Sony's PS3 DRM Cracked

Anyone who pays any attention to DRM will extrapolate the general principle:

You can never prevent an end-user who has physical control of a device from breaking any DRM scheme you can invent.

Sony just learned their DRM lesson (again).  I'm sure that people at Sony already know this principle, but some "suit" tells the engineers to "do something about the problem" so they implement a technical speed bump. That's all it is and will ever be.

Finally a Safe Hello World

It's very common for Hello World example apps in textbooks or other educational literature to promote insecure software building practices right out of the gate.  What a breath of fresh air to see the Microsoft MVC folks safely HTML encoding (to avoid XSS) in their MVC4 Hello World application!

Protecting Cars from Viruses

Reuters is running a story that should amuse any computer security professional: Experts hope to shield cars from computer viruses.

An excerpt:

Intel's McAfee unit, which is best known for software that fights PC viruses, is one of a handful of firms that are looking to protect the dozens of tiny computers and electronic communications systems that are built into every modern car.

It's scary business. Security experts say that automakers have so far failed to adequately protect these systems, leaving them vulnerable to hacks by attackers looking to steal cars, eavesdrop on conversations, or even harm passengers by causing vehicles to crash.

Our guess is that when cars get to the point that they drive themselves, those who understand how malware works-- and more important: how undeniably complicated modern software and its hardware architecture can be-- will start donning a pair of Converse Chuck Taylors and resemble a modern Luddite by driving themselves, a la Will Smith in I, Robot.

When you look at the statistics, you are far more likely to get injured or die in a car accident than you are in nearly any other security risk you face in your daily life.  Even with the vast skies being what they are, and the regulations on the airlines industry and their pilots, it's not possible to keep air travel 100% safe, though it's safer than driving (once you get past the TSA checkpoint).

Computerized, self-driving cars may improve (emphasis on "may") safety stats; however, not if their software landscape looks like anything else we operate with a CPU in it these days.  There are agencies with an operating budget larger than the GDP of several nations that are terrified about the possibility of malware injected into things like military aircraft or missile guidance systems.  Given that, how in the world is an automobile for ~$20K (which is at most 1% of the price tag of the military's concerns) ever going to be 100% free of malware?  Simple: it won't be.

Toyota Motor Corp, the world's biggest automaker, said it was not aware of any hacking incidents on its cars.

"They're basically designed to change coding constantly. I won't say it's impossible to hack, but it's pretty close," said Toyota spokesman John Hanson. [emphasis ours]

Oh, we've never heard that before...

Officials with Hyundai Motor Co, Nissan Motor Co and Volkswagen AG said they could not immediately comment on the issue.

A spokesman for Honda Motor Co said that the Japanese automaker was studying the security of on-vehicle computer systems, but declined to discuss those efforts.

Mums the word is a much smarter response to the press.

A spokesman for the U.S. Department of Homeland Security declined to comment when asked how seriously the agency considers the risk that hackers could launch attacks on vehicles or say whether DHS had learned of any such incidents.

They probably declined to comment because they are working on exploits for these as well.  Say it ain't so?  Look no further than Stuxnet and Flame, of which the US Gov takes full authorship credits.  It's the future of the "cyberwarfarestate".

We can't keep malware out of critical infrastructure SCADA systems.  There's no way we can keep it out of your mom's minivan.

Classic Trust

Ken Thompson is on the left. That's not Adam Savage on the right.

If you work in computer security or software development, and you have never read Unix co-creator Ken Thompson's original 1984 speech "Reflections on Trusting Trust" then you are hereby obliged to at least read the following snippet for today's history lesson, which is just as relevant-- actually more so-- today:

The moral is obvious. You can't trust code that you did not totally create yourself. (Especially code from companies that employ people like me.) No amount of source-level verification or scrutiny will protect you from using untrusted code. In demonstrating the possibility of this kind of attack, I picked on the C compiler. I could have picked on any program-handling program such as an assembler, a loader, or even hardware microcode. As the level of program gets lower, these bugs will be harder and harder to detect. A well installed microcode bug will be almost impossible to detect.

Ken was referring to the trojan modifications he embedded into the C compiler, illustrating that you need to rely on more that source code, but the compiler, the assember, the loader, all the way down to the instruction sets of the CPUs.  Or as Schneier famously pitched: "security is a chain; only as strong as its weakest link".

Who operates on a completely self-built system from software to hardware?  We would venture to say: nary a soul.

Just a good reminder for a random Thursday, in case you forgot.

Free OWASP .NET Development E-Book

For your developer friends (or you), Troy Hunt made his book about the OWASP Top 10 web security flaws as implemented in .NET available as a free e-book PDF.  Plenty of good information in there to share with developers who need more clarification or a refresher in what it takes to build defensible web applications.

Alex Halderman on Internet Voting

Computer Science Professor J. Alex Halderman is an upcoming academic star that we at Securology have been watching for awhile now, since some of the earliest days of all the great work put on at Princeton by Ed Felten and his Freedom to Tinker group (an excellent blog). Halderman, having completed his PhD (Bell Labs UNIX and C programming language creator Brian Kernighan was on his PhD committee!), has moved on to the University of Michigan as a member of the faculty and is continuing his excellent work at the intersection of technology and public policy, which always means security and privacy issues are in the spotlight.

Here is an excellent interview with Halderman (presumably shot at the 2012 RSA Conference) on how he and his students (legally) hacked the mock trial of Internet Voting put on by Washington D.C., and why Internet Voting should not be employed for a very long time.

In summary, there are two main reasons why Internet Voting is a horrible idea:

1. Getting the software perfectly correct is, for all intents and purposes, impossible.
2. Authenticating a voter eliminates the ability to anonymize the voter's vote (major privacy flaw).

