summaryrefslogtreecommitdiffstats
path: root/comm/third_party/libgcrypt/cipher/elgamal.c
diff options
context:
space:
mode:
Diffstat (limited to 'comm/third_party/libgcrypt/cipher/elgamal.c')
-rw-r--r--comm/third_party/libgcrypt/cipher/elgamal.c1149
1 files changed, 1149 insertions, 0 deletions
diff --git a/comm/third_party/libgcrypt/cipher/elgamal.c b/comm/third_party/libgcrypt/cipher/elgamal.c
new file mode 100644
index 0000000000..4eb52d620b
--- /dev/null
+++ b/comm/third_party/libgcrypt/cipher/elgamal.c
@@ -0,0 +1,1149 @@
+/* Elgamal.c - Elgamal Public Key encryption
+ * Copyright (C) 1998, 2000, 2001, 2002, 2003,
+ * 2008 Free Software Foundation, Inc.
+ * Copyright (C) 2013 g10 Code GmbH
+ *
+ * This file is part of Libgcrypt.
+ *
+ * Libgcrypt is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * Libgcrypt is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * For a description of the algorithm, see:
+ * Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
+ * ISBN 0-471-11709-9. Pages 476 ff.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "g10lib.h"
+#include "mpi.h"
+#include "cipher.h"
+#include "pubkey-internal.h"
+
+
+/* Blinding is used to mitigate side-channel attacks. You may undef
+ this to speed up the operation in case the system is secured
+ against physical and network mounted side-channel attacks. */
+#define USE_BLINDING 1
+
+
+typedef struct
+{
+ gcry_mpi_t p; /* prime */
+ gcry_mpi_t g; /* group generator */
+ gcry_mpi_t y; /* g^x mod p */
+} ELG_public_key;
+
+
+typedef struct
+{
+ gcry_mpi_t p; /* prime */
+ gcry_mpi_t g; /* group generator */
+ gcry_mpi_t y; /* g^x mod p */
+ gcry_mpi_t x; /* secret exponent */
+} ELG_secret_key;
+
+
+static const char *elg_names[] =
+ {
+ "elg",
+ "openpgp-elg",
+ "openpgp-elg-sig",
+ NULL,
+ };
+
+
+static int test_keys (ELG_secret_key *sk, unsigned int nbits, int nodie);
+static gcry_mpi_t gen_k (gcry_mpi_t p, int small_k);
+static gcry_err_code_t generate (ELG_secret_key *sk, unsigned nbits,
+ gcry_mpi_t **factors);
+static int check_secret_key (ELG_secret_key *sk);
+static void do_encrypt (gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input,
+ ELG_public_key *pkey);
+static void decrypt (gcry_mpi_t output, gcry_mpi_t a, gcry_mpi_t b,
+ ELG_secret_key *skey);
+static void sign (gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input,
+ ELG_secret_key *skey);
+static int verify (gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input,
+ ELG_public_key *pkey);
+static unsigned int elg_get_nbits (gcry_sexp_t parms);
+
+
+static void (*progress_cb) (void *, const char *, int, int, int);
+static void *progress_cb_data;
+
+void
+_gcry_register_pk_elg_progress (void (*cb) (void *, const char *,
+ int, int, int),
+ void *cb_data)
+{
+ progress_cb = cb;
+ progress_cb_data = cb_data;
+}
+
+
+static void
+progress (int c)
+{
+ if (progress_cb)
+ progress_cb (progress_cb_data, "pk_elg", c, 0, 0);
+}
+
+
+/****************
+ * Michael Wiener's table on subgroup sizes to match field sizes.
