Web 2.0 Under Siege

Robert writes "Security researchers have found what they say is an entirely new kind of web-based attack, and it only targets the Ajax applications so beloved of the 'Web 2.0' movement. Fortify Software, which said it discovered the new class of vulnerability and has named it 'JavaScript hijacking', said that almost all the major Ajax toolkits have been found vulnerable. 'JavaScript Hijacking allows an unauthorized attacker to read sensitive data from a vulnerable application using a technique similar to the one commonly used to create mashups'"

XSS

So, how is this different than Javascript injection or Cross-site Scripting?

Re:XSS

I think the very subtle difference is that this time the calls are made using site A's public Ajax API, using site A's authentication token, but are made from a script sitting on site B. The javascript calls return with data from site A, which can then be handled by site B. XSS/JS Injection is more about injecting alien javascript onto site A to make site A call site B with the info it wants.

Daniel

Re:XSS

Sorry, I was writing this in a rush. I meant site A executes the code that was injected, retrieves the resulting data from site A, and then sends that data over to site B (or some other location). Typically this "data" is stuff like login information...

Daniel

Vocabulary Fix

Sadly, this is likely to do very little to stop the use of the word 'mashups'.

Okay, I'll be the first to ask.

How is this different from cross-site scripting?

"In an example attack, a victim who has already authenticated themselves to an Ajax application, and has the login cookie in their browser, is persuaded to visit the attacker's web site. This web site contains JavaScript code that makes calls to the Ajax app. Data received from the app is sent to the attacker."

Re:Okay, I'll be the first to ask.

This is much harder to protect against than normal XSS. Why? Because the Ajax does not have to be executed from within the same domain.

Let's say someone wants to attack my site, amazing.com. I browse to their site, remarkable.com, and the exploit code gets loaded into my browser. Remarkable.com can post to amazing.com using AJAX and receive replies as though they were authenticated on my site, because the browser automatically sends the amazing.com cookies with it when accessing an amazing.com URL. It appears to the browser fundamentally as though I was in remarkable.com and then typed the amazing.com URL on to the address bar.

(Of course you could spoof the referer but not from an existing browser session so I think the referer can be relied on in this context.)

If this is so, then it could truly be a throbbing migraine to fix - you would have to use the HTTP referer field to verify that the site calling your Ajax code was valid.

Hope that helps. Not the cheeriest news this morning :-(, but hopefully Prototype will have some kind of fix, and life will go on.

D

Re:Okay, I'll be the first to ask.

No, that kind of thing has always been possible since the very first implementation of JavaScript. If you don't need POST, then you can even do it with plain HTML 2.0, no JavaScript.

The problem here is that JSON is a subset of JavaScript and so it is automatically parsed under the local domain's security context when it's included in a document with <script>. There's a few tricks to "hide" it even though it's already been parsed and is sitting in memory, I assume these guys have found a way around that.

Re:Okay, I'll be the first to ask.

this only affects AJAX APIs / apps that are designed to be called from other domains.

No, that's the vulnerability. This allows other domains to get the data when the applications don't want to share it.

Bottom line: Don't expose any data / functionality through an API that allows cross-domain XHR unless you add additional precautions.

The news here is that the "additional precautions" that most Ajax libraries take are ineffective.

XSRF

How is this different than Cross Site Response Forgery?

http://en.wikipedia.org/wiki/Cross-site_request_fo rgery [wikipedia.org]

quick!

Upgrade to Web 3.0, quick!

Duh

This has been around for (web) ages. As stated in the summary, it's used all over the place to create mashups because it's one of the only ways around the security requirement that XmlHttpRequest can only talk to the originating server.

Mashups?

'JavaScript Hijacking allows an unauthorized attacker to read sensitive data from a vulnerable application using a technique similar to the one commonly used to create mashups'

So back when I made the Beastie Boys rap over the Macarena tune, [spacemutiny.com] I was really hacking the Web 2.0? And here I thought I was just assaulting eardrums and good taste...

Does this mean...

that we can sue Morfik? /sarcasm

Where's the problem?

