There is interesting thing with event logging on Windows. The only
security aspect of it is event log record tampering and performance
degradation, but it may become sensitive is some 3rd party software is
used for automated event log analysis.
Log tampering is a big concern, since it is trivial to change the
meaning of logs without touching the .evt files themselves.
However, there are other security concerns, at least when it comes to
the event viewer. It downloads DLLs from remote systems when viewing
remote logs, parses the message resources and uses them to determine the
meaning of remote logs. Anyone played with fuzzing the PE file format?
The problem is a kind of "Format string" vulnerability where
user-supplied input is used for event log record. For ReportEvent()
function %1, %2, etc have a special meaning and are replaced with
corresponding string from lpStrings.
It looks more like a variable replacement (like $0 $1 ... in bash shell)
than a format string issue to me.
And it seems indeed to be a relevant information disclosure bug.
I have studied the FormatMessage() interface in my attempt to interpret
event logs[1], but I had no idea that the "%n" elements were replaced
recursively. That could be significant, since format strings *can* be
included as a modifier for those elements. See [2] for more details.
3APA3A, have you tried to see if elements like "%n!FORMAT!" used
recursively will invoke the wsprintf()-like behavior??
cheers,
tim
[1] http://projects.sentinelchicken.org/grokevt/
[2] http://msdn.microsoft.com/library/en-us/debug/base/formatmessage.asp
_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.grok.org.uk/full-disclosure-charter.html
Hosted and sponsored by Secunia - http://secunia.com/
