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gnupg/g10/seckey-cert.c
Werner Koch 019601191a Improved detection of bad/invalid signer keys.
2009-08-06 20:12:00 +00:00

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/* seckey-cert.c - secret key certificate packet handling
* Copyright (C) 1998, 1999, 2000, 2001, 2002,
* 2006, 2009 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 3 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, see <http://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "gpg.h"
#include "util.h"
#include "packet.h"
#include "keydb.h"
#include "cipher.h"
#include "main.h"
#include "options.h"
#include "i18n.h"
#include "status.h"
#include "pkglue.h"
static int
do_check( PKT_secret_key *sk, const char *tryagain_text, int mode,
int *canceled )
{
gpg_error_t err;
byte *buffer;
u16 csum=0;
int i, res;
size_t nbytes;
if( sk->is_protected ) { /* remove the protection */
DEK *dek = NULL;
u32 keyid[4]; /* 4! because we need two of them */
gcry_cipher_hd_t 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_UNU_SECKEY;
}
if( sk->protect.algo == CIPHER_ALGO_NONE )
BUG();
if( openpgp_cipher_test_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(gcry_md_test_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, mode,
tryagain_text, canceled );
if (!dek && canceled && *canceled)
return G10ERR_GENERAL;
err = openpgp_cipher_open (&cipher_hd, sk->protect.algo,
GCRY_CIPHER_MODE_CFB,
(GCRY_CIPHER_SECURE
| (sk->protect.algo >= 100 ?
0 : GCRY_CIPHER_ENABLE_SYNC)));
if (err)
log_fatal ("cipher open failed: %s\n", gpg_strerror (err) );
err = gcry_cipher_setkey (cipher_hd, dek->key, dek->keylen);
if (err)
log_fatal ("set key failed: %s\n", gpg_strerror (err) );
xfree(dek);
save_sk = copy_secret_key( NULL, sk );
gcry_cipher_setiv ( cipher_hd, sk->protect.iv, sk->protect.ivlen );
csum = 0;
if( sk->version >= 4 ) {
int ndata;
unsigned int ndatabits;
byte *p, *data;
u16 csumc = 0;
i = pubkey_get_npkey(sk->pubkey_algo);
assert ( gcry_mpi_get_flag (sk->skey[i], GCRYMPI_FLAG_OPAQUE ));
p = gcry_mpi_get_opaque ( sk->skey[i], &ndatabits );
ndata = (ndatabits+7)/8;
if ( ndata > 1 )
csumc = p[ndata-2] << 8 | p[ndata-1];
data = xmalloc_secure ( ndata );
gcry_cipher_decrypt ( cipher_hd, data, ndata, p, ndata );
gcry_mpi_release (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 {
gcry_md_hd_t h;
if ( gcry_md_open (&h, DIGEST_ALGO_SHA1, 1))
BUG(); /* Algo not available. */
gcry_md_write (h, data, ndata - 20);
gcry_md_final (h);
if (!memcmp (gcry_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);
}
gcry_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++ ) {
if ( gcry_mpi_scan( &sk->skey[i], GCRYMPI_FMT_PGP,
p, ndata, &nbytes))
{
/* Checksum was okay, but not correctly
decrypted. */
sk->csum = 0;
csum = 1;
break;
}
ndata -= nbytes;
p += nbytes;
}
/* Note: at this point ndata should be 2 for a simple
checksum or 20 for the sha1 digest */
}
xfree(data);
}
else {
for(i=pubkey_get_npkey(sk->pubkey_algo);
i < pubkey_get_nskey(sk->pubkey_algo); i++ ) {
byte *p;
size_t ndata;
unsigned int ndatabits;
assert (gcry_mpi_get_flag (sk->skey[i], GCRYMPI_FLAG_OPAQUE));
p = gcry_mpi_get_opaque (sk->skey[i], &ndatabits);
ndata = (ndatabits+7)/8;
assert (ndata >= 2);
assert (ndata == ((p[0] << 8 | p[1]) + 7)/8 + 2);
buffer = xmalloc_secure (ndata);
gcry_cipher_sync (cipher_hd);
buffer[0] = p[0];
buffer[1] = p[1];
gcry_cipher_decrypt (cipher_hd, buffer+2, ndata-2,
p+2, ndata-2);
csum += checksum (buffer, ndata);
gcry_mpi_release (sk->skey[i]);
err = gcry_mpi_scan( &sk->skey[i], GCRYMPI_FMT_PGP,
buffer, ndata, &ndata );
xfree (buffer);
if (err)
{
/* Checksum was okay, but not correctly
decrypted. */
sk->csum = 0;
csum = 1;
break;
}
/* csum += checksum_mpi (sk->skey[i]); */
}
}
gcry_cipher_close ( cipher_hd );
/* Now let's see whether we have used the correct passphrase. */
if( csum != sk->csum ) {
copy_secret_key( sk, save_sk );
passphrase_clear_cache ( keyid, NULL, sk->pubkey_algo );
free_secret_key( save_sk );
return gpg_error (GPG_ERR_BAD_PASSPHRASE);
}
/* The checksum may fail, so we also check the key itself. */
res = pk_check_secret_key ( sk->pubkey_algo, sk->skey );
if( res ) {
copy_secret_key( sk, save_sk );
passphrase_clear_cache ( keyid, NULL, sk->pubkey_algo );
free_secret_key( save_sk );
return gpg_error (GPG_ERR_BAD_PASSPHRASE);
}
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
* If n is negative, disable the key info prompt and make n=abs(n)
*/
int
check_secret_key( PKT_secret_key *sk, int n )
{
int rc = gpg_error (GPG_ERR_BAD_PASSPHRASE);
int i,mode;
if (sk && sk->is_protected && sk->protect.s2k.mode == 1002)
return 0; /* Let the scdaemon handle this. */
if(n<0)
{
n=abs(n);
mode=1;
}
else
mode=0;
if( n < 1 )
n = 3; /* Use the default value */
for(i=0; i < n && gpg_err_code (rc) == GPG_ERR_BAD_PASSPHRASE; i++ ) {
int canceled = 0;
const char *tryagain = NULL;
if (i) {
tryagain = N_("Invalid passphrase; please try again");
log_info (_("%s ...\n"), _(tryagain));
}
rc = do_check( sk, tryagain, mode, &canceled );
if ( gpg_err_code (rc) == GPG_ERR_BAD_PASSPHRASE
&& 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
* -2 indicates a card stub.
