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IIS Short Name Scanner - 2012-2023 & Still Giving...

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I recommended everyone to try @bitquark's new tool in Go before trying this old tool: https://github.com/bitquark/shortscan

The latest version of scanner for IIS short file name (8.3) disclosure vulnerability by using the tilde (~) character. This issue has been discovered in 2010 but has been evolved a few times since.

This is an old tool and the code is a spaghetti, but it is capable to tackle even the latest IIS (IIS 10 on Windows Server 2022 at the time of writing this)! It has recently been updated, so it can support sending custom HTTP methods without reflection hacks in Java. However, some awesome researchers have tried to reimplement this tool using other technologies such as in Go, and when they become mature, they probably work better than this.

Description

Microsoft IIS contains a flaw that may lead to an unauthorized information disclosure. The issue is triggered during the parsing of a request that contains a tilde character (~). This may allow a remote attacker to gain access to file and folder name information.

This scanner was moved from https://code.google.com/p/iis-shortname-scanner-poc/ to GitHub for better support.

Original research file: http://soroush.secproject.com/downloadable/microsoft_iis_tilde_character_vulnerability_feature.pdf

It is possible to detect short names of files and directories which have an 8.3 equivalent in Windows by using some vectors in several versions of Microsoft IIS. For instance, it is possible to detect all short-names of ".aspx" files as they have 4 letters in their extensions.

Note: new techniques have been introduced to the latest versions of this scanner, and it can now scan IIS10 when it is vulnerable.

It is not easy to find the original file or folder names based on the short names. However, the following methods are recommended as examples:

Installation

The recent version has been compiled by using Open JDK 18 (the old jar files for other JDKs have been removed but can be found in the Git history).

You will need to download files in the /release directory to use this old application!

You can also compile this application yourself. Please submit any issues in GitHub for further investigation.

Usage

Command line options

USAGE 1 (To verify if the target is vulnerable with the default config file):

java -jar iis_shortname_scanner.jar [URL]

USAGE 2 (To find 8.3 file names with the default config file):

java -jar iis_shortname_scanner.jar [ShowProgress] [ThreadNumbers] [URL]

USAGE 3 (To verify if the target is vulnerable with a new config file):

java -jar iis_shortname_scanner.jar [URL] [configFile]

USAGE 4 (To find 8.3 file names with a new config file):

java -jar iis_shortname_scanner.jar [ShowProgress] [ThreadNumbers] [URL] [configFile]

USAGE 5 (To scan multiple targets using a linux box):

./multi_targets.sh <scope file> <is_default_https (1=https)>

DETAILS:

 [ShowProgress]: 0= Show final results only - 1= Show final results step by step  - 2= Show Progress
 [ThreadNumbers]: 0= No thread - Integer Number = Number of concurrent threads [be careful about IIS Denial of Service]
 [URL]: A complete URL - starts with http/https protocol
 [configFile]: path to a new config file which is based on config.xml

Examples:

- Example 0 (to see if the target is vulnerable):
 java -jar iis_shortname_scanner.jar http://example.com/folder/

- Example 1 (uses no thread - very slow):
 java -jar iis_shortname_scanner.jar 2 0 http://example.com/folder/new%20folder/

- Example 2 (uses 20 threads - recommended):
 java -jar iis_shortname_scanner.jar 2 20 http://example.com/folder/new%20folder/

- Example 3 (saves output in a text file):
 java -jar iis_shortname_scanner.jar 0 20 http://example.com/folder/new%20folder/ > c:\results.txt

- Example 4 (bypasses IIS basic authentication):
 java -jar iis_shortname_scanner.jar 2 20 http://example.com/folder/AuthNeeded:$I30:$Index_Allocation/

- Example 5 (using a new config file):
 java -jar iis_shortname_scanner.jar 2 20 http://example.com/folder/ newconfig.xml 
 
- Example 6 (scanning multiple targets using a linux box):
 ./multi_targets.sh scope.txt 1

Note 1: Edit config.xml file to change the scanner settings and add additional headers. Note 2: Sometimes it does not work for the first time, and you need to try again.

How Does It Work?

In the following examples, IIS responds with a different message when a file exists:

http://target/folder/valid*~1.*/.aspx
http://target/folder/invalid*~1.*/.aspx

However, different IIS servers may respond differently, and for instance some of them may work with the following or other similar patterns:

http://target/folder/valid*~1.*\.asp
http://target/folder/invalid*~1.*\.asp

Method of sending the request such as GET, POST, OPTIONS, DEBUG, ... is also important.

I believe monitoring the requests by using a proxy is the best way of understating this issue and this scanner.

How To Fix This Issue

Microsoft will not patch this security issue. Their last response is as follows:

Thank you for contacting the Microsoft Security Response Center.  

We appreciate your bringing this to our attention.  Our previous guidance stands: deploy IIS with 8.3 names disabled.

Therefore, it is recommended to deploy IIS with 8.3 names disabled by creating the following registry key on a Windows operating system:

	Key:   HKLM\SYSTEM\CurrentControlSet\Control\FileSystem
	Name:  NtfsDisable8dot3NameCreation 
	Value:        1

Note: The web folder needs to be recreated, as the change to the NtfsDisable8dot3NameCreation registry entry affects only files and directories that are created after the change, so the files that already exist are not affected.

Docker Usage

build the image:

docker build . -t shortname

file mode:

docker run \
  -v $(realpath urls.txt):/app/urls.txt \
  -v $(realpath output_dir):/app/iis_shortname_results \
  shortname -f urls.txt

single mode:

docker run shortname 2 20 http://example.com

overwrite config file:

docker run \
-v $(realpath config.xml):/app/config.xml \
shortname http://example.com

References

Research links:

Website Reference:

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