1150 строки
29 KiB
C
1150 строки
29 KiB
C
/* Elgamal.c - Elgamal Public Key encryption
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* Copyright (C) 1998, 2000, 2001, 2002, 2003,
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* 2008 Free Software Foundation, Inc.
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* Copyright (C) 2013 g10 Code GmbH
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*
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* This file is part of Libgcrypt.
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*
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* Libgcrypt is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation; either version 2.1 of
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* the License, or (at your option) any later version.
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*
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* Libgcrypt is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, see <http://www.gnu.org/licenses/>.
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*
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* For a description of the algorithm, see:
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* Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
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* ISBN 0-471-11709-9. Pages 476 ff.
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*/
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "g10lib.h"
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#include "mpi.h"
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#include "cipher.h"
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#include "pubkey-internal.h"
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/* Blinding is used to mitigate side-channel attacks. You may undef
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this to speed up the operation in case the system is secured
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against physical and network mounted side-channel attacks. */
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#define USE_BLINDING 1
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typedef struct
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{
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gcry_mpi_t p; /* prime */
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gcry_mpi_t g; /* group generator */
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gcry_mpi_t y; /* g^x mod p */
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} ELG_public_key;
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typedef struct
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{
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gcry_mpi_t p; /* prime */
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gcry_mpi_t g; /* group generator */
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gcry_mpi_t y; /* g^x mod p */
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gcry_mpi_t x; /* secret exponent */
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} ELG_secret_key;
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static const char *elg_names[] =
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{
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"elg",
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"openpgp-elg",
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"openpgp-elg-sig",
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NULL,
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};
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static int test_keys (ELG_secret_key *sk, unsigned int nbits, int nodie);
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static gcry_mpi_t gen_k (gcry_mpi_t p, int small_k);
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static gcry_err_code_t generate (ELG_secret_key *sk, unsigned nbits,
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gcry_mpi_t **factors);
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static int check_secret_key (ELG_secret_key *sk);
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static void do_encrypt (gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input,
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ELG_public_key *pkey);
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static void decrypt (gcry_mpi_t output, gcry_mpi_t a, gcry_mpi_t b,
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ELG_secret_key *skey);
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static void sign (gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input,
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ELG_secret_key *skey);
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static int verify (gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input,
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ELG_public_key *pkey);
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static unsigned int elg_get_nbits (gcry_sexp_t parms);
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static void (*progress_cb) (void *, const char *, int, int, int);
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static void *progress_cb_data;
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void
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_gcry_register_pk_elg_progress (void (*cb) (void *, const char *,
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int, int, int),
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void *cb_data)
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{
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progress_cb = cb;
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progress_cb_data = cb_data;
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}
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static void
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progress (int c)
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{
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if (progress_cb)
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progress_cb (progress_cb_data, "pk_elg", c, 0, 0);
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}
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/****************
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* Michael Wiener's table on subgroup sizes to match field sizes.
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* (floating around somewhere, probably based on the paper from
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* Eurocrypt 96, page 332)
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*/
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static unsigned int
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wiener_map( unsigned int n )
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{
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static struct { unsigned int p_n, q_n; } t[] =
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{ /* p q attack cost */
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{ 512, 119 }, /* 9 x 10^17 */
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{ 768, 145 }, /* 6 x 10^21 */
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{ 1024, 165 }, /* 7 x 10^24 */
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{ 1280, 183 }, /* 3 x 10^27 */
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{ 1536, 198 }, /* 7 x 10^29 */
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{ 1792, 212 }, /* 9 x 10^31 */
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{ 2048, 225 }, /* 8 x 10^33 */
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{ 2304, 237 }, /* 5 x 10^35 */
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{ 2560, 249 }, /* 3 x 10^37 */
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{ 2816, 259 }, /* 1 x 10^39 */
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{ 3072, 269 }, /* 3 x 10^40 */
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{ 3328, 279 }, /* 8 x 10^41 */
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{ 3584, 288 }, /* 2 x 10^43 */
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{ 3840, 296 }, /* 4 x 10^44 */
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{ 4096, 305 }, /* 7 x 10^45 */
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{ 4352, 313 }, /* 1 x 10^47 */
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{ 4608, 320 }, /* 2 x 10^48 */
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{ 4864, 328 }, /* 2 x 10^49 */
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{ 5120, 335 }, /* 3 x 10^50 */
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{ 0, 0 }
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};
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int i;
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for(i=0; t[i].p_n; i++ )
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{
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if( n <= t[i].p_n )
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return t[i].q_n;
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}
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/* Not in table - use an arbitrary high number. */
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return n / 8 + 200;
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}
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static int
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test_keys ( ELG_secret_key *sk, unsigned int nbits, int nodie )
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{
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ELG_public_key pk;
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gcry_mpi_t test = mpi_new ( 0 );
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gcry_mpi_t out1_a = mpi_new ( nbits );
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gcry_mpi_t out1_b = mpi_new ( nbits );
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gcry_mpi_t out2 = mpi_new ( nbits );
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int failed = 0;
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pk.p = sk->p;
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pk.g = sk->g;
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pk.y = sk->y;
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_gcry_mpi_randomize ( test, nbits, GCRY_WEAK_RANDOM );
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do_encrypt ( out1_a, out1_b, test, &pk );
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decrypt ( out2, out1_a, out1_b, sk );
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if ( mpi_cmp( test, out2 ) )
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failed |= 1;
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sign ( out1_a, out1_b, test, sk );
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if ( !verify( out1_a, out1_b, test, &pk ) )
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failed |= 2;
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_gcry_mpi_release ( test );
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_gcry_mpi_release ( out1_a );
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_gcry_mpi_release ( out1_b );
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_gcry_mpi_release ( out2 );
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if (failed && !nodie)
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log_fatal ("Elgamal test key for %s %s failed\n",
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(failed & 1)? "encrypt+decrypt":"",
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(failed & 2)? "sign+verify":"");
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if (failed && DBG_CIPHER)
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log_debug ("Elgamal test key for %s %s failed\n",
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(failed & 1)? "encrypt+decrypt":"",
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(failed & 2)? "sign+verify":"");
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return failed;
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}
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/****************
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* Generate a random secret exponent k from prime p, so that k is
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* relatively prime to p-1. With SMALL_K set, k will be selected for
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* better encryption performance - this must never be used signing!
