Mitigating the Hetzner/Linode XMPP.ru MitM interception incident

Post by lathiat » Sat, Oct 21, 2023, 9:05 AM UTC

tetromino_ wrote: post #40

simpaticoder wrote: post #39

Earlier quoted context omitted.

>The attacker managed to issue multiple SSL/TLS certificates via Let’s Encrypt This implies that the attacker was able to validate domain ownership of jabber.ru and xmpp.ru by either a) being able to respond to the ACME protocol on domain(s) hosted http OR b) being able to write to a DNS TXT file for the domain(s). This implies that the victim already lost control of their process server and/or their nameserver.

No. Most probably it merely implies someone upstream of them (presumably their hosting provider under compulsion from German law enforcement) intercepted and spoofed their unencrypted, unauthenticated ACME HTTP traffic. Same can happen to you.

Post by ThePowerOfFuet » Sat, Oct 21, 2023, 9:14 AM UTC

OmarAssadi wrote: post #48

whalesalad wrote: post #3

Earlier quoted context omitted.

extremely difficult to get physical access in a datacenter

Assuming this was done at the government's request, I assume Hetzner is more than willing to comply with a court order mandating they allow them to monitor and physically size a machine. And outside of nation-state requests, even ignoring the fact that someone could probably pay-off an employee, I think ease would depend a lot on the datacenter and target; judging by the awesome and hilarious story behind the Fremont…

Post by rhn_mk1 » Sat, Oct 21, 2023, 9:37 AM UTC

MattJ100 wrote: post #87

knorker wrote: post #82

Earlier quoted context omitted.

Pinnig is based on the keypair, not the cert. You can renew and not break pinning, right? Also you can phase in a new cert with pinning.

Yes, you can pin the public key instead, which is generally more helpful. But most ACME clients (including the "official" certbot) default to rotating the key too. That can be disabled, but it's a problematic default for this use case which means clients can't just enable pinning.

Post by natebc » Sat, Oct 21, 2023, 9:48 AM UTC

rhn_mk1 wrote: post #95

MattJ100 wrote: post #87

Earlier quoted context omitted.

Yes, you can pin the public key instead, which is generally more helpful. But most ACME clients (including the "official" certbot) default to rotating the key too. That can be disabled, but it's a problematic default for this use case which means clients can't just enable pinning.

How can it be disabled in certbot?

  --reuse-key           When renewing, use the same private key as the
                        existing certificate. (default: False)

Post by sshine » Sat, Oct 21, 2023, 10:11 AM UTC

simpaticoder wrote: post #54

tetromino_ wrote: post #40

Earlier quoted context omitted.

No. Most probably it merely implies someone upstream of them (presumably their hosting provider under compulsion from German law enforcement) intercepted and spoofed their unencrypted, unauthenticated ACME HTTP traffic. Same can happen to you.

Okay, but the part I don't understand is why do it this way? If the hosting provider is a threat, they don't need new certs. They can just read your private keys off your disk and MITM with that.