aboutsummaryrefslogtreecommitdiff
path: root/lib/mpi/mpiutil.c
blob: bc81419f400c5576e50b0afca66a9188b3b52d68 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
/* mpiutil.ac  -  Utility functions for MPI
 * Copyright (C) 1998, 1999 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include "mpi-internal.h"

/* Constants allocated right away at startup.  */
static MPI constants[MPI_NUMBER_OF_CONSTANTS];

/* Initialize the MPI subsystem.  This is called early and allows to
 * do some initialization without taking care of threading issues.
 */
static int __init mpi_init(void)
{
	int idx;
	unsigned long value;

	for (idx = 0; idx < MPI_NUMBER_OF_CONSTANTS; idx++) {
		switch (idx) {
		case MPI_C_ZERO:
			value = 0;
			break;
		case MPI_C_ONE:
			value = 1;
			break;
		case MPI_C_TWO:
			value = 2;
			break;
		case MPI_C_THREE:
			value = 3;
			break;
		case MPI_C_FOUR:
			value = 4;
			break;
		case MPI_C_EIGHT:
			value = 8;
			break;
		default:
			pr_err("MPI: invalid mpi_const selector %d\n", idx);
			return -EFAULT;
		}
		constants[idx] = mpi_alloc_set_ui(value);
		constants[idx]->flags = (16|32);
	}

	return 0;
}
postcore_initcall(mpi_init);

/* Return a constant MPI descripbed by NO which is one of the
 * MPI_C_xxx macros.  There is no need to copy this returned value; it
 * may be used directly.
 */
MPI mpi_const(enum gcry_mpi_constants no)
{
	if ((int)no < 0 || no > MPI_NUMBER_OF_CONSTANTS)
		pr_err("MPI: invalid mpi_const selector %d\n", no);
	if (!constants[no])
		pr_err("MPI: MPI subsystem not initialized\n");
	return constants[no];
}
EXPORT_SYMBOL_GPL(mpi_const);

/****************
 * Note:  It was a bad idea to use the number of limbs to allocate
 *	  because on a alpha the limbs are large but we normally need
 *	  integers of n bits - So we should change this to bits (or bytes).
 *
 *	  But mpi_alloc is used in a lot of places :-)
 */
MPI mpi_alloc(unsigned nlimbs)
{
	MPI a;

	a = kmalloc(sizeof *a, GFP_KERNEL);
	if (!a)
		return a;

	if (nlimbs) {
		a->d = mpi_alloc_limb_space(nlimbs);
		if (!a->d) {
			kfree(a);
			return NULL;
		}
	} else {
		a->d = NULL;
	}

	a->alloced = nlimbs;
	a->nlimbs = 0;
	a->sign = 0;
	a->flags = 0;
	a->nbits = 0;
	return a;
}
EXPORT_SYMBOL_GPL(mpi_alloc);

mpi_ptr_t mpi_alloc_limb_space(unsigned nlimbs)
{
	size_t len = nlimbs * sizeof(mpi_limb_t);

	if (!len)
		return NULL;

	return kmalloc(len, GFP_KERNEL);
}

void mpi_free_limb_space(mpi_ptr_t a)
{
	if (!a)
		return;

	kfree_sensitive(a);
}

void mpi_assign_limb_space(MPI a, mpi_ptr_t ap, unsigned nlimbs)
{
	mpi_free_limb_space(a->d);
	a->d = ap;
	a->alloced = nlimbs;
}

/****************
 * Resize the array of A to NLIMBS. the additional space is cleared
 * (set to 0) [done by m_realloc()]
 */
int mpi_resize(MPI a, unsigned nlimbs)
{
	void *p;

	if (nlimbs <= a->alloced)
		return 0;	/* no need to do it */

	if (a->d) {
		p = kcalloc(nlimbs, sizeof(mpi_limb_t), GFP_KERNEL);
		if (!p)
			return -ENOMEM;
		memcpy(p, a->d, a->alloced * sizeof(mpi_limb_t));
		kfree_sensitive(a->d);
		a->d = p;
	} else {
		a->d = kcalloc(nlimbs, sizeof(mpi_limb_t), GFP_KERNEL);
		if (!a->d)
			return -ENOMEM;
	}
	a->alloced = nlimbs;
	return 0;
}

void mpi_clear(MPI a)
{
	if (!a)
		return;
	a->nlimbs = 0;
	a->flags = 0;
}
EXPORT_SYMBOL_GPL(mpi_clear);

void mpi_free(MPI a)
{
	if (!a)
		return;

	if (a->flags & 4)
		kfree_sensitive(a->d);
	else
		mpi_free_limb_space(a->d);

	if (a->flags & ~7)
		pr_info("invalid flag value in mpi\n");
	kfree(a);
}
EXPORT_SYMBOL_GPL(mpi_free);

