Sites.Selected MS Graph API permissions were introduced by Microsoft in March 2021. One year later, in 2022 they added SharePoint Sites.Selected API permissions.

Why is this so important? Because MS Graph API for SharePoint is still limited and cannot cover all possible needs. I’d estimate: 90% of applications use SharePoint CSOM, so developers have to use AppInv.aspx to provide permissions for their applications to SharePoint API.

But from this moment – having SharePoint API permissions in MS Graph – in theory – we can fully rely on permissions provided in Azure and – in theory – this should allow us disable SharePoint-Apps only principal:

Set-SPOTenant -DisableCustomAppAuthentication $true

My math professor taught me: “before trying to find a solution – ensure the solution exists.” So let us test:

Are we really able to work with a specific SharePoint site using MS Graph and SharePoint API Sites.Selected permissions provided via Microsoft Azure?

What will happen with our new/legacy applications if we disable SharePoint app-only SPNs (DisableCustomAppAuthentication)?

I’m getting controversial test results… maybe PnP.PowerShell 1.10 is not fully support SharePoint Sites.Selected API.

Tech Wizard (Sukhija Vikas) on March 20, 2022 in the article “SharePoint and Graph API APP only permissions for Selected Sites” suggests using pre-release (AllowPrerelease).

So please ignore the following for a while.

Meantime I’ll test providing SharePoint Sites.Selected API permissions via Graph API call.

(wip) Test set #1: Certificate vs Secret

DisableCustomAppAuthentication: $false (SP-app-only spns are enabled).
All applications have “write” access provided to a specific site only.
Connecting with Connect-PnPOnline and then test access with Get-PnPSite

App / Get-PnPSite	Secret	Certificate
ACS based (Azure+AppInv)	OK	The remote server returned an error: (401) Unauthorized.
MS Graph API Sites.Selected	The remote server returned an error: (403) Forbidden.	The remote server returned an error: (401) Unauthorized.
SharePoint API Sites.Selected	OK	OK
MS Graph API + SharePoint API Sites.Selected	Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))	OK
App with no permissions	The remote server returned an error: (403) Forbidden	The remote server returned an error: (401) Unauthorized

(wip) Test set #2: Sites.Selected SharePoint vs MS Graph (secret)

• DisableCustomAppAuthentication = $false
  (SP-app-only spns are enabled).
• All applications have “write” access provided to a specific site only.
• Using Client Secret (not a certificate)
• Using PnP.PowerShell

Action/Via	SharePoint + MS Graph Sites.Selected “secret”	SharePoint Sites.Selected “secret”	MS Graph Sites.Selected “secret”
Connect-PnPOnline	WARNING: Connecting with Client Secret uses legacy authentication and provides limited functionality. We can for instance not execute requests towards the Microsoft Graph, which limits cmdlets related to Microsoft Teams, Microsoft Planner, Microsoft Flow and Microsoft 365 Groups.	WARNING: Connecting with Client Secret uses legacy authentication and provides limited functionality. We can for instance not execute requests towards the Microsoft Graph, which limits cmdlets related to Microsoft Teams, Microsoft Planner, Microsoft Flow and Microsoft 365 Groups.	WARNING: Connecting with Client Secret uses legacy authentication and provides limited functionality. We can for instance not execute requests towards the Microsoft Graph, which limits cmdlets related to Microsoft Teams, Microsoft Planner, Microsoft Flow and Microsoft 365 Groups.
Get-PnPSite	OK	OK	The remote server returned an error: (403) Forbidden.
Get-PnPList	OK	OK
Get-PnPListItem	OK	OK
Set-PnPSite		Attempted to perform an unauthorized operation.
Set-PnPList		Attempted to perform an unauthorized operation.
Set-PnPListItem	OK	OK
New-PnPList		Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
Add-PnPListItem		OK

(wip) Test set #3: Read vs Write vs FullControl

DisableCustomAppAuthentication = $false
(SP-app-only spns are enabled).
All applications have Sites.Selected SharePoint and MS Graph API permissions.
Using Client Secret (not a certificate)
Using PnP.PowerShell

	Read	Write	FullControl
Connect-PnPOnline	WARNING: Connecting with Client Secret uses legacy authentication and provides limited functionality. We can for instance not execute requests towards the Microsoft Graph, which limits cmdlets related to Microsoft Teams, Microsoft Planner, Microsoft Flow and Microsoft 365 Groups.	WARNING: Connecting with Client Secret uses legacy authentication and provides limited functionality. We can for instance not execute requests towards the Microsoft Graph, which limits cmdlets related to Microsoft Teams, Microsoft Planner, Microsoft Flow and Microsoft 365 Groups.	WARNING: Connecting with Client Secret uses legacy authentication and provides limited functionality. We can for instance not execute requests towards the Microsoft Graph, which limits cmdlets related to Microsoft Teams, Microsoft Planner, Microsoft Flow and Microsoft 365 Groups.
Get-PnPSite	Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
Get-PnPList	Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
Get-PnPListItem
Set-PnPSite
Set-PnPList
Set-PnPListItem
New-PnPList
Add-PnPListItem

(wip) Test set #5: Certificate vs Secret

C#, SharePoint CSOM, PnP.Framework

Findings

PnP.PowerShell Get-, Grant-, Set- and Revoke-PnPAzureADAppSitePermission cmdlets require Azure App with MS Graph Sites.FullControl.All app permissions (otherwise it says “Access denied”) and authentication via certificate (otherwise it says “This cmdlet does not work with a ACS based connection towards SharePoint.”)

The same actions – managing permissions for the client app to the specific site collections – could be done via Microsoft Graph Sites Permissions API using just secret-based authentication.

If an azure app does not have Sites.Selected API permissions configured – “Grant-PnPAzureADAppSitePermission” works as expected – no error messages – the output is normal – as if Sites.Selected API permissions were configured in the app. The same for Get-, -Set and Revoke-. Permissions provided for the app to the site are not effective though: Connect-PnPOnline works well, but all other commands – starting from Get-PnPSite – returns “The remote server returned an error: (403) Forbidden.”

If an app have no permissions to SharePoint – “Connect-PnPOnline” works ok, but “Get-PnPSite” return an error: “The remote server returned an error: (403) Forbidden.”

Set-PnPAzureADAppSitePermission gives an error message “code”:”generalException”,”message”:”General exception while processing”
if the site is not specified.

AppInv is not working?

Error: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))

References

• Track SharePoint App-only Service Principals in Microsoft 365
• Microsoft Graph Sites Permissions API
• “SharePoint and Graph API APP only permissions for Selected Sites”

Testing environment

• Microsoft 365 E5 Dev environment
• PowerShell 7.2.2
• PnP.PowerShell 1.10
• “write” permissions to the specific sites for client apps were assigned via PnP.PowerShell