mirror of git://git.gnupg.org/gnupg.git
387 lines
9.2 KiB
C
387 lines
9.2 KiB
C
/* mpicoder.c - Coder for the external representation of MPIs
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* Copyright (C) 1998 Free Software Foundation, Inc.
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*
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* This file is part of GNUPG.
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*
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* GNUPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GNUPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include <config.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <assert.h>
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#include "mpi.h"
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#include "mpi-internal.h"
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#include "iobuf.h"
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#include "memory.h"
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#include "util.h"
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#ifdef M_DEBUG
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#undef mpi_read
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#endif
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#define MAX_EXTERN_MPI_BITS 16384
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/****************
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* write an mpi to out.
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*/
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int
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mpi_write( IOBUF out, MPI a )
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{
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int rc;
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unsigned nbits = mpi_get_nbits(a);
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byte *p, *buf;
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unsigned n;
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if( nbits > MAX_EXTERN_MPI_BITS )
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log_bug("mpi_encode: mpi too large (%u bits)\n", nbits);
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iobuf_put(out, (nbits >>8) );
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iobuf_put(out, (nbits) );
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p = buf = mpi_get_buffer( a, &n, NULL );
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rc = iobuf_write( out, p, n );
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m_free(buf);
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return rc;
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}
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/****************
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* Read an external representation of an mpi and return the MPI
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* The external format is a 16 bit unsigned value stored in network byte order,
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* giving the number of bits for the following integer. The integer is stored
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* with MSB first (left padded with zeroes to align on a byte boundary).
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*/
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MPI
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#ifdef M_DEBUG
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mpi_debug_read(IOBUF inp, unsigned *ret_nread, int secure, const char *info)
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#else
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mpi_read(IOBUF inp, unsigned *ret_nread, int secure)
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#endif
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{
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int c, i, j;
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unsigned nbits, nbytes, nlimbs, nread=0;
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mpi_limb_t a;
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MPI val = MPI_NULL;
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if( (c = iobuf_get(inp)) == -1 )
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goto leave;
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nbits = c << 8;
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if( (c = iobuf_get(inp)) == -1 )
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goto leave;
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nbits |= c;
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if( nbits > MAX_EXTERN_MPI_BITS ) {
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log_error("mpi too large (%u bits)\n", nbits);
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goto leave;
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}
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nread = 2;
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nbytes = (nbits+7) / 8;
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nlimbs = (nbytes+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB;
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#ifdef M_DEBUG
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val = secure? mpi_debug_alloc_secure( nlimbs, info )
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: mpi_debug_alloc( nlimbs, info );
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#else
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val = secure? mpi_alloc_secure( nlimbs )
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: mpi_alloc( nlimbs );
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#endif
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i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
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i %= BYTES_PER_MPI_LIMB;
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val->nbits = nbits;
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j= val->nlimbs = nlimbs;
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val->sign = 0;
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for( ; j > 0; j-- ) {
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a = 0;
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for(; i < BYTES_PER_MPI_LIMB; i++ ) {
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a <<= 8;
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a |= iobuf_get(inp) & 0xff; nread++;
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}
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i = 0;
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val->d[j-1] = a;
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}
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leave:
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if( nread > *ret_nread )
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log_bug("mpi crosses packet border");
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else
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*ret_nread = nread;
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return val;
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}
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/****************
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* Make an mpi from a character string.
