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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 "mpi-internal.h"
22
23#define MAX_EXTERN_MPI_BITS 16384
24
25MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
26{
27 const uint8_t *buffer = xbuffer;
28 int i, j;
29 unsigned nbits, nbytes, nlimbs, nread = 0;
30 mpi_limb_t a;
31 MPI val = NULL;
32
33 if (*ret_nread < 2)
34 goto leave;
35 nbits = buffer[0] << 8 | buffer[1];
36
37 if (nbits > MAX_EXTERN_MPI_BITS) {
38 pr_info("MPI: mpi too large (%u bits)\n", nbits);
39 goto leave;
40 }
41 buffer += 2;
42 nread = 2;
43
44 nbytes = (nbits + 7) / 8;
45 nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
46 val = mpi_alloc(nlimbs);
47 if (!val)
48 return NULL;
49 i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
50 i %= BYTES_PER_MPI_LIMB;
51 val->nbits = nbits;
52 j = val->nlimbs = nlimbs;
53 val->sign = 0;
54 for (; j > 0; j--) {
55 a = 0;
56 for (; i < BYTES_PER_MPI_LIMB; i++) {
57 if (++nread > *ret_nread) {
58 printk
59 ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
60 nread, *ret_nread);
61 goto leave;
62 }
63 a <<= 8;
64 a |= *buffer++;
65 }
66 i = 0;
67 val->d[j - 1] = a;
68 }
69
70leave:
71 *ret_nread = nread;
72 return val;
73}
74EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
75
76/****************
77 * Make an mpi from a character string.
78 */
79int mpi_fromstr(MPI val, const char *str)
80{
81 int hexmode = 0, sign = 0, prepend_zero = 0, i, j, c, c1, c2;
82 unsigned nbits, nbytes, nlimbs;
83 mpi_limb_t a;
84
85 if (*str == '-') {
86 sign = 1;
87 str++;
88 }
89 if (*str == '0' && str[1] == 'x')
90 hexmode = 1;
91 else
92 return -EINVAL; /* other bases are not yet supported */
93 str += 2;
94
95 nbits = strlen(str) * 4;
96 if (nbits % 8)
97 prepend_zero = 1;
98 nbytes = (nbits + 7) / 8;
99 nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
100 if (val->alloced < nlimbs)
101 if (!mpi_resize(val, nlimbs))
102 return -ENOMEM;
103 i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
104 i %= BYTES_PER_MPI_LIMB;
105 j = val->nlimbs = nlimbs;
106 val->sign = sign;
107 for (; j > 0; j--) {
108 a = 0;
109 for (; i < BYTES_PER_MPI_LIMB; i++) {
110 if (prepend_zero) {
111 c1 = '0';
112 prepend_zero = 0;
113 } else
114 c1 = *str++;
115 assert(c1);
116 c2 = *str++;
117 assert(c2);
118 if (c1 >= '0' && c1 <= '9')
119 c = c1 - '0';
120 else if (c1 >= 'a' && c1 <= 'f')
121 c = c1 - 'a' + 10;
122 else if (c1 >= 'A' && c1 <= 'F')
123 c = c1 - 'A' + 10;
124 else {
125 mpi_clear(val);
126 return 1;
127 }
128 c <<= 4;
129 if (c2 >= '0' && c2 <= '9')
130 c |= c2 - '0';
131 else if (c2 >= 'a' && c2 <= 'f')
132 c |= c2 - 'a' + 10;
133 else if (c2 >= 'A' && c2 <= 'F')
134 c |= c2 - 'A' + 10;
135 else {
136 mpi_clear(val);
137 return 1;
138 }
139 a <<= 8;
140 a |= c;
141 }
142 i = 0;
143
144 val->d[j - 1] = a;
145 }
146
147 return 0;
148}
149EXPORT_SYMBOL_GPL(mpi_fromstr);
150
151/****************
152 * Return an allocated buffer with the MPI (msb first).
153 * NBYTES receives the length of this buffer. Caller must free the
154 * return string (This function does return a 0 byte buffer with NBYTES
155 * set to zero if the value of A is zero. If sign is not NULL, it will
156 * be set to the sign of the A.
