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/*
This file is part of TALER
(C) 2014 Christian Grothoff (and other contributing authors)
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, If not, see <http://www.gnu.org/licenses/>
*/
/**
* @file crypto.c
* @brief Cryptographic utility functions
* @author Sree Harsha Totakura <sreeharsha@totakura.in>
* @author Florian Dold
* @author Benedikt Mueller
*/
#include "platform.h"
#include "taler_util.h"
#include <gnunet/gnunet_common.h>
#include <gnunet/gnunet_util_lib.h>
#include <gcrypt.h>
#define CURVE "Ed25519"
/**
* 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)
{
LOG_ERROR ("Fatal error in libgcrypt: %s\n",
msg);
abort();
}
/**
* Initialize libgcrypt.
*/
void
TALER_gcrypt_init ()
{
gcry_set_fatalerror_handler (&fatal_error_handler, NULL);
TALER_assert_as (gcry_check_version (NEED_LIBGCRYPT_VERSION),
"libgcrypt version mismatch");
/* Disable secure memory. */
gcry_control (GCRYCTL_DISABLE_SECMEM, 0);
gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
}
/**
* Derive symmetric key material for refresh operations from
* a given shared secret for link decryption.
*
* @param secret the shared secret
* @param[out] iv set to initialization vector
* @param[out] skey set to session key
*/
static void
derive_refresh_key (const struct TALER_LinkSecret *secret,
struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
struct GNUNET_CRYPTO_SymmetricSessionKey *skey)
{
static const char ctx_key[] = "taler-link-skey";
static const char ctx_iv[] = "taler-link-iv";
GNUNET_assert (GNUNET_YES ==
GNUNET_CRYPTO_kdf (skey, sizeof (struct GNUNET_CRYPTO_SymmetricSessionKey),
ctx_key, strlen (ctx_key),
secret, sizeof (struct TALER_LinkSecret),
NULL, 0));
GNUNET_assert (GNUNET_YES ==
GNUNET_CRYPTO_kdf (iv, sizeof (struct GNUNET_CRYPTO_SymmetricInitializationVector),
ctx_iv, strlen (ctx_iv),
secret, sizeof (struct TALER_LinkSecret),
NULL, 0));
}
/**
* Derive symmetric key material for refresh operations from
* a given shared secret for key decryption.
*
* @param secret the shared secret
* @param[out] iv set to initialization vector
* @param[out] skey set to session key
*/
static void
derive_transfer_key (const struct TALER_TransferSecret *secret,
struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
struct GNUNET_CRYPTO_SymmetricSessionKey *skey)
{
static const char ctx_key[] = "taler-transfer-skey";
static const char ctx_iv[] = "taler-transfer-iv";
GNUNET_assert (GNUNET_YES ==
GNUNET_CRYPTO_kdf (skey, sizeof (struct GNUNET_CRYPTO_SymmetricSessionKey),
ctx_key, strlen (ctx_key),
secret, sizeof (struct TALER_TransferSecret),
NULL, 0));
GNUNET_assert (GNUNET_YES ==
GNUNET_CRYPTO_kdf (iv, sizeof (struct GNUNET_CRYPTO_SymmetricInitializationVector),
ctx_iv, strlen (ctx_iv),
secret, sizeof (struct TALER_TransferSecret),
NULL, 0));
}
/**
* Use the @a trans_sec (from ECDHE) to decrypt the @a secret_enc
* to obtain the @a secret to decrypt the linkage data.
*
* @param secret_enc encrypted secret
* @param trans_sec transfer secret
* @param secret shared secret for refresh link decryption
* @return #GNUNET_OK on success
*/
int
TALER_transfer_decrypt (const struct TALER_EncryptedLinkSecret *secret_enc,
const struct TALER_TransferSecret *trans_sec,
struct TALER_LinkSecret *secret)
{
struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
struct GNUNET_CRYPTO_SymmetricSessionKey skey;
GNUNET_assert (sizeof (struct TALER_EncryptedLinkSecret) ==
sizeof (struct TALER_LinkSecret));
derive_transfer_key (trans_sec, &iv, &skey);
return GNUNET_CRYPTO_symmetric_decrypt (secret_enc,
sizeof (struct TALER_LinkSecret),
&skey,
&iv,
secret);
}
/**
* Use the @a trans_sec (from ECDHE) to encrypt the @a secret
* to obtain the @a secret_enc.
