OpenSSL just released an update that allows for a "Man-in-the-Middle" attack on any webserver using the old SSLv2. The vulnerability allows an attacker to decrypt an intercepted connection by repeatedly using SSLv2 to make connections to a server. In the process, the attacker learns a few bits of information about the encryption key each time. Ultimately, the attacker can learn the encryption key and use it to decrypt anything the user sends to the webserver.
Fear not, however, if you are currently offloading your SSL on the BIG-IP. By utilizing the default configuration in your BIG-IP SSL profile, your applications are not vulnerable. The only two situations your applications might be vulnerable in the data path are:
- You are passing SSL through the BIG-IP to your application servers and NOT offloading. If this is your situation, there is an iRule mitigation you can implement that was developed for the POODLE attack that will also defend in this case.
- You have enabled the COMPAT ciphers in your SSL profile. See David's notes below in the comments for more details.
For BIG-IP version 12.0, the COMPAT cipher string for SSL profile on the data plane won't expose the issue unless you explicitly use the COMPAT cipher string with SSLv2 enabled (“COMPAT+SSLV2”) because this configuration enables SSLv2 only. I'm not sure why anyone would ever use this configuration, but in an effort to provide full disclosure, I wanted to share that it's an available option...and I highly discourage anyone from using it!
For BIG-IP versions 10.1.0 thru 10.2.2, the cipher string “ALL” in addition to “COMPAT” will expose the issue because SSLv2 was included in both groupings in those older versions. Also, the SSL profile includes an option called “NO SSLv2” which can be used to disable the protocol at the profile level.
OpenSSL has already released a new version to address this vulnerability, so get out there and implement the new version if you are one of the vulnerable webservers. Better, though, is to completely remove SSLv2 from the options your webserver offers when serving up security protocols.
Check back here for more updates as other information on this attack becomes available.
