Git initHEAD2.0_alphamaster2.0alpha1.0_post

1 files changed, 496 insertions, 0 deletions

diff --git a/cipher/dsa.c b/cipher/dsa.c
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+/* dsa.c  -  DSA signature algorithm
+ * Copyright (C) 1998, 1999, 2000, 2003, 2006 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+ * USA.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include "util.h"
+#include "mpi.h"
+#include "cipher.h"
+#include "dsa.h"
+
+typedef struct {
+    MPI p;	    /* prime */
+    MPI q;	    /* group order */
+    MPI g;	    /* group generator */
+    MPI y;	    /* g^x mod p */
+} DSA_public_key;
+
+
+typedef struct {
+    MPI p;	    /* prime */
+    MPI q;	    /* group order */
+    MPI g;	    /* group generator */
+    MPI y;	    /* g^x mod p */
+    MPI x;	    /* secret exponent */
+} DSA_secret_key;
+
+
+static MPI gen_k( MPI q );
+static void test_keys( DSA_secret_key *sk, unsigned qbits );
+static int  check_secret_key( DSA_secret_key *sk );
+static void generate( DSA_secret_key *sk, unsigned nbits, unsigned qbits,
+		      MPI **ret_factors );
+static void sign(MPI r, MPI s, MPI input, DSA_secret_key *skey);
+static int  verify(MPI r, MPI s, MPI input, DSA_public_key *pkey);
+
+
+static void (*progress_cb) ( void *, int );
+static void *progress_cb_data;
+
+void
+register_pk_dsa_progress ( void (*cb)( void *, 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, c );
+    else
+	fputc( c, stderr );
+}
+
+
+
+/****************
+ * Generate a random secret exponent k less than q
+ */
+static MPI
+gen_k( MPI q )
+{
+    MPI k = mpi_alloc_secure( mpi_get_nlimbs(q) );
+    unsigned int nbits = mpi_get_nbits(q);
+    unsigned int nbytes = (nbits+7)/8;
+    char *rndbuf = NULL;
+
+    if( DBG_CIPHER )
+	log_debug("choosing a random k ");
+    for(;;) {
+	if( DBG_CIPHER )
+	    progress('.');
+
+	if( !rndbuf || nbits < 32 ) {
+	    xfree(rndbuf);
+	    rndbuf = get_random_bits( nbits, 1, 1 );
+	}
+	else { /* change only some of the higher bits */
+	    /* we could imporove this by directly requesting more memory
+	     * at the first call to get_random_bits() and use this the here
+	     * maybe it is easier to do this directly in random.c */
+	    char *pp = get_random_bits( 32, 1, 1 );
+	    memcpy( rndbuf,pp, 4 );
+	    xfree(pp);
+	}
+	mpi_set_buffer( k, rndbuf, nbytes, 0 );
+	if( mpi_test_bit( k, nbits-1 ) )
+	    mpi_set_highbit( k, nbits-1 );
+	else {
+	    mpi_set_highbit( k, nbits-1 );
+	    mpi_clear_bit( k, nbits-1 );
+	}
+
+	if( !(mpi_cmp( k, q ) < 0) ) {	/* check: k < q */
+	    if( DBG_CIPHER )
+		progress('+');
+	    continue; /* no  */
+	}
+	if( !(mpi_cmp_ui( k, 0 ) > 0) ) { /* check: k > 0 */
+	    if( DBG_CIPHER )
+		progress('-');
+	    continue; /* no */
+	}
+	break;	/* okay */
+    }
+    xfree(rndbuf);
+    if( DBG_CIPHER )
+	progress('\n');
+
+    return k;
+}
+
+
+static void
+test_keys( DSA_secret_key *sk, unsigned qbits )
+{
+    DSA_public_key pk;
+    MPI test = mpi_alloc( qbits / BITS_PER_MPI_LIMB );
+    MPI out1_a = mpi_alloc( qbits / BITS_PER_MPI_LIMB );
+    MPI out1_b = mpi_alloc( qbits / BITS_PER_MPI_LIMB );
