WebSVN 2.0 - Cross-Site Scripting / File Handling / Code Execution





WebSVN <= 2.0 Multiple Vulnerabilities
October 20, 2008
Vendor 	: Tim Armes
URL 	: http://websvn.tigris.org
Version 	: WebSVN <= 2.0
Risk 	: Multiple Vulnerabilities

WebSVN is an online SVN repository viewer. The description taken from 
the project website reads "WebSVN offers a view onto your subversion 
repositories that's been designed to reflect the Subversion methodology. 
You can view the log of any file or directory and see a list of all the 
files changed, added or deleted in any given revision. You can also view 
the differences between 2 versions of a file so as to see exactly what 
was changed in a particular revision." Unfortunately there are a several 
issues in WebSVN may allow for an attacker to conduct cross site 
scripting attacks, and create arbitrary files. There is also a code 
execution issue in the v1 branch. 

Cross Site Scripting
There is a Cross Site Scripting issue in WebSVN due to the unsafe usage 
of the PHP_SELF server variable within the getParameterisedSelfUrl() 


A url like the one above would display a JavaScript alert window 
containing the cookie data of any set cookies for the domain. 

File Handling Issues:
There are some file handling issues in the RSS functionality used by 
WebSVN. The issue is caused by the following bit of code taken from 
rss.php, and allows arbitrary file operations to be executed. 

// Cachename reflecting full path to and rev for rssfeed. Must end with xml to work
$cachename = strtr(getFullURL($listurl), ":/\\?", "____");
$cachename = $locwebsvnreal.DIRECTORY_SEPARATOR.'cache'.DIRECTORY_SEPARATOR.

As we can see from the above bit of code, the "rev" request variable is 
never properly sanitized. in order to exploit this issue an attacker 
would have to first send a valid "rev" parameter to rss.php, and then 
traverse the known location. 


So, if the "rev" parameter was initially set to the number one, then to 
create a file called test.php in the root web directory a request like 
the one above would have to be made. 

PHP Code Execution:
There is an arbitrary php code execution issue in the 1.* branch of 
WebSVN due to the unsafe use of preg_replace evaluation when parsing 
anchor tags and the like. 

// Replace any usernames
$ret = preg_replace("#\[:nom:([^\]]*)\]#e",
	            "username(0, trim(\"\\1\"))",

The above code can be found within the create_anchors() function located 
in the utils.inc file. Since this function uses double quotes, instead 
of single quotes in the evaluated code, php code execution is possible 
via complex variable evaluation. 


Even though this is not the current version, there is still many 1.* 
installations being used as seen in the search below. 


Unfortunately the developers have been mostly unresponsive to any 
correspondence. The original bug report filed over a month ago can be 
found at the link below. 


Even before this bug report was filed, any attempts made to contact the developers were unsuccessful.

James Bercegay of the GulfTech Security Research Team

# milw0rm.com [2008-10-23]