Detecting Social Network Connectivity

This is a creative implementation that discovers several information flow theory violations. The end result is a website that is not part of a given social network can tell if a connected user is logged into the social network.

Check out the demo to see what your browser reveals.

More Fake Security

The uninstallation program for Symantec Anti-Virus requires an administrator password that is utterly trivial to bypass. This probably isn't new for a lot of people. I always figured this was weak under the hood, like the password was stored in plaintext in a configuration file or registry key, or stored as a hash output of the password that any admin could overwrite with their own hash. But it turns out it's even easier than that. The smart developers at Symantec were thoughtful enough to have a configuration switch to turn off that pesky password prompt altogether. Why bother replacing a hash or reading in a plaintext value when you can just flip a bit to disable the whole thing?

Just flip the bit from 1 to 0 on the registry value called UseVPUninstallPassword at HKEY_LOCAL_MACHINE\SOFTWARE\INTEL\LANDesk\VirusProtect6\ CurrentVersion\Administrator Only\Security. Then re-run the uninstall program.

I am aware of many large organizations that provide admin rights to their employees on their laptops, but use this setting as a way to prevent them from uninstalling their Symantec security products. Security practitioners worth their salt will tell you that admin rights = game over. This was a gimmick of a feature to begin with. What's worse is that surely at least one developer at Symantec knew that before the code was committed into the product, but security vendors have to sell out and tell you that perpetual motion is possible so you'll spend money with them. These types of features demonstrate the irresponsibility of vendors (Symantec) who build them.

And if you don't think a user with admin rights will do this, how trivial would it be for drive-by malware executed by that user to do this? Very trivial.

Just another example on the pile of examples that security features do not equal security.

"Application" vs "Network" Penetration Tests

Just my two cents, but if you have to dialog about the distinction between an "application" and "network" penetration test, then you're missing the point and not probably testing anything worthwhile.

First of all, the "network" is not an asset. It's a connection medium. Access to a set of cables and blinky lights means nothing. It's the data on the systems that use the "network" that are the assets.

Second, when a pen tester says they're doing a "network penetration test", they really mean they're going to simulate an attacker who will attack a traditional application-- a "canned" application (usually), like one that runs as a service out of the box on a consumer Operating System. It's more than just an authentication challenge (though it could be that). It's likely looking for software defects in those canned applications or commonly known insecure misconfigurations, but it's really still an application that they are testing. [In fact, the argument that a "network penetration test" is nothing more than vulnerability scan seems plausible to me.]

Third, when they say "application penetration test", they are typically talking about either custom software applications or at least an application that didn't come shipped with the OS.

Fourth, if you're trying to test how far one can "penetrate" into your systems to gain access to data, there should be no distinction. If a path to the asset you're trying to protect is through a service that comes bundled with a commercial OS, or if the path to the asset is through a customer product; it makes no difference. A penetration is a penetration.


Yet, as an industry, we like to perpetuate stupidity. This distinction between "network" and "application" penetration tests is such a prime example.

The Stupidest PCI Requirement EVER!

The Payment Card Industry (PCI) regulatory compliance goals are good, but not perfect. Some individual requirements in the Data Security Standard (DSS) are flat out ridiculous. In particular, a couple regarding key management take the cake.

3.5.2 Store cryptographic keys securely in the fewest possible locations and forms.
...
3.6 Fully document and implement all key-management processes and procedures for cryptographic keys used for encryption of cardholder data, including the following:
...
3.6.3 Secure cryptographic key storage.

Hmm. Before we even get too far, there is a redundancy with 3.5.2 and 3.6.3. Why even have 3.5.2 if 3.6 covers the items in more detail? I digress ...

3.6.6 Split knowledge and establishment of dual control of cryptographic keys.

What the authors of the DSS were thinking was that PCI compliant merchants would implement cold war-esque missile silo techniques in which two military officers would each place a physical key into a control console and punch in their portion of the launch code sequence. This is technically possible to do with schemes like Adi Shamir's key splitting techniques. However, it rarely makes sense to do so.

Consider an automated e-commerce system. The notion of automation means it works on its own, without human interaction. If that e-commerce system needs to process or store credit card numbers, it will need to encrypt and decrypt them as transactions happen. In order to do those cryptographic functions, the software must have access to the encryption key. It makes no sense for the software to only have part of the key or to rely on a pair of humans to provide it a copy of the key. That defeats the point of automation.

If the pieces of the key have to be put together for each transaction, then a human would have to be involved with each transaction-- definitely not worth the expense! Not to mention an exploit of a vulnerability in the software could result in malicious software keeping a copy of the full key once it's unlocked anyway (because it's the software that does the crypto functions, not 2 people doing crypto in their heads or on pen and paper!).

If a pair of humans are only involved with the initial unlocking of the key, then the software gets a full copy of the key anyway. Any exploit of a vulnerability in the software could potentially read the key, because the key is in its running memory. So, on the one hand, there is no requirement for humans to be involved with each interaction, thus the e-commerce system can operate more cheaply than, say, a phone-order system or a brick-and-mortar retailer. However, each restart of the application software requires a set of 2 humans to be involved with getting the system back and online. Imagine the ideal low-overhead e-commerce retailer planning vacation schedules for its minimal staff around this PCI requirement! PCI essentially dictates that more staff must be hired! Or, that support staff that otherwise would NOT have access to a portion of the key (because they take level 1 calls or work in a different group) now must be trusted with a portion of it. More hands involved means more opportunity for collusion, which increases the risk by increasing the likelihood of an incident, which is NOT what the PCI folks are trying to accomplish!

