src/pluto/mp_defs.c

   1 /* some multiprecision utilities
   2  * Copyright (C) 1998-2001  D. Hugh Redelmeier.
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License as published by the
   6  * Free Software Foundation; either version 2 of the License, or (at your
   7  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  11  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * for more details.
  13  */
  14
  15 #include <freeswan.h>
  16
  17 #include <utils.h>
  18 #include <asn1/asn1.h>
  19
  20 #include "constants.h"
  21 #include "defs.h"
  22 #include "mp_defs.h"
  23 #include "log.h"
  24
  25 /* Convert MP_INT to network form (binary octets, big-endian).
  26  * We do the malloc; caller must eventually do free.
  27  */
  28 chunk_t
  29 mpz_to_n(const MP_INT *mp, size_t bytes)
  30 {
  31         chunk_t r;
  32         MP_INT temp1, temp2;
  33         int i;
  34
  35         r.len = bytes;
  36         r.ptr = malloc(r.len);
  37
  38         mpz_init(&temp1);
  39         mpz_init(&temp2);
  40
  41         mpz_set(&temp1, mp);
  42
  43         for (i = r.len-1; i >= 0; i--)
  44         {
  45                 r.ptr[i] = mpz_mdivmod_ui(&temp2, NULL, &temp1, 1 << BITS_PER_BYTE);
  46                 mpz_set(&temp1, &temp2);
  47         }
  48
  49         passert(mpz_sgn(&temp1) == 0);      /* we must have done all the bits */
  50         mpz_clear(&temp1);
  51         mpz_clear(&temp2);
  52
  53         return r;
  54 }
  55
  56 /* Convert network form (binary bytes, big-endian) to MP_INT.
  57  * The *mp must not be previously mpz_inited.
  58  */
  59 void
  60 n_to_mpz(MP_INT *mp, const u_char *nbytes, size_t nlen)
  61 {
  62         size_t i;
  63
  64         mpz_init_set_ui(mp, 0);
  65
  66         for (i = 0; i != nlen; i++)
  67         {
  68                 mpz_mul_ui(mp, mp, 1 << BITS_PER_BYTE);
  69                 mpz_add_ui(mp, mp, nbytes[i]);
  70         }
  71 }
  72
  73 /*
  74  * convert a MP integer into a DER coded ASN.1 object
  75  */
  76 chunk_t
  77 asn1_integer_from_mpz(const mpz_t value)
  78 {
  79         size_t bits = mpz_sizeinbase(value, 2);  /* size in bits */
  80         size_t size = 1 + bits / BITS_PER_BYTE;  /* size in bytes */
  81         chunk_t n = mpz_to_n(value, size);
  82
  83         return asn1_wrap(ASN1_INTEGER, "m", n);
  84 }
  85