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Re: Remote file inclusion by office applications
From: Tim Brown <tmb () 65535 com>
Date: Fri, 14 Dec 2012 01:31:59 +0000

On Friday 14 Dec 2012 00:24:33 Kurt Seifried wrote:
On 12/13/2012 11:53 AM, Daniel Kahn Gillmor wrote:
On 12/13/2012 11:44 AM, Kurt Seifried wrote:
I'm kind of leaning towards classifying this as a security issue
since I expected there is some way to disable it or at least tell
it to prompt me when a document tries to go get an external data
source (e.g. "this document contains external data, the URLs/file
paths it is trying to  reference are: [list of locations]") but
apparently there is no way to disable/have this prompt (at least
that I can find in LibreOffice)?

I think your assessment is correct.  I've just now made an ODT file
that libreoffice uses to not only hit the network for a PNG (denial
of service attacks, remote exploitation of other flaws in libpng or
in LO itself, virus scanner bypass, etc), but one that will include
and render ~/.ssh/id_rsa as a text/plain document.  This seems like
it could be done against any local privileged file.

For local file inclusion, libreoffice at leasts prompts me with:

----------- This document contains one or more links to external
data.

Would you like to change the document, and update all links to get
the most recent data?

[Yes] [No] -----------

but it doesn't tell me what those documents are. And given the UI
history of people clicking through popups they don't understand,
i'm not convinced that this popup is going to do anything to
prevent remote disclosure (it even defaults to "Yes").  When i say
"no" on the prompt, it goes out and fetches networked URLs anyway,
so i assume this prompt is supposed to just refer to local
"external data".

--dkg

Confirmed.  By comparison both Okular and Calligra Office ignore the remote and 
local file references (without even prompting).

Tim
-- 
Tim Brown
<mailto:tmb () 65535 com>

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