The difference between a cold war missile silo and an e-commerce software application is the number of "secure" transactions each must have. Missile silos do not launch missiles at the rate of several hundred to several thousand an hour, but good e-commerce applications can take that many credit cards. When there are few (albeit more important) transactions like entering launch codes, it makes sense to require the attention of a couple different people.

So splitting the key such that an e-commerce software application cannot have the full key is stupid.

But then there is the coup-de-grace in the "Testing Procedures" of 3.5.2:

3.5.2 Examine system configuration files to verify that keys are stored in encrypted format and that key-encrypting keys are stored separately from data-encrypting keys.

This is the ultimate in pointless PCI requirements. The real world analogue is taking valuables and stashing them in a safe that is unlocked with a key (the "data-encrypting key" or DEK in PCI parlance). Then, stash the key to the first safe into a second safe also unlocked by a key (the "key-encrypting key" or KEK in PCI parlance). Presumably, at this point, this second key will be like something out of a James Bond film where the key is actually in two parts, each possessed by one of two coordinating parties who reside in two geographically distinct locations. In practice, however, the second key is typically just slipped under the floor mat and the two safes are sitting right next to one another. It takes a little longer to get the valuables out of the safe, but does little to actually prevent a thief from doing so.

In an e-commerce system, it's no different. All of the same pointlessness of splitting keys (as described above) still applies, but now there is an additional point of failure and complexity: the KEK. Encryption does add overhead to a software application's performance, though the trade-off is normally warranted. However, if at each transaction the software needs to use the KEK to unlock the DEK and then perform an encrypt or decrypt operation on a Credit Card number, the overhead is now double what it was previously. As such, most software applications that use KEKs don't do that. Instead, they just use the KEK to unlock the DEK and keep the DEK in memory throughout the duration of operation, until presumably the software or server need to be taken offline for reconfiguration of some kind. With an encryption key in memory, there's still the plausible risk that an exploit of a vulnerability in the software application could result in disclosure of the key or the records that are supposedly protected by it. Even if the key was once in memory, recent research reminds us that data remanence of RAM retains sensitive data like keys for longer than we might expect.

And if a software application is allowed to initiate and unlock its keys without a human (or pair of humans in the case of key splitting), such as the case when the e-commerce application calls for a distributed architecture of multiple application servers in a "farm", then there really is no point of having a second key. If the application can read the second key to unlock the first key, then so could an attacker that gets the same rights as the application. The software might as well just read in the first key in an unencrypted form, which would at least be a simpler design.

If the threat model is the server administrator stealing the keys, then what's the point? Administrators have FULL CONTROL. The administrator could just as easily steal the DEK and the KEK. And no, the answer is not encrypting the KEK with a KEKEK (Key-Encrypting-Key-Encrypting Key), nor with a KEKEKEK, etc., because no matter how many keys are involved (or how many safes with keys in them), the last one has to be in plaintext (readable) form! The answer is, make sure the Admins are trustworthy (which means do periodic background checks, psych evaluations if they are legal, pay them well and do your best to monitor their actions).

If the threat model is losing (or having stolen) a backup tape of a server's configuration and data, then, again, a KEK offers little help, since an attacker who has physical access to a storage device has FULL CONTROL and can read the KEK and then decrypt the DEK and the credit card records.

It is also commonly suggested by PCI assessors that KEKs be stored on different servers to deal with the threat of an administrator stealing the DEK. But that is really just the same as the problems above, just rehashed all over again.

If the application on Server A can automatically read in the KEK on Server B, then (again) a vulnerability in the application software could potentially allow malware to steal the KEK from Server B or cache a copy of it once in use. If the admin of Server A also has admin access to Server B, then it's the same problem there, too; the admin can steal the KEK from Server B and unlock the DEK on Server A. If the admin does NOT have access to the KEK, then it's the two-humans-required-for-support-scenarios all over again, like key splitting. If the KEK cannot be read by Server A when it is authorized to do so (such as the mechanism for reading the KEK from Server B is malfunctioning), then Server B's admin must be called (Murphy's Law indicates it will be off-hours, too) to figure out why it's not working. And in a small to medium sized e-commerce group, like in an ideal low-overhead operation, it will almost always be the same person or couple of people that have admin access to both. In the large scale, an admin of Server A and an admin of Server B can just choose to collude together and share the ill gains from the theft of the KEK, the DEK, and the encrypted credit card records.

What about a small e-commerce application, where the web, application, and database tiers are contained in one physical server for cost reasons? In that case, perhaps the "scope" of PCI compliance would have previously been a single server, but using a secondary server to house a single KEK now introduces that secondary server into the littany of other PCI requirements, which will likely erode the cost benefit of a single server to house all tiers of the application in the first place.

In the off-chance that a backup copy of Server A's configuration and data is lost or stolen, there will be a false sense of temporary hope if Sever B's backup is not also lost or stolen. However, collusion and/or social engineering of an admininstrator of Server B still applies. Also, this will allow an attacker time to reverse engineer the software that is now in the hands of the attacker. Is there a remote code execution bug in the software that could allow an attacker to leak either the full encryption key or individual credit card records? Is there a flaw in the way the crypto keys were generated or used that reduces the brute-force keyspace from the safety of its lofty 2^128 bit perch? Did the developers forget to turn off verbose logging after the support incident last weekend? Are there full transaction details in the clear in a log file? A better approach would be to just use some sort of full storage volume encryption INSTEAD of transaction encryption, such that none of those possibilities would occur. But in practice, that is rarely done to servers (and somehow not mandated by the PCI DSS).

So storing the KEK on multiple servers just introduces more support complexity than it reduces risk from data theft.

