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/*
This file is part of GNUnet.
Copyright (C) 2012, 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_mpi.c
* @brief Helper functions for libgcrypt MPIs
* @author Christian Grothoff
* @author Florian Dold
*/
#include "platform.h"
#include <gcrypt.h>
#include "gnunet_crypto_lib.h"
#define LOG(kind,...) GNUNET_log_from (kind, "util-crypto-mpi", __VA_ARGS__)
/**
* Log an error message at log-level 'level' that indicates
* a failure of the command 'cmd' with the message given
* by gcry_strerror(rc).
*/
#define LOG_GCRY(level, cmd, rc) do { LOG(level, _("`%s' failed at %s:%d with error: %s\n"), cmd, __FILE__, __LINE__, gcry_strerror(rc)); } while(0)
/**
* If target != size, move @a target bytes to the end of the size-sized
* buffer and zero out the first @a target - @a size bytes.
*
* @param buf original buffer
* @param size number of bytes in @a buf
* @param target target size of the buffer
*/
static void
adjust (void *buf,
size_t size,
size_t target)
{
char *p = buf;
if (size < target)
{
memmove (&p[target - size], buf, size);
memset (buf, 0, target - size);
}
}
/**
* Output the given MPI value to the given buffer in
* network byte order.
* The MPI @a val may not be negative.
*
* @param buf where to output to
* @param size number of bytes in @a buf
* @param val value to write to @a buf
*/
void
GNUNET_CRYPTO_mpi_print_unsigned (void *buf,
size_t size,
gcry_mpi_t val)
{
size_t rsize;
int rc;
if (gcry_mpi_get_flag (val, GCRYMPI_FLAG_OPAQUE))
{
/* Store opaque MPIs left aligned into the buffer. */
unsigned int nbits;
const void *p;
p = gcry_mpi_get_opaque (val, &nbits);
GNUNET_assert (p);
rsize = (nbits+7)/8;
if (rsize > size)
rsize = size;
GNUNET_memcpy (buf, p, rsize);
if (rsize < size)
memset (buf+rsize, 0, size - rsize);
}
else
{
/* Store regular MPIs as unsigned integers right aligned into
the buffer. */
rsize = size;
if (0 !=
(rc = gcry_mpi_print (GCRYMPI_FMT_USG,
buf,
rsize, &rsize,
val)))
{
LOG_GCRY (GNUNET_ERROR_TYPE_ERROR,
"gcry_mpi_print",
rc);
GNUNET_assert (0);
}
adjust (buf, rsize, size);
}
}
/**
* Convert data buffer into MPI value.
* The buffer is interpreted as network
* byte order, unsigned integer.
*
* @param result where to store MPI value (allocated)
* @param data raw data (GCRYMPI_FMT_USG)
* @param size number of bytes in @a data
*/
void
GNUNET_CRYPTO_mpi_scan_unsigned (gcry_mpi_t *result,
const void *data,
size_t size)
{
int rc;
if (0 != (rc = gcry_mpi_scan (result,
GCRYMPI_FMT_USG,
data, size, &size)))
{
LOG_GCRY (GNUNET_ERROR_TYPE_ERROR,
"gcry_mpi_scan",
rc);
GNUNET_assert (0);
}
}
/* end of crypto_mpi.c */
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