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*/
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static gcry_mpi_t
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gen_k( gcry_mpi_t p, int small_k )
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{
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gcry_mpi_t k = mpi_alloc_secure( 0 );
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gcry_mpi_t temp = mpi_alloc( mpi_get_nlimbs(p) );
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gcry_mpi_t p_1 = mpi_copy(p);
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unsigned int orig_nbits = mpi_get_nbits(p);
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unsigned int nbits, nbytes;
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char *rndbuf = NULL;
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if (small_k)
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{
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/* Using a k much lesser than p is sufficient for encryption and
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* it greatly improves the encryption performance. We use
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* Wiener's table and add a large safety margin. */
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nbits = wiener_map( orig_nbits ) * 3 / 2;
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if( nbits >= orig_nbits )
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BUG();
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}
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else
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nbits = orig_nbits;
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nbytes = (nbits+7)/8;
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if( DBG_CIPHER )
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log_debug("choosing a random k\n");
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mpi_sub_ui( p_1, p, 1);
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for(;;)
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{
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if( !rndbuf || nbits < 32 )
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{
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xfree(rndbuf);
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rndbuf = _gcry_random_bytes_secure( nbytes, GCRY_STRONG_RANDOM );
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}
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else
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{
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/* Change only some of the higher bits. We could improve
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this by directly requesting more memory at the first call
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to get_random_bytes() and use this the here maybe it is
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easier to do this directly in random.c Anyway, it is
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highly inlikely that we will ever reach this code. */
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char *pp = _gcry_random_bytes_secure( 4, GCRY_STRONG_RANDOM );
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memcpy( rndbuf, pp, 4 );
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xfree(pp);
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}
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_gcry_mpi_set_buffer( k, rndbuf, nbytes, 0 );
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for(;;)
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{
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if( !(mpi_cmp( k, p_1 ) < 0) ) /* check: k < (p-1) */
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{
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if( DBG_CIPHER )
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progress('+');
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break; /* no */
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}
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if( !(mpi_cmp_ui( k, 0 ) > 0) ) /* check: k > 0 */
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{
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if( DBG_CIPHER )
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progress('-');
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break; /* no */
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}
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if (mpi_gcd( temp, k, p_1 ))
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goto found; /* okay, k is relative prime to (p-1) */
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mpi_add_ui( k, k, 1 );
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if( DBG_CIPHER )
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progress('.');
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}
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}
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found:
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xfree (rndbuf);
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if( DBG_CIPHER )
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progress('\n');
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mpi_free(p_1);
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mpi_free(temp);
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return k;
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}
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/****************
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* Generate a key pair with a key of size NBITS
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* Returns: 2 structures filled with all needed values
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* and an array with n-1 factors of (p-1)
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*/
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static gcry_err_code_t
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generate ( ELG_secret_key *sk, unsigned int nbits, gcry_mpi_t **ret_factors )
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{
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gcry_err_code_t rc;
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gcry_mpi_t p; /* the prime */
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gcry_mpi_t p_min1;
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gcry_mpi_t g;
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gcry_mpi_t x; /* the secret exponent */
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gcry_mpi_t y;
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unsigned int qbits;
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unsigned int xbits;
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byte *rndbuf;
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p_min1 = mpi_new ( nbits );
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qbits = wiener_map( nbits );
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if( qbits & 1 ) /* better have a even one */
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qbits++;
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g = mpi_alloc(1);
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rc = _gcry_generate_elg_prime (0, nbits, qbits, g, &p, ret_factors);
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if (rc)
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{
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mpi_free (p_min1);
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mpi_free (g);
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return rc;
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}
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mpi_sub_ui(p_min1, p, 1);
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/* Select a random number which has these properties:
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* 0 < x < p-1
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* This must be a very good random number because this is the
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* secret part. The prime is public and may be shared anyway,
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* so a random generator level of 1 is used for the prime.
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*
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* I don't see a reason to have a x of about the same size
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* as the p. It should be sufficient to have one about the size
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* of q or the later used k plus a large safety margin. Decryption
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* will be much faster with such an x.
