Automating with PowerShell: Deploying AAD branding to all clients

I haven’t really been blogging the last week, that’s mostly because I’ve been focused on the CyberDrainCTF, which is going amazing. I am so happy with another successful event. Today, to catch up I figured I’d cover a request I saw in MSPGeek. One of the users there wanted to centrally change the branding of a tenant, specifically to change the texts show at logon.

The following script changes the branding text, it’s also easy to adapt the script to update the images, the logos, or even help with localization. To check out all the options I suggest grabbing the documentation by Microsoft here. Remember that you need a P1 subscription or higher for branded portals.

The Script

As always we’re using the Secure Application Model to connect to M365 so you can run this script without intervention. You will need to add some permissions to your secure application:

Go to the Azure Portal.
Click on Azure Active Directory, now click on “App Registrations”.
Find your Secure App Model application. You can search based on the ApplicationID.
Go to “API Permissions” and click Add a permission.
Choose “Microsoft Graph” and “Delegated permission”.
Add the “Organization.ReadWrite.all” permission.
Finally, click on “Grant Admin Consent for Company Name.

From then on, you can execute this script to update the branding.

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######### Secrets #########
$ApplicationId = 'AppID'
$ApplicationSecret = 'AppSecret'
$RefreshToken = 'LongRefreshToken'
######## Secrets #########
write-host "Creating credentials and tokens." -ForegroundColor Green

$credential = New-Object System.Management.Automation.PSCredential($ApplicationId, ($ApplicationSecret | Convertto-SecureString -AsPlainText -Force))
$aadGraphToken = New-PartnerAccessToken -ApplicationId $ApplicationId -Credential $credential -RefreshToken $refreshToken -Scopes 'https://graph.windows.net/.default' -ServicePrincipal
$graphToken = New-PartnerAccessToken -ApplicationId $ApplicationId -Credential $credential -RefreshToken $refreshToken -Scopes 'https://graph.microsoft.com/.default' -ServicePrincipal

write-host "Creating body to request Graph access for each client." -ForegroundColor Green
$Authbody = @{
    'resource'      = 'https://graph.microsoft.com'
    'client_id'     = $ApplicationId
    'client_secret' = $ApplicationSecret
    'grant_type'    = "client_credentials"
    'scope'         = "openid"
}


write-host "Connecting to Office365 to get all tenants." -ForegroundColor Green
Connect-MsolService -AdGraphAccessToken $aadGraphToken.AccessToken -MsGraphAccessToken $graphToken.AccessToken
$customers = Get-MsolPartnerContract -All
foreach ($Customer in $Customers) {
    $ClientToken = Invoke-RestMethod -Method post -Uri "https://login.microsoftonline.com/$($customer.tenantid)/oauth2/token" -Body $Authbody -ErrorAction Stop
    $headers = @{ "Authorization" = "Bearer $($ClientToken.access_token)" }
    $body = [PSCustomObject]@{
        backgroundColor  = '#FFFF33'
        signInPageText   = 'Please sign in to your M365 account'
        usernameHintText = 'your username is often your e-mail address.'
    } | ConvertTo-Json
    try {
        write-host "Processing $($customer.DefaultDomainName)"
        Invoke-RestMethod -Uri "https://graph.microsoft.com/v1.0/organization/$($customer.TenantId)/branding" -Headers $Headers -Method PATCH -body $body -ContentType "application/json"
    }
    Catch {
        write-host "Failed to process for tenant $($customer.DefaultDomainName) - Exception: $($_.Exception.Message)" -ForegroundColor Yellow
    }
}

And that’s it! as always, Happy PowerShelling 🙂