+
+    pk.p = sk->p;
+    pk.q = sk->q;
+    pk.g = sk->g;
+    pk.y = sk->y;
+    /*mpi_set_bytes( test, qbits, get_random_byte, 0 );*/
+    {	char *p = get_random_bits( qbits, 0, 0 );
+	mpi_set_buffer( test, p, (qbits+7)/8, 0 );
+	xfree(p);
+    }
+
+    sign( out1_a, out1_b, test, sk );
+    if( !verify( out1_a, out1_b, test, &pk ) )
+	log_fatal("DSA:: sign, verify failed\n");
+
+    mpi_free( test );
+    mpi_free( out1_a );
+    mpi_free( out1_b );
+}
+
+
+
+/****************
+ * Generate a DSA key pair with a key of size NBITS
+ * Returns: 2 structures filled with all needed values
+ *	    and an array with the n-1 factors of (p-1)
+ */
+static void
+generate( DSA_secret_key *sk, unsigned nbits, unsigned qbits,
+	  MPI **ret_factors )
+{
+    MPI p;    /* the prime */
+    MPI q;    /* the prime factor */
+    MPI g;    /* the generator */
+    MPI y;    /* g^x mod p */
+    MPI x;    /* the secret exponent */
+    MPI h, e;  /* helper */
+    byte *rndbuf;
+
+    assert( nbits >= 512 );
+    assert( qbits >= 160 );
+    assert( qbits %8 == 0 );
+
+    p = generate_elg_prime( 1, nbits, qbits, NULL, ret_factors );
+    /* get q out of factors */
+    q = mpi_copy((*ret_factors)[0]);
+    if( mpi_get_nbits(q) != qbits )
+	BUG();
+
+    /* find a generator g (h and e are helpers)*/
+    /* e = (p-1)/q */
+    e = mpi_alloc( mpi_get_nlimbs(p) );
+    mpi_sub_ui( e, p, 1 );
+    mpi_fdiv_q( e, e, q );
+    g = mpi_alloc( mpi_get_nlimbs(p) );
+    h = mpi_alloc_set_ui( 1 ); /* we start with 2 */
+    do {
+	mpi_add_ui( h, h, 1 );
+	/* g = h^e mod p */
+	mpi_powm( g, h, e, p );
+    } while( !mpi_cmp_ui( g, 1 ) );  /* continue until g != 1 */
+
+    /* select a random number which has these properties:
+     *	 0 < x < q-1
+     * This must be a very good random number because this
+     * is the secret part. */
+    if( DBG_CIPHER )
+	log_debug("choosing a random x ");
+    x = mpi_alloc_secure( mpi_get_nlimbs(q) );
+    mpi_sub_ui( h, q, 1 );  /* put q-1 into h */
+    rndbuf = NULL;
+    do {
+	if( DBG_CIPHER )
+	    progress('.');
+	if( !rndbuf )
+	    rndbuf = get_random_bits( qbits, 2, 1 );
+	else { /* change only some of the higher bits (= 2 bytes)*/
+	    char *r = get_random_bits( 16, 2, 1 );
+	    memcpy(rndbuf, r, 16/8 );
+	    xfree(r);
+	}
+	mpi_set_buffer( x, rndbuf, (qbits+7)/8, 0 );
+	mpi_clear_highbit( x, qbits+1 );
+    } while( !( mpi_cmp_ui( x, 0 )>0 && mpi_cmp( x, h )<0 ) );
+    xfree(rndbuf);
+    mpi_free( e );
+    mpi_free( h );
+
+    /* y = g^x mod p */
+    y = mpi_alloc( mpi_get_nlimbs(p) );
+    mpi_powm( y, g, x, p );
+
+    if( DBG_CIPHER ) {
+	progress('\n');
+	log_mpidump("dsa  p= ", p );
+	log_mpidump("dsa  q= ", q );
+	log_mpidump("dsa  g= ", g );
+	log_mpidump("dsa  y= ", y );
+	log_mpidump("dsa  x= ", x );
+    }
+
+    /* copy the stuff to the key structures */
+    sk->p = p;
+    sk->q = q;
+    sk->g = g;
+    sk->y = y;
+    sk->x = x;
+
+    /* now we can test our keys (this should never fail!) */
+    test_keys( sk, qbits );
+}
+
+
+
+/****************
+ * Test whether the secret key is valid.
