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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 DH |
21 | #include <linux/bitops.h> |
22 | #include <asm-generic/bitops/count_zeros.h> | |
cdec9cb5 DK |
23 | #include "mpi-internal.h" |
24 | ||
cdec9cb5 DK |
25 | #define MAX_EXTERN_MPI_BITS 16384 |
26 | ||
e1045992 DH |
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 | */ | |
32 | MPI 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 | ||
5402b804 | 40 | while (nbytes > 0 && buffer[0] == 0) { |
e1045992 DH |
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 | ||
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; | |
84 | unsigned nbits, nbytes, nlimbs, nread = 0; | |
85 | mpi_limb_t a; | |
3cccd154 | 86 | MPI val = NULL; |
cdec9cb5 DK |
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 | ||
0d2a1b2d AS |
99 | nbytes = DIV_ROUND_UP(nbits, 8); |
100 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); | |
cdec9cb5 DK |
101 | val = mpi_alloc(nlimbs); |
102 | if (!val) | |
3cccd154 | 103 | return NULL; |
cdec9cb5 DK |
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 | ||
125 | leave: | |
126 | *ret_nread = nread; | |
127 | return val; | |
128 | } | |
129 | EXPORT_SYMBOL_GPL(mpi_read_from_buffer); | |
130 | ||
d37e2969 TS |
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 | |
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; |
cdec9cb5 | 147 | mpi_limb_t alimb; |
d37e2969 | 148 | unsigned int n = mpi_get_size(a); |
cdec9cb5 | 149 | int i; |
d37e2969 TS |
150 | |
151 | if (buf_len < n || !buf) | |
152 | return -EINVAL; | |
cdec9cb5 DK |
153 | |
154 | if (sign) | |
155 | *sign = a->sign; | |
d37e2969 TS |
156 | |
157 | if (nbytes) | |
158 | *nbytes = n; | |
159 | ||
160 | p = buf; | |
cdec9cb5 DK |
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 | } | |
d37e2969 TS |
182 | return 0; |
183 | } | |
184 | EXPORT_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 | */ | |
198 | void *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 | } | |
cdec9cb5 DK |
223 | |
224 | /* this is sub-optimal but we need to do the shift operation | |
225 | * because the caller has to free the returned buffer */ | |
d37e2969 | 226 | for (p = buf; !*p && *nbytes; p++, --*nbytes) |
cdec9cb5 | 227 | ; |
d37e2969 TS |
228 | if (p != buf) |
229 | memmove(buf, p, *nbytes); | |
cdec9cb5 | 230 | |
d37e2969 | 231 | return buf; |
cdec9cb5 DK |
232 | } |
233 | EXPORT_SYMBOL_GPL(mpi_get_buffer); | |
234 | ||
235 | /**************** | |
236 | * Use BUFFER to update MPI. | |
237 | */ | |
238 | int 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 | ||
0d2a1b2d | 245 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); |
cdec9cb5 DK |
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 | } | |
309 | EXPORT_SYMBOL_GPL(mpi_set_buffer); |