So there’s this problem with lots of Microsoft API’s not allowing service principals to call them. I’ve written about this a few times in the past 🙂

These api’s want a user. And a user has to do MFA, right?

Not with this!

When I read Nathan McNulty’s LinkedIn post this morning I got a bit hyped and just HAD to get it working. He has a way to use a stored passkey to log in silently to all admin portals/hidden api’s etc.

The missing part I wanted to solve, is to actually generate that passkey for a given global admin in the tenant.

Took a bit of messing around with how to generate the keys using a virtual authenticator, but it works! Here it is:

https://github.com/jflieben/assortedFunctionsV2/blob/main/New-FidoKey.ps1

So basically:

1. register app with client id/secret and UserAuthenticationMethod.ReadWrite.All
2. run New-FidoKey
3. use the file it outputs with Nathan’s passkey login function

I should also give an honorary mention to Fabian Bader for the work he did to get us here!

disclaimer: don’t store this stuff where anyone can find it!

disclaimer2: you’ll have to set your fido policy to allow not force attestion or key restrictions