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*/
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xbits = qbits * 3 / 2;
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if( xbits >= nbits )
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BUG();
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x = mpi_snew ( xbits );
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if( DBG_CIPHER )
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log_debug("choosing a random x of size %u\n", xbits );
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rndbuf = NULL;
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do
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{
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if( DBG_CIPHER )
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progress('.');
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if( rndbuf )
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{ /* Change only some of the higher bits */
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if( xbits < 16 ) /* should never happen ... */
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{
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xfree(rndbuf);
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rndbuf = _gcry_random_bytes_secure ((xbits+7)/8,
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GCRY_VERY_STRONG_RANDOM);
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}
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else
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{
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char *r = _gcry_random_bytes_secure (2, GCRY_VERY_STRONG_RANDOM);
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memcpy(rndbuf, r, 2 );
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xfree (r);
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}
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}
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else
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{
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rndbuf = _gcry_random_bytes_secure ((xbits+7)/8,
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GCRY_VERY_STRONG_RANDOM );
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}
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_gcry_mpi_set_buffer( x, rndbuf, (xbits+7)/8, 0 );
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mpi_clear_highbit( x, xbits+1 );
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}
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while( !( mpi_cmp_ui( x, 0 )>0 && mpi_cmp( x, p_min1 )<0 ) );
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xfree(rndbuf);
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y = mpi_new (nbits);
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mpi_powm( y, g, x, p );
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if( DBG_CIPHER )
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{
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progress ('\n');
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log_mpidump ("elg p", p );
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log_mpidump ("elg g", g );
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log_mpidump ("elg y", y );
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log_mpidump ("elg x", x );
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}
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/* Copy the stuff to the key structures */
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sk->p = p;
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sk->g = g;
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sk->y = y;
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sk->x = x;
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_gcry_mpi_release ( p_min1 );
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/* Now we can test our keys (this should never fail!) */
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test_keys ( sk, nbits - 64, 0 );
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return 0;
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}
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/* Generate a key pair with a key of size NBITS not using a random
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value for the secret key but the one given as X. This is useful to
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implement a passphrase based decryption for a public key based
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encryption. It has appliactions in backup systems.
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Returns: A structure filled with all needed values and an array
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with n-1 factors of (p-1). */
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static gcry_err_code_t
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generate_using_x (ELG_secret_key *sk, unsigned int nbits, gcry_mpi_t x,
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gcry_mpi_t **ret_factors )
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{
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gcry_err_code_t rc;
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gcry_mpi_t p; /* The prime. */
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gcry_mpi_t p_min1; /* The prime minus 1. */
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gcry_mpi_t g; /* The generator. */
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gcry_mpi_t y; /* g^x mod p. */
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unsigned int qbits;
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unsigned int xbits;
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sk->p = NULL;
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sk->g = NULL;
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sk->y = NULL;
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sk->x = NULL;
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/* Do a quick check to see whether X is suitable. */
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xbits = mpi_get_nbits (x);
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if ( xbits < 64 || xbits >= nbits )
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return GPG_ERR_INV_VALUE;
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p_min1 = mpi_new ( nbits );
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qbits = wiener_map ( nbits );
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if ( (qbits & 1) ) /* Better have an even one. */
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qbits++;
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g = mpi_alloc (1);
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rc = _gcry_generate_elg_prime (0, nbits, qbits, g, &p, ret_factors );
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if (rc)
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{
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mpi_free (p_min1);
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mpi_free (g);
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return rc;
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}
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mpi_sub_ui (p_min1, p, 1);
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if (DBG_CIPHER)
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log_debug ("using a supplied x of size %u", xbits );
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if ( !(mpi_cmp_ui ( x, 0 ) > 0 && mpi_cmp ( x, p_min1 ) <0 ) )
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{
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_gcry_mpi_release ( p_min1 );
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_gcry_mpi_release ( p );
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_gcry_mpi_release ( g );
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return GPG_ERR_INV_VALUE;
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}
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y = mpi_new (nbits);
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mpi_powm ( y, g, x, p );
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if ( DBG_CIPHER )
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{
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progress ('\n');
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log_mpidump ("elg p", p );
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log_mpidump ("elg g", g );
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log_mpidump ("elg y", y );
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log_mpidump ("elg x", x );
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}
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/* Copy the stuff to the key structures */
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sk->p = p;
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sk->g = g;
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sk->y = y;
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sk->x = mpi_copy (x);
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_gcry_mpi_release ( p_min1 );
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/* Now we can test our keys. */
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if ( test_keys ( sk, nbits - 64, 1 ) )
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{
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_gcry_mpi_release ( sk->p ); sk->p = NULL;
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_gcry_mpi_release ( sk->g ); sk->g = NULL;
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_gcry_mpi_release ( sk->y ); sk->y = NULL;
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_gcry_mpi_release ( sk->x ); sk->x = NULL;
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return GPG_ERR_BAD_SECKEY;
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}
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return 0;
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}
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/****************
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* Test whether the secret key is valid.
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* Returns: if this is a valid key.
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*/
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static int
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check_secret_key( ELG_secret_key *sk )
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{
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int rc;
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gcry_mpi_t y = mpi_alloc( mpi_get_nlimbs(sk->y) );
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mpi_powm (y, sk->g, sk->x, sk->p);
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rc = !mpi_cmp( y, sk->y );
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mpi_free( y );
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return rc;
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}
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static void
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do_encrypt(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_public_key *pkey )
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{
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gcry_mpi_t k;
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/* Note: maybe we should change the interface, so that it
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* is possible to check that input is < p and return an
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* error code.
