Living without wires

By on
Living without wires

Is WPA really the answer to the problem of insecure corporate wireless networks? Maybe, but as Rob Buckley discovers, it's not that simple

Almost since its creation, wireless networking has worried CIOs. Unlike Ethernet, wireless networking removes the need for a physical connection to the network, making it far harder to restrict access. Coupled with the flawed WEP protocol used to "secure" initial Wi-Fi networks and it's no surprise that many preferred to ignore wireless networking altogether or fill in the gaps in security with other techniques.

To improve the security – and the image – of wireless networking security, the vendors responsible for Wi-Fi developed a replacement for WEP called WPA. But is it as secure as vendors claim, and is using it as easy as they suggest?

Ask almost any vendor of Wi-Fi hardware whether WPA is secure and you will get more or less the same response: "Analysis says it will take around 2.7 billion years before it's cracked. It's classed by the US government as good enough for top secret protection." And as far as it's possible to tell, those vendors are right. But that's not the whole story.

First, there are two WPA standards, WPA and its successor WPA2 (see panel, p33). WPA was intended as an interim standard designed to patch the holes in WEP until vendors and standards bodies could finalise the specifications for WPA2. WEP had many flaws, with hostile users able to discover the key used to encrypt transmissions relatively easily, change traffic on the network without knowing the key and even create a denial-of-service attack. WPA fixed those flaws relatively painlessly, usually requiring only firmware and software upgrades on clients and access points, rather than an investment in new hardware.

WPA2 improved on WPA's encryption method, but at a slight cost: older hardware did not have the processing power capable of decrypting and encrypting traffic in real-time. However, hardware developed when WPA was already a standard is usually capable of being upgraded to WPA2: vendors knew the likely basis of WPA2's encryption scheme and built-in the necessary processing power from the beginning.

WPA and WPA2 are more secure than their predecessor. Both come in "enterprise" and "personal" versions, with the first offering even more security through authentication to 802.1X servers such as RADIUS. Only WPA-Personal has so far been shown to have any kind of vulnerability, as shown by the coWPAtty passphrase auditing tool, and that is only apparent when using weak passwords.

Instead, the problem is with the implementation of the standards. Although the Wi-Fi alliance does test hardware to ensure it interoperates with other WPA-capable hardware, this testing is often insufficient to ensure true interoperability between all the various components needed for a WPA-encrypted network.

"If you want to ensure compatibility, then buy everything from one vendor," says Tim Ecott of security firm Integralis. "It's a compatibility minefield – problems with different cards, tying into Active Directory, the differences in the EAP protocols, the information exchanged."

Telindus is one of the UK's biggest network builders and has implemented WPA networks such as that used by Westminster Council for its IP CCTV system. James Walker, the head of its wireless and mobility division, has plenty of experience of the problems involved in getting different bits of WPA hardware to work together. "Often, you find things don't work correctly the first time. Usually, people then blame the network, but often it's the user's device or card."

At Surrey University, some users found their connections to the network dropped frequently. Walker's team traced the problem to the fact that the Dell laptops had been imported from the US and had US, rather than European, specifications. "Netgear, Cisco and sometimes Buffalo have a better chance of working. Dells have problems," warns Walker.

He adds that interoperability problems can typically be solved with proper patch management techniques, especially with WPA-enabled networks, rather than WPA2. "Most WEP issues have been resolved. WPA2 is newer than WPA, so fewer bugs have been fixed. But that will change over time."

Another weak point in interoperability is authentication. WPA-Enterprise and WPA2-Enterprise use the EAP framework for passing authentication data. Currently, 40 different protocols fit within EAP. Initially, EAP-TLS was the only EAP that needed a piece of wireless hardware to support for WPA certification. In April 2005, the Wi-Fi Alliance changed this to include four other EAPs: EAP-TTLS, EAP-SIM, EAP-MSCHAPv2 (PEAPv0) and EAP-GTC (PEAPv1). However, the alliance didn't change the certification issued to vendors when it did this. As a result, older hardware does not necessarily support the same authentication mechanisms as newer hardware, despite having WPA certification.

The ability of the hardware to work correctly with older authentication servers may also be a problem. Integralis' Ecott says that while a modern RADIUS server should cause few problems, it's not always a given that an organisation will have anything other than a legacy server, making it harder to ensure it will support the EAPs the organisation would like.

Picking an appropriate EAP mechanism that the organisation can support is also important. The client-side certificates required by EAP-TLS, for example, will necessitate every single device having a certificate installed on it by the IT staff.

Finally, clients might not be able to support WPA and WPA2 encryption. Modern laptops with recent wireless cards should be able to support both natively, but older clients will often need updates, patches and additional software. And laptops are not the only clients that organisations might want to connect to their networks: wireless print servers are increasingly common.

