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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> |
90f864e2 | 24 | #include <linux/string.h> |
cdec9cb5 DK |
25 | #include "mpi-internal.h" |
26 | ||
cdec9cb5 DK |
27 | #define MAX_EXTERN_MPI_BITS 16384 |
28 | ||
e1045992 DH |
29 | /** |
30 | * mpi_read_raw_data - Read a raw byte stream as a positive integer | |
31 | * @xbuffer: The data to read | |
32 | * @nbytes: The amount of data to read | |
33 | */ | |
34 | MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes) | |
35 | { | |
36 | const uint8_t *buffer = xbuffer; | |
37 | int i, j; | |
38 | unsigned nbits, nlimbs; | |
39 | mpi_limb_t a; | |
40 | MPI val = NULL; | |
41 | ||
5402b804 | 42 | while (nbytes > 0 && buffer[0] == 0) { |
e1045992 DH |
43 | buffer++; |
44 | nbytes--; | |
45 | } | |
46 | ||
47 | nbits = nbytes * 8; | |
48 | if (nbits > MAX_EXTERN_MPI_BITS) { | |
49 | pr_info("MPI: mpi too large (%u bits)\n", nbits); | |
50 | return NULL; | |
51 | } | |
52 | if (nbytes > 0) | |
eef0df6a | 53 | nbits -= count_leading_zeros(buffer[0]) - (BITS_PER_LONG - 8); |
e1045992 | 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; | |
7af791e0 | 84 | unsigned nbits, nbytes, nlimbs; |
cdec9cb5 | 85 | mpi_limb_t a; |
3cccd154 | 86 | MPI val = NULL; |
cdec9cb5 DK |
87 | |
88 | if (*ret_nread < 2) | |
03cdfaad | 89 | return ERR_PTR(-EINVAL); |
cdec9cb5 DK |
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); | |
03cdfaad | 94 | return ERR_PTR(-EINVAL); |
cdec9cb5 DK |
95 | } |
96 | buffer += 2; | |
cdec9cb5 | 97 | |
0d2a1b2d | 98 | nbytes = DIV_ROUND_UP(nbits, 8); |
7af791e0 NS |
99 | if (nbytes + 2 > *ret_nread) { |
100 | printk("MPI: mpi larger than buffer nread=%d ret_nread=%d\n", | |
101 | *ret_nread + 1, *ret_nread); | |
102 | return ERR_PTR(-EINVAL); | |
103 | } | |
104 | ||
0d2a1b2d | 105 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); |
cdec9cb5 DK |
106 | val = mpi_alloc(nlimbs); |
107 | if (!val) | |
03cdfaad | 108 | return ERR_PTR(-ENOMEM); |
cdec9cb5 DK |
109 | i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; |
110 | i %= BYTES_PER_MPI_LIMB; | |
111 | val->nbits = nbits; | |
112 | j = val->nlimbs = nlimbs; | |
113 | val->sign = 0; | |
114 | for (; j > 0; j--) { | |
115 | a = 0; | |
116 | for (; i < BYTES_PER_MPI_LIMB; i++) { | |
cdec9cb5 DK |
117 | a <<= 8; |
118 | a |= *buffer++; | |
119 | } | |
120 | i = 0; | |
121 | val->d[j - 1] = a; | |
122 | } | |
123 | ||
7af791e0 | 124 | *ret_nread = nbytes + 2; |
cdec9cb5 DK |
125 | return val; |
126 | } | |
127 | EXPORT_SYMBOL_GPL(mpi_read_from_buffer); | |
128 | ||
3ee0cb5f MM |
129 | static int count_lzeros(MPI a) |
130 | { | |
131 | mpi_limb_t alimb; | |
132 | int i, lzeros = 0; | |
133 | ||
134 | for (i = a->nlimbs - 1; i >= 0; i--) { | |
135 | alimb = a->d[i]; | |
136 | if (alimb == 0) { | |
137 | lzeros += sizeof(mpi_limb_t); | |
138 | } else { | |
139 | lzeros += count_leading_zeros(alimb) / 8; | |
140 | break; | |
141 | } | |
142 | } | |
143 | return lzeros; | |
144 | } | |
145 | ||
d37e2969 TS |
146 | /** |
