Beyond Passport Vulnerabilities

Little more than a year ago, a company that I'm involved with found a serious flaw with Microsoft Passport.

Microsoft Passport, for anyone not in the know, is Microsoft's highly promoted identity management and single sign-on system. Instead of having one password for the Microsoft Developer Network, another password for Hotmail and another password for Microsoft Messenger, all of these services are tied together with a single common database. Log in to one system, and you've logged in to them all. In theory, this makes the overall process easier for users, since there is only one ID and password to remember, and more secure, since it is easier to debug and audit one system as opposed to many.

Microsoft has adopted Passport internally for most of its products that need to identify users - things such as Windows Media Player. Microsoft has also encouraged other companies to adopt Passport as their back-end authentication system. The biggest company that has jumped onboard so far is eBay, which allows you to sign in using either an eBay ID or a Passport ID.

The problem that the company discovered had to do with the way the Windows XP Registration Wizard used Microsoft Passport to register new copies of Windows when they were first loaded. Instead of communicating with the Passport servers over an encrypted SSL channel, as Microsoft claimed, much of the information was being sent without encryption.

Because Passport is so widely used, the bug was significant. By sniffing the packets on a local area network or an ISP, an attacker could learn the ID and password of any person registering a new copy of Windows XP. What's more, because the registration was done in a Wizard program - rather than in a traditional Web browser - there was no telltale "https," meaning there was no easy way for people to know the information was being sent without encryption.

Passport vulnerabilities have been big news in the past: People who have found them have made the front page of The New York Times. Microsoft then scrambled to fix the problem, while individuals and organizations using the system were left in the lurch. The problem, of course, is that it's hard to stop using Passport. But once the vulnerability is known, the black hats are free to start exploiting it. And once they know where to look, more vulnerabilities might be found.

Bug hunters weren't always so fast to disclose vulnerabilities. When I started writing about computer security 15 years ago, such disclosures were widely seen as irresponsible and dangerous. Back then, newly discovered vulnerabilities were shared with a few trusted security professionals and communicated to the vendor or software developer. The idea was to give those most affected the opportunity to immediately protect themselves and give the company time to develop a fix before the problem was widely known. Frequently there was no "patch" issued at all; the fix for the security problem was simply folded into the next software release.

The Problem with Selective Disclosure

There was just one problem with this careful approach to vulnerability disclosure: Many security vulnerabilities never got fixed at all. Uninformed that the new releases actually contained security fixes, many users didn't bother upgrading - especially users running mission-critical systems that couldn't afford any downtime. Even worse, many software vendors simply didn't fix the security problems that were brought to their attention. After all, why should they? The typical application or operating system has many security vulnerabilities - some of which are known publicly, some of which are known internally and most of which are undiscovered. Why fix a vulnerability that's being kept secret?

As the 1990s unfolded, we learned another reason why selective disclosure didn't work: Increasingly, the people who were discovering security vulnerabilities weren't part of the privileged cabal of computer security researchers and practitioners; they were students, "reformed hackers," independent consultants and even journalists. Time and again, I would hear stories of people who had sent e-mail to a company, reporting a vulnerability they had discovered and then got nothing back, not even a "thank you."

How frustrating. And, as far as the companies were concerned, how tremendously shortsighted.

Thus was born the idea of full disclosure. Mailing lists such as Bugtraq, the sole purpose of which was to allow this new breed of researchers to exchange red-hot vulnerability information, sprung into existence. Computer vendors were welcome to monitor Bugtraq to learn about vulnerabilities in their products - or in the products of their competitors. Of course, the bad guys subscribed to Bugtraq as well - so, too, did a number of highly placed journalists. Thus began the era of disclosures being published on the front page of newspapers, followed by hectic days of patch-or-be-hacked. And all too often, the important disclosures were almost invariably followed by a new round of computer worms or viruses that took advantage of the disclosures.

Disclosures that showed up on Bugtraq weren't just about new buffer overflows; sometimes the bugs were with e-commerce shopping cart software - bugs that would allow a knowledgeable attacker to get products for free, or even to execute commands on the shopping cart's server and steal credit card numbers. The most prestige went to people who posted notices with so-called "exploit scripts," usually a small program that both demonstrated the bug and allowed an attacker to break in to the remote system.

In many cases, there was no obvious public interest served in the public disclosure. Sure, the person who found the bug got credit, but merchants relying on the products were frequently hurt. This was evident when the exploits discovered were with orphaned products made by companies that were having financial problems or had gone out of business. Yes, the merchants relying on these products need to find solutions. But widely posting such vulnerabilities probably did more harm than good.

The Importance of Full Disclosure

These days the pendulum is swinging toward a middle ground called responsible disclosure. People and companies that find security vulnerabilities are supposed to notify the company in question about their discovery and start a clock. The company has 30 days to confirm the vulnerability, come up with a patch and distribute that patch to its users. If the company isn't responsive, the theory goes, then the bug hunter has not just a right but a duty to publicly disclose the vulnerability in an effort to both light a fire under the vendor and warn users.

These guidelines have been agreed upon by a consortium called the Organization for Internet Safety (OIS, www.oisafety.org). The consortium includes software publishers such as Microsoft and The SCO Group and bug-hunters such as @Stake, Foundstone, Internet Security Systems and Symantec. The hope is that agreed-upon ground rules should bring stability to the hectic world of vulnerability disclosure.

The whole question of vulnerability disclosure is one that most CSOs will have to wrestle with from time to time. The most obvious reason is that a CSO needs to know when new vulnerabilities are disclosed in products that his organization is using. For this reason, it makes sense to have at least one person in your shop monitoring mailing lists such as Bugtraq and Full-Disclosure. The person should also do regular Web searches of product names and release numbers, just to keep tabs on the "chatter" surrounding your organization's infrastructure investment.

But another reason that disclosure protocols affect CSOs is that a CSO is likely to encounter security vulnerabilities as well. In these cases, the CSO needs to know what to do with this information - whom to tell, how to tell and how to manage the flow of information.

Follow Disclosure Guidelines

It makes good sense for CSOs to be familiar with the OIS disclosure guidelines. Although nothing makes these guidelines sacrosanct, they do reflect a lot of hard work from respected people and organizations familiar with disclosure problems. If I were CSO at a major corporation, I would be hard-pressed to find a reason to implement a policy that was fundamentally different from what the OIS is proposing.

That's what my company did: Following the responsible disclosure guidelines, we contacted Microsoft. Following the guidelines, the company took us quite seriously. In fact, Microsoft said the problem was a minor configuration on one of the Passport Web servers. A few days later, the problem was fixed. We didn't get any glory, but we received a very nice box of Microsoft warm-up jackets in the mail as a kind of tangible "thank you."

It's important to remember that the disclosed vulnerabilities represent only a tiny fraction of the vulnerabilities that are in any given piece of software. Any program that's sufficiently complex will have security problems. Ultimately, what makes a security disclosure something that you need to act upon is that other people know about it. You will always have vulnerabilities. If nobody knows about them, you're relatively safe.

Isn't that a comfortable thought?

Simson Garfinkel, CISSP, is a technology writer in the Boston area.

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