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/*
This file is part of TALER
Copyright (C) 2014, 2015 GNUnet e.V.
TALER 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 3, or (at your option) any later version.
TALER 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
TALER; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
*/
/**
* @file util/crypto.c
* @brief Cryptographic utility functions
* @author Sree Harsha Totakura <sreeharsha@totakura.in>
* @author Florian Dold
* @author Benedikt Mueller
* @author Christian Grothoff
*/
#include "platform.h"
#if HAVE_GNUNET_GNUNET_UTIL_TALER_WALLET_LIB_H
#include "taler_util_wallet.h"
#endif
#if HAVE_GNUNET_GNUNET_UTIL_LIB_H
#include "taler_util.h"
#endif
#include <gcrypt.h>
/**
* Function called by libgcrypt on serious errors.
* Prints an error message and aborts the process.
*
* @param cls NULL
* @param wtf unknown
* @param msg error message
*/
static void
fatal_error_handler (void *cls,
int wtf,
const char *msg)
{
fprintf (stderr,
"Fatal error in libgcrypt: %s\n",
msg);
abort();
}
/**
* Initialize libgcrypt.
*/
void __attribute__ ((constructor))
TALER_gcrypt_init ()
{
gcry_set_fatalerror_handler (&fatal_error_handler,
NULL);
if (! gcry_check_version (NEED_LIBGCRYPT_VERSION))
{
fprintf (stderr,
"libgcrypt version mismatch\n");
abort ();
}
/* Disable secure memory. */
gcry_control (GCRYCTL_DISABLE_SECMEM, 0);
gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
}
/**
* Check if a coin is valid; that is, whether the denomination key exists,
* is not expired, and the signature is correct.
*
* @param coin_public_info the coin public info to check for validity
* @return #GNUNET_YES if the coin is valid,
* #GNUNET_NO if it is invalid
* #GNUNET_SYSERROR if an internal error occured
*/
int
TALER_test_coin_valid (const struct TALER_CoinPublicInfo *coin_public_info)
{
struct GNUNET_HashCode c_hash;
GNUNET_CRYPTO_hash (&coin_public_info->coin_pub,
sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey),
&c_hash);
if (GNUNET_OK !=
GNUNET_CRYPTO_rsa_verify (&c_hash,
coin_public_info->denom_sig.rsa_signature,
coin_public_info->denom_pub.rsa_public_key))
{
GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
"coin signature is invalid\n");
return GNUNET_NO;
}
return GNUNET_YES;
}
/**
* Given the coin and the transfer private keys, compute the
* transfer secret. (Technically, we only need one of the two
* private keys, but the caller currently trivially only has
* the two private keys, so we derive one of the public keys
* internally to this function.)
*
* @param coin_priv coin key
* @param trans_priv transfer private key
* @param[out] ts computed transfer secret
*/
void
TALER_link_derive_transfer_secret (const struct TALER_CoinSpendPrivateKeyP *coin_priv,
const struct TALER_TransferPrivateKeyP *trans_priv,
struct TALER_TransferSecretP *ts)
{
struct TALER_CoinSpendPublicKeyP coin_pub;
GNUNET_CRYPTO_eddsa_key_get_public (&coin_priv->eddsa_priv,
&coin_pub.eddsa_pub);
GNUNET_assert (GNUNET_OK ==
GNUNET_CRYPTO_ecdh_eddsa (&trans_priv->ecdhe_priv,
&coin_pub.eddsa_pub,
&ts->key));
}
/**
* Decrypt the shared @a secret from the information in the
* @a trans_priv and @a coin_pub.
*
* @param trans_priv transfer private key
* @param coin_pub coin public key
* @param[out] secret set to the shared secret
*/
void
TALER_link_reveal_transfer_secret (const struct TALER_TransferPrivateKeyP *trans_priv,
const struct TALER_CoinSpendPublicKeyP *coin_pub,
struct TALER_TransferSecretP *transfer_secret)
{
GNUNET_assert (GNUNET_OK ==
GNUNET_CRYPTO_ecdh_eddsa (&trans_priv->ecdhe_priv,
&coin_pub->eddsa_pub,
&transfer_secret->key));
}
/**
* Decrypt the shared @a secret from the information in the
* @a trans_priv and @a coin_pub.
*
* @param trans_pub transfer private key
* @param coin_priv coin public key
* @param[out] secret set to the shared secret
*/
void
TALER_link_recover_transfer_secret (const struct TALER_TransferPublicKeyP *trans_pub,
const struct TALER_CoinSpendPrivateKeyP *coin_priv,
struct TALER_TransferSecretP *transfer_secret)
{
GNUNET_assert (GNUNET_OK ==
GNUNET_CRYPTO_eddsa_ecdh (&coin_priv->eddsa_priv,
&trans_pub->ecdhe_pub,
&transfer_secret->key));
}
/**
* Setup information for a fresh coin.
*
* @param secret_seed seed to use for KDF to derive coin keys
* @param coin_num_salt number of the coin to include in KDF
* @param[out] fc value to initialize
*/
void
TALER_setup_fresh_coin (const struct TALER_TransferSecretP *secret_seed,
unsigned int coin_num_salt,
struct TALER_FreshCoinP *fc)
{
uint32_t be_salt = htonl (coin_num_salt);
GNUNET_assert (GNUNET_OK ==
GNUNET_CRYPTO_kdf (fc,
sizeof (*fc),
secret_seed,
sizeof (*secret_seed),
&be_salt,
sizeof (be_salt),
"taler-coin-derivation",
strlen ("taler-coin-derivation"),
NULL, 0));
/* Taken from like 170-172 of libgcrypt/cipher/ecc.c
* We note that libgcrypt stores the private key in the reverse order
* from many Ed25519 implementatons. */
fc->coin_priv[0] &= 0x7f; /* Clear bit 255. */
fc->coin_priv[0] |= 0x40; /* Set bit 254. */
fc->coin_priv[31] &= 0xf8; /* Clear bits 2..0 so that d mod 8 == 0 */
/* FIXME: Run GNUNET_CRYPTO_ecdhe_key_create several times and inspect
* the output to verify that the same bits are set and cleared.
* Is it worth also adding a test case that runs gcry_pk_testkey on
* this key after first parsing it into libgcrypt's s-expression mess
* ala decode_private_eddsa_key from gnunet/src/util/crypto_ecc.c?
* It'd run check_secret_key but not test_keys from libgcrypt/cipher/ecc.c */
}
/* end of crypto.c */
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