guard relays | Tor Blog

Research problem: better guard rotation parameters

Tor's entry guard design protects users in a variety of ways.

16 comments

Upcoming Events

October 21, 2019 - October 27, 2019

Mozz Fest (London)

October 30, 2019

Swiss Web Security Day (Bern)

November 01, 2019

Driving IT (Copenhagen)

See All Upcoming Events

Recent Updates

New release: Tor 0.4.1.6

We have a new stable release today. If you build Tor from source, you can download the source code for 0.4.1.6 from the download page on the website. Packages should be available within the next several weeks, with a new Tor Browser in the next week or two.

This release backports several bugfixes to improve stability and correctness. Anyone experiencing build problems or crashes with 0.4.1.5, or experiencing reliability issues with single onion services, should upgrade.

Changes in version 0.4.1.6 - 2019-09-19

Major bugfixes (crash, Linux, Android, backport from 0.4.2.1-alpha):
- Tolerate systems (including some Android installations) where madvise and MADV_DONTDUMP are available at build-time, but not at run time. Previously, these systems would notice a failed syscall and abort. Fixes bug 31570; bugfix on 0.4.1.1-alpha.
- Tolerate systems (including some Linux installations) where madvise and/or MADV_DONTFORK are available at build-time, but not at run time. Previously, these systems would notice a failed syscall and abort. Fixes bug 31696; bugfix on 0.4.1.1-alpha.
Minor features (stem tests, backport from 0.4.2.1-alpha):
- Change "make test-stem" so it only runs the stem tests that use tor. This change makes test-stem faster and more reliable. Closes ticket 31554.

New Release: Tor 0.4.2.1-alpha

There's a new alpha release available for download. If you build Tor from source, you can download the source code for 0.4.2.1-alpha from the download page on the website. Packages should be available over the coming weeks, with a new alpha Tor Browser release in the next couple of weeks.

Remember, this is an alpha release: you should only run this if you'd like to find and report more bugs than usual.

This is the first alpha release in the 0.4.2.x series. It adds new defenses for denial-of-service attacks against onion services. It also includes numerous kinds of bugfixes and refactoring to help improve Tor's stability and ease of development.

Changes in version 0.4.2.1-alpha - 2019-09-17

Major features (onion service v3, denial of service):
- Add onion service introduction denial of service defenses. Intro points can now rate-limit client introduction requests, using parameters that can be sent by the service within the ESTABLISH_INTRO cell. If the cell extension for this is not used, the intro point will honor the consensus parameters. Closes ticket 30924.
Major bugfixes (circuit build, guard):
- When considering upgrading circuits from "waiting for guard" to "open", always ignore circuits that are marked for close. Previously we could end up in the situation where a subsystem is notified of a circuit opening, but the circuit is still marked for close, leading to undesirable behavior. Fixes bug 30871; bugfix on 0.3.0.1-alpha.

Join the Global Climate Strike 20-27 September

Humanity is facing a climate crisis.

Tor’s Bug Smash Fund: $86K Raised!

To the Tor community: we owe you a thank you!