Man-In-the-Middle Vulnerability For SSL and TLS

imbaczek writes "The SSL 3.0+ and TLS 1.0+ protocols are vulnerable to a set of related attacks which allow a man-in-the-middle (MITM) operating at or below the TCP layer to inject a chosen plaintext prefix into the encrypted data stream, often without detection by either end of the connection. This is possible because an 'authentication gap' exists during the renegotiation process, at which the MitM may splice together disparate TLS connections in a completely standards-compliant way. This represents a serious security defect for many or all protocols which run on top of TLS, including HTTPS."

Comments

Re:How does this compromise SSL?

[Anonymous Coward]

Actually, this isn't true. This attack only allows for injecting data into the request from the client to the server. The attacker doesn't even get to see the result, much less modify it.

Basically, the only thing the attacker gets is the ability to make the client's browser request whatever the attacker wants. You know, the kind of thing you could do with a simple injected IMG tag.

Client certificates only? is this important?

[Xylantiel]

The linked articles only discuss authentication via client certificates, which seems pretty rare currently. How does this vulnerability actually impact the "usual" web commerce usages of SSL, which involves a server certificate? Also it does not appear that there is any way to force a re-negotiation from outside. And while re-negotiation appears common for client certs, I would expect it to be somewhat uncommon for server certs except for the initial up-negotiation to a secure connection for TLS. How important is this for the common-use cases of e-commerce and banking?