" Windows trusts 322 root certificates issued by 122 different organizations"
I think this is a good point I would never trust 122 people in my life with my bank-account details. But if I
trust my browser it seems that is exactly what I'm doing.
I don't think the high number of CAs is as big a risk as it sounds like.
1. To exploit this, the attacker needs to be in a man-in-the-middle position and compromise a CA
2. Certificate transparency helps with detecting and banning misbehaving CAs
3. CAs are audited to have processes in place which make it difficult for individuals to misbehave
4. In case of a large scale attack of this kind, banks are relatively likely to refund the money (unlike money stolen by a person you authorized)
5. The individuals employed by CAs are not anonymous and at risk of legal prosecution
I'd be more worried about DNS/registrar level attacks, since CAs generally assume that whoever has control over a domain is authorized to issue certificates for it. I doubt registrars are anywhere near as security conscious as CAs.
And then there is the dependency hell of random software having hundreds of indirect dependencies they didn't verify which are maintained by random, often anonymous people. On most desktop OSs any such application can steal your banking credentials.
No, to exploit this, you just need to either 1) work inside a CA, 2) be a spy and infiltrate the CA, 3) use your nation-state powers to force a CA in your borders to do what you want, or 4) be a clever hacker hack a CA. There are "only" 330 different complex organizations in probably a hundred-plus countries to try, so I guess this is pretty unlikely.
But even if it is, you can actually hack the entire system with just a BGP hack. Today, if you issue some false BGP routes, you can MITM LetsEncrypt (or one of the other 329 CAs) to sign a valid cert for you. It's not hard because validation is automated and depends on proving you own IP space... and IP space is just what your router's BGP table says it is at the moment you issue a cert.
I would not depend on the kindness of banks giving back money on very large scales. They care about themselves more than they care about you.
You're right, DNS registrar and nameserver attack is another great attack and usually they're pretty vulnerable, so that's another good option.
I see there are safeguards in place. But is it true that it is enough to compromise one CA to compromise my browser? Or would a hacker have to compromise ALL of the 322 certificates?
If the latter then having more certificates would simply mean it is more secure. If the former it would mean having more certificates makes it less secure.
Or is it something in between? Do additional certificates add to the security, or diminish from it?
It is - generally speaking - enough for the attacker to compromise one CA. Every CA can issue certificates for all domains, with some exceptions where the browser knows which CA should be issuing the certificate. Google chrome has a hardcoded list of high value targets, IIRC. All of that is ignored when you have a local CA trust root, though, like many enterprises do (for their TLS intercepting proxies)
And for those CAs, even the safeguards as certificate transparency are moot. As a consultant, I never accept to install one of those CA certs in my trust store. I’d rather go and use a VM or a dedicated machine.
There's always a better way. But when you're going up against gigantic incumbents with way more power than everyone else, you don't get the better way. You get the way the powerful decide it will work. It's like politics, or economics. When a system is so large and unwieldy, significant change can't come unless the ridiculously powerful minority forces it. If they have no reason to do so...
I think this is a good point I would never trust 122 people in my life with my bank-account details. But if I trust my browser it seems that is exactly what I'm doing.
Isn't there a better way?