/work/toxencryptsave/toxencryptsave.c

Source (jump to first uncovered line)
/* SPDX-License-Identifier: GPL-3.0-or-later
 * Copyright © 2016-2026 The TokTok team.
 * Copyright © 2013 Tox project.
 */

/**
 * Batch encryption functions.
 */
#include "toxencryptsave.h"

#include <sodium.h>

#include <stdlib.h>
#include <string.h>

#include "../toxcore/ccompat.h"
#include "../toxcore/crypto_core.h"
#include "../toxcore/mem.h"
#include "../toxcore/os_memory.h"
#include "../toxcore/os_random.h"
#include "../toxcore/rng.h"
#include "defines.h"

static_assert(TOX_PASS_SALT_LENGTH == crypto_pwhash_scryptsalsa208sha256_SALTBYTES,
              "TOX_PASS_SALT_LENGTH is assumed to be equal to crypto_pwhash_scryptsalsa208sha256_SALTBYTES");
static_assert(TOX_PASS_KEY_LENGTH == CRYPTO_SHARED_KEY_SIZE,
              "TOX_PASS_KEY_LENGTH is assumed to be equal to CRYPTO_SHARED_KEY_SIZE");
static_assert(TOX_PASS_ENCRYPTION_EXTRA_LENGTH == (crypto_box_MACBYTES + crypto_box_NONCEBYTES +
              crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH),
              "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)");

#define SET_ERROR_PARAMETER(param, x) \
    do {                              \
        if (param != nullptr) {       \
            *param = x;               \
        }                             \
    } while (0)

uint32_t tox_pass_salt_length(void)
{
    return TOX_PASS_SALT_LENGTH;
}
uint32_t tox_pass_key_length(void)
{
    return TOX_PASS_KEY_LENGTH;
}
uint32_t tox_pass_encryption_extra_length(void)
{
    return TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
}

struct Tox_Pass_Key {
    uint8_t salt[TOX_PASS_SALT_LENGTH];
    uint8_t key[TOX_PASS_KEY_LENGTH];
};

void tox_pass_key_free(Tox_Pass_Key *_Nullable key)
{
    if (key == nullptr) {
        return;
    }

    /* wipe sensitive state */
    crypto_memzero(key->salt, TOX_PASS_SALT_LENGTH);
    crypto_memzero(key->key, TOX_PASS_KEY_LENGTH);
    free(key);
}

/* 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.
 */

/**
 * Retrieves the salt used to encrypt the given data.
 *
 * The retrieved salt can then be passed to tox_pass_key_derive_with_salt to
 * produce the same key as was previously used. Any data encrypted with this
 * module can be used as input.
 *
 * The cipher text must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in
 * length.
 * The salt must be TOX_PASS_SALT_LENGTH bytes in length.
 * If the passed byte arrays are smaller than required, the behaviour is
 * undefined.
 *
 * If the cipher text pointer or the salt is NULL, this function returns false.
 *
 * Success does not say anything about the validity of the data, only that
 * data of the appropriate size was copied.
 *
 * @param ciphertext The encrypted data; at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes are read.
 * @param salt An array of exactly TOX_PASS_SALT_LENGTH bytes to write the salt to.
 *
 * @return true on success.
 */
bool tox_get_salt(
    const uint8_t ciphertext[TOX_PASS_ENCRYPTION_EXTRA_LENGTH],
    Tox_Pass_Salt salt, Tox_Err_Get_Salt *_Nullable error)
{
    if (ciphertext == nullptr || salt == nullptr) {
        SET_ERROR_PARAMETER(error, TOX_ERR_GET_SALT_NULL);
        return false;
    }

    if (memcmp(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
        SET_ERROR_PARAMETER(error, TOX_ERR_GET_SALT_BAD_FORMAT);
        return false;
    }

    ciphertext += TOX_ENC_SAVE_MAGIC_LENGTH;
    memcpy(salt, ciphertext, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
    SET_ERROR_PARAMETER(error, TOX_ERR_GET_SALT_OK);
    return true;
}

/**
 * Generates a secret symmetric key from the given passphrase.
 *
 * Be sure to not compromise the key! Only keep it in memory, do not write
 * it to disk.
 *
 * 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. A
 * deterministic version of this function is `tox_pass_key_derive_with_salt`.
 *
 * @param passphrase The user-provided password. Can be empty.
 * @param passphrase_len The length of the password.
 *
 * @return new symmetric key on success, NULL on failure.
 */
Tox_Pass_Key *_Nullable tox_pass_key_derive(
    const uint8_t passphrase[], size_t passphrase_len,
    Tox_Err_Key_Derivation *_Nullable error)
{
    const Random *rng = os_random();

    if (rng == nullptr) {
        SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_FAILED);
        return nullptr;
    }

    uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
    random_bytes(rng, salt, sizeof(salt));
    return tox_pass_key_derive_with_salt(passphrase, passphrase_len, salt, error);
}

