Go will reject certificate chains containing eight distrusted SPKIs

112 pointsposted 9 hours ago
by mendym
(github.com)

50 Comments

agwa

6 hours ago

https://gist.github.com/AGWA/5a78186e0f4a7d537b8891a7b46f945... is the list of certificates in Certificate Transparency issued by the blocked CAs as of this time. They appear to be non-malicious test certificates, and the DNS name in the first certificate indicates who likely discovered the issue.

What's alarming and unprecedented is that yesterday, two Certificate Transparency log implementations were updated to block the logging of certificates issued by the CAs. This likely indicates total private key compromise, and the blocking by CT logs is to prevent the logs from being spammed by forged certificates. However, it also means there will be no place to record forged certificates found in the wild. (These certificates won't validate in CT-enforcing clients since they won't be in CT logs, but could be used to attack non-CT-enforcing clients.)

FiloSottile

4 hours ago

I did not discover the issue. I just wished to have a rapid and definitive way to test the patch(es).

amluto

3 hours ago

Am I off base, or should I be surprised that you were able to get the mentioned cert issued in the first place this recently (yesterday)? It seems unexpected that certificates are being actively issued and logged coming from a to-be-forcibly-distrusted part of the hierarchy.

The bugzilla issues mentioned elsewhere suggest at least a mostly orderly removal of trust with issuance stopped several months ago. Your new cert was issued by “CN=EM DV TLS CA - G3B,O=eMudhra BV,C=NL”, which presumably chains to the G3 root, and the bugzilla issue seems to say that G3 was going to be dropped from the root lists some time ago but that maybe it would be cross-signed by something still trusted. So I assume that something else is going on.

Was that cert issued via normal means (e.g. ACME)?

rollulus

4 hours ago

I think that the Go project is lucky to have you. Thank you for what you do!

noja

2 hours ago

What is the CT log for then, if not to log that?

agwa

2 hours ago

CT is for logging certificates from trusted CAs. Logging certificates from untrusted CAs is out of scope, and can be harmful as untrusted certificates could be used to spam the log until it's unavailable.

Of course, the notion of "trusted" is complicated. These CAs are no longer trusted by up-to-date clients, but out-of-date clients may continue to trust them. The needs of up-to-date clients take priority over the needs of out-of-date clients.

ericbarrett

9 hours ago

A bit more info (and some discussion linked from these Bugzilla reports):

https://bugzilla.mozilla.org/show_bug.cgi?id=2083709

https://bugzilla.mozilla.org/show_bug.cgi?id=2018979

tveita

2 hours ago

Those tickets sound fairly non-dramatic - a trusted root certificate was dual-use, in breach of root certificate policy, and have committed to transition to TLS-only certificates and remove trust in the old ones.

But the Go issue is market urgent, and assigns it a CVE, so clearly there's more to it than that.

wnoise

8 hours ago

It is a shame that you cannot have a cert signed by multiple CAs.

(The format seems like it would allow it, but nothing supports it, and in practice CAs demand the ability to actually modify some fields, and then sign that.)

crote

8 hours ago

It is done with intermediate certs, though! It's a common method of establishing trust in new root certs: sign the intermediate with an already-trusted root cert, then wait for the community to adopt the new root cert over the years.

For example, the initial Let's Encrypt Authority X3 was signed by both their own (new, not-yet-universally-trusted) ISRG Root X1, and the universally-trusted third-party IdenTrust DST Root CA X3.

One crucial detail is that it isn't the same certificate. Rather, it is two separate certificates which just so happen to be using the same key pair, so the leaf cert is in essence signed by both intermediate certs at once.

I wonder if it would be possible to do the same thing on your own, actually: can a server present two completely separate cert chains to a connecting client - as long as the leaves use the same key pair? Technically AFAIK the only requirements should be 1) the key pair in use for the connection matches the cert, 2) the domain matches the cert's Subject, and 3) the cert is trusted, so at first glance it might be possible...

happosai

12 minutes ago

If the client uses "certificate_authorities" extension to list support CA's, a TLD server that holds multiple x509 certificates can present to the client the certificate signed by the clients trusted CA.

Of course, the browsers don't use the "certificate_authorities" because the list would be hilariously large for a TLS CLient Hello packet.

GoblinSlayer

4 hours ago

AFAIK, that's what google does: it sends a second post-quantum chain in addition to ecc chain.

wnoise

8 hours ago

That's an interesting wrinkle I was not aware of.

cpach

7 hours ago

Would it really be worth the extra complexity?

Another option: Use ACME together with ARI (RFC 9773). The client checks ARI data every hour. If the cert needs to be replaced – for example like in this scenario – the CA will inform the client, which in turn would then request a new cert.

I know it’s not convenient to automate for every kind of device though. I guess in some of those cases it might be better to have a load balancer in front of the device. Or use an alternative PKI.

hannob

4 hours ago

Every time there is a CA issue, someone comes up with "this would be so much better if we'd make it more complex than it already is, as it would make it a bit more convenient to deal with the most recent issue".

I don't think that's the right way to think about it.

lmz

8 hours ago

X.509v3 just has one issuer Name in the certificate, unless you're talking about something else?

wnoise

8 hours ago

Yeah, that's one of the complications. It would have to be ignored in processing, or multiple variants be presented at once (preferred).

Certificates are not the same as the public key; multiple certs sharing the same key is essentially the way around this. It's not as elegant as identical signing of the same cert, but it could work.

crote

7 hours ago

Identical signing of the same cert also runs into issues like "who gets to decide the serial number" and "how to deal with revocation lists: all of, or any of?".

