[TLS] Read-only vs. read-write proxies

[Yaron Sheffer <[e-mail]>]

First, I strongly dislike this type of corporate proxies, and would take the German constitutional regime any time. But in other free countries, this scenario is perfectly OK (legal and socially acceptable), and we need to cater for this use case.

If we break the TLS architecture as proposed here, we will have killed forever any chance of having TLS-level mutual authentication (TLS-PSK, TLS-SRP). This is IMHO too high a price for the benefits of R/W proxies.

I have not been convinced by David's explanation of the need for R/W proxies, nor by Yoav's use case. A malware detection proxy can drop the connection precisely at the time malware is detected: the Word document would not be received in its entirety and would be rejected by the client. Even if a partial document is acceptable (e.g. JPEG), a partial malware is (hopefully) not effective.

What are the reasons proxies need to modify the stream?

- Purely informational app-level insertion, of the "sent from my iPhone" kind. The *client* has a trusted channel to the proxy, and if this is needed, the client can insert this stuff.

- Security-specific signaling, of the "no spam detected here" kind. The server wouldn't trust the proxy with that anyway (this is a client-side proxy!) so this is not useful.

- Malware detection: just ax the connection.

- Other reasons?

Lastly, it is important that the server should know of the proxy's presence, even if the indication relies on the client's and/or the proxy's good will. I can think of banks who still use passwords for client auth, but would not allow logins where that password is clearly intercepted by a third party.

Thanks,

    Yaron