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/*
This file is part of GNUnet.
Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2013 GNUnet e.V.
GNUnet is free software: you can redistribute it and/or modify it
under the terms of the GNU Affero General Public License as published
by the Free Software Foundation, either version 3 of the License,
or (at your option) any later version.
GNUnet 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
Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file util/crypto_symmetric.c
* @brief Symmetric encryption services; combined cipher AES+TWOFISH (256-bit each)
* @author Christian Grothoff
* @author Ioana Patrascu
*/
#include "platform.h"
#include "gnunet_crypto_lib.h"
#include <gcrypt.h>
#define LOG(kind,...) GNUNET_log_from (kind, "util-crypto-symmetric", __VA_ARGS__)
/**
* Create a new SessionKey (for symmetric encryption).
*
* @param key session key to initialize
*/
void
GNUNET_CRYPTO_symmetric_create_session_key (struct GNUNET_CRYPTO_SymmetricSessionKey *key)
{
gcry_randomize (key->aes_key,
GNUNET_CRYPTO_AES_KEY_LENGTH,
GCRY_STRONG_RANDOM);
gcry_randomize (key->twofish_key,
GNUNET_CRYPTO_AES_KEY_LENGTH,
GCRY_STRONG_RANDOM);
}
/**
* Initialize AES cipher.
*
* @param handle handle to initialize
* @param sessionkey session key to use
* @param iv initialization vector to use
* @return #GNUNET_OK on success, #GNUNET_SYSERR on error
*/
static int
setup_cipher_aes (gcry_cipher_hd_t *handle,
const struct GNUNET_CRYPTO_SymmetricSessionKey *sessionkey,
const struct GNUNET_CRYPTO_SymmetricInitializationVector *iv)
{
int rc;
GNUNET_assert (0 ==
gcry_cipher_open (handle, GCRY_CIPHER_AES256,
GCRY_CIPHER_MODE_CFB, 0));
rc = gcry_cipher_setkey (*handle,
sessionkey->aes_key,
sizeof (sessionkey->aes_key));
GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
rc = gcry_cipher_setiv (*handle,
iv->aes_iv,
sizeof (iv->aes_iv));
GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
return GNUNET_OK;
}
/**
* Initialize TWOFISH cipher.
*
* @param handle handle to initialize
* @param sessionkey session key to use
* @param iv initialization vector to use
* @return #GNUNET_OK on success, #GNUNET_SYSERR on error
*/
static int
setup_cipher_twofish (gcry_cipher_hd_t *handle,
const struct GNUNET_CRYPTO_SymmetricSessionKey *sessionkey,
const struct GNUNET_CRYPTO_SymmetricInitializationVector *iv)
{
int rc;
GNUNET_assert (0 ==
gcry_cipher_open (handle, GCRY_CIPHER_TWOFISH,
GCRY_CIPHER_MODE_CFB, 0));
rc = gcry_cipher_setkey (*handle,
sessionkey->twofish_key,
sizeof (sessionkey->twofish_key));
GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
rc = gcry_cipher_setiv (*handle,
iv->twofish_iv,
sizeof (iv->twofish_iv));
GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
return GNUNET_OK;
}
/**
* Encrypt a block with a symmetric session key.
*
* @param block the block to encrypt
* @param size the size of the @a block
* @param sessionkey the key used to encrypt
* @param iv the initialization vector to use, use INITVALUE for streams
* @param result the output parameter in which to store the encrypted result
* can be the same or overlap with @c block
* @returns the size of the encrypted block, -1 for errors.
* Due to the use of CFB and therefore an effective stream cipher,
* this size should be the same as @c len.
*/
ssize_t
GNUNET_CRYPTO_symmetric_encrypt (const void *block,
size_t size,
const struct GNUNET_CRYPTO_SymmetricSessionKey *sessionkey,
const struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
void *result)
{
gcry_cipher_hd_t handle;
char tmp[size];
if (GNUNET_OK != setup_cipher_aes (&handle, sessionkey, iv))
return -1;
GNUNET_assert (0 == gcry_cipher_encrypt (handle, tmp, size, block, size));
gcry_cipher_close (handle);
if (GNUNET_OK != setup_cipher_twofish (&handle, sessionkey, iv))
return -1;
GNUNET_assert (0 == gcry_cipher_encrypt (handle, result, size, tmp, size));
gcry_cipher_close (handle);
memset (tmp, 0, sizeof (tmp));
return size;
}
/**
* Decrypt a given block with the session key.
*
* @param block the data to decrypt, encoded as returned by encrypt
* @param size the size of the @a block to decrypt
* @param sessionkey the key used to decrypt
* @param iv the initialization vector to use, use INITVALUE for streams
* @param result address to store the result at
* can be the same or overlap with @c block
* @return -1 on failure, size of decrypted block on success.
* Due to the use of CFB and therefore an effective stream cipher,
* this size should be the same as @c size.
*/
ssize_t
GNUNET_CRYPTO_symmetric_decrypt (const void *block,
size_t size,
const struct GNUNET_CRYPTO_SymmetricSessionKey *sessionkey,
const struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
void *result)
{
gcry_cipher_hd_t handle;
char tmp[size];
if (GNUNET_OK != setup_cipher_twofish (&handle, sessionkey, iv))
return -1;
GNUNET_assert (0 == gcry_cipher_decrypt (handle, tmp, size, block, size));
gcry_cipher_close (handle);
if (GNUNET_OK != setup_cipher_aes (&handle, sessionkey, iv))
return -1;
GNUNET_assert (0 == gcry_cipher_decrypt (handle, result, size, tmp, size));
gcry_cipher_close (handle);
memset (tmp, 0, sizeof (tmp));
return size;
}
/**
* @brief Derive an IV
*
* @param iv initialization vector
* @param skey session key
* @param salt salt for the derivation
* @param salt_len size of the @a salt
* @param ... pairs of void * & size_t for context chunks, terminated by NULL
*/
void
GNUNET_CRYPTO_symmetric_derive_iv (struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
const struct GNUNET_CRYPTO_SymmetricSessionKey *skey,
const void *salt,
size_t salt_len,
...)
{
va_list argp;
va_start (argp, salt_len);
GNUNET_CRYPTO_symmetric_derive_iv_v (iv, skey, salt, salt_len, argp);
va_end (argp);
}
/**
* @brief Derive an IV
*
* @param iv initialization vector
* @param skey session key
* @param salt salt for the derivation
* @param salt_len size of the salt
* @param argp pairs of void * & size_t for context chunks, terminated by NULL
*/
void
GNUNET_CRYPTO_symmetric_derive_iv_v (struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
const struct GNUNET_CRYPTO_SymmetricSessionKey *skey,
const void *salt,
size_t salt_len,
va_list argp)
{
char aes_salt[salt_len + 4];
char twofish_salt[salt_len + 4];
GNUNET_memcpy (aes_salt, salt, salt_len);
GNUNET_memcpy (&aes_salt[salt_len], "AES!", 4);
GNUNET_memcpy (twofish_salt, salt, salt_len);
GNUNET_memcpy (&twofish_salt[salt_len], "FISH", 4);
GNUNET_CRYPTO_kdf_v (iv->aes_iv,
sizeof (iv->aes_iv),
aes_salt,
salt_len + 4,
skey->aes_key,
sizeof (skey->aes_key),
argp);
GNUNET_CRYPTO_kdf_v (iv->twofish_iv,
sizeof (iv->twofish_iv),
twofish_salt,
salt_len + 4,
skey->twofish_key,
sizeof (skey->twofish_key),
argp);
}
/* end of crypto_symmetric.c */
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