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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> |
d7552906 | 23 | #include <linux/byteorder/generic.h> |
127827b9 | 24 | #include <linux/scatterlist.h> |
90f864e2 | 25 | #include <linux/string.h> |
cdec9cb5 DK |
26 | #include "mpi-internal.h" |
27 | ||
cdec9cb5 DK |
28 | #define MAX_EXTERN_MPI_BITS 16384 |
29 | ||
e1045992 DH |
30 | /** |
31 | * mpi_read_raw_data - Read a raw byte stream as a positive integer | |
32 | * @xbuffer: The data to read | |
33 | * @nbytes: The amount of data to read | |
34 | */ | |
35 | MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes) | |
36 | { | |
37 | const uint8_t *buffer = xbuffer; | |
38 | int i, j; | |
39 | unsigned nbits, nlimbs; | |
40 | mpi_limb_t a; | |
41 | MPI val = NULL; | |
42 | ||
5402b804 | 43 | while (nbytes > 0 && buffer[0] == 0) { |
e1045992 DH |
44 | buffer++; |
45 | nbytes--; | |
46 | } | |
47 | ||
48 | nbits = nbytes * 8; | |
49 | if (nbits > MAX_EXTERN_MPI_BITS) { | |
50 | pr_info("MPI: mpi too large (%u bits)\n", nbits); | |
51 | return NULL; | |
52 | } | |
53 | if (nbytes > 0) | |
eef0df6a | 54 | nbits -= count_leading_zeros(buffer[0]) - (BITS_PER_LONG - 8); |
e1045992 | 55 | |
0d2a1b2d | 56 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); |
e1045992 DH |
57 | val = mpi_alloc(nlimbs); |
58 | if (!val) | |
59 | return NULL; | |
60 | val->nbits = nbits; | |
61 | val->sign = 0; | |
62 | val->nlimbs = nlimbs; | |
63 | ||
64 | if (nbytes > 0) { | |
65 | i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; | |
66 | i %= BYTES_PER_MPI_LIMB; | |
67 | for (j = nlimbs; j > 0; j--) { | |
68 | a = 0; | |
69 | for (; i < BYTES_PER_MPI_LIMB; i++) { | |
70 | a <<= 8; | |
71 | a |= *buffer++; | |
72 | } | |
73 | i = 0; | |
74 | val->d[j - 1] = a; | |
75 | } | |
76 | } | |
77 | return val; | |
78 | } | |
79 | EXPORT_SYMBOL_GPL(mpi_read_raw_data); | |
80 | ||
cdec9cb5 DK |
81 | MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread) |
82 | { | |
83 | const uint8_t *buffer = xbuffer; | |
20b5b7f3 NS |
84 | unsigned int nbits, nbytes; |
85 | MPI val; | |
cdec9cb5 DK |
86 | |
87 | if (*ret_nread < 2) | |
03cdfaad | 88 | return ERR_PTR(-EINVAL); |
cdec9cb5 DK |
89 | nbits = buffer[0] << 8 | buffer[1]; |
90 | ||
91 | if (nbits > MAX_EXTERN_MPI_BITS) { | |
92 | pr_info("MPI: mpi too large (%u bits)\n", nbits); | |
03cdfaad | 93 | return ERR_PTR(-EINVAL); |
cdec9cb5 | 94 | } |
cdec9cb5 | 95 | |
0d2a1b2d | 96 | nbytes = DIV_ROUND_UP(nbits, 8); |
7af791e0 | 97 | if (nbytes + 2 > *ret_nread) { |
cdf24b42 NS |
98 | pr_info("MPI: mpi larger than buffer nbytes=%u ret_nread=%u\n", |
99 | nbytes, *ret_nread); | |
7af791e0 NS |
100 | return ERR_PTR(-EINVAL); |
101 | } | |
102 | ||
20b5b7f3 | 103 | val = mpi_read_raw_data(buffer + 2, nbytes); |
cdec9cb5 | 104 | if (!val) |
03cdfaad | 105 | return ERR_PTR(-ENOMEM); |
cdec9cb5 | 106 | |
7af791e0 | 107 | *ret_nread = nbytes + 2; |
cdec9cb5 DK |
108 | return val; |
109 | } | |
110 | EXPORT_SYMBOL_GPL(mpi_read_from_buffer); | |
111 | ||
3ee0cb5f MM |
112 | static int count_lzeros(MPI a) |
113 | { | |
114 | mpi_limb_t alimb; | |
115 | int i, lzeros = 0; | |
116 | ||
117 | for (i = a->nlimbs - 1; i >= 0; i--) { | |
118 | alimb = a->d[i]; | |
119 | if (alimb == 0) { | |
