index.js

'use strict';

const CONFIG = require('./config.js');
const ALGO_MAP = {
  'SHA512withRSA': 'RSA-SHA512'
};

var request = require('request');
var _ = require('underscore');
var async = require('async');
var pemtools = require('pemtools');

function _fetchPublicKey(callback) {
  var options = {
    url: CONFIG.PUBLIC_KEY_URL,
    method: 'GET',
    json: true
  };

  request(options, function (err, response, body) {
    if (err) {
      return callback(err);
    }

    if (!body || body.length === 0 || !body[0].key, !body[0].keyType) {
      return callback('Failed to read public key from key server.');
    }

    return callback(null, body[0]);
  });
}

function _getDecodedPayloadFromProfile(profile, callback) {
  if (!profile.payload) {
    return callback('Error: Profile does not contain payload');
  }

  try {
    var payload = JSON.parse(new Buffer(profile.payload, 'base64').toString());
    return callback(null, payload);
  } catch (e) {
    return callback(e);
  }
};

function _deconstructProfile(profile, callback) {
  try {
    var result = {};

    var _profile = JSON.parse(JSON.stringify(profile));

    delete(_profile.signature);
    delete(_profile.signatureAlgorithm);
    delete(_profile.payload);

    result.profile = _profile;
    result.signature = profile.signature;
    result.signatureAlgorithm = profile.signatureAlgorithm;
    result.payload = profile.payload;

    _getDecodedPayloadFromProfile(profile, function (err, decodedPayload) {
      if (err) {
        return callback(err);
      }

      result.decodedPayload = decodedPayload;

      return callback(null, result);
    });
  } catch (e) {
    return callback(e);
  }
};

function _verifyPayload(profile, callback) {
  _deconstructProfile(profile, function (err, truecallerProfile) {
    if (err) {
      return callback(err);
    }

    if (truecallerProfile.decodedPayload.hasOwnProperty('requestTime')) {
      delete truecallerProfile.decodedPayload.requestTime;
    }

    if (_.isEqual(truecallerProfile.profile, truecallerProfile.decodedPayload)) {
      return callback(null, true);
    } else {
      return callback(null, false);
    }
  });
};

function _verifySignature(profile, callback) {
  async.waterfall([
    function (cb) {
      _fetchPublicKey(function (err, result) {
        if (err) {
          return cb(err);
        }

        return cb(null, result.keyType, result.key);
      });
    },

    function (keyType, key, cb) {
      _deconstructProfile(profile, function (err, result) {
        if (err) {
          return cb(err);
        }

        return cb(null, keyType, key, result.payload, result.signature, result.signatureAlgorithm);
      });
    },

    function (keyType, key, payload, signature, signatureAlgorithm, cb) {
      var _key = Buffer.from(pemtools(Buffer.from(key, 'base64'), 'PUBLIC KEY').pem);
      var _payload = Buffer.from(payload);
      var _signature = Buffer.from(signature, 'base64');
      var _signatureAlgorithm = ALGO_MAP[signatureAlgorithm];

      var verifier = crypto.createVerify(_signatureAlgorithm);
      verifier.update(_payload);

      var signatureVerificationResult = verifier.verify(_key, _signature);

      return cb(null, signatureVerificationResult);
    }
  ], function (err, result) {
    if (err) {
      return callback(err);
    }

    return callback(null, result);
  });
};

function _verifyProfile(profile, callback) {
  async.parallel([
    function (cb) {
      _verifyPayload(profile, function (err, result) {
        if (err) {
          return cb(err);
        }

        return cb(null, result);
      });
    },

    function (cb) {
      _verifySignature(profile, function (err, result) {
        if (err) {
          return cb(err);
        }

        return cb(null, result);
      });
    }
  ], function (err, results) {
    if (err) {
      return callback(err);
    }

    if (results[0] === true && results[1] === true) {
      return callback(null, true);
    } else {
      return callback(null, false);
    }
  });
};

exports = module.exports = {
  verifyProfile: _verifyProfile
};