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
);
261 for (i
= a
->nlimbs
- 1; i
>= 0; i
--) {
263 #if BYTES_PER_MPI_LIMB == 4
268 #elif BYTES_PER_MPI_LIMB == 8
278 #error please implement for this limb size.
282 /* this is sub-optimal but we need to do the shift operation
283 * because the caller has to free the returned buffer */
284 for (p
= buffer
; !*p
&& *nbytes
; p
++, --*nbytes
)
287 memmove(buffer
, p
, *nbytes
);
291 EXPORT_SYMBOL_GPL(mpi_get_buffer
);
294 * Use BUFFER to update MPI.
296 int mpi_set_buffer(MPI a
, const void *xbuffer
, unsigned nbytes
, int sign
)
298 const uint8_t *buffer
= xbuffer
, *p
;
303 nlimbs
= (nbytes
+ BYTES_PER_MPI_LIMB
- 1) / BYTES_PER_MPI_LIMB
;
304 if (RESIZE_IF_NEEDED(a
, nlimbs
) < 0)
308 for (i
= 0, p
= buffer
+ nbytes
- 1; p
>= buffer
+ BYTES_PER_MPI_LIMB
;) {
309 #if BYTES_PER_MPI_LIMB == 4
310 alimb
= (mpi_limb_t
) *p
--;
311 alimb
|= (mpi_limb_t
) *p
-- << 8;
312 alimb
|= (mpi_limb_t
) *p
-- << 16;
313 alimb
|= (mpi_limb_t
) *p
-- << 24;
314 #elif BYTES_PER_MPI_LIMB == 8
315 alimb
= (mpi_limb_t
) *p
--;
316 alimb
|= (mpi_limb_t
) *p
-- << 8;
317 alimb
|= (mpi_limb_t
) *p
-- << 16;
318 alimb
|= (mpi_limb_t
) *p
-- << 24;
319 alimb
|= (mpi_limb_t
) *p
-- << 32;
320 alimb
|= (mpi_limb_t
) *p
-- << 40;
321 alimb
|= (mpi_limb_t
) *p
-- << 48;
322 alimb
|= (mpi_limb_t
) *p
-- << 56;
324 #error please implement for this limb size.
329 #if BYTES_PER_MPI_LIMB == 4
332 alimb
|= (mpi_limb_t
) *p
-- << 8;
334 alimb
|= (mpi_limb_t
) *p
-- << 16;
336 alimb
|= (mpi_limb_t
) *p
-- << 24;
337 #elif BYTES_PER_MPI_LIMB == 8
338 alimb
= (mpi_limb_t
) *p
--;
340 alimb
|= (mpi_limb_t
) *p
-- << 8;
342 alimb
|= (mpi_limb_t
) *p
-- << 16;
344 alimb
|= (mpi_limb_t
) *p
-- << 24;
346 alimb
|= (mpi_limb_t
) *p
-- << 32;
348 alimb
|= (mpi_limb_t
) *p
-- << 40;
350 alimb
|= (mpi_limb_t
) *p
-- << 48;
352 alimb
|= (mpi_limb_t
) *p
-- << 56;
354 #error please implement for this limb size.
361 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i
,
367 EXPORT_SYMBOL_GPL(mpi_set_buffer
);