120 | lzeros += sizeof(mpi_limb_t); | |
121 | } else { | |
122 | lzeros += count_leading_zeros(alimb) / 8; | |
123 | break; | |
124 | } | |
125 | } | |
126 | return lzeros; | |
127 | } | |
128 | ||
d37e2969 TS |
129 | /** |
130 | * mpi_read_buffer() - read MPI to a bufer provided by user (msb first) | |
131 | * | |
132 | * @a: a multi precision integer | |
133 | * @buf: bufer to which the output will be written to. Needs to be at | |
134 | * leaset mpi_get_size(a) long. | |
135 | * @buf_len: size of the buf. | |
9cbe21d8 AZ |
136 | * @nbytes: receives the actual length of the data written on success and |
137 | * the data to-be-written on -EOVERFLOW in case buf_len was too | |
138 | * small. | |
d37e2969 TS |
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 | |
cdec9cb5 | 142 | */ |
d37e2969 TS |
143 | int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes, |
144 | int *sign) | |
cdec9cb5 | 145 | { |
d37e2969 | 146 | uint8_t *p; |
90f864e2 NS |
147 | #if BYTES_PER_MPI_LIMB == 4 |
148 | __be32 alimb; | |
149 | #elif BYTES_PER_MPI_LIMB == 8 | |
150 | __be64 alimb; | |
151 | #else | |
152 | #error please implement for this limb size. | |
153 | #endif | |
d37e2969 | 154 | unsigned int n = mpi_get_size(a); |
3ee0cb5f | 155 | int i, lzeros; |
d37e2969 | 156 | |
9cbe21d8 | 157 | if (!buf || !nbytes) |
d37e2969 | 158 | return -EINVAL; |
cdec9cb5 DK |
159 | |
160 | if (sign) | |
161 | *sign = a->sign; | |
d37e2969 | 162 | |
3ee0cb5f | 163 | lzeros = count_lzeros(a); |
d37e2969 | 164 | |
9cbe21d8 AZ |
165 | if (buf_len < n - lzeros) { |
166 | *nbytes = n - lzeros; | |
167 | return -EOVERFLOW; | |
168 | } | |
169 | ||
d37e2969 | 170 | p = buf; |
0f74fbf7 | 171 | *nbytes = n - lzeros; |
cdec9cb5 | 172 | |
f00fa241 NS |
173 | for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB, |
174 | lzeros %= BYTES_PER_MPI_LIMB; | |
175 | i >= 0; i--) { | |
cdec9cb5 | 176 | #if BYTES_PER_MPI_LIMB == 4 |
90f864e2 | 177 | alimb = cpu_to_be32(a->d[i]); |
cdec9cb5 | 178 | #elif BYTES_PER_MPI_LIMB == 8 |
90f864e2 | 179 | alimb = cpu_to_be64(a->d[i]); |
cdec9cb5 DK |
180 | #else |
181 | #error please implement for this limb size. | |
182 | #endif | |
462696fd NS |
183 | memcpy(p, (u8 *)&alimb + lzeros, BYTES_PER_MPI_LIMB - lzeros); |
184 | p += BYTES_PER_MPI_LIMB - lzeros; | |
185 | lzeros = 0; | |
cdec9cb5 | 186 | } |
d37e2969 TS |
187 | return 0; |
188 | } | |
189 | EXPORT_SYMBOL_GPL(mpi_read_buffer); | |
190 | ||
191 | /* | |
192 | * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first). | |
193 | * Caller must free the return string. | |
194 | * This function does return a 0 byte buffer with nbytes set to zero if the | |
195 | * value of A is zero. | |
196 | * | |
197 | * @a: a multi precision integer. | |
198 | * @nbytes: receives the length of this buffer. | |
199 | * @sign: if not NULL, it will be set to the sign of the a. | |
200 | * | |
201 | * Return: Pointer to MPI buffer or NULL on error | |
202 | */ | |
203 | void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign) | |
204 | { | |
0f74fbf7 | 205 | uint8_t *buf; |
d37e2969 TS |
206 | unsigned int n; |
207 | int ret; | |
208 | ||
209 | if (!nbytes) | |
210 | return NULL; | |
211 | ||
212 | n = mpi_get_size(a); | |
213 | ||
214 | if (!n) | |
215 | n++; | |
