Paranoid Penguin - Linux Security Challenges 2010

Security challenges and worries for 2010: we live in interesting times indeed!
Web Application Security and SSL/TLS Weaknesses

If Internet security is a war, Web applications surely constitute the front line. Nothing has changed the way we interact with computers, and the places from which we interact with them, like the World Wide Web—that is, the use of Web browsers to access data and even entire networks that are mediated by Web servers. In fact, the term World Wide Web is all but obsolete. The Web is now so ubiquitous, it's become synonymous with the Internet and even to some extent with user interface.

Web browsers now do things that used to be done by entire operating systems. Whereas the primary function of Web browsers used to be to format and display data correctly (Web pages originally being, in real terms, brochures with text, images and links to other pages), for some time now, we've used our browsers to download and execute code transparently. This code can be as simple as a script that takes form data from us, such as an on-line order form, and transmits it back to the server. Or, it can be as complex as an entire remote-desktop application that lets us control a computer on the other side of the world.

Most of the same things an attacker might attempt to subvert in an operating system, therefore, are now worth attempting against a Web browser. In the world of OS security, we worry about viruses—executables that end users might be tricked into running that change system behavior or steal data on the system. In the world of browser security, we worry about hostile Web sites—hostile Web content that can change browser behavior or steal data the browser is processing or has stored on the system.

And, that's just on the client side of the Web application equation! On the server side, we worry not only about hostile Web sites, but also about flaws in our own Web applications that might allow attackers to gain unauthorized access to back-end systems and data, or to attack other users.

What about SSL/TLS? Doesn't that provide a reliable means of cryptographically signing and verifying active content (code), authenticating transactions and preventing eavesdropping? Obviously, yes. It does so well enough for most of us to shop on-line, do on-line banking and so forth, with a reasonable level of safety and confidence. However, as I reported in my November 2009 DEFCON column, there has been a marked increase lately in man-in-the-middle attacks against SSL/TLS-protected transactions.

Some of these attacks exploit the ways commercially signed digital certificates are issued, maintained and verified by major issuers, such as VeriSign. That is, they exploit weaknesses in commercial public key infrastructures. Others exploit the ways Web servers and browsers handle SSL/TLS functions and the ways they alert (or don't alert) end users of suspicious behavior.

The good news is the actual cryptosystems on which SSL/TLS is built remain sound. Most of these problems stem from the way Web server and browser developers implement them (less so Web application developers) and the way large Certificate Authorities manage certificates. On the one hand, the server/browser development and PKI communities have their work cut out for them in figuring out how to keep SSL/TLS mechanisms transparent enough for ordinary users to accept and have success with, while fixing these new, serious security gaps. Even getting those communities to acknowledge their respective responsibilities and roles in fixing these issues is a big challenge, and it's not at all clear that they have done or will do so.

But, at least the suite of algorithms and other systems comprising TLS itself is sound. This is a solvable problem!

Cloud Computing

As Internet connectivity has gotten faster, cheaper and more ubiquitous, people have begun to question the need for relying on local computing power and storage, if so much of one's daily computing experience depends so heavily on Internet connectivity anyhow. If your major applications are all Internet applications, why not run them from over the Internet, on remote servers rather than your local CPU or on your local IT infrastructure?

Why not subscribe to a framework in which external providers host enormous farms of servers and storage arrays on which anybody can host virtual servers running massively multiuser on-line applications? Heck, why not just use applications written and maintained by the provider? Should end users even care where and how these applications are being run or who wrote them in the first place?

This is the promise of cloud computing—not just the major systems in your data center, but the data center itself—from the floor to which the racks are bolted upward to the applications running on top of it all—can become someone else's problem to maintain, for much cheaper than maintaining any of it yourself. All you need is a bunch of users with ordinary desktop systems (or Netbooks, for that matter) and Internet connectivity.

Maybe I've been a network engineer for too long, but I have a little trouble seeing the appeal of being completely dependent on network connectivity to do all my work. Even though I don't do much computing off-line nowadays, I certainly like to think I could. (I definitely would have written this article much faster without the distraction of an open browser window!)

My real problem with cloud computing, however, is the difficulty of protecting data that is not just flowing through, but being processed and stored by, applications owned and maintained by someone else on hardware and bandwidth completely outside my control. Frankly, I'm amazed that in an era when identity theft is the single-most quickly growing type of computer crime, any organization would be in such a big hurry to put such dense concentrations of its critical data in the hands of strangers.

Do I think cloud computing is a boondoggle? Not at all, but my attitude is the same as with IT outsourcing in general. It probably makes sense for certain applications used by certain organizations, but I think the whole concept is being grossly oversold, and I think people are overlooking substantial trade-offs and hidden costs, both operational- and security-related.


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