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gnupg/g10/seckey-cert.c
David Shaw eb5045d972 * mainproc.c (proc_symkey_enc), seckey-cert.c (do_check): Check the S2K 
hash algorithm before we try to generate a passphrase using it.  This
prevents hitting BUG() when generating a passphrase using a hash that we
don't have.
2004-06-27 18:26:49 +00:00

397 lines
13 KiB
C
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/* seckey-cert.c - secret key certificate packet handling
* Copyright (C) 1998,1999,2000,2001,2002,2003 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 <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"
#include "main.h"
#include "options.h"
#include "i18n.h"
#include "status.h"
static int
do_check( PKT_secret_key *sk, const char *tryagain_text, int *canceled )
{
byte *buffer;
u16 csum=0;
int i, res;
unsigned nbytes;
if( sk->is_protected ) { /* remove the protection */
DEK *dek = NULL;
u32 keyid[4]; /* 4! because we need two of them */
CIPHER_HANDLE cipher_hd=NULL;
PKT_secret_key *save_sk;
if( sk->protect.s2k.mode == 1001 ) {
log_info(_("secret key parts are not available\n"));
return G10ERR_GENERAL;
}
if( sk->protect.algo == CIPHER_ALGO_NONE )
BUG();
if( check_cipher_algo( sk->protect.algo ) ) {
log_info(_("protection algorithm %d%s is not supported\n"),
sk->protect.algo,sk->protect.algo==1?" (IDEA)":"" );
if (sk->protect.algo==CIPHER_ALGO_IDEA)
{
write_status (STATUS_RSA_OR_IDEA);
idea_cipher_warn (0);
}
return G10ERR_CIPHER_ALGO;
}
if(check_digest_algo(sk->protect.s2k.hash_algo))
{
log_info(_("protection digest %d is not supported\n"),
sk->protect.s2k.hash_algo);
return G10ERR_DIGEST_ALGO;
}
keyid_from_sk( sk, keyid );
keyid[2] = keyid[3] = 0;
if( !sk->is_primary ) {
keyid[2] = sk->main_keyid[0];
keyid[3] = sk->main_keyid[1];
}
dek = passphrase_to_dek( keyid, sk->pubkey_algo, sk->protect.algo,
&sk->protect.s2k, 0,
tryagain_text, canceled);
if (!dek && canceled && *canceled)
return G10ERR_GENERAL;
cipher_hd = cipher_open( sk->protect.algo,
CIPHER_MODE_AUTO_CFB, 1);
cipher_setkey( cipher_hd, dek->key, dek->keylen );
m_free(dek);
save_sk = copy_secret_key( NULL, sk );
cipher_setiv( cipher_hd, sk->protect.iv, sk->protect.ivlen );
csum = 0;
if( sk->version >= 4 ) {
int ndata;
byte *p, *data;
u16 csumc = 0;
i = pubkey_get_npkey(sk->pubkey_algo);
assert( mpi_is_opaque( sk->skey[i] ) );
p = mpi_get_opaque( sk->skey[i], &ndata );
if ( ndata > 1 )
csumc = p[ndata-2] << 8 | p[ndata-1];
data = m_alloc_secure( ndata );
cipher_decrypt( cipher_hd, data, p, ndata );
mpi_free( sk->skey[i] ); sk->skey[i] = NULL ;
p = data;
if (sk->protect.sha1chk) {
/* This is the new SHA1 checksum method to detect
tampering with the key as used by the Klima/Rosa
attack */
sk->csum = 0;
csum = 1;
if( ndata < 20 )
log_error("not enough bytes for SHA-1 checksum\n");
else {
MD_HANDLE h = md_open (DIGEST_ALGO_SHA1, 1);
if (!h)
BUG(); /* algo not available */
md_write (h, data, ndata - 20);
md_final (h);
if (!memcmp (md_read (h, DIGEST_ALGO_SHA1),
data + ndata - 20, 20) ) {
/* digest does match. We have to keep the old
style checksum in sk->csum, so that the
test used for unprotected keys does work.