216 | ||
217 | buf = kmalloc(n, GFP_KERNEL); | |
218 | ||
219 | if (!buf) | |
220 | return NULL; | |
221 | ||
222 | ret = mpi_read_buffer(a, buf, n, nbytes, sign); | |
223 | ||
224 | if (ret) { | |
225 | kfree(buf); | |
226 | return NULL; | |
227 | } | |
d37e2969 | 228 | return buf; |
cdec9cb5 DK |
229 | } |
230 | EXPORT_SYMBOL_GPL(mpi_get_buffer); | |
231 | ||
2d4d1eea TS |
232 | /** |
233 | * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first) | |
234 | * | |
235 | * This function works in the same way as the mpi_read_buffer, but it | |
236 | * takes an sgl instead of u8 * buf. | |
237 | * | |
238 | * @a: a multi precision integer | |
239 | * @sgl: scatterlist to write to. Needs to be at least | |
240 | * mpi_get_size(a) long. | |
9b45b7bb HX |
241 | * @nbytes: the number of bytes to write. Leading bytes will be |
242 | * filled with zero. | |
2d4d1eea TS |
243 | * @sign: if not NULL, it will be set to the sign of a. |
244 | * | |
245 | * Return: 0 on success or error code in case of error | |
246 | */ | |
9b45b7bb | 247 | int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned nbytes, |
2d4d1eea TS |
248 | int *sign) |
249 | { | |
250 | u8 *p, *p2; | |
d7552906 NS |
251 | #if BYTES_PER_MPI_LIMB == 4 |
252 | __be32 alimb; | |
253 | #elif BYTES_PER_MPI_LIMB == 8 | |
254 | __be64 alimb; | |
255 | #else | |
256 | #error please implement for this limb size. | |
257 | #endif | |
2d4d1eea | 258 | unsigned int n = mpi_get_size(a); |
127827b9 | 259 | struct sg_mapping_iter miter; |
9b45b7bb | 260 | int i, x, buf_len; |
127827b9 | 261 | int nents; |
2d4d1eea TS |
262 | |
263 | if (sign) | |
264 | *sign = a->sign; | |
265 | ||
9b45b7bb | 266 | if (nbytes < n) |
9cbe21d8 | 267 | return -EOVERFLOW; |
9cbe21d8 | 268 | |
127827b9 HX |
269 | nents = sg_nents_for_len(sgl, nbytes); |
270 | if (nents < 0) | |
271 | return -EINVAL; | |
2d4d1eea | 272 | |
127827b9 HX |
273 | sg_miter_start(&miter, sgl, nents, SG_MITER_ATOMIC | SG_MITER_TO_SG); |
274 | sg_miter_next(&miter); | |
275 | buf_len = miter.length; | |
276 | p2 = miter.addr; | |
9b45b7bb | 277 | |
127827b9 | 278 | while (nbytes > n) { |
9b45b7bb HX |
279 | i = min_t(unsigned, nbytes - n, buf_len); |
280 | memset(p2, 0, i); | |
281 | p2 += i; | |
9b45b7bb | 282 | nbytes -= i; |
127827b9 HX |
283 | |
284 | buf_len -= i; | |
285 | if (!buf_len) { | |
286 | sg_miter_next(&miter); | |
287 | buf_len = miter.length; | |
288 | p2 = miter.addr; | |
289 | } | |
9b45b7bb HX |
290 | } |
291 | ||
292 | for (i = a->nlimbs - 1; i >= 0; i--) { | |
2d4d1eea | 293 | #if BYTES_PER_MPI_LIMB == 4 |
9b45b7bb | 294 | alimb = a->d[i] ? cpu_to_be32(a->d[i]) : 0; |
2d4d1eea | 295 | #elif BYTES_PER_MPI_LIMB == 8 |
9b45b7bb | 296 | alimb = a->d[i] ? cpu_to_be64(a->d[i]) : 0; |
2d4d1eea TS |
297 | #else |
298 | #error please implement for this limb size. | |
299 | #endif | |
9b45b7bb | 300 | p = (u8 *)&alimb; |
2d4d1eea | 301 | |
9b45b7bb | 302 | for (x = 0; x < sizeof(alimb); x++) { |
2d4d1eea | 303 | *p2++ = *p++; |
127827b9 HX |
304 | if (!--buf_len) { |
305 | sg_miter_next(&miter); | |
306 | buf_len = miter.length; | |
307 | p2 = miter.addr; | |
308 | } | |
2d4d1eea | 309 | } |
2d4d1eea | 310 | } |
127827b9 HX |
311 | |
312 | sg_miter_stop(&miter); | |
2d4d1eea TS |
313 | return 0; |