147 | * mpi_read_buffer() - read MPI to a bufer provided by user (msb first) | |
148 | * | |
149 | * @a: a multi precision integer | |
150 | * @buf: bufer to which the output will be written to. Needs to be at | |
151 | * leaset mpi_get_size(a) long. | |
152 | * @buf_len: size of the buf. | |
9cbe21d8 AZ |
153 | * @nbytes: receives the actual length of the data written on success and |
154 | * the data to-be-written on -EOVERFLOW in case buf_len was too | |
155 | * small. | |
d37e2969 TS |
156 | * @sign: if not NULL, it will be set to the sign of a. |
157 | * | |
158 | * Return: 0 on success or error code in case of error | |
cdec9cb5 | 159 | */ |
d37e2969 TS |
160 | int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes, |
161 | int *sign) | |
cdec9cb5 | 162 | { |
d37e2969 | 163 | uint8_t *p; |
90f864e2 NS |
164 | #if BYTES_PER_MPI_LIMB == 4 |
165 | __be32 alimb; | |
166 | #elif BYTES_PER_MPI_LIMB == 8 | |
167 | __be64 alimb; | |
168 | #else | |
169 | #error please implement for this limb size. | |
170 | #endif | |
d37e2969 | 171 | unsigned int n = mpi_get_size(a); |
3ee0cb5f | 172 | int i, lzeros; |
d37e2969 | 173 | |
9cbe21d8 | 174 | if (!buf || !nbytes) |
d37e2969 | 175 | return -EINVAL; |
cdec9cb5 DK |
176 | |
177 | if (sign) | |
178 | *sign = a->sign; | |
d37e2969 | 179 | |
3ee0cb5f | 180 | lzeros = count_lzeros(a); |
d37e2969 | 181 | |
9cbe21d8 AZ |
182 | if (buf_len < n - lzeros) { |
183 | *nbytes = n - lzeros; | |
184 | return -EOVERFLOW; | |
185 | } | |
186 | ||
d37e2969 | 187 | p = buf; |
0f74fbf7 | 188 | *nbytes = n - lzeros; |
cdec9cb5 | 189 | |
f00fa241 NS |
190 | for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB, |
191 | lzeros %= BYTES_PER_MPI_LIMB; | |
192 | i >= 0; i--) { | |
cdec9cb5 | 193 | #if BYTES_PER_MPI_LIMB == 4 |
90f864e2 | 194 | alimb = cpu_to_be32(a->d[i]); |
cdec9cb5 | 195 | #elif BYTES_PER_MPI_LIMB == 8 |
90f864e2 | 196 | alimb = cpu_to_be64(a->d[i]); |
cdec9cb5 DK |
197 | #else |
198 | #error please implement for this limb size. | |
199 | #endif | |
462696fd NS |
200 | memcpy(p, (u8 *)&alimb + lzeros, BYTES_PER_MPI_LIMB - lzeros); |
201 | p += BYTES_PER_MPI_LIMB - lzeros; | |
202 | lzeros = 0; | |
cdec9cb5 | 203 | } |
d37e2969 TS |
204 | return 0; |
205 | } | |
206 | EXPORT_SYMBOL_GPL(mpi_read_buffer); | |
207 | ||
208 | /* | |
209 | * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first). | |
210 | * Caller must free the return string. | |
211 | * This function does return a 0 byte buffer with nbytes set to zero if the | |
212 | * value of A is zero. | |
213 | * | |
214 | * @a: a multi precision integer. | |
215 | * @nbytes: receives the length of this buffer. | |
216 | * @sign: if not NULL, it will be set to the sign of the a. | |
217 | * | |
218 | * Return: Pointer to MPI buffer or NULL on error | |
219 | */ | |
220 | void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign) | |
221 | { | |
0f74fbf7 | 222 | uint8_t *buf; |
d37e2969 TS |
223 | unsigned int n; |
224 | int ret; | |
225 | ||
226 | if (!nbytes) | |
227 | return NULL; | |
