Function checkParentDomainMatch

src/utils.ts:1160–1190

(address: string, srvHost: string)

 * @returns void
 */
export function checkParentDomainMatch(address: string, srvHost: string): void {
  // Remove trailing dot if exists on either the resolved address or the srv hostname
  const normalizedAddress = address.endsWith('.') ? address.slice(0, address.length - 1) : address;
  const normalizedSrvHost = srvHost.endsWith('.') ? srvHost.slice(0, srvHost.length - 1) : srvHost;

  const allCharacterBeforeFirstDot = /^.*?\./;
  const srvIsLessThanThreeParts = normalizedSrvHost.split('.').length < 3;
  // Remove all characters before first dot
  // Add leading dot back to string so
  //   an srvHostDomain = '.trusted.site'
  //   will not satisfy an addressDomain that endsWith '.fake-trusted.site'
  const addressDomain = `.${normalizedAddress.replace(allCharacterBeforeFirstDot, '')}`;
  let srvHostDomain = srvIsLessThanThreeParts
    ? normalizedSrvHost
    : `.${normalizedSrvHost.replace(allCharacterBeforeFirstDot, '')}`;

  if (!srvHostDomain.startsWith('.')) {
    srvHostDomain = '.' + srvHostDomain;
  }
  if (
    srvIsLessThanThreeParts &&
    normalizedAddress.split('.').length <= normalizedSrvHost.split('.').length
  ) {
    throw new MongoAPIError(
      'Server record does not have at least one more domain level than parent URI'
    );
  }
  if (!addressDomain.endsWith(srvHostDomain)) {
    throw new MongoAPIError('Server record does not share hostname with parent URI');
  }
}

/**
 * Perform a get request that returns status and body.