From pdt@jackhammer.org Mon Mar  8 21:34:46 2004
From: Paul Tinsley <pdt@jackhammer.org>
To: full-disclosure@lists.netsys.com
Date: Mon, 08 Mar 2004 20:03:49 -0600
Subject: [Full-Disclosure] ASP script using OpenTextFile

Need some help from those out there versed in windows.  I am auditing an 
ASP based (VBScript) application which uses OpenTextFile as follows:

Set f = fso.OpenTextFile(sLeadingPath + paramPageToRender + ".xsl", 
ForReading)

I have been able to ../../../../ all over the place, but it only allows 
me to pick up files ending with .xsl.  I would like to print the 
contents of a non .xsl file to prove that not checking paths properly is 
a large issue.  But I have had no luck making it ignore the .xsl I have 
tried ../../foo.txt%00 ../../foo.txt%0a ../../foo.txt%0d.  But none of 
these seem to be working for me, does anyone know of a good way to end 
the file where I want and have it ignore the .xsl tacked on the end of 
the filename to be opened?  Any help is greatly appreciated.

Thanks,
   Paul Tinsley

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From lists2@onryou.com Mon Mar  8 22:17:21 2004
From: Cael Abal <lists2@onryou.com>
To: Paul Tinsley <pdt@jackhammer.org>
Cc: full-disclosure@lists.netsys.com
Date: Mon, 08 Mar 2004 21:58:57 -0500
Subject: Re: [Full-Disclosure] ASP script using OpenTextFile

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Paul Tinsley wrote:
> Need some help from those out there versed in windows.  I am auditing
> an ASP based (VBScript) application which uses OpenTextFile as
> follows:
>
> Set f = fso.OpenTextFile(sLeadingPath + paramPageToRender + ".xsl",
> ForReading)
>
> I have been able to ../../../../ all over the place, but it only
> allows me to pick up files ending with .xsl.  I would like to print
> the contents of a non .xsl file to prove that not checking paths
> properly is a large issue.  But I have had no luck making it ignore
> the .xsl I have tried ../../foo.txt%00 ../../foo.txt%0a
> ../../foo.txt%0d.  But none of these seem to be working for me, does
> anyone know of a good way to end the file where I want and have it
> ignore the .xsl tacked on the end of the filename to be opened?  Any
> help is greatly appreciated.

Hi Paul,

You're right to raise concerns about this sort of code.  Consider this
example:

- ---snip---

sLeadingPath = "C:\"
paramPageToRender = "passwords.txt" + Chr(0)

set fso = CreateObject("Scripting.FileSystemObject")
set f = fso.OpenTextFile (sLeadingPath + paramPageToRender + ".xsl", 1)

WScript.echo (f.ReadAll)

- ---snip---

You had the right idea, you only needed to figure out how VBS represents
\0.  As you know, because strings are terminated with the null
character, the final string concatenation performed within
OpenTextFile() is disregarded.

Cheers,

Cael

(Heh, fear my leet VBS skills.)
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_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html