DifferentialAzureADSyncViaPowerShell.ps1

# Adding the AD AuthN library to your PowerShell Session.
# the default path to where the ADAL GraphAPI PS Module puts the Libs
Add-Type -Path 'C:\Program Files\WindowsPowerShell\Modules\AzureADPreview\1.1.143.0\Microsoft.IdentityModel.Clients.ActiveDirectory.dll'

# Your Azure tenant name 
$tenantID = "mytenant.com.au"
$authString = "https://login.microsoftonline.com/$tenantID" 

# username and password. The username must be MFA disabled user Admin at least, and must not be a live id.
$username = "doc@mytenant.com.au"
$password = "Sup3rS3cr3t1"

# The resource URI for your token.
$resource = "https://graph.windows.net/"

# Object Type (eg. Users, Groups, Contacts, DirectoryObjects)
$object = "directoryObjects"

# What Objects are we interested in. I'm expliciting calling User, Group and Contact even though they are meant to be implied (default)
# as I've read about mixed results with differential sync across different object types
$Searchfilter ="`$filter=isof('Microsoft.DirectoryServices.User') or isof('Microsoft.DirectoryServices.Group') or isof('Microsoft.DirectoryServices.Contact')"

# Output Directory and file for Differential Cookie
$downloadDirectory = "C:\Users\Darren\Dropbox\Kloud\Powershell\O365\DeltaSync"
$cookieFile = "\AADDeltaCookie.txt"
$filepath = $downloadDirectory +$cookieFile 

# Reset results var 
$query = $null

# Read in Delta Cookie if it exists, if not create the file for storing the cookie
if(!(Test-Path $filepath))
    {
        $cookie = New-Item -Path $filepath -ItemType File
    }
    else
    {
        $cookie = Get-Item -Path $filepath
    }

# This is the powershell common client id.
$client_id = "1950a258-227b-4e31-a9cf-717495945fc2"

# Create a client credential with the above common client id, username and password.
$creds = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.UserCredential" `
                    -ArgumentList $username,$password

# Create a authentication context with the above authentication string.
$authContext = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext" `
                    -ArgumentList $authString

# Acquire access token from server.
$authenticationResult = $authContext.AcquireToken($resource,$client_id,$creds)

# Use the access token to setup headers for your http request.
$authHeader = $authenticationResult.AccessTokenType + " " + $authenticationResult.AccessToken
$headers = @{"Authorization"=$authHeader; "Content-Type"="application/json"}

# URI to get first set of objects
if((Get-Item $cookie).length -gt 0kb){
        # Delta cookie value exists. Get it
        $url = Get-Content $cookie.FullName 
        # omit &ocp-aad-dq-include-only-changed-properties=true from the URI if you want the full object
        $url += '&ocp-aad-dq-include-only-changed-properties=true&api-version=1.6' -f $authenticationResult.TenantId        
    }
    else
    {
        # no Delta Cookie, so first run, so return everything
        $url = "https://graph.windows.net/{0}/$($object)?&$($Searchfilter)&api-version=1.6&deltaLink="
    }

# Get first set of results
$query = Invoke-RestMethod -Method Get -Headers @{
    Authorization   = $authenticationResult.CreateAuthorizationHeader()
    'Content-Type'  = "application/json"
    # unremark if you just want the DeltaLink from now
    # 'ocp-aad-dq-include-only-delta-token' = "true"
} -Uri ($url -f $authenticationResult.TenantId)
$query.value.Count

# An Array for the retuned objects to go into 
$tenantObjects = @()
# Add in our first objects
$tenantObjects += $query.value
$moreObjects = $query 

# Get all the remaining objects in batches if we didn't return them all already
if ($query.'aad.nextLink'){
    $moreObjects.'aad.nextLink' = $query.'aad.nextLink'
    do
        {
            $moreObjects = Invoke-RestMethod -Method Get -Headers @{
            Authorization   = $authenticationResult.CreateAuthorizationHeader()
            'Content-Type'  = "application/json"
            } -Uri ($moreObjects.'aad.nextLink'+'&api-version=1.6' -f $authenticationResult.TenantId)
            $moreObjects.value.count
            $tenantObjects += $moreObjects.value
            $tenantObjects.Count

        } while ($moreObjects.'aad.nextLink')
}

$moreObjects.value | out-gridview

# store the DeltaLink in a file for next time we run the script
$moreObjects.'aad.deltaLink' | Out-File $cookie