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Category:   Application (Security)  >   GnuPG (Gnu Privacy Guard) Vendors:   Gnupg.org
(Red Hat Issues Fix for RH Enteprise Linux) GnuPG ElGamal Signature Flaw May Disclose Type 20 ElGamal Private Keys to Remote Users
SecurityTracker Alert ID:  1008448
SecurityTracker URL:  http://securitytracker.com/id/1008448
CVE Reference:   CVE-2003-0971   (Links to External Site)
Date:  Dec 11 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:   Red Hat has released a fix.

Red Hat Enterprise Linux AS (Advanced Server) version 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1AS/en/os/SRPMS/gnupg-1.0.7-13.src.rpm

i386:
Available from Red Hat Network: gnupg-1.0.7-13.i386.rpm

ia64:
Available from Red Hat Network: gnupg-1.0.7-13.ia64.rpm

Red Hat Linux Advanced Workstation 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1AW/en/os/SRPMS/gnupg-1.0.7-13.src.rpm

ia64:
Available from Red Hat Network: gnupg-1.0.7-13.ia64.rpm

Red Hat Enterprise Linux ES version 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1ES/en/os/SRPMS/gnupg-1.0.7-13.src.rpm

i386:
Available from Red Hat Network: gnupg-1.0.7-13.i386.rpm

Red Hat Enterprise Linux WS version 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1WS/en/os/SRPMS/gnupg-1.0.7-13.src.rpm

i386:
Available from Red Hat Network: gnupg-1.0.7-13.i386.rpm

Red Hat Enterprise Linux AS version 3:

SRPMS:
ftp://updates.redhat.com/enterprise/3AS/en/os/SRPMS/gnupg-1.2.1-10.src.rpm

i386:
Available from Red Hat Network: gnupg-1.2.1-10.i386.rpm

ia64:
Available from Red Hat Network: gnupg-1.2.1-10.ia64.rpm

ppc:
Available from Red Hat Network: gnupg-1.2.1-10.ppc.rpm

s390:
Available from Red Hat Network: gnupg-1.2.1-10.s390.rpm

s390x:
Available from Red Hat Network: gnupg-1.2.1-10.s390x.rpm

x86_64:
Available from Red Hat Network: gnupg-1.2.1-10.x86_64.rpm

Red Hat Enterprise Linux ES version 3:

SRPMS:
ftp://updates.redhat.com/enterprise/3ES/en/os/SRPMS/gnupg-1.2.1-10.src.rpm

i386:
Available from Red Hat Network: gnupg-1.2.1-10.i386.rpm

Red Hat Enterprise Linux WS version 3:

SRPMS:
ftp://updates.redhat.com/enterprise/3WS/en/os/SRPMS/gnupg-1.2.1-10.src.rpm

i386:
Available from Red Hat Network: gnupg-1.2.1-10.i386.rpm

ia64:
Available from Red Hat Network: gnupg-1.2.1-10.ia64.rpm

x86_64:
Available from Red Hat Network: gnupg-1.2.1-10.x86_64.rpm

The verification checksums are:

MD5 sum Package Name
b619c30c293094d7dcd18487d8e62a43 2.1AS/en/os/SRPMS/gnupg-1.0.7-13.src.rpm
e7e3e75afd1ccd2267ccc7847c76ebb4 2.1AS/en/os/i386/gnupg-1.0.7-13.i386.rpm
6fb21011ca42ff395b8cfc7dce4c2936 2.1AS/en/os/ia64/gnupg-1.0.7-13.ia64.rpm
b619c30c293094d7dcd18487d8e62a43 2.1AW/en/os/SRPMS/gnupg-1.0.7-13.src.rpm
6fb21011ca42ff395b8cfc7dce4c2936 2.1AW/en/os/ia64/gnupg-1.0.7-13.ia64.rpm
b619c30c293094d7dcd18487d8e62a43 2.1ES/en/os/SRPMS/gnupg-1.0.7-13.src.rpm
e7e3e75afd1ccd2267ccc7847c76ebb4 2.1ES/en/os/i386/gnupg-1.0.7-13.i386.rpm
b619c30c293094d7dcd18487d8e62a43 2.1WS/en/os/SRPMS/gnupg-1.0.7-13.src.rpm
e7e3e75afd1ccd2267ccc7847c76ebb4 2.1WS/en/os/i386/gnupg-1.0.7-13.i386.rpm
a2015b94dc7a8b8b8b24036522f5a7f5 3AS/en/os/SRPMS/gnupg-1.2.1-10.src.rpm
9830e4ba4a1b5eb261e39ae5c9efd2b4 3AS/en/os/i386/gnupg-1.2.1-10.i386.rpm
1f50796a959836602552d5f94590269a 3AS/en/os/ia64/gnupg-1.2.1-10.ia64.rpm
b7728dde4a9b9e864a5993de3b0af8ce 3AS/en/os/ppc/gnupg-1.2.1-10.ppc.rpm
8ffa950e28d01c05a1bf5e3beb462d35 3AS/en/os/s390/gnupg-1.2.1-10.s390.rpm
986220a49e895db43dbf37778613e628 3AS/en/os/s390x/gnupg-1.2.1-10.s390x.rpm
d7fc757e68c14f273c2a1bd5d6a3af8f 3AS/en/os/x86_64/gnupg-1.2.1-10.x86_64.rpm
a2015b94dc7a8b8b8b24036522f5a7f5 3ES/en/os/SRPMS/gnupg-1.2.1-10.src.rpm
9830e4ba4a1b5eb261e39ae5c9efd2b4 3ES/en/os/i386/gnupg-1.2.1-10.i386.rpm
a2015b94dc7a8b8b8b24036522f5a7f5 3WS/en/os/SRPMS/gnupg-1.2.1-10.src.rpm
9830e4ba4a1b5eb261e39ae5c9efd2b4 3WS/en/os/i386/gnupg-1.2.1-10.i386.rpm
1f50796a959836602552d5f94590269a 3WS/en/os/ia64/gnupg-1.2.1-10.ia64.rpm
d7fc757e68c14f273c2a1bd5d6a3af8f 3WS/en/os/x86_64/gnupg-1.2.1-10.x86_64.rpm

Vendor URL:  www.gnupg.org/ (Links to External Site)
Cause:   State error
Underlying OS:  Linux (Red Hat Linux)
Underlying OS Comments:  Red Hat Enterprise Linux 2.1, 3

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:  [RHSA-2003:395-01] Updated gnupg packages disable ElGamal keys


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

- ---------------------------------------------------------------------
                   Red Hat Security Advisory

Synopsis:          Updated gnupg packages disable ElGamal keys
Advisory ID:       RHSA-2003:395-01
Issue date:        2003-12-10
Updated on:        2003-12-10
Product:           Red Hat Enterprise Linux
Keywords:          gnupg elgamal sign encrypt
Cross references:  
Obsoletes:         
CVE Names:         CAN-2003-0971
- ---------------------------------------------------------------------

1. Topic:

Updated gnupg packages are now available for Red Hat Enterprise Linux. 
These updates disable the ability to generate ElGamal keys (used for both
signing and encrypting) and disable the ability to use ElGamal public keys
for encrypting data.

2. Relevant releases/architectures:

Red Hat Enterprise Linux AS (Advanced Server) version 2.1 - i386, ia64
Red Hat Linux Advanced Workstation 2.1 - ia64
Red Hat Enterprise Linux ES version 2.1 - i386
Red Hat Enterprise Linux WS version 2.1 - i386
Red Hat Enterprise Linux AS version 3 - i386, ia64, ppc, s390, s390x, x86_64
Red Hat Enterprise Linux ES version 3 - i386
Red Hat Enterprise Linux WS version 3 - i386, ia64, x86_64

3. Problem description:

GnuPG is a utility for encrypting data and creating digital signatures.

Phong Nguyen identified a severe bug in the way GnuPG creates and uses
ElGamal keys, when those keys are used both to sign and encrypt data.  This
vulnerability can be used to trivially recover the private key.  While the
default behavior of GnuPG when generating keys does not lead to the
creation of unsafe keys, by overriding the default settings an unsafe key
could have been created.

If you are using ElGamal keys, you should revoke those keys immediately.

The packages included in this update do not make ElGamal keys safe to use;
they merely include a patch by David Shaw that disables functions that
would generate or use ElGamal keys.

