EventGrid trigger does not work with TLS 1.3

[eluchsinger]

Description

I'm not sure if this is a library issue or a platform issue.

The EventGrid trigger does not seem to work when my Azure Function is set to accept TLS 1.3 or higher. I just stopped receiving events.

After setting Minimum Inbound TLS Version to 1.2, the trigger started working again. I could reproduce this on multiple Azure Function Apps.

Steps to reproduce

1. Deploy an Azure Function with EventGrid trigger and CloudEvent parameter:
   [Function("MyFunction")] public async Task Run([EventGridTrigger] CloudEvent cloudEvent)
2. Change the Azure Function Minimum Inbound TLS Version to 1.3
3. Trigger the Azure Function.

[miszu]

We've noticed the same thing, also saw it reported on stack overflow: https://stackoverflow.com/questions/69556360/creating-azure-event-grid-webhook-subscription-fails-tls-handshake/78575138#78575138

Is the TLS 1.3 support coming or is it recommended to not use EventGrid if 1.3 is required?

[johngraumann]

We ran across this as well. I stumbled upon this blog post that seems to indicate it will be working starting March 1. Let's hope that is still the case.

https://azure.microsoft.com/en-us/updates?id=TLS-changes-for-Azure-Event-Grid

[miszu]

@johngraumann thanks for the link! We've tested it by bumping the min. TLS to 1.3 in our Azure Function, unfortunately it still doesn't work, events are not accepted. I also did not find a way of bumping TLS to 1.3 on EventGrid's side. Hopefully this is just a delay on MS side and it will start working soon.