Wiki source code of Engine_XalanJ

Last modified by Nicolas Gregoire on 2012/01/31 17:35
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1 {{toc/}}
2
3 = Introduction =
4
5 [[Xalan-J>>http://xml.apache.org/xalan-j/||rel="__blank" title="Xalan-J Home Page"]] is a Java based XSLT engine by the Apache Project.
6
7 = Supported version =
8
9 1.0
10
11 = Command line =
12
13 $> java org.apache.xalan.xslt.Process -in foo.xml -xsl foo.xsl
14
15 __Note__ : xml-apis.jar, xercesImpl.jar and xalan*.jar must be in the $CLASSPATH
16
17 = Identification strings =
18
19 |=xsl:vendor-url|http:~/~/xml.apache.org/xalan-j
20 |=xsl:vendor|Apache Software Foundation
21 |=xsl:version|1.0
22
23 = Special features =
24
25 * Java properties disclosure
26 * Java environment disclosure
27 * Java code execution
28 * OS command execution
29 * File creation
30 * JDBC connectivity
31
32 = Java properties disclosure =
33
34 The xsl:system-property() standard function can be called with non standard arguments, mapped to Java properties. In this example, the name of the Java properties is stored in a separate XML file ([[properties.xml>>attach:properties.xml]]). The XSLT code will, for each property, display its name and its value.
35
36 |=Namespace|=Function|=PoC|=Sample output
37 |http:~/~/www.w3.org/1999/XSL/Transform|system-property()|[[xalanj-java-properties.xsl>>attach:xalanj-java-properties.xsl]]|[[xalanj-java-properties-output.txt>>attach:xalanj-java-properties-output.txt]]
38
39 = Java environment disclosure =
40
41 The checkEnvironment() extension function (documented [[here>>http://xml.apache.org/xalan-j/faq.html#faq-N10064||rel="__blank"]]) will display some information about the execution context (including available packages, paths, versions, ...).
42
43 |=Namespace|=Extension function|=PoC|=Sample output
44 |http:~/~/xml.apache.org/xalan|checkEnvironment()|[[xalanj-checkenv.xsl>>attach:xalanj-checkenv.xsl]]|[[xalanj-checkenv-output.txt>>attach:xalanj-checkenv-output.txt]]
45
46 = Java code execution =
47
48 == Basic Java calls ==
49
50 The attached code will display the current date using a newly created "java.util.Date" object. This should be enough to demonstrate Java code execution.
51
52 |=Namespace|=Extension function|=PoC|=Sample output
53 |http:~/~/xml.apache.org/xalan/java/java.util.Date|new()|[[xalanj-java-date.xsl>>attach:xalanj-java-date.xsl]]|Current date:
54 Wed Jan 11 22:45:07 CET 2012
55
56 == Executing arbitrary classes ==
57
58 -- It is afaik not possible to get a pure Java reverse-shell, as we can't create threads :-( --
59
60 {{warning}}
61 TODO : javapayload => loading arbitrary byte code (aka classes) via reflection
62 $> java javapayload.builder.Builder Template XalanJ.xsl bind-jsh-4444.xsl BindTCP 127.0.0.1 4444 - - JSh
63 List supported payloads !
64 Check supported versions of Xalan !
65 {{/warning}}
66
67 = OS command execution =
68
69 Once Java code execution is possible, it is trivial to execute arbitrary OS commands using the java.lang.Runtime class.
70
71 == Command without output ==
72
73 The attached PoC will not read the output of the executed command (because loops are hard in XSLT). But this is not a problem if a reverse-shell have already been started, isn't it ;-)
74
75 |=Namespace|=Extension functions|=PoC
76 |http:~/~/xml.apache.org/xalan/java|split(), getRuntime(), exec() and toString()|[[xalanj-reverse-bash.xsl>>attach:xalanj-reverse-bash.xsl]]
77
78 __Note__ : as arrays are not a native type in XSLT, we create one in Java via split() before passing it as an argument to [[exec(String[] cmdarray)>>http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/Runtime.html#exec(java.lang.String[])||rel="__blank"]].
