--- /dev/null
+/* 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 )
+ printk("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) {
+ printk("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 ) {
+ printk("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;
+}
+
+
+/****************
+ * 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;
+}
+
+
+/****************
+ * 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;
+}
+
+
+/****************
+ * 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) {
+ printk("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i, nlimbs);
+ BUG();
+ }
+ return 0;
+}
+
git://git.onelab.eu / linux-2.6.git / blobdiff