+ * (floating around somewhere, probably based on the paper from
+ * Eurocrypt 96, page 332)
+ */
+static unsigned int
+wiener_map( unsigned int n )
+{
+ static struct { unsigned int p_n, q_n; } t[] =
+ { /* p q attack cost */
+ { 512, 119 }, /* 9 x 10^17 */
+ { 768, 145 }, /* 6 x 10^21 */
+ { 1024, 165 }, /* 7 x 10^24 */
+ { 1280, 183 }, /* 3 x 10^27 */
+ { 1536, 198 }, /* 7 x 10^29 */
+ { 1792, 212 }, /* 9 x 10^31 */
+ { 2048, 225 }, /* 8 x 10^33 */
+ { 2304, 237 }, /* 5 x 10^35 */
+ { 2560, 249 }, /* 3 x 10^37 */
+ { 2816, 259 }, /* 1 x 10^39 */
+ { 3072, 269 }, /* 3 x 10^40 */
+ { 3328, 279 }, /* 8 x 10^41 */
+ { 3584, 288 }, /* 2 x 10^43 */
+ { 3840, 296 }, /* 4 x 10^44 */
+ { 4096, 305 }, /* 7 x 10^45 */
+ { 4352, 313 }, /* 1 x 10^47 */
+ { 4608, 320 }, /* 2 x 10^48 */
+ { 4864, 328 }, /* 2 x 10^49 */
+ { 5120, 335 }, /* 3 x 10^50 */
+ { 0, 0 }
+ };
+ int i;
+
+ for(i=0; t[i].p_n; i++ )
+ {
+ if( n <= t[i].p_n )
+ return t[i].q_n;
+ }
+ /* Not in table - use an arbitrary high number. */
+ return n / 8 + 200;
+}
+
+static int
+test_keys ( ELG_secret_key *sk, unsigned int nbits, int nodie )
+{
+ ELG_public_key pk;
+ gcry_mpi_t test = mpi_new ( 0 );
+ gcry_mpi_t out1_a = mpi_new ( nbits );
+ gcry_mpi_t out1_b = mpi_new ( nbits );
+ gcry_mpi_t out2 = mpi_new ( nbits );
+ int failed = 0;
+
+ pk.p = sk->p;
+ pk.g = sk->g;
+ pk.y = sk->y;
+
+ _gcry_mpi_randomize ( test, nbits, GCRY_WEAK_RANDOM );
+
+ do_encrypt ( out1_a, out1_b, test, &pk );
+ decrypt ( out2, out1_a, out1_b, sk );
+ if ( mpi_cmp( test, out2 ) )
+ failed |= 1;
+
+ sign ( out1_a, out1_b, test, sk );
+ if ( !verify( out1_a, out1_b, test, &pk ) )
+ failed |= 2;
+
+ _gcry_mpi_release ( test );
+ _gcry_mpi_release ( out1_a );
+ _gcry_mpi_release ( out1_b );
+ _gcry_mpi_release ( out2 );
+
+ if (failed && !nodie)
+ log_fatal ("Elgamal test key for %s %s failed\n",
+ (failed & 1)? "encrypt+decrypt":"",
+ (failed & 2)? "sign+verify":"");
+ if (failed && DBG_CIPHER)
+ log_debug ("Elgamal test key for %s %s failed\n",
+ (failed & 1)? "encrypt+decrypt":"",
+ (failed & 2)? "sign+verify":"");
+
+ return failed;
+}
+
+
+/****************
+ * Generate a random secret exponent k from prime p, so that k is
+ * relatively prime to p-1. With SMALL_K set, k will be selected for
+ * better encryption performance - this must never be used signing!
+ */
+static gcry_mpi_t
+gen_k( gcry_mpi_t p, int small_k )
+{
+ gcry_mpi_t k = mpi_alloc_secure( 0 );
+ gcry_mpi_t temp = mpi_alloc( mpi_get_nlimbs(p) );
+ gcry_mpi_t p_1 = mpi_copy(p);
+ unsigned int orig_nbits = mpi_get_nbits(p);
+ unsigned int nbits, nbytes;
+ char *rndbuf = NULL;
+
+ if (small_k)
+ {
+ /* Using a k much lesser than p is sufficient for encryption and
+ * it greatly improves the encryption performance. We use
+ * Wiener's table and add a large safety margin. */
+ nbits = wiener_map( orig_nbits ) * 3 / 2;
+ if( nbits >= orig_nbits )
+ BUG();
+ }
+ else
+ nbits = orig_nbits;
+
+
+ nbytes = (nbits+7)/8;
+ if( DBG_CIPHER )
+ log_debug("choosing a random k\n");
+ mpi_sub_ui( p_1, p, 1);
+ for(;;)
+ {
+ if( !rndbuf || nbits < 32 )
+ {
+ xfree(rndbuf);
+ rndbuf = _gcry_random_bytes_secure( nbytes, GCRY_STRONG_RANDOM );
+ }
+ else
+ {
+ /* Change only some of the higher bits. We could improve
+ this by directly requesting more memory at the first call
+ to get_random_bytes() and use this the here maybe it is
+ easier to do this directly in random.c Anyway, it is
+ highly inlikely that we will ever reach this code. */
