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Comment by hedora | Hacker News Reader

People drastically overestimate the security properties of TLS.

The correct mental model is that it’s good enough to convince 1990’s US internet users to type their credit card into a web page. (Where the downside of a breach is that you have to dispute some charges and change your CC#.)

If you need stronger security than that, then many, many caveats start to apply.

For instance, by default, anyone that can reliably man-in-the-middle port 80 on your website can get an acme certificate for your domain from a reputable certificate authority.

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If by “people,” you mean “people who rely on HTTPS for security,” then it seems like you’re saying that every hosted software company is getting it wrong. HTTPS is the foundation of the “zero trust” security model as implemented by Google, MS365, Facebook, AWS, etc.

I think it’s more likely you are not considering the full picture of the TLS ecosystem, or are making arbitrary distinctions like “cert transparency logging isn’t actually part of HTTPS” or something.

Consider that Symantec basically did what you suggest (mis-issue some certs) and not only was it detected and mitigated, they lost their CA business entirely over it.

>For instance, by default, anyone that can reliably man-in-the-middle port 80 on your website can get an acme certificate for your domain from a reputable certificate authority.

You are leaving out a huge caveat here - exactly where the MITM is taking place matters a lot. In 99% cases this isn't possible unless the victim server network is effectively compromised.

Is there more on this mitm cert spoofing somewhere I can read up on? Sounds intriguing to say the least

It probably isn't too different from other access methods: 1) Get access to port 80 for > 60 seconds. Point it at your temporary VM. 2) Use any cert authority, and for verification, choose a file-specific location verification (you can choose amongst DNS records, an email to admin@domain, or a specific file location on your site with many of them) 3) On your VM, Quickly paste the file-specific location into a django GET route. 4) Run the Django site on port 80. 5) The cert authority verifies you, and emails your account the cert, the website author being none the wiser. You can now use it later to fool future visitors for a deeper attack or email-related attacks.

This doesn't work unless the attacker happens to be in between your servers and the cert authority. The ISP that's in-between your laptop and the site can't pull this trick.

Also LE actually knows this attack is possible and mitigates it by validating the challenge from multiple sources so the attacker would need to be in the middle of all the LE validators and your servers.

https://portswigger.net/daily-swig/lets-encrypt-deploys-new-...

Yes that's true, but I was just talking about the scenario of having access to port 80 of a server DNS pointed at by some domain.

You might have access through editing a proxy rewrite rule, for example.

In the attack above you use your own SSL provider for a cert (LE not involved) and you overwrite the cert in a sense that existed before. You choose a provider that just validates with a file location. It's an attack which already requires compromise.

> The cert authority verifies you, and emails your account the cert, the website author being none the wiser.

It’s not hard to monitor cert transparency logs, which will show this new cert.

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