@roshni, which ocp3 version it failed? or it failed from ocp3.7 to ocp3.11?

From browser logs we see the browser received a 403 from backend, then looks like UI had a bug in decoding the error.

Assuming something related to configuration of oauthclient on OCP 3 side.

Note the configuration of CORS is only need on the host of the controller/ui, for this case that is only OCP 3 side.
So the configuration of CORS on OCP 4 is not needed for this scenario.

We have confirmed being able to test OCP 3.10 to 3.11 migrations via WebUI.

(In reply to Roshni from comment #0)
> Description of problem:
> Login Failure and Alert error when trying to access migration UI - migration
> controller configured on OCP 3.
> 
> Version-Release number of selected component (if applicable):
> https://quay.io/repository/ocpmigrate/mig-ui/manifest/sha256:
> d73f9b418c8571cf6063b420f88e87624425b33e89126b5a18235663ae5cc7de
> https://quay.io/repository/ocpmigrate/mig-operator/manifest/sha256:
> 1df62f5ce345f56520a8d0b9795fa9bc55fcac9c04a029f6ddf4da638b055a32
> 
> 
> How reproducible:
> 
> 
> Steps to Reproduce:
> 1. Create OCP 3.11 and OCP 4.2 clusters.
> 2. CLone https://github.com/fusor/mig-operator on OCP 3 cluster and edit
> controller.yml as follows
> # cat mig-operator/controller.yml 
> apiVersion: migration.openshift.io/v1alpha1
> kind: MigrationController
> metadata:
>   name: migration-controller
>   namespace: mig
> spec:
>   cluster_name: host
>   migration_velero: true
>   migration_controller: true
>   migration_ui: true
>   #To install the controller on Openshift 3 you will need to configure the
> API endpoint:
>   mig_ui_cluster_api_endpoint: https://<ocp3-hostname>:8443/api
Looks like the issue was the api at the end of the url is not required. Also https://github.com/fusor/mig-operator/pull/90 to fix the sample endpoint in controller-3.yaml

> 3. oc create -f operator.yml
> 4. oc create -f controller.yaml
> 5. corsAllowedOrigins:
> - //<output-of-oc get -n mig route/migration -o go-template='{{ .spec.host
> }}{{ println }}'-on-OCP3>
> 6. master-restart api
> 7. Create an stateless nginx app to migrate.
> 
> On OCP 4 do the following steps:
> 1. CLone https://github.com/fusor/mig-operator on OCP 4 cluster and edit
> controller.yml as follows
> # cat mig-operator/controller.yml 
> apiVersion: migration.openshift.io/v1alpha1
> kind: MigrationController
> metadata:
>   name: migration-controller
>   namespace: mig
> spec:
>   cluster_name: host
>   migration_velero: true
>   migration_controller: false
>   migration_ui: false
>   #To install the controller on Openshift 3 you will need to configure the
> API endpoint:
>   mig_ui_cluster_api_endpoint: https://<ocp3-hostname>:8443/api
> 
> 2. oc edit authentication.operator cluster and ensure the following exist:
> 
> spec:
>   unsupportedConfigOverrides:
>     corsAllowedOrigins:
>     - //localhost(:|$)
>     - //127.0.0.1(:|$)
>     - //<output-of-oc get -n mig route/migration -o go-template='{{
> .spec.host }}{{ println }}'-on-OCP3>
> 
> 3. oc edit kubeapiserver.operator cluster and ensure the following exist:
> 
> spec:
>   unsupportedConfigOverrides:
>     corsAllowedOrigins:
>     - //<output-of-oc get -n mig route/migration -o go-template='{{
> .spec.host }}{{ println }}'-on-OCP3>
> 
> 4. oc create -f operator.yml
> 5. oc create -f controller.yml
> 
> Try to access the Migration Web UI
> https://<output-of-oc get -n mig route/migration -o go-template='{{
> .spec.host }}{{ println }}'-on-OCP3>
> 
> Actual results:
> Web UI is not accessible
> 
> Expected results:
> Web UI should be accessible
> 
> Additional info:
> Error on the browser
> 
> action LOGIN_FAILURE @ 09:28:25.190
> app.bundle.js:262  prev state {router: {…}, auth: {…}, common: {…}, cluster:
> {…}, storage: {…}, …}
> app.bundle.js:262  action     {type: "LOGIN_FAILURE"}
> app.bundle.js:262  next state {router: {…}, auth: {…}, common: {…}, cluster:
> {…}, storage: {…}, …}
> app.bundle.js:262  action ALERT_ERROR_TIMEOUT @ 09:28:25.223
> app.bundle.js:262  prev state {router: {…}, auth: {…}, common: {…}, cluster:
> {…}, storage: {…}, …}
> app.bundle.js:262  action     {type: "ALERT_ERROR_TIMEOUT", params: Error:
> Request failed with status code 403
>     at e.exports (https://migration-mig.apps.0807-ydp.qe.…}
> app.bundle.js:262  next state {router: {…}, auth: {…}, common: {…}, cluster:
> {…}, storage: {…}, …}
> app.bundle.js:262  action ALERT_ERROR @ 09:28:25.223
> app.bundle.js:262  prev state {router: {…}, auth: {…}, common: {…}, cluster:
> {…}, storage: {…}, …}
> app.bundle.js:262  action     {type: "ALERT_ERROR", text: Error: Request
> failed with status code 403
>     at e.exports (https://migration-mig.apps.0807-ydp.qe.…,
> @@redux-saga/SAGA_ACTION: true}
> app.bundle.js:262  error      TypeError: t.text.trim is not a function
>     at Object.ALERT_ERROR (app.bundle.js:262)
>     at t.default (app.bundle.js:262)
>     at app.bundle.js:12
>     at app.bundle.js:262
>     at g (app.bundle.js:12)
>     at app.bundle.js:18
>     at app.bundle.js:262
>     at app.bundle.js:262
>     at app.bundle.js:262
>     at dispatch (app.bundle.js:12)

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, 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/RHBA-2019:2922