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cdec9cb5 DK |
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 | ||
e1045992 | 21 | #include <linux/bitops.h> |
a1164a3a | 22 | #include <linux/count_zeros.h> |
cdec9cb5 DK |
23 | #include "mpi-internal.h" |
24 | ||
cdec9cb5 DK |
25 | #define MAX_EXTERN_MPI_BITS 16384 |
26 | ||
e1045992 DH |
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 | */ | |
32 | MPI 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 | ||
5402b804 | 40 | while (nbytes > 0 && buffer[0] == 0) { |
e1045992 DH |
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 | ||
0d2a1b2d | 55 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); |
e1045992 DH |
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 | } | |
78 | EXPORT_SYMBOL_GPL(mpi_read_raw_data); | |
79 | ||
cdec9cb5 DK |
80 | MPI 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; | |
3cccd154 | 86 | MPI val = NULL; |
cdec9cb5 DK |
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 | ||
0d2a1b2d AS |
99 | nbytes = DIV_ROUND_UP(nbits, 8); |
100 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); | |
cdec9cb5 DK |
101 | val = mpi_alloc(nlimbs); |
102 | if (!val) | |
3cccd154 | 103 | return NULL; |
cdec9cb5 DK |
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 | ||
125 | leave: | |
126 | *ret_nread = nread; | |
127 | return val; | |
128 | } | |
129 | EXPORT_SYMBOL_GPL(mpi_read_from_buffer); | |
130 | ||
3ee0cb5f MM |
131 | static int count_lzeros(MPI a) |
132 | { | |
133 | mpi_limb_t alimb; | |
134 | int i, lzeros = 0; | |
135 | ||
136 | for (i = a->nlimbs - 1; i >= 0; i--) { | |
137 | alimb = a->d[i]; | |
138 | if (alimb == 0) { | |
139 | lzeros += sizeof(mpi_limb_t); | |
140 | } else { | |
141 | lzeros += count_leading_zeros(alimb) / 8; | |
142 | break; | |
143 | } | |
144 | } | |
145 | return lzeros; | |
146 | } | |
147 | ||
d37e2969 TS |
148 | /** |
149 | * mpi_read_buffer() - read MPI to a bufer provided by user (msb first) | |
150 | * | |
151 | * @a: a multi precision integer | |
152 | * @buf: bufer to which the output will be written to. Needs to be at | |
153 | * leaset mpi_get_size(a) long. | |
154 | * @buf_len: size of the buf. | |
9cbe21d8 AZ |
155 | * @nbytes: receives the actual length of the data written on success and |
156 | * the data to-be-written on -EOVERFLOW in case buf_len was too | |
157 | * small. | |
d37e2969 TS |
158 | * @sign: if not NULL, it will be set to the sign of a. |
159 | * | |
160 | * Return: 0 on success or error code in case of error | |
cdec9cb5 | 161 | */ |
d37e2969 TS |
162 | int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes, |
163 | int *sign) | |
cdec9cb5 | 164 | { |
d37e2969 | 165 | uint8_t *p; |
cdec9cb5 | 166 | mpi_limb_t alimb; |
d37e2969 | 167 | unsigned int n = mpi_get_size(a); |
3ee0cb5f | 168 | int i, lzeros; |
d37e2969 | 169 | |
9cbe21d8 | 170 | if (!buf || !nbytes) |
d37e2969 | 171 | return -EINVAL; |
cdec9cb5 DK |
172 | |
173 | if (sign) | |
174 | *sign = a->sign; | |
d37e2969 | 175 | |
3ee0cb5f | 176 | lzeros = count_lzeros(a); |
d37e2969 | 177 | |
9cbe21d8 AZ |
178 | if (buf_len < n - lzeros) { |
179 | *nbytes = n - lzeros; | |
180 | return -EOVERFLOW; | |
181 | } | |
182 | ||
d37e2969 | 183 | p = buf; |
0f74fbf7 | 184 | *nbytes = n - lzeros; |
cdec9cb5 DK |
185 | |
186 | for (i = a->nlimbs - 1; i >= 0; i--) { | |
187 | alimb = a->d[i]; | |
188 | #if BYTES_PER_MPI_LIMB == 4 | |
189 | *p++ = alimb >> 24; | |
190 | *p++ = alimb >> 16; | |
191 | *p++ = alimb >> 8; | |
192 | *p++ = alimb; | |
