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* mainproc.c (symkey_decrypt_sesskey): There is no way to tell the

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difference here between a bad passphrase and a cipher algorithm that we
don't have, so use a error message that makes that clear. Use the actual
list of ciphers when checking whether a cipher is invalid.  Return error
if the decrypted cipher algorithm is invalid. (proc_symkey_enc): In a
mixed passphrase/pk message, if a valid dek already exists from decrypting
via pk, do not try to process the passphrase. (proc_symkey_enc): Indicate
when we're decrypting a session key as opposed to decrypting data.  If a
passphrase is invalid, discard the dek so we'll keep trying.
This commit is contained in:
David Shaw 2003-10-26 02:31:48 +00:00
parent 5c67438a67
commit ea4d713e88
2 changed files with 69 additions and 25 deletions
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15
g10/ChangeLog
View File

@ -1,3 +1,18 @@
2003-10-25 David Shaw <dshaw@jabberwocky.com>
* mainproc.c (symkey_decrypt_sesskey): There is no way to tell the
difference here between a bad passphrase and a cipher algorithm
that we don't have, so use a error message that makes that clear.
Use the actual list of ciphers when checking whether a cipher is
invalid. Return error if the decrypted cipher algorithm is
invalid.
(proc_symkey_enc): In a mixed passphrase/pk message, if a valid
dek already exists from decrypting via pk, do not try to process
the passphrase.
(proc_symkey_enc): Indicate when we're decrypting a session key as
opposed to decrypting data. If a passphrase is invalid, discard
the dek so we'll keep trying.
2003-10-16 David Shaw <dshaw@jabberwocky.com>
* g10.c (main): Fix --export-all do actually do something

79
g10/mainproc.c
View File

@ -1,5 +1,6 @@
/* mainproc.c - handle packets
* Copyright (C) 1998,1999,2000,2001,2002,2003 Free Software Foundation, Inc.
* Copyright (C) 1998, 1999, 2000, 2001, 2002,
* 2003 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
@ -238,8 +239,8 @@ add_signature( CTX c, PACKET *pkt )
return 1;
}
static void
symkey_decrypt_sesskey( DEK *dek, byte *sesskey, size_t slen )
static int
symkey_decrypt_seskey( DEK *dek, byte *seskey, size_t slen )
{
CIPHER_HANDLE hd;
int n;
@ -247,28 +248,35 @@ symkey_decrypt_sesskey( DEK *dek, byte *sesskey, size_t slen )
if ( slen < 17 || slen > 33 ) {
log_error ( _("weird size for an encrypted session key (%d)\n"),
(int)slen);
return;
return G10ERR_BAD_KEY;
}
hd = cipher_open( dek->algo, CIPHER_MODE_CFB, 1 );
cipher_setkey( hd, dek->key, dek->keylen );
cipher_setiv( hd, NULL, 0 );
cipher_decrypt( hd, sesskey, sesskey, slen );
cipher_decrypt( hd, seskey, seskey, slen );
cipher_close( hd );
/* check first byte (the cipher algo) */
if ( sesskey[0] > 10 ) {
log_error ( _("invalid symkey algorithm detected (%d)\n"),
sesskey[0] );
return;
}
n = cipher_get_keylen (sesskey[0]) / 8;
if(check_cipher_algo(seskey[0]))
{
/* There is no way to tell the difference here between a bad
passphrase and a cipher algorithm that we don't have. */
log_error(_("bad passphrase or unknown cipher algorithm (%d)\n"),
seskey[0]);
if(seskey[0]==CIPHER_ALGO_IDEA)
idea_cipher_warn(0);
return G10ERR_PASSPHRASE;
}
n = cipher_get_keylen (seskey[0]) / 8;
if (n > DIM(dek->key))
BUG ();
/* now we replace the dek components with the real session key
to decrypt the contents of the sequencing packet. */
dek->keylen = cipher_get_keylen( sesskey[0] ) / 8;
dek->algo = sesskey[0];
memcpy( dek->key, sesskey + 1, dek->keylen );
dek->keylen = cipher_get_keylen( seskey[0] ) / 8;
dek->algo = seskey[0];
memcpy( dek->key, seskey + 1, dek->keylen );
/*log_hexdump( "thekey", dek->key, dek->keylen );*/
return 0;
}
static void
@ -279,26 +287,47 @@ proc_symkey_enc( CTX c, PACKET *pkt )
enc = pkt->pkt.symkey_enc;
if (!enc)
log_error ("invalid symkey encrypted packet\n");
else {
else if(!c->dek)
{
int algo = enc->cipher_algo;
const char *s;
const char *s = cipher_algo_to_string (algo);
s = cipher_algo_to_string (algo);
if( s )
log_info(_("%s encrypted data\n"), s );
{
if(enc->seskeylen)
log_info(_("%s encrypted session key\n"), s );
else
log_info(_("%s encrypted data\n"), s );
}
else
log_info(_("encrypted with unknown algorithm %d\n"), algo );
log_info(_("encrypted with unknown algorithm %d\n"), algo );
c->last_was_session_key = 2;
if ( opt.list_only )
goto leave;
c->dek = passphrase_to_dek( NULL, 0, algo, &enc->s2k, 0, NULL, NULL );
if (c->dek)
c->dek->algo_info_printed = 1;
if ( c->dek && enc->seskeylen )
symkey_decrypt_sesskey( c->dek, enc->seskey, enc->seskeylen );
}
leave:
if(c->dek)
{
/* FIXME: This doesn't work perfectly if a symmetric key
comes before a public key in the message - if the user
doesn't know the passphrase, then there is a chance
that the "decrypted" algorithm will happen to be a
valid one, which will make the returned dek appear
valid, so we won't try any public keys that come
later. */
if(enc->seskeylen)
{
if(symkey_decrypt_seskey(c->dek, enc->seskey, enc->seskeylen))
{
m_free(c->dek);
c->dek=NULL;
}
}
else
c->dek->algo_info_printed = 1;
}
}
leave:
free_packet(pkt);
}