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Disable the "quick check" bytes for PK decryptions. This is in

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regards to the Mister and Zuccherato attack on OpenPGP CFB mode.
This commit is contained in:
David Shaw 2005-02-10 04:11:35 +00:00
parent 658d1e7302
commit 4df22ba030
5 changed files with 25 additions and 6 deletions
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9
g10/ChangeLog
View File

@ -1,3 +1,12 @@
2005-02-09 David Shaw <dshaw@jabberwocky.com>
* mainproc.c (proc_symkey_enc): Set a flag to indicate that a
particular session key came from a passphrase and not a PK.
* encr-data.c (decrypt_data): Use it here to turn off the "quick
check" bytes for PK decryptions. This is in regards to the Mister
and Zuccherato attack on OpenPGP CFB mode.
2004-11-29 David Shaw <dshaw@jabberwocky.com>
* getkey.c (parse_key_usage): New function to parse out key usage

6
g10/encr-data.c
View File

@ -1,5 +1,5 @@
/* encr-data.c - process an encrypted data packet
* Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
* Copyright (C) 1998, 1999, 2000, 2001, 2005 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
@ -120,7 +120,9 @@ decrypt_data( void *procctx, PKT_encrypted *ed, DEK *dek )
cipher_sync( dfx.cipher_hd );
p = temp;
/* log_hexdump( "prefix", temp, nprefix+2 ); */
if( p[nprefix-2] != p[nprefix] || p[nprefix-1] != p[nprefix+1] ) {
if( dek->symmetric
&& (p[nprefix-2] != p[nprefix] || p[nprefix-1] != p[nprefix+1]) )
{
rc = G10ERR_BAD_KEY;
goto leave;
}

6
g10/mainproc.c
View File

@ -1,6 +1,6 @@
/* mainproc.c - handle packets
* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003,
* 2004 Free Software Foundation, Inc.
* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
* 2005 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
@ -317,6 +317,8 @@ proc_symkey_enc( CTX c, PACKET *pkt )
c->dek = passphrase_to_dek( NULL, 0, algo, &enc->s2k, 0, NULL, NULL );
if(c->dek)
{
c->dek->symmetric=1;
/* 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

4
include/ChangeLog
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@ -1,3 +1,7 @@
2005-02-09 David Shaw <dshaw@jabberwocky.com>
* cipher.h: Add a flag for a symmetric DEK.
2004-11-29 David Shaw <dshaw@jabberwocky.com>
* cipher.h: Add PUBKEY_USAGE_UNKNOWN.

4
include/cipher.h
View File

@ -1,5 +1,6 @@
/* cipher.h
* Copyright (C) 1998, 1999, 2000, 2001, 2003 Free Software Foundation, Inc.
* Copyright (C) 1998, 1999, 2000, 2001, 2003,
* 2005 Free Software Foundation, Inc.
*
* This file is part of GNUPG.
*
@ -76,6 +77,7 @@ typedef struct {
int keylen;
int algo_info_printed;
int use_mdc;
int symmetric;
byte key[32]; /* this is the largest used keylen (256 bit) */
} DEK;