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*/
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k = gen_k( pkey->p, 1 );
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mpi_powm (a, pkey->g, k, pkey->p);
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/* b = (y^k * input) mod p
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* = ((y^k mod p) * (input mod p)) mod p
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* and because input is < p
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||
* = ((y^k mod p) * input) mod p
|
||
*/
|
||
mpi_powm (b, pkey->y, k, pkey->p);
|
||
mpi_mulm (b, b, input, pkey->p);
|
||
#if 0
|
||
if( DBG_CIPHER )
|
||
{
|
||
log_mpidump("elg encrypted y", pkey->y);
|
||
log_mpidump("elg encrypted p", pkey->p);
|
||
log_mpidump("elg encrypted k", k);
|
||
log_mpidump("elg encrypted M", input);
|
||
log_mpidump("elg encrypted a", a);
|
||
log_mpidump("elg encrypted b", b);
|
||
}
|
||
#endif
|
||
mpi_free(k);
|
||
}
|
||
|
||
|
||
|
||
|
||
static void
|
||
decrypt (gcry_mpi_t output, gcry_mpi_t a, gcry_mpi_t b, ELG_secret_key *skey )
|
||
{
|
||
gcry_mpi_t t1, t2, r;
|
||
unsigned int nbits = mpi_get_nbits (skey->p);
|
||
|
||
mpi_normalize (a);
|
||
mpi_normalize (b);
|
||
|
||
t1 = mpi_snew (nbits);
|
||
|
||
#ifdef USE_BLINDING
|
||
|
||
t2 = mpi_snew (nbits);
|
||
r = mpi_new (nbits);
|
||
|
||
/* We need a random number of about the prime size. The random
|
||
number merely needs to be unpredictable; thus we use level 0. */
|
||
_gcry_mpi_randomize (r, nbits, GCRY_WEAK_RANDOM);
|
||
|
||
/* t1 = r^x mod p */
|
||
mpi_powm (t1, r, skey->x, skey->p);
|
||
/* t2 = (a * r)^-x mod p */
|
||
mpi_mulm (t2, a, r, skey->p);
|
||
mpi_powm (t2, t2, skey->x, skey->p);
|
||
mpi_invm (t2, t2, skey->p);
|
||
/* t1 = (t1 * t2) mod p*/
|
||
mpi_mulm (t1, t1, t2, skey->p);
|
||
|
||
mpi_free (r);
|
||
mpi_free (t2);
|
||
|
||
#else /*!USE_BLINDING*/
|
||
|
||
/* output = b/(a^x) mod p */
|
||
mpi_powm (t1, a, skey->x, skey->p);
|
||
mpi_invm (t1, t1, skey->p);
|
||
|
||
#endif /*!USE_BLINDING*/
|
||
|
||
mpi_mulm (output, b, t1, skey->p);
|
||
|
||
#if 0
|
||
if( DBG_CIPHER )
|
||
{
|
||
log_mpidump ("elg decrypted x", skey->x);
|
||
log_mpidump ("elg decrypted p", skey->p);
|
||
log_mpidump ("elg decrypted a", a);
|
||
log_mpidump ("elg decrypted b", b);
|
||
log_mpidump ("elg decrypted M", output);
|
||
}
|
||
#endif
|
||
mpi_free (t1);
|
||
}
|
||
|
||
|
||
/****************
|
||
* Make an Elgamal signature out of INPUT
|
||
*/
|
||
|
||
static void
|
||
sign(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_secret_key *skey )
|
||
{
|
||
gcry_mpi_t k;
|
||
gcry_mpi_t t = mpi_alloc( mpi_get_nlimbs(a) );
|
||
gcry_mpi_t inv = mpi_alloc( mpi_get_nlimbs(a) );
|
||
gcry_mpi_t p_1 = mpi_copy(skey->p);
|
||
|
||
/*
|
||
* b = (t * inv) mod (p-1)
|
||
* b = (t * inv(k,(p-1),(p-1)) mod (p-1)
|
||
* b = (((M-x*a) mod (p-1)) * inv(k,(p-1),(p-1))) mod (p-1)
|
||
*
|
||
*/
|
||
mpi_sub_ui(p_1, p_1, 1);
|
||
k = gen_k( skey->p, 0 /* no small K ! */ );
|
||
mpi_powm( a, skey->g, k, skey->p );
|
||
mpi_mul(t, skey->x, a );
|
||
mpi_subm(t, input, t, p_1 );
|
||
mpi_invm(inv, k, p_1 );
|
||
mpi_mulm(b, t, inv, p_1 );
|
||
|
||
#if 0
|
||
if( DBG_CIPHER )
|
||
{
|
||
log_mpidump ("elg sign p", skey->p);
|
||
log_mpidump ("elg sign g", skey->g);
|
||
log_mpidump ("elg sign y", skey->y);
|
||
log_mpidump ("elg sign x", skey->x);
|
||
log_mpidump ("elg sign k", k);
|
||
log_mpidump ("elg sign M", input);
|
||
log_mpidump ("elg sign a", a);
|
||
log_mpidump ("elg sign b", b);
|
||
}
|
||
#endif
|
||
mpi_free(k);
|
||
mpi_free(t);
|
||
mpi_free(inv);
|
||
mpi_free(p_1);
|
||
}
|
||
|
||
|
||
/****************
|
||
* Returns true if the signature composed of A and B is valid.
