Private/ConvertFrom-Base64UrlEncodedString.ps1
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function ConvertFrom-Base64UrlEncodedString { <# .SYNOPSIS Decodes a base 64 URL encoded string. .DESCRIPTION Decodes a base 64 URL encoded string such as a JWT header or payload. .PARAMETER InputString The string to be base64 URL decoded. .PARAMETER AsBytes Instructions this function to return the result as a byte array as opposed to a default string. .EXAMPLE "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9" | ConvertFrom-Base64UrlEncodedString Decodes a JWT header. .INPUTS System.String A string is received by the InputString parameter. .OUTPUTS System.String Returns a base 64 URL decoded string for the given input. .LINK https://tools.ietf.org/html/rfc4648#section-5 #> [CmdletBinding()] [OutputType([System.String], [System.Byte[]])] param ( [Parameter(Position = 0, Mandatory = $true, ValueFromPipeline = $true)] [string] $InputString, [Parameter(Position = 1, Mandatory = $false)] [switch] $ByteArray ) PROCESS { try { # Replace and pad $InputString = $InputString.Replace("-","+").Replace("_","/") $InputString = $InputString.PadRight($InputString.Length + (4 - ($InputString.Length % 4)), "=").Replace("====", "") if ($ByteArray.IsPresent) { [Convert]::FromBase64String($InputString) } else { [System.Text.Encoding]::UTF8.GetString([Convert]::FromBase64String($InputString)) } } catch { Write-Error "Unable to decode base64" } } } |