"In an example attack, a victim who has already authenticated themselves to an Ajax application, and has the login cookie in their browser, is persuaded to visit the attacker's web site. This web site contains JavaScript code that makes calls to the Ajax app. Data received from the app is sent to the attacker."

So essentially it means that the attacker can use the authentication cookie of the user to authenticate them again, and then run javascript with that authentication. But why are AJAX apps storing authentication in cookies? If you need to store authentication (User session id's etc), store them in a variable within the javascript. That'll stay there until a page refresh clears variable status, and how many page refreshes occur with AJAX?

AJAX apps do not need to (and should not!) store user authentication in cookies. Cookies are useful for keeping a continual session open between pages. AJAX needs no continual session. If they don't use cookies, then other sites cannot use that authentication.

Where's the problem? (What am i missing?)

PimTerry

Re:Where's the problem?

The problem is your statement that "AJAX needs no continual session"

AJAX really do need sessions. Just think of Gmail. It it a single AJAX session starting when you login, and finishing when you logout or timeout.

If AJAX don't use sessions, it would have to authenticate itself with username and password with each request it made to the server.

An better solution might be to let the AJAX application explicit handle sessions by storing the session id, and sending it in the post part of all it's requests. But that might be a problem with the browsers history, because it would then loose your session id, if you used the back button.

Shirky's Law:

"Social Software is stuff that gets spammed."

The obvious implication of Shirky's Law is that Web 2.0 services are an attractive nuisance and give spammers and other griefers an incentive to game the system. Any new web service has to account for this and build in extremely high levels of security. Obviously nobody is doing this.

Is that title sarcastic?

I really hope it is. There's no such thing as Web 2.0, some arse decided to put a label on the natural progression the Web was undertaking anyway. It's annoying when authors write that some entirely new, completely re-written version of the Web is--suprisingly--vulnerable, it's the same old Web, just with some new buzz-words.

This is a vulnerability that appears only when passing Javascript between client and server. An attacker has to get a potential-victim who is logged-in to a site, that uses the JSON format to exchange data using AJAX, to visit a page they've setup. Then the attacker can intercept the data as it travels between client and server, a man in the middle attack. From the article:

In an example attack, a victim who has already authenticated themselves to an Ajax application, and has the login cookie in their browser, is persuaded to visit the attacker's web site. This web site contains JavaScript code that makes calls to the Ajax app. Data received from the app is sent to the attacker.

So it's a known method of attack, but because it's aimed at web sites using AJAX it has to be labelled 'Web 2.0'. Ugh.

We've already seen this before

It was reported as a problem with the google address book. These guys just generalized the problem because they saw it in many places.

It actually could be pretty nasty. I think the only solution is for you to pass authenticated tokens through the url or input parameters (not through cookies).

It might be a good time to use the firefox NoScript plugin if you're not using it already. Only allow javascript on sites you trust.

Re:We've already seen this before

There are ways to deal with this. Joe Walker, author of Direct Web Remoting (DWR), talks about the GMail problem and ways to solve it:

http://getahead.org/blog/joe/2007/01/01/csrf_attac ks_or_how_to_avoid_exposing_your_gmail_contacts.ht ml [getahead.org]

Of course, DWR 2.0 will have all this goodness built in. :)

They discovered this?

I went to an Ajax conference last fall and I'm pretty sure that presenters mentioned this vulnerability in JSON.

All AJAX applications transfer data between the webpage in the client's browser and the server. If the data is in XML, the webpage and the XML have to come from the same server. If it's JSON (JavaScript Object Notation), then they do not have to come from the same server. So, if you are sending data that depends on some kind of authentication - don't use JSON.

The JSON vulnerability comes from having your session open too long. Someone navigates to a bad site and it access the active session on the target site. Shorter session timeouts help with this. You can also do some authentication in the XML request as well. And don't use JSON for data that requires authentication.

In short, if you're using AJAX for data that requires authentication, then you need to take some simple precautions.

Easy Fix

Just serve up an animated cursor before any XML handshakes. This will stop the attackers from exploiting the AJAX piece.

