tor-dev February 2022

tor-dev@lists.torproject.org

7 participants
7 discussions

Two features that would help load-balanced bridges
by David Fifield 01 Jun '23

01 Jun '23

After the blocking of Tor in Russia in December 2022, the number of Snowflake users rapidly increased. Eventually the tor process became the limiting factor for performance, using all of one CPU core. In a thread on tor-relays, we worked out a design where we run multiple instances of tor on the same host, all with the same identity keys, in order to effectively use all the server's CPU resources. It's running on the live bridge now, and as a result the bridge's bandwidth use has roughly doubled. Design thread https://forum.torproject.net/t/tor-relays-how-to-reduce-tor-cpu-load-on-a-s… Installation instructions https://gitlab.torproject.org/tpo/anti-censorship/team/-/wikis/Survival-Gui… Two details came up that are awkward to deal with. We have workaround for them, but they could benefit from support from core tor. They are: 1. Provide a way to disable onion key rotation, or configure a custom onion key. 2. Provide a way to set a specific authentication cookie for ExtORPort SAFE_COOKIE authentication, or a new authentication type that doesn't require credentials that change whenever tor is restarted. I should mention that, apart from the load-balancing design we settled on, we have brainstormed some other options for scaling the Snowflake bridge or bridges. At this point, none of these ideas can immediately be put into practice, because there's no way to tell tor "connect to one of these bridges at random, but only one," or "connect to this bridge, but accept any of these fingerprints." https://bugs.torproject.org/tpo/anti-censorship/pluggable-transports/snowfl… # Disable onion key rotation Multiple tor instances with the same identity keys will work fine for the first 5 weeks (onion-key-rotation-days + onion-key-grace-period-days), but after that time the instances will have independently rotated their onion keys, and clients will have connection failures unless the load balancer happens to connect them to the instance whose descriptor they have cached. This post investigates what the failure looks like: https://lists.torproject.org/pipermail/tor-relays/2022-January/020238.html Examples of what could work here are a torrc option to set onion-key-rotation-days to a large value, an option to disable onion key rotation, an option to set a certain named file as the onion key. What we are doing now is a bit of a nasty hack: we create a directory named secret_onion_key.old, so that a failed replace_file causes an early exit from rotate_onion_key. https://gitweb.torproject.org/tor.git/tree/src/feature/relay/router.c?h=tor… There are a few apparently benign side effects, like tor trying to rebuild its descriptor every hour, but it's effective at stopping onion key rotation. https://lists.torproject.org/pipermail/tor-relays/2022-January/020277.html # Stable ExtORPort authentication ExtORPort (extended ORPort) is a protocol that lets a pluggable transport attach transport and client IP metadata to a connection, for metrics purposes. In order to connect to the ExtORPort, the pluggable transport needs to authenticate using a scheme like ControlPort authentication. https://gitweb.torproject.org/torspec.git/tree/proposals/217-ext-orport-aut… tor generates a secret auth cookie and stores it in a file. When the pluggable transport process is managed by tor, tor tells the pluggable transport where to find the file by setting the TOR_PT_AUTH_COOKIE_FILE environment variable. In the load-balanced configuration, the pluggable transport server (snowflake-server) is not run and managed by tor. It is an independent daemon, so it doesn't have access to TOR_PT_AUTH_COOKIE_FILE (which anyway would be a different path for every tor instance). The bigger problem is that tor regenerates the auth cookie and rewrites the file on every restart. All the tor instances have different cookies, and snowflake-server does not know which it will get through the load balancer, so it doesn't know what cookie to use. Examples of what would work here are an option to use a certain file as the auth cookie, an option to leave the auth cookie file alone if it already exists, or a new ExtORPort authentication type that can use the same credentials across multiple instances. What we're doing now is using a shim program, extor-static-cookie, which presents an ExtORPort interface with a static auth cookie for snowflake-server to authenticate with, then re-authenticates to the ExtORPort of its respective instance of tor, using that instance's auth cookie. https://lists.torproject.org/pipermail/tor-relays/2022-January/020183.html

2 2

Interoperation with libp2p
by Mike Mestnik 07 Apr '22

07 Apr '22

https://gitlab.torproject.org/tpo/core/torspec/-/issues/64

5 5

[dappy] Willing to chat with tor devs, about name system issues/solutions
by Raphaël Fabre 27 Mar '22