|
||
*/
|
||
static int
|
||
verify(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_public_key *pkey )
|
||
{
|
||
int rc;
|
||
gcry_mpi_t t1;
|
||
gcry_mpi_t t2;
|
||
gcry_mpi_t base[4];
|
||
gcry_mpi_t ex[4];
|
||
|
||
if( !(mpi_cmp_ui( a, 0 ) > 0 && mpi_cmp( a, pkey->p ) < 0) )
|
||
return 0; /* assertion 0 < a < p failed */
|
||
|
||
t1 = mpi_alloc( mpi_get_nlimbs(a) );
|
||
t2 = mpi_alloc( mpi_get_nlimbs(a) );
|
||
|
||
#if 0
|
||
/* t1 = (y^a mod p) * (a^b mod p) mod p */
|
||
gcry_mpi_powm( t1, pkey->y, a, pkey->p );
|
||
gcry_mpi_powm( t2, a, b, pkey->p );
|
||
mpi_mulm( t1, t1, t2, pkey->p );
|
||
|
||
/* t2 = g ^ input mod p */
|
||
gcry_mpi_powm( t2, pkey->g, input, pkey->p );
|
||
|
||
rc = !mpi_cmp( t1, t2 );
|
||
#elif 0
|
||
/* t1 = (y^a mod p) * (a^b mod p) mod p */
|
||
base[0] = pkey->y; ex[0] = a;
|
||
base[1] = a; ex[1] = b;
|
||
base[2] = NULL; ex[2] = NULL;
|
||
mpi_mulpowm( t1, base, ex, pkey->p );
|
||
|
||
/* t2 = g ^ input mod p */
|
||
gcry_mpi_powm( t2, pkey->g, input, pkey->p );
|
||
|
||
rc = !mpi_cmp( t1, t2 );
|
||
#else
|
||
/* t1 = g ^ - input * y ^ a * a ^ b mod p */
|
||
mpi_invm(t2, pkey->g, pkey->p );
|
||
base[0] = t2 ; ex[0] = input;
|
||
base[1] = pkey->y; ex[1] = a;
|
||
base[2] = a; ex[2] = b;
|
||
base[3] = NULL; ex[3] = NULL;
|
||
mpi_mulpowm( t1, base, ex, pkey->p );
|
||
rc = !mpi_cmp_ui( t1, 1 );
|
||
|
||
#endif
|
||
|
||
mpi_free(t1);
|
||
mpi_free(t2);
|
||
return rc;
|
||
}
|
||
|
||
/*********************************************
|
||
************** interface ******************
|
||
*********************************************/
|
||
|
||
static gpg_err_code_t
|
||
elg_generate (const gcry_sexp_t genparms, gcry_sexp_t *r_skey)
|
||
{
|
||
gpg_err_code_t rc;
|
||
unsigned int nbits;
|
||
ELG_secret_key sk;
|
||
gcry_mpi_t xvalue = NULL;
|
||
gcry_sexp_t l1;
|
||
gcry_mpi_t *factors = NULL;
|
||
gcry_sexp_t misc_info = NULL;
|
||
|
||
memset (&sk, 0, sizeof sk);
|
||
|
||
rc = _gcry_pk_util_get_nbits (genparms, &nbits);
|
||
if (rc)
|
||
return rc;
|
||
|
||
/* Parse the optional xvalue element. */
|
||
l1 = sexp_find_token (genparms, "xvalue", 0);
|
||
if (l1)
|
||
{
|
||
xvalue = sexp_nth_mpi (l1, 1, 0);
|
||
sexp_release (l1);
|
||
if (!xvalue)
|
||
return GPG_ERR_BAD_MPI;
|
||
}
|
||
|
||
if (xvalue)
|
||
{
|
||
rc = generate_using_x (&sk, nbits, xvalue, &factors);
|
||
mpi_free (xvalue);
|
||
}
|
||
else
|
||
{
|
||
rc = generate (&sk, nbits, &factors);
|
||
}
|
||
if (rc)
|
||
goto leave;
|
||
|
||
if (factors && factors[0])
|
||
{
|
||
int nfac;
|
||
void **arg_list;
|
||
char *buffer, *p;
|
||
|
||
for (nfac = 0; factors[nfac]; nfac++)
|
||
;
|
||
arg_list = xtrycalloc (nfac+1, sizeof *arg_list);
|
||
if (!arg_list)
|
||
{
|
||
rc = gpg_err_code_from_syserror ();
|
||
goto leave;
|
||
}
|
||
buffer = xtrymalloc (30 + nfac*2 + 2 + 1);
|
||
if (!buffer)
|
||
{
|
||
rc = gpg_err_code_from_syserror ();
|
||
xfree (arg_list);
|
||
goto leave;
|
||
}
|
||
p = stpcpy (buffer, "(misc-key-info(pm1-factors");
|
||
for(nfac = 0; factors[nfac]; nfac++)
|
||
{
|
||
p = stpcpy (p, "%m");
|
||
arg_list[nfac] = factors + nfac;
|
||
}
|
||
p = stpcpy (p, "))");
|
||
rc = sexp_build_array (&misc_info, NULL, buffer, arg_list);
|
||
xfree (arg_list);
|
||
xfree (buffer);
|
||
if (rc)
|
||
goto leave;
|
||
}
|
||
|
||
rc = sexp_build (r_skey, NULL,
|
||
"(key-data"
|
||
" (public-key"
|
||
" (elg(p%m)(g%m)(y%m)))"
|
