1 /* mpicoder.c - Coder for the external representation of MPIs
2 * Copyright (C) 1998, 1999 Free Software Foundation, Inc.
4 * This file is part of GnuPG.
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.
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.
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
21 #include "mpi-internal.h"
23 #define DIM(v) (sizeof(v)/sizeof((v)[0]))
24 #define MAX_EXTERN_MPI_BITS 16384
26 static uint8_t asn[15] = /* Object ID is 1.3.14.3.2.26 */
27 { 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03,
28 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14
31 MPI do_encode_md(const void *sha_buffer, unsigned nbits)
33 int nframe = (nbits + 7) / 8;
34 uint8_t *frame, *fr_pt;
36 size_t asnlen = DIM(asn);
39 if (SHA1_DIGEST_LENGTH + asnlen + 4 > nframe)
40 pr_info("MPI: can't encode a %d bit MD into a %d bits frame\n",
41 (int)(SHA1_DIGEST_LENGTH * 8), (int)nbits);
43 /* We encode the MD in this way:
45 * 0 A PAD(n bytes) 0 ASN(asnlen bytes) MD(len bytes)
47 * PAD consists of FF bytes.
49 frame = kmalloc(nframe, GFP_KERNEL);
54 frame[n++] = 1; /* block type */
55 i = nframe - SHA1_DIGEST_LENGTH - asnlen - 3;
58 pr_info("MPI: message digest encoding failed\n");
63 memset(frame + n, 0xff, i);
66 memcpy(frame + n, &asn, asnlen);
68 memcpy(frame + n, sha_buffer, SHA1_DIGEST_LENGTH);
69 n += SHA1_DIGEST_LENGTH;
76 ("MPI: message digest encoding failed, frame length is wrong\n");
81 a = mpi_alloc((nframe + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB);
82 mpi_set_buffer(a, frame, nframe, 0);
88 MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
90 const uint8_t *buffer = xbuffer;
92 unsigned nbits, nbytes, nlimbs, nread = 0;
98 nbits = buffer[0] << 8 | buffer[1];
100 if (nbits > MAX_EXTERN_MPI_BITS) {
101 pr_info("MPI: mpi too large (%u bits)\n", nbits);
107 nbytes = (nbits + 7) / 8;
108 nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
109 val = mpi_alloc(nlimbs);
112 i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
113 i %= BYTES_PER_MPI_LIMB;
115 j = val->nlimbs = nlimbs;
119 for (; i < BYTES_PER_MPI_LIMB; i++) {
120 if (++nread > *ret_nread) {
122 ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
137 EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
140 * Make an mpi from a character string.
142 int mpi_fromstr(MPI val, const char *str)
144 int hexmode = 0, sign = 0, prepend_zero = 0, i, j, c, c1, c2;
145 unsigned nbits, nbytes, nlimbs;
152 if (*str == '0' && str[1] == 'x')
155 return -EINVAL; /* other bases are not yet supported */
158 nbits = strlen(str) * 4;
161 nbytes = (nbits + 7) / 8;
162 nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
163 if (val->alloced < nlimbs)
164 if (!mpi_resize(val, nlimbs))
166 i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
167 i %= BYTES_PER_MPI_LIMB;
168 j = val->nlimbs = nlimbs;
172 for (; i < BYTES_PER_MPI_LIMB; i++) {
181 if (c1 >= '0' && c1 <= '9')
183 else if (c1 >= 'a' && c1 <= 'f')
185 else if (c1 >= 'A' && c1 <= 'F')
192 if (c2 >= '0' && c2 <= '9')
194 else if (c2 >= 'a' && c2 <= 'f')
196 else if (c2 >= 'A' && c2 <= 'F')
212 EXPORT_SYMBOL_GPL(mpi_fromstr);
215 * Special function to get the low 8 bytes from an mpi.
216 * This can be used as a keyid; KEYID is an 2 element array.
217 * Return the low 4 bytes.
219 u32 mpi_get_keyid(const MPI a, u32 *keyid)
221 #if BYTES_PER_MPI_LIMB == 4
223 keyid[0] = a->nlimbs >= 2 ? a->d[1] : 0;
224 keyid[1] = a->nlimbs >= 1 ? a->d[0] : 0;
226 return a->nlimbs >= 1 ? a->d[0] : 0;
227 #elif BYTES_PER_MPI_LIMB == 8
229 keyid[0] = a->nlimbs ? (u32) (a->d[0] >> 32) : 0;
230 keyid[1] = a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
232 return a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
234 #error Make this function work with other LIMB sizes
239 * Return an allocated buffer with the MPI (msb first).
240 * NBYTES receives the length of this buffer. Caller must free the
241 * return string (This function does return a 0 byte buffer with NBYTES
242 * set to zero if the value of A is zero. If sign is not NULL, it will
243 * be set to the sign of the A.
245 void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
254 *nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
256 n++; /* avoid zero length allocation */
257 p = buffer = kmalloc(n, GFP_KERNEL);
259 for (i = a->nlimbs - 1; i >= 0; i--) {
261 #if BYTES_PER_MPI_LIMB == 4
266 #elif BYTES_PER_MPI_LIMB == 8
276 #error please implement for this limb size.
280 /* this is sub-optimal but we need to do the shift operation
281 * because the caller has to free the returned buffer */
282 for (p = buffer; !*p && *nbytes; p++, --*nbytes)
285 memmove(buffer, p, *nbytes);
289 EXPORT_SYMBOL_GPL(mpi_get_buffer);
292 * Use BUFFER to update MPI.
294 int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
296 const uint8_t *buffer = xbuffer, *p;
301 nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
302 if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
306 for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
307 #if BYTES_PER_MPI_LIMB == 4
308 alimb = (mpi_limb_t) *p--;
309 alimb |= (mpi_limb_t) *p-- << 8;
310 alimb |= (mpi_limb_t) *p-- << 16;
311 alimb |= (mpi_limb_t) *p-- << 24;
312 #elif BYTES_PER_MPI_LIMB == 8
313 alimb = (mpi_limb_t) *p--;
314 alimb |= (mpi_limb_t) *p-- << 8;
315 alimb |= (mpi_limb_t) *p-- << 16;
316 alimb |= (mpi_limb_t) *p-- << 24;
317 alimb |= (mpi_limb_t) *p-- << 32;
318 alimb |= (mpi_limb_t) *p-- << 40;
319 alimb |= (mpi_limb_t) *p-- << 48;
320 alimb |= (mpi_limb_t) *p-- << 56;
322 #error please implement for this limb size.
327 #if BYTES_PER_MPI_LIMB == 4
330 alimb |= (mpi_limb_t) *p-- << 8;
332 alimb |= (mpi_limb_t) *p-- << 16;
334 alimb |= (mpi_limb_t) *p-- << 24;
335 #elif BYTES_PER_MPI_LIMB == 8
336 alimb = (mpi_limb_t) *p--;
338 alimb |= (mpi_limb_t) *p-- << 8;
340 alimb |= (mpi_limb_t) *p-- << 16;
342 alimb |= (mpi_limb_t) *p-- << 24;
344 alimb |= (mpi_limb_t) *p-- << 32;
346 alimb |= (mpi_limb_t) *p-- << 40;
348 alimb |= (mpi_limb_t) *p-- << 48;
350 alimb |= (mpi_limb_t) *p-- << 56;
352 #error please implement for this limb size.
359 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
365 EXPORT_SYMBOL_GPL(mpi_set_buffer);