And if we now know that these requirements don't guarantee anything of substance that would pass Kerckhoff's Principle (i.e. security by obscurity does not make these key storage techniques more "secure"), then we can also say that having multiple keys, separate KEK storage, and key-splitting all violate 3.5.2 because the keys are not stored "securely in the fewest possible locations and forms".

...

To Recap: Splitting keys is not feasible in most cases; it negates the benefit from having less people involved with e-commerce. Encrypting keys with other keys is an attempt to implement computer security perpetual motion machines. If you really are paranoid, implement full volume encryption on your servers. If you're not, well, ditch the transaction crypto unless you just happen to have CPU cycles to spare. If you must be "PCI Compliant" (whatever that means outside of "not paying fines"), then implement your e-commerce app to have an "auditor mode" by default, where it requires two people to each type in part of a key for the application to initiate. Then let it have a normal "back door" mode where it just uses the regular key for everything. [Most PCI Assessors are not skilled or qualified enough to validate the difference by inspecting the software program's behavior. They really just want a screen shot to go into their pretty report. Of course, this requires a detailed understanding of the ethics involved, and your mileage may vary.]

And remember: "you're only paranoid if you're wrong."


...

UPDATED: It was pointed out that there is even one more crazy method that PCI Assessors think can turn this polished turd into alchemist's gold: "encode" the KEK into the software's binary. By "encode" they mean "compile", as in have a variable (probably a text string) that contains the value of the KEK. Rather than have the software read in that KEK value from a file, have it just apply the KEK from the static or constant variable in the decryption operation that unlocks the DEK. This is equally stupid as the above. If the point of having a KEK and a DEK is to prevent someone who has access to the file system from unlocking credit card records, then the PCI folks completely missed "intro to pen testing 101" which describes the ultra l33t h4x0r tool called "strings". Any text strings (ASCII, UNICODE, what have you) can be extracted by that ages-old command line utility. So, if the threat model is somebody who stole the contents of a server's disks-- they win. If the treat model is a server administrator-- they win. Not to mention, the common practices of software developers is to store source code in a repository, presumably a shared repository. Any static variable that is "encoded" into a binary will live in source code (unless, I guess, the developer is sadistic enough to fire up a hex editor and find/replace the ASCII values in the binary after it's compiled) and source code lives in repositories, which means even more opportunities for collusion. This type of crypto fairydust magic is pure fiction-- it just doesn't work like they think it does.

Gmail Mobile Insecurity

Google just released a new set of security features for Gmail. However, you cannot turn on the "always use HTTPS" option if you are also using the older java based Gmail Mobile client for smart phones, like the Blackberry. They have written that app to always fetch new mail and post actions like delete and archive over HTTP instead of HTTPS. With Gmail's new require-HTTPS feature enabled, the mobile client will error out that it cannot fetch mail. The new version (2.0.5 as of right now), is a little quirky with this setting, but it will work with require-HTTPS enabled.

Without the new version, smart phones which can fetch content over local WiFi have a ready made attack vector. Blackberries, which route all traffic through an encrypted tunnel back to the company's BES (Blackberry Enterprise Server), would find themselves vulnerable to eavesdropping and MITM closer to the BES (i.e. the corporate LAN), or, of course, at any hop along the way from the corporate LAN through the ISPs (but ISPs would never snoop on your email ;).

With these embedded devices, how many people stop to think about which protocols these apps use under the hood? It's not like on a traditional browser, where the user can at least monitor link destinations via a status bar. I would also venture to say that not too many people worry about keeping app versions up to date-- there haven't been too many nagging update applications for the majority of smart phones, yet. Google's Mobile Updater requires the user to go in and manually check for new versions. So, it's even more imperative for these app developers to get it right the first time.

Gmail Notifier is also experiencing similar issues.

Why You Don't Need a Web Application Layer Firewall

Now that PCI 6.6's supporting documents are finally released, a lot people are jumping on the "Well, we're getting a Web Application Firewall" bandwagon. I've discussed the Pros and Cons of Web Application Firewalls vs Code Reviews before, but let's dissect one more objection in favor of WAFs and against code reviews (specifically static analysis) ...

This is from Trey Ford's blog post "Instant AppSec Alibi?"

Let’s evaluate this in light of what happens after a vulnerability is identified- application owners can do one of a couple things…

1. Take the website off-line
2. Revert to older code (known to be secure)
3. Leave the known vulnerable code online

The vast majority of websites often do the latter… I am personally excited that the organizations now at least have a viable new option with a Web Application Firewall in the toolbox! With virtual patching as a legitimate option, the decision to correct a vulnerability at the code level or mitigate the vuln with a WAF becomes a business decision.

There are two huge flaws in Mr Ford's justification of having WAFs as a layer of defense.

1) Web Application Firewalls only address HALF of the problems with web applications: the syntactic portion, otherwise known in Gary McGraw speak as "the bug parade". The other half of the problems are design (semantic) problems, which Gary refers to as "security flaws". If you read Gary's books, he eloquently points out that research shows actual software security problems fall about 50/50 in each category (bugs and flaws).

For example, a WAF will never detect, correct, or prevent horizontal (becoming another user) or vertical (becoming an administrator) privilege escalation. This is not an input validation issue, this is an authorization and session management issue. If a WAF vendor says their product can do this, beware. Given the ideal best case scenario, let's suppose a WAF can keep track of the source IP address of where "joe" logged in. If joe's session suddenly jumps to an IP address from some very distinctly different geographic location and the WAF thinks this is "malicious" and kills the session (or more realistically the WAF just doesn't pass the transactions from that assumed-to-be-rogue IP to the web application), then there will be false positives, such as corporate users who jump to VPN and continue their browser's session, or individuals who switch from wireless to an "AirCard" or some other ISP. Location based access policies are problematic. In 1995 it was safe to say "joe will only log on from this IP address", but today's Internet is so much more dynamic than that. And if the WAF won't allow multiple simultaneous sessions from the same IP, well forget selling your company's products or services to corporate users who are all behind the same proxy and NAT address.

