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Category:   Application (Security)  >   GnuPG (Gnu Privacy Guard) Vendors:   Gnupg.org
(Mandrake Issues Fix) GnuPG ElGamal Signature Flaw May Disclose Type 20 ElGamal Private Keys to Remote Users
SecurityTracker Alert ID:  1008336
SecurityTracker URL:  http://securitytracker.com/id/1008336
CVE Reference:   CVE-2003-0971   (Links to External Site)
Updated:  Dec 2 2003
Original Entry Date:  Nov 28 2003
Impact:   Disclosure of authentication information
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 1.0.2 and later versions
Description:   A vulnerability was reported in GnuPG in the creation of ElGamal keys for digital signature. Keys used for signing can be compromised.

It is reported that Phong Nguyen discovered a flaw that allows a remote user to determine your private key within a few seconds.

In version 1.0.2 (January 2000), the flaw was introduced when the GnuPG code was modified to improve the efficiency of encryption using ElGamal keys. A common factor was used for encrypting and signing. As a result, a remtote user with access to a target user's signature can conduct a cryptographic attack to determine the target user's private key. This flaw reportedly affects only ElGamal sign+encrypt keys (type 20) in GnuPG version 1.0.2 and later.

The vendor reports that ElGamal encrypt-only keys (type 16) are not affected. Also, the DSA keys and RSA keys are not vulnerable, according to the report.

Impact:   A remote user can determine the ElGamal private key.
Solution:   Mandrake has released a fix.

Corporate Server 2.1:
d134c826e4fae506ccde3be7686888bc corporate/2.1/RPMS/gnupg-1.0.7-3.2.C21mdk.i586.rpm
9294c6b3587a3a177b1d7ac57c1a0db2 corporate/2.1/SRPMS/gnupg-1.0.7-3.2.C21mdk.src.rpm

Corporate Server 2.1/x86_64:
7c4be5a2e952dd10c10f9242b91b51de x86_64/corporate/2.1/RPMS/gnupg-1.0.7-3.2.C21mdk.x86_64.rpm
9294c6b3587a3a177b1d7ac57c1a0db2 x86_64/corporate/2.1/SRPMS/gnupg-1.0.7-3.2.C21mdk.src.rpm

Mandrake Linux 9.0:
f4f876cd0988362fba3718450727fd95 9.0/RPMS/gnupg-1.0.7-3.2.90mdk.i586.rpm
a459cb6e80e56562eac4a40a2ece3777 9.0/SRPMS/gnupg-1.0.7-3.2.90mdk.src.rpm

Mandrake Linux 9.1:
cdec75d7675fdb36874e61795800f582 9.1/RPMS/gnupg-1.2.2-1.2.91mdk.i586.rpm
08bba4f56d5d5eb581be7170e058133a 9.1/SRPMS/gnupg-1.2.2-1.2.91mdk.src.rpm

Mandrake Linux 9.1/PPC:
4c41071186f40d9895a1032ced8d0601 ppc/9.1/RPMS/gnupg-1.2.2-1.2.91mdk.ppc.rpm
08bba4f56d5d5eb581be7170e058133a ppc/9.1/SRPMS/gnupg-1.2.2-1.2.91mdk.src.rpm

Mandrake Linux 9.2:
03d66699b92149590b078298063a1744 9.2/RPMS/gnupg-1.2.3-3.1.92mdk.i586.rpm
0f5d1244d156a0b229c0d27e07c67b35 9.2/SRPMS/gnupg-1.2.3-3.1.92mdk.src.rpm

Multi Network Firewall 8.2:
b59a3c9a6c27c8d0c52e7a83d1ca3c75 mnf8.2/RPMS/gnupg-1.0.7-3.2.M82mdk.i586.rpm
d4dbfe3968a94705f7a7e175e00d03c9 mnf8.2/SRPMS/gnupg-1.0.7-3.2.M82mdk.src.rpm

Vendor URL:  www.gnupg.org/ (Links to External Site)
Cause:   State error
Underlying OS:  Linux (Mandriva/Mandrake)
Underlying OS Comments:  9.0, 9.1, 9.2, Corporate Server 2.1, Multi Network Firewall 8.2

Message History:   This archive entry is a follow-up to the message listed below.
Nov 27 2003 GnuPG ElGamal Signature Flaw May Disclose Type 20 ElGamal Private Keys to Remote Users



 Source Message Contents

Subject:  MDKSA-2003:109 - Updated gnupg packages fix vulnerability with ElGamal signing keys


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

 _______________________________________________________________________

                Mandrake Linux Security Update Advisory
 _______________________________________________________________________

 Package name:           gnupg
 Advisory ID:            MDKSA-2003:109
 Date:                   November 28th, 2003

 Affected versions:	 9.0, 9.1, 9.2, Corporate Server 2.1,
			 Multi Network Firewall 8.2
 ______________________________________________________________________

 Problem Description:

 A severe vulnerability was discovered in GnuPG by Phong Nguyen
 relating to ElGamal sign+encrypt keys.  From Werner Koch's email
 message:
 
 "Phong Nguyen identified a severe bug in the way GnuPG creates and uses
 ElGamal keys for signing.  This is a significant security failure
 which can lead to a compromise of almost all ElGamal keys used for
 signing.  Note that this is a real world vulnerability which will
 reveal your private key within a few seconds.
 
