Functions/Get-JsonWebTokenSignature.ps1
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function Get-JsonWebTokenSignature { <# .SYNOPSIS Gets the JSON Web Token signature from the passed JWT. ..DESCRIPTION Deserializes a JSON Web Token payload to a byte array by default. Optionally the original base 64 URL encoded signature can be returned via the AsEncodedString parameter. .PARAMETER JsonWebToken Specifies the The JSON Web Token to get the signature from. .PARAMETER AsEncodedString Returns the signature as a base 64 URL encoded string as opposed to the decoded value as a byte array. .EXAMPLE $jwt = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWV9.VG6H-orYnMLknmJajHx1HW9SftqCWeqE3TQ1UArx3Mk" $jwt | Get-JsonWebTokenSignature Returns the signature from the passed JWT as a byte array. .EXAMPLE $jwt = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWV9.VG6H-orYnMLknmJajHx1HW9SftqCWeqE3TQ1UArx3Mk" Get-JsonWebTokenSignature -JsonWebToken $jwt -AsEncodedString Returns the encoded signature from the passed JWT. .INPUTS System.String A String is received by the JsonWebToken parameter. .OUTPUTS System.Byte or System.String .LINK New-JsonWebToken Test-JsonWebToken Get-JsonWebTokenHeader Get-JsonWebTokenPayload #> [CmdletBinding()] [Alias('gjwtsig')] [OutputType([System.String], [System.Byte[]])] Param ( [Parameter(Mandatory = $true, ValueFromPipeline = $true, Position = 0)] [ValidateLength(16, 131072)][Alias("JWT", "Token")][String]$JsonWebToken, [Parameter(Mandatory = $false, ValueFromPipeline = $false, ValueFromPipelineByPropertyName = $false, Position = 1)][Alias("AsIs")][switch]$AsEncodedString ) BEGIN { $decodeExceptionMessage = "Unable to decode JWT." $ArgumentException = New-Object -TypeName ArgumentException -ArgumentList $decodeExceptionMessage } PROCESS { [bool]$isValidJwt = Test-JwtStructure -JsonWebToken $JsonWebToken -VerifySignaturePresent if (-not($isValidJwt)) { Write-Error -Exception $ArgumentException -Category InvalidArgument -ErrorAction Stop } $jwtSignature = $JsonWebToken.Split(".")[2] if ($PSBoundParameters.ContainsKey("AsEncodedString")) { return $jwtSignature } else { $jwtSignatureByteArray = ConvertFrom-Base64UrlEncodedString -InputString $jwtSignature -AsBytes return $jwtSignatureByteArray } } } |