To determine if your key is affected, run the following command to obtain a
list of secret keys that you have on your secret keyring:

gpg --list-secret-keys

The output of this command includes both the size and type of the keys
found, and will look similar to this example:

/home/example/.gnupg/secring.gpg
- ----------------------------------------------------
sec  1024D/01234567 2000-10-17 Example User <example@example.com>
uid                            Example User <example@example.com>

The key length, type, and ID are listed together, separated by a forward
slash.  In the example output above, the key's type is "D" (DSA, sign
and encrypt).  Your key is unsafe if and only if the key type is "G"
(ElGamal, sign and encrypt).  In the above example, the secret key is safe
to use, while the secret key in the following example is not:

/home/example/.gnupg/secring.gpg
- ----------------------------------------------------
sec  1024G/01234567 2000-10-17 Example User <example@example.com>
uid                            Example User <example@example.com>

For more details regarding this issue, as well as instructions on how to
revoke any keys that are unsafe, refer to the advisory available from the
GnuPG web site:

http://www.gnupg.org/

4. Solution:

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

To update all RPMs for your particular architecture, run:

rpm -Fvh [filenames]

where [filenames] is a list of the RPMs you wish to upgrade.  Only those
RPMs which are currently installed will be updated.  Those RPMs which are
not installed but included in the list will not be updated.  Note that you
can also use wildcards (*.rpm) if your current directory *only* contains the
desired RPMs.

Please note that this update is also available via Red Hat Network.  Many
people find this an easier way to apply updates.  To use Red Hat Network,
launch the Red Hat Update Agent with the following command:

up2date

This will start an interactive process that will result in the appropriate
RPMs being upgraded on your system.

If up2date fails to connect to Red Hat Network due to SSL Certificate 
Errors, you need to install a version of the up2date client with an updated 
certificate.  The latest version of up2date is available from the Red Hat 
FTP site and may also be downloaded directly from the RHN website:

https://rhn.redhat.com/help/latest-up2date.pxt

5. Bug IDs fixed (http://bugzilla.redhat.com/bugzilla for more info):

111345 - CAN-2003-0971 GnuPG ElGamal compromise

6. RPMs required:

Red Hat Enterprise Linux AS (Advanced Server) version 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1AS/en/os/SRPMS/gnupg-1.0.7-13.src.rpm

i386:
Available from Red Hat Network: gnupg-1.0.7-13.i386.rpm

ia64:
Available from Red Hat Network: gnupg-1.0.7-13.ia64.rpm

Red Hat Linux Advanced Workstation 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1AW/en/os/SRPMS/gnupg-1.0.7-13.src.rpm

ia64:
Available from Red Hat Network: gnupg-1.0.7-13.ia64.rpm

Red Hat Enterprise Linux ES version 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1ES/en/os/SRPMS/gnupg-1.0.7-13.src.rpm

i386:
Available from Red Hat Network: gnupg-1.0.7-13.i386.rpm

Red Hat Enterprise Linux WS version 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1WS/en/os/SRPMS/gnupg-1.0.7-13.src.rpm

i386:
Available from Red Hat Network: gnupg-1.0.7-13.i386.rpm

Red Hat Enterprise Linux AS version 3:

SRPMS:
ftp://updates.redhat.com/enterprise/3AS/en/os/SRPMS/gnupg-1.2.1-10.src.rpm

i386:
Available from Red Hat Network: gnupg-1.2.1-10.i386.rpm

ia64:
Available from Red Hat Network: gnupg-1.2.1-10.ia64.rpm

ppc:
Available from Red Hat Network: gnupg-1.2.1-10.ppc.rpm

s390:
Available from Red Hat Network: gnupg-1.2.1-10.s390.rpm

s390x:
Available from Red Hat Network: gnupg-1.2.1-10.s390x.rpm

x86_64:
Available from Red Hat Network: gnupg-1.2.1-10.x86_64.rpm

Red Hat Enterprise Linux ES version 3:

SRPMS:
ftp://updates.redhat.com/enterprise/3ES/en/os/SRPMS/gnupg-1.2.1-10.src.rpm

i386:
Available from Red Hat Network: gnupg-1.2.1-10.i386.rpm

Red Hat Enterprise Linux WS version 3:

SRPMS:
ftp://updates.redhat.com/enterprise/3WS/en/os/SRPMS/gnupg-1.2.1-10.src.rpm

i386:
Available from Red Hat Network: gnupg-1.2.1-10.i386.rpm

ia64:
Available from Red Hat Network: gnupg-1.2.1-10.ia64.rpm

x86_64:
Available from Red Hat Network: gnupg-1.2.1-10.x86_64.rpm



7. Verification:

MD5 sum                          Package Name
- --------------------------------------------------------------------------
b619c30c293094d7dcd18487d8e62a43 2.1AS/en/os/SRPMS/gnupg-1.0.7-13.src.rpm
e7e3e75afd1ccd2267ccc7847c76ebb4 2.1AS/en/os/i386/gnupg-1.0.7-13.i386.rpm
6fb21011ca42ff395b8cfc7dce4c2936 2.1AS/en/os/ia64/gnupg-1.0.7-13.ia64.rpm
b619c30c293094d7dcd18487d8e62a43 2.1AW/en/os/SRPMS/gnupg-1.0.7-13.src.rpm
6fb21011ca42ff395b8cfc7dce4c2936 2.1AW/en/os/ia64/gnupg-1.0.7-13.ia64.rpm
b619c30c293094d7dcd18487d8e62a43 2.1ES/en/os/SRPMS/gnupg-1.0.7-13.src.rpm
e7e3e75afd1ccd2267ccc7847c76ebb4 2.1ES/en/os/i386/gnupg-1.0.7-13.i386.rpm
b619c30c293094d7dcd18487d8e62a43 2.1WS/en/os/SRPMS/gnupg-1.0.7-13.src.rpm
e7e3e75afd1ccd2267ccc7847c76ebb4 2.1WS/en/os/i386/gnupg-1.0.7-13.i386.rpm
a2015b94dc7a8b8b8b24036522f5a7f5 3AS/en/os/SRPMS/gnupg-1.2.1-10.src.rpm
9830e4ba4a1b5eb261e39ae5c9efd2b4 3AS/en/os/i386/gnupg-1.2.1-10.i386.rpm
1f50796a959836602552d5f94590269a 3AS/en/os/ia64/gnupg-1.2.1-10.ia64.rpm
b7728dde4a9b9e864a5993de3b0af8ce 3AS/en/os/ppc/gnupg-1.2.1-10.ppc.rpm
8ffa950e28d01c05a1bf5e3beb462d35 3AS/en/os/s390/gnupg-1.2.1-10.s390.rpm
986220a49e895db43dbf37778613e628 3AS/en/os/s390x/gnupg-1.2.1-10.s390x.rpm
d7fc757e68c14f273c2a1bd5d6a3af8f 3AS/en/os/x86_64/gnupg-1.2.1-10.x86_64.rpm
a2015b94dc7a8b8b8b24036522f5a7f5 3ES/en/os/SRPMS/gnupg-1.2.1-10.src.rpm
9830e4ba4a1b5eb261e39ae5c9efd2b4 3ES/en/os/i386/gnupg-1.2.1-10.i386.rpm
a2015b94dc7a8b8b8b24036522f5a7f5 3WS/en/os/SRPMS/gnupg-1.2.1-10.src.rpm
9830e4ba4a1b5eb261e39ae5c9efd2b4 3WS/en/os/i386/gnupg-1.2.1-10.i386.rpm
1f50796a959836602552d5f94590269a 3WS/en/os/ia64/gnupg-1.2.1-10.ia64.rpm
d7fc757e68c14f273c2a1bd5d6a3af8f 3WS/en/os/x86_64/gnupg-1.2.1-10.x86_64.rpm


These packages are GPG signed by Red Hat for security.  Our key is
available from https://www.redhat.com/security/keys.html

You can verify each package with the following command:
    
    rpm --checksig -v <filename>

If you only wish to verify that each package has not been corrupted or
tampered with, examine only the md5sum with the following command:
    
    md5sum <filename>


8. References:

http://lists.gnupg.org/pipermail/gnupg-announce/2003q4/000276.html
http://lists.gnupg.org/pipermail/gnupg-users/2003-November/020779.html
http://lists.gnupg.org/pipermail/gnupg-announce/2003q4/000277.html
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0971

9. Contact:

The Red Hat security contact is <secalert@redhat.com>.  More contact
details at https://www.redhat.com/solutions/security/news/contact.html

Copyright 2003 Red Hat, Inc.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.7 (GNU/Linux)

iD8DBQE/19/DXlSAg2UNWIIRAvkFAJ9G1H3ybTaZRfCj/chSQLEYZauszQCgi/PD
Z2Kho9a/DjV1dygUW2+cR6I=
=sLY1
-----END PGP SIGNATURE-----

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