Monday, 5 August 2019

Get Microsoft Graph API Access Token using ClientID and ClientSecret

In some cases, apps or users might want to acquire Microsoft Graph access token by using the ClientID (Azure AD Application ID) and ClientSecret instead of providing their own credentials. In many cases, these are background services or automation jobs which require to authenticate a script without user interaction (Unattended Authentication). I would also recommend you to read the post Get access without a user.

Note: Assume that you have already registered an App in Azure AD through App Registration and you have the Client ID, Client Secret, and your Tenant Domain Name (or Tenant ID).

Required Parameters :

  • ClientID - AppId of your Azure AD Application.
  • ClientSecret - A secret code that you get from the registered app.
  • Tenant - Provide your tenant id or tenant domain name (ex: xxxxx.onmicrosoft.com). Refer this post to find your tenant id.

Get Access Token :

In the OAuth 2.0 client credentials grant flow, you can acquire an access token by sending a POST request to the /token identity platform endpoint with required parameters :
Http Method : POST
Endpoint URL : https://login.microsoftonline.com/Tenant/oauth2/v2.0/token
Content-Type : application/x-www-form-urlencoded
Body : scope=https://graph.microsoft.com/.default&grant_type=client_credentials&client_id=535fb089-9ff3-47b6-9bfb-4f1264799865&client_secret=qWgdYAmab0YSkuL1qKv5bPX

Get Graph Access Token Using Powershell :

In Powershell, you can use the Invoke-RestMethod cmdlet to send the post request to the /token identity endpoint. Use the below commands after replacing your own values for ClientID, ClientSecret and TenantId.
#This is the ClientID (Application ID) of registered AzureAD App
$ClientID = "535fb089-9ff3-47b6-9bfb-4f1264799865"
#This is the key of the registered AzureAD app
$ClientSecret = "qWgdYAmab0YSkuL1qKv5bPX"
#This is your Office 365 Tenant Domain Name or Tenant Id
$TenantId = "m365xxxxx.onmicrosoft.com"
#$TenantId = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
$Body = @{client_id=$ClientID;client_secret=$ClientSecret;grant_type="client_credentials";scope="https://graph.microsoft.com/.default";}
$OAuthReq = Invoke-RestMethod -Method Post -Uri https://login.microsoftonline.com/$TenantId/oauth2/v2.0/token -Body $Body
$TokenType = $OAuthReq.token_type
$AccessToken = $OAuthReq.access_token

Call Graph API Using Powershell :

The below command retrieves all the Azure AD user details by passing the acquired access token.
$apiUrl = "https://graph.microsoft.com/v1.0/users"
$users = Invoke-RestMethod -Headers @{Authorization = "Bearer $AccessToken"} -Uri $apiUrl -Method Get
Note : Before using the above end-point (https://graph.microsoft.com/v1.0/users), you should have added the Application permission User.Read.All (or User.ReadWrite.All) in your Azure AD app and you should have already provided Admin consent for your app.

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