SUSE Security Announcement: gpg signature checking problems (SUSE-SA:2006:014)
Posted on: 03/10/2006 06:22 PM

A security announcement from SUSE

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______________________________________________________________________________

SUSE Security Announcement

Package: gpg
Announcement ID: SUSE-SA:2006:014
Date: Fri, 10 Mar 2006 18:00:00 +0000
Affected Products: SUSE LINUX 10.0
SUSE LINUX 9.3
SUSE LINUX 9.2
SUSE LINUX 9.1
SuSE Linux Desktop 1.0
SuSE Linux Enterprise Server 8
SUSE SLES 9
UnitedLinux 1.0
Vulnerability Type: remote code execution
Severity (1-10): 9
SUSE Default Package: yes
Cross-References: CVE-2006-0049

Content of This Advisory:
1) Security Vulnerability Resolved:
gpg signature verification problem
Problem Description
2) Solution or Work-Around
3) Special Instructions and Notes
4) Package Location and Checksums
5) Pending Vulnerabilities, Solutions, and Work-Arounds:
See SUSE Security Summary Report.
6) Authenticity Verification and Additional Information

______________________________________________________________________________

1) Problem Description and Brief Discussion

The GNU Privacy Guard (GPG) allows crafting a message which could
check out correct using "--verify", but would extract a different,
potentially malicious content when using "-o --batch".

The reason for this is that a .gpg or .asc file can contain multiple
plain text and signature streams and the handling of these streams was
only possible when correctly following the gpg state.

The gpg "--verify" option has been changed to be way more strict than
before and fail on files with multiple signatures/blocks to mitigate
the problem of doing the common --verify checks and -o extraction.

This problem could be used by an attacker to remotely execute code
by using handcrafted YaST Online Patch files put onto a compromised
YOU mirror server and waiting for the user to run YOU.

This problem is tracked by the Mitre CVE ID CVE-2006-0049.

This is a different issue than the gpg signature checking problem for
which we released updates a week ago, tracked by SUSE-SA:2006:013 /
CVE-2006-0455.

2) Solution or Work-Around

There is no known workaround, please install the update packages.

3) Special Instructions and Notes

None.

4) Package Location and Checksums

The preferred method for installing security updates is to use the YaST
Online Update (YOU) tool. YOU detects which updates are required and
automatically performs the necessary steps to verify and install them.
Alternatively, download the update packages for your distribution manually
and verify their integrity by the methods listed in Section 6 of this
announcement. Then install the packages using the command

rpm -Fhv <file.rpm>

to apply the update, replacing <file.rpm> with the filename of the
downloaded RPM package.


x86 Platform:

SUSE LINUX 10.0:
ftp://ftp.suse.com/pub/suse/i386/update/10.0/rpm/i586/gpg-1.4.2-5.4.i586.rpm
17f4db7313fb81477d491cd1de3b4a7c

SUSE LINUX 9.3:
ftp://ftp.suse.com/pub/suse/i386/update/9.3/rpm/i586/gpg-1.4.0-4.4.i586.rpm
781a1f6ee507960c3b7f5ab7b09aae01

SUSE LINUX 9.2:
ftp://ftp.suse.com/pub/suse/i386/update/9.2/rpm/i586/gpg-1.2.5-3.6.i586.rpm
0ac37c5097314b9d65fe3c00552991ba

SUSE LINUX 9.1:
ftp://ftp.suse.com/pub/suse/i386/update/9.1/rpm/i586/gpg-1.2.4-68.13.i586.rpm
2436ccc119ac1af98928536d2b968a3a

Power PC Platform:

SUSE LINUX 10.0:
ftp://ftp.suse.com/pub/suse/i386/update/10.0/rpm/ppc/gpg-1.4.2-5.4.ppc.rpm
7da97d12baf4aa28e307affa9ccaa2ad

x86-64 Platform:

SUSE LINUX 10.0:
ftp://ftp.suse.com/pub/suse/i386/update/10.0/rpm/x86_64/gpg-1.4.2-5.4.x86_64.rpm
490728e89c6564ac1e0b679012a89a42

SUSE LINUX 9.3:
ftp://ftp.suse.com/pub/suse/i386/update/9.3/rpm/x86_64/gpg-1.4.0-4.4.x86_64.rpm
f258e8971ef2eb171907bbc426e15893

SUSE LINUX 9.2:
ftp://ftp.suse.com/pub/suse/i386/update/9.2/rpm/x86_64/gpg-1.2.5-3.6.x86_64.rpm
3e59895b7bed858997bdbc49aece5644

SUSE LINUX 9.1:
ftp://ftp.suse.com/pub/suse/x86_64/update/9.1/rpm/x86_64/gpg-1.2.4-68.13.x86_64.rpm
6369420f068f5d935bbc01f4798f2f20

Sources:

SUSE LINUX 10.0:
ftp://ftp.suse.com/pub/suse/i386/update/10.0/rpm/src/gpg-1.4.2-5.4.src.rpm
a4ee567384c8744bafc59c19ed89669e

