Linux Bug Leaves USA Today, Other Top Sites Vulnerable To Serious Hijacking Attacks (arstechnica.com)

Dan Goodin, reporting for Ars Technica: Computer scientists have discovered a serious Internet vulnerability that allows attackers to terminate connections between virtually any two parties and, if the connections aren't encrypted, inject malicious code or content into the parties' communications. The vulnerability resides in the design and implementation of RFC 5961, a relatively new Internet standard that's intended to prevent certain classes of hacking attacks. In fact, the protocol is designed in a way that it can easily open Internet users to so-called blind off-path attacks, in which hackers anywhere on the Internet can detect when any two parties are communicating over an active transmission control protocol connection. Attackers can go on to exploit the flaw to shut down the connection, inject malicious code or content into unencrypted data streams, and possibly degrade privacy guarantees provided by the Tor anonymity network. At the 25th Usenix Security Symposium on Wednesday, researchers with the University of California at Riverside and the US Army Research Laboratory will demonstrate a proof-of-concept exploit that allows them to inject content into an otherwise legitimate USA Today page that asks viewers to enter their e-mail and passwords.

Comments

R.I.P. IPsec

[OrangeTide]

I wrote a tiny bit of IPsec code about 15+ years ago, for a router company thinking it would take off. It still hasn't taken off, and I've given up on anyone giving two shits about rolling out IPsec in any significant way.

Not A Linux Bug

[StormReaver]

The bug is in the RFC, which Linux implements faithfully. I find it funny that the only reason Linux is the only mainstream operating system that is vulnerable is because it's the only mainstream operating system that implements the RFC. And yes, it is a very critical bug, one which the RFC needs to address, too.

Also, the fix was committed a few weeks ago, but distributions haven't pushed it out yet (at the time the arstechnica article was written).

Re:TLS

[omnichad]

For many websites using a cert is simply to expensive and may require a dedicated IP.

Answer: Let's Encrypt and SNI. There is no excuse. If you can't do that, find a new host.

Re:RFC5961 is flawed

[kamakazi]

Actually, the global rate limiting may not be the problem, the fixed limit may be. If the global rate limit were periodically randomly set, instead of 100/second, somewhere between 95 and 105 per second, then this attack would not work. It depends completely on knowing the global rate limit, and assumes there is no other traffic generating challenge ACKs.

A per connection rate limit would not accomplish the purpose of a rate limit, but an unknown global rate limit that changed fairly often would prevent this information leakage. Based on the attack time in the paper I think a rate limit that reset to a random value at a random time from 3-5 seconds would make this attack useless.

If the time the limit changes is fixed then the attacker can synchronize with the reset clock and still achieve a workable attack window by probing to determine the new limit.

I suppose you could skip the lifetime and just change it every second, since then the attacker would have great difficulty synchronizing with the limit counter as described in the article.