/**
 * Same as above, except use the given salt for deterministic key derivation.
 *
 * @param passphrase The user-provided password. Can be empty.
 * @param passphrase_len The length of the password.
 * @param salt An array of exactly TOX_PASS_SALT_LENGTH bytes.
 *
 * @return new symmetric key on success, NULL on failure.
 */
Tox_Pass_Key *_Nullable tox_pass_key_derive_with_salt(
    const uint8_t passphrase[], size_t passphrase_len,
    const Tox_Pass_Salt salt, Tox_Err_Key_Derivation *_Nullable error)
{
    if (salt == nullptr || (passphrase == nullptr && passphrase_len != 0)) {
        SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_NULL);
        return nullptr;
    }

    uint8_t passkey[crypto_hash_sha256_BYTES];
    crypto_hash_sha256(passkey, passphrase, passphrase_len);

    uint8_t key[CRYPTO_SHARED_KEY_SIZE];

    // 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 nullptr;
    }

    crypto_memzero(passkey, crypto_hash_sha256_BYTES); /* wipe plaintext pw */

    Tox_Pass_Key *out_key = (Tox_Pass_Key *)calloc(1, sizeof(Tox_Pass_Key));

    if (out_key == nullptr) {
        SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_FAILED);
        return nullptr;
    }

    memcpy(out_key->salt, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
    memcpy(out_key->key, key, CRYPTO_SHARED_KEY_SIZE);
    SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_OK);
    return out_key;
}

/**
 * Encrypt a plain text with a key produced by tox_pass_key_derive or
 * tox_pass_key_derive_with_salt.
 *
 * The output array must be at least
 * `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long.
 *
 * @param plaintext A byte array of length `plaintext_len`.
 * @param plaintext_len The length of the plain text array. Bigger than 0.
 * @param ciphertext The cipher text array to write the encrypted data to.
 *
 * @return true on success.
 */
bool tox_pass_key_encrypt(const Tox_Pass_Key *_Nonnull key, const uint8_t plaintext[], size_t plaintext_len,
                          uint8_t ciphertext[], Tox_Err_Encryption *_Nullable error)
{
    const Memory *mem = os_memory();
    const Random *rng = os_random();

    if (mem == nullptr || rng == nullptr) {
        SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_FAILED);
        return false;
    }

    if (plaintext_len == 0 || plaintext == nullptr || key == nullptr || ciphertext == nullptr) {
        SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_NULL);
        return false;
    }

    // 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(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH);
    ciphertext += TOX_ENC_SAVE_MAGIC_LENGTH;

    /* then add the rest prefix */
    memcpy(ciphertext, key->salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
    ciphertext += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;

    uint8_t nonce[crypto_box_NONCEBYTES];
    random_nonce(rng, nonce);
    memcpy(ciphertext, nonce, crypto_box_NONCEBYTES);
    ciphertext += crypto_box_NONCEBYTES;

    /* now encrypt */
    const int32_t encrypted_len = encrypt_data_symmetric((const Memory * _Nonnull)mem, key->key, nonce, plaintext, plaintext_len, ciphertext);
    if (encrypted_len < 0 || (size_t)encrypted_len != plaintext_len + crypto_box_MACBYTES) {
        SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_FAILED);
        return false;
    }

    SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_OK);
    return true;
}

/**
 * Encrypts the given data with the given passphrase.
 *
 * The output array must be at least
 * `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long. This delegates
 * to tox_pass_key_derive and tox_pass_key_encrypt.
 *
 * @param plaintext A byte array of length `plaintext_len`.
 * @param plaintext_len The length of the plain text array. Bigger than 0.
 * @param passphrase The user-provided password. Can be empty.
 * @param passphrase_len The length of the password.
 * @param ciphertext The cipher text array to write the encrypted data to.
 *
 * @return true on success.
 */
bool tox_pass_encrypt(const uint8_t plaintext[], size_t plaintext_len, const uint8_t passphrase[], size_t passphrase_len,
                      uint8_t ciphertext[/*! plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH */], Tox_Err_Encryption *_Nullable error)
{
    Tox_Err_Key_Derivation err;
    Tox_Pass_Key *key = tox_pass_key_derive(passphrase, passphrase_len, &err);

    if (key == nullptr) {
        if (err == TOX_ERR_KEY_DERIVATION_NULL) {
            SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_NULL);
        } else if (err == TOX_ERR_KEY_DERIVATION_FAILED) {
            SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED);
        }

        return false;
    }

    const bool result = tox_pass_key_encrypt(key, plaintext, plaintext_len, ciphertext, error);
    tox_pass_key_free(key);
    return result;
}

