Advisories

CERT-In Advisory CIAD-2003-0015

Multiple Vulnerabilities in SSL/TLS Implementations

Original Issue Date: October 03, 2003

Severity Rating: Medium

Systems Affected

OpenSSL versions up to and including 0.9.6j and 0.9.7b
Multiple SSL/TLS implementations
SSLeay library

Overview

There exist multiple vulnerabilities in all the implementations of the Secure Sockets Layer SSL and Transport Layer Security TLS . Vulnerabilities arise in the way OpenSSL processes a data format called Abstract Syntax Notation One ASN.1 -- an internationally recognized standard for coding and transmitting complex data structures, and a building block of the digital certificates that make SSL work.

Impact

The impacts of these vulnerabilities vary. In almost all, a remote attacker could cause a denial of service. The vulnerability mentioned in point no. 1, may result in a remote attacker being able to execute arbitrary code.

Description

OpenSSL is an open source toolkit implementing SSL v2/v3 and TLS v1 as well as a general purpose cryptographic library. SSL and TLS are used to provide authentication, encryption and integrity services to many applications such as HTTP. Cryptographic elements used by the protocols, such as X.509 certificates, are represented as ASN.1 objects. In order to encode and decode these objects, ASN.1 parsers are included in many SSL and TLS implementations and cryptographic libraries

The details of these vulnerabilities are discussed below:

Certain ASN.1 encodings that are rejected as invalid by the parser can trigger a bug in the deallocation of the corresponding data structure, corrupting the stack. This can be used as a denial of service attack or allow a remote attacker to execute arbitrary code with the privileges of the process using the OpenSSL library. This issue does not affect OpenSSL 0.9.6.
Unusual ASN.1 tag values can cause an out of bounds read under certain circumstances, resulting in a denial of service vulnerability.
A malformed public key in a certificate will crash the verify code if it is set to ignore public key decoding errors. Public key decode errors are not normally ignored, except for debugging purposes, so this is unlikely to affect production code. Exploitation of an affected application would result in a denial of service vulnerability.
Due to an error in the SSL/TLS protocol handling, a server will parse a client certificate when one is not specifically requested. This by itself is not strictly speaking a vulnerability but it does mean that *all* SSL/TLS servers that use OpenSSL can be attacked using vulnerabilities 1, 2 and 3 even if they don't enable client authentication.

Solution

Upgrade to OpenSSL 0.9.7c or 0.9.6k. Recompile any OpenSSL applications statically linked to OpenSSL libraries. Alternatively, upgrade or apply a patch as directed by the vendor.

Vendor Information

Cisco
http://www.cisco.com/warp/public/707/ cisco-sa- 20030930-SSL.shtml.
IBM - [eServer]
https://app-06.www.ibm.com/servers/resourcelink/lib03020.nsf/pages/securityalerts?OpenDocument&pathID
Novell
http://support.novell.com/security-alerts
SCO
SCO has released an advisory related to this vulnerability
CSSA-2003-SCO.25
SGI
SGI have released an IRIX advisory available at
ftp://patches.sgi.com/support/free/security/advisories/20030904-01-P.asc

References

OpenSSL Security Advisory [30 September 2003]
http://www.openssl.org/news/secadv_20030930.txt

NISCC Vulnerability Advisory 006489/OpenSSL -
http://www.uniras.gov.uk/vuls/2003/006489/openssl.htm

NISCC Vulnerability Advisory 006489/TLS -
http://www.uniras.gov.uk/vuls/2003/006489/tls.htm

ITU ASN.1 documentation -
http://www.itu.int/ITU-T/studygroups/com10/languages/

Disclaimer

The information provided herein is on "as is" basis, without warranty of any kind.

Contact Information

Email: info@cert-in.org.in
Phone: +91-11-2436857

Postal address

Indian Computer Emergency Response Team (CERT-In)
Ministry of Electronics and Information Technology
Government of India
Electronics Niketan
6, CGO Complex, Lodhi Road,
New Delhi - 110 003
India