/* 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; }