+ char *pp = _gcry_random_bytes_secure( 4, GCRY_STRONG_RANDOM );
+ memcpy( rndbuf, pp, 4 );
+ xfree(pp);
+ }
+ _gcry_mpi_set_buffer( k, rndbuf, nbytes, 0 );
+
+ for(;;)
+ {
+ if( !(mpi_cmp( k, p_1 ) < 0) ) /* check: k < (p-1) */
+ {
+ if( DBG_CIPHER )
+ progress('+');
+ break; /* no */
+ }
+ if( !(mpi_cmp_ui( k, 0 ) > 0) ) /* check: k > 0 */
+ {
+ if( DBG_CIPHER )
+ progress('-');
+ break; /* no */
+ }
+ if (mpi_gcd( temp, k, p_1 ))
+ goto found; /* okay, k is relative prime to (p-1) */
+ mpi_add_ui( k, k, 1 );
+ if( DBG_CIPHER )
+ progress('.');
+ }
+ }
+ found:
+ xfree (rndbuf);
+ if( DBG_CIPHER )
+ progress('\n');
+ mpi_free(p_1);
+ mpi_free(temp);
+
+ return k;
+}
+
+/****************
+ * Generate a key pair with a key of size NBITS
+ * Returns: 2 structures filled with all needed values
+ * and an array with n-1 factors of (p-1)
+ */
+static gcry_err_code_t
+generate ( ELG_secret_key *sk, unsigned int nbits, gcry_mpi_t **ret_factors )
+{
+ gcry_err_code_t rc;
+ gcry_mpi_t p; /* the prime */
+ gcry_mpi_t p_min1;
+ gcry_mpi_t g;
+ gcry_mpi_t x; /* the secret exponent */
+ gcry_mpi_t y;
+ unsigned int qbits;
+ unsigned int xbits;
+ byte *rndbuf;
+
+ p_min1 = mpi_new ( nbits );
+ qbits = wiener_map( nbits );
+ if( qbits & 1 ) /* better have a even one */
+ qbits++;
+ g = mpi_alloc(1);
+ rc = _gcry_generate_elg_prime (0, nbits, qbits, g, &p, ret_factors);
+ if (rc)
+ {
+ mpi_free (p_min1);
+ mpi_free (g);
+ return rc;
+ }
+ mpi_sub_ui(p_min1, p, 1);
+
+
+ /* Select a random number which has these properties:
+ * 0 < x < p-1
+ * This must be a very good random number because this is the
+ * secret part. The prime is public and may be shared anyway,
+ * so a random generator level of 1 is used for the prime.
+ *
+ * I don't see a reason to have a x of about the same size
+ * as the p. It should be sufficient to have one about the size
+ * of q or the later used k plus a large safety margin. Decryption
+ * will be much faster with such an x.
+ */
+ xbits = qbits * 3 / 2;
+ if( xbits >= nbits )
+ BUG();
+ x = mpi_snew ( xbits );
+ if( DBG_CIPHER )
+ log_debug("choosing a random x of size %u\n", xbits );
+ rndbuf = NULL;
+ do
+ {
+ if( DBG_CIPHER )
+ progress('.');
+ if( rndbuf )
+ { /* Change only some of the higher bits */
+ if( xbits < 16 ) /* should never happen ... */
+ {
+ xfree(rndbuf);
+ rndbuf = _gcry_random_bytes_secure ((xbits+7)/8,
+ GCRY_VERY_STRONG_RANDOM);
+ }
+ else
+ {
+ char *r = _gcry_random_bytes_secure (2, GCRY_VERY_STRONG_RANDOM);
+ memcpy(rndbuf, r, 2 );
+ xfree (r);
+ }
+ }
+ else
+ {
+ rndbuf = _gcry_random_bytes_secure ((xbits+7)/8,
+ GCRY_VERY_STRONG_RANDOM );
+ }
+ _gcry_mpi_set_buffer( x, rndbuf, (xbits+7)/8, 0 );
+ mpi_clear_highbit( x, xbits+1 );
+ }
+ while( !( mpi_cmp_ui( x, 0 )>0 && mpi_cmp( x, p_min1 )<0 ) );
+ xfree(rndbuf);
+
+ y = mpi_new (nbits);
+ mpi_powm( y, g, x, p );
+
+ if( DBG_CIPHER )
+ {
+ progress ('\n');
+ log_mpidump ("elg p", p );
+ log_mpidump ("elg g", g );
+ log_mpidump ("elg y", y );
+ log_mpidump ("elg x", x );
+ }
+
+ /* Copy the stuff to the key structures */
+ sk->p = p;
+ sk->g = g;
+ sk->y = y;
+ sk->x = x;
+
+ _gcry_mpi_release ( p_min1 );
+
+ /* Now we can test our keys (this should never fail!) */
+ test_keys ( sk, nbits - 64, 0 );
+
+ return 0;
+}
+
+
+/* Generate a key pair with a key of size NBITS not using a random
+ value for the secret key but the one given as X. This is useful to
+ implement a passphrase based decryption for a public key based
+ encryption. It has appliactions in backup systems.
