For example, CAs present in Firefox, that might give you pause: Beijing Certificate Authority, China Financial CA, Guang Dong CA
The CA system in browsers is inherently broken and it allows state actors to MITM you and see all your traffic if they: 1. have ability to capture IP traffic (requires cooperation with ISP) 2. have ability to generate rogue certificate via cooperation with CA
1. Major browsers (Chrome, Safari, Edge) only accept certificates which are published in Certificate Transparency logs.
2. If a CA is discovered to have issued MitM certificates, they are swiftly distrusted by browsers.
So it's not really viable to use the existing CA system for MitM attacks.
The eIDAS proposal would:
1. Prevent browsers from distrusting CAs which are used in MitM attacks.
2. Ban mandatory checks (such as Certificate Transparency) on certificates unless the EU agrees to them.
That creates a system that is very viable for government MitM attacks.
Thats reassuring but, not knowing much about this, I have a couple of questions:
1. Is this proactively monitored for? And how? And by whom?
2. If a major state-level CA was discovered to have issued a mitm cert, would browser vendors really take the commercial hit of removing or distrusting their root cert?
Yes, security researchers like myself are constantly looking in CT logs for suspicious certificates, and I've found many, most notably Symantec issuing certs for example.com (https://groups.google.com/g/mozilla.dev.security.policy/c/fy...) and Certinomis issuing for test.com (https://bugzilla.mozilla.org/show_bug.cgi?id=1496088). Both CAs were eventually distrusted. (But Certinomis will be back once eIDAS is adopted!)
Domain owners can use Certificate Transparency Monitors to learn about suspicious certificates for their own domains. Here are some monitors:
https://crt.sh/ - allows you to search for certificates for a domain
https://github.com/SSLMate/certspotter/ - open source tool which notifies you when a certificate is issued for one of your domains
https://sslmate.com/certspotter/ - commercial service that does the same, operated by my company
> 2. If a major state-level CA was discovered to have issued a mitm cert, would browser vendors really take the commercial hit of removing or distrusting their root cert?
In 2017, Chrome and Firefox distrusted Symantec, which was at the time the world's largest certificate authority: https://security.googleblog.com/2017/09/chromes-plan-to-dist...
Symantec hadn't even issued MitM certs - they were just grossly incompetent. Distrusting them was very painful, but necessary to uphold the integrity of the CA system, and demonstrated conclusively that there is no such thing as a too-big-to-fail CA.