/**
 * This is the inverse of tox_pass_key_encrypt, also using only keys produced by
 * tox_pass_key_derive or tox_pass_key_derive_with_salt.
 *
 * @param ciphertext A byte array of length `ciphertext_len`.
 * @param ciphertext_len The length of the cipher text array. At least
 *   TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
 * @param plaintext The plain text array to write the decrypted data to.
 *
 * @return true on success.
 */
bool tox_pass_key_decrypt(const Tox_Pass_Key *_Nonnull key, const uint8_t ciphertext[], size_t ciphertext_len,
                          uint8_t plaintext[], Tox_Err_Decryption *_Nullable error)
{
    const Memory *mem = os_memory();

    if (mem == nullptr) {
        SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_FAILED);
        return false;
    }

    if (ciphertext_len <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH) {
        SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_INVALID_LENGTH);
        return false;
    }

    if (ciphertext == nullptr || key == nullptr || plaintext == nullptr) {
        SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_NULL);
        return false;
    }

    if (memcmp(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
        SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_BAD_FORMAT);
        return false;
    }

    ciphertext += TOX_ENC_SAVE_MAGIC_LENGTH;
    ciphertext += crypto_pwhash_scryptsalsa208sha256_SALTBYTES; // salt only affects key derivation

    const size_t decrypt_length = ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;

    uint8_t nonce[crypto_box_NONCEBYTES];
    memcpy(nonce, ciphertext, crypto_box_NONCEBYTES);
    ciphertext += crypto_box_NONCEBYTES;

    /* decrypt the ciphertext */
    const int32_t decrypted_len = decrypt_data_symmetric((const Memory * _Nonnull)mem, key->key, nonce, ciphertext, decrypt_length + crypto_box_MACBYTES, plaintext);
    if (decrypted_len < 0 || (size_t)decrypted_len != decrypt_length) {
        SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_FAILED);
        return false;
    }

    SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_OK);
    return true;
}

/**
 * Decrypts the given data with the given passphrase.
 *
 * The output array must be at least
 * `ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long. This
 * delegates to tox_pass_key_decrypt.
 *
 * @param ciphertext A byte array of length `ciphertext_len`.
 * @param ciphertext_len The length of the cipher text array. At least
 *   TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
 * @param passphrase The user-provided password. Can be empty.
 * @param passphrase_len The length of the password.
 * @param plaintext The plain text array to write the decrypted data to.
 *
 * @return true on success.
 */
bool tox_pass_decrypt(const uint8_t ciphertext[], size_t ciphertext_len, const uint8_t passphrase[],
                      size_t passphrase_len, uint8_t plaintext[/*! ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH */], Tox_Err_Decryption *_Nullable error)
{
    if (ciphertext_len <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH) {
        SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_INVALID_LENGTH);
        return false;
    }

    if (ciphertext == nullptr || passphrase == nullptr || plaintext == nullptr) {
        SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_NULL);
        return false;
    }

    if (memcmp(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
        SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_BAD_FORMAT);
        return false;
    }

    uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
    memcpy(salt, ciphertext + TOX_ENC_SAVE_MAGIC_LENGTH, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);

    /* derive the key */
    Tox_Pass_Key *key = tox_pass_key_derive_with_salt(passphrase, passphrase_len, salt, nullptr);

    if (key == nullptr) {
        /* out of memory most likely */
        SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED);
        return false;
    }

    const bool result = tox_pass_key_decrypt(key, ciphertext, ciphertext_len, plaintext, error);
    tox_pass_key_free(key);
    return result;
}

