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.NET Core 3.1 SSL offloading issue.

Mike Schrock
Mike Schrock used Ask the Experts™
Hello Experts!
I have gotten an issue dumped in my lap. I am a SysAdmin by trade and enjoy my craft, not developing and here is just why:

We offload our SSL to a HA pair of Load Balancer. That works fine. Traffic comes in HTTPS, gets converted to HTTP and ships it along to the server (Server 2012 R2).
So here is where things get messy:
This application is built with .NET Core 3.1. On the server, going HTTPS to the site everything runs without issue (it requires a login). Going HTTP to the site it just boots you back out to the login screen, no error no warning, just login over and over. The Dev claims it to be a security feature to ensure traffic is secure (which I understand) and per the Dev cannot be turned off (core doesn't allow it to be off, which I don't understand).
Going through the Load Balancer yields the same result as HTTP on the server (makes sense as it is being delivered there as HTTP).

Here where the assistance is needed.
In the Load Balancer we header tag the following:
HTTP_FRONT_END_HTTPS               On
HTTP_X_FORWARDED_FOR       (client IP)

The headers get modified, I requested that a full header site be placed there for viewing, and they are being tagged.
Not sure why Forwarded_For needs to be there but here we are.

This should allow .NET Core 3.1 to see the load as HTTP, but alas it does not. I think it is an app problem, but here we are with it now being my issue.

Thank you as always for any assistance that can be provided.
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Distinguished Expert 2017

Looks like the app designed requiring HTTPS access

You could configure the loadbalancer to devide and forward to HTTPS ..
While your loadbalancer will be doing double work...

Alternatively fix the application whether it is IIS that on the sevurity has SSL required......

Confirm, by going to the server directly via http and see what happens.
Chief Technology Ninja
Distinguished Expert 2018
Hi Mike,

I do not think what your developer is telling you is the truth. .Net core allows you to turn off HTTPS if needed.

I think this could be very well classic Dev vs SysAdmin case, S/He might not want to give in an inch OR maybe there is a valid reason (maybe they are using api end points on the same portal) and not using HTTPS will invite its own set of challenges.

With that said, here is a reference link: https://docs.microsoft.com/en-us/aspnet/core/security/enforcing-ssl?view=aspnetcore-3.1&tabs=visual-studio
in case you want to check it out yourself that how .Net Core allows you to turn on / turn off HTTPS redirection.

All the best.

Mike SchrockIT Operations Manager


The Dev is out today, but if I had to take a stab at it, most likely they left the Configure for HTTPS button checked when creating the app.
I'll circle back tomorrow.
Chinmay PatelChief Technology Ninja
Distinguished Expert 2018

I think they might have configured it on their own as well, we really do not know how they are setting up the app. It is a good idea to check with them and get the clarity.
Mike SchrockIT Operations Manager


I shall do my best!
Distinguished Expert 2017

You could take the overhead and direct the loadbalancer to setup a secure session to the backend systems as a test.

If you can create another vip on the loadbalancer that targets one of the systems using the https
and then see if it works.