MQTT AWS Snippet

IoTSnippet.js

import AWS, { CognitoIdentityCredentials } from 'aws-sdk/dist/aws-sdk-react-native';
import { CognitoUserPool } from 'react-native-aws-cognito-js';
import { Client, Message } from 'react-native-paho-mqtt';

import appConfig from '../helpers/appConfig';
import SigV4Utils from '../helpers/SigV4Utils';


class Home extends Component {
  componentDidMount() {
    this.connectIoT();
  }

  componentWillUnmount() {
    this.client.disconnect();
  }

  /**
   *  Creates a MQTT client, grants the user IoT permissions, connects the client
   *  to AWS IoT & subscribes to the user's topic. Parses any messages received
   *  from string to JSON to be handled by handleIoTMessage().
   */
  connectIoT() {
    AWS.config.credentials.get(() => {
      var ioturl = SigV4Utils.getSignedUrl(appConfig.iotEndpoint, appConfig.region, AWS.config.credentials);
      const client = new Client({ uri: ioturl, clientId: 'Some Unqiue ID', storage: AsyncStorage });
      this.client = client;
      client.on('messageReceived', (message) => {
        const jsonResponse = JSON.parse(message.payloadString);
        // console.log(jsonResponse);
        this.handleIoTMessage(jsonResponse);
      });

      client.on('connectionLost', (responseObject) => {
        console.log('CLIENT DC');
        if (responseObject.errorCode !== 0) {
          clearInterval(this.publishInterval);
          console.log('CONNECTIONLOST TRIGGERED:', responseObject.errorMessage);
        }
      });

      var connectOptions = {
        useSSL: true,
        timeout: 30000, // In milliseconds, it turns out
        mqttVersion: 4,
      };

      const IoT = new AWS.Iot();

      var params = {
        policyName: appConfig.policyName,
        principal: AWS.config.credentials.identityId
      };

      IoT.attachPrincipalPolicy(params, (err) => {
        if (err) {
          console.log('ERROR attachPrincipalPolicy: ', err);
        }

        client.connect(connectOptions).then(() => {
          client.subscribe('Some relevant topic');
        })
        .catch((responseObject) => {
          console.log(responseObject);
          if (responseObject.errorCode !== 0) {
            console.log(`CATCH ONCONNECTIONLOSTTRIGGERED: ${responseObject.errorMessage}`);
          }
        });
      });
    });
  }
}







import AWS from 'aws-sdk/dist/aws-sdk-react-native';

export default function SigV4Utils() {}

/**
 *  Used to create signature key for signing the URL.
 *  @param {string} key - User's secretAccessKey stored in AWS.credentials.
 *  @param {string} date - (format: YYYYMMDD).
 *  @param {string} region - Our AWS region (us-east-1).
 *  @param {string} service - The service being used (iotdevicegateway).
*/
SigV4Utils.getSignatureKey = (key, date, region, service) => {
  var kDate = AWS.util.crypto.hmac(`AWS4${key}`, date, 'buffer');
  var kRegion = AWS.util.crypto.hmac(kDate, region, 'buffer');
  var kService = AWS.util.crypto.hmac(kRegion, service, 'buffer');
  var kCredentials = AWS.util.crypto.hmac(kService, 'aws4_request', 'buffer');
  return kCredentials;
};

/**
 *  Used to sign the IoT endpoint URL to establish a MQTT websocket.
 *  @param {string} host - Our AWS IoT endpoint.
 *  @param {string} region - Our AWS region (us-east-1).
 *  @param {object} credentials - Current user's stored AWS.config.credentials object.
*/
SigV4Utils.getSignedUrl = (host, region, credentials) => {
  var datetime = AWS.util.date.iso8601(new Date()).replace(/[:-]|\.\d{3}/g, '');
  var date = datetime.substr(0, 8);

  var method = 'GET';
  var protocol = 'wss';
  var uri = '/mqtt';
  var service = 'iotdevicegateway';
  var algorithm = 'AWS4-HMAC-SHA256';

  var credentialScope = `${date}/${region}/${service}/aws4_request`;
  var canonicalQuerystring = `X-Amz-Algorithm=${algorithm}`;
  var credentialsURI = encodeURIComponent(`${credentials.accessKeyId}/${credentialScope}`);
  canonicalQuerystring += `&X-Amz-Credential=${credentialsURI}`;
  canonicalQuerystring += `&X-Amz-Date=${datetime}`;
  canonicalQuerystring += '&X-Amz-SignedHeaders=host';

  var canonicalHeaders = `host:${host}\n`;
  var payloadHash = AWS.util.crypto.sha256('', 'hex');

  //  Linter throws an error on string concatenation here. I couldn't get a template string to work -MK.
  var canonicalRequest = method + '\n' + uri + '\n' + canonicalQuerystring + '\n' + canonicalHeaders + '\nhost\n' + payloadHash;

  var stringToSign = `${algorithm}\n${datetime}\n${credentialScope}\n${AWS.util.crypto.sha256(canonicalRequest, 'hex')}`;
  var signingKey = SigV4Utils.getSignatureKey(credentials.secretAccessKey, date, region, service);
  var signature = AWS.util.crypto.hmac(signingKey, stringToSign, 'hex');

  canonicalQuerystring += `&X-Amz-Signature=${signature}`;
  if (credentials.sessionToken) {
    canonicalQuerystring += `&X-Amz-Security-Token=${encodeURIComponent(credentials.sessionToken)}`;
  }

  var requestUrl = `${protocol}://${host}${uri}?${canonicalQuerystring}`;
  return requestUrl;
};