Overview

When you try authenticate on sharepoint portal over a proxy server the sharepoint rejects the firsts request and sends an 401 Unauthorized error.

or in debug mode

root@artica-4:~# curl --verbose --proxy 127.0.0.1:3128 -u teste http://mysharepoint.local
Enter host password for user 'teste':
* Expire in 0 ms for 6 (transfer 0x5559e35e3f90)
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Expire in 200 ms for 4 (transfer 0x5559e35e3f90)
* Connected to 127.0.0.1 (127.0.0.1) port 3128 (#0)
* Server auth using Basic with user 'teste'
> GET http://mysharepoint.local/ HTTP/1.1
> Host: mysharepoint.local
> Authorization: Basic YWxzX2x1cm91cjpBbGx1cysyODA2
> User-Agent: curl/7.64.0
> Accept: */*
> Proxy-Connection: Keep-Alive
>
< HTTP/1.1 401 Unauthorized
< SPRequestGuid: ee760b22-120e-459b-9fb9-145cea1230e1
< X-Powered-By: ASP.NET
< MicrosoftSharePointTeamServices: 14.0.0.6108

How to fix it?

To fix this issue you most enable persistents connection on Artica Proxy settings.

1. Open Your Proxy menu
2. Select Global Settings
3. Click on the tab TimeOuts
4. On Persistent connections settings enable the options Server persistent connections and Client persistent connections
5. Click on Apply button