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re-refactor to separate pass->key and key->encryption

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This commit is contained in:
dubslow 2014-10-09 20:16:05 -05:00
parent e6f30694d3
commit 54fdf3bdd6
2 changed files with 110 additions and 27 deletions
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106
toxencryptsave/toxencryptsave.c
View File

@ -47,13 +47,19 @@ uint32_t tox_encrypted_size(const Tox *tox)
return tox_size(tox) + TOX_PASS_ENCRYPTION_EXTRA_LENGTH + TOX_ENC_SAVE_MAGIC_LENGTH;
}
/* Encrypts the given data with the given passphrase. The output array must be
* at least data_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long.
/* 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_pass_encrypt(uint8_t* data, uint32_t data_len, uint8_t* passphrase, uint32_t pplength, uint8_t* out)
int tox_derive_key_from_pass(uint8_t* passphrase, uint32_t pplength, uint8_t* out_key)
{
if (pplength == 0)
return -1;
@ -77,7 +83,23 @@ int tox_pass_encrypt(uint8_t* data, uint32_t data_len, uint8_t* passphrase, uint
}
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(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()
@ -88,9 +110,10 @@ int tox_pass_encrypt(uint8_t* data, uint32_t data_len, uint8_t* passphrase, uint
/* first add the prefix */
uint8_t nonce[crypto_box_NONCEBYTES];
random_nonce(nonce);
random_nonce(nonce);
memcpy(out, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
memcpy(out, key, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
key += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
out += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
memcpy(out, nonce, crypto_box_NONCEBYTES);
out += crypto_box_NONCEBYTES;
@ -104,6 +127,22 @@ int tox_pass_encrypt(uint8_t* data, uint32_t data_len, uint8_t* passphrase, uint
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(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().
*
@ -122,11 +161,39 @@ int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint3
memcpy(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH);
data += TOX_ENC_SAVE_MAGIC_LENGTH;
/* now encrypt */
return tox_pass_encrypt(temp_data, temp_size, passphrase, pplength, 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)
return -1;
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.
@ -136,26 +203,19 @@ int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint3
*/
int tox_pass_decrypt(const uint8_t* data, uint32_t length, uint8_t* passphrase, uint32_t pplength, uint8_t* out)
{
if (length <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH)
return -1;
uint32_t decrypt_length = length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
uint8_t nonce[crypto_box_NONCEBYTES];
uint8_t passkey[crypto_hash_sha256_BYTES];
crypto_hash_sha256(passkey, passphrase, pplength);
memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
data += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
memcpy(nonce, data, crypto_box_NONCEBYTES);
data += crypto_box_NONCEBYTES;
uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
/* derive the key */
uint8_t key[crypto_box_KEYBYTES];
uint8_t key[crypto_box_KEYBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
if (crypto_pwhash_scryptsalsa208sha256(
key, sizeof(key), passkey, sizeof(passkey), salt,
key + crypto_pwhash_scryptsalsa208sha256_SALTBYTES,
crypto_box_KEYBYTES, passkey, sizeof(passkey), salt,
crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE * 2, /* slightly stronger */
crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE) != 0) {
/* out of memory most likely */
@ -164,13 +224,7 @@ int tox_pass_decrypt(const uint8_t* data, uint32_t length, uint8_t* passphrase,
sodium_memzero(passkey, crypto_hash_sha256_BYTES); /* wipe plaintext pw */
/* decrypt the data */
if (decrypt_data_symmetric(key, nonce, data, decrypt_length + crypto_box_MACBYTES, out)
!= decrypt_length) {
return -1;
}
return decrypt_length;
return tox_pass_key_decrypt(data, length, key, out);
}
/* Load the messenger from encrypted data of size length.

31
toxencryptsave/toxencryptsave.h
View File

@ -38,6 +38,8 @@ typedef struct Tox Tox;
#define TOX_PASS_ENCRYPTION_EXTRA_LENGTH (crypto_box_MACBYTES + crypto_box_NONCEBYTES \
+ crypto_pwhash_scryptsalsa208sha256_SALTBYTES)
#define TOX_PASS_KEY_LENGTH (crypto_box_KEYBYTES + 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.
@ -47,8 +49,35 @@ typedef struct Tox Tox;
/* return size of the messenger data (for encrypted saving). */
uint32_t tox_encrypted_size(const Tox *tox);
/* 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);
/* 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(uint8_t* data, uint32_t data_len, const uint8_t* key, uint8_t* out);
/* Encrypts the given data with the given passphrase. The output array must be
* at least data_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long.
* at least data_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long. This delegates
* to tox_derive_key_from_pass and tox_pass_key_encrypt.
*
* tox_encrypted_save() is a good example of how to use this function.
*