Using SharePoint Web Services from Anonymous Mode

NOTE: This is only applicable to on premise.

You might have a need to access the SharePoint Web Services (in my case it was the UserProfileService.asmx) from an anonymous site. The issue is authentication - through both CSOM and Server Side code, there are problems with authentication.

A test with elevated, impersonation using a token and impersonation in .NET failed to produce results. In all cases, the permissions were blocked (user not part of the site, etc.). The actual fix was from a post I stumbled on wherein you can add a section to the Web.config to make it work.

Look for the end tag </system.web.extensions> and add the following just below it:

<!-- Disable anonymous access to _vti_bin -->

<location path="_vti_bin">

    <system.web>                 

        <authorization>

            <deny users="?" />

        </authorization>

    </system.web>

</location>

This effectively blocks anon-users from accessing _vti_bin (a good thing anyway) but permits the web services to work (you still need to set network credentials).

FYI: You should be using SPWebConfigModification to make the change - while I've documented this myself, here's another quick guide: https://blogs.technet.microsoft.com/heyscriptingguy/2010/09/14/use-powershell-to-script-changes-to-the-sharepoint-web-config-file/


Kudos to: http://www.sharepointdiary.com/2012/06/sharepoint-web-services-exposed-to-anonymous-users.html#ixzz551Cj8h3j

Getting the Public Key Token for a DLL (and where the heck is sn.exe?)

An oldie but a goodie...(and for my own memory). To get the Public Key Token for a DLL is to simply use the "Strong Name Tool" (more from Microsoft here: https://docs.microsoft.com/en-us/dotnet/framework/tools/sn-exe-strong-name-tool).

The SN.exe tool can be found under the SDK's folder, under C:\Program Files (x86)\Microsoft SDKs\Windows. You can simply open the folder and search for sn.exe and pick the latest based on what version of .NET you have. For example, it's C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6.1 Tools.

Note: If you use the Developer Command Window, the path will already be loaded.

Simply navigate to the folder where the DLL is and enter:

sn  -T <ddl name>.dll

Example:

sn -T MyNewDLL.dll

* If you don't know where the DLL is, you can find it under the bin\debug or bin\release folders in your Visual Studio project.