pkcs1-rsa-md5.c 2.54 KB
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/* pkcs1-rsa-md5.c
 *
 * PKCS stuff for rsa-md5.
 */

/* nettle, low-level cryptographics library
 *
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 * Copyright (C) 2001, 2003 Niels Möller
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 *  
 * The nettle library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * The nettle library 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 Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

#if HAVE_CONFIG_H
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# include "config.h"
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#endif

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#include <assert.h>
#include <stdlib.h>
#include <string.h>

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#include "rsa.h"

#include "bignum.h"
#include "pkcs1.h"

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#include "nettle-internal.h"

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/* From pkcs-1v2
 *
 *   md5 OBJECT IDENTIFIER ::=
 *     {iso(1) member-body(2) US(840) rsadsi(113549) digestAlgorithm(2) 5}
 *
 * The parameters part of the algorithm identifier is NULL:
 *
 *   md5Identifier ::= AlgorithmIdentifier {md5, NULL}
 */

static const uint8_t
md5_prefix[] =
{
  /* 18 octets prefix, 16 octets hash, 34 total. */
  0x30,       32, /* SEQUENCE */
    0x30,     12, /* SEQUENCE */
      0x06,    8, /* OBJECT IDENTIFIER */
  	0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05,
      0x05,    0, /* NULL */
    0x04,     16  /* OCTET STRING */
      /* Here comes the raw hash value */
};

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int
pkcs1_rsa_md5_encode(mpz_t m, unsigned size, struct md5_ctx *hash)
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{
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  TMP_DECL(em, uint8_t, NETTLE_MAX_BIGNUM_SIZE);
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  TMP_ALLOC(em, size);
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  if (pkcs1_signature_prefix(size, em,
			     sizeof(md5_prefix),
			     md5_prefix,
			     MD5_DIGEST_SIZE))
    {
      md5_digest(hash, MD5_DIGEST_SIZE, em + size - MD5_DIGEST_SIZE);
      nettle_mpz_set_str_256_u(m, size, em);
      return 1;
    }
  else
    return 0;
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}

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int
pkcs1_rsa_md5_encode_digest(mpz_t m, unsigned size, const uint8_t *digest)
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{
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  TMP_DECL(em, uint8_t, NETTLE_MAX_BIGNUM_SIZE);
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  TMP_ALLOC(em, size);
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  if (pkcs1_signature_prefix(size, em,
			     sizeof(md5_prefix),
			     md5_prefix,
			     MD5_DIGEST_SIZE))
    {
      memcpy(em + size - MD5_DIGEST_SIZE, digest, MD5_DIGEST_SIZE);
      nettle_mpz_set_str_256_u(m, size, em);
      return 1;
    }
  else
    return 0;
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}