5 ms·

Can someone explain what could be done with that and by whom?

tptacek 2y ago
Microsoft appears to have arranged with the government of Brazil for one of their national CAs to have the ability to mint arbitrary certificates. Only Microsoft's own WebPKI software cares; Chrome, Safari, and Firefox don't trust this CA.
77pt77 2y ago
Whoever has the private certificate can pretend to be google.com to people using windows. The brower (possibly only edge) and system would show the connection as being secure.
- deleted 2y ago
  [deleted]
woofcat 2y ago
Whomever has this fake certificate can run a server and say it's google.com and windows will say "yep you are" with the little green lock.
- bufferoverflow 2y ago
  The certificate is for a specific IP address, no? And without DNS pointing google.com to that IP address, it's pretty useless.
  - zer0x4d 2y ago
    Nope, certificates are issued for CNs(Common Name), also known as FQDNs (Fully qualified domain names). Something such as *.google.com, not IP addresses. If they were issued for IP addresses they would have to reissue the certificate every time they spun up a new server. Also it's why if you spin up another server and make DNS point google.com to that server, it would not pass verification since the certificate you will be using on that server is not issued to *.google.com, but rather some other domain you own. The IP address plays no role in certificates.
    - buzer 2y ago
      Certificates can be issued to IP addresses (at least on SAN level, not sure if they are allowed in CN in CA/B baseline requirements), like https://crt.sh/?id=15492507462 https://crt.sh/?id=15492507462
      - Arrowmaster 2y ago
        That is different in context to what was being asked though.
    - colanderman 2y ago
      Nit: a CN (stored in the Subject field of a cert) is not an FQDN, though historically web browsers treated them as such. This practice is now deprecated. Modern practice is for the domain name(s) to be placed in the Subject Alternative Name (SAN) field. The Subject field is not consulted so long as the SAN field is present, and can in theory be any X.500 Distinguished Name, of which Common Name is one possible attribute, which may be any freeform string of a limited length (though it is typically set to the primary domain the cert is issued for, for easy identification).
  - deleted 2y ago
    [deleted]
  - echoangle 2y ago
    > And without DNS pointing google.com to that IP address, it's pretty useless. On the internet itself maybe, but you can still MITM people on some network, right?
- baobabKoodaa 2y ago
  Where? In Edge you mean?
  - echoangle 2y ago
    And everything that uses the OS trust store, when run on Windows, I assume.
brianpan 2y ago
It's not entirely about this particular certificate (although this is bad, too). This is about a certificate authority giving someone who is NOT Google, a certificate that can be used to "prove" a server is Google. Accidental or not, this should not happen. The "blast radius" is limited to Microsoft since they are the only ones that trust this particular certificate authority. Your non-Microsoft browser won't trust these certs. Your non-Microsoft OS, Java program, etc. etc. won't trust these certs.
- xcrunner529 2y ago
  Chrome uses the Windows trust store on Windows, IIRC.
  - brianpan 2y ago
    I dug a little and apparently Chrome previously used the trust store of the platform but has now transitioned away from that to use their own. https://blog.chromium.org/2022/09/announcing-launch-of-chrome-root-program.html https://blog.chromium.org/2022/09/announcing-launch-of-chrom... But even before they switched to this "Chrome Root Program", they have distrusted specific CAs, for example Symantec in 2017. https://security.googleblog.com/2017/09/chromes-plan-to-distrust-symantec.html https://security.googleblog.com/2017/09/chromes-plan-to-dist...
    - xcrunner529 2y ago
      Thanks for the info! Didn’t know they moved on.

Microsoft appears to have arranged with the government of Brazil for one of their national CAs to have the ability to mint arbitrary certificates. Only Microsoft's own WebPKI software cares; Chrome, Safari, and Firefox don't trust this CA.

77pt77 2y ago

Whoever has the private certificate can pretend to be google.com to people using windows. The brower (possibly only edge) and system would show the connection as being secure.

deleted 2y ago
[deleted]

woofcat 2y ago

Whomever has this fake certificate can run a server and say it's google.com and windows will say "yep you are" with the little green lock.

bufferoverflow 2y ago
The certificate is for a specific IP address, no? And without DNS pointing google.com to that IP address, it's pretty useless.
- zer0x4d 2y ago
  Nope, certificates are issued for CNs(Common Name), also known as FQDNs (Fully qualified domain names). Something such as *.google.com, not IP addresses. If they were issued for IP addresses they would have to reissue the certificate every time they spun up a new server. Also it's why if you spin up another server and make DNS point google.com to that server, it would not pass verification since the certificate you will be using on that server is not issued to *.google.com, but rather some other domain you own. The IP address plays no role in certificates.
  - buzer 2y ago
    Certificates can be issued to IP addresses (at least on SAN level, not sure if they are allowed in CN in CA/B baseline requirements), like https://crt.sh/?id=15492507462 https://crt.sh/?id=15492507462
    - Arrowmaster 2y ago
      That is different in context to what was being asked though.
  - colanderman 2y ago
    Nit: a CN (stored in the Subject field of a cert) is not an FQDN, though historically web browsers treated them as such. This practice is now deprecated. Modern practice is for the domain name(s) to be placed in the Subject Alternative Name (SAN) field. The Subject field is not consulted so long as the SAN field is present, and can in theory be any X.500 Distinguished Name, of which Common Name is one possible attribute, which may be any freeform string of a limited length (though it is typically set to the primary domain the cert is issued for, for easy identification).
- deleted 2y ago
  [deleted]
- echoangle 2y ago
  > And without DNS pointing google.com to that IP address, it's pretty useless. On the internet itself maybe, but you can still MITM people on some network, right?
baobabKoodaa 2y ago
Where? In Edge you mean?
- echoangle 2y ago
  And everything that uses the OS trust store, when run on Windows, I assume.

brianpan 2y ago

It's not entirely about this particular certificate (although this is bad, too). This is about a certificate authority giving someone who is NOT Google, a certificate that can be used to "prove" a server is Google. Accidental or not, this should not happen. The "blast radius" is limited to Microsoft since they are the only ones that trust this particular certificate authority. Your non-Microsoft browser won't trust these certs. Your non-Microsoft OS, Java program, etc. etc. won't trust these certs.

xcrunner529 2y ago
Chrome uses the Windows trust store on Windows, IIRC.
- brianpan 2y ago
  I dug a little and apparently Chrome previously used the trust store of the platform but has now transitioned away from that to use their own. https://blog.chromium.org/2022/09/announcing-launch-of-chrome-root-program.html https://blog.chromium.org/2022/09/announcing-launch-of-chrom... But even before they switched to this "Chrome Root Program", they have distrusted specific CAs, for example Symantec in 2017. https://security.googleblog.com/2017/09/chromes-plan-to-distrust-symantec.html https://security.googleblog.com/2017/09/chromes-plan-to-dist...
  - xcrunner529 2y ago
    Thanks for the info! Didn’t know they moved on.