Another example: suppose your org's e-commerce app is designed so horribly that a key variable affecting the total price of a shopping cart is controlled by the client/browser. If a malicious user could make a shopping cart total $0, or worse -$100 (issuing a credit to the card instead of a debit), then no WAF on today's or some future market is going to understand how to fix that. The WAF will say "OK, that's a properly formatted ASCII represented number and not some malicious script code, let it pass".

Since the PCI Security Standards Council is supporting the notion of Web Application Firewalls, that begs the question: Does the PCI Security Standards Council even understand what a WAF can and cannot do? Section 6.6 requires that WAFs or Code Reviews address the issues inspired by OWASP which are listed in section 6.5:

6.5.1 Unvalidated input
6.5.2 Broken access control (for example, malicious use of user IDs)
6.5.3 Broken authentication and session management (use of account credentials and session cookies)
6.5.4 Cross-site scripting (XSS) attacks
6.5.5 Buffer overflows
6.5.6 Injection flaws (for example, structured query language (SQL) injection)
6.5.7 Improper error handling
6.5.8 Insecure storage
6.5.9 Denial of service
6.5.10 Insecure configuration management

The following items fall into the "implementation bug" category which could be addressed by a piece of software trained to identify the problem (a WAF or a Static Code Analyzer):

6.5.1 Unvalidated input
6.5.4 Cross-site scripting (XSS) attacks
6.5.5 Buffer overflows
6.5.6 Injection flaws (for example, structured query language (SQL) injection)
6.5.7 Improper error handling

These items fall into the "design flaw" category and require human intelligence to discover, correct, or prevent:

6.5.2 Broken access control (for example, malicious use of user IDs)
6.5.3 Broken authentication and session management (use of account credentials and session cookies)
6.5.8 Insecure storage
6.5.9 Denial of service
6.5.10 Insecure configuration management

Solving "design" or "semantic" issues requires building security into the design phase of your lifecycle. It cannot be added on by a WAF and generally won't be found by a code review, at least not one that relies heavily on automated tools. A manual code review that takes into consideration the criticality of a subset of the application (say, portions dealing with a sensitive transaction) may catch this, but don't count on it.



2) If your organization has already deployed a production web application that is vulnerable to something a WAF could defend against, then you are not really doing code reviews. There's no more blunt of a way to put it. If you have a problem in production that falls into the "bug" category that I described above, then don't bother spending money on WAFs. Instead, spend your money on either a better code review tool OR hiring & training better employees to use it (since they clearly are not using it properly).



Bottom line: any problem in software that a WAF can be taught to find could have been caught at development time with a code review tool, so why bother buying both. You show me a problem a WAF can find that slipped through your development process, and I'll show you a broken development process. Web Application Firewalls are solution in search of a problem.

Sending Bobby Tables to the Moon

NASA has a program where you can send your name to the moon. Just give them your name, they'll store it electronically, and send it on the next lunar rover to be left there forever.

Now, little Bobby Tables will be immortalized forever on the moon.

Automating Exploitation Creation

Some academic security researchers at Carnegie Mellon have released a very compelling paper which introduces the idea that just monitoring a vendor's patch releases can allow for an automated exploit creation. (They call it "APEG".) They claim that automated analysis of the diffs between a pre-patched program and a patched program is possible-- and that in some cases an exploit can be created in mere minutes when some clients take hours or days to check in and install their updates! Granted there is some well established commentary from Halvar Flake about the use of the term "exploit" since the APEG paper really only describes "vulnerability triggers" (Halvar's term).

Our friends at Carnegie Mellon have proved that the emperor hath no clothes. Creating exploits from analyzing patches is certainly not new. What is novel, in this case, is how the exploit creation process is automated:

"In our evaluation, for the cases when a public proof- of-concept exploit is available, the exploits we generate are often different than those publicly described. We also demonstrate that we can automatically generate polymorphic exploit variants. Finally, we are able to automatically generate exploits for vulnerabilities which, to the best of our knowledge, have no previously published exploit."

PCI 1.1 Section 6.6

If you're one of the many practitioners waiting to see how the PCI Security Council clarifies the ambiguous 6.6 requirement, then you may wish to use this interview with Bob Russo, General Manager of the PCI Security Standards Council, as either an inkling towards an interpretation OR just more obfuscation (depending upon your point of view).

Here is the PCI requirement in question:

6.6 Ensure that all web-facing applications are protected against known attacks by applying either of the following methods:
• Having all custom application code reviewed for common vulnerabilities by an organization that specializes in application security
• Installing an application layer firewall in front of web-facing applications.
Note: This method is considered a best practice until June 30, 2008, after which it becomes a requirement.

Russo's comments on the debate of Web Application Firewalls versus Code Reviews:

"Personally, I'd love to see everyone go through on OWASP-based source-code review, but certainly, that's not going to happen," Russo said, referring to the expensive and time-consuming process of manual code reviews. "So the application firewall is probably the best thing to do, but there needs to be some clarification around what it needs to do. That clarification is coming; that's been the biggest question."

Jeremiah Grossman sounded off on the interview as well.



