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it seems like all this infrastructure could be replaced by a DNS TXT record with a public key that browsers could use to check the cert sent from the web server

by donpdonp 10mo ago

it seems like all this infrastructure could be replaced by a DNS TXT record with a public key that browsers could use to check the cert sent from the web server. A web server would load a self-signed cert (or whatever cert they wanted), and put the cert's public key into a DNS record for that hostname. Every visit to a website would need two lookups, one for address and one for key. It puts control back into the hands of the domain owners and eliminates the need for letsencrypt.

akovaski 10mo ago
I'm not sure what that would solve. You would still need some central entity to sign the DNS TXT record, to ensure that the HTTPS client does not use a tampered DNS TXT record.
- tzs 10mo ago
  If someone can tamper with your DNS TXT records now they can get a certificate for your domain.
  - franga2000 10mo ago
    Not tamper with the record directly, but MitM it on the way to a target.
    - crote 10mo ago
      That's what DNSSEC is for.
      - franga2000 10mo ago
        Yes, but that's just PKI again, which is what the OP was trying to avoid.
    - ishouldbework 10mo ago
      That should be prevented by dnssec no?
      - tptacek 10mo ago
        Depends on who your adversary is. If it's your ISP: no, DNSSEC doesn't prevent that (in every mainstream deployment scenario, your upstream DNS recursive server is the only thing really doing DNSSEC validation).
  - arp242 10mo ago
    That's already the case with dns-01 verification, no? Besides, if someone has access to your TXT records then chances are they can also change A records, and you've lost already.
pennomi 10mo ago
Ah but then how would nations spy on people by compromising the root certificate?
- pgporada 10mo ago
  You're insinuating that the Let's Encrypt roots are compromised? https://letsencrypt.org/repository/#isrg-legal-transparency-reports https://letsencrypt.org/repository/#isrg-legal-transparency-...
  - pennomi 10mo ago
    No, but it’s a well-established fact that some CAs are run by governments, some of which are publicly trusted by browsers.
    - tptacek 10mo ago
      The mainstream root stores all require Certificate Transparency now.
ryangibb 10mo ago
E.g. DNS-Based Authentication of Named Entities? https://www.rfc-editor.org/rfc/rfc6698 https://www.rfc-editor.org/rfc/rfc6698 There's a TLSA resource record for certificates instead of a TXT encoding. As far as I know no major browser supports it, and adoption is hindered by DNSSEC adoption.

akovaski 10mo ago

I'm not sure what that would solve. You would still need some central entity to sign the DNS TXT record, to ensure that the HTTPS client does not use a tampered DNS TXT record.

tzs 10mo ago
If someone can tamper with your DNS TXT records now they can get a certificate for your domain.
- franga2000 10mo ago
  Not tamper with the record directly, but MitM it on the way to a target.
  - crote 10mo ago
    That's what DNSSEC is for.
    - franga2000 10mo ago
      Yes, but that's just PKI again, which is what the OP was trying to avoid.
  - ishouldbework 10mo ago
    That should be prevented by dnssec no?
    - tptacek 10mo ago
      Depends on who your adversary is. If it's your ISP: no, DNSSEC doesn't prevent that (in every mainstream deployment scenario, your upstream DNS recursive server is the only thing really doing DNSSEC validation).
- arp242 10mo ago
  That's already the case with dns-01 verification, no? Besides, if someone has access to your TXT records then chances are they can also change A records, and you've lost already.

pennomi 10mo ago

Ah but then how would nations spy on people by compromising the root certificate?

pgporada 10mo ago
You're insinuating that the Let's Encrypt roots are compromised? https://letsencrypt.org/repository/#isrg-legal-transparency-reports https://letsencrypt.org/repository/#isrg-legal-transparency-...
- pennomi 10mo ago
  No, but it’s a well-established fact that some CAs are run by governments, some of which are publicly trusted by browsers.
  - tptacek 10mo ago
    The mainstream root stores all require Certificate Transparency now.

ryangibb 10mo ago

E.g. DNS-Based Authentication of Named Entities? https://www.rfc-editor.org/rfc/rfc6698 https://www.rfc-editor.org/rfc/rfc6698 There's a TLSA resource record for certificates instead of a TXT encoding. As far as I know no major browser supports it, and adoption is hindered by DNSSEC adoption.