/* mpicoder.c - Coder for the external representation of MPIs
* Copyright (C) 1998, 1999 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
* GnuPG is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* GnuPG is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include "mpi-internal.h"
#define DIM(v) (sizeof(v)/sizeof((v)[0]))
#define MAX_EXTERN_MPI_BITS 16384
static uint8_t asn[15] = /* Object ID is 1.3.14.3.2.26 */
{ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03,
0x02, 0x1a, 0x05, 0x00, 0x04, 0x14
};
MPI do_encode_md(const void *sha_buffer, unsigned nbits)
{
int nframe = (nbits + 7) / 8;
uint8_t *frame, *fr_pt;
int i = 0, n;
size_t asnlen = DIM(asn);
MPI a = MPI_NULL;
if (SHA1_DIGEST_LENGTH + asnlen + 4 > nframe)
pr_info("MPI: can't encode a %d bit MD into a %d bits frame\n",
(int)(SHA1_DIGEST_LENGTH * 8), (int)nbits);
/* We encode the MD in this way:
*
* 0 A PAD(n bytes) 0 ASN(asnlen bytes) MD(len bytes)
*
* PAD consists of FF bytes.
*/
frame = kmalloc(nframe, GFP_KERNEL);
if (!frame)
return MPI_NULL;
n = 0;
frame[n++] = 0;
frame[n++] = 1; /* block type */
i = nframe - SHA1_DIGEST_LENGTH - asnlen - 3;
if (i <= 1) {
pr_info("MPI: message digest encoding failed\n");
kfree(frame);
return a;
}
memset(frame + n, 0xff, i);
n += i;
frame[n++] = 0;
memcpy(frame + n, &asn, asnlen);
n += asnlen;
memcpy(frame + n, sha_buffer, SHA1_DIGEST_LENGTH);
n += SHA1_DIGEST_LENGTH;
i = nframe;
fr_pt = frame;
if (n != nframe) {
printk
("MPI: message digest encoding failed, frame length is wrong\n");
kfree(frame);
return a;
}
a = mpi_alloc((nframe + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB);
mpi_set_buffer(a, frame, nframe, 0);
kfree(frame);
return a;
}
MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
{
const uint8_t *buffer = xbuffer;
int i, j;
unsigned nbits, nbytes, nlimbs, nread = 0;
mpi_limb_t a;
MPI val = MPI_NULL;
if (*ret_nread < 2)
goto leave;
nbits = buffer[0] << 8 | buffer[1];
if (nbits > MAX_EXTERN_MPI_BITS) {
pr_info("MPI: mpi too large (%u bits)\n", nbits);
goto leave;
}
buffer += 2;
nread = 2;
nbytes = (nbits + 7) / 8;
nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
val = mpi_alloc(nlimbs);
if (!val)
return MPI_NULL;
i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
i %= BYTES_PER_MPI_LIMB;
val->nbits = nbits;
j = val->nlimbs = nlimbs;
val->sign = 0;
for (; j > 0; j--) {
a = 0;
for (; i < BYTES_PER_MPI_LIMB; i++) {
if (++nread > *ret_nread) {
printk
("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
nread, *ret_nread);
goto leave;
}
a <<= 8;
a |= *buffer++;
}
i = 0;
val->d[j - 1] = a;
}
leave:
*ret_nread = nread;
return val;
}
EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
/****************
* Make an mpi from a character string.
*/
int mpi_fromstr(MPI val, const char *str)
{
int hexmode = 0, sign = 0, prepend_zero = 0, i, j, c, c1, c2;
unsigned nbits, nbytes, nlimbs;
mpi_limb_t a;
if (*str == '-') {
sign = 1;
str++;
}
if (*str == '0' && str[1] == 'x')
hexmode = 1;
else
return -EINVAL; /* other bases are not yet supported */
str += 2;
nbits = strlen(str) * 4;
if (nbits % 8)
prepend_zero = 1;
nbytes = (nbits + 7) / 8;
nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
if (val->alloced < nlimbs)
if (!mpi_resize(val, nlimbs))
return -ENOMEM;
i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
i %= BYTES_PER_MPI_LIMB;
j = val->nlimbs = nlimbs;
val->sign = sign;
for (; j > 0; j--) {
a = 0;
for (; i < BYTES_PER_MPI_LIMB; i++) {
if (prepend_zero) {
c1 = '0';
prepend_zero = 0;
} else
c1 = *str++;
assert(c1);
c2 = *str++;
assert(c2);
if (c1 >= '0' && c1 <= '9')
c = c1 - '0';
else if (c1 >= 'a' && c1 <= 'f')
c = c1 - 'a' + 10;
else if (c1 >= 'A' && c1 <= 'F')
c = c1 - 'A' + 10;
else {
mpi_clear(val);
return 1;
}
c <<= 4;
if (c2 >= '0' && c2 <= '9')
c |= c2 - '0';
else if (c2 >= 'a' && c2 <= 'f')
c |= c2 - 'a' + 10;
else if (c2 >= 'A' && c2 <= 'F')
c |= c2 - 'A' + 10;
else {
mpi_clear(val);
return 1;
}
a <<= 8;
a |= c;
}
i = 0;
val->d[j - 1] = a;
}
return 0;
}
EXPORT_SYMBOL_GPL(mpi_fromstr);
/****************
* Special function to get the low 8 bytes from an mpi.
