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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
131static 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
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.
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.
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
161 */
162int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
163 int *sign)
164{
165 uint8_t *p;
166 mpi_limb_t alimb;
167 unsigned int n = mpi_get_size(a);
168 int i, lzeros;
169
170 if (!buf || !nbytes)
171 return -EINVAL;
172
173 if (sign)
174 *sign = a->sign;
175
176 lzeros = count_lzeros(a);
177
178 if (buf_len < n - lzeros) {
179 *nbytes = n - lzeros;
180 return -EOVERFLOW;
181 }
182
183 p = buf;
184 *nbytes = n - lzeros;
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
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 }
218 }
219 return 0;
220}
221EXPORT_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 */
235void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
236{
237 uint8_t *buf;
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 }
260 return buf;
261}
262EXPORT_SYMBOL_GPL(mpi_get_buffer);
263
264/****************
265 * Use BUFFER to update MPI.
266 */
267int 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
274 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
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}
338EXPORT_SYMBOL_GPL(mpi_set_buffer);
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
352 * length of the data written on success or the data that would
353 * be written if buffer was too small.
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 */
358int 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);
364 int i, x, y = 0, lzeros, buf_len;
365
366 if (!nbytes)
367 return -EINVAL;
368
369 if (sign)
370 *sign = a->sign;
371
372 lzeros = count_lzeros(a);
373
374 if (*nbytes < n - lzeros) {
375 *nbytes = n - lzeros;
376 return -EOVERFLOW;
377 }
378
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}
435EXPORT_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 */
450MPI 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
465 while (len && !*buff) {
466 lzeros++;
467 len--;
468 buff++;
469 }
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}
536EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);