POODLE (Padding Oracle On Downgraded Legacy Encryption) attack

 

In late 2014 an attack came to the attention of the security world known as the POODLE (Padding Oracle On Downgraded Legacy Encryption) attack. This attack showed the vulnerabilities introduced by using legacy protocols with weak encryption.

POODLE was designed to take advantage of browser communications that use SSL 3.0 to provide encryption and authentication services. In practice, SSL has been superseded by Transport Layer Security (TLS) as a means to provide secure data transmission over the Internet. The situation that allows this attack to take place occurs when a browser doesn’t support TLS but does support SSL 3.0. When the browser encounters a situation where TLS is not an option, it reverts to SSL 3.0 as its encryption option. An attacker noticing this situation can insert themselves into the communication session and force the browser to use SSL 3.0 instead.

If an attacker is able to successfully exploit this situation, they can then exploit a design defect in the SSL 3.0 technology to carry the attack further. The defect allows an attacker to alter the padding at the end of each block and thus make it less secure. If this attack continues, the attacker can eventually gain access to resources and data they should not be able to have.

In order to prevent this attack, the browser and servers should be configured in such a way as to prevent the use of SSL 3.0.