305 lines
6.3 KiB
C
305 lines
6.3 KiB
C
/*
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* pgp-mpi-internal.c
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* OpenPGP MPI functions.
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*
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* Copyright (c) 2005 Marko Kreen
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* contrib/pgcrypto/pgp-mpi-internal.c
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*/
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#include "postgres.h"
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#include "imath.h"
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#include "pgp.h"
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#include "px.h"
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static mpz_t *
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mp_new()
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{
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mpz_t *mp = mp_int_alloc();
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mp_int_init_size(mp, 256);
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return mp;
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}
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static void
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mp_clear_free(mpz_t *a)
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{
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if (!a)
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return;
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/* fixme: no clear? */
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mp_int_free(a);
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}
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static int
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mp_px_rand(uint32 bits, mpz_t *res)
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{
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unsigned bytes = (bits + 7) / 8;
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int last_bits = bits & 7;
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uint8 *buf;
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buf = px_alloc(bytes);
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if (!pg_strong_random(buf, bytes))
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{
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px_free(buf);
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return PXE_NO_RANDOM;
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}
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/* clear unnecessary bits and set last bit to one */
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if (last_bits)
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{
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buf[0] >>= 8 - last_bits;
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buf[0] |= 1 << (last_bits - 1);
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}
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else
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buf[0] |= 1 << 7;
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mp_int_read_unsigned(res, buf, bytes);
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px_free(buf);
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return 0;
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}
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static void
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mp_modmul(mpz_t *a, mpz_t *b, mpz_t *p, mpz_t *res)
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{
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mpz_t *tmp = mp_new();
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mp_int_mul(a, b, tmp);
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mp_int_mod(tmp, p, res);
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mp_clear_free(tmp);
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}
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static mpz_t *
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mpi_to_bn(PGP_MPI *n)
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{
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mpz_t *bn = mp_new();
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mp_int_read_unsigned(bn, n->data, n->bytes);
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if (!bn)
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return NULL;
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if (mp_int_count_bits(bn) != n->bits)
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{
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px_debug("mpi_to_bn: bignum conversion failed: mpi=%d, bn=%d",
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n->bits, mp_int_count_bits(bn));
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mp_clear_free(bn);
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return NULL;
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}
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return bn;
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}
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static PGP_MPI *
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bn_to_mpi(mpz_t *bn)
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{
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int res;
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PGP_MPI *n;
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int bytes;
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res = pgp_mpi_alloc(mp_int_count_bits(bn), &n);
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if (res < 0)
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return NULL;
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bytes = (mp_int_count_bits(bn) + 7) / 8;
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if (bytes != n->bytes)
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{
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px_debug("bn_to_mpi: bignum conversion failed: bn=%d, mpi=%d",
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bytes, n->bytes);
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pgp_mpi_free(n);
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return NULL;
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}
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mp_int_to_unsigned(bn, n->data, n->bytes);
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return n;
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}
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/*
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* Decide the number of bits in the random component k
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*
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* It should be in the same range as p for signing (which
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* is deprecated), but can be much smaller for encrypting.
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*
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* Until I research it further, I just mimic gpg behaviour.
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* It has a special mapping table, for values <= 5120,
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* above that it uses 'arbitrary high number'. Following
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* algorithm hovers 10-70 bits above gpg values. And for
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* larger p, it uses gpg's algorithm.
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*
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* The point is - if k gets large, encryption will be
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* really slow. It does not matter for decryption.