This test gets used when we are adding new
keys. */
sk->csum = csum = checksum (data, ndata-20);
}
md_close (h);
}
}
else {
if( ndata < 2 ) {
log_error("not enough bytes for checksum\n");
sk->csum = 0;
csum = 1;
}
else {
csum = checksum( data, ndata-2);
sk->csum = data[ndata-2] << 8 | data[ndata-1];
if ( sk->csum != csum ) {
/* This is a PGP 7.0.0 workaround */
sk->csum = csumc; /* take the encrypted one */
}
}
}
/* must check it here otherwise the mpi_read_xx would fail
because the length may have an arbitrary value */
if( sk->csum == csum ) {
for( ; i < pubkey_get_nskey(sk->pubkey_algo); i++ ) {
nbytes = ndata;
sk->skey[i] = mpi_read_from_buffer(p, &nbytes, 1 );
ndata -= nbytes;
p += nbytes;
}
/* Note: at this point ndata should be 2 for a simple
checksum or 20 for the sha1 digest */
}
m_free(data);
}
else {
for(i=pubkey_get_npkey(sk->pubkey_algo);
i < pubkey_get_nskey(sk->pubkey_algo); i++ ) {
byte *p;
int ndata;
unsigned int dummy;
assert (mpi_is_opaque (sk->skey[i]));
p = mpi_get_opaque (sk->skey[i], &ndata);
assert (ndata >= 2);
assert (ndata == ((p[0] << 8 | p[1]) + 7)/8 + 2);
buffer = m_alloc_secure (ndata);
cipher_sync (cipher_hd);
buffer[0] = p[0];
buffer[1] = p[1];
cipher_decrypt (cipher_hd, buffer+2, p+2, ndata-2);
csum += checksum (buffer, ndata);
mpi_free (sk->skey[i]);
dummy = ndata;
sk->skey[i] = mpi_read_from_buffer (buffer, &dummy, 1);
assert (sk->skey[i]);
m_free (buffer);
/* csum += checksum_mpi (sk->skey[i]); */
}
}
cipher_close( cipher_hd );
/* now let's see whether we have used the right passphrase */
if( csum != sk->csum ) {
copy_secret_key( sk, save_sk );
passphrase_clear_cache ( keyid, sk->pubkey_algo );
free_secret_key( save_sk );
return G10ERR_BAD_PASS;
}
/* the checksum may fail, so we also check the key itself */
res = pubkey_check_secret_key( sk->pubkey_algo, sk->skey );
if( res ) {
copy_secret_key( sk, save_sk );
passphrase_clear_cache ( keyid, sk->pubkey_algo );
free_secret_key( save_sk );
return G10ERR_BAD_PASS;
}
free_secret_key( save_sk );
sk->is_protected = 0;
}
else { /* not protected, assume it is okay if the checksum is okay */
csum = 0;
for(i=pubkey_get_npkey(sk->pubkey_algo);
i < pubkey_get_nskey(sk->pubkey_algo); i++ ) {
csum += checksum_mpi( sk->skey[i] );
}
if( csum != sk->csum )
return G10ERR_CHECKSUM;
}
return 0;
}
/****************
* Check the secret key
* Ask up to 3 (or n) times for a correct passphrase
*/
int
check_secret_key( PKT_secret_key *sk, int n )
{
int rc = G10ERR_BAD_PASS;
int i;
if( n < 1 )
n = (opt.batch && !opt.use_agent)? 1 : 3; /* use the default value */
for(i=0; i < n && rc == G10ERR_BAD_PASS; i++ ) {
int canceled;
const char *tryagain = NULL;
if (i) {
tryagain = N_("Invalid passphrase; please try again");
log_info (_("%s ...\n"), _(tryagain));
}
rc = do_check( sk, tryagain, &canceled );
if( rc == G10ERR_BAD_PASS && is_status_enabled() ) {
u32 kid[2];
char buf[50];
keyid_from_sk( sk, kid );
sprintf(buf, "%08lX%08lX", (ulong)kid[0], (ulong)kid[1]);
write_status_text( STATUS_BAD_PASSPHRASE, buf );
}
if( have_static_passphrase() || canceled )
break;
}
if( !rc )
write_status( STATUS_GOOD_PASSPHRASE );
return rc;
}
/****************
* check whether the secret key is protected.