+ * Returns: if this is a valid key.
+ */
+static int
+check_secret_key( DSA_secret_key *sk )
+{
+    int rc;
+    MPI 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;
+}
+
+
+
+/****************
+ * Make a DSA signature from HASH and put it into r and s.
+ *
+ * Without generating the k this function runs in 
+ * about 26ms on a 300 Mhz Mobile Pentium
+ */
+
+static void
+sign(MPI r, MPI s, MPI hash, DSA_secret_key *skey )
+{
+    MPI k;
+    MPI kinv;
+    MPI tmp;
+
+    /* select a random k with 0 < k < q */
+    k = gen_k( skey->q );
+
+    /* r = (a^k mod p) mod q */
+    mpi_powm( r, skey->g, k, skey->p );
+    mpi_fdiv_r( r, r, skey->q );
+
+    /* kinv = k^(-1) mod q */
+    kinv = mpi_alloc( mpi_get_nlimbs(k) );
+    mpi_invm(kinv, k, skey->q );
+
+    /* s = (kinv * ( hash + x * r)) mod q */
+    tmp = mpi_alloc( mpi_get_nlimbs(skey->p) );
+    mpi_mul( tmp, skey->x, r );
+    mpi_add( tmp, tmp, hash );
+    mpi_mulm( s , kinv, tmp, skey->q );
+
+    mpi_free(k);
+    mpi_free(kinv);
+    mpi_free(tmp);
+}
+
+
+/****************
+ * Returns true if the signature composed from R and S is valid.
+ *
+ * Without the checks this function runs in 
+ * about 31ms on a 300 Mhz Mobile Pentium
+ */
+static int
+verify(MPI r, MPI s, MPI hash, DSA_public_key *pkey )
+{
+    int rc;
+    MPI w, u1, u2, v;
+    MPI base[3];
+    MPI exponent[3];
+
+
+    if( !(mpi_cmp_ui( r, 0 ) > 0 && mpi_cmp( r, pkey->q ) < 0) )
+	return 0; /* assertion	0 < r < q  failed */
+    if( !(mpi_cmp_ui( s, 0 ) > 0 && mpi_cmp( s, pkey->q ) < 0) )
+	return 0; /* assertion	0 < s < q  failed */
+
+    w  = mpi_alloc( mpi_get_nlimbs(pkey->q) );
+    u1 = mpi_alloc( mpi_get_nlimbs(pkey->q) );
+    u2 = mpi_alloc( mpi_get_nlimbs(pkey->q) );
+    v  = mpi_alloc( mpi_get_nlimbs(pkey->p) );
+
+    /* w = s^(-1) mod q */
+    mpi_invm( w, s, pkey->q );
+
+    /* u1 = (hash * w) mod q */
+    mpi_mulm( u1, hash, w, pkey->q );
+
+    /* u2 = r * w mod q  */
+    mpi_mulm( u2, r, w, pkey->q );
+
+    /* v =  g^u1 * y^u2 mod p mod q */
+    base[0] = pkey->g; exponent[0] = u1;
+    base[1] = pkey->y; exponent[1] = u2;
+    base[2] = NULL;    exponent[2] = NULL;
+    mpi_mulpowm( v, base, exponent, pkey->p );
+    mpi_fdiv_r( v, v, pkey->q );
+
+    rc = !mpi_cmp( v, r );
+
+    mpi_free(w);
+    mpi_free(u1);
+    mpi_free(u2);
+    mpi_free(v);
+    return rc;
+}
+
+
+/*********************************************
+ **************  interface  ******************
+ *********************************************/
+
+/* DSA2 has a variable-sized q, which adds an extra parameter to the
+   pubkey generation.  I'm doing this as a different function as it is
+   only called from one place and is thus cleaner than revamping the
+   pubkey_generate interface to carry an extra parameter which would