157 */
158void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
159{
160 uint8_t *p, *buffer;
161 mpi_limb_t alimb;
162 int i;
163 unsigned int n;
164
165 if (sign)
166 *sign = a->sign;
167 *nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
168 if (!n)
169 n++; /* avoid zero length allocation */
170 p = buffer = kmalloc(n, GFP_KERNEL);
171 if (!p)
172 return NULL;
173
174 for (i = a->nlimbs - 1; i >= 0; i--) {
175 alimb = a->d[i];
176#if BYTES_PER_MPI_LIMB == 4
177 *p++ = alimb >> 24;
178 *p++ = alimb >> 16;
179 *p++ = alimb >> 8;
180 *p++ = alimb;
181#elif BYTES_PER_MPI_LIMB == 8
182 *p++ = alimb >> 56;
183 *p++ = alimb >> 48;
184 *p++ = alimb >> 40;
185 *p++ = alimb >> 32;
186 *p++ = alimb >> 24;
187 *p++ = alimb >> 16;
188 *p++ = alimb >> 8;
189 *p++ = alimb;
190#else
191#error please implement for this limb size.
192#endif
193 }
194
195 /* this is sub-optimal but we need to do the shift operation
196 * because the caller has to free the returned buffer */
197 for (p = buffer; !*p && *nbytes; p++, --*nbytes)
198 ;
199 if (p != buffer)
200 memmove(buffer, p, *nbytes);
201
202 return buffer;
203}
204EXPORT_SYMBOL_GPL(mpi_get_buffer);
205
206/****************
207 * Use BUFFER to update MPI.
208 */
209int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
210{
211 const uint8_t *buffer = xbuffer, *p;
212 mpi_limb_t alimb;
213 int nlimbs;
214 int i;
215
216 nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
217 if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
218 return -ENOMEM;
219 a->sign = sign;
220
221 for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
222#if BYTES_PER_MPI_LIMB == 4
223 alimb = (mpi_limb_t) *p--;
224 alimb |= (mpi_limb_t) *p-- << 8;
225 alimb |= (mpi_limb_t) *p-- << 16;
226 alimb |= (mpi_limb_t) *p-- << 24;
227#elif BYTES_PER_MPI_LIMB == 8
228 alimb = (mpi_limb_t) *p--;
229 alimb |= (mpi_limb_t) *p-- << 8;
230 alimb |= (mpi_limb_t) *p-- << 16;
231 alimb |= (mpi_limb_t) *p-- << 24;
232 alimb |= (mpi_limb_t) *p-- << 32;
233 alimb |= (mpi_limb_t) *p-- << 40;
234 alimb |= (mpi_limb_t) *p-- << 48;
235 alimb |= (mpi_limb_t) *p-- << 56;
236#else
237#error please implement for this limb size.
238#endif
239 a->d[i++] = alimb;
240 }
241 if (p >= buffer) {
242#if BYTES_PER_MPI_LIMB == 4
243 alimb = *p--;
244 if (p >= buffer)
245 alimb |= (mpi_limb_t) *p-- << 8;
246 if (p >= buffer)
247 alimb |= (mpi_limb_t) *p-- << 16;
248 if (p >= buffer)
249 alimb |= (mpi_limb_t) *p-- << 24;
250#elif BYTES_PER_MPI_LIMB == 8
251 alimb = (mpi_limb_t) *p--;
252 if (p >= buffer)
253 alimb |= (mpi_limb_t) *p-- << 8;
254 if (p >= buffer)
255 alimb |= (mpi_limb_t) *p-- << 16;
256 if (p >= buffer)
257 alimb |= (mpi_limb_t) *p-- << 24;
258 if (p >= buffer)
259 alimb |= (mpi_limb_t) *p-- << 32;
260 if (p >= buffer)
261 alimb |= (mpi_limb_t) *p-- << 40;
262 if (p >= buffer)
263 alimb |= (mpi_limb_t) *p-- << 48;
264 if (p >= buffer)
265 alimb |= (mpi_limb_t) *p-- << 56;
266#else
267#error please implement for this limb size.
268#endif
269 a->d[i++] = alimb;
270 }
271 a->nlimbs = i;
272
273 if (i != nlimbs) {
274 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
275 nlimbs);
276 BUG();
277 }
278 return 0;
279}
280EXPORT_SYMBOL_GPL(mpi_set_buffer);