This article introduces the concept of “3TOFU” — a harm-reduction process when downloading software that cannot be verified cryptographically.
⚠ NOTE: This article is about harm reduction.
It is dangerous to download and run binaries (or code) whose authenticity you cannot verify (using a cryptographic signature from a key stored offline). However, sometimes we cannot avoid it. If you’re going to proceed with running untrusted code, then following the steps outlined in this guide may reduce your risk.
TOFU
TOFU stands for Trust On First Use. It’s a (often abused) concept of downloading a person or org’s signing key and just blindly trusting it (instead of verifying it).
3TOFU
3TOFU is a process where a user downloads something three times at three different locations. If-and-only-if all three downloads are identical, then you trust it.
Why 3TOFU?
The EFF’s Deep Crack proved DES to be insecure and pushed a switch to 3DES.
During the Crypto Wars of the 1990s, it was illegal to export cryptography from the United States. In 1996, after intense public pressure and legal challenges, the government officially permitted export with the 56-bit DES cipher — which was a known-vulnerable cipher.
This post will outline recommended steps to harden phpList after install to make it reasonably secure.
phpList is the most popular open-source software for managing mailing lists. Like wordpress, they have a phplist.com for paid hosting services and phplist.org for free self-hosting.
Earlier this week, it was announced that phpList had a critical security vulnerability permitting an attacker to bypass authentication and login as an administrator using an incorrect & carefully-crafted password in some cases. This bug is a result of the fact that [a] PHP is a loosely typed language and [b] the phpList team was using the ‘==‘ operator to test for equality of the user’s hashed password against the DB. This security pitfall has been known in PHP since at least 2010 (a decade ago!), but I’m sure the same mistake will be made again..
Indeed, security is porous. There’s no such thing as 100% vulnerability-free code, and phpList is no exception. But if we’re careful in adding layers of security to our infrastructure, then we might be able to protect ourselves from certain 0-days.
That said, here’s my recommended steps to making your phpList install reasonably secure.
Your browser aggrigates a *lot* of data about your computer, and it won’t hesitate to provide all of this data to a nosy web site. In fact, if a website requests a large dataset of your computer’s configuration, concatinates it together, and passes it through a hash function, the resulting hash can be farily unique.
This procedure can be done (and is done) on seperate websites to track users and their activity across multiple websites. If the same procedure [get data, concatenate, hash()] produces the same hash value when done on 2 seperate websites, the website can be fairly certain that you’re the same user. This technique for tracking users is known as Browser Fingerprinting.
Just to get an idea of how effective this is, here’s an excerpt from the above-linked article:
[The EFF] found that, over their study of around 1 million visits to their study website, 83.6% of the browsers seen had a unique fingerprint; among those with Flash or Java enabled, 94.2%. This does not include cookies!
You can test the uniqueness of your browser’s “fingerprint” using this handy EFF tool.
