Hi!
I’ve observed what appears to be a discrepancy in the Tor Project’s obfs4proxy Debian / Ubuntu setup guide web documentation, regarding iat-mode.
The Tor Project’s post-installation guide states,
“Paste the entire bridge line into Tor Browser:
Bridge obfs4 : cert= iat-mode=0
You’ll need to replace , , and with the actual values, which you can find in the tor log.”
However, the Tor Project’s obfs4 Bridge Relay configuration guide webpage doesn’t state the requirement of the inclusion of iat-mode=0 in the torrc configuration file provided at:
https://community.torproject.org/relay/setup/bridge/debian-ubuntu/
Therefore the individual following this guide, when they view the bridge relay’s full fingerprint found inside the Tor Data Directory, for example, in Debian/Ubuntu at /var/lib/tor/pt_state/obfs4_bridgeline.txt" then the iat-mode=0 parameter is not printed.
I’m not interested in contributing to the recent debate regarding “iat-mode=0/1/2” I’m merely stating what appears to be an omission in the Debian/Ubuntu Bridge obfs4 relay webpage configuration guide for a standard obfs4 Bridge relay.
In this neutral context if the obfs4 Bridge relay is to communicate iat-mode=0 to Tor Browser clients who might be configured with iat-mode=1/2 & connecting to this obfs4 bridge relay, is the inclusion of:
ServerTransportOptions obfs4 iat-mode=0
a mandatory requirement to be added to the torrc provided at Tor Project | Debian / Ubuntu ?
Would the exclusion of iat-mode=0 in the torrc be sufficient, technically, to notify any connecting Tor Browser clients utilising iat-modes 1&2 that these modes are not available on this obfs4 Bridge relay, or does the torrc explicitly require the inclusion of ServerTransportOptions obfs4 iat-mode=0 to communicate to the Tor Browser client that iat-mode is not available on this obfs4 Bridge relay?
Is it imperative that a obfs4 Bridge relay communicates the iat mode, if so then this should probably be stipulated in the instructions at Tor Project | Debian / Ubuntu
to tally with the advice on the post install page which states,
" Paste the entire bridge line into Tor Browser: Bridge obfs4 : cert= iat-mode=0
To summarise, if iat-mode=0 is excluded from the torrc then the iat-mode will not be included in the full obfs4 Bridge relay fingerprint, displayed on the obfs4 Bridge relay Post Install webpage guide at Tor Project | Post-install
To reiterate, this post is not intended to reignite the debate surrounding the use of iat-mode.
It’s to help clarify the need/no need for the inclusion of ServerTransportOptions obfs4 iat-mode= in the torrc of a standard configuration of a obfs4 bridge relay.
If anyone feels prompted by this post to engage in further discussion regarding the use of iat=mode, please start a new topic. Thanks.