Page MenuHome GnuPG
Files F18826748

mpicoder.c
No OneTemporary
Actions

mpicoder.c
View Options

/* mpicoder.c - Coder for the external representation of MPIs
* Copyright (C) 1998 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 <config.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include "mpi.h"
#include "mpi-internal.h"
#include "iobuf.h"
#include "memory.h"
#include "util.h"
#ifdef M_DEBUG
#undef mpi_read
#endif
#define MAX_EXTERN_MPI_BITS 16384
/****************
* write an mpi to out.
*/
int
mpi_write( IOBUF out, MPI a )
{
int rc;
unsigned nbits = mpi_get_nbits(a);
byte *p, *buf;
unsigned n;
if( nbits > MAX_EXTERN_MPI_BITS )
log_bug("mpi_encode: mpi too large (%u bits)\n", nbits);
iobuf_put(out, (nbits >>8) );
iobuf_put(out, (nbits) );
p = buf = mpi_get_buffer( a, &n, NULL );
rc = iobuf_write( out, p, n );
m_free(buf);
return rc;
}
/****************
* Read an external representation of an mpi and return the MPI
* The external format is a 16 bit unsigned value stored in network byte order,
* giving the number of bits for the following integer. The integer is stored
* with MSB first (left padded with zeroes to align on a byte boundary).
*/
MPI
#ifdef M_DEBUG
mpi_debug_read(IOBUF inp, unsigned *ret_nread, int secure, const char *info)
#else
mpi_read(IOBUF inp, unsigned *ret_nread, int secure)
#endif
{
int c, i, j;
unsigned nbits, nbytes, nlimbs, nread=0;
mpi_limb_t a;
MPI val = MPI_NULL;
if( (c = iobuf_get(inp)) == -1 )
goto leave;
nbits = c << 8;
if( (c = iobuf_get(inp)) == -1 )
goto leave;
nbits |= c;
if( nbits > MAX_EXTERN_MPI_BITS ) {
log_error("mpi too large (%u bits)\n", nbits);
goto leave;
}
nread = 2;
nbytes = (nbits+7) / 8;
nlimbs = (nbytes+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB;
#ifdef M_DEBUG
val = secure? mpi_debug_alloc_secure( nlimbs, info )
: mpi_debug_alloc( nlimbs, info );
#else
val = secure? mpi_alloc_secure( nlimbs )
: mpi_alloc( nlimbs );
#endif
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++ ) {
a <<= 8;
a |= iobuf_get(inp) & 0xff; nread++;
}
i = 0;
val->d[j-1] = a;
}
leave:
if( nread > *ret_nread )
log_bug("mpi crosses packet border");
else
*ret_nread = nread;
return val;
}
MPI
mpi_read_from_buffer(byte *buffer, unsigned *ret_nread, int secure)
{
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 ) {
log_error("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 = secure? mpi_alloc_secure( nlimbs )
: mpi_alloc( nlimbs );
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 )
log_bug("mpi larger than buffer");
a <<= 8;
a |= *buffer++;
}
i = 0;
val->d[j-1] = a;
}
leave:
*ret_nread = nread;
return val;
}
/****************
* 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 1; /* 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 )
mpi_resize(val, nlimbs );
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;
}
/****************
* print an MPI to the given stream and return the number of characters
* printed.
*/
int
mpi_print( FILE *fp, MPI a, int mode )
{
int i, n=0;
if( a == MPI_NULL )
return fprintf(fp, "[MPI_NULL]");
if( !mode ) {
unsigned n1, n2;
n1 = mpi_get_nbits(a);
n2 = mpi_get_nbit_info(a);
if( n2 && n2 != n1 )
n += fprintf(fp, "[%u bits (%u)]", n1, n2 );
else
n += fprintf(fp, "[%u bits]", n1);
}
else {
if( a->sign )
putc('-', fp);
#if BYTES_PER_MPI_LIMB == 2
#define X "4"
#elif BYTES_PER_MPI_LIMB == 4
#define X "8"
#elif BYTES_PER_MPI_LIMB == 8
#define X "16"
#else
#error please define the format here
#endif
for(i=a->nlimbs; i > 0 ; i-- ) {
n += fprintf(fp, i!=a->nlimbs? "%0" X "lX":"%lX", (ulong)a->d[i-1]);
#undef X
}
if( !a->nlimbs )
putc('0', fp );
}
return n;
}
void
g10_log_mpidump( const char *text, MPI a )
{
FILE *fp = log_stream();
g10_log_print_prefix(text);
mpi_print(fp, a, 1 );
fputc('\n', fp);
}
/****************
* 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( 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 m_alloced 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.
*/
static byte *
do_get_buffer( MPI a, unsigned *nbytes, int *sign, int force_secure )
{
byte *p, *buffer;
mpi_limb_t alimb;
int i;
if( sign )
*sign = a->sign;
*nbytes = a->nlimbs * BYTES_PER_MPI_LIMB;
p = buffer = force_secure || mpi_is_secure(a) ? m_alloc_secure( *nbytes)
: m_alloc( *nbytes );
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 oepration 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;
}
byte *
mpi_get_buffer( MPI a, unsigned *nbytes, int *sign )
{
return do_get_buffer( a, nbytes, sign, 0 );
}
byte *
mpi_get_secure_buffer( MPI a, unsigned *nbytes, int *sign )
{
return do_get_buffer( a, nbytes, sign, 1 );
}
/****************
* Use BUFFER to update MPI.
*/
void
mpi_set_buffer( MPI a, const byte *buffer, unsigned nbytes, int sign )
{
const byte *p;
mpi_limb_t alimb;
int nlimbs;
int i;
nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
RESIZE_IF_NEEDED(a, nlimbs);
a->sign = sign;
for(i=0, p = buffer+nbytes-1; p >= buffer+BYTES_PER_MPI_LIMB; ) {
#if BYTES_PER_MPI_LIMB == 4
alimb = *p-- ;
alimb |= *p-- << 8 ;
alimb |= *p-- << 16 ;
alimb |= *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 |= *p-- << 8 ;
if( p >= buffer ) alimb |= *p-- << 16 ;
if( p >= buffer ) alimb |= *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;
assert( i == nlimbs );
}

File Metadata

Mime Type
text/x-c
Expires
Mon, Dec 23, 5:45 PM (2 m, 35 s)
Storage Engine
local-disk
Storage Format
Raw Data
Storage Handle
b0/10/33069355997fe4888138d21bb250

Event Timeline