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seckey-cert.c
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/* seckey-cert.c - secret key certifucate packet handling
* 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 "memory.h"
#include "packet.h"
#include "mpi.h"
#include "keydb.h"
#include "cipher.h"
#if BLOWFISH_BLOCKSIZE != 8
#error unsupportted blocksize
#endif
static u16
checksum_u16( unsigned n )
{
u16 a;
a = (n >> 8) & 0xff;
a |= n & 0xff;
return a;
}
static u16
checksum( byte *p, unsigned n )
{
u16 a;
for(a=0; n; n-- )
a += *p++;
return a;
}
static int
check_elg( PKT_secret_cert *cert )
{
byte *buffer;
u16 n, csum=0;
int res;
unsigned nbytes;
u32 keyid[2];
ELG_secret_key skey;
char save_iv[8];
if( cert->d.elg.is_protected ) { /* remove the protection */
DEK *dek = NULL;
MPI test_x;
BLOWFISH_context *blowfish_ctx=NULL;
switch( cert->d.elg.protect_algo ) {
case CIPHER_ALGO_NONE: log_bug(NULL); break;
case CIPHER_ALGO_BLOWFISH:
keyid_from_skc( cert, keyid );
dek = get_passphrase_hash( keyid, NULL );
blowfish_ctx = m_alloc_secure( sizeof *blowfish_ctx );
blowfish_setkey( blowfish_ctx, dek->key, dek->keylen );
m_free(dek); /* pw is in secure memory, so m_free() burns it */
blowfish_setiv( blowfish_ctx, NULL );
memcpy(save_iv, cert->d.elg.protect.blowfish.iv, 8 );
blowfish_decode_cfb( blowfish_ctx,
cert->d.elg.protect.blowfish.iv,
cert->d.elg.protect.blowfish.iv, 8 );
buffer = mpi_get_buffer( cert->d.elg.x, &nbytes, NULL );
csum = checksum_u16( nbytes*8 );
blowfish_decode_cfb( blowfish_ctx, buffer, buffer, nbytes );
csum += checksum( buffer, nbytes );
test_x = mpi_alloc_secure( mpi_get_nlimbs(cert->d.elg.x) );
mpi_set_buffer( test_x, buffer, nbytes, 0 );
m_free( buffer );
m_free( blowfish_ctx );
/* now let's see wether we have used the right passphrase */
if( csum != cert->d.elg.csum ) {
mpi_free(test_x);
memcpy( cert->d.elg.protect.blowfish.iv, save_iv, 8 );
return G10ERR_BAD_PASS;
}
skey.p = cert->d.elg.p;
skey.g = cert->d.elg.g;
skey.y = cert->d.elg.y;
skey.x = test_x;
res = elg_check_secret_key( &skey );
memset( &skey, 0, sizeof skey );
if( !res ) {
mpi_free(test_x);
memcpy( cert->d.elg.protect.blowfish.iv, save_iv, 8 );
return G10ERR_BAD_PASS;
}
mpi_set(cert->d.elg.x, test_x);
mpi_free(test_x);
cert->d.elg.is_protected = 0;
break;
default:
return G10ERR_CIPHER_ALGO; /* unsupport protection algorithm */
}
}
else { /* not protected */
buffer = mpi_get_buffer( cert->d.elg.x, &nbytes, NULL );
csum = checksum_u16( nbytes*8 );
csum += checksum( buffer, nbytes );
m_free( buffer );
if( csum != cert->d.elg.csum )
return G10ERR_CHECKSUM;
}
return 0;
}
static int
protect_elg( PKT_secret_cert *cert, DEK *dek )
{
byte *buffer;
unsigned nbytes;
if( !cert->d.elg.is_protected ) { /* add the protection */
BLOWFISH_context *blowfish_ctx=NULL;
switch( cert->d.elg.protect_algo ) {
case CIPHER_ALGO_NONE: log_bug(NULL); break;
case CIPHER_ALGO_BLOWFISH:
blowfish_ctx = m_alloc_secure( sizeof *blowfish_ctx );
blowfish_setkey( blowfish_ctx, dek->key, dek->keylen );
blowfish_setiv( blowfish_ctx, NULL );
blowfish_encode_cfb( blowfish_ctx,
cert->d.elg.protect.blowfish.iv,
cert->d.elg.protect.blowfish.iv, 8 );
buffer = mpi_get_buffer( cert->d.elg.x, &nbytes, NULL );
blowfish_encode_cfb( blowfish_ctx, buffer, buffer, nbytes );
mpi_set_buffer( cert->d.elg.x, buffer, nbytes, 0 );
m_free( buffer );
m_free( blowfish_ctx );
cert->d.elg.is_protected = 1;
break;
default:
return G10ERR_CIPHER_ALGO; /* unsupport protection algorithm */
}
}
return 0;
}
#ifdef HAVE_RSA_CIPHER
static int
check_rsa( PKT_secret_cert *cert )
{
byte *buffer;
u16 n, csum=0;
int res;
unsigned nbytes;
u32 keyid[2];
RSA_secret_key skey;
if( cert->d.rsa.is_protected ) { /* remove the protection */
DEK *dek = NULL;
BLOWFISH_context *blowfish_ctx=NULL;
switch( cert->d.rsa.protect_algo ) {
/* FIXME: use test variables to check for the correct key */
case CIPHER_ALGO_NONE: log_bug(NULL); break;
case CIPHER_ALGO_BLOWFISH:
keyid_from_skc( cert, keyid );
dek = get_passphrase_hash( keyid, NULL );
blowfish_ctx = m_alloc_secure( sizeof *blowfish_ctx );
blowfish_setkey( blowfish_ctx, dek->key, dek->keylen );
m_free(dek); /* pw is in secure memory, so m_free() burns it */
blowfish_setiv( blowfish_ctx, NULL );
blowfish_decode_cfb( blowfish_ctx,
cert->d.rsa.protect.blowfish.iv,
cert->d.rsa.protect.blowfish.iv, 8 );
csum = 0;
#define X(a) do { \
buffer = mpi_get_buffer( cert->d.rsa.rsa_##a, &nbytes, NULL );\
csum += checksum_u16( nbytes*8 ); \
blowfish_decode_cfb( blowfish_ctx, buffer, buffer, nbytes ); \
csum += checksum( buffer, nbytes ); \
mpi_set_buffer(cert->d.rsa.rsa_##a, buffer, nbytes, 0 ); \
m_free( buffer ); \
} while(0)
X(d);
X(p);
X(q);
X(u);
#undef X
cert->d.rsa.is_protected = 0;
m_free( blowfish_ctx );
/* now let's see wether we have used the right passphrase */
if( csum != cert->d.rsa.csum )
return G10ERR_BAD_PASS;
skey.d = cert->d.rsa.rsa_d;
skey.p = cert->d.rsa.rsa_p;
skey.q = cert->d.rsa.rsa_q;
skey.u = cert->d.rsa.rsa_u;
res = rsa_check_secret_key( &skey );
memset( &skey, 0, sizeof skey );
if( !res )
return G10ERR_BAD_PASS;
break;
default:
return G10ERR_CIPHER_ALGO; /* unsupported protection algorithm */
}
}
else { /* not protected */
csum =0;
buffer = mpi_get_buffer( cert->d.rsa.rsa_d, &nbytes, NULL );
csum += checksum_u16( nbytes*8 );
csum += checksum( buffer, nbytes );
m_free( buffer );
buffer = mpi_get_buffer( cert->d.rsa.rsa_p, &nbytes, NULL );
csum += checksum_u16( nbytes*8 );
csum += checksum( buffer, nbytes );
m_free( buffer );
buffer = mpi_get_buffer( cert->d.rsa.rsa_q, &nbytes, NULL );
csum += checksum_u16( nbytes*8 );
csum += checksum( buffer, nbytes );
m_free( buffer );
buffer = mpi_get_buffer( cert->d.rsa.rsa_u, &nbytes, NULL );
csum += checksum_u16( nbytes*8 );
csum += checksum( buffer, nbytes );
m_free( buffer );
if( csum != cert->d.rsa.csum )
return G10ERR_CHECKSUM;
}
return 0;
}
#endif /*HAVE_RSA_CIPHER*/
/****************
* Check the secret key certificate
* Ask up to 3 time for a correct passphrase
*/
int
check_secret_key( PKT_secret_cert *cert )
{
int rc = G10ERR_BAD_PASS;
int i;
for(i=0; i < 3 && rc == G10ERR_BAD_PASS; i++ ) {
if( i )
log_error("Invalid passphrase; please try again ...\n");
if( cert->pubkey_algo == PUBKEY_ALGO_ELGAMAL )
rc = check_elg( cert );
#ifdef HAVE_RSA_CIPHER
else if( cert->pubkey_algo == PUBKEY_ALGO_RSA )
rc = check_rsa( cert );
#endif
else
rc = G10ERR_PUBKEY_ALGO;
if( get_passphrase_fd() != -1 )
break;
}
return rc;
}
/****************
* Protect the secret key certificate with the passphrase from DEK
*/
int
protect_secret_key( PKT_secret_cert *cert, DEK *dek )
{
if( !dek )
return 0;
if( cert->pubkey_algo == PUBKEY_ALGO_ELGAMAL )
return protect_elg( cert, dek );
#ifdef 0 /* noy yet implemented */
else if( cert->pubkey_algo == PUBKEY_ALGO_RSA )
return protect_rsa( cert, dek );
#endif
else
return G10ERR_PUBKEY_ALGO;
}

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