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Verify a Google JWT Using Google's Public Key

Demonstrates how to verify a JWT that was signed using Google's RSA private key.
This example verifies the RSA signature. It also does the following:
Checks to see if the time constraints ("nbf" and "exp") are valid.
Recovers the original JOSE header.
Recovers the original claims JSON.
Chilkat AutoIt Downloads

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Local $bSuccess = False

; This example assumes the Chilkat API to have been previously unlocked.
; See Global Unlock Sample for sample code.

$oHttp = ObjCreate("Chilkat.Http")
$oSbPubKeys = ObjCreate("Chilkat.StringBuilder")

$bSuccess = $oHttp.QuickGetSb("https://www.googleapis.com/oauth2/v3/certs",$oSbPubKeys)
If ($bSuccess = False) Then
    ConsoleWrite($oHttp.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite($oSbPubKeys.GetAsString() & @CRLF)

; Here are the keys:

; {
;   "keys": [
;     {
;       "e": "AQAB",
;       "n": "4bAT6C6EeX8Dspje3FrAXw-nnhNk04e1RmNa4kjc0CHf6Pk7ryARlwA-6YilyPABqQfYHx60s8oSnxvUVprFfQ2-Q8aAZO7bPKSxnoGlcKERL2oLNA4Msvc89N9Y5ycThZUplf_QC19e6jyYXN6Nz-UnJSCLrtQY8tVhhVRs61j4A2N_p-enAi-r704Qi1-v-DKV4eVRkClKViploo8NyjUaT9L4vbBssPCjyimJzsWnEe1fED5c4LnHeArYzA_FEn3JJotqDIz9t2VnvZNTMhizHEX4VnORlEWMEfR8n4CEHQx7PcQUOmfqyw08gWeXQl1-uTjtIGaE-sRIv9u_vQ",
;       "kty": "RSA",
;       "use": "sig",
;       "alg": "RS256",
;       "kid": "2af90e87be140c20038898a6efa11283dab6031d"
;     },
;     {
;       "n": "nzGsrziOYrMVYMpvUZOwkKNiPWcOPTYRYlDSdRW4UpAHdWPbPlyqaaphYhoMB5DXrVxI3bdvm7DOlo-sHNnulmAFQa-7TsQMxrZCvVdAbyXGID9DZYEqf8mkCV1Ohv7WY5lDUqlybIk1OSHdK7-1et0QS8nn-5LojGg8FK4ssLf3mV1APpujl27D1bDhyRb1MGumXYElwlUms7F9p9OcSp5pTevXCLmXs9MJJk4o9E1zzPpQ9Ko0lH9l_UqFpA7vwQhnw0nbh73rXOX2TUDCUqL4ThKU5Z9Pd-eZCEOatKe0mJTpQ00XGACBME_6ojCdfNIJr84Y_IpGKvkAEksn9w",
;       "use": "sig",
;       "kid": "87bbe0815b064e6d449cac999f0e50e72a3e4374",
;       "e": "AQAB",
;       "alg": "RS256",
;       "kty": "RSA"
;     }
;   ]
; }

; -------------------------------------------------------------------------------------------
; Replace this with your actual token.
; This sample token contains a kid that does not match any of the above Google public keys.
; -------------------------------------------------------------------------------------------
Local $sToken = "eyJhbGciOiJSUzI1NiIsImtpZCI6IjQyZmY5MGQ3ZDM0OGM5NzM4MWE3YzExOWVmMWY1MzI0ZWEzZjViZWIifQ.eyJpc3MiOiJodHRwczovL2FjY291bnRzLmdvb2dsZS5jb20iLCJzdWIiOiIxMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExIiwiaWF0IjoxNjExMTE1MTQzLCJleHAiOjE2MTEyMDE1NDMsImF1ZCI6IjQyOTc1NzExNTE0ODg0OSJ9.pLem5i0bx3M7lJYj7jKv2Nq7c07X5YpZz-x1uM5RniW-v4LsX-lKIVvOq2x3-WoPqkzLXJfP0kG0dx1uD2q1NfFQK60YwKH4FnFtB6INnUP1dRVpP9_pTTKyAE28I3s5Tay4PbPdrCl7ZLCIJzCfpCW1TiWeVoPjp5HgZKTBHdP_sEkN_yO5dQerQXAkFJkV3kNgF9jI3ayT-KPqOIH6GVoWXjHFDyA2EYgJPEFRo5WSe6XycJ85p5duwT-OoBcb_kJZG9PxYd91eHlPCzp8vGxzIb2dVROCBxyM8e8W0cd9v15hfmpg9R-eG9vCM5y63ZLChZLFeHFx0Pd7hvAqfKg"

$oJwt = ObjCreate("Chilkat.Jwt")
Local $sHeader = $oJwt.GetHeader($sToken)

ConsoleWrite($sHeader & @CRLF)

; Sample header:
; {"alg":"RS256","kid":"87bbe0815b064e6d449cac999f0e50e72a3e4374"}

; Load the public key matching the "kid" into a Chilkat public key object, then verify..

$oJson = ObjCreate("Chilkat.JsonObject")
$oJson.Load($sHeader)
Local $sKid = $oJson.StringOf("kid")

ConsoleWrite("kid = " & $sKid & @CRLF)

$oJsonPubKeys = ObjCreate("Chilkat.JsonObject")
$oJsonPubKeys.LoadSb($oSbPubKeys)

Local $oJsonKey = $oJsonPubKeys.FindRecord("keys","kid",$sKid,True)
If ($oJsonPubKeys.LastMethodSuccess = False) Then
    ConsoleWrite("Did not find a matching public key based on the kid." & @CRLF)
    Exit
EndIf

ConsoleWrite($oJsonKey.Emit() & @CRLF)

; Load the matching public key into a Chilkat public key object.
$oPubKey = ObjCreate("Chilkat.PublicKey")
$bSuccess = $oPubKey.LoadFromString($oJsonKey.Emit())

If ($bSuccess = False) Then
    ConsoleWrite($oPubKey.LastErrorText & @CRLF)
    Exit
EndIf

; ----------------------------------------------------------------------------------------
; Now we can validate the JWT using Google's public key as shown in this example:
; (Except we use the public key obtained as shown above instead of a public key loaded from a PEM file.
; 
; See Verify JWT Using an RSA Public Key