Get-AppRegistrationExpiration.ps1

<#
Disclaimer
The sample scripts are not supported under any Microsoft standard support program or service.
The sample scripts are provided AS IS without warranty of any kind. Microsoft further disclaims all implied warranties including, without limitation, 
any implied warranties of merchantability or of fitness for a particular purpose. The entire risk arising out of the use or performance of the sample 
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Microsoft has been advised of the possibility of such damages.
#>


Function _SendToLogAnalytics{
    Param(
        [string]$customerId,
        [string]$sharedKey,
        [string]$logs,
        [string]$logType,
        [string]$timeStampField
    )
        # Generate the body for the Invoke-WebRequest
        $body = ([System.Text.Encoding]::UTF8.GetBytes($Logs))
        $method = "POST"
        $contentType = "application/json"
        $resource = "/api/logs"
        $rfc1123date = [DateTime]::UtcNow.ToString("r")
        $contentLength = $body.Length

        #Create the encoded hash to be used in the authorization signature
        $xHeaders = "x-ms-date:" + $rfc1123date
        $stringToHash = $method + "`n" + $contentLength + "`n" + $contentType + "`n" + $xHeaders + "`n" + $resource
        $bytesToHash = [Text.Encoding]::UTF8.GetBytes($stringToHash)
        $keyBytes = [Convert]::FromBase64String($sharedKey)
        $sha256 = New-Object System.Security.Cryptography.HMACSHA256
        $sha256.Key = $keyBytes
        $calculatedHash = $sha256.ComputeHash($bytesToHash)
        $encodedHash = [Convert]::ToBase64String($calculatedHash)
        $authorization = 'SharedKey {0}:{1}' -f $customerId,$encodedHash

        # Create the uri for the data insertion endpoint for the Log Analytics workspace
        $uri = "https://" + $customerId + ".ods.opinsights.azure.us" + $resource + "?api-version=2016-04-01"

        # Create the headers to be used in the Invoke-WebRequest
        $headers = @{
            "Authorization" = $authorization;
            "Log-Type" = $logType;
            "x-ms-date" = $rfc1123date;
            "time-generated-field" = $timeStampField;
        }
        
        # Try to send the logs to the Log Analytics workspace
        Try{
            $response = Invoke-WebRequest `
            -Uri $uri `
            -Method $method `
            -ContentType $contentType `
            -Headers $headers `
            -Body $body `
            -UseBasicParsing `
            -ErrorAction stop
        }
        # Catch any exceptions and write them to the output 
        Catch{
            Write-Error "$($_.Exception)"
            throw "$($_.Exception)" 
        }
        # Return the status code of the web request response
        return $response
}


#### End Function Declaration Section ##############################################################

####Connect to the O365 Tenant using AutomationCredential###########################################

Try{
    $credentials = Get-AutomationPSCredential -Name "AppRegistrationMonitor" -ErrorAction Stop
} catch {
    write-error "Unable to find AutomationPSCredential"
    throw "Unable to find AutomationPSCredential"
}

Try {
    $tenantID= Get-AutomationVariable -Name 'MonitoredTenantID'
    Connect-AzAccount -ServicePrincipal -Credential $credentials -Tenant $tenantID
} catch {
    write-error "$($_.Exception)"
    throw "$($_.Exception)"
}
Write-output 'Gathering necessary information...'

$applications = Get-AzADApplication
$servicePrincipals = Get-AzADServicePrincipal
$timeStamp = Get-Date -format o


$appWithCredentials = @()
$appWithCredentials += $applications | Sort-Object -Property DisplayName | % {
    $application = $_
    $sp = $servicePrincipals | ? ApplicationId -eq $application.ApplicationId
    Write-Verbose ('Fetching information for application {0}' -f $application.DisplayName)
    $application | Get-AzADAppCredential -ErrorAction SilentlyContinue | Select-Object `
    -Property @{Name='DisplayName'; Expression={$application.DisplayName}}, `
    @{Name='ObjectId'; Expression={$application.Id}}, `
    @{Name='ApplicationId'; Expression={$application.ApplicationId}}, `
    @{Name='KeyId'; Expression={$_.KeyId}}, `
    @{Name='Type'; Expression={$_.Type}},`
    @{Name='StartDate'; Expression={$_.StartDate -as [datetime]}},`
    @{Name='EndDate'; Expression={$_.EndDate -as [datetime]}}
  }

Write-output 'Validating expiration data...'
$today = (Get-Date).ToUniversalTime()
$appWithCredentials | Sort-Object EndDate | % {
        if($_.EndDate -lt $today) {
            $days= ($_.EndDate-$Today).Days
            $_ | Add-Member -MemberType NoteProperty -Name 'Status' -Value 'Expired'
            $_ | Add-Member -MemberType NoteProperty -Name 'TimeStamp' -Value "$timestamp"
            $_ | Add-Member -MemberType NoteProperty -Name 'DaysToExpiration' -Value $days
        }  else {
            $days= ($_.EndDate-$Today).Days
            $_ | Add-Member -MemberType NoteProperty -Name 'Status' -Value 'Valid'
            $_ | Add-Member -MemberType NoteProperty -Name 'TimeStamp' -Value "$timestamp"
            $_ | Add-Member -MemberType NoteProperty -Name 'DaysToExpiration' -Value $days
        }
}



$audit = $appWithCredentials | convertto-json
$customerId= Get-AutomationVariable -Name 'LogAnalyticsWorkspaceID'
$sharedKey= Get-AutomationVariable -Name 'LogAnalyticsPrimaryKey'

_SendToLogAnalytics -CustomerId $customerId `
                        -SharedKey $sharedKey `
                        -Logs $Audit `
                        -LogType "AppRegistrationExpiration" `
                        -TimeStampField "TimeStamp"
Write-Output 'Done.'