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Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +03001/* 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
David Howellse1045992012-09-24 17:11:27 +010021#include <linux/bitops.h>
Christoph Hellwiga1164a32015-08-28 09:27:15 +020022#include <linux/count_zeros.h>
Nicolai Stanged7552902016-03-22 13:12:39 +010023#include <linux/byteorder/generic.h>
Herbert Xu127827b2016-06-29 19:32:22 +080024#include <linux/scatterlist.h>
Nicolai Stange90f864e2016-03-22 13:12:41 +010025#include <linux/string.h>
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +030026#include "mpi-internal.h"
27
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +030028#define MAX_EXTERN_MPI_BITS 16384
29
David Howellse1045992012-09-24 17:11:27 +010030/**
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 */
35MPI 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
Chen Gang5402b802013-06-12 14:04:40 -070043 while (nbytes > 0 && buffer[0] == 0) {
David Howellse1045992012-09-24 17:11:27 +010044 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)
Nicolai Stangeeef0df62016-05-26 13:05:32 +020054 nbits -= count_leading_zeros(buffer[0]) - (BITS_PER_LONG - 8);
David Howellse1045992012-09-24 17:11:27 +010055
Andy Shevchenko0d2a1b22013-01-30 11:30:06 +020056 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
David Howellse1045992012-09-24 17:11:27 +010057 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}
79EXPORT_SYMBOL_GPL(mpi_read_raw_data);
80
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +030081MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
82{
83 const uint8_t *buffer = xbuffer;
Nicolai Stange20b5b7f2016-05-26 23:19:55 +020084 unsigned int nbits, nbytes;
85 MPI val;
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +030086
87 if (*ret_nread < 2)
Nicolai Stange03cdfaa2016-05-26 23:19:51 +020088 return ERR_PTR(-EINVAL);
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +030089 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);
Nicolai Stange03cdfaa2016-05-26 23:19:51 +020093 return ERR_PTR(-EINVAL);
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +030094 }
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +030095
Andy Shevchenko0d2a1b22013-01-30 11:30:06 +020096 nbytes = DIV_ROUND_UP(nbits, 8);
Nicolai Stange7af791e2016-05-26 23:19:53 +020097 if (nbytes + 2 > *ret_nread) {
Nicolai Stangecdf24b42016-05-26 23:19:54 +020098 pr_info("MPI: mpi larger than buffer nbytes=%u ret_nread=%u\n",
99 nbytes, *ret_nread);
Nicolai Stange7af791e2016-05-26 23:19:53 +0200100 return ERR_PTR(-EINVAL);
101 }
102
Nicolai Stange20b5b7f2016-05-26 23:19:55 +0200103 val = mpi_read_raw_data(buffer + 2, nbytes);
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300104 if (!val)
Nicolai Stange03cdfaa2016-05-26 23:19:51 +0200105 return ERR_PTR(-ENOMEM);
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300106
Nicolai Stange7af791e2016-05-26 23:19:53 +0200107 *ret_nread = nbytes + 2;
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300108 return val;
109}
110EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
111
Michal Marek3ee0cb52016-02-17 14:46:59 +0100112static 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
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700129/**
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.
Andrzej Zaborowski9cbe21d2015-11-13 12:01:32 +0100136 * @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.
