toxcore/toxencryptsave/toxencryptsave.c
2015-02-14 23:00:12 -05:00

347 lines
12 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"
#include "../toxcore/tox.h"
#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
#define TOX_PASS_ENCRYPTION_EXTRA_LENGTH (crypto_box_MACBYTES + crypto_box_NONCEBYTES \
+ crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH)
#define TOX_PASS_KEY_LENGTH (crypto_pwhash_scryptsalsa208sha256_SALTBYTES + crypto_box_KEYBYTES)
int tox_pass_encryption_extra_length()
{
return TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
}
int tox_pass_key_length()
{
return TOX_PASS_KEY_LENGTH;
}
int tox_pass_salt_length()
{
return crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
}
/* 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_save_size(tox) + TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
}
/* 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 -1 if the magic number is wrong
* returns 0 otherwise (no guarantee about validity of data)
*/
int tox_get_salt(uint8_t *data, uint8_t *salt)
{
if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0)
return -1;
data += TOX_ENC_SAVE_MAGIC_LENGTH;
memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
return 0;
}
/* 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.
* This function is fairly cheap, but irungentoo insists that you be allowed to
* cache the result if you want, to minimize computation for repeated encryptions.
* 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.
*
* returns 0 on success
* returns -1 on failure
*/
int tox_derive_key_from_pass(uint8_t *passphrase, uint32_t pplength, uint8_t *out_key)
{
uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
randombytes(salt, sizeof salt);
return tox_derive_key_with_salt(passphrase, pplength, salt, out_key);
}
/* Same as above, except with use the given salt for deterministic key derivation.
* The salt must be tox_salt_length() bytes in length.
*/
int tox_derive_key_with_salt(uint8_t *passphrase, uint32_t pplength, uint8_t *salt, uint8_t *out_key)
{
if (pplength == 0)
return -1;
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 */
return -1;
}
sodium_memzero(passkey, crypto_hash_sha256_BYTES); /* wipe plaintext pw */
memcpy(out_key, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
memcpy(out_key + crypto_pwhash_scryptsalsa208sha256_SALTBYTES, key, crypto_box_KEYBYTES);
return 0;
}
/* Encrypt arbitrary with a key produced by tox_derive_key_from_pass. 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 0 on success
* returns -1 on failure
*/
int tox_pass_key_encrypt(const uint8_t *data, uint32_t data_len, const uint8_t *key, uint8_t *out)
{
/* 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, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
key += 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, nonce, data, data_len, out)
!= data_len + crypto_box_MACBYTES) {
return -1;
}
return 0;
}
/* 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 0 on success
* returns -1 on failure
*/
int tox_pass_encrypt(const uint8_t *data, uint32_t data_len, uint8_t *passphrase, uint32_t pplength, uint8_t *out)
{
uint8_t key[TOX_PASS_KEY_LENGTH];
if (tox_derive_key_from_pass(passphrase, pplength, key) == -1)
return -1;
return tox_pass_key_encrypt(data, data_len, key, out);
}
/* 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)
{
/* first get plain save data */
uint32_t temp_size = tox_save_size(tox);
uint8_t temp_data[temp_size];
tox_save(tox, temp_data);
/* now encrypt */
return tox_pass_encrypt(temp_data, temp_size, passphrase, pplength, data);
}
/* Save the messenger data encrypted with the given key from tox_derive_key.
* data must be at least tox_encrypted_size().
*
* returns 0 on success
* returns -1 on failure
*/
int tox_encrypted_key_save(const Tox *tox, uint8_t *data, uint8_t *key)
{
/* first get plain save data */
uint32_t temp_size = tox_save_size(tox);
uint8_t temp_data[temp_size];
tox_save(tox, temp_data);
/* encrypt */
return tox_pass_key_encrypt(temp_data, temp_size, key, data);
}
/* This is the inverse of tox_pass_key_encrypt, also using only keys produced by
* tox_derive_key_from_pass.
*
* returns the length of the output data (== data_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH) on success
* returns -1 on failure
*/
int tox_pass_key_decrypt(const uint8_t *data, uint32_t length, const uint8_t *key, uint8_t *out)
{
if (length <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH
|| 0 != memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH))
return -1;
data += TOX_ENC_SAVE_MAGIC_LENGTH;
uint32_t decrypt_length = length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
//uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
uint8_t nonce[crypto_box_NONCEBYTES];
//memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
key += crypto_pwhash_scryptsalsa208sha256_SALTBYTES; // ignore the salt, which is only needed for kdf
data += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
memcpy(nonce, data, crypto_box_NONCEBYTES);
data += crypto_box_NONCEBYTES;
/* decrypt the data */
if (decrypt_data_symmetric(key, nonce, data, decrypt_length + crypto_box_MACBYTES, out)
!= decrypt_length) {
return -1;
}
return decrypt_length;
}
/* Decrypts the given data with the given passphrase. The output array must be
* at least data_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long.
*
* returns the length of the output data (== data_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH) on success
* returns -1 on failure
*/
int tox_pass_decrypt(const uint8_t *data, uint32_t length, uint8_t *passphrase, uint32_t pplength, uint8_t *out)
{
uint8_t passkey[crypto_hash_sha256_BYTES];
crypto_hash_sha256(passkey, passphrase, pplength);
uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
memcpy(salt, data + TOX_ENC_SAVE_MAGIC_LENGTH, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
/* derive the key */
uint8_t key[crypto_box_KEYBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
if (crypto_pwhash_scryptsalsa208sha256(
key + crypto_pwhash_scryptsalsa208sha256_SALTBYTES,
crypto_box_KEYBYTES, (char *)passkey, sizeof(passkey), salt,
crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE * 2, /* slightly stronger */
crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE) != 0) {
/* out of memory most likely */
return -1;
}
sodium_memzero(passkey, crypto_hash_sha256_BYTES); /* wipe plaintext pw */
return tox_pass_key_decrypt(data, length, key, out);
}
/* 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)
{
uint32_t decrypt_length = length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
uint8_t temp_data[decrypt_length];
if (tox_pass_decrypt(data, length, passphrase, pplength, temp_data)
!= decrypt_length)
return -1;
return tox_load(tox, temp_data, decrypt_length);
}
/* Load the messenger from encrypted data of size length, with key from tox_derive_key.
*
* returns 0 on success
* returns -1 on failure
*/
int tox_encrypted_key_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *key)
{
uint32_t decrypt_length = length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
uint8_t temp_data[decrypt_length];
if (tox_pass_key_decrypt(data, length, key, temp_data)
!= decrypt_length)
return -1;
return tox_load(tox, temp_data, decrypt_length);
}
/* Determines whether or not the given data is encrypted (by checking the magic number)
*
* returns 1 if it is encrypted
* returns 0 otherwise
*/
int 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;
}
int tox_is_save_encrypted(const uint8_t *data)
{
return tox_is_data_encrypted(data);
}