Graph API Authentification

Requirements: An App Registration with the appropriate permissions and a ClientSecret.

First, the authentication header must be compiled in the script. With this header (here the variable $Header) the authentication at the Graph API can be executed. The top three variables now contain the values, which were compiled in an upper point.

$TenantID = "<tenantid>"
$ClientId = "<cliendid>"
$ClientSecret = "<clientsecret>"
 
$Body = @{
"tenant" = $TenantId
"client_id" = $ClientId
"scope" = "https://graph.microsoft.com/.default"
"client_secret" = $ClientSecret
"grant_type" = "client_credentials"
}
 
$Params = @{
"Uri" = "https://login.microsoftonline.com/$TenantId/oauth2/v2.0/token"
"Method" = "Post"
"Body" = $Body
"ContentType" = "application/x-www-form-urlencoded"
}
$AuthResponse = Invoke-RestMethod @Params
 
$Header = @{
    "Authorization" = "Bearer $($AuthResponse.access_token)"
}