And turning fields like issuer and serial into arrays risks someone accidentally using index 0 for one field and index 1 for another.

Combine that with the insane back-and-forth nightmare that the issuance process would turn into, and I have a very hard time seeing the benefit in it. After all, nobody is stopping you from requesting multiple certs independently, watching the revocation logs, and switching to the backup when required.

Puts

5 hours ago

I think certificates should be like badges that you can collect – the more badges the higher the trust. So if you are a French company, maybe the tax office in France can sign your certificate to show that you indeed is a real company. If you are accepting card payments – Visa and Mastercard could sign your certificate. If you have a domain the TLD owner could sign your certificate to show that it's indeed your domain… And so on…

And then the browser could present these badges in a nice way to the user.

calgoo

4 hours ago

I just worry that this would just bring us back to the: "Pay $$$$$$ for a certificate, those pesky lets encrypt free certs are not expensive enough to give trust", BS that always happens.

LoganDark

5 hours ago

Imagining those little "Intel Inside" "AMD Athlon" "Windows Vista" style stickers all over my browser address bar

And then you have that one website trying to collect them all.

accountrequired

7 hours ago

"Sir, this is a Wendy's" moment where my compiler thought it was a root certificate authority

xtajv

6 minutes ago

Yeah, this is making me real glad that I know C well enough to stop being afraid of it.

Pinning certificates in a browser was a brilliant idea for Chrome because web browsers are not made for technical users.

But pinning certificates in a compiler? It's reminding me of that one time where the NSA handed out DES constants to use and said "just trust me, bro". I don't even care that the DES constants ultimately ended up being protections against differential-cryptanalysis SCA (which, btw, the NSA then undermined by arguing for shorter keylengths in "export-grade crypto").

Get off my lawn.

TheDong

7 hours ago

I mean, they're the TLS certs are baked into the stdlib 'tls' package, not the compiler itself.

It's just an unfortunate unforced error that the go TLS package is bundled along with the compiler, in the same way Safari being bundled with iOS updates is an unforced error meaning a safari security bug requires a full OS update.

rollulus

5 hours ago

There are no certs baked into Go’s stdlib. This is about pkg x509 blacklisting certain certs that get loaded from elsewhere.

TheDong

3 hours ago

Oh, wow, that makes it even sillier. If I want to delete certs from my system certificate store, I can do that, the stdlib should not be making that choice if it's not even packaging the things.

agwa

2 hours ago

These are intermediate certificates, and the system certificate store on Linux provides no way to tell verifiers such as Go's crypto/x509 that an intermediate is revoked. So Go really has no other option here.

xtajv

22 minutes ago

"There's no off-the-shelf option" is not a good reason to trash a preexisting component.

Build another one.

mschuster91

8 minutes ago

Why the hell does Go ship its own root CA list? This is a task for the operating system, and at the very least Windows, macOS and most flavors of Linux ship an OS-wide truststore. It's annoying enough with Java to keep stuff updated...

q3k

15 minutes ago

$ curl https://q3k.google.com --resolve 'q3k.google.com:443:135.181.235.221' --cacert ~/emudhra/roottlscag3.pem

Yeah okay this is funny. Nice little CTF challenge :).

direwolf20

23 minutes ago

So even if your OS trusts these certs, programs written in Go won't. This is extremely unusual and makes me think someone got a National Security Letter.

jeffbee

8 hours ago

It's interesting that this sort of policy is baked into a language platform.

Aissen

2 hours ago

It's basically an additional policy on top your OS's policy, while waiting for the stores to update, it protects the users.

direwolf20

21 minutes ago

Or allows Google to override security. They could also trust a certificate here, maybe one owned by the regime.

Jarred

3 hours ago

If you don't bundle certificates, users will report that your builtin https client doesn't work in production (usually in docker)

stephbook

8 hours ago

Indeed. But the Java keystore and the Firefox/Chrome/VSCode NSSDB and whatever Python is shipping this week aren't really better.

I wonder what's so annoying about OS certs.

quiet35

4 hours ago

I really appreciate Firefox to have their own certificate DB because it allows to create separate profiles with different trusted certificate sets. The country where I live issued it's own root certificates which I have reasons not to trust in all cases but when accessing government services etc. So I've created a separate Firefox profile where I've installed those malicious certificates, keeping the main Firefox profile clean.

fc417fc802

3 hours ago

It's nice that firefox implemented that but it's the wrong place to do it IMO. It's the sort of thing that should be built into the OS along with fine grained permissions and sandboxing. The browser is merely providing a bandaid over a deficiency.

whatevaa

7 hours ago

It's mostly historical. They used to suck in the past, but the implementations remain. Nowadays you are better off configuring to use OS certificates if possible.

fractorial

8 hours ago

What about it makes it so interesting?

jeffbee

7 hours ago

Clearly the platform isn't designed to do this. Nobody thought this was going to be a necessary facility. They have just crammed an array of numbers as literal values deep into the standard library. So clearly this is an exceptional event, and not the exercise of a feature that was foreseen.

zx8080

5 hours ago

One of those "temporary workarounds" that live forever once added?

fractorial

7 hours ago

Ah, yes that seems to be what URGENT track self-documents as.

xtajv

26 minutes ago

"interesting" in the same way that folks in the south say "Bless your heart".

zx8080

5 hours ago

It's probably about power. Certs control is getting higher value, so control over this policy means more negotiation power with whatever states (governments) need from platforms.

It's easy to imagine something like: "give us some grant taxpayers money and we'll add your cert to our trusted list/remove theirs cert/disable cert when run on this hardware/etc."