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/* openpgp-misc.c - miscellaneous functions for OpenPGP
* Copyright (C) 2021 g10 Code GmbH
*
* This file is part of GnuPG.
*
* GnuPG 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 of the License, or
* (at your option) any later version.
*
* GnuPG 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 this program; if not, see <https://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdlib.h>
#include "util.h"
#include "openpgpdefs.h"
/*
* Convert from OpenPGP-format with possible prefix, return
* libgcrypt-format of the key; That is, for Ed448/X448, return key
* with prefix removed, if any.
*/
gcry_mpi_t
openpgp_to_libgcrypt (pubkey_algo_t pkalgo, const char *curve,
gcry_mpi_t key)
{
unsigned int nbits = 0;
unsigned char *buf = NULL;
if ((pkalgo == PUBKEY_ALGO_EDDSA && !strcmp (curve, "Ed448"))
|| (pkalgo == PUBKEY_ALGO_ECDH && !strcmp (curve, "X448")))
buf = gcry_mpi_get_opaque (key, &nbits);
/* Either Ed448/X448 non-prefixed or not Ed448/X448. */
if (nbits == 0
|| (pkalgo == PUBKEY_ALGO_EDDSA && (nbits+7)/8 == (448 + 8)/8)
|| (pkalgo == PUBKEY_ALGO_ECDH && (nbits+7)/8 == 448/8))
return gcry_mpi_copy (key);
/* Ed448 or X448 prefixed. */
if (pkalgo == PUBKEY_ALGO_EDDSA)
return gcry_mpi_set_opaque_copy (NULL, buf+1, 8 + 448);
else
return gcry_mpi_set_opaque_copy (NULL, buf+1, 448);
}
/*
* Convert from libgcrypt-format with no-prefix, return OpenPGP-format
* of the key; That is, for Ed448/X448, return key with prefix added.
*/
gpg_error_t
openpgp_from_libgcrypt (int algo, gcry_mpi_t *r_key)
{
gcry_mpi_t key_mpi;
gcry_mpi_t a;
unsigned char *p;
const unsigned char *p_key;
unsigned int nbits;
unsigned int len;
key_mpi = *r_key;
*r_key = NULL;
p_key = gcry_mpi_get_opaque (key_mpi, &nbits);
len = (nbits+7)/8;
if ((algo == PUBKEY_ALGO_ECDH && len != 56)
|| (algo == PUBKEY_ALGO_EDDSA && len != 57)
|| (algo != PUBKEY_ALGO_ECDH && algo != PUBKEY_ALGO_EDDSA))
{
gcry_mpi_release (key_mpi);
return gpg_error (GPG_ERR_BAD_PUBKEY);
}
p = xtrymalloc (1 + len);
if (!p)
{
gcry_mpi_release (key_mpi);
return gpg_error_from_syserror ();
}
p[0] = 0x40;
memcpy (p+1, p_key, len);
a = gcry_mpi_set_opaque (NULL, p, len*8+7);
gcry_mpi_set_flag (a, GCRYMPI_FLAG_USER2);
*r_key = a;
gcry_mpi_release (key_mpi);
return 0;
}
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