mpicoder.c 11.7 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
/* mpicoder.c  -  Coder for the external representation of MPIs
 * 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
 */

21
#include <linux/bitops.h>
22
#include <linux/count_zeros.h>
23
24
25
26
#include "mpi-internal.h"

#define MAX_EXTERN_MPI_BITS 16384

27
28
29
30
31
32
33
34
35
36
37
38
39
/**
 * mpi_read_raw_data - Read a raw byte stream as a positive integer
 * @xbuffer: The data to read
 * @nbytes: The amount of data to read
 */
MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
{
	const uint8_t *buffer = xbuffer;
	int i, j;
	unsigned nbits, nlimbs;
	mpi_limb_t a;
	MPI val = NULL;

40
	while (nbytes > 0 && buffer[0] == 0) {
41
42
43
44
45
46
47
48
49
50
51
52
53
54
		buffer++;
		nbytes--;
	}

	nbits = nbytes * 8;
	if (nbits > MAX_EXTERN_MPI_BITS) {
		pr_info("MPI: mpi too large (%u bits)\n", nbits);
		return NULL;
	}
	if (nbytes > 0)
		nbits -= count_leading_zeros(buffer[0]);
	else
		nbits = 0;

55
	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
	val = mpi_alloc(nlimbs);
	if (!val)
		return NULL;
	val->nbits = nbits;
	val->sign = 0;
	val->nlimbs = nlimbs;

	if (nbytes > 0) {
		i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
		i %= BYTES_PER_MPI_LIMB;
		for (j = nlimbs; j > 0; j--) {
			a = 0;
			for (; i < BYTES_PER_MPI_LIMB; i++) {
				a <<= 8;
				a |= *buffer++;
			}
			i = 0;
			val->d[j - 1] = a;
		}
	}
	return val;
}
EXPORT_SYMBOL_GPL(mpi_read_raw_data);

80
81
82
83
84
85
MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
{
	const uint8_t *buffer = xbuffer;
	int i, j;
	unsigned nbits, nbytes, nlimbs, nread = 0;
	mpi_limb_t a;
86
	MPI val = NULL;
87
88
89
90
91
92
93
94
95
96
97
98

	if (*ret_nread < 2)
		goto leave;
	nbits = buffer[0] << 8 | buffer[1];

	if (nbits > MAX_EXTERN_MPI_BITS) {
		pr_info("MPI: mpi too large (%u bits)\n", nbits);
		goto leave;
	}
	buffer += 2;
	nread = 2;

99
100
	nbytes = DIV_ROUND_UP(nbits, 8);
	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
101
102
	val = mpi_alloc(nlimbs);
	if (!val)
103
		return NULL;
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
	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	i %= BYTES_PER_MPI_LIMB;
	val->nbits = nbits;
	j = val->nlimbs = nlimbs;
	val->sign = 0;
	for (; j > 0; j--) {
		a = 0;
		for (; i < BYTES_PER_MPI_LIMB; i++) {
			if (++nread > *ret_nread) {
				printk
				    ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
				     nread, *ret_nread);
				goto leave;
			}
			a <<= 8;
			a |= *buffer++;
		}
		i = 0;
		val->d[j - 1] = a;
	}

leave:
	*ret_nread = nread;
	return val;
}
EXPORT_SYMBOL_GPL(mpi_read_from_buffer);

Michal Marek's avatar
Michal Marek committed
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
static int count_lzeros(MPI a)
{
	mpi_limb_t alimb;
	int i, lzeros = 0;

	for (i = a->nlimbs - 1; i >= 0; i--) {
		alimb = a->d[i];
		if (alimb == 0) {
			lzeros += sizeof(mpi_limb_t);
		} else {
			lzeros += count_leading_zeros(alimb) / 8;
			break;
		}
	}
	return lzeros;
}

148
149
150
151
152
153
154
/**
 * mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
 *
 * @a:		a multi precision integer
 * @buf:	bufer to which the output will be written to. Needs to be at
 *		leaset mpi_get_size(a) long.
 * @buf_len:	size of the buf.
155
156
157
 * @nbytes:	receives the actual length of the data written on success and
 *		the data to-be-written on -EOVERFLOW in case buf_len was too
 *		small.
158
159
160
 * @sign:	if not NULL, it will be set to the sign of a.
 *
 * Return:	0 on success or error code in case of error
161
 */
162
163
int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
		    int *sign)
164
{
165
	uint8_t *p;
166
	mpi_limb_t alimb;
167
	unsigned int n = mpi_get_size(a);
Michal Marek's avatar
Michal Marek committed
168
	int i, lzeros;
169

170
	if (!buf || !nbytes)
171
		return -EINVAL;
172
173
174

	if (sign)
		*sign = a->sign;
175

Michal Marek's avatar
Michal Marek committed
176
	lzeros = count_lzeros(a);
177

178
179
180
181
182
	if (buf_len < n - lzeros) {
		*nbytes = n - lzeros;
		return -EOVERFLOW;
	}