* Returns: 0 not protected, -1 on error or the protection algorithm
*/
int
is_secret_key_protected( PKT_secret_key *sk )
{
return sk->is_protected? sk->protect.algo : 0;
}
/****************
* Protect the secret key with the passphrase from DEK
*/
int
protect_secret_key( PKT_secret_key *sk, DEK *dek )
{
int i,j, rc = 0;
byte *buffer;
unsigned nbytes;
u16 csum;
if( !dek )
return 0;
if( !sk->is_protected ) { /* okay, apply the protection */
CIPHER_HANDLE cipher_hd=NULL;
if( check_cipher_algo( sk->protect.algo ) )
rc = G10ERR_CIPHER_ALGO; /* unsupport protection algorithm */
else {
print_cipher_algo_note( sk->protect.algo );
cipher_hd = cipher_open( sk->protect.algo,
CIPHER_MODE_AUTO_CFB, 1 );
if( cipher_setkey( cipher_hd, dek->key, dek->keylen ) )
log_info(_("WARNING: Weak key detected"
" - please change passphrase again.\n"));
sk->protect.ivlen = cipher_get_blocksize( sk->protect.algo );
assert( sk->protect.ivlen <= DIM(sk->protect.iv) );
if( sk->protect.ivlen != 8 && sk->protect.ivlen != 16 )
BUG(); /* yes, we are very careful */
randomize_buffer(sk->protect.iv, sk->protect.ivlen, 1);
cipher_setiv( cipher_hd, sk->protect.iv, sk->protect.ivlen );
if( sk->version >= 4 ) {
byte *bufarr[PUBKEY_MAX_NSKEY];
unsigned narr[PUBKEY_MAX_NSKEY];
unsigned nbits[PUBKEY_MAX_NSKEY];
int ndata=0;
byte *p, *data;
for(j=0, i = pubkey_get_npkey(sk->pubkey_algo);
i < pubkey_get_nskey(sk->pubkey_algo); i++, j++ ) {
assert( !mpi_is_opaque( sk->skey[i] ) );
bufarr[j] = mpi_get_buffer( sk->skey[i], &narr[j], NULL );
nbits[j] = mpi_get_nbits( sk->skey[i] );
ndata += narr[j] + 2;
}
for( ; j < PUBKEY_MAX_NSKEY; j++ )
bufarr[j] = NULL;
ndata += opt.simple_sk_checksum? 2 : 20; /* for checksum */
data = m_alloc_secure( ndata );
p = data;
for(j=0; j < PUBKEY_MAX_NSKEY && bufarr[j]; j++ ) {
p[0] = nbits[j] >> 8 ;
p[1] = nbits[j];
p += 2;
memcpy(p, bufarr[j], narr[j] );
p += narr[j];
m_free(bufarr[j]);
}
if (opt.simple_sk_checksum) {
log_info (_("generating the deprecated 16-bit checksum"
" for secret key protection\n"));
csum = checksum( data, ndata-2);
sk->csum = csum;
*p++ = csum >> 8;
*p++ = csum;
sk->protect.sha1chk = 0;
}
else {
MD_HANDLE h = md_open (DIGEST_ALGO_SHA1, 1);
if (!h)
BUG(); /* algo not available */
md_write (h, data, ndata - 20);
md_final (h);
memcpy (p, md_read (h, DIGEST_ALGO_SHA1), 20);
p += 20;
md_close (h);
sk->csum = csum = 0;
sk->protect.sha1chk = 1;
}
assert( p == data+ndata );
cipher_encrypt( cipher_hd, data, data, ndata );
for(i = pubkey_get_npkey(sk->pubkey_algo);
i < pubkey_get_nskey(sk->pubkey_algo); i++ ) {
mpi_free( sk->skey[i] );
sk->skey[i] = NULL;
}
i = pubkey_get_npkey(sk->pubkey_algo);
sk->skey[i] = mpi_set_opaque(NULL, data, ndata );
}
else {
csum = 0;
for(i=pubkey_get_npkey(sk->pubkey_algo);
i < pubkey_get_nskey(sk->pubkey_algo); i++ ) {
byte *data;
unsigned int nbits;
csum += checksum_mpi (sk->skey[i]);
buffer = mpi_get_buffer( sk->skey[i], &nbytes, NULL );
cipher_sync (cipher_hd);
assert ( !mpi_is_opaque (sk->skey[i]) );
data = m_alloc (nbytes+2);
nbits = mpi_get_nbits (sk->skey[i]);
assert (nbytes == (nbits + 7)/8);
data[0] = nbits >> 8;
data[1] = nbits;
cipher_encrypt (cipher_hd, data+2, buffer, nbytes);
m_free( buffer );
mpi_free (sk->skey[i]);
sk->skey[i] = mpi_set_opaque (NULL, data, nbytes+2);
}
sk->csum = csum;
}
sk->is_protected = 1;
cipher_close( cipher_hd );
}
}
return rc;
}
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