||
" (private-key"
|
||
" (elg(p%m)(g%m)(y%m)(x%m)))"
|
||
" %S)",
|
||
sk.p, sk.g, sk.y,
|
||
sk.p, sk.g, sk.y, sk.x,
|
||
misc_info);
|
||
|
||
leave:
|
||
mpi_free (sk.p);
|
||
mpi_free (sk.g);
|
||
mpi_free (sk.y);
|
||
mpi_free (sk.x);
|
||
sexp_release (misc_info);
|
||
if (factors)
|
||
{
|
||
gcry_mpi_t *mp;
|
||
for (mp = factors; *mp; mp++)
|
||
mpi_free (*mp);
|
||
xfree (factors);
|
||
}
|
||
|
||
return rc;
|
||
}
|
||
|
||
|
||
static gcry_err_code_t
|
||
elg_check_secret_key (gcry_sexp_t keyparms)
|
||
{
|
||
gcry_err_code_t rc;
|
||
ELG_secret_key sk = {NULL, NULL, NULL, NULL};
|
||
|
||
rc = sexp_extract_param (keyparms, NULL, "pgyx",
|
||
&sk.p, &sk.g, &sk.y, &sk.x,
|
||
NULL);
|
||
if (rc)
|
||
goto leave;
|
||
|
||
if (!check_secret_key (&sk))
|
||
rc = GPG_ERR_BAD_SECKEY;
|
||
|
||
leave:
|
||
_gcry_mpi_release (sk.p);
|
||
_gcry_mpi_release (sk.g);
|
||
_gcry_mpi_release (sk.y);
|
||
_gcry_mpi_release (sk.x);
|
||
if (DBG_CIPHER)
|
||
log_debug ("elg_testkey => %s\n", gpg_strerror (rc));
|
||
return rc;
|
||
}
|
||
|
||
|
||
static gcry_err_code_t
|
||
elg_encrypt (gcry_sexp_t *r_ciph, gcry_sexp_t s_data, gcry_sexp_t keyparms)
|
||
{
|
||
gcry_err_code_t rc;
|
||
struct pk_encoding_ctx ctx;
|
||
gcry_mpi_t mpi_a = NULL;
|
||
gcry_mpi_t mpi_b = NULL;
|
||
gcry_mpi_t data = NULL;
|
||
ELG_public_key pk = { NULL, NULL, NULL };
|
||
|
||
_gcry_pk_util_init_encoding_ctx (&ctx, PUBKEY_OP_ENCRYPT,
|
||
elg_get_nbits (keyparms));
|
||
|
||
/* Extract the data. */
|
||
rc = _gcry_pk_util_data_to_mpi (s_data, &data, &ctx);
|
||
if (rc)
|
||
goto leave;
|
||
if (DBG_CIPHER)
|
||
log_mpidump ("elg_encrypt data", data);
|
||
if (mpi_is_opaque (data))
|
||
{
|
||
rc = GPG_ERR_INV_DATA;
|
||
goto leave;
|
||
}
|
||
|
||
/* Extract the key. */
|
||
rc = sexp_extract_param (keyparms, NULL, "pgy",
|
||
&pk.p, &pk.g, &pk.y, NULL);
|
||
if (rc)
|
||
goto leave;
|
||
if (DBG_CIPHER)
|
||
{
|
||
log_mpidump ("elg_encrypt p", pk.p);
|
||
log_mpidump ("elg_encrypt g", pk.g);
|
||
log_mpidump ("elg_encrypt y", pk.y);
|
||
}
|
||
|
||
/* Do Elgamal computation and build result. */
|
||
mpi_a = mpi_new (0);
|
||
mpi_b = mpi_new (0);
|
||
do_encrypt (mpi_a, mpi_b, data, &pk);
|
||
rc = sexp_build (r_ciph, NULL, "(enc-val(elg(a%m)(b%m)))", mpi_a, mpi_b);
|
||
|
||
leave:
|
||
_gcry_mpi_release (mpi_a);
|
||
_gcry_mpi_release (mpi_b);
|
||
_gcry_mpi_release (pk.p);
|
||
_gcry_mpi_release (pk.g);
|
||
_gcry_mpi_release (pk.y);
|
||
_gcry_mpi_release (data);
|
||
_gcry_pk_util_free_encoding_ctx (&ctx);
|
||
if (DBG_CIPHER)
|
||
log_debug ("elg_encrypt => %s\n", gpg_strerror (rc));
|
||
return rc;
|
||
}
|
||
|
||
|
||
static gcry_err_code_t
|
||
elg_decrypt (gcry_sexp_t *r_plain, gcry_sexp_t s_data, gcry_sexp_t keyparms)
|
||
{
|
||
gpg_err_code_t rc;
|
||
struct pk_encoding_ctx ctx;
|
||
gcry_sexp_t l1 = NULL;
|
||
gcry_mpi_t data_a = NULL;
|
||
gcry_mpi_t data_b = NULL;
|
||
ELG_secret_key sk = {NULL, NULL, NULL, NULL};
|
||
gcry_mpi_t plain = NULL;
|
||
unsigned char *unpad = NULL;
|
||
size_t unpadlen = 0;
|
||
|
||
_gcry_pk_util_init_encoding_ctx (&ctx, PUBKEY_OP_DECRYPT,
|
||
elg_get_nbits (keyparms));
|
||
|
||
/* Extract the data. */
|
||
rc = _gcry_pk_util_preparse_encval (s_data, elg_names, &l1, &ctx);
|
||
if (rc)
|
||
goto leave;
|
||
rc = sexp_extract_param (l1, NULL, "ab", &data_a, &data_b, NULL);
|
||
if (rc)
|
||
goto leave;
|
||
if (DBG_CIPHER)
|
||
{
|