183
	p = buf;
Tadeusz Struk's avatar
Tadeusz Struk committed
184
	*nbytes = n - lzeros;
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204

	for (i = a->nlimbs - 1; i >= 0; i--) {
		alimb = a->d[i];
#if BYTES_PER_MPI_LIMB == 4
		*p++ = alimb >> 24;
		*p++ = alimb >> 16;
		*p++ = alimb >> 8;
		*p++ = alimb;
#elif BYTES_PER_MPI_LIMB == 8
		*p++ = alimb >> 56;
		*p++ = alimb >> 48;
		*p++ = alimb >> 40;
		*p++ = alimb >> 32;
		*p++ = alimb >> 24;
		*p++ = alimb >> 16;
		*p++ = alimb >> 8;
		*p++ = alimb;
#else
#error please implement for this limb size.
#endif
Tadeusz Struk's avatar
Tadeusz Struk committed
205
206
207
208
209
210
211
212
213
214
215
216
217

		if (lzeros > 0) {
			if (lzeros >= sizeof(alimb)) {
				p -= sizeof(alimb);
			} else {
				mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
				mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
							+ lzeros;
				*limb1 = *limb2;
				p -= lzeros;
			}
			lzeros -= sizeof(alimb);
		}
218
	}
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
	return 0;
}
EXPORT_SYMBOL_GPL(mpi_read_buffer);

/*
 * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
 * Caller must free the return string.
 * This function does return a 0 byte buffer with nbytes set to zero if the
 * value of A is zero.
 *
 * @a:		a multi precision integer.
 * @nbytes:	receives the length of this buffer.
 * @sign:	if not NULL, it will be set to the sign of the a.
 *
 * Return:	Pointer to MPI buffer or NULL on error
 */
void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
{
Tadeusz Struk's avatar
Tadeusz Struk committed
237
	uint8_t *buf;
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
	unsigned int n;
	int ret;

	if (!nbytes)
		return NULL;

	n = mpi_get_size(a);

	if (!n)
		n++;

	buf = kmalloc(n, GFP_KERNEL);

	if (!buf)
		return NULL;

	ret = mpi_read_buffer(a, buf, n, nbytes, sign);

	if (ret) {
		kfree(buf);
		return NULL;
	}
	return buf;
261
262
263
264
265
266
267
268
269
270
271
272
273
}
EXPORT_SYMBOL_GPL(mpi_get_buffer);

/****************
 * Use BUFFER to update MPI.
 */
int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
{
	const uint8_t *buffer = xbuffer, *p;
	mpi_limb_t alimb;
	int nlimbs;
	int i;

274
	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
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
331
332
333
334
335
336
337
338
	if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
		return -ENOMEM;
	a->sign = sign;

	for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
#if BYTES_PER_MPI_LIMB == 4
		alimb = (mpi_limb_t) *p--;
		alimb |= (mpi_limb_t) *p-- << 8;
		alimb |= (mpi_limb_t) *p-- << 16;
		alimb |= (mpi_limb_t) *p-- << 24;
#elif BYTES_PER_MPI_LIMB == 8
		alimb = (mpi_limb_t) *p--;
		alimb |= (mpi_limb_t) *p-- << 8;
		alimb |= (mpi_limb_t) *p-- << 16;
		alimb |= (mpi_limb_t) *p-- << 24;
		alimb |= (mpi_limb_t) *p-- << 32;
		alimb |= (mpi_limb_t) *p-- << 40;
		alimb |= (mpi_limb_t) *p-- << 48;
		alimb |= (mpi_limb_t) *p-- << 56;
#else
#error please implement for this limb size.
#endif
		a->d[i++] = alimb;
	}
	if (p >= buffer) {
#if BYTES_PER_MPI_LIMB == 4
		alimb = *p--;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 8;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 16;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 24;
#elif BYTES_PER_MPI_LIMB == 8
		alimb = (mpi_limb_t) *p--;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 8;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 16;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 24;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 32;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 40;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 48;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 56;
#else
#error please implement for this limb size.
#endif
		a->d[i++] = alimb;
	}
	a->nlimbs = i;

	if (i != nlimbs) {
		pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
		       nlimbs);
		BUG();
	}
	return 0;
}
EXPORT_SYMBOL_GPL(mpi_set_buffer);
Tadeusz Struk's avatar
Tadeusz Struk committed
339
340
341
342
343
344
345
346
347
348
349
350
351

/**
 * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first)
 *
 * This function works in the same way as the mpi_read_buffer, but it
 * takes an sgl instead of u8 * buf.
 *
 * @a:		a multi precision integer
 * @sgl:	scatterlist to write to. Needs to be at least
 *		mpi_get_size(a) long.
 * @nbytes:	in/out param - it has the be set to the maximum number of
 *		bytes that can be written to sgl. This has to be at least
 *		the size of the integer a. On return it receives the actual
352
353
 *		length of the data written on success or the data that would
 *		be written if buffer was too small.
Tadeusz Struk's avatar
Tadeusz Struk committed
354
355
356
357
358
359
360
361
362
363
 * @sign:	if not NULL, it will be set to the sign of a.
 *
 * Return:	0 on success or error code in case of error
 */
int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
		     int *sign)
{
	u8 *p, *p2;
	mpi_limb_t alimb, alimb2;
	unsigned int n = mpi_get_size(a);
Michal Marek's avatar
Michal Marek committed
364
	int i, x, y = 0, lzeros, buf_len;
Tadeusz Struk's avatar
Tadeusz Struk committed
365

