4 ms·

I've never understood how a VPN doesn't get too carried away to pull a MITM with some central cert

gjsman-1000 5y ago
Because if you used a central cert, every device would have to whitelist that cert, and just clocking the lock icon in your browser would reveal it.
- jen20 5y ago
  Many consumer VPNs install a client, and it would be trivial to ship a new trusted certificate with it.
  - acdha 5y ago
    This is true, but note that, for example, on iOS an application can't do that without prompting. Now, most people would probably hit “Approve” if one of their security products said it was necessary.
  - gjsman-1000 5y ago
    That wouldn’t change that clicking the lock icon in your browser would show the same certificate on every website, and that this certificate was universally valid. Pretty obvious…
    - AdamJacobMuller 5y ago
      > show the same certificate on every website Not really, because, you can use on-demand certificate issuance. Hell, if you really want to, you can even name your certificates the same as existing certificates and the only way to detect the forgery would be to compare the actual public keys (and who does THAT). I feel like I'm writing an evil roadmap here, but, you can even do multiple root certs with different names and trust them all, do a whole "fake" PKI infrastructure which would be impossible to detect unless you were comparing the actual keys.
      - anonymouse008 5y ago
        > I feel like I'm writing an evil roadmap here, but, you can even do multiple root certs with different names and trust them all, do a whole "fake" PKI infrastructure which would be impossible to detect unless you were comparing the actual keys. Yeah, just imagine being beholden to some federal statue impropriety (easiest in taxes) and running one of the these vpn organizations...
      - 0x0 5y ago
        If and when browsers start requiring pre-certificate transparency logging, anything like this should no longer be possible to pull off, since none of the fake certificates would be able to contain a stapled pre-certificate "signoff" from a trusted CT log.
  - throw0101a 5y ago
    > Many consumer VPNs install a client, and it would be trivial to ship a new trusted certificate with it. A lot of browsers have their own root chain, and also now do certificate pinning, so will (IIRC) only accept specifically designated certs for particular sites (doesn't Google/Chrome/Gmail do this?).
- Nextgrid 5y ago
  On the other hand, a lot of VPNs provide proprietary client software (even though all the major OSes have built-in support for the common VPN protocols such as IPSec, L2TP, etc) so they could very well sneak the root cert in there too.

Because if you used a central cert, every device would have to whitelist that cert, and just clocking the lock icon in your browser would reveal it.

jen20 5y ago
Many consumer VPNs install a client, and it would be trivial to ship a new trusted certificate with it.
- acdha 5y ago
  This is true, but note that, for example, on iOS an application can't do that without prompting. Now, most people would probably hit “Approve” if one of their security products said it was necessary.
- gjsman-1000 5y ago
  That wouldn’t change that clicking the lock icon in your browser would show the same certificate on every website, and that this certificate was universally valid. Pretty obvious…
  - AdamJacobMuller 5y ago
    > show the same certificate on every website Not really, because, you can use on-demand certificate issuance. Hell, if you really want to, you can even name your certificates the same as existing certificates and the only way to detect the forgery would be to compare the actual public keys (and who does THAT). I feel like I'm writing an evil roadmap here, but, you can even do multiple root certs with different names and trust them all, do a whole "fake" PKI infrastructure which would be impossible to detect unless you were comparing the actual keys.
    - anonymouse008 5y ago
      > I feel like I'm writing an evil roadmap here, but, you can even do multiple root certs with different names and trust them all, do a whole "fake" PKI infrastructure which would be impossible to detect unless you were comparing the actual keys. Yeah, just imagine being beholden to some federal statue impropriety (easiest in taxes) and running one of the these vpn organizations...
    - 0x0 5y ago
      If and when browsers start requiring pre-certificate transparency logging, anything like this should no longer be possible to pull off, since none of the fake certificates would be able to contain a stapled pre-certificate "signoff" from a trusted CT log.
- throw0101a 5y ago
  > Many consumer VPNs install a client, and it would be trivial to ship a new trusted certificate with it. A lot of browsers have their own root chain, and also now do certificate pinning, so will (IIRC) only accept specifically designated certs for particular sites (doesn't Google/Chrome/Gmail do this?).
Nextgrid 5y ago
On the other hand, a lot of VPNs provide proprietary client software (even though all the major OSes have built-in support for the common VPN protocols such as IPSec, L2TP, etc) so they could very well sneak the root cert in there too.