Private/SiemAuth.ps1
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$script:SiemTokenCache = @{} function ConvertFrom-SiemSecureString { [CmdletBinding()] param( [Parameter(Mandatory = $true)] [SecureString]$SecureString ) $bstr = [IntPtr]::Zero try { $bstr = [Runtime.InteropServices.Marshal]::SecureStringToBSTR($SecureString) return [Runtime.InteropServices.Marshal]::PtrToStringBSTR($bstr) } finally { if ($bstr -ne [IntPtr]::Zero) { [Runtime.InteropServices.Marshal]::ZeroFreeBSTR($bstr) } } } function ConvertTo-SiemSecureString { [CmdletBinding()] param( [Parameter(Mandatory = $true)] [AllowEmptyString()] [string]$PlainText ) $secure = New-Object System.Security.SecureString foreach ($character in $PlainText.ToCharArray()) { $secure.AppendChar($character) } $secure.MakeReadOnly() return $secure } function Get-SiemHttpStatusCode { [CmdletBinding()] param( [AllowNull()] [object]$Exception ) if ($null -eq $Exception) { return $null } $responseProperty = $Exception.PSObject.Properties['Response'] if ($null -eq $responseProperty -or $null -eq $responseProperty.Value) { return $null } $statusProperty = $responseProperty.Value.PSObject.Properties['StatusCode'] if ($null -eq $statusProperty -or $null -eq $statusProperty.Value) { return $null } try { return [int]$statusProperty.Value } catch { return $null } } function Assert-SiemTenantId { [CmdletBinding()] param( [Parameter(Mandatory = $true)] [string]$TenantId ) if ($TenantId -notmatch '^[A-Za-z0-9][A-Za-z0-9.-]{0,255}$' -or $TenantId.Contains('..')) { throw 'TenantId must be a tenant GUID or domain name without path separators.' } } function Assert-SiemMonitorScope { [CmdletBinding()] param( [Parameter(Mandatory = $true)] [string]$MonitorScope ) $parsed = $null if (-not [Uri]::TryCreate($MonitorScope, [UriKind]::Absolute, [ref]$parsed) -or $parsed.Scheme -ne 'https' -or -not $parsed.AbsolutePath.EndsWith('/.default', [StringComparison]::OrdinalIgnoreCase) -or -not [string]::IsNullOrEmpty($parsed.Query) -or -not [string]::IsNullOrEmpty($parsed.Fragment) -or -not [string]::IsNullOrEmpty($parsed.UserInfo)) { throw 'MonitorScope must be an HTTPS resource scope ending in /.default, without a query or fragment.' } } function Assert-SiemEndpointUri { [CmdletBinding()] param( [Parameter(Mandatory = $true)] [string]$Uri, [Parameter()] [ValidateSet('SplunkHEC', 'Sentinel', 'SentinelLogsIngestion', 'GenericWebhook')] [string]$Destination = 'GenericWebhook', [Parameter()] [switch]$RequireHttps ) $parsed = $null if (-not [Uri]::TryCreate($Uri, [UriKind]::Absolute, [ref]$parsed) -or ($parsed.Scheme -ne 'https' -and $parsed.Scheme -ne 'http') -or -not [string]::IsNullOrEmpty($parsed.UserInfo)) { throw 'The SIEM endpoint must be an absolute HTTP(S) URI without embedded user information.' } if (($RequireHttps.IsPresent -or $Destination -eq 'SentinelLogsIngestion') -and $parsed.Scheme -ne 'https') { throw 'This SIEM destination requires an HTTPS endpoint.' } if ($Destination -eq 'SentinelLogsIngestion') { if ($parsed.AbsolutePath -notmatch '^/dataCollectionRules/[^/]+/streams/[^/]+/?