android-base/stringprintf.h>
namespace {
// Key length in bits
const int key_length = 128;
static_assert(key_length % 8 == 0,
"Key length must be multiple of 8 bits");
// How long do we store passwords for?
const int password_max_age_seconds = 60;
// How is device encrypted
struct keys {
std::string master_key;
std::string password;
time_t expiry_time;
};
std::map<std::string, keys> s_key_store;
// ext4enc:TODO get these consts from somewhere good
const int SHA512_LENGTH = 64;
const int EXT4_KEY_DESCRIPTOR_SIZE = 8;
// ext4enc:TODO Include structure from somewhere sensible
// MUST be in sync with ext4_crypto.c in kernel
const int EXT4_MAX_KEY_SIZE = 64;
const int EXT4_ENCRYPTION_MODE_AES_256_XTS = 1;
struct ext4_encryption_key {
uint32_t mode;
char raw[EXT4_MAX_KEY_SIZE];
uint32_t size;
};
namespace tag {
const char* magic = "magic";
const char* major_version = "major_version";
const char* minor_version = "minor_version";
const char* flags = "flags";
const char* crypt_type = "crypt_type";
const char* failed_decrypt_count = "failed_decrypt_count";
const char* crypto_type_name = "crypto_type_name";
const char* master_key = "master_key";
const char* salt = "salt";
const char* kdf_type = "kdf_type";
const char* N_factor = "N_factor";
const char* r_factor = "r_factor";
const char* p_factor = "p_factor";
const char* keymaster_blob = "keymaster_blob";
const char* scrypted_intermediate_key = "scrypted_intermediate_key";
}
}
static std::string e4crypt_install_key(const std::string &key);
static int put_crypt_ftr_and_key(const crypt_mnt_ftr& crypt_ftr,
UnencryptedProperties& props)
{
SLOGI("Putting crypt footer");
bool success = props.Set<int>(tag::magic, crypt_ftr.magic)
&& props.Set<int>(tag::major_version, crypt_ftr.major_version)
&& props.Set<int>(tag::minor_version, crypt_ftr.minor_version)
&& props.Set<int>(tag::flags, crypt_ftr.flags)
&& props.Set<int>(tag::crypt_type, crypt_ftr.crypt_type)
&& props.Set<int>(tag::failed_decrypt_count,
crypt_ftr.failed_decrypt_count)
&& props.Set<std::string>(tag::crypto_type_name,
std::string(reinterpret_cast<const char*>(crypt_ftr.crypto_type_name)))
&& props.Set<std::string>(tag::master_key,
std::string((const char*) crypt_ftr.master_key,
crypt_ftr.keysize))
&& props.Set<std::string>(tag::salt,
std::string((const char*) crypt_ftr.salt,
SALT_LEN))
&& props.Set<int>(tag::kdf_type, crypt_ftr.kdf_type)
&& props.Set<int>(tag::N_factor, crypt_ftr.N_factor)
&& props.Set<int>(tag::r_factor, crypt_ftr.r_factor)
&& props.Set<int>(tag::p_factor, crypt_ftr.p_factor)
&& props.Set<std::string>(tag::keymaster_blob,
std::string((const char*) crypt_ftr.keymaster_blob,
crypt_ftr.keymaster_blob_size))
&& props.Set<std::string>(tag::scrypted_intermediate_key,
std::string((const char*) crypt_ftr.scrypted_intermediate_key,
SCRYPT_LEN));
return success ? 0 : -1;
}
static int get_crypt_ftr_and_key(crypt_mnt_ftr& crypt_ftr,
const UnencryptedProperties& props)
{
memset(&crypt_ftr, 0, sizeof(crypt_ftr));
crypt_ftr.magic = props.Get<int>(tag::magic);
crypt_ftr.major_version = props.Get<int>(tag::major_version);
crypt_ftr.minor_version = props.Get<int>(tag::minor_version);
