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
33 void
_gcry_mpi_mul_ui(gcry_mpi_t prod,gcry_mpi_t mult,unsigned long small_mult)34 _gcry_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
63 void
_gcry_mpi_mul_2exp(gcry_mpi_t w,gcry_mpi_t u,unsigned long cnt)64 _gcry_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
109 void
_gcry_mpi_mul(gcry_mpi_t w,gcry_mpi_t u,gcry_mpi_t v)110 _gcry_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
207 void
_gcry_mpi_mulm(gcry_mpi_t w,gcry_mpi_t u,gcry_mpi_t v,gcry_mpi_t m)208 _gcry_mpi_mulm (gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v, gcry_mpi_t m)
209 {
210 mpi_mul (w, u, v);
211 _gcry_mpi_tdiv_r (w, w, m);
212 }
213