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Validate a Google ID Token

Demonstrates how to verify the signature of a Google id token.
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Local $bSuccess = False

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

$oHttp = ObjCreate("Chilkat.Http")

; First get the public key we'll be needing..
Local $sJwkStr = $oHttp.QuickGetStr("https://www.googleapis.com/oauth2/v3/certs")
If ($oHttp.LastMethodSuccess = False) Then
    ConsoleWrite($oHttp.LastErrorText & @CRLF)
    Exit
EndIf

; We have the following:

;     {
;       "keys": [
; 	{
; 	  "kid": "e8732db06287515556213b80acbcfd08cfb302a9",
; 	  "n": "4RIrO30287Wsq3gqXCMkUYMVAeI3H8...w2mbMNEBQ",
; 	  "kty": "RSA",
; 	  "e": "AQAB",
; 	  "alg": "RS256",
; 	  "use": "sig"
; 	},
; 	{
; 	  "kid": "8462a71da4f6d611fc0fecf0fc4ba9c37d65e6cd",
; 	  "e": "AQAB",
; 	  "n": "xT_ngLZNmT5GBtJZeTB...Ft4gK0eoFi0d3l8bcw",
; 	  "alg": "RS256",
; 	  "use": "sig",
; 	  "kty": "RSA"
; 	}
;       ]
;     }

$oJson = ObjCreate("Chilkat.JsonObject")
$bSuccess = $oJson.Load($sJwkStr)

; -------------------------------------------------

; Load the following..

;  {
;   "access_token": "ya29.a0...0f",
;   "expires_in": 3599,
;   "scope": "openid https://www.googleapis.com/auth/userinfo.email",
;   "token_type": "Bearer",
;   "id_token": "eyJhb...o5nQ"
; }

$oJsonToken = ObjCreate("Chilkat.JsonObject")
$bSuccess = $oJsonToken.LoadFile("qa_data/tokens/google_sample_id_token.json")
If ($bSuccess = False) Then
    ConsoleWrite("Failed to load the JSON file..." & @CRLF)
    Exit
EndIf

; Get the id_token;
$oSbIdToken = ObjCreate("Chilkat.StringBuilder")
$bSuccess = $oSbIdToken.Append($oJsonToken.StringOf("id_token"))

; Get the signature in base64url format.
; The header + payload remains in sbIdToken.
Local $sig_b64Url = $oSbIdToken.GetAfterFinal(".",True)
Local $sHeaderPlusPayload = $oSbIdToken.GetAsString()

ConsoleWrite($sig_b64Url & @CRLF)
ConsoleWrite($sHeaderPlusPayload & @CRLF)

; ---------------------------------------------

; Try validating with each cert's public key.
; Hopefully one will be the key that verifies.

$oRsa = ObjCreate("Chilkat.Rsa")
$oRsa.EncodingMode = "base64url"

$oJsonKey = ObjCreate("Chilkat.JsonObject")
$oPubKey = ObjCreate("Chilkat.PublicKey")

Local $iNumKeys = $oJson.SizeOfArray("keys")
Local $i = 0
While $i < $iNumKeys
    $oJson.I = $i

    $oJson.ObjectOf2("keys[i]",$oJsonKey)

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

    ConsoleWrite($i & @CRLF)
    ConsoleWrite($oPubKey.GetPem(True) & @CRLF)

    $bSuccess = $oRsa.UsePublicKey($oPubKey)

Local $bVerified = $oRsa.VerifyStringENC($sHeaderPlusPayload,"sha256",$sig_b64Url)
    ConsoleWrite("bVerified = " & $bVerified & @CRLF)

    $i = $i + 1
Wend

; The output is:

; 0
; -----BEGIN RSA PUBLIC KEY-----
; MIIBCgKCAQEA4RIrO30287Wsq3gqXCMkUYMVAeI3H8LVE6IXR1krdFeGnZLiGUPw
; cbkeVpXf3lmJdsStOg+jijces2DZCfPyIBiQuLYfxxmAZE6ErJ0QJFg1stwli2Pz
; 9ncYhFoqi8pXr7kEzEJBTzX4thuw56ydbGsshSEznPXoerCJOc7UI2+n0wFCWQ4Y
; LHbh/PrWt4vdadyUUUW/QpQHXQLdD8q/Qwqdj0O9zlJE7R6Elw2E9EqnHyIGu1hm
; LxhqrTru1M18SUhONYbVskV/BCEdVKs//X96849HorWQDCAgVMWfGsdMVq55FAdJ
; 680N5UmQDRynIZ4+PeNGN4S9iw2mbMNEBQIDAQAB
; -----END RSA PUBLIC KEY-----
; 
; bVerified = True
; 1
; -----BEGIN RSA PUBLIC KEY-----
; MIIBCgKCAQEAxT/ngLZNmT5GBdkLtJZjNeTB+8B5yWgrq/e5eMZ1hrZhcmLK+dSn
; IkpOPV8/OekV67EnQ7I4II2rcNJnHGrGKZziXO3XN2gtUHE+mBJC99oULSbX/QwB
; Kz7gC/IBPq9EuxTt6Oq6fPkVQ9DbRIgWJSEGBF/KRaNl3kyAlIZfpY7XgHyJTTv8
; E7yAcYKPR+36gzdl+ps0sDLKzUuAtZNq8llK0u80z6AtAUIYwWdkEhM9upy6keKI
; TasIxcsO7M6kZPINUSbh6t5VAm8FuqRmxpgg+9c9/GQSGd89InVypoVzWLQ+wOGg
; 5G4H6JqIgtj0TRFt4gK0eoFi2U0d3l8bcwIDAQAB
; -----END RSA PUBLIC KEY-----
; 
; bVerified = False