An unexpected isssue in EventGrid Callback validation requests

Question

I did spend hours trying to figure out why Cloud Event Webhook validation was ok in one service and failed in other services in Azure.

I was running the exactly the same App as a App Service and Container App.

I found out that the problem was that the request header names have different casings.

WebHook-Request-Callback:

vs.

webhook-request-callback:

I wish they could atleast be consistent within Azure and EventGrid..

Here's a webhook-request-callback to an App Service

OPTIONS /hook2

CLIENT-IP: 51.12.47.159:64196

DISGUISED-HOST: as-clouddebugger-linux-container.azurewebsites.net

Host: as-clouddebugger-linux-container.azurewebsites.net

Max-Forwards: 10

WAS-DEFAULT-HOSTNAME: as-clouddebugger-linux-container.azurewebsites.net

WebHook-Request-Callback: https://rp-swedencentral.eventgrid.azure.net:553/eventsubscriptions/cloudevent-linux-container/validate?id=041F50B3-5A9F-417B-835D-1CDE58F3C6A9&t=2025-01-29T18:53:45.4115525Z&apiVersion=2024-12-15-preview&token=SZUYTGhOMExsrcg3qmStXMhsezj1TCILREWmZCQXVh4%3d

WebHook-Request-Origin: eventgrid.azure.net

X-ARR-LOG-ID: 32916421-23c7-4df7-8024-d1e0a42ea84b

X-ARR-SSL: 2048|256|CN=Microsoft Azure RSA TLS Issuing CA 08, O=Microsoft Corporation, C=US|CN=*.azurewebsites.net, O=Microsoft Corporation, L=Redmond, S=WA, C=US

X-AppService-Proto: https

X-Client-IP: 51.12.47.159

X-Client-Port: 64196

X-Forwarded-TlsVersion: 1.2

X-Original-For: [::ffff:169.254.131.1]:52719

X-Original-Proto: http

X-Original-URL: /hook2

X-SITE-DEPLOYMENT-ID: as-CloudDebugger-Linux-Container

X-WAWS-Unencoded-URL: /hook2

And here is a request to Container AppService-Proto

OPTIONS /hook2

Content-Length: 0

Host: ca-clouddebugger.orangewater-c2f516d4.swedencentral.azurecontainerapps.io

X-Original-For: [::ffff:100.100.0.180]:56784

X-Original-Proto: http

webhook-request-callback: https://rp-swedencentral.eventgrid.azure.net:553/eventsubscriptions/cloudevent-linux-container-app/validate?id=DDAD8472-2717-4624-8661-210F29029BB2&t=2025-01-29T18:57:11.1296364Z&apiVersion=2024-12-15-preview&token=%2fnvnFmnrE5MGmBCutflYlZTU1Ux9f7JakOtnRNyyYUQ%3d

webhook-request-origin: eventgrid.azure.net

x-arr-ssl: true

x-envoy-expected-rq-timeout-ms: 1800000

x-envoy-external-address: 51.12.47.151

x-k8se-app-kind: web

x-k8se-app-name: ca-clouddebugger--9bn4egg

x-k8se-app-namespace: k8se-apps

x-k8se-protocol: http1

x-ms-containerapp-name: ca-clouddebugger

x-ms-containerapp-revision-name: ca-clouddebugger--9bn4egg

x-request-id: 796c0195-690a-4aa8-95ba-705655383419