/**
 * Determines whether or not the given data is encrypted by this module.
 *
 * It does this check by verifying that the magic number is the one put in
 * place by the encryption functions.
 *
 * The data must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in length.
 * If the passed byte array is smaller than required, the behaviour is
 * undefined.
 *
 * If the data pointer is NULL, the behaviour is undefined
 *
 * @param data The data to check; at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes are read.
 *
 * @return true if the data is encrypted by this module.
 */
bool tox_is_data_encrypted(const uint8_t data[TOX_PASS_ENCRYPTION_EXTRA_LENGTH])
{
    return memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) == 0;
}

const char *_Nonnull tox_err_key_derivation_to_string(Tox_Err_Key_Derivation error)
{
    switch (error) {
        case TOX_ERR_KEY_DERIVATION_OK:
            return "TOX_ERR_KEY_DERIVATION_OK";
        case TOX_ERR_KEY_DERIVATION_NULL:
            return "TOX_ERR_KEY_DERIVATION_NULL";
        case TOX_ERR_KEY_DERIVATION_FAILED:
            return "TOX_ERR_KEY_DERIVATION_FAILED";
    }
    return "<invalid Tox_Err_Key_Derivation>";
}

const char *_Nonnull tox_err_encryption_to_string(Tox_Err_Encryption error)
{
    switch (error) {
        case TOX_ERR_ENCRYPTION_OK:
            return "TOX_ERR_ENCRYPTION_OK";
        case TOX_ERR_ENCRYPTION_NULL:
            return "TOX_ERR_ENCRYPTION_NULL";
        case TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED:
            return "TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED";
        case TOX_ERR_ENCRYPTION_FAILED:
            return "TOX_ERR_ENCRYPTION_FAILED";
    }
    return "<invalid Tox_Err_Encryption>";
}

const char *_Nonnull tox_err_decryption_to_string(Tox_Err_Decryption error)
{
    switch (error) {
        case TOX_ERR_DECRYPTION_OK:
            return "TOX_ERR_DECRYPTION_OK";
        case TOX_ERR_DECRYPTION_NULL:
            return "TOX_ERR_DECRYPTION_NULL";
        case TOX_ERR_DECRYPTION_INVALID_LENGTH:
            return "TOX_ERR_DECRYPTION_INVALID_LENGTH";
        case TOX_ERR_DECRYPTION_BAD_FORMAT:
            return "TOX_ERR_DECRYPTION_BAD_FORMAT";
        case TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED:
            return "TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED";
        case TOX_ERR_DECRYPTION_FAILED:
            return "TOX_ERR_DECRYPTION_FAILED";
    }
    return "<invalid Tox_Err_Decryption>";
}

const char *_Nonnull tox_err_get_salt_to_string(Tox_Err_Get_Salt error)
{
    switch (error) {
        case TOX_ERR_GET_SALT_OK:
            return "TOX_ERR_GET_SALT_OK";
        case TOX_ERR_GET_SALT_NULL:
            return "TOX_ERR_GET_SALT_NULL";
        case TOX_ERR_GET_SALT_BAD_FORMAT:
            return "TOX_ERR_GET_SALT_BAD_FORMAT";
    }
    return "<invalid Tox_Err_Get_Salt>";
}

