Hi,I have an updated proposal which addresses your concerns, along with David Goulet's comments on GitLab.
On 2021-09-07 12:47, s7r wrote:
Hi Neel, Please add a "MOTIVATION" section and explain in detail why is this needed for the network/heath team and how will it improve things? Also include in the "MOTIVATION" section the following: - Why not play with the Exit/Guard to achieve the same goal, why not possible? what is the goal -- we need to know the goal to further discuss this.
I have an updated proposal which addresses your concerns, along with David Goulet's comments on GitLab.
- It's something at Directory Authority Level only? So the client / relay operator has no decision whatsoever for this flag? What are the tie breakers or based on what is this assigned?
This is something assigned at the dirauth-level.
- How will this work in a wonderful feature I am dreaming of where all the relays are Exits and maybe we make walking onions working?
I believe it shouldn't affect these scenarios, but have mentioned we should look out for them.
P.S. Rendezvous point is NOT a less powerful position (at least from an onion service server/operator point of view), unless you are using vanguards plugin by Mike with rendguard component activated. Because it's always chosen by the client connecting to the onion service, and we should assume the client is always ~LE~ evil. Trust me on this :)
I have also updated this to be a strictly Middle-only flag, and am not giving rendezvous capabilities to MiddleOnly relays.
Sorry about this, but I have taken more-or-less a so-called "break" from Tor development for a while. I am technically a volunteer, and my $DAYJOB is at "Big Tech" (don't judge, that's where I found work).
I also got FreeBSD "commit bit" (not every Tor developer uses Debian) which took time away from Tor volunteer efforts. I am only getting back to Tor development as of the past week or two, so I need to refresh my memory.
Going back, this update also completes the missing paragraph reported by Ian, that seemed to miss me in the original proposal.
-Neel Chauhan
Filename: 334-middle-only-flag.txt Title: A dirauth flag to mark Relays as Middle-only Author: Neel Chauhan Created: 2021-09-07 Status: Open 1. Introduction The Health Team often deals with a large number of relays with an incorrect configuration (e.g. not all relays in MyFamily), or needs validation that requires contacting the relay operator. It is desirable to put the said relays in a less powerful position, such as a middle only flag that prevents a relay from being used in more powerful positions like an entry guard or an exit relay. [1] 1.1. Motivation The proposed middle-only flag is needed by the Health Team to prevent misconfigured relays from being used in positions capable of deanonymizing users while the team evaluates the relay's risk to the network. An example of this scenario is when a guard and exit relay run by the same operator has an incomplete MyFamily, and the same operator's guard and exit are used in a circuit. The reason why we won't play with the Guard and Exit flags or weights to achieve the same goal is because even if we were to reduce the guard and exit weights of a misconfigured relay, it could keep some users at risk of deanonymization. Even a small fraction of users at risk of deanonymization isn't something we should aim for. One case we could look out for is if all relays are exit relays (unlikely), or if walking onions are working on the current Tor network. This proposal should not affect those scenarios, but we should watch out for these cases. 2. The MiddleOnly Flag We propose a consensus flag MiddleOnly. As mentioned earlier, relays will be assigned this flag from the directory authorities. What this flag does is that a relay must not be used as an entry guard or exit relay. This is to prevent issues with a misconfigured relay as described in Section 1 (Introduction) while the Health Team assesses the risk with the relay. 3. Implementation details The MiddleOnly flag can be assigned to relays whose IP addresses are configured at the directory authority level, similar to how the BadExit flag currently works. In short, if a relay's IP is designated as middle-only, it must assign the MiddleOnly flag, otherwise we must not assign it. Relays which haven't gotten the Guard or Exit flags yet but have IP addresses that aren't designated as middle-only in the dirauths must not get the MiddleOnly flag. This is to allow new entry guards and exit relays to enter the Tor network, while giving relay administrators flexibility to increase and reduce bandwidth, or change their exit policy. 3.1. Client Implementation Clients should interpret the MiddleOnly flag while parsing relay descriptors to determine whether a relay is to be avoided for non-middle purposes. If a client parses the MiddleOnly flag, it must not use MiddleOnly-designated relays as entry guards or exit relays. 3.2. MiddleOnly Relay Purposes If a relay has the MiddleOnly flag, we do not allow it to be used for the following purposes: * Entry Guard * Exit * Onion Service Rendevous Point * Onion Service Intro Point * Onion Service HSDir * Fallback Directories The reason for this is to prevent a misconfigured relay from being used in places where they may know about the client directly. This is in case certain misconfigured relays are used to deanonymize clients. 4. Consensus Method We also propose a new consensus method 32, which is to only use this flag if and when all authorities understand the flag and agree on it. This is because the MiddleOnly flag impacts path selection for clients. 5. Citations [1] - https://gitlab.torproject.org/tpo/core/tor/-/issues/40448
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