314 | } | |
315 | EXPORT_SYMBOL_GPL(mpi_write_to_sgl); | |
316 | ||
317 | /* | |
318 | * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with | |
319 | * data from the sgl | |
320 | * | |
321 | * This function works in the same way as the mpi_read_raw_data, but it | |
322 | * takes an sgl instead of void * buffer. i.e. it allocates | |
323 | * a new MPI and reads the content of the sgl to the MPI. | |
324 | * | |
325 | * @sgl: scatterlist to read from | |
b6985389 | 326 | * @nbytes: number of bytes to read |
2d4d1eea TS |
327 | * |
328 | * Return: Pointer to a new MPI or NULL on error | |
329 | */ | |
b6985389 | 330 | MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes) |
2d4d1eea | 331 | { |
127827b9 | 332 | struct sg_mapping_iter miter; |
b6985389 | 333 | unsigned int nbits, nlimbs; |
127827b9 HX |
334 | int x, j, z, lzeros, ents; |
335 | unsigned int len; | |
336 | const u8 *buff; | |
2d4d1eea TS |
337 | mpi_limb_t a; |
338 | MPI val = NULL; | |
339 | ||
127827b9 HX |
340 | ents = sg_nents_for_len(sgl, nbytes); |
341 | if (ents < 0) | |
342 | return NULL; | |
2d4d1eea | 343 | |
127827b9 | 344 | sg_miter_start(&miter, sgl, ents, SG_MITER_ATOMIC | SG_MITER_FROM_SG); |
2d4d1eea | 345 | |
127827b9 HX |
346 | lzeros = 0; |
347 | len = 0; | |
348 | while (nbytes > 0) { | |
63349d02 | 349 | while (len && !*buff) { |
2d4d1eea | 350 | lzeros++; |
63349d02 SM |
351 | len--; |
352 | buff++; | |
353 | } | |
2d4d1eea TS |
354 | |
355 | if (len && *buff) | |
356 | break; | |
357 | ||
127827b9 HX |
358 | sg_miter_next(&miter); |
359 | buff = miter.addr; | |
360 | len = miter.length; | |
361 | ||
ab1e912e | 362 | nbytes -= lzeros; |
2d4d1eea TS |
363 | lzeros = 0; |
364 | } | |
365 | ||
4816c940 | 366 | miter.consumed = lzeros; |
4816c940 | 367 | |
ab1e912e | 368 | nbytes -= lzeros; |
2d4d1eea TS |
369 | nbits = nbytes * 8; |
370 | if (nbits > MAX_EXTERN_MPI_BITS) { | |
dea3eb8b | 371 | sg_miter_stop(&miter); |
2d4d1eea TS |
372 | pr_info("MPI: mpi too large (%u bits)\n", nbits); |
373 | return NULL; | |
374 | } | |
375 | ||
376 | if (nbytes > 0) | |
127827b9 | 377 | nbits -= count_leading_zeros(*buff) - (BITS_PER_LONG - 8); |
2d4d1eea | 378 | |
dea3eb8b SM |
379 | sg_miter_stop(&miter); |
380 | ||
2d4d1eea TS |
381 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); |
382 | val = mpi_alloc(nlimbs); | |
383 | if (!val) | |
384 | return NULL; | |
385 | ||
386 | val->nbits = nbits; | |
387 | val->sign = 0; | |
388 | val->nlimbs = nlimbs; | |
389 | ||
390 | if (nbytes == 0) | |
391 | return val; | |
392 | ||
393 | j = nlimbs - 1; | |
394 | a = 0; | |
85d541a3 NS |
395 | z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; |
396 | z %= BYTES_PER_MPI_LIMB; | |
2d4d1eea | 397 | |
4816c940 HX |
398 | while (sg_miter_next(&miter)) { |
399 | buff = miter.addr; | |
400 | len = miter.length; | |
401 | ||
85d541a3 | 402 | for (x = 0; x < len; x++) { |
2d4d1eea | 403 | a <<= 8; |
127827b9 | 404 | a |= *buff++; |
2d4d1eea TS |
405 | if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) { |
406 | val->d[j--] = a; | |
407 | a = 0; | |
408 | } | |
409 | } | |
410 | z += x; | |
2d4d1eea | 411 | } |
127827b9 | 412 | |
2d4d1eea TS |
413 | return val; |
414 | } | |
415 | EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl); |