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gnupg/mpi/mpicoder.c

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/* 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 "memory.h"
#include "g10lib.h"
#define MAX_EXTERN_MPI_BITS 16384
static 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;
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.
* FIXME: Replace this by the more generic gcry_mpi_print()
*/
static 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 int n1;
n1 = mpi_get_nbits(a);
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 = stderr; /* used to be log_stream() */
/* FIXME: Replace this function by a g10_log_xxx one */
fprintf(fp,"%s: ",text);
mpi_print(fp, a, 1 );
fputc('\n', fp);
}
/****************
* 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 );
}
int
gcry_mpi_scan( struct gcry_mpi **ret_mpi, enum gcry_mpi_format format,
const char *buffer, size_t *nbytes )
{
struct gcry_mpi *a = NULL;
unsigned int len;
len = nbytes? *nbytes : strlen(buffer);
/* TODO: add a way to allocate the MPI in secure memory
* Hmmm: maybe it is better to retrieve this information from
* the provided buffer. */
if( format == GCRYMPI_FMT_STD ) {
const byte *s = buffer;
a = mpi_alloc( (len+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB );
if( len ) { /* not zero */
a->sign = *s & 0x80;
if( a->sign ) {
/* FIXME: we have to convert from 2compl to magnitude format */
mpi_free(a);
return GCRYERR_INTERNAL;
}
else
mpi_set_buffer( a, s, len, 0 );
}
if( ret_mpi )
*ret_mpi = a;
else
mpi_free(a);
return 0;
}
else if( format == GCRYMPI_FMT_USG ) {
a = mpi_alloc( (len+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB );
if( len ) /* not zero */
mpi_set_buffer( a, buffer, len, 0 );
if( ret_mpi )
*ret_mpi = a;
else
mpi_free(a);
return 0;
}
else if( format == GCRYMPI_FMT_PGP ) {
a = mpi_read_from_buffer( (char*)buffer, &len, 0 );
if( nbytes )
*nbytes = len;
if( ret_mpi )
*ret_mpi = a;
else
mpi_free(a);
return a? 0 : GCRYERR_INV_OBJ;
}
else if( format == GCRYMPI_FMT_SSH ) {
const byte *s = buffer;
size_t n;
if( len < 4 )
return GCRYERR_TOO_SHORT;
n = s[0] << 24 | s[1] << 16 | s[2] << 8 | s[3];
s += 4; len -= 4;
if( n > len )
return GCRYERR_TOO_LARGE; /* or should it be too_short */
a = mpi_alloc( (n+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB );
if( len ) { /* not zero */
a->sign = *s & 0x80;
if( a->sign ) {
/* FIXME: we have to convert from 2compl to magnitude format */
mpi_free(a);
return GCRYERR_INTERNAL;
}
else
mpi_set_buffer( a, s, n, 0 );
}
if( nbytes )
*nbytes = n+4;
if( ret_mpi )
*ret_mpi = a;
else
mpi_free(a);
return 0;
}
else if( format == GCRYMPI_FMT_HEX ) {
if( nbytes )
return GCRYERR_INV_ARG; /* can only handle C strings for now */
a = mpi_alloc(0);
if( mpi_fromstr( a, buffer ) )
return GCRYERR_INV_OBJ;
if( ret_mpi )
*ret_mpi = a;
else
mpi_free(a);
return 0;
}
else
return GCRYERR_INV_ARG;
}
/****************
* Write a using format into buffer which has a length of *NBYTES.
* Returns the number of bytes actually written in nbytes.
* Buffer maybe NULL to query the required length of the buffer
*/
int
gcry_mpi_print( enum gcry_mpi_format format, char *buffer, size_t *nbytes,
struct gcry_mpi *a )
{
unsigned int nbits = mpi_get_nbits(a);
size_t len;
if( !nbytes )
return GCRYERR_INV_ARG;
len = *nbytes;
*nbytes = 0;
if( format == GCRYMPI_FMT_STD ) {
char *tmp;
int extra = 0;
unsigned int n;
if( a->sign )
return GCRYERR_INTERNAL; /* can't handle it yet */
tmp = mpi_get_buffer( a, &n, NULL );
if( n && (*tmp & 0x80) ) {
n++;
extra=1;
}
if( n > len && buffer ) {
m_free(tmp);
return GCRYERR_TOO_SHORT; /* the provided buffer is too short */
}
if( buffer ) {
byte *s = buffer;
if( extra )
*s++ = 0;
memcpy( s, tmp, n-extra );
}
m_free(tmp);
*nbytes = n;
return 0;
}
else if( format == GCRYMPI_FMT_PGP ) {
unsigned int n = (nbits + 7)/8;
if( a->sign )
return GCRYERR_INV_ARG; /* pgp format can only handle unsigned */
if( n+2 > len && buffer )
return GCRYERR_TOO_SHORT; /* the provided buffer is too short */
if( buffer ) {
char *tmp;
byte *s = buffer;
s[0] = nbits >> 8;
s[1] = nbits;
tmp = mpi_get_buffer( a, &n, NULL );
memcpy( s+2, tmp, n );
m_free(tmp);
}
*nbytes = n+2;
return 0;
}
else if( format == GCRYMPI_FMT_SSH ) {
char *tmp;
int extra = 0;
unsigned int n;
if( a->sign )
return GCRYERR_INTERNAL; /* can't handle it yet */
tmp = mpi_get_buffer( a, &n, NULL );
if( n && (*tmp & 0x80) ) {
n++;
extra=1;
}
if( n+4 > len && buffer ) {
m_free(tmp);
return GCRYERR_TOO_SHORT; /* the provided buffer is too short */
}
if( buffer ) {
byte *s = buffer;
*s++ = n >> 24;
*s++ = n >> 16;
*s++ = n >> 8;
*s++ = n;
if( extra )
*s++ = 0;
memcpy( s, tmp, n-extra );
}
m_free(tmp);
*nbytes = 4+n;
return 0;
}
else if( format == GCRYMPI_FMT_HEX ) {
byte *tmp;
int i;
int extra = 0;
unsigned int n=0;
tmp = mpi_get_buffer( a, &n, NULL );
if( !n || (*tmp & 0x80) )
extra=1;
if( 2*n+3+1 > len && buffer ) {
m_free(tmp);
return GCRYERR_TOO_SHORT; /* the provided buffer is too short */
}
if( buffer ) {
byte *s = buffer;
if( a->sign )
*s++ = '-';
if( extra ) {
*s++ = '0';
*s++ = '0';
}
for(i=0; i < n; i++ ) {
unsigned int c = tmp[i];
*s++ = (c >> 4) < 10? '0'+(c>>4) : 'A'+(c>>4)-10 ;
c &= 15;
*s++ = c < 10? '0'+c : 'A'+c-10 ;
}
*s++ = 0;
*nbytes = (char*)s - buffer;
}
else {
*nbytes = n;
if( a->sign )
++*nbytes;
if( extra )
*nbytes += 2;
++*nbytes; /* terminating Nul */
}
m_free(tmp);
return 0;
}
else
return GCRYERR_INV_ARG;
}
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