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RE: Re: [Full-disclosure] URI handling woes in Acrobat Reader, Netscape, Miranda, Skype
- To: "Thierry Zoller" <Thierry@xxxxxxxxx>, "Juergen Schmidt" <ju@xxxxxxxxx>, <bugtraq@xxxxxxxxxxxxxxxxx>, <full-disclosure@xxxxxxxxxxxxxxxxx>
- Subject: RE: Re: [Full-disclosure] URI handling woes in Acrobat Reader, Netscape, Miranda, Skype
- From: "Roger A. Grimes" <roger@xxxxxxxxxxxxxx>
- Date: Sat, 6 Oct 2007 21:30:20 -0400
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- Thread-topic: Re: [Full-disclosure] URI handling woes in Acrobat Reader, Netscape, Miranda, Skype
I appreciate everyone's replies. Thanks for the replies and the
explanations. I'm not a Microsoft developer, I'm just a security
consultant. I didn't understand the nature of the central issue, at
first, but now I do.
*Roger A. Grimes, InfoWorld, Security Columnist
*CPA, CISSP, CISA, MCSE: Security (2000/2003), CEH, yada...yada...
*email: roger_grimes@xxxxxxxxxxxxx or roger@xxxxxxxxxxxxxx
*Author of Windows Vista Security: Securing Vista Against Malicious
From: Thierry Zoller [mailto:Thierry@xxxxxxxxx]
Sent: Saturday, October 06, 2007 12:13 PM
To: Juergen Schmidt; bugtraq@xxxxxxxxxxxxxxxxx;
Subject: Re: [Full-disclosure] URI handling woes in Acrobat Reader,
Netscape, Miranda, Skype
RAG> The applications in question are accepting abitrary input and not
Please define "correctly" in case of an Uri handler. I am not aware of
special attack vectors or injections that I should be filtering in case
of mailto: calls, are there any? If yes, where are they documented and
where can I find them ? As a developer I have no control over what
Windows does with this handler, I have to trust it.
Are all Application developers now required to work around obvious bugs
in the way Windows handles the mailto: handler ?
What you call for is in essence - mitigation, yes it's fine to mitigate
a "vulnerability". But shouldn't we be concentrating on finding and
fixing the root cause instead of trying to mitigate the problem in
(hundrets) of third-party applications ?
RAG> How is that a Microsoft or Windows problem?
How is that _not_ a Windows Problem ?
RAG> Don't get me wrong, I want to protect end-users as much as the next
RAG> person (as does MS), but if it is the application not validating
RAG> correctly, could there not be hundreds of potential characters and
RAG> strings that cause input validation problems in particular
RAG> circumstances, which will vary according to the application?
We are speaking of the mailto: handler here that _seems_ to be broken
POST IE7 installation. (Again IMHO)
Could you explain me why POST Ie7:
executes notepad trying to open calc
Now the surprise :
OFFICE (Winword) opens, SHELLS the mailto handler BUT replaces "%" with
"%25" and " with %22 and surprise it does NOT execute calc but your mail
Winword mitigated the problem/vulnerability.
Try it, open Winword, add hyperlink with
click on it, and check process explorer to see the result winword
replaced the % prior to shelling mailto. Now this is some serious
I think some persons were aware of the problem but couldn't get the
responsible parties to fix it, becuase of arguments like yours. This is
a assumption, not a fact. I have not been there and heard that...
RAG> If Microsoft scrubs out every potential malicious character, it's
RAG> bound to break lots of legitimate applications.
What genuine application uses this  way to call a mailto: handler ?
RAG> At what point should Microsoft scrub URIs so that it hands off only
RAG> "legitmate" characters "most of the time"? How could Microsoft
RAG> determine ahead of time what is and isn't legitimate characters to
RAG> pass to applications they don't own?
It's not that they should decide what and what to pass or not to pass
on, the problem in the example Juergen sent is - what they pass
INTERNALY not to third party applications.
RAG> If they block
RAG> characters that affect certain applications, it might cause
RAG> problems in other applications that have no problem with the
character(s) in question?
RAG> What is the solution? The easy answer is to block the % character
RAG> in this particular instance...but that's just a whack-a-mole fix.
The Solution might be :
- Determine the root cause
- Determine the attack vectors
- Determine whether it's wise to fix it at the root or try to mitigate
RAG> I'm asking, with genuine interest and a listening ear, what is the
RAG> best long term solution you envision, to solve the larger problem?
Certainly it's not mitigating through hundrets of third party
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