toxcore/toxencryptsave/toxencryptsave.c
2015-05-27 19:54:04 -04:00

297 lines
11 KiB
C

/* toxencryptsave.c
*
* The Tox encrypted save functions.
*
* Copyright (C) 2013 Tox project All Rights Reserved.
*
* This file is part of Tox.
*
* Tox is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Tox is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Tox. If not, see <http://www.gnu.org/licenses/>.
*
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "toxencryptsave.h"
#include "defines.h"
#include "../toxcore/crypto_core.h"
#define SET_ERROR_PARAMETER(param, x) {if(param) {*param = x;}}
#ifdef VANILLA_NACL
#include "crypto_pwhash_scryptsalsa208sha256/crypto_pwhash_scryptsalsa208sha256.h"
#include "crypto_pwhash_scryptsalsa208sha256/utils.h" /* sodium_memzero */
#include <crypto_hash_sha256.h>
#endif
#if TOX_PASS_SALT_LENGTH != crypto_pwhash_scryptsalsa208sha256_SALTBYTES
#error TOX_PASS_SALT_LENGTH is assumed to be equal to crypto_pwhash_scryptsalsa208sha256_SALTBYTES
#endif
#if TOX_PASS_KEY_LENGTH != crypto_box_KEYBYTES
#error TOX_PASS_KEY_LENGTH is assumed to be equal to crypto_box_KEYBYTES
#endif
#if TOX_PASS_ENCRYPTION_EXTRA_LENGTH != (crypto_box_MACBYTES + crypto_box_NONCEBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH)
#error TOX_PASS_ENCRYPTION_EXTRA_LENGTH is assumed to be equal to (crypto_box_MACBYTES + crypto_box_NONCEBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH)
#endif
/* Clients should consider alerting their users that, unlike plain data, if even one bit
* becomes corrupted, the data will be entirely unrecoverable.
* Ditto if they forget their password, there is no way to recover the data.
*/
/* This retrieves the salt used to encrypt the given data, which can then be passed to
* derive_key_with_salt to produce the same key as was previously used. Any encrpyted
* data with this module can be used as input.
*
* returns true if magic number matches
* success does not say anything about the validity of the data, only that data of
* the appropriate size was copied
*/
bool tox_get_salt(const uint8_t *data, uint8_t *salt)
{
if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0)
return 0;
data += TOX_ENC_SAVE_MAGIC_LENGTH;
memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
return 1;
}
/* Generates a secret symmetric key from the given passphrase. out_key must be at least
* TOX_PASS_KEY_LENGTH bytes long.
* Be sure to not compromise the key! Only keep it in memory, do not write to disk.
* The password is zeroed after key derivation.
* The key should only be used with the other functions in this module, as it
* includes a salt.
* Note that this function is not deterministic; to derive the same key from a
* password, you also must know the random salt that was used. See below.
*
* returns true on success
*/
bool tox_derive_key_from_pass(const uint8_t *passphrase, size_t pplength, TOX_PASS_KEY *out_key,
TOX_ERR_KEY_DERIVATION *error)
{
uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
randombytes(salt, sizeof salt);
return tox_derive_key_with_salt(passphrase, pplength, salt, out_key, error);
}
/* Same as above, except with use the given salt for deterministic key derivation.
* The salt must be TOX_PASS_SALT_LENGTH bytes in length.
*/
bool tox_derive_key_with_salt(const uint8_t *passphrase, size_t pplength, const uint8_t *salt, TOX_PASS_KEY *out_key,
TOX_ERR_KEY_DERIVATION *error)
{
if (!salt || !out_key || (!passphrase && pplength != 0)) {
SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_NULL);
return 0;
}
uint8_t passkey[crypto_hash_sha256_BYTES];
crypto_hash_sha256(passkey, passphrase, pplength);
uint8_t key[crypto_box_KEYBYTES];
/* Derive a key from the password */
/* http://doc.libsodium.org/key_derivation/README.html */
/* note that, according to the documentation, a generic pwhash interface will be created
* once the pwhash competition (https://password-hashing.net/) is over */
if (crypto_pwhash_scryptsalsa208sha256(
key, sizeof(key), (char *)passkey, sizeof(passkey), salt,
crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE * 2, /* slightly stronger */
crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE) != 0) {
/* out of memory most likely */
SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_FAILED);
return 0;
}
sodium_memzero(passkey, crypto_hash_sha256_BYTES); /* wipe plaintext pw */
memcpy(out_key->salt, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
memcpy(out_key->key, key, crypto_box_KEYBYTES);
SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_OK);
return 1;
}
/* Encrypt arbitrary with a key produced by tox_derive_key_*. The output
* array must be at least data_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long.