Even given all of the discourse I have heard and read to date, there are many unanswered questions on this one particular point alone. No doubt the PCI Security Standards Council has realized that application layer problems are going to undermine everything else we have taught security practitioners for the last decade about the idiocy of controlling security at the network layers. And no doubt the PCI Security Standards Council understands they have a mighty hand to influence organizations to handle their custom software with the appropriate level of diligence and quality that cardholders deserve. However ...

Here are my top 7 questions concerning PCI 1.1, Requirement 6.6 that are still left unanswered:

1) Please define "web-facing applications". Does that mean HTTP/S applications? Does that mean anything directly exposed to Internet traffic? Or, does it mean any application that Al Gore created? [PCI Expert, Trey Ford, attempted to define "web-facing", but we need the offical PCI Security Council interpretation.]

2) Please define "known attacks". Known by whom? Who is keeping the authoritative list? What happens when new attacks become "known" and are added to the list? Do we have to go back and perform more analysis to check for the new attacks?

3) Please define "an organization that specializes in application security". Is that a third party or can it be a team within an organization? Can it be a team of one in a smaller organization? What is meant by "specializes"? Does that mean "took a class", "has a certificate", or is that reserved for somebody who leads the industry in the subject matter? "Application Security" as a discipline (sorry, Gary McGraw--you're right, we should call it "software security") is new. Will we have a chicken and egg problem trying to establish people as specialists in application security?

4) Does a blackbox (runtime) scanning approach constitute a "review" of custom application code? Or will only a whitebox (source code at development time) cut the mustard? Can automated review tools be used, or must it be 100% manual (human) code review? To what extent can automation be involved? Are there specific products (vendors) that are preferred or required when selecting automated tools?

5) Does the "review" imply remediation? In the case of PCI Vulnerability Scanning Procedures, some lesser vulnerabilities are allowed to exist, but vulnerabilities that the PCI Security Standards Council rate at a higher criticality must absolutely be fixed. What criticality scale must we use? Is there a taxonomy of vulnerabilities that are categorized by "must fix" criticality versus a "should fix" criticality?

6) Please define "an application layer firewall". Is that a preventative tool or can it be just a detective tool (i.e. must it be active or can it be passive, like an IDS)? What "bad things" must it detect? How tight must it be tuned? Will there be a process to pre-certify vendors, or must we invest in it now and hope that auditors will accept what we choose?

7) Why is that we are (as of today) only a mere 76 days out from when requirement 6.6 becomes mandatory and we do NOT yet have clarification? Large organizations move slowly. Complicated "web-facing applications" may take a long time to properly regression test with either option implemented (remediations found in code reviews OR web application layer firewall deployments). We have little over two months to: 1) Understand the requirement, 2) Budget accordingly, and 3) Implement on time and under budget. With PCI DSS version->next right around the corner, why wasn't this requirement held off until it could be properly flushed out in the next version?

Localhost DNS Entries & "Same Site Scripting"

I'm not a big fan of new names for variations of existing attacks, but Tavis Ormandy (of Google) has pointed out an interesting way to leverage non-fully qualified DNS entries for localhost (127.0.0.1) with XSS:

It's a common and sensible practice to install records of the form
"localhost. IN A 127.0.0.1" into nameserver configurations, bizarrely
however, administrators often mistakenly drop the trailing dot,
introducing an interesting variation of Cross-Site Scripting (XSS) I
call Same-Site Scripting. The missing dot indicates that the record is
not fully qualified, and thus queries of the form
"localhost.example.com" are resolved. While superficially this may
appear to be harmless, it does in fact allow an attacker to cheat the
RFC2109 (HTTP State Management Mechanism) same origin restrictions, and
therefore hijack state management data.

The result of this minor misconfiguration is that it is impossible to
access sites in affected domains securely from multi-user systems. The
attack is trivial, for example, from a shared UNIX system, an attacker
listens on an unprivileged port[0] and then uses a typical XSS attack
vector (e.g. in an html email) to lure a victim into
requesting http://localhost.example.com:1024/example.gif, logging the
request. The request will include the RFC2109 Cookie header, which could
then be used to steal credentials or interact with the affected service
as if they were the victim.

Tavis recommends removing localhost entries from DNS servers that do not have the trailing period (i.e. "localhost" vs. "localhost."). The trailing period assures that somebody cannot setup camp on 127.0.0.1 and steal your web applications cookies or run any other malicious dynamic content in the same domain, exploiting DNS for same origin policy attacks.

Two Words: Code Quality

Dr. Brian Chess, Chief Scientist at Fortify and static analysis guru, has a couple very interesting posts on the company blog: one on the U.S. court system paying attention to source code quality of breathalyzers, and one on the quality of source code in closed systems (Nintendo Wii and Apple's iPhone).

It appears that a custom crafted Zelda saved game file can exploit a buffer overflow in Zelda allowing the execution of any code you want to throw at the console-- step one of software piracy on the Wii. It just further illustrates that you should NEVER trust user input-- no matter how unlikely you think the input will be untrustworthy (ahem, saved games in a closed video game system).

About 1.5 Million iPhones are unaccounted for, suggesting they've been hijacked to be set free of AT&T contracts. And this further illustrates that controlling a system at a distance is impossible.

Dr. Chess' comments about the Breathalyzers are choice as well:

"One of the teams used Fortify to analyze the code, and lo-and-behold, they found a buffer overflow vulnerability! This raises the possibility that if you mix just the right cocktail at just the right time, you could craft an exploit. (Dream on.) The real lesson here is that our legal system is waking up to the importance of code. If the code isn’t trustworthy, the outcome isn’t trustworthy either. (Electronic voting machine vendors, you might want to read that last line again.)"

