Proposal to mitigate insecure protocols over Tor

Roger Dingledine arma at
Thu Jan 17 20:56:56 UTC 2008

On Thu, Jan 17, 2008 at 12:18:00PM -0700, Kevin Bauer wrote:
> Title: Block Insecure Protocols by Default
> Author: Kevin Bauer & Damon McCoy

Hi Kevin,

Thanks for the proposal. I've been pondering something similar
lately. I've got a few questions below.

> 	POP and IMAP:10,326 connections
> 	Telnet: 8,401 connections
> 	FTP: 3,788 connections

Were (many of) these FTP username/password pairs anon-ftp or were they
actual logins?

> 	As an initial step towards mitigating the use of the above-mentioned
> 	insecure protocols, we propose that the default ports for each respective
> 	insecure service be blocked at the Tor client's socks proxy. These default
> 	ports include:
> 	  23 - Telnet
> 	109 - POP2
> 	110 - POP3
> 	143 - IMAP

Right, this seems like it's not a crazy idea. I had been pondering
setting up some Tor controller status events "insecure port used" that
Vidalia could monitor to inform its user that they had just tried doing
something dangerous.

> 	  BlockInsecureProtocols 0|1
> 	  WarnInsecureProtocols 0|1

This seems like a fine interface. The status events I mention above
could still be useful, because if Block is default, there will be a lot
of confused users unless Vidalia pops up a little something explaining
that what they just tried may not be a smart move.

(Vidalia could also have the ability to turn off the warnings, for users
who know they want to do it. But we need to be careful in that regard --
see the Firefox comments below.)

> 	When the warning flag is activated, a message should be displayed to
> 	the user similar to the message given when Tor's socks proxy is given an IP
> 	address rather than resolving a host name.
> 	We recommend that the default torrc configuration file block insecure
> 	protocols and provide a warning to the user to explain the behavior.

Right. I think integration into Vidalia is critical -- few users know
that Tor even *has* log messages.

> 	Finally, there are many popular web pages that do not offer secure
> 	login features, such as MySpace, and it would be prudent to provide
> 	additional rules to Privoxy to attempt to protect users from unknowingly
> 	submitting their login credentials in plain-text.

This is the big issue here. It's all well and good to block pop
connections. But there are still many ways to give up secrets on an
unencrypted (or unauthenticated) http channel.

Now, Firefox already has a pop-up warning about this! But users have
been trained to ignore it.

We're trying to move away from Privoxy towards Polipo, and to put
the application-level security/privacy smarts into Torbutton-dev So relying on Privoxy for stuff
going forward is not a good move. I wonder if there are good ways to
get Torbutton to help users with http-level issues?


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