Date: Mon, 24 Oct 2011 14:14:04 +0000
From: rm@...fault.net
To: full-disclosure@...ts.grok.org.uk
Subject: THC SSL DOS tool released

Hi,

http://thehackerschoice.wordpress.com/2011/10/24/thc-ssl-dos/
http://www.thc.org/thc-ssl-dos/

Today the German hacker group "The Hacker's Choice" officially
released a new DDoS tool. The tool exploits a weakness in SSL to kick a
server off the Internet.

Technical details can be found at http://www.thc.org/thc-ssl-dos.

"We decided to make the official release after realizing that this tool
leaked to the public a couple of months ago" said a member of THC who
wants to remain anonymous.

The tool departs from traditional DDoS tools: It does not require any
bandwidth and just a single attack computer ("bot").

The THC-SSL-DOS attack is en par with other resource exhausting DDoS
attacks. Some of those methods played a vital role in demonstrations
against oppressive governments (like the DDoS attack against Iran's
leader) and against companies that violate free speech (like the DDoS
attack against Mastercard for closing Wikileak's non-profit donation
account because of an alleged typo/misspelling in the application form).

"Here at THC the rights of the citizen and the freedom of speech are
the core of our research", says a member of THC in a private interview
this morning.

"We are hoping that the fishy security in SSL does not go unnoticed. The
industry should step in to fix the problem so that citizens are safe and
secure again. SSL is using an aging method of protecting private data
which is complex, unnecessary and not fit for the 21st century.", Says a
THC member, referring to 3 major vulnerabilities disclosed in SSL over
the past 3 years.

To list the 3 major vulnerabilities here THC explains: "In 2009 a
vulnerability was disclosed that broke the encryption of SSL. De-facto
making all SSL traffic unsafe. In 2011 various Certification Authorities
got hacked. De-facto making all SSL traffic unsafe _again_."

"We warned in 2002 about giving hundreds of commercial companies (so
called Certification Authorities) a master key to ALL SSL traffic.", says
Fred Mauer, a senior cryptographer at THC. "Only a real genius can come
up with such an idea!."

"And last but not least the immense complexity of SSL Renegotiation
strikes again in 2011 with the release of THC-SSL-DOS."

It's time for a new security model that adequately protects the
citizens..

The THC-SSL-DOS tool is a Proof Of Concept tool to disclose fishy
security in SSL. It works great if the server supports SSL
Renegotiation. It still works if SSL Renegotiation is not supported but
requires more bots and some modifications before an effect can be seen.

Our tests reveal that the average server can be taken down from a single
IBM laptop through a standard DSL connection.

Taking on larger server farms who make use of SSL Load balancer required
20 average size laptops and about 120kbit/sec of traffic.

All in all superb results.

Interesting here is that a security feature that was supposed to make

SSL Renegotiation was invented to renegotiate the key material of an SSL
connection. This feature is rarely used. In fact we could not find any
software that uses SSL Renegotiation. Yet it's enabled by default by
most servers.

An old saying comes true all over again: Complexity is the enemy of
security.

"Renegotiating Key material is a stupid idea from a cryptography
standpoint. If you are not happy with the key material negotiated at the
start of the session then the session should be re-established and not
re-negotiated", says THC.

-rm


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