Bug 1965929

Summary: kube-apiserver should use cert auth when reaching out to the oauth-apiserver with a TokenReview request
Product: OpenShift Container Platform Reporter: Standa Laznicka <slaznick>
Component: apiserver-authAssignee: Standa Laznicka <slaznick>
Status: CLOSED ERRATA QA Contact: liyao
Severity: urgent Docs Contact:
Priority: urgent    
Version: 4.8CC: aos-bugs, mfojtik, sttts, surbania, xxia
Target Milestone: ---   
Target Release: 4.8.0   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: No Doc Update
Doc Text:
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Clone Of: Environment:
Last Closed: 2021-07-27 23:10:35 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Standa Laznicka 2021-05-31 07:35:14 UTC 
Description of problem:
We are now using the WebhookTokenAuthenticator auth stack for OpenShift authentication which means the kube-apiserver is reaching to the oauth-apiserver's TokenReview endpoint.

To avoid additional request from the oauth-apiserver to the kube-apiserver to validate the SA token, use client cert authenticaion.

Version-Release number of selected component (if applicable):
4.8

How reproducible:
100%
Comment 2 Standa Laznicka 2021-06-07 14:33:44 UTC 
needs one more slight improvement from lib-go
Comment 4 liyao 2021-06-11 14:20:13 UTC 
Tested in cluster 4.8.0-0.nightly-2021-06-10-071057

1. check secret/webhook-authentication-integrated-oauth content is presented with cert/key form
$ oc extract secret/webhook-authentication-integrated-oauth -n openshift-config

2. save cert and key
echo 'client-certificate-data value' | base64 -d > cert
echo 'client-key-data value' | base64 -d > key

3. In terminal A:

cat > tokenreview_invalid.json << EOF
{"kind":"TokenReview","apiVersion":"authentication.k8s.io/v1","spec":{"token":"aaaaaaaaaaaa"}}
EOF
oc login -u testuser-41 -p <password>
TOKEN=`oc whoami -t`
cat > tokenreview_valid.json << EOF
{"kind":"TokenReview","apiVersion":"authentication.k8s.io/v1","spec":{"token":"$TOKEN"}}
EOF

4.In terminal B:

VALIDATION_POD=`oc get pod -n openshift-oauth-apiserver --no-headers | awk '{print $1}' | head -n 1` 
oc port-forward -n openshift-oauth-apiserver $VALIDATION_POD 8443:8443

5.In terminal A again, using the cert and key file saved in step2

curl -ksS -XPOST --cert ./cert --key ./key -H "Content-Type: application/json" https://localhost:8443/apis/oauth.openshift.io/v1/tokenreviews/ -d @tokenreview_valid.json
...
  "status": {
    "authenticated": true,

check and find above .status.authenticated is true, which is the expected value.
Comment 7 errata-xmlrpc 2021-07-27 23:10:35 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: OpenShift Container Platform 4.8.2 bug fix and security update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2021:2438