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
);
83 mpi_set_buffer(a
, frame
, nframe
, 0);
89 MPI
mpi_read_from_buffer(const void *xbuffer
, unsigned *ret_nread
)
91 const uint8_t *buffer
= xbuffer
;
93 unsigned nbits
, nbytes
, nlimbs
, nread
= 0;
99 nbits
= buffer
[0] << 8 | buffer
[1];
101 if (nbits
> MAX_EXTERN_MPI_BITS
) {
102 pr_info("MPI: mpi too large (%u bits)\n", nbits
);
108 nbytes
= (nbits
+ 7) / 8;
109 nlimbs
= (nbytes
+ BYTES_PER_MPI_LIMB
- 1) / BYTES_PER_MPI_LIMB
;
110 val
= mpi_alloc(nlimbs
);
113 i
= BYTES_PER_MPI_LIMB
- nbytes
% BYTES_PER_MPI_LIMB
;
114 i
%= BYTES_PER_MPI_LIMB
;
116 j
= val
->nlimbs
= nlimbs
;
120 for (; i
< BYTES_PER_MPI_LIMB
; i
++) {
121 if (++nread
> *ret_nread
) {
123 ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
138 EXPORT_SYMBOL_GPL(mpi_read_from_buffer
);
141 * Make an mpi from a character string.
143 int mpi_fromstr(MPI val
, const char *str
)
145 int hexmode
= 0, sign
= 0, prepend_zero
= 0, i
, j
, c
, c1
, c2
;
146 unsigned nbits
, nbytes
, nlimbs
;
153 if (*str
== '0' && str
[1] == 'x')
156 return -EINVAL
; /* other bases are not yet supported */
159 nbits
= strlen(str
) * 4;
162 nbytes
= (nbits
+ 7) / 8;
163 nlimbs
= (nbytes
+ BYTES_PER_MPI_LIMB
- 1) / BYTES_PER_MPI_LIMB
;
164 if (val
->alloced
< nlimbs
)
165 if (!mpi_resize(val
, nlimbs
))
167 i
= BYTES_PER_MPI_LIMB
- nbytes
% BYTES_PER_MPI_LIMB
;
168 i
%= BYTES_PER_MPI_LIMB
;
169 j
= val
->nlimbs
= nlimbs
;
173 for (; i
< BYTES_PER_MPI_LIMB
; i
++) {
182 if (c1
>= '0' && c1
<= '9')
184 else if (c1
>= 'a' && c1
<= 'f')
186 else if (c1
>= 'A' && c1
<= 'F')
193 if (c2
>= '0' && c2
<= '9')
195 else if (c2
>= 'a' && c2
<= 'f')
197 else if (c2
>= 'A' && c2
<= 'F')
213 EXPORT_SYMBOL_GPL(mpi_fromstr
);
216 * Special function to get the low 8 bytes from an mpi.
217 * This can be used as a keyid; KEYID is an 2 element array.
218 * Return the low 4 bytes.
220 u32
mpi_get_keyid(const MPI a
, u32
*keyid
)
222 #if BYTES_PER_MPI_LIMB == 4
224 keyid
[0] = a
->nlimbs
>= 2 ? a
->d
[1] : 0;
225 keyid
[1] = a
->nlimbs
>= 1 ? a
->d
[0] : 0;
227 return a
->nlimbs
>= 1 ? a
->d
[0] : 0;
228 #elif BYTES_PER_MPI_LIMB == 8
230 keyid
[0] = a
->nlimbs
? (u32
) (a
->d
[0] >> 32) : 0;
231 keyid
[1] = a
->nlimbs
? (u32
) (a
->d
[0] & 0xffffffff) : 0;
233 return a
->nlimbs
? (u32
) (a
->d
[0] & 0xffffffff) : 0;
235 #error Make this function work with other LIMB sizes
240 * Return an allocated buffer with the MPI (msb first).
241 * NBYTES receives the length of this buffer. Caller must free the
242 * return string (This function does return a 0 byte buffer with NBYTES
243 * set to zero if the value of A is zero. If sign is not NULL, it will
244 * be set to the sign of the A.
246 void *mpi_get_buffer(MPI a
, unsigned *nbytes
, int *sign
)
255 *nbytes
= n
= a
->nlimbs
* BYTES_PER_MPI_LIMB
;
257 n
++; /* avoid zero length allocation */
258 p
= buffer
= kmalloc(n
, GFP_KERNEL
);
262 for (i
= a
->nlimbs
- 1; i
>= 0; i
--) {
264 #if BYTES_PER_MPI_LIMB == 4
269 #elif BYTES_PER_MPI_LIMB == 8
279 #error please implement for this limb size.
283 /* this is sub-optimal but we need to do the shift operation
284 * because the caller has to free the returned buffer */
285 for (p
= buffer
; !*p
&& *nbytes
; p
++, --*nbytes
)
288 memmove(buffer
, p
, *nbytes
);
292 EXPORT_SYMBOL_GPL(mpi_get_buffer
);
295 * Use BUFFER to update MPI.
297 int mpi_set_buffer(MPI a
, const void *xbuffer
, unsigned nbytes
, int sign
)
299 const uint8_t *buffer
= xbuffer
, *p
;
304 nlimbs
= (nbytes
+ BYTES_PER_MPI_LIMB
- 1) / BYTES_PER_MPI_LIMB
;
305 if (RESIZE_IF_NEEDED(a
, nlimbs
) < 0)
309 for (i
= 0, p
= buffer
+ nbytes
- 1; p
>= buffer
+ BYTES_PER_MPI_LIMB
;) {
310 #if BYTES_PER_MPI_LIMB == 4
311 alimb
= (mpi_limb_t
) *p
--;
312 alimb
|= (mpi_limb_t
) *p
-- << 8;
313 alimb
|= (mpi_limb_t
) *p
-- << 16;
314 alimb
|= (mpi_limb_t
) *p
-- << 24;
315 #elif BYTES_PER_MPI_LIMB == 8
316 alimb
= (mpi_limb_t
) *p
--;
317 alimb
|= (mpi_limb_t
) *p
-- << 8;
318 alimb
|= (mpi_limb_t
) *p
-- << 16;
319 alimb
|= (mpi_limb_t
) *p
-- << 24;
320 alimb
|= (mpi_limb_t
) *p
-- << 32;
321 alimb
|= (mpi_limb_t
) *p
-- << 40;
322 alimb
|= (mpi_limb_t
) *p
-- << 48;
323 alimb
|= (mpi_limb_t
) *p
-- << 56;
325 #error please implement for this limb size.
330 #if BYTES_PER_MPI_LIMB == 4
333 alimb
|= (mpi_limb_t
) *p
-- << 8;
335 alimb
|= (mpi_limb_t
) *p
-- << 16;
337 alimb
|= (mpi_limb_t
) *p
-- << 24;
338 #elif BYTES_PER_MPI_LIMB == 8
339 alimb
= (mpi_limb_t
) *p
--;
341 alimb
|= (mpi_limb_t
) *p
-- << 8;
343 alimb
|= (mpi_limb_t
) *p
-- << 16;
345 alimb
|= (mpi_limb_t
) *p
-- << 24;
347 alimb
|= (mpi_limb_t
) *p
-- << 32;
349 alimb
|= (mpi_limb_t
) *p
-- << 40;
351 alimb
|= (mpi_limb_t
) *p
-- << 48;
353 alimb
|= (mpi_limb_t
) *p
-- << 56;
355 #error please implement for this limb size.
362 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i
,
368 EXPORT_SYMBOL_GPL(mpi_set_buffer
);
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