index.js

'use strict';

const aws = require('aws-sdk');

const defaultSleep = function (ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
};

// These are used for test purposes only
let defaultResponseURL;
let waiter;
let sleep = defaultSleep;
let random = Math.random;
let maxAttempts = 10;

/**
 * Upload a CloudFormation response object to S3.
 *
 * @param {object} event the Lambda event payload received by the handler function
 * @param {object} context the Lambda context received by the handler function
 * @param {string} responseStatus the response status, either 'SUCCESS' or 'FAILED'
 * @param {string} physicalResourceId CloudFormation physical resource ID
 * @param {object} [responseData] arbitrary response data object
 * @param {string} [reason] reason for failure, if any, to convey to the user
 * @returns {Promise} Promise that is resolved on success, or rejected on connection error or HTTP error response
 */
let report = function (event, context, responseStatus, physicalResourceId, responseData, reason) {
  return new Promise((resolve, reject) => {
    const https = require('https');
    const { URL } = require('url');

    var responseBody = JSON.stringify({
      Status: responseStatus,
      Reason: reason,
      PhysicalResourceId: physicalResourceId || context.logStreamName,
      StackId: event.StackId,
      RequestId: event.RequestId,
      LogicalResourceId: event.LogicalResourceId,
      Data: responseData
    });

    const parsedUrl = new URL(event.ResponseURL || defaultResponseURL);
    const options = {
      hostname: parsedUrl.hostname,
      port: 443,
      path: parsedUrl.pathname + parsedUrl.search,
      method: 'PUT',
      headers: {
        'Content-Type': '',
        'Content-Length': responseBody.length
      }
    };

    https.request(options)
      .on('error', reject)
      .on('response', res => {
        res.resume();
        if (res.statusCode >= 400) {
          reject(new Error(`Server returned error ${res.statusCode}: ${res.statusMessage}`));
        } else {
          resolve();
        }
      })
      .end(responseBody, 'utf8');
  });
};

/**
 * Requests a public certificate from AWS Certificate Manager, using DNS validation.
 * The hosted zone ID must refer to a **public** Route53-managed DNS zone that is authoritative
 * for the suffix of the certificate's Common Name (CN).  For example, if the CN is
 * `*.example.com`, the hosted zone ID must point to a Route 53 zone authoritative
 * for `example.com`.
 *
 * @param {string} requestId the CloudFormation request ID
 * @param {string} domainName the Common Name (CN) field for the requested certificate
 * @param {string} hostedZoneId the Route53 Hosted Zone ID
 * @param {map} tags Tags to add to the requested certificate
 * @returns {string} Validated certificate ARN
 */
const requestCertificate = async function (requestId, domainName, subjectAlternativeNames, hostedZoneId, region, route53Endpoint, tags) {
  const crypto = require('crypto');
  const acm = new aws.ACM({ region });
  const route53 = route53Endpoint ? new aws.Route53({ endpoint: route53Endpoint }) : new aws.Route53();
  if (waiter) {
    // Used by the test suite, since waiters aren't mockable yet
    route53.waitFor = acm.waitFor = waiter;
  }

  console.log(`Requesting certificate for ${domainName}`);

  const reqCertResponse = await acm.requestCertificate({
    DomainName: domainName,
    SubjectAlternativeNames: subjectAlternativeNames,
    IdempotencyToken: crypto.createHash('sha256').update(requestId).digest('hex').substr(0, 32),
    ValidationMethod: 'DNS'
  }).promise();

  console.log(`Certificate ARN: ${reqCertResponse.CertificateArn}`);


  if (!!tags) {
    const result = Array.from(Object.entries(tags)).map(([Key, Value]) => ({ Key, Value }))

    await acm.addTagsToCertificate({
      CertificateArn: reqCertResponse.CertificateArn,
      Tags: result,
    }).promise();
  }

  console.log('Waiting for ACM to provide DNS records for validation...');

  let records;
  for (let attempt = 0; attempt < maxAttempts && !records; attempt++) {
    const { Certificate } = await acm.describeCertificate({
      CertificateArn: reqCertResponse.CertificateArn
    }).promise();
    const options = Certificate.DomainValidationOptions || [];
    if (options.length > 0 && options[0].ResourceRecord) {
      // some alternative names will produce the same validation record
      // as the main domain (eg. example.com + *.example.com)
      // filtering duplicates to avoid errors with adding the same record
      // to the route53 zone twice
      const unique = options
        .map((val) => val.ResourceRecord)
        .reduce((acc, cur) => {
          acc[cur.Name] = cur;
          return acc;
        }, {});
      records = Object.keys(unique).sort().map(key => unique[key]);
    } else {
      // Exponential backoff with jitter based on 200ms base
      // component of backoff fixed to ensure minimum total wait time on
      // slow targets.
      const base = Math.pow(2, attempt);
      await sleep(random() * base * 50 + base * 150);
    }
  }
  if (!records) {
    throw new Error(`Response from describeCertificate did not contain DomainValidationOptions after ${maxAttempts} attempts.`)
  }