SUSE LINUX 9.3:
ftp://ftp.suse.com/pub/suse/i386/update/9.3/rpm/src/gpg-1.4.0-4.4.src.rpm
2d392b6698c4a9bb5f2b54aa51b53405

SUSE LINUX 9.2:
ftp://ftp.suse.com/pub/suse/i386/update/9.2/rpm/src/gpg-1.2.5-3.6.src.rpm
1cb53598e1a3c6d31aefc69c2ea18f37

SUSE LINUX 9.1:
ftp://ftp.suse.com/pub/suse/i386/update/9.1/rpm/src/gpg-1.2.4-68.13.src.rpm
91f82734783f307bf64a1728dbcddd79
ftp://ftp.suse.com/pub/suse/x86_64/update/9.1/rpm/src/gpg-1.2.4-68.13.src.rpm
117ec3bfb057b88b637355db64c74723

Our maintenance customers are notified individually. The packages are
offered for installation from the maintenance web:

http://support.novell.com/cgi-bin/search/searchtid.cgi?psdb/a78b647fae6fd03f11da9c538433f9c8.html
______________________________________________________________________________

5) Pending Vulnerabilities, Solutions, and Work-Arounds:

See SUSE Security Summary Report.
______________________________________________________________________________

6) Authenticity Verification and Additional Information

- Announcement authenticity verification:

SUSE security announcements are published via mailing lists and on Web
sites. The authenticity and integrity of a SUSE security announcement is
guaranteed by a cryptographic signature in each announcement. All SUSE
security announcements are published with a valid signature.

To verify the signature of the announcement, save it as text into a file
and run the command

gpg --verify <file>

replacing <file> with the name of the file where you saved the
announcement. The output for a valid signature looks like:

gpg: Signature made <DATE> using RSA key ID 3D25D3D9
gpg: Good signature from "SuSE Security Team <security@suse.de>"

where <DATE> is replaced by the date the document was signed.

If the security team's key is not contained in your key ring, you can
import it from the first installation CD. To import the key, use the
command

gpg --import gpg-pubkey-3d25d3d9-36e12d04.asc

- Package authenticity verification:

SUSE update packages are available on many mirror FTP servers all over the
world. While this service is considered valuable and important to the free
and open source software community, the authenticity and the integrity of
a package needs to be verified to ensure that it has not been tampered
with.

There are two verification methods that can be used independently from
each other to prove the authenticity of a downloaded file or RPM package:

1) Using the internal gpg signatures of the rpm package
2) MD5 checksums as provided in this announcement

1) The internal rpm package signatures provide an easy way to verify the
authenticity of an RPM package. Use the command

rpm -v --checksig <file.rpm>

to verify the signature of the package, replacing <file.rpm> with the
filename of the RPM package downloaded. The package is unmodified if it
contains a valid signature from build@suse.de with the key ID 9C800ACA.

This key is automatically imported into the RPM database (on
RPMv4-based distributions) and the gpg key ring of 'root' during
installation. You can also find it on the first installation CD and at
the end of this announcement.

2) If you need an alternative means of verification, use the md5sum
command to verify the authenticity of the packages. Execute the command

md5sum <filename.rpm>

after you downloaded the file from a SUSE FTP server or its mirrors.
Then compare the resulting md5sum with the one that is listed in the
SUSE security announcement. Because the announcement containing the
checksums is cryptographically signed (by security@suse.de), the
checksums show proof of the authenticity of the package if the
signature of the announcement is valid. Note that the md5 sums
published in the SUSE Security Announcements are valid for the
respective packages only. Newer versions of these packages cannot be
verified.

- SUSE runs two security mailing lists to which any interested party may
subscribe:

suse-security@suse.com
- General Linux and SUSE security discussion.
All SUSE security announcements are sent to this list.
To subscribe, send an e-mail to
<suse-security-subscribe@suse.com>.

suse-security-announce@suse.com
- SUSE's announce-only mailing list.
Only SUSE's security announcements are sent to this list.
To subscribe, send an e-mail to
<suse-security-announce-subscribe@suse.com>.

For general information or the frequently asked questions (FAQ),
send mail to <suse-security-info@suse.com> or
<suse-security-faq@suse.com>.

=====================================================================
SUSE's security contact is <security@suse.com> or <security@suse.de>.
The <security@suse.de> public key is listed below.
=====================================================================
______________________________________________________________________________

The information in this advisory may be distributed or reproduced,
provided that the advisory is not modified in any way. In particular, the
clear text signature should show proof of the authenticity of the text.

SUSE Linux Products GmbH provides no warranties of any kind whatsoever
with respect to the information contained in this security advisory.

Type Bits/KeyID Date User ID
pub 2048R/3D25D3D9 1999-03-06 SuSE Security Team <security@suse.de>
pub 1024D/9C800ACA 2000-10-19 SuSE Package Signing Key <build@suse.de>

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