Tag Archives: CRIME

TLS/SSL Vulnerabilities

“Which SSL ciphers should I disable?”

A client recently gave me a list of their supported ciphers and asked me which SSL ciphers they should disable – effectively looking for the most secure SSL ciphers they can use. Instead of the fast answer of “disable the insecure ones”, I thought I’d try and write up something useful.

So here’s a handy reference guide I’m working on. This has been time consuming to develop and no doubt will be added to over time. This isn’t intended to be read from start-to-finish, but is more of a handy SSL/TLS issue cheat-sheet.

Continue reading: TLS/SSL Vulnerabilities

CRIME against TLS?

Compression Ratio Info-leak Made Easy

CRIME is an attack against SSL, like Heartbleed, but it has a much smaller probability of exploitation. The authors of CRIME also wrote the BEAST attack. The attack can allow an attacker to recover web cookies and thereby perform session hijacking attacks, much like BEAST and the specific restrictions for the attack are similar. The attacker requires the ability to repeatedly inject predictable data whilst monitoring the resulting encrypted traffic. This requires the attacker to achieve two main prerequisites before the attack is possible: the attacker must be able to observe network traffic and manipulate the victim’s browser to submit requests to the target site.

The manipulation could be possible through Cross-site scripting attacks; JavaScript is not required and an attack could be possible with HTML Injection alone however it would be less efficient.

For CRIME to be possible the server must support compression of the request before encryption. TLS supports DEFLATE which is vulnerable, as is SPDY. The client must also support compression but only a small percentage of browsers do.