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.
Likelihood of exploitation
Medium to Low
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:18.104.22.168) Gecko/20070515 Firefox/22.214.171.124 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.
http://capec.mitre.org/data/definitions/93.html - Log Injection-Tampering-Forging