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*/
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static int
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decide_k_bits(int p_bits)
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{
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if (p_bits <= 5120)
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return p_bits / 10 + 160;
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else
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return (p_bits / 8 + 200) * 3 / 2;
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}
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int
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pgp_elgamal_encrypt(PGP_PubKey *pk, PGP_MPI *_m,
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PGP_MPI **c1_p, PGP_MPI **c2_p)
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{
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int res = PXE_PGP_MATH_FAILED;
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int k_bits;
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mpz_t *m = mpi_to_bn(_m);
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mpz_t *p = mpi_to_bn(pk->pub.elg.p);
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mpz_t *g = mpi_to_bn(pk->pub.elg.g);
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mpz_t *y = mpi_to_bn(pk->pub.elg.y);
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mpz_t *k = mp_new();
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mpz_t *yk = mp_new();
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mpz_t *c1 = mp_new();
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mpz_t *c2 = mp_new();
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if (!m || !p || !g || !y || !k || !yk || !c1 || !c2)
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goto err;
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/*
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* generate k
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*/
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k_bits = decide_k_bits(mp_int_count_bits(p));
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res = mp_px_rand(k_bits, k);
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if (res < 0)
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return res;
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/*
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* c1 = g^k c2 = m * y^k
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*/
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mp_int_exptmod(g, k, p, c1);
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mp_int_exptmod(y, k, p, yk);
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mp_modmul(m, yk, p, c2);
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/* result */
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*c1_p = bn_to_mpi(c1);
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*c2_p = bn_to_mpi(c2);
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if (*c1_p && *c2_p)
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res = 0;
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err:
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mp_clear_free(c2);
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mp_clear_free(c1);
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mp_clear_free(yk);
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mp_clear_free(k);
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mp_clear_free(y);
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mp_clear_free(g);
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mp_clear_free(p);
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mp_clear_free(m);
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return res;
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}
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int
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pgp_elgamal_decrypt(PGP_PubKey *pk, PGP_MPI *_c1, PGP_MPI *_c2,
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PGP_MPI **msg_p)
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{
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int res = PXE_PGP_MATH_FAILED;
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mpz_t *c1 = mpi_to_bn(_c1);
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mpz_t *c2 = mpi_to_bn(_c2);
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mpz_t *p = mpi_to_bn(pk->pub.elg.p);
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mpz_t *x = mpi_to_bn(pk->sec.elg.x);
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mpz_t *c1x = mp_new();
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mpz_t *div = mp_new();
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mpz_t *m = mp_new();
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if (!c1 || !c2 || !p || !x || !c1x || !div || !m)
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goto err;
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/*
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* m = c2 / (c1^x)
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*/
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mp_int_exptmod(c1, x, p, c1x);
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mp_int_invmod(c1x, p, div);
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mp_modmul(c2, div, p, m);
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/* result */
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*msg_p = bn_to_mpi(m);
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if (*msg_p)
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res = 0;
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err:
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mp_clear_free(m);
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mp_clear_free(div);
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mp_clear_free(c1x);
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mp_clear_free(x);
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mp_clear_free(p);
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mp_clear_free(c2);
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mp_clear_free(c1);
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return res;
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}
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int
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pgp_rsa_encrypt(PGP_PubKey *pk, PGP_MPI *_m, PGP_MPI **c_p)
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{
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int res = PXE_PGP_MATH_FAILED;
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mpz_t *m = mpi_to_bn(_m);
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mpz_t *e = mpi_to_bn(pk->pub.rsa.e);
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mpz_t *n = mpi_to_bn(pk->pub.rsa.n);
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mpz_t *c = mp_new();
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if (!m || !e || !n || !c)
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goto err;
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/*
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* c = m ^ e
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*/
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mp_int_exptmod(m, e, n, c);
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*c_p = bn_to_mpi(c);
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if (*c_p)
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res = 0;
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err:
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mp_clear_free(c);
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mp_clear_free(n);
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mp_clear_free(e);
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mp_clear_free(m);
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return res;
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}
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int
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pgp_rsa_decrypt(PGP_PubKey *pk, PGP_MPI *_c, PGP_MPI **m_p)
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{
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int res = PXE_PGP_MATH_FAILED;
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mpz_t *c = mpi_to_bn(_c);
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mpz_t *d = mpi_to_bn(pk->sec.rsa.d);
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mpz_t *n = mpi_to_bn(pk->pub.rsa.n);
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mpz_t *m = mp_new();
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if (!m || !d || !n || !c)
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goto err;
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/*
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* m = c ^ d
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*/
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mp_int_exptmod(c, d, n, m);
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*m_p = bn_to_mpi(m);
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if (*m_p)
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res = 0;
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err:
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mp_clear_free(m);
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mp_clear_free(n);
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mp_clear_free(d);
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mp_clear_free(c);
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return res;
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}
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