Leaves web to trusted sites only

I think the article is a bit exaggerated but if the idea that "Web 2.0" is under attack might be a good time to look at this problem. Consider that a lot of people only surf a few websites (get some news, etc) and use e-mail. Most people don't use the net for anything more.

So if I only visit about 10 websties daily and those 10 sites I'm reasonably sure are safe why would I go anywhere else if it could cause problems to my computer? I've seen and heard from a lot of people fed-up with spyware, adware and viruses. Its a waster of their time. So going to these other sites, simply because they could be infected would also be a waste of their time (assume they're interested in the content). If this blows up any more - or alternately - if the perception exists that the Internet will only get worse, its not going to help people go much past those 10 websites regularly.

Suprised?

Is anyone actually suprised by this? It was only a matter of time since most people are using all the frameworks out there and more than half of the AJAX sites that spawned up arent fully protected by smart coding since its a new technology.

Backwards quote...

From TFA..

Everybody thought that the rise of Ajax as a web programming model would merely exacerbate existing types of attack. Few thought it would give rise to a new class, noted (some random guy).

Actually, I'd claim "everybody" with a toe in the security world thought it was the opposite; we'd start hearing about daily/weekly Ajax security problems as a regular course of business.

(If you think various operating systems have legacy code problems; you don't know "Javascript as implemented by browsers"...)

The Biggest WTF...

The biggest WTF is that somebody is still using javascript. Oops. Wrong site...
(Captcha: backtotheweb1.0)

Detailed report on this problem (no reg required)

All: I encourage all of you to read the detailed report Fortify wrote on this topic. Its written for developers and explains the problem in clear technical detail. http://www.fortifysoftware.com/advisory.jsp [fortifysoftware.com] (No registration required) Its a long document but I doubt you'll have a lot of questions after reading it. Its refreshing to see reports written like this that don't insult a developer's intelligence.

sigh

This just sounds like a fancy Cross-Site Request Forgery.

I still maintain that the collective blindness to these security issues comes from our absolute refusal to see HTTP requests as function calls. This is partly due to the silly ideology of the REST crowd.

Rephrase the situation as follows and see if this doesn't make you pee your pants: "Any site can instruct your browser to execute an arbitrary function on another site using your authentication credentials."

Re:sigh

This just sounds like a fancy Cross-Site Request Forgery.

That'll be because it is. It's basically an observation that CSRF on a site which returns data in JSON format allows the attacker to read the content of the result. Well, duh. Of course that happens. It's one of the reasons I've always opposed JSON as a useful format.

The other reason is equally bad, but only applies to "mash up" type situations: the coder of the client has to trust the server with access to all data in the client. This makes it useless in many situations.

The best solution would be to scrap the current security system, make subrequest cookies (including XMLHttpRequests) dependent on both the domain the request goes to *and* the domain of the page that caused the request, and allow XMLHttpRequest to access servers other than the page source. This would both fix CSRF and eliminate the need for JSON. What more do you want? :)

vulnerable == cookie && json && !p

An application may be vulnerable if:

- It uses cookies to store session IDs or other forms of credentials; and
- It sends data from server to browser using "JSON" notation; and
- It doesn't require POST data in each request.

A vulnerable application can be fixed by changing any of these three aspects:

- Stop using cookies, and instead supply the credentials in the request's URL or POST data.
- Don't use JSON, or munge your JSON so that it can't be run directly from within a <script> tag; for example, you could put comments around it in the server and strip them off in your client.
- Have the client send some POST data and check for it on the server (a <script> tag can't send POST data).

My preference, and the strategy that I've used in Anyterm and Decimail Webmail, is to not use cookies. To me it actually seems easier to put the session ID in the request, rather than to mess around with cookies.

The advisory, which explains it all but is a bit waffly at the start, is at http://www.fortifysoftware.com/servlet/downloads/p ublic/JavaScript_Hijacking.pdf [fortifysoftware.com]

On the upside...

MySpace 2.0 is then, by extension, doomed. Watch CNN for exciting stories of the kiddie Internet wild west, where sexual predators and teenage hackers battle over rocky terrain useless to anyone with anything of import on their minds.

i told that EVERY time AJAX - 2.0 hype was posted

If you delegate operations and processes to client side, sooner or later they will be finding more ways to exploit it to an extent that it would be a security risk to offer such client side stuff, making anti-virus, anti-spyware, privacy product manufacturers more agitated about it, and in the end drawing visitors away from your site due to blocks, issues, and fear.