$' -or $parsed.Query -notmatch '^\?api-version=[A-Za-z0-9._-]+$' -or -not [string]::IsNullOrEmpty($parsed.Fragment)) { throw 'The Logs Ingestion URI must use /dataCollectionRules/{dcrId}/streams/{stream}?api-version={version}.' } } return $parsed } function Get-SiemSafeEndpoint { [CmdletBinding()] param( [Parameter(Mandatory = $true)] [Uri]$Uri ) $port = $Uri.Port if ($port -lt 0) { $port = $(if ($Uri.Scheme -eq 'https') { 443 } else { 80 }) } return ('{0}://{1}:{2}' -f $Uri.Scheme, $Uri.Host, $port) } function Get-SiemAccessToken { [CmdletBinding()] param( [Parameter(Mandatory = $true)] [string]$TenantId, [Parameter(Mandatory = $true)] [string]$ClientId, [Parameter(Mandatory = $true)] [SecureString]$ClientSecret, [Parameter(Mandatory = $true)] [string]$MonitorScope, [Parameter()] [ValidateRange(0, 10)] [int]$MaxRetries = 3, [Parameter()] [ValidateRange(0, 60000)] [int]$ThrottleMs = 250, [Parameter()] [switch]$ForceRefresh ) Assert-SiemTenantId -TenantId $TenantId Assert-SiemMonitorScope -MonitorScope $MonitorScope if ([string]::IsNullOrWhiteSpace($ClientId)) { throw 'ClientId is required for Entra client-credentials authentication.' } if ($ClientSecret.Length -eq 0) { throw 'ClientSecret cannot be empty.' } $cacheKey = '{0}|{1}|{2}' -f $TenantId.ToLowerInvariant(), $ClientId.ToLowerInvariant(), $MonitorScope if ($ForceRefresh.IsPresent -and $script:SiemTokenCache.ContainsKey($cacheKey)) { $script:SiemTokenCache.Remove($cacheKey) } if ($script:SiemTokenCache.ContainsKey($cacheKey)) { $cached = $script:SiemTokenCache[$cacheKey] if ([DateTimeOffset]::UtcNow -lt $cached.ExpiresAt) { return [string]$cached.AccessToken } $script:SiemTokenCache.Remove($cacheKey) } $tokenEndpoint = 'https://login.microsoftonline.com/{0}/oauth2/v2.0/token' -f $TenantId $plainSecret = $null $requestBody = $null $response = $null try { $plainSecret = ConvertFrom-SiemSecureString -SecureString $ClientSecret $requestBody = @{ grant_type = 'client_credentials' client_id = $ClientId client_secret = $plainSecret scope = $MonitorScope } $attempt = 0 while ($true) { $attempt++ try { $response = Invoke-RestMethod -Uri $tokenEndpoint -Method Post -ContentType 'application/x-www-form-urlencoded' -Body $requestBody -TimeoutSec 100 -UseBasicParsing -ErrorAction Stop break } catch { $statusCode = Get-SiemHttpStatusCode -Exception $_.Exception $isTransient = ($null -ne $statusCode) -and (($statusCode -eq 429) -or ($statusCode -ge 500 -and $statusCode -le 599)) if ($isTransient -and $attempt -le $MaxRetries) { $backoffMs = $ThrottleMs * [int][math]::Pow(2, $attempt) Write-Warning "Entra token request transient failure (HTTP $statusCode); retry $attempt of $MaxRetries in $backoffMs ms." if ($backoffMs -gt 0) { Start-Sleep -Milliseconds $backoffMs } continue } $statusText = $(if ($null -ne $statusCode) { " (HTTP $statusCode)" } else { '' }) throw "Entra token request failed after $attempt attempt(s)$statusText." } } $accessTokenProperty = $response.PSObject.Properties['access_token'] $expiresProperty = $response.PSObject.Properties['expires_in'] if ($null -eq $accessTokenProperty -or [string]::IsNullOrWhiteSpace([string]$accessTokenProperty.Value) -or $null -eq $expiresProperty) { throw 'Entra token response did not contain access_token and expires_in.' } $expiresIn = 0.0 if (-not [double]::TryParse([string]$expiresProperty.Value, [Globalization.NumberStyles]::Float, [Globalization.CultureInfo]::InvariantCulture, [ref]$expiresIn) -or $expiresIn -le 0) { throw 'Entra token response contained an invalid expires_in value.' } $script:SiemTokenCache[$cacheKey] = [PSCustomObject]@{ AccessToken = [string]$accessTokenProperty.Value ExpiresAt = [DateTimeOffset]::UtcNow.AddSeconds($expiresIn - 300) } return [string]$accessTokenProperty.Value } finally { if ($null -ne $requestBody) { $requestBody['client_secret'] = $null } $plainSecret = $null $response = $null } } |