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openssldkim

How to verify DKIM signature from an e-mail with openssl?

I've set up opendkim for my postfix and now all outgoing mails have DKIM-Signature heading. What I want to do is to verify manually, withoug DNS and external utilities, preferably with openssl only, that messages are getting correct signature. So as input data I have:

  • DKIM-Signature header of an e-mail
  • DKIM Selector, DKIM Domain
  • DKIM Private Key
  • DKIM Public signature if form of a record that I need to put to DNS

The question is how to decrypt and/or verify DKIM-Signature with DKIM Public signature using some CLI utility like openssl?

Solution

  • To verify directly from email's source

    • Download email, usually an .eml file

    • Install python

    • pip install dkimpy

    • dkimverify < email_file.eml

      Alternatively you can

      • dkimverify
      • paste source
      • Ctrl+D

    source

    Other methods