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.
Fast/Flexible Linux OS Recovery
On Demand Now
In this live one-hour webinar, learn how to enhance your existing backup strategies for complete disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible full-system recovery solution for UNIX and Linux systems.
Join Linux Journal's Shawn Powers and David Huffman, President/CEO, Storix, Inc.
Free to Linux Journal readers.Register Now!
|Secure Desktops with Qubes: Installation||May 28, 2016|
|CentOS 6.8 Released||May 27, 2016|
|Secure Desktops with Qubes: Introduction||May 27, 2016|
|Chris Birchall's Re-Engineering Legacy Software (Manning Publications)||May 26, 2016|
|ServersCheck's Thermal Imaging Camera Sensor||May 25, 2016|
|Petros Koutoupis' RapidDisk||May 24, 2016|
- Secure Desktops with Qubes: Introduction
- Secure Desktops with Qubes: Installation
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- CentOS 6.8 Released
- The Italian Army Switches to LibreOffice
- Linux Mint 18
- ServersCheck's Thermal Imaging Camera Sensor
- Chris Birchall's Re-Engineering Legacy Software (Manning Publications)
- Petros Koutoupis' RapidDisk
- Oracle vs. Google: Round 2
Until recently, IBM’s Power Platform was looked upon as being the system that hosted IBM’s flavor of UNIX and proprietary operating system called IBM i. These servers often are found in medium-size businesses running ERP, CRM and financials for on-premise customers. By enabling the Power platform to run the Linux OS, IBM now has positioned Power to be the platform of choice for those already running Linux that are facing scalability issues, especially customers looking at analytics, big data or cloud computing.
￼Running Linux on IBM’s Power hardware offers some obvious benefits, including improved processing speed and memory bandwidth, inherent security, and simpler deployment and management. But if you look beyond the impressive architecture, you’ll also find an open ecosystem that has given rise to a strong, innovative community, as well as an inventory of system and network management applications that really help leverage the benefits offered by running Linux on Power.Get the Guide