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-rw-r--r--mpi/mpicoder.c474
1 files changed, 474 insertions, 0 deletions
diff --git a/mpi/mpicoder.c b/mpi/mpicoder.c
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+/* mpicoder.c - Coder for the external representation of MPIs
+ * Copyright (C) 1998, 1999, 2005 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+ * 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 );
+ xfree(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 int nmax = *ret_nread;
+ unsigned nbits, nbytes, nlimbs, nread=0;
+ mpi_limb_t a;
+ MPI val = MPI_NULL;
+
+ if (nread == nmax)
+ goto overflow;
+ if( (c = iobuf_get(inp)) == -1 )
+ goto leave;
+ nread++;
+ nbits = c << 8;
+
+ if (nread == nmax)
+ goto overflow;
+ if( (c = iobuf_get(inp)) == -1 )
+ goto leave;
+ nread++;
+ nbits |= c;
+
+ if( nbits > MAX_EXTERN_MPI_BITS ) {
+ log_error("mpi too large for this implementation (%u bits)\n", nbits);
+ goto leave;
+ }
+
+ 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++ ) {
+ if (nread == nmax) {
+#ifdef M_DEBUG
+ mpi_debug_free (val);
+#else
+ mpi_free (val);
+#endif
+ val = NULL;
+ goto overflow;
+ }
+ a <<= 8;
+ a |= iobuf_get(inp) & 0xff; nread++;
+ }
+ i = 0;
+ val->d[j-1] = a;
+ }
+
+ leave:
+ *ret_nread = nread;
+ return val;
+ overflow:
+ log_error ("mpi larger than indicated length (%u bytes)\n", nmax);
+ *ret_nread = nread;
+ return val;
+}
+
+
+MPI
+mpi_read_from_buffer(byte *buffer, unsigned int *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_info ("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 ) {
+ /* This (as well as the above error condition) may
+ happen if we use this function to parse a decrypted
+ MPI which didn't turn out to be a real MPI - possible
+ because the supplied key was wrong but the OpenPGP
+ checksum didn't caught it. */
+ log_info ("mpi larger than buffer\n");
+ mpi_free (val);
+ val = MPI_NULL;
+ goto leave;
+ }
+ 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 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 = 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 xmalloced 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;
+ 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 = force_secure || mpi_is_secure(a) ? xmalloc_secure(n)
+ : xmalloc(n);
+
+ 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;
+}
+
+
+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 = (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;
+ assert( i == nlimbs );
+}
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