Server loads incorrect certificate from Windows Certificate Store

[wooti]

Observed behavior

I start nats-server.exe with the following configuration:

tls: {
  cert_store: "WindowsLocalMachine"
  cert_match_by: "Subject"
  cert_match: "MyCertificate"
  timeout: 2
}
jetstream: enabled
host: my.local.machine

My Windows Certificate Store has multiple test certificates defined, with similar subject names. One is called MyCertificate, another MyCertificateForClient. The former is fully trusted (as it is also registered as a Trusted Root CA), and is the certificate I expect the server to load.

Expected behavior

The server loads certificate MyCertificateForClient. I am unable to connect to the server, with the following error:

nats: error: tls: failed to verify certificate: x509: certificate signed by unknown authority

Server and client version

nats-server: v2.10.22

Host environment

Windows 10, AMD64

Steps to reproduce

It looks like this is due to use of CERT_FIND_ISSUER_STR or CERT_FIND_SUBJECT_STR, more details here. The lookup is for a certificate that "contains the specified string", which both of my test certificates satisfy.

Furthermore, certificates within the store are unordered, and I also suspect that the server could retrieve expired, revoked or untrusted certificates in favour of one that can actually be used.

I found a comment with similar issue here. The follow up here makes sense to me - if I could specify a certificate by thumbprint I could guarantee that the correct certificate is loaded.

See also

https://github.com/nats-io/nats-server/issues/2130 https://github.com/nats-io/nats-architecture-and-design/blob/main/adr/ADR-39.md

[neilalexander]

Have prepared a branch that should let you specify the certificate by the SHA1 thumbprint instead:

tls: {
  cert_store: "WindowsLocalMachine"
  cert_match_by: "thumbprint"
  cert_match: "2fd4e1c67a2d28fced849ee1bb76e7391b93eb12"
  timeout: 2
}

Can you please give it a try?

https://binaries.nats.dev/binary/github.com/nats-io/nats-server/v2?os=windows&arch=amd64&version=21ad69a5

[wooti]

Can you please give it a try?

Hi @neilalexander, many thanks for having a look at this issue! Unfortunately I wasn't able to make this work with the binary provided.

nats-server: .\nats-streaming.conf:1:0: unable to find certificate in store

[wooti]

I wonder if CERT_FIND_SHA1_HASH or CERT_FIND_HASH should be used instead of CERT_FIND_HASH_STR in https://github.com/nats-io/nats-server/blob/main/server/certstore/certstore_windows.go#L63 ?

[neilalexander]

Hmm, you could be right, can you try this instead?

https://binaries.nats.dev/binary/github.com/nats-io/nats-server/v2?os=windows&arch=amd64&version=24eefd85

[wooti]

No luck I'm afraid, same error message

[neilalexander]

Ah, I see the problem. CERT_FIND_HASH_STR is indeed correct but it needs the string input, not the decoded form.

Please give this one a go — I've tested it on a Windows virtual machine:

https://binaries.nats.dev/binary/github.com/nats-io/nats-server/v2?os=windows&arch=amd64&version=7eb387a5

[wooti]

Amazing! That one is working great

[neilalexander]

Thanks for confirming, have raised PR #6047.