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*/
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int
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mpi_fromstr(MPI val, const char *str)
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{
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int hexmode=0, sign=0, prepend_zero=0, i, j, c, c1, c2;
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unsigned nbits, nbytes, nlimbs;
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mpi_limb_t a;
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if( *str == '-' ) {
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sign = 1;
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str++;
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}
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if( *str == '0' && str[1] == 'x' )
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hexmode = 1;
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else
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return 1; /* other bases are not yet supported */
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str += 2;
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nbits = strlen(str)*4;
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if( nbits % 8 )
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prepend_zero = 1;
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nbytes = (nbits+7) / 8;
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nlimbs = (nbytes+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB;
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if( val->alloced < nlimbs )
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mpi_resize(val, nlimbs );
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i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
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i %= BYTES_PER_MPI_LIMB;
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j= val->nlimbs = nlimbs;
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val->sign = sign;
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for( ; j > 0; j-- ) {
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a = 0;
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for(; i < BYTES_PER_MPI_LIMB; i++ ) {
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if( prepend_zero ) {
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c1 = '0';
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prepend_zero = 0;
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}
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else
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c1 = *str++;
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assert(c1);
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c2 = *str++;
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assert(c2);
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if( c1 >= '0' && c1 <= '9' )
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c = c1 - '0';
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else if( c1 >= 'a' && c1 <= 'f' )
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c = c1 - 'a' + 10;
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else if( c1 >= 'A' && c1 <= 'F' )
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c = c1 - 'A' + 10;
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else {
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mpi_clear(val);
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return 1;
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}
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c <<= 4;
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if( c2 >= '0' && c2 <= '9' )
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c |= c2 - '0';
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else if( c2 >= 'a' && c2 <= 'f' )
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c |= c2 - 'a' + 10;
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else if( c2 >= 'A' && c2 <= 'F' )
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c |= c2 - 'A' + 10;
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else {
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mpi_clear(val);
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return 1;
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}
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a <<= 8;
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a |= c;
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}
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i = 0;
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val->d[j-1] = a;
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}
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return 0;
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}
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/****************
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* print an MPI to the given stream and return the number of characters
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* printed.
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*/
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int
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mpi_print( FILE *fp, MPI a, int mode )
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{
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int i, n=0;
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if( a == MPI_NULL )
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return fprintf(fp, "[MPI_NULL]");
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if( !mode )
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n += fprintf(fp, "[%u bits]", mpi_get_nbits(a) );
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else {
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if( a->sign )
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putc('-', fp);
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#if BYTES_PER_MPI_LIMB == 2
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#define X "4"
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#elif BYTES_PER_MPI_LIMB == 4
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#define X "8"
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#elif BYTES_PER_MPI_LIMB == 8
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#define X "16"
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#else
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#error please define the format here
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#endif
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for(i=a->nlimbs; i > 0 ; i-- ) {
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n += fprintf(fp, i!=a->nlimbs? "%0" X "lX":"%lX", (ulong)a->d[i-1]);
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#undef X
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}
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if( !a->nlimbs )
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putc('0', fp );
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}
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return n;
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}
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/****************
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* Special function to get the low 8 bytes from an mpi.
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* This can be used as a keyid; KEYID is an 2 element array.
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* Return the low 4 bytes.
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*/
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u32
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mpi_get_keyid( MPI a, u32 *keyid )
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{
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#if BYTES_PER_MPI_LIMB == 4
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if( keyid ) {
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keyid[0] = a->nlimbs >= 2? a->d[1] : 0;
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keyid[1] = a->nlimbs >= 1? a->d[0] : 0;
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}
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return a->nlimbs >= 1? a->d[0] : 0;
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#elif BYTES_PER_MPI_LIMB == 8
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if( keyid ) {
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keyid[0] = a->nlimbs? (u32)(a->d[0] >> 32) : 0;
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keyid[1] = a->nlimbs? (u32)(a->d[0] & 0xffffffff) : 0;
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}
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return a->nlimbs? (u32)(a->d[0] & 0xffffffff) : 0;
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#else
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#error Make this function work with other LIMB sizes
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#endif
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}
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/****************
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* Return an m_alloced buffer with the MPI (msb first).
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* NBYTES receives the length of this buffer. Caller must free the
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* return string (This function does return a 0 byte buffer with NBYTES
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* set to zero if the value of A is zero. If sign is not NULL, it will
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* be set to the sign of the A.