193 | #elif BYTES_PER_MPI_LIMB == 8 | |
194 | *p++ = alimb >> 56; | |
195 | *p++ = alimb >> 48; | |
196 | *p++ = alimb >> 40; | |
197 | *p++ = alimb >> 32; | |
198 | *p++ = alimb >> 24; | |
199 | *p++ = alimb >> 16; | |
200 | *p++ = alimb >> 8; | |
201 | *p++ = alimb; | |
202 | #else | |
203 | #error please implement for this limb size. | |
204 | #endif | |
0f74fbf7 TS |
205 | |
206 | if (lzeros > 0) { | |
207 | if (lzeros >= sizeof(alimb)) { | |
208 | p -= sizeof(alimb); | |
209 | } else { | |
210 | mpi_limb_t *limb1 = (void *)p - sizeof(alimb); | |
211 | mpi_limb_t *limb2 = (void *)p - sizeof(alimb) | |
212 | + lzeros; | |
213 | *limb1 = *limb2; | |
214 | p -= lzeros; | |
215 | } | |
216 | lzeros -= sizeof(alimb); | |
217 | } | |
cdec9cb5 | 218 | } |
d37e2969 TS |
219 | return 0; |
220 | } | |
221 | EXPORT_SYMBOL_GPL(mpi_read_buffer); | |
222 | ||
223 | /* | |
224 | * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first). | |
225 | * Caller must free the return string. | |
226 | * This function does return a 0 byte buffer with nbytes set to zero if the | |
227 | * value of A is zero. | |
228 | * | |
229 | * @a: a multi precision integer. | |
230 | * @nbytes: receives the length of this buffer. | |
231 | * @sign: if not NULL, it will be set to the sign of the a. | |
232 | * | |
233 | * Return: Pointer to MPI buffer or NULL on error | |
234 | */ | |
235 | void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign) | |
236 | { | |
0f74fbf7 | 237 | uint8_t *buf; |
d37e2969 TS |
238 | unsigned int n; |
239 | int ret; | |
240 | ||
241 | if (!nbytes) | |
242 | return NULL; | |
243 | ||
244 | n = mpi_get_size(a); | |
245 | ||
246 | if (!n) | |
247 | n++; | |
248 | ||
249 | buf = kmalloc(n, GFP_KERNEL); | |
250 | ||
251 | if (!buf) | |
252 | return NULL; | |
253 | ||
254 | ret = mpi_read_buffer(a, buf, n, nbytes, sign); | |
255 | ||
256 | if (ret) { | |
257 | kfree(buf); | |
258 | return NULL; | |
259 | } | |
d37e2969 | 260 | return buf; |
cdec9cb5 DK |
261 | } |
262 | EXPORT_SYMBOL_GPL(mpi_get_buffer); | |
263 | ||
264 | /**************** | |
265 | * Use BUFFER to update MPI. | |
266 | */ | |
267 | int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign) | |
268 | { | |
269 | const uint8_t *buffer = xbuffer, *p; | |
270 | mpi_limb_t alimb; | |
271 | int nlimbs; | |
272 | int i; | |
273 | ||
0d2a1b2d | 274 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); |
cdec9cb5 DK |
275 | if (RESIZE_IF_NEEDED(a, nlimbs) < 0) |
276 | return -ENOMEM; | |
277 | a->sign = sign; | |
278 | ||
279 | for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) { | |
280 | #if BYTES_PER_MPI_LIMB == 4 | |
281 | alimb = (mpi_limb_t) *p--; | |
282 | alimb |= (mpi_limb_t) *p-- << 8; | |
283 | alimb |= (mpi_limb_t) *p-- << 16; | |
284 | alimb |= (mpi_limb_t) *p-- << 24; | |
285 | #elif BYTES_PER_MPI_LIMB == 8 | |
286 | alimb = (mpi_limb_t) *p--; | |
287 | alimb |= (mpi_limb_t) *p-- << 8; | |
288 | alimb |= (mpi_limb_t) *p-- << 16; | |
289 | alimb |= (mpi_limb_t) *p-- << 24; | |
290 | alimb |= (mpi_limb_t) *p-- << 32; | |
291 | alimb |= (mpi_limb_t) *p-- << 40; | |
292 | alimb |= (mpi_limb_t) *p-- << 48; | |
293 | alimb |= (mpi_limb_t) *p-- << 56; | |
294 | #else | |
295 | #error please implement for this limb size. | |
296 | #endif | |
297 | a->d[i++] = alimb; | |
298 | } | |
299 | if (p >= buffer) { | |
300 | #if BYTES_PER_MPI_LIMB == 4 | |
301 | alimb = *p--; | |
302 | if (p >= buffer) | |
303 | alimb |= (mpi_limb_t) *p-- << 8; | |
304 | if (p >= buffer) | |