XML is so last week. What's really wrong.

XML is now so last week. Really l33t web apps use JSON, which is yet another way to write S-expressions like those of LISP, but now in Javascript brackets.

There are several security problems with JSON. First, some web apps parse JSON notation by feeding it into JavaScript's "eval" [json.org]. Now that was dumb. Some JSON support code "filters" the incoming data before the EVAL, but the most popular implementation missed filtering something and left a hole. Second, there's an attack similar to the ones involving redefining XMLHttpRequest: redefining the Array constructor. [getahead.org] (Caution, page contains proof of concept exploit.)

The real problem is JavaScript's excessive dynamism. Because you can redefine objects in one script and have that affect another script from a different source, the language is fundamentally vulnerable. It's not clear how to allow "mashups" and prevent this. The last attempt to fix this problem involved adding restrictions to XMLHttpRequest, but that only plugged some of the holes.

As a minimum, it's probably desirable to insist in the browser that, on secure pages, all Javascript and data must come from the main page of the domain. No "mashups" with secure pages.

Re:XML is so last week. What's really wrong.

There are several security problems with JSON. First, some web apps parse JSON notation by feeding it into JavaScript's "eval". Now that was dumb.

You don't say. My first thought on hearing about the entire idea was "why would you want to let a foreign server run its code on your page?"

The real problem is JavaScript's excessive dynamism. Because you can redefine objects in one script and have that affect another script from a different source, the language is fundamentally vulnerable.

Err... if I don't let foreign code execute (e.g. by doing 'var e = document.createElement("script"); e.src = "http://www.someotherserver.com/potential-security -risk"; document.body.appendChild (e);', which I've seen many scripts do) how can another site redefine the objects in my script? I think the vulnerability is that most JS programmers are too willing to let other sites execute arbitrary code in their own context, which really ain't good.

The last attempt to fix this problem involved adding restrictions to XMLHttpRequest, but that only plugged some of the holes.

The fix seems obvious to me:

* cookies in subrequests must be tied to the domain of the page that initiated the request as well as the domain the request goes to; this reduces the possibility of CSRF. So if www.a.com has a web page that requests data from www.b.com, it will only send a cookie if www.b.com set one in response to a previous request from www.a.com. This applies to SCRIPT tags, to IFRAME tags, to IMG tags, to LINK tags, etc.

* XMLHttpRequest must not be tied to the same-domain policy. Attempts to access a different domain should result in a request for confirmation from the user for the first time any particular requester/receiver domain pair is used. This means mashups (and other applications that need cross-domain access) can be written that do not need to use JSON. JSON parsing through script insertion or eval() is insecure, and should be deprecated.

As a minimum, it's probably desirable to insist in the browser that, on secure pages, all Javascript and data must come from the main page of the domain. No "mashups" with secure pages.

Scripts, yes. I don't see the need to ensure that data originates in the same domain.

Old truths new truths...

AKA, the security programmer's favorite adage: "The user is the enemy."

That is, when ANY new technique or code module is to be used in a production environment, it should not be considered ready until it has been thoroughly attacked by a person who has the kind of mind-set that will expose code vulnerabilities before a user (or set of users) finds them.

Trouble is, most IT organizations have a hard sell to get that type of person within the company -- first, because an "inside the firewall" attacker is counter-intuitive to the idea that a company should trust their employees, and second, the position seems redundant IF the programmers are up to speed on writing secure applications. Which -- catch 22 here -- they won't know until it is too late. Secondarily, inside the wire attackers are much more dangerous than outside attackers, because the inside the wire person comes to know exactly what is vulnerable, and what can be done with that knowledge.

Any thoughts?

Executing 3rd party code by default is insecure?

Fortunately the web development community has learned so much from the ongoing ramifications of Microsoft's "features first, security later" approach in the 90's that we would never recreate such a mess. Oh wait - automatic, default execution of third party code on the client browser, INSIDE THE FIREWALL? What could possibly go wrong with that?

