mirror of
https://github.com/irungentoo/toxcore.git
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`system_random()` can fail and return NULL, which should be handled by toxencryptsave functions. Also synced function comments between .h and .c file for toxencryptsave.
389 lines
14 KiB
C
389 lines
14 KiB
C
/* SPDX-License-Identifier: GPL-3.0-or-later
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* Copyright © 2016-2018 The TokTok team.
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* Copyright © 2013 Tox project.
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*/
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/**
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* Batch encryption functions.
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*/
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#include "toxencryptsave.h"
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#include <sodium.h>
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#include <stdlib.h>
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#include <string.h>
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#include "../toxcore/ccompat.h"
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#include "../toxcore/crypto_core.h"
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#include "defines.h"
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static_assert(TOX_PASS_SALT_LENGTH == crypto_pwhash_scryptsalsa208sha256_SALTBYTES,
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"TOX_PASS_SALT_LENGTH is assumed to be equal to crypto_pwhash_scryptsalsa208sha256_SALTBYTES");
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static_assert(TOX_PASS_KEY_LENGTH == CRYPTO_SHARED_KEY_SIZE,
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"TOX_PASS_KEY_LENGTH is assumed to be equal to CRYPTO_SHARED_KEY_SIZE");
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static_assert(TOX_PASS_ENCRYPTION_EXTRA_LENGTH == (crypto_box_MACBYTES + crypto_box_NONCEBYTES +
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crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH),
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"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)");
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#define SET_ERROR_PARAMETER(param, x) \
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do { \
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if (param != nullptr) { \
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*param = x; \
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} \
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} while (0)
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uint32_t tox_pass_salt_length(void)
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{
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return TOX_PASS_SALT_LENGTH;
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}
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uint32_t tox_pass_key_length(void)
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{
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return TOX_PASS_KEY_LENGTH;
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}
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uint32_t tox_pass_encryption_extra_length(void)
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{
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return TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
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}
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struct Tox_Pass_Key {
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uint8_t salt[TOX_PASS_SALT_LENGTH];
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uint8_t key[TOX_PASS_KEY_LENGTH];
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};
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void tox_pass_key_free(Tox_Pass_Key *key)
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{
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free(key);
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}
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/* Clients should consider alerting their users that, unlike plain data, if even one bit
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* becomes corrupted, the data will be entirely unrecoverable.
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* Ditto if they forget their password, there is no way to recover the data.
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*/
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/**
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* Retrieves the salt used to encrypt the given data.
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*
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* The retrieved salt can then be passed to tox_pass_key_derive_with_salt to
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* produce the same key as was previously used. Any data encrypted with this
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* module can be used as input.
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*
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* The cipher text must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in length.
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* The salt must be TOX_PASS_SALT_LENGTH bytes in length.
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* If the passed byte arrays are smaller than required, the behaviour is
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* undefined.
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*
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* If the cipher text pointer or the salt is NULL, this function returns false.
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*
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* Success does not say anything about the validity of the data, only that
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* data of the appropriate size was copied.
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*
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* @return true on success.
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*/
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bool tox_get_salt(const uint8_t *ciphertext, uint8_t *salt, Tox_Err_Get_Salt *error)
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{
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if (ciphertext == nullptr || salt == nullptr) {
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SET_ERROR_PARAMETER(error, TOX_ERR_GET_SALT_NULL);
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return false;
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}
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if (memcmp(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
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SET_ERROR_PARAMETER(error, TOX_ERR_GET_SALT_BAD_FORMAT);
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return false;
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}
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ciphertext += TOX_ENC_SAVE_MAGIC_LENGTH;
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memcpy(salt, ciphertext, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
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SET_ERROR_PARAMETER(error, TOX_ERR_GET_SALT_OK);
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return true;
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}
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/**
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* Generates a secret symmetric key from the given passphrase.
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*
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* Be sure to not compromise the key! Only keep it in memory, do not write
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* it to disk.
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*
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* Note that this function is not deterministic; to derive the same key from
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* a password, you also must know the random salt that was used. A
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* deterministic version of this function is `tox_pass_key_derive_with_salt`.
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*
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* @param passphrase The user-provided password. Can be empty.
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* @param passphrase_len The length of the password.
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*
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* @return new symmetric key on success, NULL on failure.
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*/
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Tox_Pass_Key *tox_pass_key_derive(const uint8_t *passphrase, size_t passphrase_len,
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Tox_Err_Key_Derivation *error)
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{
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const Random *rng = system_random();
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if (rng == nullptr) {
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SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_FAILED);
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return nullptr;
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}
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uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
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random_bytes(rng, salt, sizeof(salt));
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return tox_pass_key_derive_with_salt(passphrase, passphrase_len, salt, error);
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}
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/**
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* Same as above, except use the given salt for deterministic key derivation.
