Matthew McPherrin

419 Followers
309 Following
348 Posts
SRE at Let's Encrypt, though these toots are my own.
new tech warcrime

ppl always complain that the clock on my microwave never shows the right time bcs i cant be assed to set it manually

so now i have an unfuck-microwave.sh cronjob which briefly kills its power every day at midnight
It looks like some of this data is incorrect due to a Firefox bug, which I've filed as https://bugzilla.mozilla.org/show_bug.cgi?id=1972339
1972339 - cert.validation_success_by_ca bin collision between CAs and unknown entries in RootCertificateTelemetryUtils.h

NEW (nobody) in Core - Security: PSM. Last updated 2025-06-16.

Firefox's telemetry has data on how many times a CA is used to successfully validate certificates. This is a pretty good measure for how "big" a CA is. The data is hard to view in Mozilla's site, so I've made a script to combine a few data sources and graph it! https://github.com/mcpherrinm/cert-count

Inspired by the classic xeyes program, I made a thing:

ssh teyes.fly.dev

Or go install github.com/mcpherrinm/teyes@latest && teyes

Give your mouse a wiggle over the terminal!

I'll be speaking at the Ontario Cryptography Day!

https://ontario-crypto-day.github.io/

Where: University of Waterloo Davis Centre (DC) 1301 and 1302
When: Friday, June 6, 2025, from 10am to approx. 4:30pm

I hope anyone in the area interested in cryptography is able to attend. It's a free event, but registration is required.

Ontario Cryptography Day

June 6, 2025 • University of Waterloo

Ontario Cryptography Day
Of all the things I didn’t expect to ever happen, iOS Safari actually got a certificate viewer in 18.4! https://webkit.org/blog/16574/webkit-features-in-safari-18-4/#connection-security
WebKit Features in Safari 18.4

Safari 18.4 is here!

WebKit
We've issued our first short-lived (6 day) certificate! https://letsencrypt.org/2025/02/20/first-short-lived-cert-issued/
We Issued Our First Six Day Cert

Earlier this year we announced our intention to introduce short-lived certificates with lifetimes of six days as an option for our subscribers. Yesterday we issued our first short-lived certificate. You can see the certificate at the bottom of our post, or here thanks to Certificate Transparency logs. We issued it to ourselves and then immediately revoked it so we can observe the certificate’s whole lifecycle. This is the first step towards making short-lived certificates available to all subscribers.

Chrome has published version 1.6 of their root store policy.

Notably, this contains a timeline for deprecating use of the TLS Client Auth extended-key-usage inside the PKIs included in their program.
If you currently use TLS Client Auth from a publicly trusted CA, you may need to take action.

> ... certificates issued on or after June 15, 2026 MUST include the extendedKeyUsage extension and only assert an extendedKeyUsage purpose of id-kp-serverAuth.

https://www.chromium.org/Home/chromium-security/root-ca-policy/#32-promote-use-of-dedicated-tls-server-authentication-pki-hierarchies

Chrome Root Program Policy, Version 1.6

Congratulations to the Firefox team for shipping CT enforcement!

> Starting in Firefox 135, Certificate Transparency is now enforced on all desktop platforms.

https://groups.google.com/a/mozilla.org/g/dev-security-policy/c/OagRKpVirsA/m/Q4c89XG-EAAJ

Certificate Transparency is now enforced in Firefox on desktop platforms starting with version 135

I'm speaking at #SREcon in Santa Clara this March! Come learn how Let's Encrypt issues millions of certificates with just a handful of staff and servers! https://www.usenix.org/conference/srecon25americas/presentation/mcpherrin
Improving the SRE Experience for 10 Years as a Free, Open, and Automated Certificate Authority | USENIX