305 | alimb |= (mpi_limb_t) *p-- << 16; | |
306 | if (p >= buffer) | |
307 | alimb |= (mpi_limb_t) *p-- << 24; | |
308 | #elif BYTES_PER_MPI_LIMB == 8 | |
309 | alimb = (mpi_limb_t) *p--; | |
310 | if (p >= buffer) | |
311 | alimb |= (mpi_limb_t) *p-- << 8; | |
312 | if (p >= buffer) | |
313 | alimb |= (mpi_limb_t) *p-- << 16; | |
314 | if (p >= buffer) | |
315 | alimb |= (mpi_limb_t) *p-- << 24; | |
316 | if (p >= buffer) | |
317 | alimb |= (mpi_limb_t) *p-- << 32; | |
318 | if (p >= buffer) | |
319 | alimb |= (mpi_limb_t) *p-- << 40; | |
320 | if (p >= buffer) | |
321 | alimb |= (mpi_limb_t) *p-- << 48; | |
322 | if (p >= buffer) | |
323 | alimb |= (mpi_limb_t) *p-- << 56; | |
324 | #else | |
325 | #error please implement for this limb size. | |
326 | #endif | |
327 | a->d[i++] = alimb; | |
328 | } | |
329 | a->nlimbs = i; | |
330 | ||
331 | if (i != nlimbs) { | |
332 | pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i, | |
333 | nlimbs); | |
334 | BUG(); | |
335 | } | |
336 | return 0; | |
337 | } | |
338 | EXPORT_SYMBOL_GPL(mpi_set_buffer); | |
2d4d1eea TS |
339 | |
340 | /** | |
341 | * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first) | |
342 | * | |
343 | * This function works in the same way as the mpi_read_buffer, but it | |
344 | * takes an sgl instead of u8 * buf. | |
345 | * | |
346 | * @a: a multi precision integer | |
347 | * @sgl: scatterlist to write to. Needs to be at least | |
348 | * mpi_get_size(a) long. | |
349 | * @nbytes: in/out param - it has the be set to the maximum number of | |
350 | * bytes that can be written to sgl. This has to be at least | |
351 | * the size of the integer a. On return it receives the actual | |
9cbe21d8 AZ |
352 | * length of the data written on success or the data that would |
353 | * be written if buffer was too small. | |
2d4d1eea TS |
354 | * @sign: if not NULL, it will be set to the sign of a. |
355 | * | |
356 | * Return: 0 on success or error code in case of error | |
357 | */ | |
358 | int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes, | |
359 | int *sign) | |
360 | { | |
361 | u8 *p, *p2; | |
362 | mpi_limb_t alimb, alimb2; | |
363 | unsigned int n = mpi_get_size(a); | |
3ee0cb5f | 364 | int i, x, y = 0, lzeros, buf_len; |
2d4d1eea | 365 | |
9cbe21d8 | 366 | if (!nbytes) |
2d4d1eea TS |
367 | return -EINVAL; |
368 | ||
369 | if (sign) | |
370 | *sign = a->sign; | |
371 | ||
3ee0cb5f | 372 | lzeros = count_lzeros(a); |
2d4d1eea | 373 | |
9cbe21d8 AZ |
374 | if (*nbytes < n - lzeros) { |
375 | *nbytes = n - lzeros; | |
376 | return -EOVERFLOW; | |
377 | } | |
378 | ||
2d4d1eea TS |
379 | *nbytes = n - lzeros; |
380 | buf_len = sgl->length; | |
381 | p2 = sg_virt(sgl); | |
382 | ||
383 | for (i = a->nlimbs - 1; i >= 0; i--) { | |
384 | alimb = a->d[i]; | |
385 | p = (u8 *)&alimb2; | |
386 | #if BYTES_PER_MPI_LIMB == 4 | |
387 | *p++ = alimb >> 24; | |
388 | *p++ = alimb >> 16; | |
389 | *p++ = alimb >> 8; | |
390 | *p++ = alimb; | |
391 | #elif BYTES_PER_MPI_LIMB == 8 | |
392 | *p++ = alimb >> 56; | |
393 | *p++ = alimb >> 48; | |
394 | *p++ = alimb >> 40; | |
395 | *p++ = alimb >> 32; | |
396 | *p++ = alimb >> 24; | |
397 | *p++ = alimb >> 16; | |
398 | *p++ = alimb >> 8; | |
399 | *p++ = alimb; | |
400 | #else | |
401 | #error please implement for this limb size. | |
402 | #endif | |
403 | if (lzeros > 0) { | |
404 | if (lzeros >= sizeof(alimb)) { | |
405 | p -= sizeof(alimb); | |
406 | continue; | |
407 | } else { | |
408 | mpi_limb_t *limb1 = (void *)p - sizeof(alimb); | |