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*
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* @param passphrase The user-provided password. Can be empty.
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* @param passphrase_len The length of the password.
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* @param salt An array of at least TOX_PASS_SALT_LENGTH bytes.
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*
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* @return new symmetric key on success, NULL on failure.
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*/
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Tox_Pass_Key *tox_pass_key_derive_with_salt(const uint8_t *passphrase, size_t passphrase_len,
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const uint8_t *salt, Tox_Err_Key_Derivation *error)
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{
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if (salt == nullptr || (passphrase == nullptr && passphrase_len != 0)) {
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SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_NULL);
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return nullptr;
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}
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uint8_t passkey[crypto_hash_sha256_BYTES];
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crypto_hash_sha256(passkey, passphrase, passphrase_len);
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uint8_t key[CRYPTO_SHARED_KEY_SIZE];
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// Derive a key from the password
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// http://doc.libsodium.org/key_derivation/README.html
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// note that, according to the documentation, a generic pwhash interface will be created
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// once the pwhash competition (https://password-hashing.net/) is over */
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if (crypto_pwhash_scryptsalsa208sha256(
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key, sizeof(key), (char *)passkey, sizeof(passkey), salt,
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crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE * 2, /* slightly stronger */
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crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE) != 0) {
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/* out of memory most likely */
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SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_FAILED);
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return nullptr;
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}
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crypto_memzero(passkey, crypto_hash_sha256_BYTES); /* wipe plaintext pw */
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Tox_Pass_Key *out_key = (Tox_Pass_Key *)calloc(1, sizeof(Tox_Pass_Key));
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if (out_key == nullptr) {
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SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_FAILED);
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return nullptr;
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}
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memcpy(out_key->salt, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
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memcpy(out_key->key, key, CRYPTO_SHARED_KEY_SIZE);
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SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_OK);
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return out_key;
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}
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/**
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* Encrypt a plain text with a key produced by tox_pass_key_derive or tox_pass_key_derive_with_salt.
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*
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* The output array must be at least `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH`
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* bytes long.
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*
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* @param plaintext A byte array of length `plaintext_len`.
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* @param plaintext_len The length of the plain text array. Bigger than 0.
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* @param ciphertext The cipher text array to write the encrypted data to.
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*
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* @return true on success.
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*/
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bool tox_pass_key_encrypt(const Tox_Pass_Key *key, const uint8_t *plaintext, size_t plaintext_len,
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uint8_t *ciphertext, Tox_Err_Encryption *error)
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{
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const Random *rng = system_random();
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if (rng == nullptr) {
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SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_FAILED);
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return false;
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}
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if (plaintext_len == 0 || plaintext == nullptr || key == nullptr || ciphertext == nullptr) {
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SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_NULL);
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return false;
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}
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// the output data consists of, in order:
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// salt, nonce, mac, enc_data
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// where the mac is automatically prepended by the encrypt()
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// the salt+nonce is called the prefix
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// I'm not sure what else I'm supposed to do with the salt and nonce, since we
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// need them to decrypt the data
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/* first add the magic number */
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memcpy(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH);
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ciphertext += TOX_ENC_SAVE_MAGIC_LENGTH;
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/* then add the rest prefix */
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memcpy(ciphertext, key->salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
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ciphertext += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
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uint8_t nonce[crypto_box_NONCEBYTES];
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random_nonce(rng, nonce);
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memcpy(ciphertext, nonce, crypto_box_NONCEBYTES);
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ciphertext += crypto_box_NONCEBYTES;
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/* now encrypt */
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if (encrypt_data_symmetric(key->key, nonce, plaintext, plaintext_len, ciphertext)
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!= plaintext_len + crypto_box_MACBYTES) {
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SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_FAILED);
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return false;
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}
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SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_OK);
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return true;
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}
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/**
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* Encrypts the given data with the given passphrase.
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*
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* The output array must be at least `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH`
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* bytes long. This delegates to tox_pass_key_derive and
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* tox_pass_key_encrypt.
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*
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* @param plaintext A byte array of length `plaintext_len`.
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* @param plaintext_len The length of the plain text array. Bigger than 0.
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* @param passphrase The user-provided password. Can be empty.
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* @param passphrase_len The length of the password.
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* @param ciphertext The cipher text array to write the encrypted data to.
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*
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* @return true on success.
