Vulnerability Note VU#925211

Debian and Ubuntu OpenSSL packages contain a predictable random number generator

Overview

A vulnerability in the OpenSSL package included with the Debian GNU/Linux operating system and its derivatives may cause weak cryptographic keys to be generated.

I. Description

A weakness exists in the random number generator used by the OpenSSL package included with the Debian GNU/Linux operating system and derivative systems that causes the generated numbers to be predictable. As a result of this weakness, certain encryption keys are much more common than they should be. This vulnerability affects cryptographic applications that use keys generated by the flawed versions of the OpenSSL package. Affected keys include SSH keys, OpenVPN keys, DNSSEC keys, and key material for use in X.509 certificates and session keys used in SSL/TLS connections. Any of these keys generated using the affected systems on or after 2006-09-17 may be vulnerable. Keys generated with GnuPG or GNUTLS on the affected systems are not vulnerable because these applications use their own random number generators and not the one from the flawed version of OpenSSL.

Note that this vulnerability is specific to Debian, Ubuntu Linux and other Debian-derived operating systems. Other systems can be indirectly affected if weak keys generated by the vulnerable systems are imported into them.

II. Impact

A remote, unauthenticated attacker with minimal knowledge of the vulnerable system and the ability to conduct a brute force attack against an affected application may be able to guess secret key material. Secondary impacts include authenticated access to the system through the affected service or the ability to perform man-in-the-middle attacks.

III. Solution

Apply a patch from the vendor and regenerate key material

Patches have been release by the affected vendors. Users are encouraged to review the Systems Affected section of this document and apply the updates it refers to.

Due to the nature of the flaw, any key material generated by the vulnerable versions of the OpenSSL package should be considered fatally defective. Additionally, all DSA keys ever used on affected Debian systems for signing or authentication purposes should be considered compromised since the Digital Signature Algorithm relies on a secret random value used during signature generation. After the software updates are applied, this key material must be regenerated with the updated version of the software. Vendor-specific instructions for doing this can also be found in the Systems Affected section of this document.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Debian GNU/Linux	Vulnerable	15-May-2008
Ubuntu	Vulnerable	15-May-2008

References

http://www.debian.org/security/2008/dsa-1571
http://www.debian.org/security/2008/dsa-1576
http://security.debian.org/project/extra/dowkd/dowkd.pl.gz
http://www.debian.org/security/key-rollover/
http://metasploit.com/users/hdm/tools/debian-openssl/
http://wiki.debian.org/SSLkeys
http://research.swtch.com/2008/05/lessons-from-debianopenssl-fiasco.html
http://www.links.org/?p=328

Credit

Thanks to Florian Weimer of the Debian security team for reporting this vulnerability. Debian, in turn, credits Luciano Bello with discovering this issue.

This document was written by Chad R Dougherty.

Other Information

Date Public:	2008-05-13
Date First Published:	2008-05-15
Date Last Updated:	2008-06-03
CERT Advisory:
CVE-ID(s):	CVE-2008-0166
NVD-ID(s):	CVE-2008-0166
US-CERT Technical Alerts:
Metric:	7.20
Document Revision:	12

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Produced 2008 by US-CERT, a government organization
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