Azure AD Application Proxy SSL Certificate for custom domain

Owen Thompson 1 Reputation point
2021-12-06T13:57:16.357+00:00

Hi All,

I am having a strange issue with the Azure Application Proxy. I had this working before with the same server & website but I had to change the name, and now it's not working.

The error message I get while trying to visit the page is

BadGateway:
This corporate app can't be accessed.
Next Steps
One or more errors were found in the Secure Sockets Layer (SSL) certificate sent by the server.
For more details, check the Application Proxy Connector Event Log for reported errors.

I have checked the Application Proxy events and it says the SSL Cert is not trusted on the backend server. But there is a lets encrypt cert there for the internal server/website name and also I added the external URL as a SAN. I have tried obtaining certs for just the internal or external URLs but the message is the same.

Can anyone help me figure out what is going on here? Like I said it was working - when I changed the name, I also changed the SSL Cert (as mentioned), the CNAME (both external and internally). Any ideas? I spent nearly 1 hour on the phone with MS Support (or Mindtree Ltd to be precise) but we could not figure out what was wrong.

Many Thanks!

Microsoft Security | Microsoft Entra | Microsoft Entra ID
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2 answers

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  1. Ahmed Lotfy 1 Reputation point
    2021-12-13T09:33:25.833+00:00

    Hi Owen ,
    i totally understand , okay please do the follwoing and feedback :

    1- configure the internal url to be the same as external url .
    2- make sure you've uploaded the Public certificate that contains the name of the external url to the application proxy.
    3- create a record in the hosts file of the backend server --- > let's say it's app.abc.com points to the internal IP of your backend server.

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  2. Ahmed Lotfy 1 Reputation point
    2021-12-13T15:24:13.487+00:00

    Hello Owen , Did it Work ?

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