[ietf-dkim] Features that could be reconsidered as part of the bis process
Murray S. Kucherawy
msk at sendmail.com
Wed May 20 14:42:45 PDT 2009
On Wed, 20 May 2009, Steve Atkins wrote:
> Another use case is to use l= to sign a text part of an email, but not
> to sign an attachment. In that case I can obviously replace the
> attachment with my own content, but depending on the details of the
> email structure I may well be able to replace the text section as
> rendered to the user as well.
Indeed, Outlook will opt to render an HTML part over a text part whenever
given the choice. Thus, if you sign only the text/plain portion of a
message and an attacker appends a text/html part, the unsigned HTML
version will be rendered even if completely different from the text/plain
part, and DKIM would give that a thumbs-up.
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