The arguments today also mirror what went on with Windows and Outlook in the 90's. A few wild haired prophets screaming doom and gloom but 99.9% of the IT community was/is hypnotized by the glamour of "features, features, features" and security is relegated to patching. Like building a submarine out of swiss cheese. You'll spend the rest of your life patching but if everyone does it, it's normal. A few weirdos will look up and say "why don't we just start with a less porous base material?" but they will be shouted down by the masses.

Javascript, Flash and Applets are insecure by concept. Oh, pardon me, sandboxes will take care of everything? Append an image to the DOM from your server. If that "image" is actually a program which reads the query string you can pass it any information you want. Sandbox jumped. Not a bug, a feature.

It's not enough to patch websites. It only takes one popular compromised site to infect thousands or even millions of users. Do I trust every site on the internet to be 100% invulnerable 24/7? Not really. Not even the sites I work on.

Most BANKS and financial services require Javascript to log in. Nice to know such critical web services are designed by people who "care about customer security." (cough, cough)

NoScript [noscript.net] seems to be a reasonable compromise. No browser I'm aware of takes this approach by default.

I'm still waiting!

I'm still waiting for someone to come up with a nice pun involving the title of this news item and Steven Seagal! :D

I'm out for justice ;D

I give up.

First the MS cursor exploit [slashdot.org], now this. How are we supposed to surf the web, anymore? That's it! I'm going back to Morse Code:
_-_- ___ __ - __- - _ --- ___ __ - --- _ ___ -__-

Examples?

Are there any working examples of this problem we could see? I'm having trouble understanding exactly what the issue is supposed to be.

cookie still needs to be stolen doesn't it?

Am I missing something? Doesn't the attacker still need to be able to obtain the victim's cookie? Fair enough, this is not the most difficult task in the world, but if your cookie can be stolen and read by an attacker's site then the fact of AJAX being in the mix seems to be hardly relevant. If someone has your login cookie, why not just go the site with a forged cookie themselves? AJAX might help them to programatically use the cookie to authenticate themselves to the site and request data, but a program that just sends HTTP requests and takes cookies as input could probably achieve the same?

Where is my understanding flawed?

Where's the actual hole?

I've read the article, and some of the comments here, but can't find any concrete details about what the actual exploit is. All I can find is some vague references to "using javascript instead of xml" for transfering data, and "It's perfectly possible for any one web site to run JavaScript hosted on another domain. Applications such as Google Adsense or Google Maps, for examples, rely upon it." Do "11 out of 12" frameworks really use javascript? I thought JSON was the best method for transfering data (xml is too slow), and you're supposed to run a regex on it to kill any injections before evaling the JSON. I know I certainly do this, and I'd expect more than 1 in 12 of the major frameworks to do it too. As for being easy to execute javascript hosted on another domain, yeah that can be done. But how do you get *your* code to run on a domain that you have zero control over? Browsers are supposed to make this impossible, and if there's a hole this article doesn't tell you what it is. My FUD bells are ringing.

Under Siege

Impossible , An error programing? (another more) , can not be possible! programming is perfect!, bugs are not possible!, fails are not possible!. This should be an error on MATRIX, The Matrix (2.0) have a bug.

Good news for "Web 2.0" douchebags

Now they can go on and babble about a "Web 2.1" or a "Symantic Web" or other punditry.

xajax

So xajax is vunerable to JSON vunerabilities? That might be difficult since xajax only uses XML (the 'x' in xajax)

Interestingly the article says that xajax is vunerable, but then in the PDF report mentions that xajax isn't vunerable because it doesn't use JSON

Stop misusing this term, okay?

“Web 2.0” is not AJAX and “AJAX” is not Web 2.0. These terms are not synonyms nor does one necessarily imply the other. Yes, AJAX is an important participant, but Web 2.0 is really about service architecture [oreillynet.com] that is equally consumable by machines and people—a notion that somewhat embodies the original vision of the Web. The article title “Web 2.0 Under Siege” is misleading nonsense. It is analogous to stating that programming is “under siege” because a library exists that contains a vulnerability.

nonsense

What a crock. This has got zero to do with ajax. For example, even with 'insecure' PHP - the first line of any backend ajax code should read something like ..

require_once("include/session.inc");

Where session.inc reads the user cookie (or whatever the authentication mechanism your app uses), and sets up a validated user.