/****************
 * Note: This copy function should not interpret the MPI
 *	 but copy it transparently.
 */
MPI mpi_copy(MPI a)
{
	int i;
	MPI b;

	if (a) {
		b = mpi_alloc(a->nlimbs);
		b->nlimbs = a->nlimbs;
		b->sign = a->sign;
		b->flags = a->flags;
		b->flags &= ~(16|32); /* Reset the immutable and constant flags. */
		for (i = 0; i < b->nlimbs; i++)
			b->d[i] = a->d[i];
	} else
		b = NULL;
	return b;
}

/****************
 * This function allocates an MPI which is optimized to hold
 * a value as large as the one given in the argument and allocates it
 * with the same flags as A.
 */
MPI mpi_alloc_like(MPI a)
{
	MPI b;

	if (a) {
		b = mpi_alloc(a->nlimbs);
		b->nlimbs = 0;
		b->sign = 0;
		b->flags = a->flags;
	} else
		b = NULL;

	return b;
}


/* Set U into W and release U.  If W is NULL only U will be released. */
void mpi_snatch(MPI w, MPI u)
{
	if (w) {
		mpi_assign_limb_space(w, u->d, u->alloced);
		w->nlimbs = u->nlimbs;
		w->sign   = u->sign;
		w->flags  = u->flags;
		u->alloced = 0;
		u->nlimbs = 0;
		u->d = NULL;
	}
	mpi_free(u);
}


MPI mpi_set(MPI w, MPI u)
{
	mpi_ptr_t wp, up;
	mpi_size_t usize = u->nlimbs;
	int usign = u->sign;

	if (!w)
		w = mpi_alloc(mpi_get_nlimbs(u));
	RESIZE_IF_NEEDED(w, usize);
	wp = w->d;
	up = u->d;
	MPN_COPY(wp, up, usize);
	w->nlimbs = usize;
	w->flags = u->flags;
	w->flags &= ~(16|32); /* Reset the immutable and constant flags.  */
	w->sign = usign;
	return w;
}
EXPORT_SYMBOL_GPL(mpi_set);

MPI mpi_set_ui(MPI w, unsigned long u)
{
	if (!w)
		w = mpi_alloc(1);
	/* FIXME: If U is 0 we have no need to resize and thus possible
	 * allocating the the limbs.
	 */
	RESIZE_IF_NEEDED(w, 1);
	w->d[0] = u;
	w->nlimbs = u ? 1 : 0;
	w->sign = 0;
	w->flags = 0;
	return w;
}
EXPORT_SYMBOL_GPL(mpi_set_ui);

MPI mpi_alloc_set_ui(unsigned long u)
{
	MPI w = mpi_alloc(1);
	w->d[0] = u;
	w->nlimbs = u ? 1 : 0;
	w->sign = 0;
	return w;
}

/****************
 * Swap the value of A and B, when SWAP is 1.
 * Leave the value when SWAP is 0.
 * This implementation should be constant-time regardless of SWAP.
 */
void mpi_swap_cond(MPI a, MPI b, unsigned long swap)
{
	mpi_size_t i;
	mpi_size_t nlimbs;
	mpi_limb_t mask = ((mpi_limb_t)0) - swap;
	mpi_limb_t x;

	if (a->alloced > b->alloced)
		nlimbs = b->alloced;
	else
		nlimbs = a->alloced;
	if (a->nlimbs > nlimbs || b->nlimbs > nlimbs)
		return;

	for (i = 0; i < nlimbs; i++) {
		x = mask & (a->d[i] ^ b->d[i]);
		a->d[i] = a->d[i] ^ x;
		b->d[i] = b->d[i] ^ x;
	}

	x = mask & (a->nlimbs ^ b->nlimbs);
	a->nlimbs = a->nlimbs ^ x;
	b->nlimbs = b->nlimbs ^ x;

	x = mask & (a->sign ^ b->sign);
	a->sign = a->sign ^ x;
	b->sign = b->sign ^ x;
}

MODULE_DESCRIPTION("Multiprecision maths library");
MODULE_LICENSE("GPL");