postgresql/contrib/pgcrypto/pgp-mpi-internal.c
2020-05-21 08:31:16 -07:00

305 lines
6.3 KiB
C

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