There is NO DIFFERENCE in the way users are authenticated between server side code that renders a regular page, and server side code that is called by ajax. One generally returns HTML, the other generally returns javascript or XML, but as far as authentication goes, they should use the same mechanism.

If your ajax code is capable of returning data that is not authorised, then the problem exists entirely between keyboard and chair. If that is the case with your app right now, then its something you should be able to fix entirely during your lunch break.

I have said it before on slashdot (re the Delphi/PHP thing) - ajax is not rocket science, its just a few extra lines of javascript to your program to call another program and get the results asynchronously. There is NO NEED to buy into some bloated third party 'pointy clicky enterprisey ajax' framework that cannot possibly know anything about your existing authentication methods.

It's simple to defend against. Don't be a wimp

It's simple to defend against. Don't be a wimp; read the original paper at http://www.fortifysoftware.com/servlet/downloads/p ublic/JavaScript_Hijacking.pdf [fortifysoftware.com], follow the advice, and all will be well. If nothing else, look at the Conclusion and Recommendations section at the end.

ASP.NET Ajax is not affected

ASP.NET Ajax [asp.net], with the default settings, is protected [asp.net] against these attacks.

Re:...allows an unauthorized attacker...

Yes; Tiger Teams [wikipedia.org] and the OPFOR in Red Flag exercises [wikipedia.org] come to mind.

Re:Enough

BBZZZT! I'll bite... "Web 2.0" is a term coined by Tim O'Reilly (of O'Reilly Media; you know, those books with the animals on the cover) as a way of classifying a new generation of web-based applications, a shift from static text and html to interactivity and user-participation in creating the content of a site. The media picked up on it later and gave it buzzwordyness. People who do not have a background in and/or an understanding of technology assume that the media made it up.

enough semantics!

Wrong. It's a buzzword used by the media to represent interactive web applications, whether they understand technology or not. It's useful because it's painfully simple, and non-techie people get the basic idea.

Given that the article was not aimed directly at web developers, but at people interested in computing in general, it's appropriate for them to use buzzwords to convey their message.

If I'm talking with another web developer, I'll get upset if he/she uses "web 2.0" in a sentence -- when it comes to my profession, I hate the word. When dealing with non-web tech savvy people, it's a helpful tool to refer to dynamic websites of the type that may have this vulnerability.

Very few news articles are ever written for the /. audience, so don't take it personally when they disregard us. And don't get upset at them for using certain words when they weren't talking to us in the first place. We may make a lot of things work, but the world doesn't revolve around ./!

Re:Enough

You should get the stick out of your ass. Discuss... ;)
Seriously, when they said Web 2.0, I knew what they were talking about (it's the "Under Seige" part that I felt was dumb). I knew they were talking about javascript and XMLHttpRequest stuff that is frequently called AJAX (another term which some people whine about). Do you even know what a buzzword is? It's something you add to a product because it's popular. Like "object oriented" or "xml" when it's irrelevant to the actual functioning of the product. On the other hand Web 2.0/AJAX defines web applications that function in quite a different manner than non Web 2.0/AJAX ones.

Re:Enough

A buzzword that well goes over very well with prospective clients these days, especially since you can tailor your definition to your clients desires due to the lack of an "official" description of the technology web 2.0 embraces and the new use models it allows.

Re:Enough

Ignorant media people and unscrupulous "consultants".

My company lost a client last year, because we were realistic with telling him what we could achieve over his web site. Meanwhile a "Web 2.0 consultant" told him that using the power of Web 2.0 he could keep my client's web site in the top google spot for search terms of his choice. My client was gullible enough to believe him.

Re:Enough

"Discuss" is a word appended to an obvious, usually one line statements, that proves the poster has only basic insight into the topic and just wants to leech karma off of more insightful replies.