release/src/router/nettle/ecdsa-verify.c

   1 /* ecc-ecdsa-verify.c */
   2
   3 /* nettle, low-level cryptographics library
   4  *
   5  * Copyright (C) 2013 Niels Möller
   6  *
   7  * The nettle library is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU Lesser General Public License as published by
   9  * the Free Software Foundation; either version 2.1 of the License, or (at your
  10  * option) any later version.
  11  *
  12  * The nettle library is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  14  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  15  * License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public License
  18  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  19  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  20  * MA 02111-1301, USA.
  21  */
  22
  23 /* Development of Nettle's ECC support was funded by the .SE Internet Fund. */
  24
  25 #if HAVE_CONFIG_H
  26 # include "config.h"
  27 #endif
  28
  29 #include <assert.h>
  30 #include <stdlib.h>
  31
  32 #include "ecdsa.h"
  33 #include "ecc-internal.h"
  34
  35 int
  36 ecdsa_verify (const struct ecc_point *pub,
  37               unsigned length, const uint8_t *digest,
  38               const struct dsa_signature *signature)
  39 {
  40   mp_limb_t size = pub->ecc->size;
  41   mp_size_t itch = 2*size + ECC_ECDSA_VERIFY_ITCH (size);
  42   /* For ECC_MUL_A_WBITS == 0, at most 1512 bytes. With
  43      ECC_MUL_A_WBITS == 4, currently needs 67 * ecc->size, at most
  44      4824 bytes. Don't use stack allocation for this. */
  45   mp_limb_t *scratch = gmp_alloc_limbs (itch);
  46   int res;
  47
  48 #define rp scratch
  49 #define sp (scratch + size)
  50 #define scratch_out (scratch + 2*size)
  51
  52   if (mpz_sgn (signature->r) <= 0 || mpz_size (signature->r) > size
  53       || mpz_sgn (signature->s) <= 0 || mpz_size (signature->s) > size)
  54     return 0;
  55
  56   mpz_limbs_copy (rp, signature->r, size);
  57   mpz_limbs_copy (sp, signature->s, size);
  58
  59   res = ecc_ecdsa_verify (pub->ecc, pub->p, length, digest, rp, sp, scratch_out);
  60
  61   gmp_free_limbs (scratch, itch);
  62
  63   return res;
  64 #undef rp
  65 #undef sp
  66 #undef scratch_out
  67 }