Securing Name Servers on UNIX
The Domain Name System (DNS) is essential to the functioning of the Internet. The DNS organizes the Internet into distributed hierarchical domains. This hierarchical domain structure provides ease of administration and scalability. It must be kept secure.
In July of 1996, Eugene Kashpureff was able to hijack the www.internic.net (Internic) web site to www.alternic.net (Alternic). As a result, visitors to the Internic net site were directed to the Alternic web site. This was done without authorization from Internic. In late 1997, Kashpureff was arrested in Canada. He pleaded guilty to computer fraud in March of 1998. This incident serves to demonstrate the importance of DNS and the impact that a security attack on the DNS could have on organizations that provide services on the Internet. In today's era of e-commerce and “webification” of everything, DNS security is imperative.
BIND (Berkeley Internet Name Domain) is an implementation of DNS. I will describe here the vulnerabilities discovered in BIND and measures you can take to protect against them. I will assume you are familiar with the workings of the Internet and the DNS architecture.
Two major BIND versions are available today: BIND version 4.9 and the BIND 8 series. Most new development of BIND continues on the 8 series. The latest BIND, version 8.2.1, was released on June 21, 1999, and is available from http://www.isc.org/. In the 4.9 BIND series, the latest version of BIND is 4.9.7.
BIND is usually available as part of most UNIX-based operating systems. However, vendors tend to be behind in adapting to the latest BIND version. You can determine the version of BIND provided by the vendor of your operating system by checking the system log files.
The Internet Software Consortium (ISC) sponsors the development of BIND. The latest version of BIND provides many new features and security enhancements. Chief among these are full support for negative caching, the ability to run multiple virtual DNS servers, bug fixes from previous versions and performance enhancements. Table 1 compares some of the primary differences between BIND 8 and BIND 4.9.7. The ISC states the following about the two different streams of BIND:
BIND version 4 is officially deprecated in favor of BIND version 8 and no additional development will be done on BIND version 4, other than for security-related patches.
The risk to a BIND server may arise from a need for a functionality that can leave the BIND server susceptible to attacks, mis-configuration of BIND and vulnerabilities in BIND. The following vulnerabilities/issues in BIND could be exploited.
This vulnerability exists in all versions of BIND prior to version 4.9.6 and version 8.1.1. It allowed an intruder to cause a victim name server to query a remote name server controlled by the intruder. The remote name server would return bogus information to the victim name server. The bogus information would be cached on the victim name server for a period specified by the TTL field of the record returned by the remote name server. Very simply, this attack allowed the intruder to point the victim name server's host name IP address mapping to an alternate IP address of the intruder's choice. Eugene Kaspureff used cache poisoning to divert the traffic from www.internic.net to www.alternic.net.
BIND versions prior to BIND 4.9.7 and BIND 8.1.2 are vulnerable to this. This vulnerability allowed an intruder to gain root-level access on the victim name server, or just cause the server to crash. Earlier versions of BIND allowed the inverse-query feature (see Glossary). Actually, according to the DNS specification, the inverse queries are optional. By default, the servers are not configured to respond to fake queries. However, BIND 8 can be configured to provide fake responses to inverse queries. It is those servers configured to respond to fake queries that are vulnerable. The inverse-query feature code is disabled (commented out in source code) in BIND versions 4.9.7 and later.
BIND version 4.9.7 and 8.1.2 perform better bounds checking than the previous versions. The previous BIND version could be exploited to access an invalid memory location causing the server to crash. A crash leaves the name server unable to answer queries, which is a denial of service.
|Dynamic DNS—an Object Lesson in Problem Solving||May 21, 2013|
|Using Salt Stack and Vagrant for Drupal Development||May 20, 2013|
|Making Linux and Android Get Along (It's Not as Hard as It Sounds)||May 16, 2013|
|Drupal Is a Framework: Why Everyone Needs to Understand This||May 15, 2013|
|Home, My Backup Data Center||May 13, 2013|
|Non-Linux FOSS: Seashore||May 10, 2013|
- Dynamic DNS—an Object Lesson in Problem Solving
- Making Linux and Android Get Along (It's Not as Hard as It Sounds)
- Using Salt Stack and Vagrant for Drupal Development
- New Products
- A Topic for Discussion - Open Source Feature-Richness?
- Drupal Is a Framework: Why Everyone Needs to Understand This
- Validate an E-Mail Address with PHP, the Right Way
- RSS Feeds
- Readers' Choice Awards
- Tech Tip: Really Simple HTTP Server with Python
2 hours 10 min ago
- Reply to comment | Linux Journal
2 hours 42 min ago
- All the articles you talked
5 hours 6 min ago
- All the articles you talked
5 hours 9 min ago
- All the articles you talked
5 hours 10 min ago
9 hours 35 min ago
- Keeping track of IP address
11 hours 26 min ago
- Roll your own dynamic dns
16 hours 39 min ago
- Please correct the URL for Salt Stack's web site
19 hours 51 min ago
- Android is Linux -- why no better inter-operation
22 hours 6 min ago
Enter to Win an Adafruit Pi Cobbler Breakout Kit for Raspberry Pi
It's Raspberry Pi month at Linux Journal. Each week in May, Adafruit will be giving away a Pi-related prize to a lucky, randomly drawn LJ reader. Winners will be announced weekly.
Fill out the fields below to enter to win this week's prize-- a Pi Cobbler Breakout Kit for Raspberry Pi.
Congratulations to our winners so far:
- 5-8-13, Pi Starter Pack: Jack Davis
- 5-15-13, Pi Model B 512MB RAM: Patrick Dunn
- 5-21-13, Prototyping Pi Plate Kit: Philip Kirby
- Next winner announced on 5-27-13!
Free Webinar: Hadoop
How to Build an Optimal Hadoop Cluster to Store and Maintain Unlimited Amounts of Data Using Microservers
Realizing the promise of Apache® Hadoop® requires the effective deployment of compute, memory, storage and networking to achieve optimal results. With its flexibility and multitude of options, it is easy to over or under provision the server infrastructure, resulting in poor performance and high TCO. Join us for an in depth, technical discussion with industry experts from leading Hadoop and server companies who will provide insights into the key considerations for designing and deploying an optimal Hadoop cluster.
Some of key questions to be discussed are:
- What is the “typical” Hadoop cluster and what should be installed on the different machine types?
- Why should you consider the typical workload patterns when making your hardware decisions?
- Are all microservers created equal for Hadoop deployments?
- How do I plan for expansion if I require more compute, memory, storage or networking?