79
80 == Reading stdout ==
81
82 As the output have an unknown number of lines, we must use a __loop__ construct like "while" ... which is not available in XSLT. This limitation is due to the functional programming paradigm but can be circumvented using templates and recursion. This way, we can also __update__ some variables, but the syntax is awful and error prone.
83
84 It's far more efficient to 1) write loops using non-standard elements like <loop:while> and <loop:update> 2) convert them in stylesheets using only templates and recursion. This conversion can be done with a tool like the [[XSLT Loop Compiler>>http://www2.informatik.hu-berlin.de/~~obecker/XSLT/loop-compiler/||rel="__blank"]] (which is itself in XSLT).
85
86 The following PoC will fetch some commands from a XML file, execute them (with bash or cmd.exe depending on the detected OS), read the standard output and display it. The file with a "lxsl" extension uses the non-standard <loop:*> elements and is far more readable than the "xsl" one.
87
88 |=Using non standards elements|=Using recursion and templates|=Commands to execute|=Output
89 |[[xalanj-reading-stdout.lxsl>>attach:xalanj-reading-stdout.lxsl]]|[[xalanj-reading-stdout.xsl>>attach:xalanj-reading-stdout.xsl]]|[[unix_commands.xml>>attach:unix_commands.xml]]|[[xalanj-reading-stdout.txt>>attach:xalanj-reading-stdout.txt]]
90
91 It is of course possible to include commands for multiples OS in one file and to execute only the relevant ones.
92
93 = File creation =
94
95 The "write" extension element allows to create files on the engine side. The content written to the file must be valid UTF-8 (so plain ASCII works too). Existing files can be overwritten.
96
97 |=Namespace|=Extension element|=Parameter|=PoC
98 |http:~/~/xml.apache.org/xalan/redirect|write|file|[[xalanj-write.xsl>>attach:xalanj-write.xsl]]
99
100 = JDBC connectivity =
101
102 It is possible to use XSLT to connect to any database having a corresponding installed JDBC driver.
103
104 == Simple connection ==
105
106 The [[xalanj-jdbc-query.xsl>>attach:xalanj-jdbc-query.xsl]] PoC simply connects to a local MySQL database using some hard-coded credentials, executes a query and displays the result.
107
108 |=Namespace|=Extension function|=PoC
109 |org.apache.xalan.lib.sql.XConnection|new(), query() and close()|[[xalanj-jdbc-query.xsl>>attach:xalanj-jdbc-query.xsl]]
110
111 == Credentials brute-forcing ==
112
113 The [[xalanj-jdbc-bruteforce.xsl>>attach:xalanj-jdbc-bruteforce.xsl]] file will read some tuples (JDBC driver, database URL, username, passsword) from a XML file ([[xalanj-jdbc-bruteforce.xml>>attach:xalanj-jdbc-bruteforce.xml]]) and try to login with each one, effectively brute-forcing credentials from the engine side (usually on the backend ;-).
114
115
116 Here's the output when launched from the CLI :
117
118 ##$> java org.apache.xalan.xslt.Process -in xalanj-jdbc-bruteforce.xml -xsl xalanj-jdbc-bruteforce.xsl 2> /dev/null
119 Username : [root] / Password : [] :
120 Username : [root] / Password : [uberpasswd] :
121 Username : [root] / Password : [cnam] : OK !!
122 Username : [pma] / Password : [pma] : ##
123
124 = Anti XEE =
125
126 DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
127 builderFactory.setExpandEntityReferences(false); <<<<==[Here]==<<<<
128 DocumentBuilder builder = builderFactory.newDocumentBuilder();
129 DOMSource xmlSource = new DOMSource(builder.parse(new ByteArrayInputStream(myXmlString.getBytes(~)~)~));
130
131
132 By default (cf. Xalan-j [[documentation>>http://xml.apache.org/xalan-j/apidocs/javax/xml/parsers/DocumentBuilderFactory.html#setExpandEntityReferences(boolean)]]), this value is set to True.