This is an Attack. To view all attacks, please see the Attack Category page.

Description

Repudiation is the act of refuse authoring of something that happened. A repudiation attack happens when an application or system do not adopt controls to properly track and log users actions, thus permitting malicious manipulation or forging the identification of new actions. This attack can be used to change the authoring information of actions executed by a malicious user in order to log wrong data to log files. Its usage can be extended to general data manipulation in name of others, in a similar manner as spoofing mails messages. If this attack takes place, the data stored on log files can be considered invalid or misleading.

Examples

Consider a web application that makes access control and authorization based on SESSIONID, but register user actions based on user parameter defined on Cookie header, as follows:

 POST http://someserver/Upload_file.jsp HTTP/1.1
 Host: tequila:8443
 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.8.1.4)   
 Gecko/20070515 Firefox/2.0.0.4
 Accept:
 text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
 Accept-Language: en-us,en;q=0.5
 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
 Keep-Alive: 300
 Connection: keep-alive
 Referer: http://someserver/uploads.jsp
 Cookie: JSESSIONID=EE3BD1E764CD6EED280426128201131C;  
 user=leonardo
 Content-Type: multipart/form-data; boundary=--------------------------- 
 263152394310685
 Content-Length: 321

And the log file is composed by:

Date, Time, Source IP, Source port, Request, User

Once user information is acquired from user parameter on HTTP header, a malicious user could make use of a local proxy (eg:paros) and change it by a known or unknown username.