bumptech/stud — pull request #47 by vincentbernat (2011-10-28 21:45:50+00:00)
Title: Disable SSL renegotiation to fix CVE-2009-3555.

If OpenSSL is too old, it does not properly associate renegotiation handshakes with an existing connection, which allows man-in-the-middle attackers to insert data into HTTPS sessions, and possibly other types of sessions protected by TLS or SSL, by sending an unauthenticated request that is processed retroactively by a server in a post-renegotiation context, related to a "plaintext injection" attack, aka the "Project Mogul" issue.

If OpenSSL is recent enough, it will use SSL secure renegotiation instead (RFC 5746). However, this feature allows an attacker to trigger easily a lot of handshake which would allow to DoS the server (this kind of attack has been recently advertised by THC)

At least, there seems to be no easy way to tell if OpenSSL is vulnerable to CVE-2009-3555 and therefore, in doubt, it may be better to disable renegotiation.