 Please *take immediate action and revoke your ElGamal signing keys*.
 Furthermore you should take whatever measures necessary to limit the
 damage done for signed or encrypted documents using that key."
 
 And also:
 
 "Note that the standard keys as generated by GnuPG (DSA and ElGamal
 encryption) as well as RSA keys are NOT vulnerable.  Note also that
 ElGamal signing keys cannot be generated without the use of a special
 flag to enable hidden options and even then overriding a warning
 message about this key type.  See below for details on how to identify
 vulnerable keys."
 
 MandrakeSoft urges any users who use the ElGamal sign+encrypt keys to
 immediately revoke these keys and discontinue use of them.  Updated
 packages are provided that remove the ability to create these keys and
 to create signatures using these keys (thanks to David Shaw for
 writing the patch).
 _______________________________________________________________________

 References:

  http://lists.gnupg.org/pipermail/gnupg-announce/2003q4/000276.html
 ______________________________________________________________________

 Updated Packages:
  
 Corporate Server 2.1:
 d134c826e4fae506ccde3be7686888bc  corporate/2.1/RPMS/gnupg-1.0.7-3.2.C21mdk.i586.rpm
 9294c6b3587a3a177b1d7ac57c1a0db2  corporate/2.1/SRPMS/gnupg-1.0.7-3.2.C21mdk.src.rpm

 Corporate Server 2.1/x86_64:
 7c4be5a2e952dd10c10f9242b91b51de  x86_64/corporate/2.1/RPMS/gnupg-1.0.7-3.2.C21mdk.x86_64.rpm
 9294c6b3587a3a177b1d7ac57c1a0db2  x86_64/corporate/2.1/SRPMS/gnupg-1.0.7-3.2.C21mdk.src.rpm

 Mandrake Linux 9.0:
 f4f876cd0988362fba3718450727fd95  9.0/RPMS/gnupg-1.0.7-3.2.90mdk.i586.rpm
 a459cb6e80e56562eac4a40a2ece3777  9.0/SRPMS/gnupg-1.0.7-3.2.90mdk.src.rpm

 Mandrake Linux 9.1:
 cdec75d7675fdb36874e61795800f582  9.1/RPMS/gnupg-1.2.2-1.2.91mdk.i586.rpm
 08bba4f56d5d5eb581be7170e058133a  9.1/SRPMS/gnupg-1.2.2-1.2.91mdk.src.rpm

 Mandrake Linux 9.1/PPC:
 4c41071186f40d9895a1032ced8d0601  ppc/9.1/RPMS/gnupg-1.2.2-1.2.91mdk.ppc.rpm
 08bba4f56d5d5eb581be7170e058133a  ppc/9.1/SRPMS/gnupg-1.2.2-1.2.91mdk.src.rpm

 Mandrake Linux 9.2:
 03d66699b92149590b078298063a1744  9.2/RPMS/gnupg-1.2.3-3.1.92mdk.i586.rpm
 0f5d1244d156a0b229c0d27e07c67b35  9.2/SRPMS/gnupg-1.2.3-3.1.92mdk.src.rpm

 Multi Network Firewall 8.2:
 b59a3c9a6c27c8d0c52e7a83d1ca3c75  mnf8.2/RPMS/gnupg-1.0.7-3.2.M82mdk.i586.rpm
 d4dbfe3968a94705f7a7e175e00d03c9  mnf8.2/SRPMS/gnupg-1.0.7-3.2.M82mdk.src.rpm
 _______________________________________________________________________

 To upgrade automatically use MandrakeUpdate or urpmi.  The verification
 of md5 checksums and GPG signatures is performed automatically for you.

 A list of FTP mirrors can be obtained from:

  http://www.mandrakesecure.net/en/ftp.php

 All packages are signed by MandrakeSoft for security.  You can obtain
 the GPG public key of the Mandrake Linux Security Team by executing:

  gpg --recv-keys --keyserver www.mandrakesecure.net 0x22458A98

 Please be aware that sometimes it takes the mirrors a few hours to
 update.

 You can view other update advisories for Mandrake Linux at:

  http://www.mandrakesecure.net/en/advisories/

 MandrakeSoft has several security-related mailing list services that
 anyone can subscribe to.  Information on these lists can be obtained by
 visiting:

  http://www.mandrakesecure.net/en/mlist.php

 If you want to report vulnerabilities, please contact

  security_linux-mandrake.com

 Type Bits/KeyID     Date       User ID
 pub  1024D/22458A98 2000-07-10 Linux Mandrake Security Team
  <security linux-mandrake.com>
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.7 (GNU/Linux)

iD8DBQE/x4h+mqjQ0CJFipgRAg1OAKDODFf1SkdO39LjyCFY6SvjCjZJ8wCg7GlT
lman5suxvcMbPKW/gDy2mJE=
=bcUF
-----END PGP SIGNATURE-----

 
 


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