Coverage Report

Created: 2026-10-24 08:16

Line	Count	Source (jump to first uncovered line)
1		/* SPDX-License-Identifier: GPL-3.0-or-later
2		* Copyright © 2016-2026 The TokTok team.
3		* Copyright © 2013 Tox project.
4		*/
5
6		/**
7		* Batch encryption functions.
8		*/
9		#include "toxencryptsave.h"
10
11		#include <sodium.h>
12
13		#include <stdlib.h>
14		#include <string.h>
15
16		#include "../toxcore/ccompat.h"
17		#include "../toxcore/crypto_core.h"
18		#include "../toxcore/mem.h"
19		#include "../toxcore/os_memory.h"
20		#include "../toxcore/os_random.h"
21		#include "../toxcore/rng.h"
22		#include "defines.h"
23
24		static_assert(TOX_PASS_SALT_LENGTH == crypto_pwhash_scryptsalsa208sha256_SALTBYTES,
25		"TOX_PASS_SALT_LENGTH is assumed to be equal to crypto_pwhash_scryptsalsa208sha256_SALTBYTES");
26		static_assert(TOX_PASS_KEY_LENGTH == CRYPTO_SHARED_KEY_SIZE,
27		"TOX_PASS_KEY_LENGTH is assumed to be equal to CRYPTO_SHARED_KEY_SIZE");
28		static_assert(TOX_PASS_ENCRYPTION_EXTRA_LENGTH == (crypto_box_MACBYTES + crypto_box_NONCEBYTES +
29		crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH),
30		"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)");
31
32		#define SET_ERROR_PARAMETER(param, x) \
33	29	do { \
34	29	if (param != nullptr) { \
35	23	*param = x; \
36	23	} \
37	29	} while (0)
38
39		uint32_t tox_pass_salt_length(void)
40	0	{
41	0	return TOX_PASS_SALT_LENGTH;
42	0	}
43		uint32_t tox_pass_key_length(void)
44	0	{
45	0	return TOX_PASS_KEY_LENGTH;
46	0	}
47		uint32_t tox_pass_encryption_extra_length(void)
48	0	{
49	0	return TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
50	0	}
51
52		struct Tox_Pass_Key {
53		uint8_t salt[TOX_PASS_SALT_LENGTH];
54		uint8_t key[TOX_PASS_KEY_LENGTH];
55		};
56
57		void tox_pass_key_free(Tox_Pass_Key *_Nullable key)
58	13	{
59	13	if (key == nullptr) {
60	0	return;
61	0	}
62
63		/* wipe sensitive state */
64	13	crypto_memzero(key->salt, TOX_PASS_SALT_LENGTH);
65	13	crypto_memzero(key->key, TOX_PASS_KEY_LENGTH);
66	13	free(key);
67	13	}
68
69		/* Clients should consider alerting their users that, unlike plain data, if even one bit
70		* becomes corrupted, the data will be entirely unrecoverable.
71		* Ditto if they forget their password, there is no way to recover the data.
72		*/
73
74		/**
75		* Retrieves the salt used to encrypt the given data.
76		*
77		* The retrieved salt can then be passed to tox_pass_key_derive_with_salt to
78		* produce the same key as was previously used. Any data encrypted with this
79		* module can be used as input.
80		*
81		* The cipher text must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in
82		* length.
83		* The salt must be TOX_PASS_SALT_LENGTH bytes in length.
84		* If the passed byte arrays are smaller than required, the behaviour is
85		* undefined.
86		*
87		* If the cipher text pointer or the salt is NULL, this function returns false.
88		*
89		* Success does not say anything about the validity of the data, only that
90		* data of the appropriate size was copied.
91		*
92		* @param ciphertext The encrypted data; at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes are read.
93		* @param salt An array of exactly TOX_PASS_SALT_LENGTH bytes to write the salt to.
94		*
95		* @return true on success.
96		*/
97		bool tox_get_salt(
98		const uint8_t ciphertext[TOX_PASS_ENCRYPTION_EXTRA_LENGTH],
99		Tox_Pass_Salt salt, Tox_Err_Get_Salt *_Nullable error)
100	1	{
101	1	if (ciphertext == nullptr \|\| salt == nullptr) {
102	0	SET_ERROR_PARAMETER(error, TOX_ERR_GET_SALT_NULL);
103	0	return false;
104	0	}
105
106	1	if (memcmp(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
107	0	SET_ERROR_PARAMETER(error, TOX_ERR_GET_SALT_BAD_FORMAT);
108	0	return false;
109	0	}
110
111	1	ciphertext += TOX_ENC_SAVE_MAGIC_LENGTH;
112	1	memcpy(salt, ciphertext, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
113	1	SET_ERROR_PARAMETER(error, TOX_ERR_GET_SALT_OK);
114	1	return true;
115	1	}
116
117		/**
118		* Generates a secret symmetric key from the given passphrase.
119		*
120		* Be sure to not compromise the key! Only keep it in memory, do not write
121		* it to disk.
122		*
123		* Note that this function is not deterministic; to derive the same key from
124		* a password, you also must know the random salt that was used. A
125		* deterministic version of this function is `tox_pass_key_derive_with_salt`.
126		*
127		* @param passphrase The user-provided password. Can be empty.
128		* @param passphrase_len The length of the password.
129		*
130		* @return new symmetric key on success, NULL on failure.
131		*/
132		Tox_Pass_Key *_Nullable tox_pass_key_derive(