crypt_ftr.ftr_size = sizeof(crypt_ftr);
crypt_ftr.flags = props.Get<int>(tag::flags);
crypt_ftr.crypt_type = props.Get<int>(tag::crypt_type);
crypt_ftr.failed_decrypt_count = props.Get<int>(tag::failed_decrypt_count);
std::string crypto_type_name = props.Get<std::string>(tag::crypto_type_name);
strlcpy(reinterpret_cast<char*>(crypt_ftr.crypto_type_name),
crypto_type_name.c_str(),
sizeof(crypt_ftr.crypto_type_name));
std::string master_key = props.Get<std::string>(tag::master_key);
crypt_ftr.keysize = master_key.size();
if (crypt_ftr.keysize > sizeof(crypt_ftr.master_key)) {
SLOGE("Master key size too long");
return -1;
}
memcpy(crypt_ftr.master_key, &master_key[0], crypt_ftr.keysize);
std::string salt = props.Get<std::string>(tag::salt);
if (salt.size() != SALT_LEN) {
SLOGE("Salt wrong length");
return -1;
}
memcpy(crypt_ftr.salt, &salt[0], SALT_LEN);
crypt_ftr.kdf_type = props.Get<int>(tag::kdf_type);
crypt_ftr.N_factor = props.Get<int>(tag::N_factor);
crypt_ftr.r_factor = props.Get<int>(tag::r_factor);
crypt_ftr.p_factor = props.Get<int>(tag::p_factor);
std::string keymaster_blob = props.Get<std::string>(tag::keymaster_blob);
crypt_ftr.keymaster_blob_size = keymaster_blob.size();
if (crypt_ftr.keymaster_blob_size > sizeof(crypt_ftr.keymaster_blob)) {
SLOGE("Keymaster blob too long");
return -1;
}
memcpy(crypt_ftr.keymaster_blob, &keymaster_blob[0],
crypt_ftr.keymaster_blob_size);
std::string scrypted_intermediate_key = props.Get<std::string>(tag::scrypted_intermediate_key);
if (scrypted_intermediate_key.size() != SCRYPT_LEN) {
SLOGE("scrypted intermediate key wrong length");
return -1;
}
memcpy(crypt_ftr.scrypted_intermediate_key, &scrypted_intermediate_key[0],
SCRYPT_LEN);
return 0;
}
static UnencryptedProperties GetProps(const char* path)
{
return UnencryptedProperties(path);
}
static UnencryptedProperties GetAltProps(const char* path)
{
return UnencryptedProperties((std::string() + path + "/tmp_mnt").c_str());
}
static UnencryptedProperties GetPropsOrAltProps(const char* path)
{
UnencryptedProperties props = GetProps(path);
if (props.OK()) {
return props;
}
return GetAltProps(path);
}
int e4crypt_enable(const char* path)
{
// Already enabled?
if (s_key_store.find(path) != s_key_store.end()) {
return 0;
}
// Not an encryptable device?
UnencryptedProperties key_props = GetProps(path).GetChild(properties::key);
if (!key_props.OK()) {
return 0;
}
if (key_props.Get<std::string>(tag::master_key).empty()) {
crypt_mnt_ftr ftr;
if (cryptfs_create_default_ftr(&ftr, key_length)) {
SLOGE("Failed to create crypto footer");
return -1;
}
// Scrub fields not used by ext4enc
ftr.persist_data_offset[0] = 0;
ftr.persist_data_offset[1] = 0;
ftr.persist_data_size = 0;
if (put_crypt_ftr_and_key(ftr, key_props)) {
SLOGE("Failed to write crypto footer");
return -1;
}
crypt_mnt_ftr ftr2;
if (get_crypt_ftr_and_key(ftr2, key_props)) {
SLOGE("Failed to read crypto footer back");
return -1;
}
if (memcmp(&ftr, &ftr2, sizeof(ftr)) != 0) {
SLOGE("Crypto footer not correctly written");
return -1;
}
}
if (!UnencryptedProperties(path).Remove(properties::ref)) {
