mirror of
git://git.gnupg.org/gnupg.git
synced 2024-12-22 10:19:57 +01:00
238 lines
6.7 KiB
C
238 lines
6.7 KiB
C
/* seskey.c - make sesssion keys etc.
|
|
* Copyright (c) 1997 by Werner Koch (dd9jn)
|
|
*
|
|
* This file is part of G10.
|
|
*
|
|
* G10 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.
|
|
*
|
|
* G10 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 <stdlib.h>
|
|
#include <string.h>
|
|
#include <assert.h>
|
|
#include "util.h"
|
|
#include "cipher.h"
|
|
#include "mpi.h"
|
|
#include "main.h"
|
|
|
|
|
|
|
|
/****************
|
|
* Make a session key and put it into DEK
|
|
*/
|
|
void
|
|
make_session_key( DEK *dek )
|
|
{
|
|
switch( dek->algo ) {
|
|
case CIPHER_ALGO_BLOWFISH:
|
|
dek->keylen = 20;
|
|
randomize_buffer( dek->key, dek->keylen, 1 );
|
|
break;
|
|
|
|
default: log_bug("invalid algo %d in make_session_key()\n");
|
|
}
|
|
}
|
|
|
|
|
|
/****************
|
|
* Encode the session key. NBITS is the number of bits which should be used
|
|
* for packing the session key.
|
|
* returns: A mpi with the session key (caller must free)
|
|
*/
|
|
MPI
|
|
encode_session_key( DEK *dek, unsigned nbits )
|
|
{
|
|
int nframe = (nbits+7) / 8;
|
|
byte *p;
|
|
MPI frame;
|
|
int i,n,c;
|
|
u16 csum;
|
|
|
|
/* the current limitation is, that we can only use a session key
|
|
* which length is a multiple of BITS_PER_MPI_LIMB
|
|
* I think we can live with that.
|
|
*/
|
|
if( dek->keylen + 7 > nframe || (nbits % BITS_PER_MPI_LIMB) || !nframe )
|
|
log_bug("can't encode a %d bit key in a %d bits frame\n",
|
|
dek->keylen*8, nbits );
|
|
|
|
/* We encode the session key in this way:
|
|
*
|
|
* 0 2 RND(n bytes) 0 A DEK(k bytes) CSUM(2 bytes)
|
|
*
|
|
* RND are non-zero random bytes.
|
|
* A is the cipher algorithm
|
|
* DEK is the encryption key (session key) length k depends on the
|
|
* cipher algorithm (20 is used with blowfish).
|
|
* CSUM is the 16 bit checksum over the DEK
|
|
*/
|
|
frame = mpi_alloc_secure( nframe / BYTES_PER_MPI_LIMB );
|
|
csum = 0;
|
|
for( p = dek->key, i=0; i < dek->keylen; i++ )
|
|
csum += *p++;
|
|
mpi_putbyte(frame, 0, csum );
|
|
mpi_putbyte(frame, 1, csum >> 8 );
|
|
for(n=2,i=dek->keylen-1, p = dek->key; i >= 0; i--, n++ )
|
|
mpi_putbyte(frame, n, p[i] );
|
|
mpi_putbyte(frame, n++, dek->algo );
|
|
mpi_putbyte(frame, n++, 0 );
|
|
while( n < nframe-2 ) {
|
|
while( !(c = get_random_byte(1)) )
|
|
;
|
|
mpi_putbyte(frame, n++, c );
|
|
}
|
|
mpi_putbyte(frame, n++, 2 );
|
|
mpi_putbyte(frame, n++, 0 );
|
|
assert( n == nframe );
|
|
return frame;
|
|
}
|
|
|
|
/****************
|
|
* Encode a ripemd160 message digest of LEN bytes into NBITS.
|
|
* returns: A mpi with the session key (caller must free)
|
|
* RMD160 Object ID is 1.3.36.3.2.1
|
|
*/
|
|
MPI
|
|
encode_rmd160_value( byte *md, unsigned len, unsigned nbits )
|
|
{
|
|
static byte asn[15] =
|
|
{ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x24, 0x03,
|
|
0x02, 0x01, 0x05, 0x00, 0x04, 0x14 };
|
|
int nframe = (nbits+7) / 8;
|
|
byte *p;
|
|
MPI frame;
|
|
int i,n,c;
|
|
|
|
if( (nbits % BITS_PER_MPI_LIMB) || nframe < 42 || len != 20 )
|
|
log_bug("can't encode a %d bit MD into a %d bits frame\n",len*8, nbits);
|
|
|
|
/* We encode the MD in this way:
|
|
*
|
|
* 0 A PAD(n bytes) 0 ASN(15 bytes) MD(20 bytes)
|
|
*
|
|
* PAD consists of FF bytes.