133		const uint8_t passphrase[], size_t passphrase_len,
134		Tox_Err_Key_Derivation *_Nullable error)
135	6	{
136	6	const Random *rng = os_random();
137
138	6	if (rng == nullptr) {
139	0	SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_FAILED);
140	0	return nullptr;
141	0	}
142
143	6	uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
144	6	random_bytes(rng, salt, sizeof(salt));
145	6	return tox_pass_key_derive_with_salt(passphrase, passphrase_len, salt, error);
146	6	}
147
148		/**
149		* Same as above, except use the given salt for deterministic key derivation.
150		*
151		* @param passphrase The user-provided password. Can be empty.
152		* @param passphrase_len The length of the password.
153		* @param salt An array of exactly TOX_PASS_SALT_LENGTH bytes.
154		*
155		* @return new symmetric key on success, NULL on failure.
156		*/
157		Tox_Pass_Key *_Nullable tox_pass_key_derive_with_salt(
158		const uint8_t passphrase[], size_t passphrase_len,
159		const Tox_Pass_Salt salt, Tox_Err_Key_Derivation *_Nullable error)
160	13	{
161	13	if (salt == nullptr \|\| (passphrase == nullptr && passphrase_len != 0)) {
162	0	SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_NULL);
163	0	return nullptr;
164	0	}
165
166	13	uint8_t passkey[crypto_hash_sha256_BYTES];
167	13	crypto_hash_sha256(passkey, passphrase, passphrase_len);
168
169	13	uint8_t key[CRYPTO_SHARED_KEY_SIZE];
170
171		// Derive a key from the password
172		// http://doc.libsodium.org/key_derivation/README.html
173		// note that, according to the documentation, a generic pwhash interface will be created
174		// once the pwhash competition (https://password-hashing.net/) is over */
175	13	if (crypto_pwhash_scryptsalsa208sha256(
176	13	key, sizeof(key), (char *)passkey, sizeof(passkey), salt,
177	13	crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE * 2, /* slightly stronger */
178	13	crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE) != 0) {
179		/* out of memory most likely */
180	0	SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_FAILED);
181	0	return nullptr;
182	0	}
183
184	13	crypto_memzero(passkey, crypto_hash_sha256_BYTES); /* wipe plaintext pw */
185
186	13	Tox_Pass_Key out_key = (Tox_Pass_Key )calloc(1, sizeof(Tox_Pass_Key));
187
188	13	if (out_key == nullptr) {
189	0	SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_FAILED);
190	0	return nullptr;
191	0	}
192
193	13	memcpy(out_key->salt, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
194	13	memcpy(out_key->key, key, CRYPTO_SHARED_KEY_SIZE);
195	13	SET_ERROR_PARAMETER(error, TOX_ERR_KEY_DERIVATION_OK);
196	13	return out_key;
197	13	}
198
199		/**
200		* Encrypt a plain text with a key produced by tox_pass_key_derive or
201		* tox_pass_key_derive_with_salt.
202		*
203		* The output array must be at least
204		* `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long.
205		*
206		* @param plaintext A byte array of length `plaintext_len`.
207		* @param plaintext_len The length of the plain text array. Bigger than 0.
208		* @param ciphertext The cipher text array to write the encrypted data to.
209		*
210		* @return true on success.
211		*/
212		bool tox_pass_key_encrypt(const Tox_Pass_Key *_Nonnull key, const uint8_t plaintext[], size_t plaintext_len,
213		uint8_t ciphertext[], Tox_Err_Encryption *_Nullable error)
214	6	{
215	6	const Memory *mem = os_memory();
216	6	const Random *rng = os_random();
217
218	6	if (mem == nullptr \|\| rng == nullptr) {
219	0	SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_FAILED);
220	0	return false;
221	0	}
222
223	6	if (plaintext_len == 0 \|\| plaintext == nullptr \|\| key == nullptr \|\| ciphertext == nullptr) {
224	0	SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_NULL);
225	0	return false;
226	0	}
227
228		// the output data consists of, in order:
229		// salt, nonce, mac, enc_data
230		// where the mac is automatically prepended by the encrypt()
231		// the salt+nonce is called the prefix
232		// I'm not sure what else I'm supposed to do with the salt and nonce, since we
233		// need them to decrypt the data
234
235		/* first add the magic number */
236	6	memcpy(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH);
237	6	ciphertext += TOX_ENC_SAVE_MAGIC_LENGTH;
238
239		/* then add the rest prefix */
240	6	memcpy(ciphertext, key->salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
241	6	ciphertext += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
242
243	6	uint8_t nonce[crypto_box_NONCEBYTES];
244	6	random_nonce(rng, nonce);
245	6	memcpy(ciphertext, nonce, crypto_box_NONCEBYTES);
246	6	ciphertext += crypto_box_NONCEBYTES;
247
248		/* now encrypt */