*
* @param secret shared secret for refresh link decryption
* @param trans_sec transfer secret
* @param secret_enc[out] encrypted secret
* @return #GNUNET_OK on success
*/
int
TALER_transfer_encrypt (const struct TALER_LinkSecret *secret,
const struct TALER_TransferSecret *trans_sec,
struct TALER_EncryptedLinkSecret *secret_enc)
{
struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
struct GNUNET_CRYPTO_SymmetricSessionKey skey;
GNUNET_assert (sizeof (struct TALER_EncryptedLinkSecret) ==
sizeof (struct TALER_LinkSecret));
derive_transfer_key (trans_sec, &iv, &skey);
return GNUNET_CRYPTO_symmetric_encrypt (secret,
sizeof (struct TALER_LinkSecret),
&skey,
&iv,
secret_enc);
}
/**
* Decrypt refresh link information.
*
* @param input encrypted refresh link data
* @param secret shared secret to use for decryption
* @return NULL on error
*/
struct TALER_RefreshLinkDecrypted *
TALER_refresh_decrypt (const struct TALER_RefreshLinkEncrypted *input,
const struct TALER_LinkSecret *secret)
{
struct TALER_RefreshLinkDecrypted *ret;
struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
struct GNUNET_CRYPTO_SymmetricSessionKey skey;
size_t buf_size = input->blinding_key_enc_size
+ sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey);
char buf[buf_size];
GNUNET_assert (input->blinding_key_enc == (const char *) &input[1]);
derive_refresh_key (secret, &iv, &skey);
if (GNUNET_OK !=
GNUNET_CRYPTO_symmetric_decrypt (input->coin_priv_enc,
buf_size,
&skey,
&iv,
buf))
return NULL;
ret = GNUNET_new (struct TALER_RefreshLinkDecrypted);
memcpy (&ret->coin_priv,
buf,
sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey));
ret->blinding_key
= GNUNET_CRYPTO_rsa_blinding_key_decode (&buf[sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey)],
input->blinding_key_enc_size);
if (NULL == ret->blinding_key)
{
GNUNET_free (ret);
return NULL;
}
return ret;
}
/**
* Encrypt refresh link information.
*
* @param input plaintext refresh link data
* @param secret shared secret to use for encryption
* @return NULL on error (should never happen)
*/
struct TALER_RefreshLinkEncrypted *
TALER_refresh_encrypt (const struct TALER_RefreshLinkDecrypted *input,
const struct TALER_LinkSecret *secret)
{
char *b_buf;
size_t b_buf_size;
struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
struct GNUNET_CRYPTO_SymmetricSessionKey skey;
struct TALER_RefreshLinkEncrypted *ret;
derive_refresh_key (secret, &iv, &skey);
b_buf_size = GNUNET_CRYPTO_rsa_blinding_key_encode (input->blinding_key,
&b_buf);
ret = GNUNET_malloc (sizeof (struct TALER_RefreshLinkEncrypted) +
b_buf_size);
ret->blinding_key_enc = (const char *) &ret[1];
ret->blinding_key_enc_size = b_buf_size;
{
size_t buf_size = b_buf_size + sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey);
char buf[buf_size];
memcpy (buf,
&input->coin_priv,
sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey));
memcpy (&buf[sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey)],
b_buf,
b_buf_size);
if (GNUNET_OK !=
GNUNET_CRYPTO_symmetric_encrypt (buf,
buf_size,
&skey,
&iv,
ret->coin_priv_enc))
{
GNUNET_free (ret);
return NULL;
}
}
return ret;
}
/* end of crypto.c */
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