Arti 0.0.3 is released

Arti 0.0.3 is released: Configuration, predictive circuits, and more! 

Arti is our ongoing project to create a working embeddable Tor client in Rust. It’s nowhere near ready to replace the main Tor implementation in C, but we believe that it’s the future.

We're working towards our 0.1.0 milestone in early March, where our main current priorities are stabilizing our APIs, and resolving issues that prevent integration. We're planning to do releases every month or so until we get to that milestone.

Please be aware that every release between now and then will probably break backward compatibility.

So, what's new in Arti 0.0.3?

Our biggest API change is that we've completely revamped our configuration system to allow changing configuration values from Rust, while the TorClient instance is running.

In the background, we've also implemented a system for “preemptive circuit construction.” Based on which ports you've used in the recent past, it predicts which circuits you'll likely need in the future, and constructs them in advance to lower your circuit latency.

There are also a bunch of smaller features, bugfixes, and infrastructure improvements; see the changelog for a more complete list.

And what's next?

Between now and March, we're going to be focused on three kinds of improvements:

• Those that will require API breakage.
• Those based on developer feedback.
• Those that resolve technical debt.

We'll try to do our next release around the start of February. It might have a new error system, support for bootstrap reporting, easier setup, and more!

Here's how to try it out

We rely on users and volunteers to find problems in our software and suggest directions for its improvement. Although Arti isn't yet ready for production use, it should work fine as a SOCKS proxy (if you're willing to compile from source) and as an embeddable library (if you don't mind a little API instability).

Assuming you've installed Arti (with cargo install arti, or directly from a cloned repository), you can use it to start a simple SOCKS proxy for making connections via Tor with:

$ arti proxy -p 9150

and use more or less as you would use the C Tor implementation!

(It doesn't support onion services yet. If compilation doesn't work, make sure you have development files for libsqlite installed on your platform.)

For more information, check out the README file. (For now, it assumes that you're comfortable building Rust programs from the command line). Our CONTRIBUTING file has more information on installing development tools, and on using Arti inside of Tor Browser. (If you want to try that, please be aware that Arti doesn't support onion services yet.)

When you find bugs, please report them on our bugtracker. You can request an account or report a bug anonymously.

And if this documentation doesn't make sense, please ask questions! The questions you ask today might help improve the documentation tomorrow.

Call for comments—Urgent!

We need feedback on our APIs. Sure, we think we're making them more complete and ergonomic… but it's the users' opinion that matters!

Here are some ideas of how you can help:

1. You can read over the high-level APIs for the arti-client crate, and look for places where the documentation could be more clear, or where the API is ugly or hard to work with.

2. Try writing more code with this API: what do you wish you could do with Tor in Rust? Give it a try! Does this API make it possible? Is any part of it harder than necessary? (If you want, maybe clean up your code and contribute it as an example?)

Acknowledgments

Thanks to everybody who has contributed to this release, including dagon, Daniel Eades, Muhammad Falak R Wani, Neel Chauhan, Trinity Pointard, and Yuan Lyu!

And thanks, of course, to Zcash Open Major Grants (ZOMG) for funding this project!

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Security release: Arti 1.2.3. (Please upgrade.)

We have released updates to Arti today, to resolve a pair of security issues related to circuit construction for onion services.

These vulnerabilities affect the crate tor-circmgr 0.18.0, released along with Arti version 1.2.2. They are fixed in tor-circmgr 0.18.1. (Fixes will also appear in Arti version 1.2.4, to be released on our regular schedule at the start of June.)

Who is affected

If you use arti to connect to onion services, or to run onion services, and you are using Arti 1.2.2 or tor-circmgr 0.18.0, you should upgrade.

(In Arti 1.2.1 and earlier, vanguards were still an experimental feature, or absent, so those versions are classified as "not affected", but downgrading to these versions will not improve your security.)

Upgrade instructions

If you installed Arti via cargo install, use this command to update:

cargo install --locked --features=full arti
# or whatever --features you used before

If you obtained Arti as source code from git, fetch the tag arti-v1.2.3 and rebuild, with cargo build --locked --release --features=full -p arti.

The issues

Both issues affect circuit construction when vanguards are enabled, and affect the length.

First, when building anonymizing circuits to or from an onion service with 'lite' vanguards (the default) enabled, the circuit manager code would build the circuits with one hop too few. This makes users of this code more vulnerable to some kinds of traffic analysis when they run or visit onion services. This bug is tracked as issue #1409, and as TROVE-2024-003. Its severity is "high".

Second, when 'full' vanguards are enabled, some circuits are supposed to be built with an extra hop to minimize the linkability of the guard nodes. In some circumstances, the circuit manager would build circuits with one hop too few, making it easier for an adversary to discover the L2 and L3 guards of the affected clients and services. This issue is tracked as issue #1400, and as TROVE-2024-004. Its severity is "medium".