1/* mpi-mul.c  -  MPI functions
2 * Copyright (C) 1994, 1996, 1998, 2001, 2002, 2003 Free Software Foundation, Inc.
3 *
4 * This file is part of Libgcrypt.
5 *
6 * Libgcrypt is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU Lesser General Public License as
8 * published by the Free Software Foundation; either version 2.1 of
9 * the License, or (at your option) any later version.
10 *
11 * Libgcrypt is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
19 *
20 * Note: This code is heavily based on the GNU MP Library.
21 *	 Actually it's the same code with only minor changes in the
22 *	 way the data is stored; this is to support the abstraction
23 *	 of an optional secure memory allocation which may be used
24 *	 to avoid revealing of sensitive data due to paging etc.
25 */
26
27#include <config.h>
28#include <stdio.h>
29#include <stdlib.h>
30#include "mpi-internal.h"
31
32
33void
34gcry_mpi_mul_ui( gcry_mpi_t prod, gcry_mpi_t mult, unsigned long small_mult )
35{
36    mpi_size_t size, prod_size;
37    mpi_ptr_t  prod_ptr;
38    mpi_limb_t cy;
39    int sign;
40
41    size = mult->nlimbs;
42    sign = mult->sign;
43
44    if( !size || !small_mult ) {
45	prod->nlimbs = 0;
46	prod->sign = 0;
47	return;
48    }
49
50    prod_size = size + 1;
51    if( prod->alloced < prod_size )
52	mpi_resize( prod, prod_size );
53    prod_ptr = prod->d;
54
55    cy = _gcry_mpih_mul_1( prod_ptr, mult->d, size, (mpi_limb_t)small_mult );
56    if( cy )
57	prod_ptr[size++] = cy;
58    prod->nlimbs = size;
59    prod->sign = sign;
60}
61
62
63void
64gcry_mpi_mul_2exp( gcry_mpi_t w, gcry_mpi_t u, unsigned long cnt)
65{
66    mpi_size_t usize, wsize, limb_cnt;
67    mpi_ptr_t wp;
68    mpi_limb_t wlimb;
69    int usign, wsign;
70
71    usize = u->nlimbs;
72    usign = u->sign;
73
74    if( !usize ) {
75	w->nlimbs = 0;
76	w->sign = 0;
77	return;
78    }
79
80    limb_cnt = cnt / BITS_PER_MPI_LIMB;
81    wsize = usize + limb_cnt + 1;
82    if( w->alloced < wsize )
83	mpi_resize(w, wsize );
84    wp = w->d;
85    wsize = usize + limb_cnt;
86    wsign = usign;
87
88    cnt %= BITS_PER_MPI_LIMB;
89    if( cnt ) {
90	wlimb = _gcry_mpih_lshift( wp + limb_cnt, u->d, usize, cnt );
91	if( wlimb ) {
92	    wp[wsize] = wlimb;
93	    wsize++;
94	}
95    }
96    else {
97	MPN_COPY_DECR( wp + limb_cnt, u->d, usize );
98    }
99
100    /* Zero all whole limbs at low end.  Do it here and not before calling
101     * mpn_lshift, not to lose for U == W.  */
102    MPN_ZERO( wp, limb_cnt );
103
104    w->nlimbs = wsize;
105    w->sign = wsign;
106}
107
108
109void
110gcry_mpi_mul( gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v)
111{
112    mpi_size_t usize, vsize, wsize;
113    mpi_ptr_t up, vp, wp;
114    mpi_limb_t cy;
115    int usign, vsign, usecure, vsecure, sign_product;
116    int assign_wp=0;
117    mpi_ptr_t tmp_limb=NULL;
118    unsigned int tmp_limb_nlimbs = 0;
119
120    if( u->nlimbs < v->nlimbs ) { /* Swap U and V. */
121	usize = v->nlimbs;
122	usign = v->sign;
123	usecure = mpi_is_secure(v);
124	up    = v->d;
125	vsize = u->nlimbs;
126	vsign = u->sign;
127	vsecure = mpi_is_secure(u);
128	vp    = u->d;
129    }
130    else {
131	usize = u->nlimbs;
132	usign = u->sign;
133	usecure = mpi_is_secure(u);
134	up    = u->d;
135	vsize = v->nlimbs;
136	vsign = v->sign;
137	vsecure = mpi_is_secure(v);
138	vp    = v->d;
139    }
140    sign_product = usign ^ vsign;
141    wp = w->d;
142
143    /* Ensure W has space enough to store the result.  */
144    wsize = usize + vsize;
145    if ( !mpi_is_secure (w) && (mpi_is_secure (u) || mpi_is_secure (v)) ) {
146        /* w is not allocated in secure space but u or v is.  To make sure
147         * that no temporray results are stored in w, we temporary use
148         * a newly allocated limb space for w */
149        wp = mpi_alloc_limb_space( wsize, 1 );
150        assign_wp = 2; /* mark it as 2 so that we can later copy it back to
151                        * mormal memory */
152    }
153    else if( w->alloced < wsize ) {
154	if( wp == up || wp == vp ) {
155	    wp = mpi_alloc_limb_space( wsize, mpi_is_secure(w) );
156	    assign_wp = 1;
157	}
158	else {
159	    mpi_resize(w, wsize );
160	    wp = w->d;
161	}
162    }
163    else { /* Make U and V not overlap with W.	*/
164	if( wp == up ) {
165	    /* W and U are identical.  Allocate temporary space for U.	*/
166            tmp_limb_nlimbs = usize;
167	    up = tmp_limb = mpi_alloc_limb_space( usize, usecure  );
168	    /* Is V identical too?  Keep it identical with U.  */
169	    if( wp == vp )
170		vp = up;
171	    /* Copy to the temporary space.  */
172	    MPN_COPY( up, wp, usize );
173	}
174	else if( wp == vp ) {
175	    /* W and V are identical.  Allocate temporary space for V.	*/
176            tmp_limb_nlimbs = vsize;
177	    vp = tmp_limb = mpi_alloc_limb_space( vsize, vsecure );
178	    /* Copy to the temporary space.  */
179	    MPN_COPY( vp, wp, vsize );
180	}
181    }
182
183    if( !vsize )
184	wsize = 0;
185    else {
186	cy = _gcry_mpih_mul( wp, up, usize, vp, vsize );
187	wsize -= cy? 0:1;
188    }
189
190    if( assign_wp ) {
191        if (assign_wp == 2) {
192            /* copy the temp wp from secure memory back to normal memory */
193	    mpi_ptr_t tmp_wp = mpi_alloc_limb_space (wsize, 0);
194	    MPN_COPY (tmp_wp, wp, wsize);
195            _gcry_mpi_free_limb_space (wp, 0);
196            wp = tmp_wp;
197        }
198	_gcry_mpi_assign_limb_space( w, wp, wsize );
199    }
200    w->nlimbs = wsize;
201    w->sign = sign_product;
202    if( tmp_limb )
203	_gcry_mpi_free_limb_space (tmp_limb, tmp_limb_nlimbs);
204}
205
206
207void
208gcry_mpi_mulm( gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v, gcry_mpi_t m)
209{
210    gcry_mpi_mul(w, u, v);
211    _gcry_mpi_fdiv_r( w, w, m );
212}
213