projects/linux·blob v4.4 · refs

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1/* mpicoder.c - Coder for the external representation of MPIs
2 * Copyright (C) 1998, 1999 Free Software Foundation, Inc.
3 *
4 * This file is part of GnuPG.
5 *
6 * GnuPG is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * GnuPG 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 General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * 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
21#include <linux/bitops.h>
22#include <linux/count_zeros.h>
23#include "mpi-internal.h"
24
25#define MAX_EXTERN_MPI_BITS 16384
26
27/**
28 * mpi_read_raw_data - Read a raw byte stream as a positive integer
29 * @xbuffer: The data to read
30 * @nbytes: The amount of data to read
31 */
32MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
33{
34 const uint8_t *buffer = xbuffer;
35 int i, j;
36 unsigned nbits, nlimbs;
37 mpi_limb_t a;
38 MPI val = NULL;
39
40 while (nbytes > 0 && buffer[0] == 0) {
41 buffer++;
42 nbytes--;
43 }
44
45 nbits = nbytes * 8;
46 if (nbits > MAX_EXTERN_MPI_BITS) {
47 pr_info("MPI: mpi too large (%u bits)\n", nbits);
48 return NULL;
49 }
50 if (nbytes > 0)
51 nbits -= count_leading_zeros(buffer[0]);
52 else
53 nbits = 0;
54
55 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
56 val = mpi_alloc(nlimbs);
57 if (!val)
58 return NULL;
59 val->nbits = nbits;
60 val->sign = 0;
61 val->nlimbs = nlimbs;
62
63 if (nbytes > 0) {
64 i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
65 i %= BYTES_PER_MPI_LIMB;
66 for (j = nlimbs; j > 0; j--) {
67 a = 0;
68 for (; i < BYTES_PER_MPI_LIMB; i++) {
69 a <<= 8;
70 a |= *buffer++;
71 }
72 i = 0;
73 val->d[j - 1] = a;
74 }
75 }
76 return val;
77}
78EXPORT_SYMBOL_GPL(mpi_read_raw_data);
79
80MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
81{
82 const uint8_t *buffer = xbuffer;
83 int i, j;
84 unsigned nbits, nbytes, nlimbs, nread = 0;
85 mpi_limb_t a;
86 MPI val = NULL;
87
88 if (*ret_nread < 2)
89 goto leave;
90 nbits = buffer[0] << 8 | buffer[1];
91
92 if (nbits > MAX_EXTERN_MPI_BITS) {
93 pr_info("MPI: mpi too large (%u bits)\n", nbits);
94 goto leave;
95 }
96 buffer += 2;
97 nread = 2;
98
99 nbytes = DIV_ROUND_UP(nbits, 8);
100 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
101 val = mpi_alloc(nlimbs);
102 if (!val)
103 return NULL;
104 i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
105 i %= BYTES_PER_MPI_LIMB;
106 val->nbits = nbits;
107 j = val->nlimbs = nlimbs;
108 val->sign = 0;
109 for (; j > 0; j--) {
110 a = 0;
111 for (; i < BYTES_PER_MPI_LIMB; i++) {
112 if (++nread > *ret_nread) {
113 printk
114 ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
115 nread, *ret_nread);
116 goto leave;
117 }
118 a <<= 8;
119 a |= *buffer++;
120 }
121 i = 0;
122 val->d[j - 1] = a;
123 }
124
125leave:
126 *ret_nread = nread;
127 return val;
128}
129EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
130
131/**
132 * mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
133 *
134 * @a: a multi precision integer
135 * @buf: bufer to which the output will be written to. Needs to be at
136 * leaset mpi_get_size(a) long.
137 * @buf_len: size of the buf.
138 * @nbytes: receives the actual length of the data written.
139 * @sign: if not NULL, it will be set to the sign of a.
140 *
141 * Return: 0 on success or error code in case of error
142 */
143int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
144 int *sign)
145{
146 uint8_t *p;
147 mpi_limb_t alimb;
148 unsigned int n = mpi_get_size(a);
149 int i, lzeros = 0;
150
151 if (buf_len < n || !buf || !nbytes)
152 return -EINVAL;
153
154 if (sign)
155 *sign = a->sign;
156
157 p = (void *)&a->d[a->nlimbs] - 1;
158
159 for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {
160 if (!*p)
161 lzeros++;
162 else
163 break;
164 }
165
166 p = buf;
167 *nbytes = n - lzeros;
168
169 for (i = a->nlimbs - 1; i >= 0; i--) {
170 alimb = a->d[i];
171#if BYTES_PER_MPI_LIMB == 4
172 *p++ = alimb >> 24;
173 *p++ = alimb >> 16;
174 *p++ = alimb >> 8;
175 *p++ = alimb;
176#elif BYTES_PER_MPI_LIMB == 8
177 *p++ = alimb >> 56;
178 *p++ = alimb >> 48;
179 *p++ = alimb >> 40;
180 *p++ = alimb >> 32;
181 *p++ = alimb >> 24;
182 *p++ = alimb >> 16;
183 *p++ = alimb >> 8;
184 *p++ = alimb;
185#else
186#error please implement for this limb size.