SLOGE("Failed to remove key ref");
return -1;
}
return e4crypt_check_passwd(path, "");
}
int e4crypt_change_password(const char* path, int crypt_type,
const char* password)
{
SLOGI("e4crypt_change_password");
auto key_props = GetProps(path).GetChild(properties::key);
crypt_mnt_ftr ftr;
if (get_crypt_ftr_and_key(ftr, key_props)) {
SLOGE("Failed to read crypto footer back");
return -1;
}
auto mki = s_key_store.find(path);
if (mki == s_key_store.end()) {
SLOGE("No stored master key - can't change password");
return -1;
}
const unsigned char* master_key_bytes
= reinterpret_cast<const unsigned char*>(&mki->second.master_key[0]);
if (cryptfs_set_password(&ftr, password, master_key_bytes)) {
SLOGE("Failed to set password");
return -1;
}
ftr.crypt_type = crypt_type;
if (put_crypt_ftr_and_key(ftr, key_props)) {
SLOGE("Failed to write crypto footer");
return -1;
}
if (!UnencryptedProperties(path).Set(properties::is_default,
crypt_type == CRYPT_TYPE_DEFAULT)) {
SLOGE("Failed to update default flag");
return -1;
}
return 0;
}
int e4crypt_crypto_complete(const char* path)
{
SLOGI("ext4 crypto complete called on %s", path);
auto key_props = GetPropsOrAltProps(path).GetChild(properties::key);
if (key_props.Get<std::string>(tag::master_key).empty()) {
SLOGI("No master key, so not ext4enc");
return -1;
}
return 0;
}
// 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_LENGTH];
SHA512_Final(key_ref1, &c);
SHA512_Init(&c);
SHA512_Update(&c, key_ref1, SHA512_LENGTH);
unsigned char key_ref2[SHA512_LENGTH];
SHA512_Final(key_ref2, &c);
return std::string((char*)key_ref2, EXT4_KEY_DESCRIPTOR_SIZE);
}
int e4crypt_check_passwd(const char* path, const char* password)
{
SLOGI("e4crypt_check_password");
auto props = GetPropsOrAltProps(path);
auto key_props = props.GetChild(properties::key);
crypt_mnt_ftr ftr;
if (get_crypt_ftr_and_key(ftr, key_props)) {
SLOGE("Failed to read crypto footer back");
return -1;
}
unsigned char master_key_bytes[key_length / 8];
if (cryptfs_get_master_key (&ftr, password, master_key_bytes)){
SLOGI("Incorrect password");
ftr.failed_decrypt_count++;
if (put_crypt_ftr_and_key(ftr, key_props)) {
SLOGW("Failed to update failed_decrypt_count");
}
return ftr.failed_decrypt_count;
}
if (ftr.failed_decrypt_count) {
ftr.failed_decrypt_count = 0;
if (put_crypt_ftr_and_key(ftr, key_props)) {
SLOGW("Failed to reset failed_decrypt_count");
}
}
std::string master_key(reinterpret_cast<char*>(master_key_bytes),
sizeof(master_key_bytes));
struct timespec now;
clock_gettime(CLOCK_BOOTTIME, &now);
s_key_store[path] = keys{master_key, password,
now.tv_sec + password_max_age_seconds};
auto raw_ref = e4crypt_install_key(master_key);
if (raw_ref.empty()) {
return -1;
}
// Save reference to key so we can set policy later
if (!props.Set(properties::ref, raw_ref)) {
SLOGE("Cannot save key reference");
return -1;
}
return 0;
}
static ext4_encryption_key fill_key(const std::string &key)
{
// ext4enc:TODO Currently raw key is required to be of length
// sizeof(ext4_key.raw) == EXT4_MAX_KEY_SIZE, so zero pad to
// this length. Change when kernel bug is fixed.