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700139 * @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
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300142 */
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700143int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
144 int *sign)
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300145{
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700146 uint8_t *p;
Nicolai Stange90f864e2016-03-22 13:12:41 +0100147#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
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700154 unsigned int n = mpi_get_size(a);
Michal Marek3ee0cb52016-02-17 14:46:59 +0100155 int i, lzeros;
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700156
Andrzej Zaborowski9cbe21d2015-11-13 12:01:32 +0100157 if (!buf || !nbytes)
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700158 return -EINVAL;
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300159
160 if (sign)
161 *sign = a->sign;
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700162
Michal Marek3ee0cb52016-02-17 14:46:59 +0100163 lzeros = count_lzeros(a);
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700164
Andrzej Zaborowski9cbe21d2015-11-13 12:01:32 +0100165 if (buf_len < n - lzeros) {
166 *nbytes = n - lzeros;
167 return -EOVERFLOW;
168 }
169
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700170 p = buf;
Tadeusz Struk0f74fbf2015-08-24 07:52:14 -0700171 *nbytes = n - lzeros;
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300172
Nicolai Stangef00fa242016-03-22 13:12:40 +0100173 for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
174 lzeros %= BYTES_PER_MPI_LIMB;
175 i >= 0; i--) {
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300176#if BYTES_PER_MPI_LIMB == 4
Nicolai Stange90f864e2016-03-22 13:12:41 +0100177 alimb = cpu_to_be32(a->d[i]);
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300178#elif BYTES_PER_MPI_LIMB == 8
Nicolai Stange90f864e2016-03-22 13:12:41 +0100179 alimb = cpu_to_be64(a->d[i]);
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300180#else
181#error please implement for this limb size.
182#endif
Nicolai Stange462696f2016-03-22 13:12:42 +0100183 memcpy(p, (u8 *)&alimb + lzeros, BYTES_PER_MPI_LIMB - lzeros);
184 p += BYTES_PER_MPI_LIMB - lzeros;
185 lzeros = 0;
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300186 }
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700187 return 0;
188}
189EXPORT_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 */
203void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
204{
Tadeusz Struk0f74fbf2015-08-24 07:52:14 -0700205 uint8_t *buf;
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700206 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 }
Tadeusz Strukd37e2962015-06-15 13:18:36 -0700228 return buf;
Dmitry Kasatkincdec9cb2011-08-31 14:05:16 +0300229}
230EXPORT_SYMBOL_GPL(mpi_get_buffer);
231
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700232/**
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.
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800241 * @nbytes: the number of bytes to write. Leading bytes will be
242 * filled with zero.
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700243 * @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 */
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800247int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned nbytes,
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700248 int *sign)
249{
250 u8 *p, *p2;
Nicolai Stanged7552902016-03-22 13:12:39 +0100251#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
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700258 unsigned int n = mpi_get_size(a);
Herbert Xu127827b2016-06-29 19:32:22 +0800259 struct sg_mapping_iter miter;
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800260 int i, x, buf_len;
Herbert Xu127827b2016-06-29 19:32:22 +0800261 int nents;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700262
263 if (sign)
264 *sign = a->sign;
265
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800266 if (nbytes < n)
Andrzej Zaborowski9cbe21d2015-11-13 12:01:32 +0100267 return -EOVERFLOW;
Andrzej Zaborowski9cbe21d2015-11-13 12:01:32 +0100268
Herbert Xu127827b2016-06-29 19:32:22 +0800269 nents = sg_nents_for_len(sgl, nbytes);
270 if (nents < 0)
271 return -EINVAL;
272
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;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700277
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800278 while (nbytes > n) {
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800279 i = min_t(unsigned, nbytes - n, buf_len);
280 memset(p2, 0, i);
281 p2 += i;
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800282 nbytes -= i;
Herbert Xu127827b2016-06-29 19:32:22 +0800283
284 buf_len -= i;
285 if (!buf_len) {
286 sg_miter_next(&miter);
287 buf_len = miter.length;
288 p2 = miter.addr;
289 }
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800290 }
291
292 for (i = a->nlimbs - 1; i >= 0; i--) {
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700293#if BYTES_PER_MPI_LIMB == 4
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800294 alimb = a->d[i] ? cpu_to_be32(a->d[i]) : 0;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700295#elif BYTES_PER_MPI_LIMB == 8
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800296 alimb = a->d[i] ? cpu_to_be64(a->d[i]) : 0;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700297#else
298#error please implement for this limb size.
