Ext4Crypt.cpp - SHIFTPHONES/android_system_vold - Gitiles

 #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 "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 <base/file.h>
 #include <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;
 }

 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;
 }

 // Install password into global keyring
 // Return raw key reference for use in policy
 static std::string e4crypt_install_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());

     // Get raw keyref - used to make keyname and to pass to ioctl
     auto raw_ref = generate_key_ref(ext4_key.raw, ext4_key.size);

     // Generate keyname
     std::ostringstream o;
     for (auto i = raw_ref.begin(); i != raw_ref.end(); ++i) {
         o << std::hex << std::setw(2) << std::setfill('0') << (int)*i;
     }
     auto ref = std::string("ext4:") + o.str();

     // Find existing keyring
     key_serial_t device_keyring = keyctl_search(KEY_SPEC_SESSION_KEYRING,
                                                 "keyring", "e4crypt", 0);

     SLOGI("Found device_keyring - id is %d", device_keyring);

     // Add key ...
     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 "";
     }

     SLOGI("Added key %d (%s) to keyring %d in process %d",
           key_id, ref.c_str(), device_keyring, getpid());

     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_user_key(
     const char *mount_path,
     const char *user_handle,
     bool create_if_absent)
 {
     auto key_path = get_key_path(mount_path, user_handle);
     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 user_key(key_bytes, sizeof(key_bytes));
     if (!android::base::WriteStringToFile(user_key, key_path)) {
         SLOGE("Unable to write key to %s (%s)",
                 key_path.c_str(), strerror(errno));
         return "";
     }
     return user_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_user_key(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 (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);
     // ext4enc:TODO evict the key from the keyring.
     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;
 }
	#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 "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 <base/file.h>
	#include <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;
	}

	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;
	}

	// Install password into global keyring
	// Return raw key reference for use in policy
	static std::string e4crypt_install_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());

	// Get raw keyref - used to make keyname and to pass to ioctl
	auto raw_ref = generate_key_ref(ext4_key.raw, ext4_key.size);

	// Generate keyname
	std::ostringstream o;
	for (auto i = raw_ref.begin(); i != raw_ref.end(); ++i) {
	o << std::hex << std::setw(2) << std::setfill('0') << (int)*i;
	}
	auto ref = std::string("ext4:") + o.str();

	// Find existing keyring
	key_serial_t device_keyring = keyctl_search(KEY_SPEC_SESSION_KEYRING,
	"keyring", "e4crypt", 0);

	SLOGI("Found device_keyring - id is %d", device_keyring);

	// Add key ...
	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 "";
	}

	SLOGI("Added key %d (%s) to keyring %d in process %d",
	key_id, ref.c_str(), device_keyring, getpid());

	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_user_key(
	const char *mount_path,
	const char *user_handle,
	bool create_if_absent)
	{
	auto key_path = get_key_path(mount_path, user_handle);
	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 user_key(key_bytes, sizeof(key_bytes));
	if (!android::base::WriteStringToFile(user_key, key_path)) {
	SLOGE("Unable to write key to %s (%s)",
	key_path.c_str(), strerror(errno));
	return "";
	}
	return user_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_user_key(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 (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);
	// ext4enc:TODO evict the key from the keyring.
	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;
	}