ext4_encryption_key ext4_key = {EXT4_ENCRYPTION_MODE_AES_256_XTS,
{0},
sizeof(ext4_key.raw)};
memset(ext4_key.raw, 0, sizeof(ext4_key.raw));
static_assert(key_length / 8 <= sizeof(ext4_key.raw),
"Key too long!");
memcpy(ext4_key.raw, &key[0], key.size());
return ext4_key;
}
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);
}
static int e4crypt_install_key(const ext4_encryption_key &ext4_key, const std::string &ref)
{
key_serial_t device_keyring = e4crypt_keyring();
SLOGI("Found device_keyring - id is %d", device_keyring);
key_serial_t key_id = add_key("logon", ref.c_str(),
(void*)&ext4_key, sizeof(ext4_key),
device_keyring);
if (key_id == -1) {
SLOGE("Failed to insert key into keyring with error %s",
strerror(errno));
return -1;
}
SLOGI("Added key %d (%s) to keyring %d in process %d",
key_id, ref.c_str(), device_keyring, getpid());
return 0;
}
// Install password into global keyring
// Return raw key reference for use in policy
static std::string e4crypt_install_key(const std::string &key)
{
auto ext4_key = fill_key(key);
auto raw_ref = generate_key_ref(ext4_key.raw, ext4_key.size);
auto ref = keyname(raw_ref);
if (e4crypt_install_key(ext4_key, ref) == -1) {
return "";
}
return raw_ref;
}
int e4crypt_restart(const char* path)
{
SLOGI("e4crypt_restart");
int rc = 0;
SLOGI("ext4 restart called on %s", path);
property_set("vold.decrypt", "trigger_reset_main");
SLOGI("Just asked init to shut down class main");
sleep(2);
std::string tmp_path = std::string() + path + "/tmp_mnt";
rc = wait_and_unmount(tmp_path.c_str(), true);
if (rc) {
SLOGE("umount %s failed with rc %d, msg %s",
tmp_path.c_str(), rc, strerror(errno));
return rc;
}
rc = wait_and_unmount(path, true);
if (rc) {
SLOGE("umount %s failed with rc %d, msg %s",
path, rc, strerror(errno));
return rc;
}
return 0;
}
int e4crypt_get_password_type(const char* path)
{
SLOGI("e4crypt_get_password_type");
return GetPropsOrAltProps(path).GetChild(properties::key)
.Get<int>(tag::crypt_type, CRYPT_TYPE_DEFAULT);
}
const char* e4crypt_get_password(const char* path)
{
SLOGI("e4crypt_get_password");
auto i = s_key_store.find(path);
if (i == s_key_store.end()) {
return 0;
}
struct timespec now;
clock_gettime(CLOCK_BOOTTIME, &now);
if (i->second.expiry_time < now.tv_sec) {
e4crypt_clear_password(path);
return 0;
}
return i->second.password.c_str();
}
void e4crypt_clear_password(const char* path)
{
SLOGI("e4crypt_clear_password");
auto i = s_key_store.find(path);
if (i == s_key_store.end()) {
return;
}
memset(&i->second.password[0], 0, i->second.password.size());
i->second.password = std::string();
}
int e4crypt_get_field(const char* path, const char* fieldname,
char* value, size_t len)
{
auto v = GetPropsOrAltProps(path).GetChild(properties::props)
.Get<std::string>(fieldname);
if (v == "") {
return CRYPTO_GETFIELD_ERROR_NO_FIELD;
}
if (v.length() >= len) {
return CRYPTO_GETFIELD_ERROR_BUF_TOO_SMALL;
}
strlcpy(value, v.c_str(), len);
return 0;
}
int e4crypt_set_field(const char* path, const char* fieldname,
const char* value)
{
return GetPropsOrAltProps(path).GetChild(properties::props)
.Set(fieldname, std::string(value)) ? 0 : -1;
}
static std::string get_key_path(
const char *mount_path,
const char *user_handle)
{
// ext4enc:TODO get the path properly
auto key_dir = android::base::StringPrintf("%s/misc/vold/user_keys",
mount_path);
if (mkdir(key_dir.c_str(), 0700) < 0 && errno != EEXIST) {
SLOGE("Unable to create %s (%s)", key_dir.c_str(), strerror(errno));
return "";
}
return key_dir + "/" + user_handle;
}
// ext4enc:TODO this can't be the only place keys are read from /dev/urandom
// we should unite those places.
