Add certificate watcher to queue-proxy #14189

ReToCode · 2023-07-26T06:35:49Z

Proposed Changes

Use projected volumes to mount certificate secret in queue-proxy to get updates when secret changes
Adds a certificate watcher to queue-proxy to reload certificates when they change on the file system

Release Note

When `internal-encryption` is enabled, queue-proxy mounts the certificate secret as projected-volume and automatically reloads the certificates on change.

ReToCode · 2023-07-26T06:37:49Z

@dprotaso , @skonto , @nak3 , @KauzClay
Before I add unit-tests and e2e-tests, what do you think about the approach? Problem description see: #14187.

Also is there anything to keep in mind/check when adding new dependencies?

nak3 · 2023-07-26T08:19:10Z

Use projected volumes to mount certificate secret in queue-proxy to get updates when secret changes

inotify on k8s is a little bit tricky kubernetes/kubernetes#112677 - but it would work well? I guess using projected volumes could solve it? (Honsetly, I didn't know why it changed to use projected volume so I am guessing it.)

Also is there anything to keep in mind/check when adding new dependencies?

We want to make QP small as much as possible #9957. But the deps is enough small that we can ignore, isn't it? As far as I built the image, it seems OK.
Also, we would like to make sure memory/CPU consumption is not increased by the inotify watcher. (Sorry I haven't confirmed it on my side 😅 )

ReToCode · 2023-07-26T08:59:44Z

inotify on k8s is a little bit tricky kubernetes/kubernetes#112677 - but it would work well? I guess using projected volumes could solve it? (Honsetly, I didn't know why it changed to use projected volume so I am guessing it.)

Good points, thank you. Yes I had the same issue with normal secrets, but projected volumes seem to work fine. But I'll probably do some more testing with it.

Seems like thanos went with an approach to continuously re-read the file (thanos-io/thanos#6503) and see if there are differences. That could also work fine, but could take some more time for the certificate to be updated, so we somehow would still would need to trust multiple root CAs for some time in activator and all ingress-controllers to make it work properly - or implement proper cross signing ourselves.

I still feel like that we are rebuilding too much stuff ourselves instead of leveraging functionality of a Service Mesh or directly relying on solutions like cert-manager.

In the end we probably will end up with some limitations and known issues with our custom solution.

KauzClay · 2023-07-26T13:35:42Z

I think your approach makes sense, seems like the path of least resistance too.

Asking just so I can understand the scenario better: do you have context on why QP uses the mounted secrets? Is there a reason it doesn't have a trust-store like activator? Maybe that makes it too big, per @nak3 's point?

I still feel like that we are rebuilding too much stuff ourselves instead of leveraging functionality of a Service Mesh or directly relying on solutions like cert-manager.

generally I'd agree, would it be so bad if Knative had a dependency on cert-manager?

But I might not be seeing it in this case, is there a way you see cert-manager would help here? We would still need the logic to check for the change in the mounted secret, right?

pkg/queue/certificate/watcher.go

ReToCode · 2023-07-27T05:04:40Z

Is there a reason it doesn't have a trust-store like activator? Maybe that makes it too big, per @nak3 's point?

Queue-Proxy does not have access to the kube api (so no informers or watchers on secrets). Not sure what the original reasons for this are, but I also assume it is related to the size topic.

generally I'd agree, would it be so bad if Knative had a dependency on cert-manager?

I don't think so either, especially as this would only be necessary when people want to use encryption. @evankanderson had some doubts about having that.

But I might not be seeing it in this case, is there a way you see cert-manager would help here? We would still need the logic to check for the change in the mounted secret, right?

It would not help here directly. It is more about the rotation of the CA. Our current implementation just creates a new CA and immediately rotates all secrets. We probably will have to build some logic that does proper rotation. These things would already be handled with cert-manager. With this, ingresses, activator and proxies would have some time to shift to the new certs.

ReToCode · 2023-07-31T14:05:16Z

The thanos approach is fairly easy and the introduced delay should not matter as we need to make sure we allow some rotation grace period in activator & ingress controllers anyways (reloading certs across all K Services will take some time), so I'm going to continue with that approach. Will add tests and e2e tests shortly.

codecov · 2023-07-31T14:06:19Z

Codecov Report

Patch coverage: 54.65% and project coverage change: -0.14% ⚠️

Comparison is base (8ea1cb6) 86.25% compared to head (218c1bf) 86.11%.
Report is 68 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14189      +/-   ##
==========================================
- Coverage   86.25%   86.11%   -0.14%     
==========================================
  Files         199      196       -3     
  Lines       14811    14781      -30     
==========================================
- Hits        12775    12729      -46     
- Misses       1734     1746      +12     
- Partials      302      306       +4

Files Changed	Coverage Δ
pkg/queue/sharedmain/main.go	`0.83% <0.00%> (-0.04%)`	⬇️
pkg/queue/certificate/watcher.go	`69.11% <69.11%> (ø)`

... and 8 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

ReToCode · 2023-08-02T08:43:37Z

/unhold

This is ready to be reviewed. I'll add another issue for full CA rotation, as more work is needed to make that work (as activator and all net-* components also must support it).

