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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); |
0f74fbf7 | 149 | int i, lzeros = 0; |
d37e2969 | 150 | |
0f74fbf7 | 151 | if (buf_len < n || !buf || !nbytes) |
d37e2969 | 152 | return -EINVAL; |
cdec9cb5 DK |
153 | |
154 | if (sign) | |
155 | *sign = a->sign; | |
d37e2969 | 156 | |
0f74fbf7 TS |
157 | p = (void *)&a->d[a->nlimbs] - 1; |
158 | ||
159 | for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) { | |
160 | if (!*p) | |
161 | lzeros++; | |
162 | else | |
163 | break; | |
164 | } | |
d37e2969 TS |
165 | |
166 | p = buf; | |
0f74fbf7 | 167 | *nbytes = n - lzeros; |
cdec9cb5 DK |
168 | |
169 | for (i = a->nlimbs - 1; i >= 0; i--) { | |
170 | alimb = a->d[i]; | |
171 | #if BYTES_PER_MPI_LIMB == 4 | |
172 | *p++ = alimb >> 24; | |
173 | *p++ = alimb >> 16; | |
174 | *p++ = alimb >> 8; | |
175 | *p++ = alimb; | |
176 | #elif BYTES_PER_MPI_LIMB == 8 | |
177 | *p++ = alimb >> 56; | |
178 | *p++ = alimb >> 48; | |
179 | *p++ = alimb >> 40; | |
180 | *p++ = alimb >> 32; | |
181 | *p++ = alimb >> 24; | |
182 | *p++ = alimb >> 16; | |
183 | *p++ = alimb >> 8; | |
184 | *p++ = alimb; | |
185 | #else | |
186 | #error please implement for this limb size. | |
187 | #endif | |
0f74fbf7 TS |
188 | |
189 | if (lzeros > 0) { | |
190 | if (lzeros >= sizeof(alimb)) { | |
191 | p -= sizeof(alimb); | |
192 | } else { | |
193 | mpi_limb_t *limb1 = (void *)p - sizeof(alimb); | |
194 | mpi_limb_t *limb2 = (void *)p - sizeof(alimb) | |
195 | + lzeros; | |
196 | *limb1 = *limb2; | |
197 | p -= lzeros; | |
198 | } | |
199 | lzeros -= sizeof(alimb); | |
200 | } | |
cdec9cb5 | 201 | } |
d37e2969 TS |
202 | return 0; |
203 | } | |
204 | EXPORT_SYMBOL_GPL(mpi_read_buffer); | |
205 | ||
206 | /* | |
207 | * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first). | |
208 | * Caller must free the return string. | |
209 | * This function does return a 0 byte buffer with nbytes set to zero if the | |
210 | * value of A is zero. | |
211 | * | |
212 | * @a: a multi precision integer. | |
213 | * @nbytes: receives the length of this buffer. | |
214 | * @sign: if not NULL, it will be set to the sign of the a. | |
215 | * | |
216 | * Return: Pointer to MPI buffer or NULL on error | |
217 | */ | |
218 | void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign) | |
219 | { | |
0f74fbf7 | 220 | uint8_t *buf; |
d37e2969 TS |
221 | unsigned int n; |
222 | int ret; | |
223 | ||
224 | if (!nbytes) | |
225 | return NULL; | |
226 | ||
227 | n = mpi_get_size(a); | |
228 | ||
229 | if (!n) | |
230 | n++; | |
231 | ||
232 | buf = kmalloc(n, GFP_KERNEL); | |
233 | ||
234 | if (!buf) | |
235 | return NULL; | |
236 | ||
237 | ret = mpi_read_buffer(a, buf, n, nbytes, sign); | |
238 | ||
239 | if (ret) { | |
240 | kfree(buf); | |
241 | return NULL; | |
242 | } | |
d37e2969 | 243 | return buf; |
cdec9cb5 DK |
244 | } |
245 | EXPORT_SYMBOL_GPL(mpi_get_buffer); | |
246 | ||
247 | /**************** | |
248 | * Use BUFFER to update MPI. | |
249 | */ | |
250 | int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign) | |
251 | { | |
252 | const uint8_t *buffer = xbuffer, *p; | |
253 | mpi_limb_t alimb; | |
254 | int nlimbs; | |
255 | int i; | |
256 | ||
0d2a1b2d | 257 | nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); |
cdec9cb5 DK |
258 | if (RESIZE_IF_NEEDED(a, nlimbs) < 0) |
259 | return -ENOMEM; | |
260 | a->sign = sign; | |
261 | ||
262 | for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) { | |
263 | #if BYTES_PER_MPI_LIMB == 4 | |
264 | alimb = (mpi_limb_t) *p--; | |
265 | alimb |= (mpi_limb_t) *p-- << 8; | |
266 | alimb |= (mpi_limb_t) *p-- << 16; | |
267 | alimb |= (mpi_limb_t) *p-- << 24; | |
268 | #elif BYTES_PER_MPI_LIMB == 8 | |
269 | alimb = (mpi_limb_t) *p--; | |
270 | alimb |= (mpi_limb_t) *p-- << 8; | |
271 | alimb |= (mpi_limb_t) *p-- << 16; | |
272 | alimb |= (mpi_limb_t) *p-- << 24; | |
273 | alimb |= (mpi_limb_t) *p-- << 32; | |
274 | alimb |= (mpi_limb_t) *p-- << 40; | |
275 | alimb |= (mpi_limb_t) *p-- << 48; | |
276 | alimb |= (mpi_limb_t) *p-- << 56; | |
277 | #else | |
278 | #error please implement for this limb size. | |
279 | #endif | |
280 | a->d[i++] = alimb; | |
281 | } | |
282 | if (p >= buffer) { | |
283 | #if BYTES_PER_MPI_LIMB == 4 | |
284 | alimb = *p--; | |
285 | if (p >= buffer) | |
286 | alimb |= (mpi_limb_t) *p-- << 8; | |
287 | if (p >= buffer) | |
288 | alimb |= (mpi_limb_t) *p-- << 16; | |
289 | if (p >= buffer) | |
290 | alimb |= (mpi_limb_t) *p-- << 24; | |
291 | #elif BYTES_PER_MPI_LIMB == 8 | |
292 | alimb = (mpi_limb_t) *p--; | |
293 | if (p >= buffer) | |
294 | alimb |= (mpi_limb_t) *p-- << 8; | |
295 | if (p >= buffer) | |
296 | alimb |= (mpi_limb_t) *p-- << 16; | |
297 | if (p >= buffer) | |
298 | alimb |= (mpi_limb_t) *p-- << 24; | |
299 | if (p >= buffer) | |
300 | alimb |= (mpi_limb_t) *p-- << 32; | |
301 | if (p >= buffer) | |
302 | alimb |= (mpi_limb_t) *p-- << 40; | |
303 | if (p >= buffer) | |
304 | alimb |= (mpi_limb_t) *p-- << 48; | |
305 | if (p >= buffer) | |
306 | alimb |= (mpi_limb_t) *p-- << 56; | |
307 | #else | |
308 | #error please implement for this limb size. | |
309 | #endif | |
310 | a->d[i++] = alimb; | |
311 | } | |
312 | a->nlimbs = i; | |
313 | ||
314 | if (i != nlimbs) { | |
315 | pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i, | |
316 | nlimbs); | |
317 | BUG(); | |
318 | } | |
319 | return 0; | |
320 | } | |
321 | EXPORT_SYMBOL_GPL(mpi_set_buffer); |