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Re: [dkim-ops] FW: how can use the DKIM the function

2011-05-17 19:41:03
On Tue, May 17, 2011 at 5:40 PM, John R. Levine <johnl(_at_)iecc(_dot_)com> 
wrote:
How can:

log_write(0, LOG_MAIN, (char *)logmsg)

be used to arbitrarily inject code? I understand the concept, but
having % in the logmsg with no parameters to feed it seems harmless to
me.

It took random junk off the stack which presumably overflowed a buffer.

I found it because one of my users (someone you know)

yes, a certain Canadian.

was complaining that
all of the mail he sent to a site that uses Exim was disappearing.  I got
them to look at the logs and found they were logging the DKIM signatures and
then barfing.

See http://bugs.exim.org/show_bug.cgi?id=1106

yep, I saw that.

Passing an unchecked string as a printf format is an ancient unix bug.

Ah, so vargs type stuff. Still, I'll have to run it through a debugger
myself to understand.  I would think one would have a loop of some
sort. I would of thought if there were no args it would just end.

(oh, I see Hector has some input too)

-- 
Jeff Macdonald
Ayer, MA

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