228 | ||
229 | n = mpi_get_size(a); | |
230 | ||
231 | if (!n) | |
232 | n++; | |
233 | ||
234 | buf = kmalloc(n, GFP_KERNEL); | |
235 | ||
236 | if (!buf) | |
237 | return NULL; | |
238 | ||
239 | ret = mpi_read_buffer(a, buf, n, nbytes, sign); | |
240 | ||
241 | if (ret) { | |
242 | kfree(buf); | |
243 | return NULL; | |
244 | } | |
d37e2969 | 245 | return buf; |
cdec9cb5 DK |
246 | } |
247 | EXPORT_SYMBOL_GPL(mpi_get_buffer); | |
248 | ||
2d4d1eea TS |
249 | /** |
250 | * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first) | |
251 | * | |
252 | * This function works in the same way as the mpi_read_buffer, but it | |
253 | * takes an sgl instead of u8 * buf. | |
254 | * | |
255 | * @a: a multi precision integer | |
256 | * @sgl: scatterlist to write to. Needs to be at least | |
257 | * mpi_get_size(a) long. | |
258 | * @nbytes: in/out param - it has the be set to the maximum number of | |
259 | * bytes that can be written to sgl. This has to be at least | |
260 | * the size of the integer a. On return it receives the actual | |
9cbe21d8 AZ |
261 | * length of the data written on success or the data that would |
262 | * be written if buffer was too small. | |
2d4d1eea TS |
263 | * @sign: if not NULL, it will be set to the sign of a. |
264 | * | |
265 | * Return: 0 on success or error code in case of error | |
266 | */ | |
267 | int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes, | |
268 | int *sign) | |
269 | { | |
270 | u8 *p, *p2; | |
d7552906 NS |
271 | #if BYTES_PER_MPI_LIMB == 4 |
272 | __be32 alimb; | |
273 | #elif BYTES_PER_MPI_LIMB == 8 | |
274 | __be64 alimb; | |
275 | #else | |
276 | #error please implement for this limb size. | |
277 | #endif | |
2d4d1eea | 278 | unsigned int n = mpi_get_size(a); |
3ee0cb5f | 279 | int i, x, y = 0, lzeros, buf_len; |
2d4d1eea | 280 | |
9cbe21d8 | 281 | if (!nbytes) |
2d4d1eea TS |
282 | return -EINVAL; |
283 | ||
284 | if (sign) | |
285 | *sign = a->sign; | |
286 | ||
3ee0cb5f | 287 | lzeros = count_lzeros(a); |
2d4d1eea | 288 | |
9cbe21d8 AZ |
289 | if (*nbytes < n - lzeros) { |
290 | *nbytes = n - lzeros; | |
291 | return -EOVERFLOW; | |
292 | } | |
293 | ||
2d4d1eea TS |
294 | *nbytes = n - lzeros; |
295 | buf_len = sgl->length; | |
296 | p2 = sg_virt(sgl); | |
297 | ||
f2d1362f NS |
298 | for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB, |
299 | lzeros %= BYTES_PER_MPI_LIMB; | |
300 | i >= 0; i--) { | |
2d4d1eea | 301 | #if BYTES_PER_MPI_LIMB == 4 |
d7552906 | 302 | alimb = cpu_to_be32(a->d[i]); |
2d4d1eea | 303 | #elif BYTES_PER_MPI_LIMB == 8 |
d7552906 | 304 | alimb = cpu_to_be64(a->d[i]); |
2d4d1eea TS |
305 | #else |
306 | #error please implement for this limb size. | |
307 | #endif | |
654842ef | 308 | if (lzeros) { |
f2d1362f | 309 | y = lzeros; |
654842ef | 310 | lzeros = 0; |
2d4d1eea TS |
311 | } |
312 | ||
d7552906 | 313 | p = (u8 *)&alimb + y; |
2d4d1eea TS |
314 | |
315 | for (x = 0; x < sizeof(alimb) - y; x++) { | |
316 | if (!buf_len) { | |
317 | sgl = sg_next(sgl); | |
318 | if (!sgl) | |
319 | return -EINVAL; | |