* This can be used as a keyid; KEYID is an 2 element array.
* Return the low 4 bytes.
*/
u32 mpi_get_keyid(const MPI a, u32 *keyid)
{
#if BYTES_PER_MPI_LIMB == 4
if (keyid) {
keyid[0] = a->nlimbs >= 2 ? a->d[1] : 0;
keyid[1] = a->nlimbs >= 1 ? a->d[0] : 0;
}
return a->nlimbs >= 1 ? a->d[0] : 0;
#elif BYTES_PER_MPI_LIMB == 8
if (keyid) {
keyid[0] = a->nlimbs ? (u32) (a->d[0] >> 32) : 0;
keyid[1] = a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
}
return a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
#else
#error Make this function work with other LIMB sizes
#endif
}
/****************
* Return an allocated buffer with the MPI (msb first).
* NBYTES receives the length of this buffer. Caller must free the
* return string (This function does return a 0 byte buffer with NBYTES
* set to zero if the value of A is zero. If sign is not NULL, it will
* be set to the sign of the A.
*/
void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
{
uint8_t *p, *buffer;
mpi_limb_t alimb;
int i;
unsigned int n;
if (sign)
*sign = a->sign;
*nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
if (!n)
n++; /* avoid zero length allocation */
p = buffer = kmalloc(n, GFP_KERNEL);
for (i = a->nlimbs - 1; i >= 0; i--) {
alimb = a->d[i];
#if BYTES_PER_MPI_LIMB == 4
*p++ = alimb >> 24;
*p++ = alimb >> 16;
*p++ = alimb >> 8;
*p++ = alimb;
#elif BYTES_PER_MPI_LIMB == 8
*p++ = alimb >> 56;
*p++ = alimb >> 48;
*p++ = alimb >> 40;
*p++ = alimb >> 32;
*p++ = alimb >> 24;
*p++ = alimb >> 16;
*p++ = alimb >> 8;
*p++ = alimb;
#else
#error please implement for this limb size.
#endif
}
/* this is sub-optimal but we need to do the shift operation
* because the caller has to free the returned buffer */
for (p = buffer; !*p && *nbytes; p++, --*nbytes)
;
if (p != buffer)
memmove(buffer, p, *nbytes);
return buffer;
}
EXPORT_SYMBOL_GPL(mpi_get_buffer);
/****************
* Use BUFFER to update MPI.
*/
int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
{
const uint8_t *buffer = xbuffer, *p;
mpi_limb_t alimb;
int nlimbs;
int i;
nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
return -ENOMEM;
a->sign = sign;
for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
#if BYTES_PER_MPI_LIMB == 4
alimb = (mpi_limb_t) *p--;
alimb |= (mpi_limb_t) *p-- << 8;
alimb |= (mpi_limb_t) *p-- << 16;
alimb |= (mpi_limb_t) *p-- << 24;
#elif BYTES_PER_MPI_LIMB == 8
alimb = (mpi_limb_t) *p--;
alimb |= (mpi_limb_t) *p-- << 8;
alimb |= (mpi_limb_t) *p-- << 16;
alimb |= (mpi_limb_t) *p-- << 24;
alimb |= (mpi_limb_t) *p-- << 32;
alimb |= (mpi_limb_t) *p-- << 40;
alimb |= (mpi_limb_t) *p-- << 48;
alimb |= (mpi_limb_t) *p-- << 56;
#else
#error please implement for this limb size.
#endif
a->d[i++] = alimb;
}
if (p >= buffer) {
#if BYTES_PER_MPI_LIMB == 4
alimb = *p--;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 8;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 16;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 24;
#elif BYTES_PER_MPI_LIMB == 8
alimb = (mpi_limb_t) *p--;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 8;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 16;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 24;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 32;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 40;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 48;
if (p >= buffer)
alimb |= (mpi_limb_t) *p-- << 56;
#else
#error please implement for this limb size.
#endif
a->d[i++] = alimb;
}
a->nlimbs = i;
if (i != nlimbs) {
pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
nlimbs);
BUG();
}
return 0;
}
EXPORT_SYMBOL_GPL(mpi_set_buffer);