* -3 indicates a not-online stub.
*/
int
is_secret_key_protected( PKT_secret_key *sk )
{
return sk->is_protected?
sk->protect.s2k.mode == 1002? -2 :
sk->protect.s2k.mode == 1001? -3 : 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;
size_t nbytes;
u16 csum;
if( !dek )
return 0;
if( !sk->is_protected ) { /* okay, apply the protection */
gcry_cipher_hd_t cipher_hd=NULL;
if ( openpgp_cipher_test_algo ( sk->protect.algo ) ) {
/* Unsupport protection algorithm. */
rc = gpg_error (GPG_ERR_CIPHER_ALGO);
}
else {
print_cipher_algo_note( sk->protect.algo );
if ( openpgp_cipher_open (&cipher_hd, sk->protect.algo,
GCRY_CIPHER_MODE_CFB,
(GCRY_CIPHER_SECURE
| (sk->protect.algo >= 100 ?
0 : GCRY_CIPHER_ENABLE_SYNC))) )
BUG();
if ( gcry_cipher_setkey ( cipher_hd, dek->key, dek->keylen ) )
log_info(_("WARNING: Weak key detected"
" - please change passphrase again.\n"));
sk->protect.ivlen = openpgp_cipher_get_algo_blklen (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 */
gcry_create_nonce (sk->protect.iv, sk->protect.ivlen);
gcry_cipher_setiv (cipher_hd, sk->protect.iv, sk->protect.ivlen);
if( sk->version >= 4 ) {
byte *bufarr[PUBKEY_MAX_NSKEY];
size_t narr[PUBKEY_MAX_NSKEY];
unsigned int 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 (!gcry_mpi_get_flag (sk->skey[i],
GCRYMPI_FLAG_OPAQUE));
if (gcry_mpi_aprint (GCRYMPI_FMT_USG, bufarr+j,
narr+j, sk->skey[i]))
BUG();
nbits[j] = gcry_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 = xmalloc_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];
xfree(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 {
gcry_md_hd_t h;
if (gcry_md_open (&h, GCRY_MD_SHA1, 1))
BUG(); /* Algo not available. */
gcry_md_write (h, data, ndata - 20);
gcry_md_final (h);
memcpy (p, gcry_md_read (h, DIGEST_ALGO_SHA1), 20);
p += 20;
gcry_md_close (h);
sk->csum = csum = 0;
sk->protect.sha1chk = 1;
}
assert( p == data+ndata );
gcry_cipher_encrypt (cipher_hd, data, ndata, NULL, 0);
for (i = pubkey_get_npkey(sk->pubkey_algo);
i < pubkey_get_nskey(sk->pubkey_algo); i++ )
{
gcry_mpi_release (sk->skey[i]);
sk->skey[i] = NULL;
}
i = pubkey_get_npkey(sk->pubkey_algo);
sk->skey[i] = gcry_mpi_set_opaque (NULL, data, ndata*8 );
}
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]);
if (gcry_mpi_aprint (GCRYMPI_FMT_USG, &buffer,
&nbytes, sk->skey[i] ))
BUG();
gcry_cipher_sync (cipher_hd);
assert (!gcry_mpi_get_flag (sk->skey[i],
GCRYMPI_FLAG_OPAQUE));
data = xmalloc (nbytes+2); /* fixme: need xtrymalloc. */
nbits = gcry_mpi_get_nbits (sk->skey[i]);
assert (nbytes == (nbits + 7)/8);
data[0] = nbits >> 8;
data[1] = nbits;
gcry_cipher_encrypt (cipher_hd, data+2, nbytes,
buffer, nbytes);
xfree( buffer );
gcry_mpi_release (sk->skey[i]);
sk->skey[i] = gcry_mpi_set_opaque (NULL,
data, (nbytes+2)*8 );
}
sk->csum = csum;
}
sk->is_protected = 1;
gcry_cipher_close (cipher_hd);
}
}
return rc;
}
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