187#endif
188
189 if (lzeros > 0) {
190 if (lzeros >= sizeof(alimb)) {
191 p -= sizeof(alimb);
192 } else {
193 mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
194 mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
195 + lzeros;
196 *limb1 = *limb2;
197 p -= lzeros;
198 }
199 lzeros -= sizeof(alimb);
200 }
201 }
202 return 0;
203}
204EXPORT_SYMBOL_GPL(mpi_read_buffer);
205
206/*
207 * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
208 * Caller must free the return string.
209 * This function does return a 0 byte buffer with nbytes set to zero if the
210 * value of A is zero.
211 *
212 * @a: a multi precision integer.
213 * @nbytes: receives the length of this buffer.
214 * @sign: if not NULL, it will be set to the sign of the a.
215 *
216 * Return: Pointer to MPI buffer or NULL on error
217 */
218void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
219{
220 uint8_t *buf;
221 unsigned int n;
222 int ret;
223
224 if (!nbytes)
225 return NULL;
226
227 n = mpi_get_size(a);
228
229 if (!n)
230 n++;
231
232 buf = kmalloc(n, GFP_KERNEL);
233
234 if (!buf)
235 return NULL;
236
237 ret = mpi_read_buffer(a, buf, n, nbytes, sign);
238
239 if (ret) {
240 kfree(buf);
241 return NULL;
242 }
243 return buf;
244}
245EXPORT_SYMBOL_GPL(mpi_get_buffer);
246
247/****************
248 * Use BUFFER to update MPI.
249 */
250int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
251{
252 const uint8_t *buffer = xbuffer, *p;
253 mpi_limb_t alimb;
254 int nlimbs;
255 int i;
256
257 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
258 if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
259 return -ENOMEM;
260 a->sign = sign;
261
262 for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
263#if BYTES_PER_MPI_LIMB == 4
264 alimb = (mpi_limb_t) *p--;
265 alimb |= (mpi_limb_t) *p-- << 8;
266 alimb |= (mpi_limb_t) *p-- << 16;
267 alimb |= (mpi_limb_t) *p-- << 24;
268#elif BYTES_PER_MPI_LIMB == 8
269 alimb = (mpi_limb_t) *p--;
270 alimb |= (mpi_limb_t) *p-- << 8;
271 alimb |= (mpi_limb_t) *p-- << 16;
272 alimb |= (mpi_limb_t) *p-- << 24;
273 alimb |= (mpi_limb_t) *p-- << 32;
274 alimb |= (mpi_limb_t) *p-- << 40;
275 alimb |= (mpi_limb_t) *p-- << 48;
276 alimb |= (mpi_limb_t) *p-- << 56;
277#else
278#error please implement for this limb size.
279#endif
280 a->d[i++] = alimb;
281 }
282 if (p >= buffer) {
283#if BYTES_PER_MPI_LIMB == 4
284 alimb = *p--;
285 if (p >= buffer)
286 alimb |= (mpi_limb_t) *p-- << 8;
287 if (p >= buffer)
288 alimb |= (mpi_limb_t) *p-- << 16;
289 if (p >= buffer)
290 alimb |= (mpi_limb_t) *p-- << 24;
291#elif BYTES_PER_MPI_LIMB == 8
292 alimb = (mpi_limb_t) *p--;
293 if (p >= buffer)
294 alimb |= (mpi_limb_t) *p-- << 8;
295 if (p >= buffer)
296 alimb |= (mpi_limb_t) *p-- << 16;
297 if (p >= buffer)
298 alimb |= (mpi_limb_t) *p-- << 24;
299 if (p >= buffer)
300 alimb |= (mpi_limb_t) *p-- << 32;
301 if (p >= buffer)
302 alimb |= (mpi_limb_t) *p-- << 40;
303 if (p >= buffer)
304 alimb |= (mpi_limb_t) *p-- << 48;
305 if (p >= buffer)
306 alimb |= (mpi_limb_t) *p-- << 56;
307#else
308#error please implement for this limb size.
309#endif
310 a->d[i++] = alimb;
311 }
312 a->nlimbs = i;
313
314 if (i != nlimbs) {
315 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
316 nlimbs);
317 BUG();
318 }
319 return 0;
320}
321EXPORT_SYMBOL_GPL(mpi_set_buffer);
322
323/**
324 * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first)
325 *
326 * This function works in the same way as the mpi_read_buffer, but it
327 * takes an sgl instead of u8 * buf.
328 *
329 * @a: a multi precision integer
330 * @sgl: scatterlist to write to. Needs to be at least
331 * mpi_get_size(a) long.
332 * @nbytes: in/out param - it has the be set to the maximum number of
333 * bytes that can be written to sgl. This has to be at least
334 * the size of the integer a. On return it receives the actual
335 * length of the data written.
336 * @sign: if not NULL, it will be set to the sign of a.
