(Android™) Verify a JWT Created by the Amazon Cognito Service

Demonstrates how to verify a JWT created by the Amazon Cognito Service.

Chilkat Android™ Downloads Android™ Java Libraries Android C/C++ Libraries

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

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

    // The public keys for this example are at https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json
    // Let's get them:

    CkHttp http = new CkHttp();
    CkStringBuilder sbJsonKeys = new CkStringBuilder();
    boolean success = http.QuickGetSb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json",sbJsonKeys);
    if (success == false) {
        Log.i(TAG, http.lastErrorText());
        return;
        }

    CkJsonObject jsonKeys = new CkJsonObject();
    jsonKeys.LoadSb(sbJsonKeys);
    jsonKeys.put_EmitCompact(false);
    Log.i(TAG, jsonKeys.emit());

    // Here are the keys:

    // {
    //   "keys": [
    //     {
    //       "alg": "RS256",
    //       "e": "AQAB",
    //       "kid": "1A/L5Fsb2EsEwxy5E0cmCMS1BnMe6Jl6NXiMig4iNwU=",
    //       "kty": "RSA",
    //       "n": "y0w7BJrIJYi ... jKG27z2P3OKw",
    //       "use": "sig"
    //     },
    //     {
    //       "alg": "RS256",
    //       "e": "AQAB",
    //       "kid": "mos6VTJnvDwurY3ghJg6IAPUq+dMwl6CL/iThzJOkzg=",
    //       "kty": "RSA",
    //       "n": "qbIEH-7tg6yrT ... 3Fj94ooTd0w",
    //       "use": "sig"
    //     }
    //   ]
    // }

    // Try the 1st key.
    CkJsonObject jsonKey1 = jsonKeys.ObjectOf("keys[0]");
    if (jsonKeys.get_LastMethodSuccess() == false) {
        Log.i(TAG, "Did not get the 1st JSON public key.");
        return;
        }

    CkPublicKey pubKey1 = new CkPublicKey();
    success = pubKey1.LoadFromString(jsonKey1.emit());
    if (success == false) {
        Log.i(TAG, pubKey1.lastErrorText());
        return;
        }

    Log.i(TAG, "Success");

    CkJwt jwt = new CkJwt();

    // I did not include the an actual AWS Cognito token here because our test sample used customer-provided data..
    String token = "eyJ..asXg";

    // First verify the signature.
    boolean sigVerified = jwt.VerifyJwtPk(token,pubKey1);
    Log.i(TAG, "verified: " + String.valueOf(sigVerified));

    // Let's see if the time constraints, if any, are valid.
    // The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
    // If the current system time is before the "nbf" time, or after the "exp" time,
    // then IsTimeValid will return false/0.
    // Also, we'll allow a leeway of 60 seconds to account for any clock skew.
    // Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
    int leeway = 60;
    boolean bTimeValid = jwt.IsTimeValid(token,leeway);
    Log.i(TAG, "time constraints valid: " + String.valueOf(bTimeValid));

    // Now let's recover the original claims JSON (the payload).
    String payload = jwt.getPayload(token);
    // The payload will likely be in compact form:
    Log.i(TAG, payload);

    // We can format for human viewing by loading it into Chilkat's JSON object
    // and emit.
    CkJsonObject json = new CkJsonObject();
    success = json.Load(payload);
    json.put_EmitCompact(false);
    Log.i(TAG, json.emit());

    // We can recover the original JOSE header in the same way:
    String joseHeader = jwt.getHeader(token);
    // The payload will likely be in compact form:
    Log.i(TAG, joseHeader);

    // We can format for human viewing by loading it into Chilkat's JSON object
    // and emit.
    success = json.Load(joseHeader);
    json.put_EmitCompact(false);
    Log.i(TAG, json.emit());

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}