  console.log(`Upserting ${records.length} DNS records into zone ${hostedZoneId}:`);

  const changeBatch = await route53.changeResourceRecordSets({
    ChangeBatch: {
      Changes: records.map((record) => {
        console.log(`${record.Name} ${record.Type} ${record.Value}`)
        return {
          Action: 'UPSERT',
          ResourceRecordSet: {
            Name: record.Name,
            Type: record.Type,
            TTL: 60,
            ResourceRecords: [{
              Value: record.Value
            }]
          }
        };
      }),
    },
    HostedZoneId: hostedZoneId
  }).promise();

  console.log('Waiting for DNS records to commit...');
  await route53.waitFor('resourceRecordSetsChanged', {
    // Wait up to 5 minutes
    $waiter: {
      delay: 30,
      maxAttempts: 10
    },
    Id: changeBatch.ChangeInfo.Id
  }).promise();

  console.log('Waiting for validation...');
  await acm.waitFor('certificateValidated', {
    // Wait up to 9 minutes and 30 seconds
    $waiter: {
      delay: 30,
      maxAttempts: 19
    },
    CertificateArn: reqCertResponse.CertificateArn
  }).promise();

  return reqCertResponse.CertificateArn;
};

/**
 * Deletes a certificate from AWS Certificate Manager (ACM) by its ARN.
 * If the certificate does not exist, the function will return normally.
 *
 * @param {string} arn The certificate ARN
 */
const deleteCertificate = async function (arn, region) {
  const acm = new aws.ACM({ region });

  try {
    console.log(`Waiting for certificate ${arn} to become unused`);

    let inUseByResources;
    for (let attempt = 0; attempt < maxAttempts; attempt++) {
      const { Certificate } = await acm.describeCertificate({
        CertificateArn: arn
      }).promise();

      inUseByResources = Certificate.InUseBy || [];

      if (inUseByResources.length) {
        // Exponential backoff with jitter based on 200ms base
        // component of backoff fixed to ensure minimum total wait time on
        // slow targets.
        const base = Math.pow(2, attempt);
        await sleep(random() * base * 50 + base * 150);
      } else {
        break
      }
    }

    if (inUseByResources.length) {
      throw new Error(`Response from describeCertificate did not contain an empty InUseBy list after ${maxAttempts} attempts.`)
    }

    console.log(`Deleting certificate ${arn}`);

    await acm.deleteCertificate({
      CertificateArn: arn
    }).promise();
  } catch (err) {
    if (err.name !== 'ResourceNotFoundException') {
      throw err;
    }
  }
};

/**
 * Main handler, invoked by Lambda
 */
exports.certificateRequestHandler = async function (event, context) {
  var responseData = {};
  var physicalResourceId;
  var certificateArn;

  try {
    switch (event.RequestType) {
      case 'Create':
      case 'Update':
        certificateArn = await requestCertificate(
          event.RequestId,
          event.ResourceProperties.DomainName,
          event.ResourceProperties.SubjectAlternativeNames,
          event.ResourceProperties.HostedZoneId,
          event.ResourceProperties.Region,
          event.ResourceProperties.Route53Endpoint,
          event.ResourceProperties.Tags,
        );
        responseData.Arn = physicalResourceId = certificateArn;
        break;
      case 'Delete':
        physicalResourceId = event.PhysicalResourceId;
        // If the resource didn't create correctly, the physical resource ID won't be the
        // certificate ARN, so don't try to delete it in that case.
        if (physicalResourceId.startsWith('arn:')) {
          await deleteCertificate(physicalResourceId, event.ResourceProperties.Region);
        }
        break;
      default:
        throw new Error(`Unsupported request type ${event.RequestType}`);
    }

    console.log(`Uploading SUCCESS response to S3...`);
    await report(event, context, 'SUCCESS', physicalResourceId, responseData);
    console.log('Done.');
  } catch (err) {
    console.log(`Caught error ${err}. Uploading FAILED message to S3.`);
    await report(event, context, 'FAILED', physicalResourceId, null, err.message);
  }
};

/**
 * @private
 */
exports.withReporter = function (reporter) {
  report = reporter;
};

/**
 * @private
 */
exports.withDefaultResponseURL = function (url) {
  defaultResponseURL = url;
};

/**
 * @private
 */
exports.withWaiter = function (w) {
  waiter = w;
};

/**
 * @private
 */
exports.resetWaiter = function () {
  waiter = undefined;
};

/**
 * @private
 */
exports.withSleep = function (s) {
  sleep = s;
}

/**
 * @private
 */
exports.resetSleep = function () {
  sleep = defaultSleep;
}

/**
 * @private
 */
exports.withRandom = function (r) {
  random = r;
}

/**
 * @private
 */
exports.resetRandom = function () {
  random = Math.random;
}

/**
 * @private
 */
exports.withMaxAttempts = function (ma) {
  maxAttempts = ma;
}

/**
 * @private
 */
exports.resetMaxAttempts = function () {
  maxAttempts = 10;
}