299#endif
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800300 p = (u8 *)&alimb;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700301
Herbert Xu9b45b7b2016-06-29 19:32:21 +0800302 for (x = 0; x < sizeof(alimb); x++) {
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700303 *p2++ = *p++;
Herbert Xu127827b2016-06-29 19:32:22 +0800304 if (!--buf_len) {
305 sg_miter_next(&miter);
306 buf_len = miter.length;
307 p2 = miter.addr;
308 }
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700309 }
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700310 }
Herbert Xu127827b2016-06-29 19:32:22 +0800311
312 sg_miter_stop(&miter);
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700313 return 0;
314}
315EXPORT_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
Nicolai Stangeb6985382016-03-22 13:12:43 +0100326 * @nbytes: number of bytes to read
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700327 *
328 * Return: Pointer to a new MPI or NULL on error
329 */
Nicolai Stangeb6985382016-03-22 13:12:43 +0100330MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700331{
Herbert Xu127827b2016-06-29 19:32:22 +0800332 struct sg_mapping_iter miter;
Nicolai Stangeb6985382016-03-22 13:12:43 +0100333 unsigned int nbits, nlimbs;
Herbert Xu127827b2016-06-29 19:32:22 +0800334 int x, j, z, lzeros, ents;
335 unsigned int len;
336 const u8 *buff;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700337 mpi_limb_t a;
338 MPI val = NULL;
339
Herbert Xu127827b2016-06-29 19:32:22 +0800340 ents = sg_nents_for_len(sgl, nbytes);
341 if (ents < 0)
342 return NULL;
343
344 sg_miter_start(&miter, sgl, ents, SG_MITER_ATOMIC | SG_MITER_FROM_SG);
345
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700346 lzeros = 0;
Herbert Xu127827b2016-06-29 19:32:22 +0800347 len = 0;
348 while (nbytes > 0) {
Stephan Mueller63349d02015-10-18 12:45:18 +0200349 while (len && !*buff) {
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700350 lzeros++;
Stephan Mueller63349d02015-10-18 12:45:18 +0200351 len--;
352 buff++;
353 }
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700354
355 if (len && *buff)
356 break;
357
Herbert Xu127827b2016-06-29 19:32:22 +0800358 sg_miter_next(&miter);
359 buff = miter.addr;
360 len = miter.length;
361
Nicolai Stangeab1e9122016-03-22 13:12:44 +0100362 nbytes -= lzeros;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700363 lzeros = 0;
364 }
365
Herbert Xu4816c942016-07-28 13:29:17 +0800366 miter.consumed = lzeros;
367 sg_miter_stop(&miter);
368
Nicolai Stangeab1e9122016-03-22 13:12:44 +0100369 nbytes -= lzeros;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700370 nbits = nbytes * 8;
371 if (nbits > MAX_EXTERN_MPI_BITS) {
372 pr_info("MPI: mpi too large (%u bits)\n", nbits);
373 return NULL;
374 }
375
376 if (nbytes > 0)
Herbert Xu127827b2016-06-29 19:32:22 +0800377 nbits -= count_leading_zeros(*buff) - (BITS_PER_LONG - 8);
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700378
379 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
380 val = mpi_alloc(nlimbs);
381 if (!val)
382 return NULL;
383
384 val->nbits = nbits;
385 val->sign = 0;
386 val->nlimbs = nlimbs;
387
388 if (nbytes == 0)
389 return val;
390
391 j = nlimbs - 1;
392 a = 0;
Nicolai Stange85d541a2016-03-22 13:18:07 +0100393 z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
394 z %= BYTES_PER_MPI_LIMB;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700395
Herbert Xu4816c942016-07-28 13:29:17 +0800396 while (sg_miter_next(&miter)) {
397 buff = miter.addr;
398 len = miter.length;
399
Nicolai Stange85d541a2016-03-22 13:18:07 +0100400 for (x = 0; x < len; x++) {
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700401 a <<= 8;
Herbert Xu127827b2016-06-29 19:32:22 +0800402 a |= *buff++;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700403 if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
404 val->d[j--] = a;
405 a = 0;
406 }
407 }
408 z += x;
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700409 }
Herbert Xu127827b2016-06-29 19:32:22 +0800410
Tadeusz Struk2d4d1ee2015-10-08 09:26:50 -0700411 return val;
412}
413EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);