ericlaw

Download Blocking by File Type

I’ve previously spoken about the magic of the File Type Policies component — a mechanism that allows files to be classified by their level of “dangerousness”, such that harmless files (e.g. .txt files) can be downloaded freely, whilst potentially-dangerous files (e.g. .dll files) are subjected to a higher degree of vetting and a more security-consciousContinue reading “Download Blocking by File Type”

Per-Site Permissions in Edge

Last year, I wrote about how the new Microsoft Edge browser mostly ignores Security Zones (except in very rare circumstances) to configure security and permissions decisions. Instead, in Chromium per-site permissions are controlled by settings and policies expressed using a simple syntax with limited wildcarding support. Settings Page’s Site Permissions and Group Policy Internet ExplorerContinue reading “Per-Site Permissions in Edge”

Specifying Per-Site Policy with Chromium’s URL Filter Format

Chromium-based browsers like Microsoft Edge make very limited use of Windows Security Zones. Instead, most permissions and features that offer administrators per-site configuration via policy rely on lists of rules in the URL Filter Format. Filters are expressed in a syntax that is similar to other matching rules, but different enough to cause confusion. ForContinue reading “Specifying Per-Site Policy with Chromium’s URL Filter Format”

Web Proxy Authentication

Last year, I wrote about how the new Microsoft Edge’s adoption of the Chromium stack changed proxy determination away from the Windows Service (WinHTTP Proxy Service) to similar but not identical code in Chromium. This change mostly goes unnoticed, but it can have performance and functionality implications. In today’s post, I want to explore anotherContinue reading “Web Proxy Authentication”

window.close() Restrictions

Sometimes, Web Developers are surprised to find that the window.close() API doesn’t always close the browser window. When looking at the Developer Tools console, they’ll see a message like: Scripts may close only the windows that were opened by them. Why Do Browsers Limit close()? Before we dive into what factors govern what happens whenContinue reading “window.close() Restrictions”

Sandboxing vs. Elevated Browsing (As Administrator)

The Web Browser is the most security-critical application on most users’ systems– it accepts untrusted input from servers anywhere in the world, parses that input using dozens to hundreds of parsers, and renders the result locally as fast as it can. For performance reasons, almost all code in almost all browsers is written in memory-unsafeContinue reading “Sandboxing vs. Elevated Browsing (As Administrator)”

Objectively, the best cat

On March 15, 2009 we put my cat Jill (Jillian, Jilly, Jilly Bean, Jillkin) to sleep at an emergency vet. We didn’t know for sure why her kidneys failed, but it was sudden and unexpected. At times Jill could be grumpy and stubborn, but she was usually friendly, curious, and she was always very loved. IContinue reading “Objectively, the best cat”

Simply Making Simple Fixes Simple for Chromium

Google recently introduced a cool web-based editing tool for Chromium source code, a very stripped down version of the Willy Wonka tooling Googlers get to use for non-Chromium projects. I’ve used this tool to submit two trivial change lists (CLs, aka PRs) to Chromium, but I was curious about whether this new feature would workContinue reading “Simply Making Simple Fixes Simple for Chromium”

Client Certificates and Logout

Last Updated January 19, 2022 Back in May 2020, I wrote about Client Certificate Authentication, a mechanism that allows websites to strongly validate the identity of their visitors using certificates presented by the visitor’s browser. One significant limitation for client certificate authentication is that there is no standards-based mechanism for a user to “log out”Continue reading “Client Certificates and Logout”

Web “Sessions” in Private Mode

I’ve written about Private Browsing Mode a lot previously, and I’ve written a bit about the behavior of “Session restore” previously, but one topic I haven’t covered is how “Sessions” work while in Private mode. Session Sharing Historically, one of the top-reported Private Mode issues was that users unexpectedly found that opening a new PrivateContinue reading “Web “Sessions” in Private Mode”