projects/linux·blob v4.2 · refs

309 lines · 7.1 KiB

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 <asm-generic/bitops/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
131/**
132 * mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
133 *
134 * @a: a multi precision integer
135 * @buf: bufer to which the output will be written to. Needs to be at
136 * leaset mpi_get_size(a) long.
137 * @buf_len: size of the buf.
138 * @nbytes: receives the actual length of the data written.
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
142 */
143int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
144 int *sign)
145{
146 uint8_t *p;
147 mpi_limb_t alimb;
148 unsigned int n = mpi_get_size(a);
149 int i;
150
151 if (buf_len < n || !buf)
152 return -EINVAL;
153
154 if (sign)
155 *sign = a->sign;
156
157 if (nbytes)
158 *nbytes = n;
159
160 p = buf;
161
162 for (i = a->nlimbs - 1; i >= 0; i--) {
163 alimb = a->d[i];
164#if BYTES_PER_MPI_LIMB == 4
165 *p++ = alimb >> 24;
166 *p++ = alimb >> 16;
167 *p++ = alimb >> 8;
168 *p++ = alimb;
169#elif BYTES_PER_MPI_LIMB == 8
170 *p++ = alimb >> 56;
171 *p++ = alimb >> 48;
172 *p++ = alimb >> 40;
173 *p++ = alimb >> 32;
174 *p++ = alimb >> 24;
175 *p++ = alimb >> 16;
176 *p++ = alimb >> 8;
177 *p++ = alimb;
178#else
179#error please implement for this limb size.
180#endif
181 }
182 return 0;
183}
184EXPORT_SYMBOL_GPL(mpi_read_buffer);
185
186/*
187 * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
188 * Caller must free the return string.
189 * This function does return a 0 byte buffer with nbytes set to zero if the
190 * value of A is zero.
191 *
192 * @a: a multi precision integer.
193 * @nbytes: receives the length of this buffer.
194 * @sign: if not NULL, it will be set to the sign of the a.
195 *
196 * Return: Pointer to MPI buffer or NULL on error
197 */
198void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
199{
200 uint8_t *buf, *p;
201 unsigned int n;
202 int ret;
203
204 if (!nbytes)
205 return NULL;
206
207 n = mpi_get_size(a);
208
209 if (!n)
210 n++;
211
212 buf = kmalloc(n, GFP_KERNEL);
213
214 if (!buf)
215 return NULL;
216
217 ret = mpi_read_buffer(a, buf, n, nbytes, sign);
218
219 if (ret) {
220 kfree(buf);
221 return NULL;
222 }
223
224 /* this is sub-optimal but we need to do the shift operation
225 * because the caller has to free the returned buffer */
226 for (p = buf; !*p && *nbytes; p++, --*nbytes)
227 ;
228 if (p != buf)
229 memmove(buf, p, *nbytes);
230
231 return buf;
232}
233EXPORT_SYMBOL_GPL(mpi_get_buffer);
234
235/****************
236 * Use BUFFER to update MPI.
237 */
238int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
239{
240 const uint8_t *buffer = xbuffer, *p;
241 mpi_limb_t alimb;
242 int nlimbs;
243 int i;
244
245 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
246 if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
247 return -ENOMEM;
248 a->sign = sign;
249
250 for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
251#if BYTES_PER_MPI_LIMB == 4
252 alimb = (mpi_limb_t) *p--;
253 alimb |= (mpi_limb_t) *p-- << 8;
254 alimb |= (mpi_limb_t) *p-- << 16;
255 alimb |= (mpi_limb_t) *p-- << 24;
256#elif BYTES_PER_MPI_LIMB == 8
257 alimb = (mpi_limb_t) *p--;
258 alimb |= (mpi_limb_t) *p-- << 8;
259 alimb |= (mpi_limb_t) *p-- << 16;
260 alimb |= (mpi_limb_t) *p-- << 24;
261 alimb |= (mpi_limb_t) *p-- << 32;
262 alimb |= (mpi_limb_t) *p-- << 40;
263 alimb |= (mpi_limb_t) *p-- << 48;
264 alimb |= (mpi_limb_t) *p-- << 56;
265#else
266#error please implement for this limb size.
267#endif
268 a->d[i++] = alimb;
269 }
270 if (p >= buffer) {
271#if BYTES_PER_MPI_LIMB == 4
272 alimb = *p--;
273 if (p >= buffer)
274 alimb |= (mpi_limb_t) *p-- << 8;
275 if (p >= buffer)
276 alimb |= (mpi_limb_t) *p-- << 16;
277 if (p >= buffer)
278 alimb |= (mpi_limb_t) *p-- << 24;
279#elif BYTES_PER_MPI_LIMB == 8
280 alimb = (mpi_limb_t) *p--;
281 if (p >= buffer)
282 alimb |= (mpi_limb_t) *p-- << 8;
283 if (p >= buffer)
284 alimb |= (mpi_limb_t) *p-- << 16;
285 if (p >= buffer)
286 alimb |= (mpi_limb_t) *p-- << 24;
287 if (p >= buffer)
288 alimb |= (mpi_limb_t) *p-- << 32;
289 if (p >= buffer)
290 alimb |= (mpi_limb_t) *p-- << 40;
291 if (p >= buffer)
292 alimb |= (mpi_limb_t) *p-- << 48;
293 if (p >= buffer)
294 alimb |= (mpi_limb_t) *p-- << 56;
295#else
296#error please implement for this limb size.
297#endif
298 a->d[i++] = alimb;
299 }
300 a->nlimbs = i;
301
302 if (i != nlimbs) {
303 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
304 nlimbs);
305 BUG();
306 }
307 return 0;
308}
309EXPORT_SYMBOL_GPL(mpi_set_buffer);