Java

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.

Chilkat2 Java

import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Http;
import com.chilkatsoft.chilkat2.JsonObject;
import com.chilkatsoft.chilkat2.Jwt;
import com.chilkatsoft.chilkat2.PublicKey;
import com.chilkatsoft.chilkat2.StringBuilder;

public class ChilkatExample {

    public static void main(String[] args) {
        boolean success = false;

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

        Http http = new Http();
        StringBuilder sbPubKeys = new StringBuilder();

        try {
            http.quickGetSb("https://www.googleapis.com/oauth2/v3/certs", sbPubKeys);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println(sbPubKeys.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.
        // -------------------------------------------------------------------------------------------
        String token = "eyJhbGciOiJSUzI1NiIsImtpZCI6IjQyZmY5MGQ3ZDM0OGM5NzM4MWE3YzExOWVmMWY1MzI0ZWEzZjViZWIifQ.eyJpc3MiOiJodHRwczovL2FjY291bnRzLmdvb2dsZS5jb20iLCJzdWIiOiIxMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExMTExIiwiaWF0IjoxNjExMTE1MTQzLCJleHAiOjE2MTEyMDE1NDMsImF1ZCI6IjQyOTc1NzExNTE0ODg0OSJ9.pLem5i0bx3M7lJYj7jKv2Nq7c07X5YpZz-x1uM5RniW-v4LsX-lKIVvOq2x3-WoPqkzLXJfP0kG0dx1uD2q1NfFQK60YwKH4FnFtB6INnUP1dRVpP9_pTTKyAE28I3s5Tay4PbPdrCl7ZLCIJzCfpCW1TiWeVoPjp5HgZKTBHdP_sEkN_yO5dQerQXAkFJkV3kNgF9jI3ayT-KPqOIH6GVoWXjHFDyA2EYgJPEFRo5WSe6XycJ85p5duwT-OoBcb_kJZG9PxYd91eHlPCzp8vGxzIb2dVROCBxyM8e8W0cd9v15hfmpg9R-eG9vCM5y63ZLChZLFeHFx0Pd7hvAqfKg";

        Jwt jwt = new Jwt();
        String header = jwt.getHeader(token);

        System.out.println(header);

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

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

        JsonObject json = new JsonObject();
        json.load(header);
        String kid = json.stringOf("kid");

        System.out.println("kid = " + kid);

        JsonObject jsonPubKeys = new JsonObject();
        jsonPubKeys.loadSb(sbPubKeys);

        JsonObject jsonKey = jsonPubKeys.findRecord("keys", "kid", kid, true);
        if (jsonKey == null) {
            System.out.println("Did not find a matching public key based on the kid.");
            return;
        }

        System.out.println(jsonKey.emit());

        // Load the matching public key into a Chilkat public key object.
        PublicKey pubKey = new PublicKey();
        try {
            pubKey.loadFromString(jsonKey.emit());
            success = true;
        } catch (ChilkatException e) {
            success = false;
        }
        jsonKey.close();
        if (!success) {
            System.out.println(pubKey.getLastErrorText());
            return;
        }

        // ----------------------------------------------------------------------------------------
        // 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
    }
}