||
log_printmpi ("elg_decrypt d_a", data_a);
|
||
log_printmpi ("elg_decrypt d_b", data_b);
|
||
}
|
||
if (mpi_is_opaque (data_a) || mpi_is_opaque (data_b))
|
||
{
|
||
rc = GPG_ERR_INV_DATA;
|
||
goto leave;
|
||
}
|
||
|
||
/* Extract the key. */
|
||
rc = sexp_extract_param (keyparms, NULL, "pgyx",
|
||
&sk.p, &sk.g, &sk.y, &sk.x,
|
||
NULL);
|
||
if (rc)
|
||
goto leave;
|
||
if (DBG_CIPHER)
|
||
{
|
||
log_printmpi ("elg_decrypt p", sk.p);
|
||
log_printmpi ("elg_decrypt g", sk.g);
|
||
log_printmpi ("elg_decrypt y", sk.y);
|
||
if (!fips_mode ())
|
||
log_printmpi ("elg_decrypt x", sk.x);
|
||
}
|
||
|
||
plain = mpi_snew (ctx.nbits);
|
||
decrypt (plain, data_a, data_b, &sk);
|
||
if (DBG_CIPHER)
|
||
log_printmpi ("elg_decrypt res", plain);
|
||
|
||
/* Reverse the encoding and build the s-expression. */
|
||
switch (ctx.encoding)
|
||
{
|
||
case PUBKEY_ENC_PKCS1:
|
||
rc = _gcry_rsa_pkcs1_decode_for_enc (&unpad, &unpadlen, ctx.nbits, plain);
|
||
mpi_free (plain); plain = NULL;
|
||
if (!rc)
|
||
rc = sexp_build (r_plain, NULL, "(value %b)", (int)unpadlen, unpad);
|
||
break;
|
||
|
||
case PUBKEY_ENC_OAEP:
|
||
rc = _gcry_rsa_oaep_decode (&unpad, &unpadlen,
|
||
ctx.nbits, ctx.hash_algo, plain,
|
||
ctx.label, ctx.labellen);
|
||
mpi_free (plain); plain = NULL;
|
||
if (!rc)
|
||
rc = sexp_build (r_plain, NULL, "(value %b)", (int)unpadlen, unpad);
|
||
break;
|
||
|
||
default:
|
||
/* Raw format. For backward compatibility we need to assume a
|
||
signed mpi by using the sexp format string "%m". */
|
||
rc = sexp_build (r_plain, NULL,
|
||
(ctx.flags & PUBKEY_FLAG_LEGACYRESULT)
|
||
? "%m" : "(value %m)",
|
||
plain);
|
||
break;
|
||
}
|
||
|
||
|
||
leave:
|
||
xfree (unpad);
|
||
_gcry_mpi_release (plain);
|
||
_gcry_mpi_release (sk.p);
|
||
_gcry_mpi_release (sk.g);
|
||
_gcry_mpi_release (sk.y);
|
||
_gcry_mpi_release (sk.x);
|
||
_gcry_mpi_release (data_a);
|
||
_gcry_mpi_release (data_b);
|
||
sexp_release (l1);
|
||
_gcry_pk_util_free_encoding_ctx (&ctx);
|
||
if (DBG_CIPHER)
|
||
log_debug ("elg_decrypt => %s\n", gpg_strerror (rc));
|
||
return rc;
|
||
}
|
||
|
||
|
||
static gcry_err_code_t
|
||
elg_sign (gcry_sexp_t *r_sig, gcry_sexp_t s_data, gcry_sexp_t keyparms)
|
||
{
|
||
gcry_err_code_t rc;
|
||
struct pk_encoding_ctx ctx;
|
||
gcry_mpi_t data = NULL;
|
||
ELG_secret_key sk = {NULL, NULL, NULL, NULL};
|
||
gcry_mpi_t sig_r = NULL;
|
||
gcry_mpi_t sig_s = NULL;
|
||
|
||
_gcry_pk_util_init_encoding_ctx (&ctx, PUBKEY_OP_SIGN,
|
||
elg_get_nbits (keyparms));
|
||
|
||
/* Extract the data. */
|
||
rc = _gcry_pk_util_data_to_mpi (s_data, &data, &ctx);
|
||
if (rc)
|
||
goto leave;
|
||
if (DBG_CIPHER)
|
||
log_mpidump ("elg_sign data", data);
|
||
if (mpi_is_opaque (data))
|
||
{
|
||
rc = GPG_ERR_INV_DATA;
|
||
goto leave;
|
||
}
|
||
|
||
/* Extract the key. */
|
||
rc = sexp_extract_param (keyparms, NULL, "pgyx",
|
||
&sk.p, &sk.g, &sk.y, &sk.x, NULL);
|
||
if (rc)
|
||
goto leave;
|
||
if (DBG_CIPHER)
|
||
{
|
||
log_mpidump ("elg_sign p", sk.p);
|
||
log_mpidump ("elg_sign g", sk.g);
|
||
log_mpidump ("elg_sign y", sk.y);
|
||
if (!fips_mode ())
|
||
log_mpidump ("elg_sign x", sk.x);
|
||
}
|
||
|
||
sig_r = mpi_new (0);
|
||
sig_s = mpi_new (0);
|
||
sign (sig_r, sig_s, data, &sk);
|
||
if (DBG_CIPHER)
|
||
{
|
||
log_mpidump ("elg_sign sig_r", sig_r);
|
||
log_mpidump ("elg_sign sig_s", sig_s);
|
||
}
|
||