366
	if (!nbytes)
Tadeusz Struk's avatar
Tadeusz Struk committed
367
368
369
370
371
		return -EINVAL;

	if (sign)
		*sign = a->sign;

Michal Marek's avatar
Michal Marek committed
372
	lzeros = count_lzeros(a);
Tadeusz Struk's avatar
Tadeusz Struk committed
373

374
375
376
377
378
	if (*nbytes < n - lzeros) {
		*nbytes = n - lzeros;
		return -EOVERFLOW;
	}

Tadeusz Struk's avatar
Tadeusz Struk committed
379
380
381
382
	*nbytes = n - lzeros;
	buf_len = sgl->length;
	p2 = sg_virt(sgl);

383
384
385
	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
			lzeros %= BYTES_PER_MPI_LIMB;
		i >= 0; i--) {
Tadeusz Struk's avatar
Tadeusz Struk committed
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
		alimb = a->d[i];
		p = (u8 *)&alimb2;
#if BYTES_PER_MPI_LIMB == 4
		*p++ = alimb >> 24;
		*p++ = alimb >> 16;
		*p++ = alimb >> 8;
		*p++ = alimb;
#elif BYTES_PER_MPI_LIMB == 8
		*p++ = alimb >> 56;
		*p++ = alimb >> 48;
		*p++ = alimb >> 40;
		*p++ = alimb >> 32;
		*p++ = alimb >> 24;
		*p++ = alimb >> 16;
		*p++ = alimb >> 8;
		*p++ = alimb;
#else
#error please implement for this limb size.
#endif
		if (lzeros > 0) {
406
407
408
409
410
411
			mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
			mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
				+ lzeros;
			*limb1 = *limb2;
			p -= lzeros;
			y = lzeros;
Tadeusz Struk's avatar
Tadeusz Struk committed
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
			lzeros -= sizeof(alimb);
		}

		p = p - (sizeof(alimb) - y);

		for (x = 0; x < sizeof(alimb) - y; x++) {
			if (!buf_len) {
				sgl = sg_next(sgl);
				if (!sgl)
					return -EINVAL;
				buf_len = sgl->length;
				p2 = sg_virt(sgl);
			}
			*p2++ = *p++;
			buf_len--;
		}
		y = 0;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(mpi_write_to_sgl);

/*
 * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with
 *			     data from the sgl
 *
 * This function works in the same way as the mpi_read_raw_data, but it
 * takes an sgl instead of void * buffer. i.e. it allocates
 * a new MPI and reads the content of the sgl to the MPI.
 *
 * @sgl:	scatterlist to read from
 * @len:	number of bytes to read
 *
 * Return:	Pointer to a new MPI or NULL on error
 */
MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int len)
{
	struct scatterlist *sg;
	int x, i, j, z, lzeros, ents;
	unsigned int nbits, nlimbs, nbytes;
	mpi_limb_t a;
	MPI val = NULL;

	lzeros = 0;
	ents = sg_nents(sgl);

	for_each_sg(sgl, sg, ents, i) {
		const u8 *buff = sg_virt(sg);
		int len = sg->length;

462
		while (len && !*buff) {
Tadeusz Struk's avatar
Tadeusz Struk committed
463
			lzeros++;
464
465
466
			len--;
			buff++;
		}
Tadeusz Struk's avatar
Tadeusz Struk committed
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533

		if (len && *buff)
			break;

		ents--;
		lzeros = 0;
	}

	sgl = sg;

	if (!ents)
		nbytes = 0;
	else
		nbytes = len - lzeros;

	nbits = nbytes * 8;
	if (nbits > MAX_EXTERN_MPI_BITS) {
		pr_info("MPI: mpi too large (%u bits)\n", nbits);
		return NULL;
	}

	if (nbytes > 0)
		nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros));
	else
		nbits = 0;

	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
	val = mpi_alloc(nlimbs);
	if (!val)
		return NULL;

	val->nbits = nbits;
	val->sign = 0;
	val->nlimbs = nlimbs;

	if (nbytes == 0)
		return val;

	j = nlimbs - 1;
	a = 0;
	z = 0;
	x = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	x %= BYTES_PER_MPI_LIMB;

	for_each_sg(sgl, sg, ents, i) {
		const u8 *buffer = sg_virt(sg) + lzeros;
		int len = sg->length - lzeros;
		int buf_shift = x;

		if  (sg_is_last(sg) && (len % BYTES_PER_MPI_LIMB))
			len += BYTES_PER_MPI_LIMB - (len % BYTES_PER_MPI_LIMB);

		for (; x < len + buf_shift; x++) {
			a <<= 8;
			a |= *buffer++;
			if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
				val->d[j--] = a;
				a = 0;
			}
		}
		z += x;
		x = 0;
		lzeros = 0;
	}
	return val;
}
EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);