I recall that subdomains are their own record inside a DNS, which would imply that anyone can claim that their server is a non-existent subdomain of the real domain

  • Nougat@fedia.io
    145·
    6 days ago

    And when you are requesting a certificate for foobar.bank.com, your certificate request must come from an authorized email address at bank.com. That is also where your issued certificate would be sent. So, in order to get a certificate from a third party issuer, you have to:

    • Control the domain registration at the level just above the TLD (I don’t know how it works for co.uk, probably similar though)
    • Have access to a mailbox at the domain, where that mailbox has an address which is authorized to request certificates (this would be configured in the domain registration)

    Could a malicious actor compromise that mailbox in a way that allows them to request a certificate and then receive it? It’s not impossible, but it would be a huge effort with a small payout. Honestly, if you’ve got access to that mailbox, you don’t want to give yourself away by making false certreqs through it. You want to just exfiltrate as much data from it as you can. There’s certainly something way more valuable in there.

    • MartianSands@sh.itjust.works
      16·
      6 days ago

      your certificate request must come from an authorized email address at bank.com

      That isn’t true in general. In fact, it can’t be.

      It might be policy for most cases from the well-known certificate authorities, but it’s not part of the protocol or anything like that.

      If it were, then it would be impossible to set up your mailserver to begin with because you could never get a certificate for mail.bank.com

      • Ghoelian@lemmy.dbzer0.com
        8·
        6 days ago

        Yeah, letsencrypt doesn’t do this for example. They do ask for an email address, but that’s just for expiry notices.

        They do require you control the domain, and run it on the server the DNS record points to. When using certbot at least.

          • chameleon@fedia.io
            2·
            6 days ago

            The email ecosystem is changing in recent years but yeah, it’s best to expect that there is at least one opportunity for any given email to be sent over the internet unencrypted. MTA-STS has been slowly changing the landscape but adoption isn’t going all that great.