Xbase++

Verify a Google JWT Using Google's Public Key

See more Google APIs Examples

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.

Xbase++

LOCAL nSuccess
LOCAL oHttp
LOCAL oSbPubKeys
LOCAL cToken
LOCAL oJwt
LOCAL cHeader
LOCAL oJson
LOCAL cKid
LOCAL oJsonPubKeys
LOCAL oJsonKey
LOCAL oPubKey

nSuccess := 0

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

oHttp := CreateObject("Chilkat.Http")
oSbPubKeys := CreateObject("Chilkat.StringBuilder")

nSuccess := oHttp:QuickGetSb("https://www.googleapis.com/oauth2/v3/certs", oSbPubKeys)
IF (nSuccess == 0)
    ? oHttp:LastErrorText
    oHttp:destroy()
    oSbPubKeys:destroy()
    RETURN
ENDIF

? oSbPubKeys:GetAsString()

//  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.
//  -------------------------------------------------------------------------------------------
cToken := "eyJhbGciOiJSUzI1NiIsImtpZCI6IjQyZmY5MGQ3ZDM0OGM5NzM4MWE3YzExOWVmMWY1MzI0ZWEzZjViZWIifQ.eyJpc3MiOiJodHRwczovL2FjY291bnRzLmdvb2dsZS5jb20iLCJzdWIiOiIxMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExIiwiaWF0IjoxNjExMTE1MTQzLCJleHAiOjE2MTEyMDE1NDMsImF1ZCI6IjQyOTc1NzExNTE0ODg0OSJ9.pLem5i0bx3M7lJYj7jKv2Nq7c07X5YpZz-x1uM5RniW-v4LsX-lKIVvOq2x3-WoPqkzLXJfP0kG0dx1uD2q1NfFQK60YwKH4FnFtB6INnUP1dRVpP9_pTTKyAE28I3s5Tay4PbPdrCl7ZLCIJzCfpCW1TiWeVoPjp5HgZKTBHdP_sEkN_yO5dQerQXAkFJkV3kNgF9jI3ayT-KPqOIH6GVoWXjHFDyA2EYgJPEFRo5WSe6XycJ85p5duwT-OoBcb_kJZG9PxYd91eHlPCzp8vGxzIb2dVROCBxyM8e8W0cd9v15hfmpg9R-eG9vCM5y63ZLChZLFeHFx0Pd7hvAqfKg"

oJwt := CreateObject("Chilkat.Jwt")
cHeader := oJwt:GetHeader(cToken)

? cHeader

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

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

oJson := CreateObject("Chilkat.JsonObject")
oJson:Load(cHeader)
cKid := oJson:StringOf("kid")

? "kid = " + cKid

oJsonPubKeys := CreateObject("Chilkat.JsonObject")
oJsonPubKeys:LoadSb(oSbPubKeys)

oJsonKey := oJsonPubKeys:FindRecord("keys", "kid", cKid, 1)
IF (oJsonPubKeys:LastMethodSuccess == 0)
    ? "Did not find a matching public key based on the kid."
    oHttp:destroy()
    oSbPubKeys:destroy()
    oJwt:destroy()
    oJson:destroy()
    oJsonPubKeys:destroy()
    RETURN
ENDIF

? oJsonKey:Emit()

//  Load the matching public key into a Chilkat public key object.
oPubKey := CreateObject("Chilkat.PublicKey")
nSuccess := oPubKey:LoadFromString(oJsonKey:Emit())
oJsonKey:destroy()
IF (nSuccess == 0)
    ? oPubKey:LastErrorText
    oHttp:destroy()
    oSbPubKeys:destroy()
    oJwt:destroy()
    oJson:destroy()
    oJsonPubKeys:destroy()
    oPubKey:destroy()
    RETURN
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

oHttp:destroy()
oSbPubKeys:destroy()
oJwt:destroy()
oJson:destroy()
oJsonPubKeys:destroy()
oPubKey:destroy()