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/* 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/>.
*
*/
#include "toxencryptsave.h"
#include "../toxcore/crypto_core.h"
#ifdef VANILLA_NACL
#include "crypto_pwhash_scryptsalsa208sha256/crypto_pwhash_scryptsalsa208sha256.h"
#include "crypto_pwhash_scryptsalsa208sha256/utils.h" /* sodium_memzero */
#endif
/* This "module" provides functions analogous to tox_load and tox_save in toxcore
* 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.
*/
/* return size of the messenger data (for encrypted saving). */
uint32_t tox_encrypted_size(const Tox *tox)
{
return tox_size(tox) + crypto_box_MACBYTES + crypto_box_NONCEBYTES
+ crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
}
/* Save the messenger data encrypted with the given password.
* data must be at least tox_encrypted_size().
*
* returns 0 on success
* returns -1 on failure
*/
int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint32_t pplength)
{
if (pplength == 0)
return -1;
/* First 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 */
uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
uint8_t key[crypto_box_KEYBYTES];
randombytes_buf(salt, sizeof salt);
if (crypto_pwhash_scryptsalsa208sha256(
key, sizeof(key), passphrase, pplength, salt,
crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE * 2, /* slightly stronger */
crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE) != 0) {
/* out of memory most likely */
return -1;
}
sodium_memzero(passphrase, pplength); /* wipe plaintext pw */
/* next get plain save data */
uint32_t temp_size = tox_size(tox);
uint8_t temp_data[temp_size];
tox_save(tox, temp_data);
/* now encrypt.
* 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
*/
uint32_t prefix_size = crypto_box_NONCEBYTES+crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
uint8_t nonce[crypto_box_NONCEBYTES];
random_nonce(nonce);
if (encrypt_data_symmetric(key, nonce, temp_data, temp_size, data + prefix_size)
!= temp_size + crypto_box_MACBYTES) {
return -1;
}
/* add the prefix */
memcpy(data, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
memcpy(data + crypto_pwhash_scryptsalsa208sha256_SALTBYTES, nonce, crypto_box_NONCEBYTES);
return 0;
}
/* Load the messenger from encrypted data of size length.
*
* returns 0 on success
* returns -1 on failure
*/
int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *passphrase, uint32_t pplength)
{
if (length <= crypto_box_MACBYTES + crypto_box_NONCEBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES)
return -1;
uint32_t decrypt_length = length - crypto_box_MACBYTES - crypto_box_NONCEBYTES
- crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
uint8_t nonce[crypto_box_NONCEBYTES];
memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
memcpy(nonce, data + crypto_pwhash_scryptsalsa208sha256_SALTBYTES, crypto_box_NONCEBYTES);
/* derive the key */
uint8_t key[crypto_box_KEYBYTES];
if (crypto_pwhash_scryptsalsa208sha256(
key, sizeof(key), passphrase, pplength, salt,
crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE * 2, /* slightly stronger */
crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE) != 0) {
/* out of memory most likely */
return -1;
}
sodium_memzero(passphrase, pplength); /* wipe plaintext pw */
/* decrypt the data */
uint8_t temp_data[decrypt_length];
if (decrypt_data_symmetric(key, nonce, data+crypto_pwhash_scryptsalsa208sha256_SALTBYTES+crypto_box_NONCEBYTES,
decrypt_length + crypto_box_MACBYTES, temp_data)
!= decrypt_length) {
return -1;
}
return tox_load(tox, temp_data, decrypt_length);
}
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