Functions/Convert-JwkToPem.ps1
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function Convert-JwkToPem { <# .SYNOPSIS Converts a JWK public key to a PEM. .DESCRIPTION Converts a JWK (JSON Web Key) to formatted PEM (Privacy Enhanced Mail) as well as an unformatted Base64 encoded public key. .PARAMETER Uri Specifies the Uniform Resource Identifier (URI) containing the JSON Web Keys to convert to PEM format. .EXAMPLE $jwkUri = "https://app.mycompany.com/common/discovery/keys.json" Convert-JwkToPem -Uri $jwkUri Converts the JWKs in the JWK set found in https://app.mycompany.com/common/discovery/keys.json to PEM format. .OUTPUTS PSJsonWebToken.PemFromJwkResult An object containing the JWK ID, PEM and unformatted Base64 public key. . .LINK https://tools.ietf.org/html/rfc7517 https://www.rfc-editor.org/rfc/rfc7468 #> [CmdletBinding()] [Alias('cjwk')] [OutputType([PSJsonWebToken.PemFromJwkResult])] Param ( [Parameter(Mandatory = $true, ParameterSetName = "URI", Position = 1)][Alias('OidcUri', 'JwkUri')][System.Uri]$Uri ) PROCESS { $jsonWebKeys = @() try { $jsonWebKeys += (Get-JwkCollection -Uri $Uri -ErrorAction Stop) } catch { Write-Error -Exception $_.Exception -ErrorAction Stop } $SerializationException = [SerializationException]::new("Unable to deserialize JSON Web Key.") foreach ($jwk in $jsonWebKeys) { try { $rsaParams = [RSAParameters]::new() $rsaParams.Exponent = $jwk.e | ConvertFrom-Base64UrlEncodedString -AsBytes -ErrorAction Stop $rsaParams.Modulus = $jwk.n | ConvertFrom-Base64UrlEncodedString -AsBytes -ErrorAction Stop $rsaCryptoSp = [RSACryptoServiceProvider]::new() $rsaCryptoSp.ImportParameters($rsaParams) [byte[]]$publicKeyBytes = $rsaCryptoSp.ExportSubjectPublicKeyInfo() [string]$publicKeyUnformatted = ConvertTo-Base64UrlEncodedString -Bytes $publicKeyBytes -ErrorAction Stop [string]$publicKeyPem = $rsaCryptoSp.ExportSubjectPublicKeyInfoPem() $rsaCryptoSp.Dispose() $result = [PSJsonWebToken.PemFromJwkResult]::new() $result.JwkIdentifier = $jwk.kid $result.Pem = $publicKeyPem $result.UnformattedCertificate = $publicKeyUnformatted Write-Output -InputObject $result } catch { Write-Error -Exception $SerializationException -Category InvalidData -ErrorAction Stop } } } } |