|
|
*/
|
|
frame = mpi_alloc_secure( nframe / BYTES_PER_MPI_LIMB );
|
|
n = 0;
|
|
for(i=20-1; i >= 0; i--, n++ )
|
|
mpi_putbyte(frame, n, md[i] );
|
|
for( i=15-1; i >= 0; i--, n++ )
|
|
mpi_putbyte(frame, n, asn[i] );
|
|
mpi_putbyte(frame, n++, 0 );
|
|
while( n < nframe-2 )
|
|
mpi_putbyte(frame, n++, 0xff );
|
|
mpi_putbyte(frame, n++, DIGEST_ALGO_RMD160 );
|
|
mpi_putbyte(frame, n++, 0 );
|
|
assert( n == nframe );
|
|
return frame;
|
|
}
|
|
|
|
/****************
|
|
* Encode a sha-1 message digest of LEN bytes into NBITS.
|
|
* returns: A mpi with the session key (caller must free)
|
|
* SHA-1 Objet ID is 1.3.14.3.2.26
|
|
*/
|
|
MPI
|
|
encode_sha1_value( byte *md, unsigned len, unsigned nbits )
|
|
{
|
|
static byte asn[15] =
|
|
{ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03,
|
|
0x02, 0x1a, 0x05, 0x00, 0x04, 0x14 };
|
|
int nframe = (nbits+7) / 8;
|
|
byte *p;
|
|
MPI frame;
|
|
int i,n,c;
|
|
|
|
if( (nbits % BITS_PER_MPI_LIMB) || nframe < 42 || len != 20 )
|
|
log_bug("can't encode a %d bit MD into a %d bits frame\n",len*8, nbits);
|
|
|
|
/* We encode the MD in this way:
|
|
*
|
|
* 0 A PAD(n bytes) 0 ASN(15 bytes) MD(20 bytes)
|
|
*
|
|
* PAD consists of FF bytes.
|
|
*/
|
|
frame = mpi_alloc_secure( nframe / BYTES_PER_MPI_LIMB );
|
|
n = 0;
|
|
for(i=20-1; i >= 0; i--, n++ )
|
|
mpi_putbyte(frame, n, md[i] );
|
|
for( i=15-1; i >= 0; i--, n++ )
|
|
mpi_putbyte(frame, n, asn[i] );
|
|
mpi_putbyte(frame, n++, 0 );
|
|
while( n < nframe-2 )
|
|
mpi_putbyte(frame, n++, 0xff );
|
|
mpi_putbyte(frame, n++, DIGEST_ALGO_RMD160 );
|
|
mpi_putbyte(frame, n++, 0 );
|
|
assert( n == nframe );
|
|
return frame;
|
|
}
|
|
|
|
|
|
/****************
|
|
* Encode a md5 message digest of LEN bytes into NBITS.
|
|
* returns: A mpi with the session key (caller must free)
|
|
* MD5 Object ID is 1.2.840.113549.2.5
|
|
*/
|
|
MPI
|
|
encode_md5_value( byte *md, unsigned len, unsigned nbits )
|
|
{
|
|
static byte asn[18] =
|
|
{ 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86,0x48,
|
|
0x86, 0xf7, 0x0d, 0x02, 0x05, 0x05, 0x00, 0x04, 0x10 };
|
|
int nframe = (nbits+7) / 8;
|
|
byte *p;
|
|
MPI frame;
|
|
int i,n,c;
|
|
|
|
if( (nbits % BITS_PER_MPI_LIMB) || nframe < 38 || len != 16 )
|
|
log_bug("can't encode a %d bit MD into a %d bits frame\n",len*8, nbits);
|
|
|
|
/* We encode the MD in this way:
|
|
*
|
|
* 0 A PAD(n bytes) 0 ASN(18 bytes) MD(16 bytes)
|
|
*
|
|
* PAD consists of FF bytes.
|
|
*/
|
|
frame = mpi_alloc_secure( nframe / BYTES_PER_MPI_LIMB );
|
|
n = 0;
|
|
for(i=16-1; i >= 0; i--, n++ )
|
|
mpi_putbyte(frame, n, md[i] );
|
|
for( i=18-1; i >= 0; i--, n++ )
|
|
mpi_putbyte(frame, n, asn[i] );
|
|
mpi_putbyte(frame, n++, 0 );
|
|
while( n < nframe-2 )
|
|
mpi_putbyte(frame, n++, 0xff );
|
|
mpi_putbyte(frame, n++, DIGEST_ALGO_MD5 );
|
|
mpi_putbyte(frame, n++, 0 );
|
|
assert( n == nframe );
|
|
return frame;
|
|
}
|
|
|
|
MPI
|
|
encode_md_value( MD_HANDLE *md, unsigned nbits )
|
|
{
|
|
byte *p = md_final( md );
|
|
if( md->algo == DIGEST_ALGO_MD5 )
|
|
return encode_md5_value( p, 16, nbits );
|
|
else if( md->algo == DIGEST_ALGO_RMD160 )
|
|
return encode_rmd160_value( p, 20, nbits );
|
|
else if( md->algo == DIGEST_ALGO_SHA1 )
|
|
return encode_sha1_value( p, 20, nbits );
|
|
else
|
|
log_bug(NULL);
|
|
}
|
|
|