249	6	const int32_t encrypted_len = encrypt_data_symmetric((const Memory * _Nonnull)mem, key->key, nonce, plaintext, plaintext_len, ciphertext);
250	6	if (encrypted_len < 0 \|\| (size_t)encrypted_len != plaintext_len + crypto_box_MACBYTES) {
251	0	SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_FAILED);
252	0	return false;
253	0	}
254
255	6	SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_OK);
256	6	return true;
257	6	}
258
259		/**
260		* Encrypts the given data with the given passphrase.
261		*
262		* The output array must be at least
263		* `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long. This delegates
264		* to tox_pass_key_derive and tox_pass_key_encrypt.
265		*
266		* @param plaintext A byte array of length `plaintext_len`.
267		* @param plaintext_len The length of the plain text array. Bigger than 0.
268		* @param passphrase The user-provided password. Can be empty.
269		* @param passphrase_len The length of the password.
270		* @param ciphertext The cipher text array to write the encrypted data to.
271		*
272		* @return true on success.
273		*/
274		bool tox_pass_encrypt(const uint8_t plaintext[], size_t plaintext_len, const uint8_t passphrase[], size_t passphrase_len,
275		uint8_t ciphertext[/! plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH /], Tox_Err_Encryption *_Nullable error)
276	4	{
277	4	Tox_Err_Key_Derivation err;
278	4	Tox_Pass_Key *key = tox_pass_key_derive(passphrase, passphrase_len, &err);
279
280	4	if (key == nullptr) {
281	0	if (err == TOX_ERR_KEY_DERIVATION_NULL) {
282	0	SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_NULL);
283	0	} else if (err == TOX_ERR_KEY_DERIVATION_FAILED) {
284	0	SET_ERROR_PARAMETER(error, TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED);
285	0	}
286
287	0	return false;
288	0	}
289
290	4	const bool result = tox_pass_key_encrypt(key, plaintext, plaintext_len, ciphertext, error);
291	4	tox_pass_key_free(key);
292	4	return result;
293	4	}
294
295		/**
296		* This is the inverse of tox_pass_key_encrypt, also using only keys produced by
297		* tox_pass_key_derive or tox_pass_key_derive_with_salt.
298		*
299		* @param ciphertext A byte array of length `ciphertext_len`.
300		* @param ciphertext_len The length of the cipher text array. At least
301		* TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
302		* @param plaintext The plain text array to write the decrypted data to.
303		*
304		* @return true on success.
305		*/
306		bool tox_pass_key_decrypt(const Tox_Pass_Key *_Nonnull key, const uint8_t ciphertext[], size_t ciphertext_len,
307		uint8_t plaintext[], Tox_Err_Decryption *_Nullable error)
308	8	{
309	8	const Memory *mem = os_memory();
310
311	8	if (mem == nullptr) {
312	0	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_FAILED);
313	0	return false;
314	0	}
315
316	8	if (ciphertext_len <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH) {
317	0	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_INVALID_LENGTH);
318	0	return false;
319	0	}
320
321	8	if (ciphertext == nullptr \|\| key == nullptr \|\| plaintext == nullptr) {
322	0	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_NULL);
323	0	return false;
324	0	}
325
326	8	if (memcmp(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
327	0	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_BAD_FORMAT);
328	0	return false;
329	0	}
330
331	8	ciphertext += TOX_ENC_SAVE_MAGIC_LENGTH;
332	8	ciphertext += crypto_pwhash_scryptsalsa208sha256_SALTBYTES; // salt only affects key derivation
333
334	8	const size_t decrypt_length = ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
335
336	8	uint8_t nonce[crypto_box_NONCEBYTES];
337	8	memcpy(nonce, ciphertext, crypto_box_NONCEBYTES);
338	8	ciphertext += crypto_box_NONCEBYTES;
339
340		/* decrypt the ciphertext */
341	8	const int32_t decrypted_len = decrypt_data_symmetric((const Memory * _Nonnull)mem, key->key, nonce, ciphertext, decrypt_length + crypto_box_MACBYTES, plaintext);
342	8	if (decrypted_len < 0 \|\| (size_t)decrypted_len != decrypt_length) {
343	0	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_FAILED);
344	0	return false;
345	0	}
346
347	8	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_OK);
348	8	return true;
349	8	}
350
351		/**
352		* Decrypts the given data with the given passphrase.
353		*
354		* The output array must be at least
355		* `ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long. This
356		* delegates to tox_pass_key_decrypt.
357		*
358		* @param ciphertext A byte array of length `ciphertext_len`.
359		* @param ciphertext_len The length of the cipher text array. At least
360		* TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