+
+ Returns: A structure filled with all needed values and an array
+ with n-1 factors of (p-1). */
+static gcry_err_code_t
+generate_using_x (ELG_secret_key *sk, unsigned int nbits, gcry_mpi_t x,
+ gcry_mpi_t **ret_factors )
+{
+ gcry_err_code_t rc;
+ gcry_mpi_t p; /* The prime. */
+ gcry_mpi_t p_min1; /* The prime minus 1. */
+ gcry_mpi_t g; /* The generator. */
+ gcry_mpi_t y; /* g^x mod p. */
+ unsigned int qbits;
+ unsigned int xbits;
+
+ sk->p = NULL;
+ sk->g = NULL;
+ sk->y = NULL;
+ sk->x = NULL;
+
+ /* Do a quick check to see whether X is suitable. */
+ xbits = mpi_get_nbits (x);
+ if ( xbits < 64 || xbits >= nbits )
+ return GPG_ERR_INV_VALUE;
+
+ p_min1 = mpi_new ( nbits );
+ qbits = wiener_map ( nbits );
+ if ( (qbits & 1) ) /* Better have an even one. */
+ qbits++;
+ g = mpi_alloc (1);
+ rc = _gcry_generate_elg_prime (0, nbits, qbits, g, &p, ret_factors );
+ if (rc)
+ {
+ mpi_free (p_min1);
+ mpi_free (g);
+ return rc;
+ }
+ mpi_sub_ui (p_min1, p, 1);
+
+ if (DBG_CIPHER)
+ log_debug ("using a supplied x of size %u", xbits );
+ if ( !(mpi_cmp_ui ( x, 0 ) > 0 && mpi_cmp ( x, p_min1 ) <0 ) )
+ {
+ _gcry_mpi_release ( p_min1 );
+ _gcry_mpi_release ( p );
+ _gcry_mpi_release ( g );
+ return GPG_ERR_INV_VALUE;
+ }
+
+ y = mpi_new (nbits);
+ mpi_powm ( y, g, x, p );
+
+ if ( DBG_CIPHER )
+ {
+ progress ('\n');
+ log_mpidump ("elg p", p );
+ log_mpidump ("elg g", g );
+ log_mpidump ("elg y", y );
+ log_mpidump ("elg x", x );
+ }
+
+ /* Copy the stuff to the key structures */
+ sk->p = p;
+ sk->g = g;
+ sk->y = y;
+ sk->x = mpi_copy (x);
+
+ _gcry_mpi_release ( p_min1 );
+
+ /* Now we can test our keys. */
+ if ( test_keys ( sk, nbits - 64, 1 ) )
+ {
+ _gcry_mpi_release ( sk->p ); sk->p = NULL;
+ _gcry_mpi_release ( sk->g ); sk->g = NULL;
+ _gcry_mpi_release ( sk->y ); sk->y = NULL;
+ _gcry_mpi_release ( sk->x ); sk->x = NULL;
+ return GPG_ERR_BAD_SECKEY;
+ }
+
+ return 0;
+}
+
+
+/****************
+ * Test whether the secret key is valid.
+ * Returns: if this is a valid key.
+ */
+static int
+check_secret_key( ELG_secret_key *sk )
+{
+ int rc;
+ gcry_mpi_t y = mpi_alloc( mpi_get_nlimbs(sk->y) );
+
+ mpi_powm (y, sk->g, sk->x, sk->p);
+ rc = !mpi_cmp( y, sk->y );
+ mpi_free( y );
+ return rc;
+}
+
+
+static void
+do_encrypt(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_public_key *pkey )
+{
+ gcry_mpi_t k;
+
+ /* Note: maybe we should change the interface, so that it
+ * is possible to check that input is < p and return an
+ * error code.
+ */
+
+ k = gen_k( pkey->p, 1 );
+ mpi_powm (a, pkey->g, k, pkey->p);
+
+ /* b = (y^k * input) mod p
+ * = ((y^k mod p) * (input mod p)) mod p
+ * and because input is < p
+ * = ((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,
+ };
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-26 01:58:15 +0000