Azure Application Gateway Not allowing Client Certificates

Question

I have Azure API Management, configured internally and exposed to the public through Azure application Gateway. My API is secured for client certificates, it working perfectly when I test it internally. When I test it externally, I am getting an invalid certificate error. Does Azure Application Gateway block client certificates? How to allow them?

Answer 1

An answer from Microsoft:

We do have option for mutual authentication on Application Gateway which can allow the mutual authentication between client and Application Gateway: https://learn.microsoft.com/en-us/azure/application-gateway/mutual-authentication-overview

However this is still in preview version, which is not included in SLA. As the mutual authentication between AppGW and the APIM we double confirmed with the backend engineers, unfortunately the answer is no we do not support such a function.

Answer 2

I suspect this is not yet possible with Application Gateway: https://feedback.azure.com/forums/217313-networking/suggestions/9379902-allow-mutual-ssl-auth-on-application-gateway