Azure Application Proxy - changing application basic authorization header

Shepherd, David (Technical Specialist) 96 Reputation points
2020-04-15T08:12:37.983+00:00

We have a web app that is working fine internally and then failing when going through Azure App Proxy. The app sends a basic authentication header from the client. (This can be be seen in a wireshark trace - SSL decode) correctly formatted. When you look at a log file on the web app server we can see the same basic header as purely lower case. This of course breaks base64 and the credentials are invalid. So my question is that why should Azure App Proxy change the http header to lower case ?

This does not happen for internal access of the application and the case of header is preserved.

The app is based on websockers and is configured as passthrough currently.

Microsoft Entra ID
Microsoft Entra ID
A Microsoft Entra identity service that provides identity management and access control capabilities. Replaces Azure Active Directory.
19,502 questions
0 comments
Accepted answer
  1. Shepherd, David (Technical Specialist) 96 Reputation points
    2020-07-14T13:26:44.117+00:00

    We did indeed raise a support ticket. The root cause was a code fault in Azure App Proxy and its web socket support where all headers were being normalised which broke any form of authentication.

    A Preview fix was provided from Microsoft and the issue is resolved.

1 additional answer

Sort by: Most helpful
Most helpful Newest Oldest
  1. Alfredo Revilla - Senior Freelance SWE, SWA, IAM 27,016 Reputation points
    2020-07-14T13:22:30.153+00:00

    Please raise a support request so that we can investigate this properly.

    0 comments