Apple shared the details of valid.apple.com in a WWDC talk: https://devstreaming-cdn.apple.com/videos/wwdc/2017/701jvytnoey2yc7222/701/701_hd_your_apps_and_evol

Apple shared the details of valid.apple.com in a WWDC talk: https://devstreaming-cdn.apple.com/videos/wwdc/2017/701jvytnoey2yc7222/701/701_hd_your_apps_and_evolving_network_security_standards.mp4?dl=1 https://devstreaming-cdn.apple.com/videos/wwdc/2017/701jvytn... Slides: https://devstreaming-cdn.apple.com/videos/wwdc/2017/701jvytnoey2yc7222/701/701_your_apps_and_evolving_network_security_standards.pdf https://devstreaming-cdn.apple.com/videos/wwdc/2017/701jvytn... You can also find the client-side code if you dig around under https://opensource.apple.com/source/Security/ https://opensource.apple.com/source/Security/ It aims to cover all certificates, similar to Mozilla's CRLite.