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*/
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static byte *
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do_get_buffer( MPI a, unsigned *nbytes, int *sign, int force_secure )
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{
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byte *p, *buffer;
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mpi_limb_t alimb;
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int i;
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if( sign )
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*sign = a->sign;
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*nbytes = a->nlimbs * BYTES_PER_MPI_LIMB;
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p = buffer = force_secure || a->secure ? m_alloc_secure( *nbytes)
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: m_alloc( *nbytes );
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for(i=a->nlimbs-1; i >= 0; i-- ) {
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alimb = a->d[i];
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#if BYTES_PER_MPI_LIMB == 4
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*p++ = alimb >> 24;
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*p++ = alimb >> 16;
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*p++ = alimb >> 8;
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*p++ = alimb ;
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#elif BYTES_PER_MPI_LIMB == 8
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*p++ = alimb >> 56;
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*p++ = alimb >> 48;
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*p++ = alimb >> 40;
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*p++ = alimb >> 32;
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*p++ = alimb >> 24;
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*p++ = alimb >> 16;
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*p++ = alimb >> 8;
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*p++ = alimb ;
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#else
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#error please implement for this limb size.
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#endif
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}
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/* this is sub-optimal but we need to do the shift oepration because
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* the caller has to free the returned buffer */
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for(p=buffer; !*p && *nbytes; p++, --*nbytes )
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;
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if( p != buffer )
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memmove(buffer,p, *nbytes);
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return buffer;
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}
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byte *
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mpi_get_buffer( MPI a, unsigned *nbytes, int *sign )
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{
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return do_get_buffer( a, nbytes, sign, 0 );
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}
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byte *
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mpi_get_secure_buffer( MPI a, unsigned *nbytes, int *sign )
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{
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return do_get_buffer( a, nbytes, sign, 1 );
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}
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/****************
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* Use BUFFER to update MPI.
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*/
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void
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mpi_set_buffer( MPI a, const byte *buffer, unsigned nbytes, int sign )
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{
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const byte *p;
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mpi_limb_t alimb;
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int nlimbs;
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int i;
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nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
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RESIZE_IF_NEEDED(a, nlimbs);
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a->sign = sign;
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for(i=0, p = buffer+nbytes-1; p >= buffer+BYTES_PER_MPI_LIMB; ) {
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#if BYTES_PER_MPI_LIMB == 4
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alimb = *p-- ;
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alimb |= *p-- << 8 ;
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alimb |= *p-- << 16 ;
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alimb |= *p-- << 24 ;
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#elif BYTES_PER_MPI_LIMB == 8
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/* cast due to egc's "left shift count >= width of type" warning*/
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alimb = (mpi_limb_t)*p-- ;
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alimb |= (mpi_limb_t)*p-- << 8 ;
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alimb |= (mpi_limb_t)*p-- << 16 ;
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alimb |= (mpi_limb_t)*p-- << 24 ;
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alimb |= (mpi_limb_t)*p-- << 32 ;
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alimb |= (mpi_limb_t)*p-- << 40 ;
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alimb |= (mpi_limb_t)*p-- << 48 ;
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alimb |= (mpi_limb_t)*p-- << 56 ;
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#else
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#error please implement for this limb size.
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#endif
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a->d[i++] = alimb;
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}
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if( p >= buffer ) {
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#if BYTES_PER_MPI_LIMB == 4
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alimb = *p-- ;
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if( p >= buffer ) alimb |= *p-- << 8 ;
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if( p >= buffer ) alimb |= *p-- << 16 ;
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if( p >= buffer ) alimb |= *p-- << 24 ;
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#elif BYTES_PER_MPI_LIMB == 8
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alimb = (mpi_limb_t)*p-- ;
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if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 8 ;
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if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 16 ;
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if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 24 ;
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if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 32 ;
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if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 40 ;
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if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 48 ;
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if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 56 ;
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#else
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#error please implement for this limb size.
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#endif
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a->d[i++] = alimb;
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}
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a->nlimbs = i;
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assert( i == nlimbs );
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}
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