lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [day] [month] [year] [list]
Date: Tue, 10 Apr 2018 20:05:05 -0400
From: Sean Buckley <>
Subject: [FD] Strong Password Generator - Biased Randomness

Hi list!

I am posting my findings here in hopes some may find it interesting, and to
provide yet another example of why not to trust browser extensions blindly.
This is the top chrome web store search result for "password generator".
It has 35,000 users. This was hardly a difficult bug to find, taking
just a few minutes, but I was unable to find it online anywhere else.

This password generator contains a logic flaw, which results in some
characters appearing more frequently than others in generated passwords.

On 2018-03-27, I reported this issue using the "support" section of
the extension's page on the chrome web store.
On 2018-04-10, I checked back again to discover that the support section for
this extension has been switched off. This extension was last updated over 5
years ago. I have concluded that the developer isn't interested in it anymore.

In fairness, despite this flaw, this password generator is
still probably better than no password generator at all.


This line of code is taken from the extension.
The array "keys" stores the characters that generated passwords can contain.
This is how a random character from the keys array is selected:
  var keyPos = Math.round(Math.random() * (keys.length - 1));

Consider generating passwords with the custom character set "ABC".
Math.random()*(keys.length-1) produces a number between 0.0 to 2.0
It shouldn't take long to conclude that a random value between
0.0 and 2.0, when rounded, will produce 1 twice as often as either 0 or 2

Here are some passwords I generated using the character set "ABC":

A appears 64 times, B appears 127 times, and C appears 65 times

Sent through the Full Disclosure mailing list
Web Archives & RSS:

Powered by blists - more mailing lists