Feeds

Microsoft gives temporary fix for info leak in ASP.Net

'Padding oracle' muzzled

The Power of One eBook: Top reasons to choose HP BladeSystem

Microsoft has issued a temporary fix for a cryptographic weakness in widely used web development software that allows attackers to read password files and other sensitive data.

The workaround issued late Friday addresses what is known as a “cryptographic padding oracle” in ASP.Net, a series of web development programs that run on top of Microsoft's Internet Information Services, or IIS. The weakness, which was demonstrated last week at the Ekoparty conference in Argentina, makes it possible for outsiders to read or tamper with sensitive data that is supposed to remain encrypted.

In cryptography parlance, an oracle is something that unintentionally reveals subtle clues about the encrypted contents. The vulnerability in ASP.Net can be exploited by sending a server huge numbers of queries and then analyzing the differing error messages that result. By repeating the process over and over, attackers can read the ASP.Net View State, which is used to keep track of changes made to web forms. The View State page, which can be used to store passwords, database connection strings and other sensitive data, is supposed to remain unreadable.

By tricking ASP.Net into revealing hints about the padding used to encrypt the data, attackers can eventually read or tamper with encrypted data sitting on a server running the web applications.

Microsoft on Friday acknowledged the vulnerability and said its security team was working on a patch that would plug the information disclosure hole.

In the meantime, ASP.Net users should run a script that will identify whether their systems are vulnerable. Systems that test positive should be reconfigured so that all error messages are mapped to a single error page that prevents the attacker from distinguishing among different types of errors, effectively muzzling the oracle.

Researchers Thai Duong and Juliano Rizzo last week demonstrated a point-and-click tool called POET, short for Padding Oracle Exploitation Tool, that has been updated to decrypt cookies, view states, form authentication tickets, and other sensitive data encrypted by ASP.Net. The video below provides a demonstration of the attack. ®

Designing a Defense for Mobile Applications

More from The Register

next story
Mozilla fixes CRITICAL security holes in Firefox, urges v31 upgrade
Misc memory hazards 'could be exploited' - and guess what, one's a Javascript vuln
How long is too long to wait for a security fix?
Synology finally patches OpenSSL bugs in Trevor's NAS
Don't look, Snowden: Security biz chases Tails with zero-day flaws alert
Exodus vows not to sell secrets of whistleblower's favorite OS
Roll out the welcome mat to hackers and crackers
Security chap pens guide to bug bounty programs that won't fail like Yahoo!'s
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
Researcher sat on critical IE bugs for THREE YEARS
VUPEN waited for Pwn2Own cash while IE's sandbox leaked
Four fake Google haxbots hit YOUR WEBSITE every day
Goog the perfect ruse to slip into SEO orfice
prev story

Whitepapers

Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Top 8 considerations to enable and simplify mobility
In this whitepaper learn how to successfully add mobile capabilities simply and cost effectively.
Seven Steps to Software Security
Seven practical steps you can begin to take today to secure your applications and prevent the damages a successful cyber-attack can cause.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.