Targeted Bank Malware

There have been a lot of interesting things going on with malware these days, but this is on the top of the list (for the next few hours anyway ;). Symantec has a blog write-up on a specific trojan that targets over 400 of the most popular banks in the U.S. and abroad. From the post:

This Trojan downloads a configuration file that contains the domain names of over 400 banks. Not only are the usual large American banks targeted but banks in many other countries are also targeted, including France, Spain, Ireland, the UK, Finland, Turkey—the list goes on.

Targeted malware has some interesting economic ramifications. With signature based anti-malware, the defenses only work if a signature exists (duh!). But the problem is this: will your very large (think yellow) anti-malware vendor really publish a signature to catch malware targeted at only your organization, especially considering that each signature has the possibility of falsely identifying some other binary executable and causing a problem for another of their customers? No doubt anti-malware vendors have seen targeted malware and then specifically not published a signature for all of their customers. They may have released a specific signature for an individual organization, but the support risks are significant. It's better for everyone to NOT publish a signature unless it's widespread. Signatures add overhead, even if it's minimal. It's at least one more signature to search through when comparing each signature. At best, that's logarithmic complexity, and even that minimal complexity across a half-million signatures is expensive.

But that's not all that is interesting about "Trojan.Silentbanker" ...

Targeting over 400 banks ... and having the ability to circumvent two-factor authentication are just two of the features that push Trojan.Silentbanker into the limelight...

The ability of this Trojan to perform man-in-the-middle attacks on valid transactions is what is most worrying. The Trojan can intercept transactions that require two-factor authentication. It can then silently change the user-entered destination bank account details to the attacker's account details instead. Of course the Trojan ensures that the user does not notice this change by presenting the user with the details they expect to see, while all the time sending the bank the attacker's details instead. Since the user doesn’t notice anything wrong with the transaction, they will enter the second authentication password, in effect handing over their money to the attackers. The Trojan intercepts all of this traffic before it is encrypted, so even if the transaction takes place over SSL the attack is still valid. Unfortunately, we were unable to reproduce exactly such a transaction in the lab. However, through analysis of the Trojan's code it can be seen that this feature is available to the attackers.

The Trojan does not use this attack vector for all banks, however. It only uses this route when an easier route is not available. If a transaction can occur at the targeted bank using just a username and password then the Trojan will take that information, if a certificate is also required the Trojan can steal that too, if cookies are required the Trojan will steal those. In fact, even if the attacker is missing a piece of information to conduct a transaction, extra HTML can be added to the page to ask the user for that extra information.

If you understand how Two Factor Authentication really works (at least how banks are implementing it) then you already understand that it cannot stop fraud by an adversary in the middle (a less chauvinistic way to say "man in the middle"). Bruce Schneier has been preaching "the failures of two factor authentication" for a long time. What's monumental about this piece of malware is that it is the first to do well that which pundits have been saying for a long time. Two factor authentication, including PayPal's Security Key (courtesy of Verisign, a company not on my good list), is broken. SiteKey is broken (for the same reasons). What Schneier said in 2005 took until 2008 to materialize (at least publicly). This will not go down in history as an anomaly; this will go down as the first run at creating a sophisticated "engine" to handle MITM on any web application that has financial transactions.

Here's the real question to answer: How many fund transfer transactions must be hijacked to bank accounts in foreign nations that don't extradite their criminals to the U.S. before we finally realize just how bad malware in the "Web 2.0" world (sorry that's O'Reilly's name, I really mean "XMLHTTPRequest" world) can get?

It's about the transactions, folks. It's time to authenticate the transactions, not the users. (Schneier's been saying that, too.) Bank of America is closer-- yet farther away at the same time-- to getting this multi-factor authentication problem solved by implementing out-of-band multi-factor authentication in their "SafePass" service ... BUT, it's still completely vulnerable to this malware (I cannot state that this specimen does in fact implement a MITM on this BoA service since I have not reversed a sample, but if not in version 1.0, it will eventually). I wanted to write a rebuttal to the entry on Professor Mich Kabay's column on Network World, but the authors of this trojan did a better job!

The downfalls of SafePass, which uses SMS text messages to send one-time-use 6 digit passcodes (think RSA SecurID tokens without the hardware) to a customer's mobile phone. It's nice to see authentication out-of-band (not in the same communication channel as the HTTPS session), however, once the session is authenticated, the trojan can still create fraudulent transactions. SafePass could be improved by: 1) not using a non-confidential communication channel (SMS text messages are sent through the service provider's network in plaintext) and 2) requiring the customer to input the authentication code to validate transaction details that are sent with the out-of-band authentication token. Obviously you don't want to skip on #1 or else you'll have a privacy issue when the details of the transaction are broadcast through the provider's network and over the air.

Suppose Eve can modify Alice's payment to Bob the merchant (the transaction's destination) via a MITM trojan like this one. Eve modifies the payment to go to Charlie (an account in the Cayman Islands). Suppose Alice is presented with a "Please validate the transaction details we have sent to your mobile phone and enter the validation code below" message. Alice receives the message and notices the payment is to be sent to Charlie. Since she doesn't intend to pay Charlie, she calls her bank to report the fraud (as directed in the transaction validation method). Of course, that pipe dream would only work if SMS was a confidential channel [and if we could deliver a trustworthy confidential channel to a mobile phone, we will ALREADY solved the trustworthy transaction problem-- they're the same problem] AND if we could find a way to make customers actually PAY ATTENTION to the validation message details.

And of course, incoming SMS messages in the U.S. are charged to the recipient (what a stupid idea-- what happens when people start spamming over SMS like they do over SMTP?).