409 | mpi_limb_t *limb2 = (void *)p - sizeof(alimb) | |
410 | + lzeros; | |
411 | *limb1 = *limb2; | |
412 | p -= lzeros; | |
413 | y = lzeros; | |
414 | } | |
415 | lzeros -= sizeof(alimb); | |
416 | } | |
417 | ||
418 | p = p - (sizeof(alimb) - y); | |
419 | ||
420 | for (x = 0; x < sizeof(alimb) - y; x++) { | |
421 | if (!buf_len) { | |
422 | sgl = sg_next(sgl); | |
423 | if (!sgl) | |
424 | return -EINVAL; | |
425 | buf_len = sgl->length; | |
426 | p2 = sg_virt(sgl); | |
427 | } | |
428 | *p2++ = *p++; | |
429 | buf_len--; | |
430 | } | |
431 | y = 0; | |
432 | } | |
433 | return 0; | |
434 | } | |
435 | EXPORT_SYMBOL_GPL(mpi_write_to_sgl); | |
436 | ||
437 | /* | |
438 | * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with | |
439 | * data from the sgl | |
440 | * | |
441 | * This function works in the same way as the mpi_read_raw_data, but it | |
442 | * takes an sgl instead of void * buffer. i.e. it allocates | |
443 | * a new MPI and reads the content of the sgl to the MPI. | |
444 | * | |
445 | * @sgl: scatterlist to read from | |
446 | * @len: number of bytes to read | |
447 | * | |
448 | * Return: Pointer to a new MPI or NULL on error | |
449 | */ | |
450 | MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int len) | |
451 | { | |
452 | struct scatterlist *sg; | |
453 | int x, i, j, z, lzeros, ents; | |
454 | unsigned int nbits, nlimbs, nbytes; | |
455 | mpi_limb_t a; | |
456 | MPI val = NULL; | |
457 | ||
458 | lzeros = 0; | |
459 | ents = sg_nents(sgl); | |
460 | ||
461 | for_each_sg(sgl, sg, ents, i) { | |
462 | const u8 *buff = sg_virt(sg); | |
463 | int len = sg->length; | |
464 | ||
63349d02 | 465 | while (len && !*buff) { |
2d4d1eea | 466 | lzeros++; |
63349d02 SM |
467 | len--; |
468 | buff++; | |
469 | } | |
2d4d1eea TS |
470 | |
471 | if (len && *buff) | |
472 | break; | |
473 | ||
474 | ents--; | |
475 | lzeros = 0; | |
476 | } | |
477 | ||
478 | sgl = sg; | |
479 | ||
480 | if (!ents) | |
481 | nbytes = 0; | |
482 | else | |
483 | nbytes = len - lzeros; | |
484 | ||
485 | nbits = nbytes * 8; | |
486 | if (nbits > MAX_EXTERN_MPI_BITS) { | |
487 | pr_info("MPI: mpi too large (%u bits)\n", nbits); | |
488 | return NULL; | |
489 | } | |
490 | ||
491 | if (nbytes > 0) | |
492 | nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros)); | |
493 | else | |
494 | nbits = 0; | |
495 | ||
496 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); | |
497 | val = mpi_alloc(nlimbs); | |
498 | if (!val) | |
499 | return NULL; | |
500 | ||
501 | val->nbits = nbits; | |
502 | val->sign = 0; | |
503 | val->nlimbs = nlimbs; | |
504 | ||
505 | if (nbytes == 0) | |
506 | return val; | |
507 | ||
508 | j = nlimbs - 1; | |
509 | a = 0; | |
510 | z = 0; | |
511 | x = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; | |
512 | x %= BYTES_PER_MPI_LIMB; | |
513 | ||
514 | for_each_sg(sgl, sg, ents, i) { | |
515 | const u8 *buffer = sg_virt(sg) + lzeros; | |
516 | int len = sg->length - lzeros; | |
517 | int buf_shift = x; | |
518 | ||
519 | if (sg_is_last(sg) && (len % BYTES_PER_MPI_LIMB)) | |
520 | len += BYTES_PER_MPI_LIMB - (len % BYTES_PER_MPI_LIMB); | |
521 | ||
522 | for (; x < len + buf_shift; x++) { | |
523 | a <<= 8; | |
524 | a |= *buffer++; | |
525 | if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) { | |
526 | val->d[j--] = a; | |
527 | a = 0; | |
528 | } | |
529 | } | |
530 | z += x; | |
531 | x = 0; | |
532 | lzeros = 0; | |
533 | } | |
534 | return val; | |
535 | } | |
536 | EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl); |