New Tool Eases CSRF Bug Discovery

If you think Cross-Site Request Forgery (CSRF) vulnerabilities aren't easy to find or exploit on your Website, think again. A researcher has released a tool that makes it easier to test sites for CSRF vulnerabilities -- and find out how prevalent the emerging bugs really are.

The online tool lets you use the HTTP "post" request to check for CSRF bugs. Chris Shiflet, principal with OmniTI and creator of the newly released CSRF Redirector tool, says there's a misconception among Web developers that testing for CSRF bugs with a "post" request is more difficult or inconvenient, so CSRF attacks using "post" aren't as common as those using an HTTP "get" request.

"I think this can help highlight how easily CSRF vulnerabilities can be exploited, even when the forged request must be a 'post' request," Shiflet says. "Often, inconvenience is considered a safeguard" for a site, but that's not really the case.

It's easier to test for CSRF bugs with a "get" request because visiting a URL initiates such a request, while a "post" requires the tester to build an HTML form, Shiflet says. "So any bug that can be exploited with 'get' is easy to test for," he says. "It's marginally less convenient with 'post,' so this [tool] is trying to remove that slight barrier of inconvenience."

CSRF worries Web researchers because it can potentially cause serious damage to Websites and enterprises. (See CSRF Bug Runs Rampant, Eight Vulnerabilities You May Have Missed, and CSRF Vulnerability: A 'Sleeping Giant'.)

"For some reason, CSRF seems to be hovering just below the radar of most Web developers," Shiflet says. "And in my experience [so far], it seems to be exploited far less [than XSS] as well."

To see how much interest hackers have in CSRF, Shiflet even purposely placed a CSRF bug on his personal Website and then mentioned it in his blog. Yet, only once has someone tried to exploit it, he says. "I get cross-site scripting-related attack [attempts] in the hundreds a day... I find that very interesting. There are far fewer attempts on CSRF."

He thinks it's more of an awareness issue, rather than a complexity issue, since XSS is more widely known and understood than CSRF. "Exploiting CSRF is equally as easy as cross-site scripting."

"This doesn't change the exploitability of the attack vector much -- certainly, people were able to do this before, and will continue to be able to do this without the tool," says RSnake, a.k.a. Robert Hansen, CEO at SecTheory LLC. "However, what it does provide is the ability for researchers to quickly prototype examples to demonstrate the problem."

— Kelly Jackson Higgins, Senior Editor, Dark Reading