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/*
This file is part of GNUnet.
(C) 2001, 2002, 2003, 2004, 2005, 2006 Christian Grothoff (and other contributing authors)
GNUnet 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 2, 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNUnet; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
/**
* @file util/crypto_aes.c
* @brief Symmetric encryption services.
* @author Christian Grothoff
* @author Ioana Patrascu
*/
#include "platform.h"
#include "gnunet_common.h"
#include "gnunet_crypto_lib.h"
#include <gcrypt.h>
#define LOG(kind,...) GNUNET_log_from (kind, "util", __VA_ARGS__)
/**
* Create a new SessionKey (for AES-256).
*
* @param key session key to initialize
*/
void
GNUNET_CRYPTO_aes_create_session_key (struct GNUNET_CRYPTO_AesSessionKey *key)
{
gcry_randomize (&key->key[0], GNUNET_CRYPTO_AES_KEY_LENGTH,
GCRY_STRONG_RANDOM);
key->crc32 =
htonl (GNUNET_CRYPTO_crc32_n (key, GNUNET_CRYPTO_AES_KEY_LENGTH));
}
/**
* Check that a new session key is well-formed.
*
* @return GNUNET_OK if the key is valid
*/
int
GNUNET_CRYPTO_aes_check_session_key (const struct GNUNET_CRYPTO_AesSessionKey
*key)
{
uint32_t crc;
crc = GNUNET_CRYPTO_crc32_n (key, GNUNET_CRYPTO_AES_KEY_LENGTH);
if (ntohl (key->crc32) != crc)
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
return GNUNET_OK;
}
/**
* 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 (gcry_cipher_hd_t *handle,
const struct GNUNET_CRYPTO_AesSessionKey *
sessionkey,
const struct GNUNET_CRYPTO_AesInitializationVector *
iv)
{
int rc;
if (GNUNET_OK !=
GNUNET_CRYPTO_aes_check_session_key (sessionkey))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
GNUNET_assert (0 ==
gcry_cipher_open (handle, GCRY_CIPHER_AES256,
GCRY_CIPHER_MODE_CFB, 0));
rc = gcry_cipher_setkey (*handle, sessionkey, GNUNET_CRYPTO_AES_KEY_LENGTH);
GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
rc = gcry_cipher_setiv (*handle, iv,
sizeof (struct
GNUNET_CRYPTO_AesInitializationVector));
GNUNET_assert ((0 == rc) || ((char) rc == GPG_ERR_WEAK_KEY));
return GNUNET_OK;
}
/**
* Encrypt a block with the public key of another
* host that uses the same cyper.
*
* @param block the block to encrypt
* @param len the size of the 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
* @returns the size of the encrypted block, -1 for errors
*/
ssize_t
GNUNET_CRYPTO_aes_encrypt (const void *block, size_t len,
const struct GNUNET_CRYPTO_AesSessionKey *
sessionkey,
const struct GNUNET_CRYPTO_AesInitializationVector *
iv, void *result)
{
gcry_cipher_hd_t handle;
if (GNUNET_OK != setup_cipher (&handle, sessionkey, iv))
return -1;
GNUNET_assert (0 == gcry_cipher_encrypt (handle, result, len, block, len));
gcry_cipher_close (handle);
return len;
}
/**
* Decrypt a given block with the sessionkey.
*
* @param block the data to decrypt, encoded as returned by encrypt
* @param size the size of the 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
* @return -1 on failure, size of decrypted block on success
*/
ssize_t
GNUNET_CRYPTO_aes_decrypt (const void *block, size_t size,
const struct GNUNET_CRYPTO_AesSessionKey *
sessionkey,
const struct GNUNET_CRYPTO_AesInitializationVector *
iv, void *result)
{
gcry_cipher_hd_t handle;
if (GNUNET_OK != setup_cipher (&handle, sessionkey, iv))
return -1;
GNUNET_assert (0 == gcry_cipher_decrypt (handle, result, size, block, size));
gcry_cipher_close (handle);
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 salt
* @param ... pairs of void * & size_t for context chunks, terminated by NULL
*/
void
GNUNET_CRYPTO_aes_derive_iv (struct GNUNET_CRYPTO_AesInitializationVector *iv,
const struct GNUNET_CRYPTO_AesSessionKey *skey,
const void *salt, size_t salt_len, ...)
{
va_list argp;
va_start (argp, salt_len);
GNUNET_CRYPTO_aes_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_aes_derive_iv_v (struct GNUNET_CRYPTO_AesInitializationVector *iv,
const struct GNUNET_CRYPTO_AesSessionKey *skey,
const void *salt, size_t salt_len, va_list argp)
{
GNUNET_CRYPTO_kdf_v (iv->iv, sizeof (iv->iv), salt, salt_len, skey->key,
sizeof (skey->key), argp);
}
/* end of crypto_aes.c */
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