320 | buf_len = sgl->length; | |
321 | p2 = sg_virt(sgl); | |
322 | } | |
323 | *p2++ = *p++; | |
324 | buf_len--; | |
325 | } | |
326 | y = 0; | |
327 | } | |
328 | return 0; | |
329 | } | |
330 | EXPORT_SYMBOL_GPL(mpi_write_to_sgl); | |
331 | ||
332 | /* | |
333 | * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with | |
334 | * data from the sgl | |
335 | * | |
336 | * This function works in the same way as the mpi_read_raw_data, but it | |
337 | * takes an sgl instead of void * buffer. i.e. it allocates | |
338 | * a new MPI and reads the content of the sgl to the MPI. | |
339 | * | |
340 | * @sgl: scatterlist to read from | |
b6985389 | 341 | * @nbytes: number of bytes to read |
2d4d1eea TS |
342 | * |
343 | * Return: Pointer to a new MPI or NULL on error | |
344 | */ | |
b6985389 | 345 | MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes) |
2d4d1eea TS |
346 | { |
347 | struct scatterlist *sg; | |
348 | int x, i, j, z, lzeros, ents; | |
b6985389 | 349 | unsigned int nbits, nlimbs; |
2d4d1eea TS |
350 | mpi_limb_t a; |
351 | MPI val = NULL; | |
352 | ||
353 | lzeros = 0; | |
354 | ents = sg_nents(sgl); | |
355 | ||
356 | for_each_sg(sgl, sg, ents, i) { | |
357 | const u8 *buff = sg_virt(sg); | |
358 | int len = sg->length; | |
359 | ||
63349d02 | 360 | while (len && !*buff) { |
2d4d1eea | 361 | lzeros++; |
63349d02 SM |
362 | len--; |
363 | buff++; | |
364 | } | |
2d4d1eea TS |
365 | |
366 | if (len && *buff) | |
367 | break; | |
368 | ||
369 | ents--; | |
ab1e912e | 370 | nbytes -= lzeros; |
2d4d1eea TS |
371 | lzeros = 0; |
372 | } | |
373 | ||
374 | sgl = sg; | |
ab1e912e | 375 | nbytes -= lzeros; |
2d4d1eea TS |
376 | nbits = nbytes * 8; |
377 | if (nbits > MAX_EXTERN_MPI_BITS) { | |
378 | pr_info("MPI: mpi too large (%u bits)\n", nbits); | |
379 | return NULL; | |
380 | } | |
381 | ||
382 | if (nbytes > 0) | |
64c09b0b NS |
383 | nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros)) - |
384 | (BITS_PER_LONG - 8); | |
2d4d1eea TS |
385 | |
386 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); | |
387 | val = mpi_alloc(nlimbs); | |
388 | if (!val) | |
389 | return NULL; | |
390 | ||
391 | val->nbits = nbits; | |
392 | val->sign = 0; | |
393 | val->nlimbs = nlimbs; | |
394 | ||
395 | if (nbytes == 0) | |
396 | return val; | |
397 | ||
398 | j = nlimbs - 1; | |
399 | a = 0; | |
85d541a3 NS |
400 | z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; |
401 | z %= BYTES_PER_MPI_LIMB; | |
2d4d1eea TS |
402 | |
403 | for_each_sg(sgl, sg, ents, i) { | |
404 | const u8 *buffer = sg_virt(sg) + lzeros; | |
405 | int len = sg->length - lzeros; | |
2d4d1eea | 406 | |
85d541a3 | 407 | for (x = 0; x < len; x++) { |
2d4d1eea TS |
408 | a <<= 8; |
409 | a |= *buffer++; | |
410 | if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) { | |
411 | val->d[j--] = a; | |
412 | a = 0; | |
413 | } | |
414 | } | |
415 | z += x; | |
2d4d1eea TS |
416 | lzeros = 0; |
417 | } | |
418 | return val; | |
419 | } | |
420 | EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl); |