361		* @param passphrase The user-provided password. Can be empty.
362		* @param passphrase_len The length of the password.
363		* @param plaintext The plain text array to write the decrypted data to.
364		*
365		* @return true on success.
366		*/
367		bool tox_pass_decrypt(const uint8_t ciphertext[], size_t ciphertext_len, const uint8_t passphrase[],
368		size_t passphrase_len, uint8_t plaintext[/! ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH /], Tox_Err_Decryption *_Nullable error)
369	7	{
370	7	if (ciphertext_len <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH) {
371	0	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_INVALID_LENGTH);
372	0	return false;
373	0	}
374
375	7	if (ciphertext == nullptr \|\| passphrase == nullptr \|\| plaintext == nullptr) {
376	1	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_NULL);
377	1	return false;
378	1	}
379
380	6	if (memcmp(ciphertext, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0) {
381	0	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_BAD_FORMAT);
382	0	return false;
383	0	}
384
385	6	uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
386	6	memcpy(salt, ciphertext + TOX_ENC_SAVE_MAGIC_LENGTH, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
387
388		/* derive the key */
389	6	Tox_Pass_Key *key = tox_pass_key_derive_with_salt(passphrase, passphrase_len, salt, nullptr);
390
391	6	if (key == nullptr) {
392		/* out of memory most likely */
393	0	SET_ERROR_PARAMETER(error, TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED);
394	0	return false;
395	0	}
396
397	6	const bool result = tox_pass_key_decrypt(key, ciphertext, ciphertext_len, plaintext, error);
398	6	tox_pass_key_free(key);
399	6	return result;
400	6	}
401
402		/**
403		* Determines whether or not the given data is encrypted by this module.
404		*
405		* It does this check by verifying that the magic number is the one put in
406		* place by the encryption functions.
407		*
408		* The data must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in length.
409		* If the passed byte array is smaller than required, the behaviour is
410		* undefined.
411		*
412		* If the data pointer is NULL, the behaviour is undefined
413		*
414		* @param data The data to check; at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes are read.
415		*
416		* @return true if the data is encrypted by this module.
417		*/
418		bool tox_is_data_encrypted(const uint8_t data[TOX_PASS_ENCRYPTION_EXTRA_LENGTH])
419	2	{
420	2	return memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) == 0;
421	2	}
422
423		const char *_Nonnull tox_err_key_derivation_to_string(Tox_Err_Key_Derivation error)
424	0	{
425	0	switch (error) {
426	0	case TOX_ERR_KEY_DERIVATION_OK:
427	0	return "TOX_ERR_KEY_DERIVATION_OK";
428	0	case TOX_ERR_KEY_DERIVATION_NULL:
429	0	return "TOX_ERR_KEY_DERIVATION_NULL";
430	0	case TOX_ERR_KEY_DERIVATION_FAILED:
431	0	return "TOX_ERR_KEY_DERIVATION_FAILED";
432	0	}
433	0	return "<invalid Tox_Err_Key_Derivation>";
434	0	}
435
436		const char *_Nonnull tox_err_encryption_to_string(Tox_Err_Encryption error)
437	0	{
438	0	switch (error) {
439	0	case TOX_ERR_ENCRYPTION_OK:
440	0	return "TOX_ERR_ENCRYPTION_OK";
441	0	case TOX_ERR_ENCRYPTION_NULL:
442	0	return "TOX_ERR_ENCRYPTION_NULL";
443	0	case TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED:
444	0	return "TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED";
445	0	case TOX_ERR_ENCRYPTION_FAILED:
446	0	return "TOX_ERR_ENCRYPTION_FAILED";
447	0	}
448	0	return "<invalid Tox_Err_Encryption>";
449	0	}
450
451		const char *_Nonnull tox_err_decryption_to_string(Tox_Err_Decryption error)
452	0	{
453	0	switch (error) {
454	0	case TOX_ERR_DECRYPTION_OK:
455	0	return "TOX_ERR_DECRYPTION_OK";
456	0	case TOX_ERR_DECRYPTION_NULL:
457	0	return "TOX_ERR_DECRYPTION_NULL";
458	0	case TOX_ERR_DECRYPTION_INVALID_LENGTH:
459	0	return "TOX_ERR_DECRYPTION_INVALID_LENGTH";
460	0	case TOX_ERR_DECRYPTION_BAD_FORMAT:
461	0	return "TOX_ERR_DECRYPTION_BAD_FORMAT";
462	0	case TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED:
463	0	return "TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED";
464	0	case TOX_ERR_DECRYPTION_FAILED:
465	0	return "TOX_ERR_DECRYPTION_FAILED";
466	0	}
467	0	return "<invalid Tox_Err_Decryption>";
468	0	}
469
470		const char *_Nonnull tox_err_get_salt_to_string(Tox_Err_Get_Salt error)
471	0	{
472	0	switch (error) {
473	0	case TOX_ERR_GET_SALT_OK:
474	0	return "TOX_ERR_GET_SALT_OK";
475	0	case TOX_ERR_GET_SALT_NULL:
476	0	return "TOX_ERR_GET_SALT_NULL";
477	0	case TOX_ERR_GET_SALT_BAD_FORMAT:
478	0	return "TOX_ERR_GET_SALT_BAD_FORMAT";
479	0	}
480	0	return "<invalid Tox_Err_Get_Salt>";
481	0	}