337 *
338 * Return: 0 on success or error code in case of error
339 */
340int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
341 int *sign)
342{
343 u8 *p, *p2;
344 mpi_limb_t alimb, alimb2;
345 unsigned int n = mpi_get_size(a);
346 int i, x, y = 0, lzeros = 0, buf_len;
347
348 if (!nbytes || *nbytes < n)
349 return -EINVAL;
350
351 if (sign)
352 *sign = a->sign;
353
354 p = (void *)&a->d[a->nlimbs] - 1;
355
356 for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {
357 if (!*p)
358 lzeros++;
359 else
360 break;
361 }
362
363 *nbytes = n - lzeros;
364 buf_len = sgl->length;
365 p2 = sg_virt(sgl);
366
367 for (i = a->nlimbs - 1; i >= 0; i--) {
368 alimb = a->d[i];
369 p = (u8 *)&alimb2;
370#if BYTES_PER_MPI_LIMB == 4
371 *p++ = alimb >> 24;
372 *p++ = alimb >> 16;
373 *p++ = alimb >> 8;
374 *p++ = alimb;
375#elif BYTES_PER_MPI_LIMB == 8
376 *p++ = alimb >> 56;
377 *p++ = alimb >> 48;
378 *p++ = alimb >> 40;
379 *p++ = alimb >> 32;
380 *p++ = alimb >> 24;
381 *p++ = alimb >> 16;
382 *p++ = alimb >> 8;
383 *p++ = alimb;
384#else
385#error please implement for this limb size.
386#endif
387 if (lzeros > 0) {
388 if (lzeros >= sizeof(alimb)) {
389 p -= sizeof(alimb);
390 continue;
391 } else {
392 mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
393 mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
394 + lzeros;
395 *limb1 = *limb2;
396 p -= lzeros;
397 y = lzeros;
398 }
399 lzeros -= sizeof(alimb);
400 }
401
402 p = p - (sizeof(alimb) - y);
403
404 for (x = 0; x < sizeof(alimb) - y; x++) {
405 if (!buf_len) {
406 sgl = sg_next(sgl);
407 if (!sgl)
408 return -EINVAL;
409 buf_len = sgl->length;
410 p2 = sg_virt(sgl);
411 }
412 *p2++ = *p++;
413 buf_len--;
414 }
415 y = 0;
416 }
417 return 0;
418}
419EXPORT_SYMBOL_GPL(mpi_write_to_sgl);
420
421/*
422 * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with
423 * data from the sgl
424 *
425 * This function works in the same way as the mpi_read_raw_data, but it
426 * takes an sgl instead of void * buffer. i.e. it allocates
427 * a new MPI and reads the content of the sgl to the MPI.
428 *
429 * @sgl: scatterlist to read from
430 * @len: number of bytes to read
431 *
432 * Return: Pointer to a new MPI or NULL on error
433 */
434MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int len)
435{
436 struct scatterlist *sg;
437 int x, i, j, z, lzeros, ents;
438 unsigned int nbits, nlimbs, nbytes;
439 mpi_limb_t a;
440 MPI val = NULL;
441
442 lzeros = 0;
443 ents = sg_nents(sgl);
444
445 for_each_sg(sgl, sg, ents, i) {
446 const u8 *buff = sg_virt(sg);
447 int len = sg->length;
448
449 while (len && !*buff) {
450 lzeros++;
451 len--;
452 buff++;
453 }
454
455 if (len && *buff)
456 break;
457
458 ents--;
459 lzeros = 0;
460 }
461
462 sgl = sg;
463
464 if (!ents)
465 nbytes = 0;
466 else
467 nbytes = len - lzeros;
468
469 nbits = nbytes * 8;
470 if (nbits > MAX_EXTERN_MPI_BITS) {
471 pr_info("MPI: mpi too large (%u bits)\n", nbits);
472 return NULL;
473 }
474
475 if (nbytes > 0)
476 nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros));
477 else
478 nbits = 0;
479
480 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
481 val = mpi_alloc(nlimbs);
482 if (!val)
483 return NULL;
484
485 val->nbits = nbits;
486 val->sign = 0;
487 val->nlimbs = nlimbs;
488
489 if (nbytes == 0)
490 return val;
491
492 j = nlimbs - 1;
493 a = 0;
494 z = 0;
495 x = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
496 x %= BYTES_PER_MPI_LIMB;
497
498 for_each_sg(sgl, sg, ents, i) {
499 const u8 *buffer = sg_virt(sg) + lzeros;
500 int len = sg->length - lzeros;
501 int buf_shift = x;
502
503 if (sg_is_last(sg) && (len % BYTES_PER_MPI_LIMB))
504 len += BYTES_PER_MPI_LIMB - (len % BYTES_PER_MPI_LIMB);
505
506 for (; x < len + buf_shift; x++) {
507 a <<= 8;
508 a |= *buffer++;
509 if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
510 val->d[j--] = a;
511 a = 0;
512 }
513 }
514 z += x;
515 x = 0;
516 lzeros = 0;
517 }
518 return val;
519}
520EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);