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*/
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bool tox_pass_encrypt(const uint8_t *plaintext, size_t plaintext_len, const uint8_t *passphrase, size_t passphrase_len,
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uint8_t *ciphertext, Tox_Err_Encryption *error)
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{
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Tox_Err_Key_Derivation err;
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Tox_Pass_Key *key = tox_pass_key_derive(passphrase, passphrase_len, &err);
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if (key == nullptr) {
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if (err == TOX_ERR_KEY_DERIVATION_NULL) {
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SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_NULL);
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} else if (err == TOX_ERR_KEY_DERIVATION_FAILED) {
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SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED);
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}
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return false;
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}
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const bool result = tox_pass_key_encrypt(key, plaintext, plaintext_len, ciphertext, error);
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tox_pass_key_free(key);
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return result;
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}
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/**
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* This is the inverse of tox_pass_key_encrypt, also using only keys produced by
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* tox_pass_key_derive or tox_pass_key_derive_with_salt.
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*
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* @param ciphertext A byte array of length `ciphertext_len`.
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* @param ciphertext_len The length of the cipher text array. At least TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
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* @param plaintext The plain text array to write the decrypted data to.
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*
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* @return true on success.
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*/
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bool tox_pass_key_decrypt(const Tox_Pass_Key *key, const uint8_t *ciphertext, size_t ciphertext_len,
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uint8_t *plaintext, Tox_Err_Decryption *error)
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{
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if (ciphertext_len <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH) {
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SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_INVALID_LENGTH);
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return false;
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}
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if (ciphertext == nullptr || key == nullptr || plaintext == nullptr) {
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SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_NULL);
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return false;
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}
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if (memcmp(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
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SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_BAD_FORMAT);
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return false;
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}
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ciphertext += TOX_ENC_SAVE_MAGIC_LENGTH;
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ciphertext += crypto_pwhash_scryptsalsa208sha256_SALTBYTES; // salt only affects key derivation
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const size_t decrypt_length = ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
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uint8_t nonce[crypto_box_NONCEBYTES];
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memcpy(nonce, ciphertext, crypto_box_NONCEBYTES);
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ciphertext += crypto_box_NONCEBYTES;
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/* decrypt the ciphertext */
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if (decrypt_data_symmetric(key->key, nonce, ciphertext, decrypt_length + crypto_box_MACBYTES, plaintext)
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!= decrypt_length) {
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SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_FAILED);
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return false;
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}
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SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_OK);
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return true;
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}
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/**
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* Decrypts the given data with the given passphrase.
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*
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* The output array must be at least `ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH`
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* bytes long. This delegates to tox_pass_key_decrypt.
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*
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* @param ciphertext A byte array of length `ciphertext_len`.
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* @param ciphertext_len The length of the cipher text array. At least TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
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* @param passphrase The user-provided password. Can be empty.
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* @param passphrase_len The length of the password.
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* @param plaintext The plain text array to write the decrypted data to.
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*
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* @return true on success.
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*/
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bool tox_pass_decrypt(const uint8_t *ciphertext, size_t ciphertext_len, const uint8_t *passphrase,
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size_t passphrase_len, uint8_t *plaintext, Tox_Err_Decryption *error)
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{
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if (ciphertext_len <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH) {
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SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_INVALID_LENGTH);
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return false;
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}
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if (ciphertext == nullptr || passphrase == nullptr || plaintext == nullptr) {
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SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_NULL);
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return false;
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}
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if (memcmp(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
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SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_BAD_FORMAT);
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return false;
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}
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uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
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memcpy(salt, ciphertext + TOX_ENC_SAVE_MAGIC_LENGTH, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
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/* derive the key */
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Tox_Pass_Key *key = tox_pass_key_derive_with_salt(passphrase, passphrase_len, salt, nullptr);
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if (key == nullptr) {
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/* out of memory most likely */
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SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED);
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return false;
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}
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const bool result = tox_pass_key_decrypt(key, ciphertext, ciphertext_len, plaintext, error);
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tox_pass_key_free(key);
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return result;
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}
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/**
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* Determines whether or not the given data is encrypted by this module.
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*
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* It does this check by verifying that the magic number is the one put in
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* place by the encryption functions.
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*
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* The data must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in length.
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* If the passed byte array is smaller than required, the behaviour is
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* undefined.
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*
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* If the data pointer is NULL, the behaviour is undefined
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*
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* @return true if the data is encrypted by this module.
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*/
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bool tox_is_data_encrypted(const uint8_t *data)
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{
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return memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) == 0;
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}
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