static std::string e4crypt_get_key(
const std::string &key_path,
bool create_if_absent)
{
std::string content;
if (android::base::ReadFileToString(key_path, &content)) {
if (content.size() != key_length/8) {
SLOGE("Wrong size key %zu in %s", content.size(), key_path.c_str());
return "";
}
return content;
}
if (!create_if_absent) {
SLOGE("No key found in %s", key_path.c_str());
return "";
}
std::ifstream urandom("/dev/urandom");
if (!urandom) {
SLOGE("Unable to open /dev/urandom (%s)", strerror(errno));
return "";
}
char key_bytes[key_length / 8];
errno = 0;
urandom.read(key_bytes, sizeof(key_bytes));
if (!urandom) {
SLOGE("Unable to read key from /dev/urandom (%s)", strerror(errno));
return "";
}
std::string key(key_bytes, sizeof(key_bytes));
if (!android::base::WriteStringToFile(key, key_path)) {
SLOGE("Unable to write key to %s (%s)",
key_path.c_str(), strerror(errno));
return "";
}
return key;
}
static int e4crypt_set_user_policy(const char *mount_path, const char *user_handle,
const char *path, bool create_if_absent)
{
SLOGD("e4crypt_set_user_policy for %s", user_handle);
auto user_key = e4crypt_get_key(
get_key_path(mount_path, user_handle),
create_if_absent);
if (user_key.empty()) {
return -1;
}
auto raw_ref = e4crypt_install_key(user_key);
if (raw_ref.empty()) {
return -1;
}
return do_policy_set(path, raw_ref.c_str(), raw_ref.size());
}
int e4crypt_create_new_user_dir(const char *user_handle, const char *path) {
SLOGD("e4crypt_create_new_user_dir(\"%s\", \"%s\")", user_handle, path);
if (mkdir(path, S_IRWXU | S_IRWXG | S_IXOTH) < 0) {
return -1;
}
if (chmod(path, S_IRWXU | S_IRWXG | S_IXOTH) < 0) {
return -1;
}
if (chown(path, AID_SYSTEM, AID_SYSTEM) < 0) {
return -1;
}
if (e4crypt_crypto_complete(DATA_MNT_POINT) == 0) {
// ext4enc:TODO handle errors from this.
e4crypt_set_user_policy(DATA_MNT_POINT, user_handle, path, true);
}
return 0;
}
static bool is_numeric(const char *name) {
for (const char *p = name; *p != '\0'; p++) {
if (!isdigit(*p))
return false;
}
return true;
}
int e4crypt_set_user_crypto_policies(const char *dir)
{
if (e4crypt_crypto_complete(DATA_MNT_POINT) != 0) {
return 0;
}
SLOGD("e4crypt_set_user_crypto_policies");
std::unique_ptr<DIR, int(*)(DIR*)> dirp(opendir(dir), closedir);
if (!dirp) {
SLOGE("Unable to read directory %s, error %s\n",
dir, strerror(errno));
return -1;
}
for (;;) {
struct dirent *result = readdir(dirp.get());
if (!result) {
// ext4enc:TODO check errno
break;
}
if (result->d_type != DT_DIR || !is_numeric(result->d_name)) {
continue; // skips user 0, which is a symlink
}
auto user_dir = std::string() + dir + "/" + result->d_name;
// ext4enc:TODO don't hardcode /data
if (e4crypt_set_user_policy("/data", result->d_name,
user_dir.c_str(), false)) {
// ext4enc:TODO If this function fails, stop the boot: we must
// deliver on promised encryption.
SLOGE("Unable to set policy on %s\n", user_dir.c_str());
}
}
return 0;
}
int e4crypt_delete_user_key(const char *user_handle) {
SLOGD("e4crypt_delete_user_key(\"%s\")", user_handle);
auto key_path = get_key_path(DATA_MNT_POINT, user_handle);
auto key = e4crypt_get_key(key_path, false);
auto ext4_key = fill_key(key);
auto ref = keyname(generate_key_ref(ext4_key.raw, ext4_key.size));
auto key_serial = keyctl_search(e4crypt_keyring(), "logon", ref.c_str(), 0);
if (keyctl_revoke(key_serial) == 0) {
SLOGD("Revoked key with serial %ld ref %s\n", key_serial, ref.c_str());
} else {
SLOGE("Failed to revoke key with serial %ld ref %s: %s\n",
key_serial, ref.c_str(), strerror(errno));
}
int pid = fork();
if (pid < 0) {
SLOGE("Unable to fork: %s", strerror(errno));
return -1;
}
if (pid == 0) {
SLOGD("Forked for secdiscard");
execl("/system/bin/secdiscard",
"/system/bin/secdiscard",
key_path.c_str(),
NULL);
SLOGE("Unable to launch secdiscard on %s: %s\n", key_path.c_str(),
strerror(errno));
exit(-1);
}
// ext4enc:TODO reap the zombie
return 0;
}