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This adds a new routine, pg_strong_random() for generating random bytes, for use in both frontend and backend. At the moment, it's only used in the backend, but the upcoming SCRAM authentication patches need strong random numbers in libpq as well. pg_strong_random() is based on, and replaces, the existing implementation in pgcrypto. It can acquire strong random numbers from a number of sources, depending on what's available: - OpenSSL RAND_bytes(), if built with OpenSSL - On Windows, the native cryptographic functions are used - /dev/urandom Unlike the current pgcrypto function, the source is chosen by configure. That makes it easier to test different implementations, and ensures that we don't accidentally fall back to a less secure implementation, if the primary source fails. All of those methods are quite reliable, it would be pretty surprising for them to fail, so we'd rather find out by failing hard. If no strong random source is available, we fall back to using erand48(), seeded from current timestamp, like PostmasterRandom() was. That isn't cryptographically secure, but allows us to still work on platforms that don't have any of the above stronger sources. Because it's not very secure, the built-in implementation is only used if explicitly requested with --disable-strong-random. This replaces the more complicated Fortuna algorithm we used to have in pgcrypto, which is unfortunate, but all modern platforms have /dev/urandom, so it doesn't seem worth the maintenance effort to keep that. pgcrypto functions that require strong random numbers will be disabled with --disable-strong-random. Original patch by Magnus Hagander, tons of further work by Michael Paquier and me. Discussion: https://www.postgresql.org/message-id/CAB7nPqRy3krN8quR9XujMVVHYtXJ0_60nqgVc6oUk8ygyVkZsA@mail.gmail.com Discussion: https://www.postgresql.org/message-id/CAB7nPqRWkNYRRPJA7-cF+LfroYV10pvjdz6GNvxk-Eee9FypKA@mail.gmail.com
310 lines
6.4 KiB
C
310 lines
6.4 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 "px.h"
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#include "pgp.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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#ifdef HAVE_STRONG_RANDOM
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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((char *) 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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#else
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return PXE_NO_RANDOM;
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#endif
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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 componont 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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* algorihm hovers 10-70 bits above gpg values. And for
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* larger p, it uses gpg's algorihm.
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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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