Mobility in the workforce has been spurred on in part by the emergence of smart devices such as mobile phones and PDAs. Many of these contain considerable computing power and their users will often want to use them with the corporate network. Certain sectors, such as retail, may use other kinds of wireless-enabled devices, like barcode scanners, but many such devices might only support WEP encryption or WPA-Personal.

Then there are guests who might want to use the corporate network to access the internet, but whom the company doesn't want to give full authentication details – for reasons of security, support or time.

These flaws are not without solutions, but they introduce levels of complexity that need to be overcome to use WPA. Many vendors have implemented features in their hardware that can overcome some of the technical issues. The most common fix is including virtual LAN and multiple SSID technologies in wireless access points.

"Do you want to have to downgrade the security of your network to consumer level just to use a wireless print server?" asks Michael Marsanu, CTO at Funkwerk Enterprise Communications. "With multiple SSID and VLAN support, one radio point can support up to 32 networks – each of them with different names and different security levels."

An organisation that deploys these technologies can decide which levels of security to support and grant clients access accordingly. A security-free, open network that broadcasts its SSID openly might be made available for visitors to access the internet, but no corporate resources. A WEP-encrypted network with access to a few resources might give access to basic smart devices and printers.

A hidden WPA2-Enterprise network with full RADIUS and EAP authentication might give access to the complete set of corporate resources. As well as giving network access to a greater range of devices, this technique avoids a forced upgrade of all wireless devices. Only devices that require the highest level of access need be upgraded immediately, the rest can be updated progressively or replaced at the end of their lifespans.

Alternatively, it can avoid all wireless worries, suggests SecureTest managing director Ken Munro, by treating all wireless devices as "dirty" and putting them on their own separate VLAN, away from the rest of the network. Users can then log in using remote access technology, so they have the same security wrappers as geographically distant users.

By segmenting access into VLANs, roles can be assigned to users based on their method of access and location. Hardware vendor Bluesocket's head of channel development and strategy, Jim Calderbank, highlights some of the more advanced capabilities in this technology. "You can specify at the point of installation that VLAN100 is the upstairs floor and access hours are between eight and five," he says. "You can stop someone accessing payroll from the canteen."

While including access control groups like this might seem like an increasing management problem, many of the hardware vendors are now using thin access points to centralise management. These have fewer internal management capabilities and are managed from a central controller. When policies need updating, they can be deployed from the central console to all the access points, rather than to each individual access point.

They can also increase security. Jon Green, director of technical marketing at Aruba Networks, says: "We centralise encryption into one central controller. You don't have access keys and don't have to worry about physical access. Somebody can take one of your access points, take it apart, put their own software on it and will still not get any access to the network that they shouldn't have."

Newer access points can also include their own EAP and RADIUS technology. For example, Bluesocket's access points include what Calderbank calls "inner" and "outer" EAPs. If the access point finds itself dealing with a legacy server, it can act as an intermediary between the client device and the RADIUS server, converting between the different EAP types the two systems can negotiate.

Still, with all these problems, is it worth using WPA at all? Many customers of network hardware vendor Cisco think it isn't. When insecurities were discovered in WEP, Cisco developed proprietary additions to WEP, similar to those implemented in WPA, called "Cisco extensions" or CCX (Cisco Compatible extensions).

Cisco senior security advisor Paul King says most Cisco customers are still using WEP with Cisco extensions. "I don't think you get any extra security. There's no big leap you get by going to WPA."

Others disagree, highlighting the fact that sticking with the Cisco extensions effectively locks all users into Cisco hardware for both infrastructure and client. Roger Edgar, product manager at vendor 3Com, argues that while the new versions of the Cisco extensions are very good, they are also very proprietary, despite Cisco's opening of the APIs.

"Our hardware works with everything that obeys the [WPA] standards. What happens when Vodafone launches its Wi-Fi cellular phone? Will it have CCX support?" he says.

One big additional advantage to implementing any form of WPA-Enterprise is that it will force the company to look at 802.1X authentication seriously. Forrester Research analyst Robert Whiteley says that 802.1X isn't just a wireless standard. "A universal authentication and security framework – applied to all networks – allows enterprises to more effectively share their network resources with users," he explains.

"Firms that have implemented 802.1X will be in a much better position to assert that they are appropriately managing network security. While those that stall 802.1X deployments too long risk being left behind with ineffective security and mounting regulatory pressures."

Cisco's enhancements to the WEP standards may be "good enough" for most purposes, but many organisations will want security as tight as possible. That may be through using WPA-Enterprise or WPA2-Enterprise; it may even be through WPA2 layered with a VPN and other security mechanisms. For many organisations, though, the best wireless security will be the one they can manage most easily and that offers the best level of interoperability.

At the moment, the most suitable for many enterprises will be WPA-Enterprise. But with interoperability of WPA2 devices improving and more and more devices supporting the standard, WPA2-Enterprise will soon become the method of choice for wireless encryption.

Copyright © SC Magazine, US edition

Most Read Articles

Log In

|  Forgot your password?