@dprotaso , @skonto , @nak3 , @KauzClay, @davidhadas

nak3 · 2023-08-03T06:16:55Z

Use projected volumes to mount certificate secret in queue-proxy to get updates when secret changes

I thought that the projected volumes was used for the workaround of inotify. Do we still need the change to use projected volumes?

ReToCode · 2023-08-03T06:27:59Z

I thought that the projected volumes was used for the workaround of inotify. Do we still need the change to use projected volumes?

The update behaviour with projectedVolumes seems to be way more stable in my tests. Do you think there is a downside to using it this way?

ReToCode · 2023-08-04T05:11:08Z

/retest

ReToCode · 2023-08-04T05:41:56Z

The update behaviour with projectedVolumes seems to be way more stable in my tests. Do you think there is a downside to using it this way?

I checked this again, it takes a bit longer to refresh on disk, but in general we should be fine using a normal mount. I also checked Kube RBAC proxy, it does it the same way. Updated the PR accordingly.

pkg/queue/sharedmain/main.go

nak3 · 2023-08-07T01:42:17Z

pkg/queue/certificate/watcher.go

+// NewCertWatcher creates a CertWatcher and watches
+// the certificate and key files. It reloads the contents on file change.
+// Make sure to stop the CertWatcher using Stop() upon destroy.
+func NewCertWatcher(certPath, keyPath string, reloadInterval time.Duration, logger *zap.SugaredLogger) (*CertWatcher, error) {


certPath and keyPath are fixed value.
We can move the const values (certPath and keyPath) to pkg/queue/certificate or some common package and drop the arguments and field in the struct?

Hm for now CertWatcher pretty generic (and could be used somewhere else). The constants seem to be with other configuration in sharedmain which also need to correspond to the yaml, so I think I'd prefer to let them there. WDYT?

Sure, no problem. Let's keep there.

pkg/queue/certificate/watcher.go

nak3 · 2023-08-07T05:41:12Z

/lgtm
/hold

Thank you so much 🎉 /hold for other reviewers.

KauzClay · 2023-08-08T15:09:56Z

looks good to me as well!

/unhold

KauzClay · 2023-08-09T14:26:43Z

ah, I thought unholding this would let it be merged?

Seems like it needs to be approved? Idk if I have approval power

krsna-m · 2023-08-14T13:39:27Z

/approve

knative-prow · 2023-08-14T13:39:35Z

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krsna-m · 2023-08-14T13:41:34Z

/unapprove
/hold

krsna-m · 2023-08-14T13:43:19Z

/lgtm also

ReToCode · 2023-08-21T13:53:19Z

@dprotaso can this be merged? Some Approver magic is needed.

ReToCode · 2023-08-29T05:13:13Z

/assign @dprotaso

dprotaso

FYI - if you haven't noticed K8s is looking to provide a generic mechanism to distribute CAbundles

Though it's in early design phases
https://github.com/kubernetes/enhancements/tree/master/keps/sig-auth/3257-trust-anchor-sets#pemtrustanchors-projected-volume-source

pkg/queue/certificate/watcher.go

pkg/queue/sharedmain/main.go

ReToCode · 2023-08-30T07:35:44Z

FYI - if you haven't noticed K8s is looking to provide a generic mechanism to distribute CAbundles

That is nice, definitely a thing that will help us.

dprotaso · 2023-08-31T16:42:50Z

/lgtm

knative-prow bot requested review from jsanin-vmw and kauana July 26, 2023 06:35

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ReToCode mentioned this pull request Aug 3, 2023

Set TLS minimum version to 1.3 for Ingress to Activator #14074

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Add certificate watcher to queue-proxy

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stop the certWatcher using defer

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Add certificate watcher to queue-proxy #14189

Add certificate watcher to queue-proxy #14189

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Add certificate watcher to queue-proxy #14189

Add certificate watcher to queue-proxy #14189

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