rc = sexp_build (r_sig, NULL, "(sig-val(elg(r%M)(s%M)))", sig_r, sig_s);
|
||
|
||
leave:
|
||
_gcry_mpi_release (sig_r);
|
||
_gcry_mpi_release (sig_s);
|
||
_gcry_mpi_release (sk.p);
|
||
_gcry_mpi_release (sk.g);
|
||
_gcry_mpi_release (sk.y);
|
||
_gcry_mpi_release (sk.x);
|
||
_gcry_mpi_release (data);
|
||
_gcry_pk_util_free_encoding_ctx (&ctx);
|
||
if (DBG_CIPHER)
|
||
log_debug ("elg_sign => %s\n", gpg_strerror (rc));
|
||
return rc;
|
||
}
|
||
|
||
|
||
static gcry_err_code_t
|
||
elg_verify (gcry_sexp_t s_sig, gcry_sexp_t s_data, gcry_sexp_t s_keyparms)
|
||
{
|
||
gcry_err_code_t rc;
|
||
struct pk_encoding_ctx ctx;
|
||
gcry_sexp_t l1 = NULL;
|
||
gcry_mpi_t sig_r = NULL;
|
||
gcry_mpi_t sig_s = NULL;
|
||
gcry_mpi_t data = NULL;
|
||
ELG_public_key pk = { NULL, NULL, NULL };
|
||
|
||
_gcry_pk_util_init_encoding_ctx (&ctx, PUBKEY_OP_VERIFY,
|
||
elg_get_nbits (s_keyparms));
|
||
|
||
/* Extract the data. */
|
||
rc = _gcry_pk_util_data_to_mpi (s_data, &data, &ctx);
|
||
if (rc)
|
||
goto leave;
|
||
if (DBG_CIPHER)
|
||
log_mpidump ("elg_verify data", data);
|
||
if (mpi_is_opaque (data))
|
||
{
|
||
rc = GPG_ERR_INV_DATA;
|
||
goto leave;
|
||
}
|
||
|
||
/* Extract the signature value. */
|
||
rc = _gcry_pk_util_preparse_sigval (s_sig, elg_names, &l1, NULL);
|
||
if (rc)
|
||
goto leave;
|
||
rc = sexp_extract_param (l1, NULL, "rs", &sig_r, &sig_s, NULL);
|
||
if (rc)
|
||
goto leave;
|
||
if (DBG_CIPHER)
|
||
{
|
||
log_mpidump ("elg_verify s_r", sig_r);
|
||
log_mpidump ("elg_verify s_s", sig_s);
|
||
}
|
||
|
||
/* Extract the key. */
|
||
rc = sexp_extract_param (s_keyparms, NULL, "pgy",
|
||
&pk.p, &pk.g, &pk.y, NULL);
|
||
if (rc)
|
||
goto leave;
|
||
if (DBG_CIPHER)
|
||
{
|
||
log_mpidump ("elg_verify p", pk.p);
|
||
log_mpidump ("elg_verify g", pk.g);
|
||
log_mpidump ("elg_verify y", pk.y);
|
||
}
|
||
|
||
/* Verify the signature. */
|
||
if (!verify (sig_r, sig_s, data, &pk))
|
||
rc = GPG_ERR_BAD_SIGNATURE;
|
||
|
||
leave:
|
||
_gcry_mpi_release (pk.p);
|
||
_gcry_mpi_release (pk.g);
|
||
_gcry_mpi_release (pk.y);
|
||
_gcry_mpi_release (data);
|
||
_gcry_mpi_release (sig_r);
|
||
_gcry_mpi_release (sig_s);
|
||
sexp_release (l1);
|
||
_gcry_pk_util_free_encoding_ctx (&ctx);
|
||
if (DBG_CIPHER)
|
||
log_debug ("elg_verify => %s\n", rc?gpg_strerror (rc):"Good");
|
||
return rc;
|
||
}
|
||
|
||
|
||
/* Return the number of bits for the key described by PARMS. On error
|
||
* 0 is returned. The format of PARMS starts with the algorithm name;
|
||
* for example:
|
||
*
|
||
* (dsa
|
||
* (p <mpi>)
|
||
* (g <mpi>)
|
||
* (y <mpi>))
|
||
*
|
||
* More parameters may be given but we only need P here.
|
||
*/
|
||
static unsigned int
|
||
elg_get_nbits (gcry_sexp_t parms)
|
||
{
|
||
gcry_sexp_t l1;
|
||
gcry_mpi_t p;
|
||
unsigned int nbits;
|
||
|
||
l1 = sexp_find_token (parms, "p", 1);
|
||
if (!l1)
|
||
return 0; /* Parameter P not found. */
|
||
|
||
p= sexp_nth_mpi (l1, 1, GCRYMPI_FMT_USG);
|
||
sexp_release (l1);
|
||
nbits = p? mpi_get_nbits (p) : 0;
|
||
_gcry_mpi_release (p);
|
||
return nbits;
|
||
}
|
||
|
||
|
||
|
||
gcry_pk_spec_t _gcry_pubkey_spec_elg =
|
||
{
|
||
GCRY_PK_ELG, { 0, 0 },
|
||
(GCRY_PK_USAGE_SIGN | GCRY_PK_USAGE_ENCR),
|
||
"ELG", elg_names,
|
||
"pgy", "pgyx", "ab", "rs", "pgy",
|
||
elg_generate,
|
||
elg_check_secret_key,
|
||
elg_encrypt,
|
||
elg_decrypt,
|
||
elg_sign,
|
||
elg_verify,
|
||
elg_get_nbits,
|
||
};
|