Verifying a DKIM TXT Record and Key Length

After reading the Wired story last week about Zachary Harris discovering a widespread vulnerability related to the use of weak cryptographic DKIM keys (less than 1024 bits) by companies like Google, eBay, Yahoo, Twitter and PayPal, and the subsequent CERT warning (VU#268267), I decided to write a quick tool to check DKIM TXT records and determine their key length:

DKIM Key Checker

This tool grabs your DKIM DNS TXT record and uses OpenSSL to parse the contained public key to determine its key length.