On 10/11/10 3:05 PM, Wietse Venema wrote: > Charles Lindsey: >>> When the bad guy sends mail with (multiple) forged headers, the >>> best they can get is that naive mail programs render their forged >>> header with an indication that THE BAD GUY'S DKIM SIGNATURE VERIFIED. >>> >>> Sending forged headers with bad guy's DKIM signatures is not an >>> interesting attack on DKIM. >> On the contrary, it is an exceedingly interesting attack. > If you believe that sending mail with a valid bad guy signature is > an interesting attack on DKIM, then that implies that you're willing > to believe mail that is signed by arbitrary strangers. That is a > problem that DKIM is not designed to solve. Use of a pre-pended From could be for servi...@big-bank.com, where the valid signature could be for some...@big-ips.com. It seems important to keep this from being an attack vector, as bad actors might send themselves their messages to replay them in a deceptive fashion. Its not hard to imagine this becoming a problem. It also seems unlikely to have messages from a large provider blocked when a few of their messages are used in an attack that they did not directly issue.
-Doug _______________________________________________ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