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[Side commentary] Oh. And then there's the problem of telling your family members not to click on any random e-cards (or anything else that your family members were not expecting) because it just got a little scarier out there. Imagine your retired parent just clicked on some pretty animated something-or-other that launched some client-side script, installed the Trojan.Silentbanker (or similar) and then the next time they went to check their retirement savings, their life's solvency was sent to a Cayman Islands' account and liquidated faster than you can say "fraud". Does dear old Grandma or Grandpa have to go back to work? They just might, or become a liability on their children and grandchildren. If that won't scare the older generation away from the unsafe web, what will?

Gary McGraw on Application Layer Firewalls & PCI

This serves as a good follow-up to my dissection of Imperva's Application Layer Firewall vs Code Review whitepaper.

Gary McGraw, the CTO of software security firm Cigital, just published an article on Dark Reading called "Beyond the PCI Bandaid". Some tidbits from his article:

Web application firewalls do their job by watching port 80 traffic as it interacts at the application layer using deep packet inspection. Security vendors hyperbolically claim that application firewalls completely solve the software security problem by blocking application-level attacks caused by bad software, but that’s just silly. Sure, application firewalls can stop easy-to-spot attacks like SQL injection or cross-site scripting as they whiz by on port 80, but they do so using simplistic matching algorithms that look for known attack patterns and anomalous input. They do nothing to fix the bad software that causes the vulnerability in the first place.

Gary's got an excellent reputation fighting information security problems from the software development perspective. His Silver Bullet podcast series is one of a kind, interviewing everyone from Peter Neumann (one of the founding fathers of computer security) to Bruce Schneier (the most well known of the gurus) to Ed Felten (of Freedom to Tinker and Princeton University fame). He is also the author of several very well respected software security books.

Code Review vs. Application Layer Firewall

In a recent sales attempt, I received a whitepaper (warning: PDF) from Web Application Layer Firewall vendor Imperva entitled: "The New PCI Requirement: Application Firewall vs. Code Review".

For those not familiar with the Payment Card Industry (PCI) compliance regulations, visit the PCI DSS (Data Security Standard) website.

From my perspective, PCI is an excellent set of security compliance regulations, perhaps the best that exist in the U.S. Items are clear, concise, and specific (sometimes too specific), which is in stark contrast to other regulations, such as SOX, HIPAA, GLBA, etc.

Here's the specific PCI requirement in question:

6.6 Ensure that all web-facing applications are protected against known attacks by applying either of the following methods:
• Having all custom application code reviewed for common vulnerabilities by an organization that specializes in application security
• Installing an application layer firewall in front of web-facing applications.
Note: This method is considered a best practice until June 30, 2008, after which it becomes a requirement.

If you're bored already, you can sum up this problem as a typical 'business case for better engineering' problem.

We (the IT and Security field) know how to achieve higher security assurance in critical applications: thorough source code analysis coupled with simple design. However, we know that for many (if not most) organizations to adopt this mindset, it will require an overhaul for their existing software lifecycles. To put it bluntly: few people are truly analyzing their design and their code.

So in to our rescue is a typical information security vendor, ready to offer a hybridized second-rate solution to the problem. [To be fair, I think it is a well engineered solution, but for the wrong problem-- the problem of managing an application without truly understanding its code.]

Now to jump in and dissect their whitepaper ...

"What is an “Application Layer Firewall”?
An application layer firewall, also known as a “Web Application Firewall” or “WAF” is a network device that is placed in front of the Web applications in an organization’s data center to protect against attacks. A WAF is able to view and understand the full spectrum of application traffic so that it can protect the applications and the sensitive data from illegitimate access and usage." [Italics are mine]

This is stopping point #1. How is it possible that a vendor-- who has NEVER seen your organization's application-- can create a drop-in box that can "understand the full spectrum" of your application's traffic??? Again, to be blunt: they cannot. They can make guesses about commonalities among applications they have seen in the past (e.g. like customers whose applications were extensively analyzed for the purpose of product development). They may be even able to code in some inference engines that can make educated guesses at runtime, but they cannot ever truly "understand the full spectrum".

"Because of SecureSphere’s unique Dynamic Profiling capabilities, it automatically builds a complete baseline profile of your applications and network traffic in a matter of days. Using the application profile, SecureSphere can distinguish between legitimate user behavior and illegitimate behavior as well as protect from attacks... No manual intervention or tuning is necessary, keeping your on-going administrative costs far lower than other WAF products." [Italics are mine]

So, yes, it is an inference engine; note the italicized portions of the quote above. What is striking is the claim that this behavioral analysis tool does not require human intelligence for tuning, which means either: 1) the engine is tuned to avoid false positives at the expense of neglecting true positives, or 2) the Marketing department is (ahem) over-estimating their product's ability. Any behavioral analysis tool requires extensive tuning.

"While code review is a good idea, and is consistent with coding best practices, hiring consultants entails extra cost, loss of flexibility, resource allocation issues, scheduling headaches, and ultimately a lower grade of security than you would achieve through the deployment of a Web Application Firewall." [Italics are mine]

What amazes me in the world of marketing is that it's an acceptable practice to both claim a universal truth and debunk it in the same sentence. The whitepaper notes that code review is a "best practice", yet before a breath is taken attempts to claim that code review is a lower security assurance process when compared to using an application layer firewall, which simply doesn't make sense. Drop-in products work blind-- they do not know your organization's applications and they can only make inferences regarding them. Human Intelligence (this assumes training and expertise, hence the word "intelligence") will certainly trump; understanding the application is inherent to the process of good coding review and implementation.

If the assurance of externally facing applications is of utmost importance, then design/implementation time controls (e.g. static analysis) should be explored, not runtime controls (i.e. application layer firewalls).

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UPDATED 12/10/2007: Here's a follow-up ...