27 Mar '22

Hello I'm Raphaël (fr) I just joined the tor dev mailing list. I would like to chat with tor developers, particularly if they have worked, or are interested in the issues regarding a name system for tor. I'm the lead developer of dappy https://dappy.tech , we'll launch in 2022 and I do think we have interesting properties, for the public web as well as for tor and privacy-focused web projects. We are the only name system in the world that does co-resolution, that's the way we found to maintain a consistent name system, and also avoid censorship and phishing. Our system has the following properties: - blockchain-based name system: it simply means that mapping is globally consistent, name management is distributed in the sense that a blockchain handles it, the resolver just connect to this blockchain. - Systematic co-resolution (not rotation): lookup request are always addressed to a network of independant agents: there are many instead of a single one. And then there is consensus at browser level. This prevents 90% of attacks or attempt of censorship/phishing. - Anonymous registrations - Load-balancing of names: you can attach 20 IP addresses to your name, dappy browser will try each one of them until it gets a response. - 100% encrypted/https Censorship cannot happen, neither at the storage location (blockchain) or on-the-fly at resolution time (co-resolution) We will launch in 2022 and would be thrilled to exchange with some developers or engineers. This document has lead me to the path of the tor-dev mailing list https://gitlab.torproject.org/legacy/trac/-/wikis/doc/OnionServiceNamingSys… Happy to chat Merry Christmas Raphaël Fabre Building a ultra-secure blockchain-based name system and browser https://dappy.tech

2 2

Gosling onion-to-onion specifications
by Richard Pospesel 19 Mar '22

19 Mar '22

Hi tor-dev, As part of my work with Blueprint for Free Speech, I recently gave a short presentation during the 2021 state-of-the-onion where we announced Gosling ( see https://youtu.be/mNhIjtXuVzk?t=8155 ). If you missed the talk, the tldr; is that we're developing a specification and reference implementation library for building (onion service based) anonymous+private+secure peer-to-peer applications. Essentially, we're taking what we've learned about onion-to-onion authentication from Ricochet-Refresh, extracting and improving the relevant pieces, and packaging it all in a library that developers can use to build their own anonymous+private+secure peer-to-peer applications. Our hope is that future developers will not need to be tor experts to build these types of applications. Today ,I'm happy to announce that we just made the the gosling repo on Github public! - https://github.com/blueprint-freespeech/gosling Things are little bare-bones at the moment, but the most relevant piece right now is the protocol specification here: - https://github.com/blueprint-freespeech/gosling/blob/main/docs/protocol.md You'll also find some initial prototyping work under the source directory (the pace of development should pick up come 2022). Please go take a look and feel free to respond here with any questions, concerns, criticisms, etc. Thanks! best, -Richard

1 1

Relay "Ping" Functionality
by Alexander Mages 19 Feb '22

19 Feb '22

Hello Tor-Dev, My name is Alex Mages, and I have been doing pluggable transport research with Eugene Vasserman (CC) at Kansas State University. Right now we're exploring latency-based attacks but are having trouble achieving a particular goal: a way to “ping” an arbitrary node in a client’s already-built (“live”) circuit. One-way timing is ideal but round trip time would suffice. We can glean this information during circuit construction, but what about a “live” circuit? Ideally, this would be a periodic thing Tor already keeps track of, but as an on-demand or as a byproduct/side-effect of a different function would also work. We have not been able to find a way to do this within the Tor (sub)protocol specs or the control port spec. Any ideas, suggestions, or criticisms would be greatly appreciated. Thanks, Alex Mages

3 4

onionoo overload_general_timestamp (prop 328)
by nusenu 10 Feb '22

10 Feb '22

Hi, in onionoo all timestamps used to be in the format YYYY-MM-DD hh:mm:ss Proposal 328 has timestamps in this same format https://gitlab.torproject.org/tpo/core/torspec/-/blob/main/proposals/328-re… The newly added prop328 fields in oninoo appear to break with that convention https://metrics.torproject.org/onionoo.html#details_relay_overload_general_… Here is an example for an onionoo overload_general_timestamp which appears to be at millisecond granularity (the source has a granularity of an hour): 1636038000000 Was there a particular motivation for this format change and granularity? And what do you think about changing it to use the YYYY-MM-DD hh:mm:ss format for consistency and having a direct human readable format here as well? related: Karsten used to maintain onionoo protocol documentation/changelog and versions: https://metrics.torproject.org/onionoo.html#versions Is that and the 'version' field in onionoo no longer maintained? (since it didn't change with the new fields) kind regards, nusenu -- https://nusenu.github.io

2 3

onbasca - the next-generation bandwidth scanner
by Georg Koppen 10 Feb '22

10 Feb '22

Hello everyone! As many of you know we have been working on a simple bandwidth scanner (sbws) over the last years to deal with the old and unmaintained Torflow code on our bandwidth authorities. We learned a lot during that process, especially after we started to replace Torflow with the new sbws code on bandwidth authorities (today sbws is powering a majority of them, yay!). We realized that we needed to improve the robustness and testability of the code significantly, in particular as we want to build exciting features like loadbalancing capability on top of it and decided it would be easier to do so in a new tool: welcome onbasca. Onbasca takes the best out of sbws and makes the code easier to test and more robust for future improvements by deploying a database management system where we previously dealt with JSON files only.[1] The code repository lives in our network-health group[2] and is open for contributions. Get in touch in case you are interested, everyone is welcome! Georg [1] For a more detailed overview over the bandwidth scanner history, design issues we encountered in sbws, and decisions we made, see: https://tpo.pages.torproject.net/network-health/onbasca/history.html. [2] https://gitlab.torproject.org/tpo/network-health/onbasca

2 1

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

tor-dev February 2022