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Headers are manually created whenever programmatically sending email messages To clarify this a little, in case anyone isn't familiar, to send an email message
by jcnnghm 16y ago
Headers are manually created whenever programmatically sending email messages
To clarify this a little, in case anyone isn't familiar, to send an email message programmatically, you basically just send a string with some headers and body content to the email server. Here are what the headers look like:
Date: Sat, 13 Jun 2009 06:53:06 -0400
From: Mail Delivery Subsystem <MAILER-DAEMON>
Message-Id: <200906131053.n5DAr2Nv025105@jclinux>
To: <root@jclinux>
To change the sender, all you'd need to do is change the from line. For example:
From: Steve Jobs <sjobs@apple.com>
A default sendmail implementation will deliver that message all day. Email headers should never be used for authentication.
- robinduckett 16y agoThat was my point. When I read in his article that he wasn't requiring a password to post, I thought I'd see if he was telling the truth, turns out he was.
- adamsmith 16y agoBut most major domains use domain keys / DKIM. http://en.wikipedia.org/wiki/DKIM http://en.wikipedia.org/wiki/DKIM As far as I understand it, you can't fake being an SMTP server sending mail from such a domain because their emails get signed with a private key whose matching public key is published by DNS.
- geocar 16y agoThere are several ways to defeat DKIM here: • If you can break DNS, you can get an NXDOMAIN reply, making recipients think there aren't any domainkeys • If the domainkey private key is small, you can factor it. There's an article on HN's frontpage right now about this. • If the server uses domainkeys, but it doesn't specifically verify the From: header, an attacker can still forge a message if they share a popular mail provider with their target. I don't know if this is still practical. • Stupidity. DKIM is difficult to test, and as a security measure it would need to be tested. An autoreponse confirmation would be immune to all of these attacks and would be trivial to implement correctly.