+   be meaningless for all algorithms other than DSA. */
+
+int
+dsa2_generate( int algo, unsigned nbits, unsigned qbits,
+	       MPI *skey, MPI **retfactors )
+{
+    DSA_secret_key sk;
+
+    if( algo != PUBKEY_ALGO_DSA )
+	return G10ERR_PUBKEY_ALGO;
+
+    generate( &sk, nbits, qbits, retfactors );
+    skey[0] = sk.p;
+    skey[1] = sk.q;
+    skey[2] = sk.g;
+    skey[3] = sk.y;
+    skey[4] = sk.x;
+    return 0;
+}
+
+
+int
+dsa_generate( int algo, unsigned nbits, MPI *skey, MPI **retfactors )
+{
+  return dsa2_generate(algo,nbits,160,skey,retfactors);
+}
+
+
+int
+dsa_check_secret_key( int algo, MPI *skey )
+{
+    DSA_secret_key sk;
+
+    if( algo != PUBKEY_ALGO_DSA )
+	return G10ERR_PUBKEY_ALGO;
+    if( !skey[0] || !skey[1] || !skey[2] || !skey[3] || !skey[4] )
+	return G10ERR_BAD_MPI;
+
+    sk.p = skey[0];
+    sk.q = skey[1];
+    sk.g = skey[2];
+    sk.y = skey[3];
+    sk.x = skey[4];
+    if( !check_secret_key( &sk ) )
+	return G10ERR_BAD_SECKEY;
+
+    return 0;
+}
+
+
+
+int
+dsa_sign( int algo, MPI *resarr, MPI data, MPI *skey )
+{
+    DSA_secret_key sk;
+
+    if( algo != PUBKEY_ALGO_DSA )
+	return G10ERR_PUBKEY_ALGO;
+    if( !data || !skey[0] || !skey[1] || !skey[2] || !skey[3] || !skey[4] )
+	return G10ERR_BAD_MPI;
+
+    sk.p = skey[0];
+    sk.q = skey[1];
+    sk.g = skey[2];
+    sk.y = skey[3];
+    sk.x = skey[4];
+    resarr[0] = mpi_alloc( mpi_get_nlimbs( sk.p ) );
+    resarr[1] = mpi_alloc( mpi_get_nlimbs( sk.p ) );
+    sign( resarr[0], resarr[1], data, &sk );
+    return 0;
+}
+
+int
+dsa_verify( int algo, MPI hash, MPI *data, MPI *pkey )
+{
+    DSA_public_key pk;
+
+    if( algo != PUBKEY_ALGO_DSA )
+	return G10ERR_PUBKEY_ALGO;
+    if( !data[0] || !data[1] || !hash
+	|| !pkey[0] || !pkey[1] || !pkey[2] || !pkey[3] )
+	return G10ERR_BAD_MPI;
+
+    pk.p = pkey[0];
+    pk.q = pkey[1];
+    pk.g = pkey[2];
+    pk.y = pkey[3];
+    if( !verify( data[0], data[1], hash, &pk ) )
+	return G10ERR_BAD_SIGN;
+    return 0;
+}
+
+
+
+unsigned
+dsa_get_nbits( int algo, MPI *pkey )
+{
+    if( algo != PUBKEY_ALGO_DSA )
+	return 0;
+    return mpi_get_nbits( pkey[0] );
+}
+
+
+/****************
+ * Return some information about the algorithm.  We need algo here to
+ * distinguish different flavors of the algorithm.
+ * Returns: A pointer to string describing the algorithm or NULL if
+ *	    the ALGO is invalid.
+ * Usage: Bit 0 set : allows signing
+ *	      1 set : allows encryption
+ */
+const char *
+dsa_get_info( int algo, int *npkey, int *nskey, int *nenc, int *nsig,
+							 int *use )
+{
+    *npkey = 4;
+    *nskey = 5;
+    *nenc = 0;
+    *nsig = 2;
+
+    switch( algo ) {
+      case PUBKEY_ALGO_DSA:   *use = PUBKEY_USAGE_SIG; return "DSA";
+      default: *use = 0; return NULL;
+    }
+}