* key must be TOX_PASS_KEY_LENGTH bytes.
* If you already have a symmetric key from somewhere besides this module, simply
* call encrypt_data_symmetric in toxcore/crypto_core directly.
*
* returns true on success
*/
bool tox_pass_key_encrypt(const uint8_t *data, size_t data_len, const TOX_PASS_KEY *key, uint8_t *out,
TOX_ERR_ENCRYPTION *error)
{
if (data_len == 0 || !data || !key || !out) {
SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_NULL);
return 0;
}
/* the output data consists of, in order:
* salt, nonce, mac, enc_data
* where the mac is automatically prepended by the encrypt()
* the salt+nonce is called the prefix
* I'm not sure what else I'm supposed to do with the salt and nonce, since we
* need them to decrypt the data
*/
/* first add the magic number */
memcpy(out, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH);
out += TOX_ENC_SAVE_MAGIC_LENGTH;
/* then add the rest prefix */
memcpy(out, key->salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
out += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
uint8_t nonce[crypto_box_NONCEBYTES];
random_nonce(nonce);
memcpy(out, nonce, crypto_box_NONCEBYTES);
out += crypto_box_NONCEBYTES;
/* now encrypt */
if (encrypt_data_symmetric(key->key, nonce, data, data_len, out)
!= data_len + crypto_box_MACBYTES) {
SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_FAILED);
return 0;
}
SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_OK);
return 1;
}
/* Encrypts the given data with the given passphrase. The output array must be
* at least data_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long. This delegates
* to tox_derive_key_from_pass and tox_pass_key_encrypt.
*
* returns true on success
*/
bool tox_pass_encrypt(const uint8_t *data, size_t data_len, const uint8_t *passphrase, size_t pplength, uint8_t *out,
TOX_ERR_ENCRYPTION *error)
{
TOX_PASS_KEY key;
TOX_ERR_KEY_DERIVATION _error;
if (!tox_derive_key_from_pass(passphrase, pplength, &key, &_error)) {
if (_error == TOX_ERR_KEY_DERIVATION_NULL) {
SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_NULL);
} else if (_error == TOX_ERR_KEY_DERIVATION_FAILED) {
SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED);
}
return 0;
}
return tox_pass_key_encrypt(data, data_len, &key, out, error);
}
/* This is the inverse of tox_pass_key_encrypt, also using only keys produced by
* tox_derive_key_from_pass.
*
* the output data has size data_length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH
*
* returns true on success
*/
bool tox_pass_key_decrypt(const uint8_t *data, size_t length, const TOX_PASS_KEY *key, uint8_t *out,
TOX_ERR_DECRYPTION *error)
{
if (length <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH) {
SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_INVALID_LENGTH);
return 0;
}
if (!data || !key || !out) {
SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_NULL);
return 0;
}
if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_BAD_FORMAT);
return 0;
}
data += TOX_ENC_SAVE_MAGIC_LENGTH;
data += crypto_pwhash_scryptsalsa208sha256_SALTBYTES; // salt only affects key derivation
size_t decrypt_length = length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
uint8_t nonce[crypto_box_NONCEBYTES];
memcpy(nonce, data, crypto_box_NONCEBYTES);
data += crypto_box_NONCEBYTES;
/* decrypt the data */
if (decrypt_data_symmetric(key->key, nonce, data, decrypt_length + crypto_box_MACBYTES, out)
!= decrypt_length) {
SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_FAILED);
return 0;
}
SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_OK);
return 1;
}
/* Decrypts the given data with the given passphrase. The output array must be
* at least data_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long. This delegates
* to tox_pass_key_decrypt.
*
* the output data has size data_length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH
*
* returns true on success
*/
bool tox_pass_decrypt(const uint8_t *data, size_t length, const uint8_t *passphrase, size_t pplength, uint8_t *out,
TOX_ERR_DECRYPTION *error)
{
if (length <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH) {
SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_INVALID_LENGTH);
return 0;
}
if (!data || !passphrase || !out) {
SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_NULL);
return 0;
}
if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_BAD_FORMAT);
return 0;
}
uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
memcpy(salt, data + TOX_ENC_SAVE_MAGIC_LENGTH, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
/* derive the key */
TOX_PASS_KEY key;
if (!tox_derive_key_with_salt(passphrase, pplength, salt, &key, NULL)) {
/* out of memory most likely */
SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED);
return 0;
}
return tox_pass_key_decrypt(data, length, &key, out, error);
}
/* Determines whether or not the given data is encrypted (by checking the magic number)
*/
bool tox_is_data_encrypted(const uint8_t *data)
{
if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) == 0)
return 1;
else
return 0;
}