OWASP AppSec Research 2013

The Web's principal security policy is the Same-Origin Policy (SOP), whichenforces origin-based isolation of mutually distrusting Web applications. Sincethe early days, the SOP was repeatedly undermined with variants of the DNSRebinding attack, allowing untrusted script code to gain illegitimate access toprotected network resources.  To counter these attacks, the browser vendorsintroduced countermeasures, such as DNS Pinning, to mitigate the attack. Inthis talk, we present a novel DNS Rebinding attack method leveraging the HTML5Application Cache. Our attack allows reliable DNS Rebinding attacks,circumventing all currently deployed browser-based defense measures.Furthermore, we analyze the fundamental problem which allows DNS Rebinding towork in the first place: The SOP's main purpose is to ensure securityboundaries of Web servers. However, the Web servers themselves are onlyindirectly involved in the corresponding security decision. Instead, the SOPrelies on information obtained from the domain name system, which is notnecessarily controlled by the Web server's owners. This mismatch is exploitedby DNS Rebinding. Based on this insight, we propose a light-weight extension tothe SOP which takes Web server provided information into account. Wesuccessfully implemented our extended SOP for the Chromium Web browser andreport on our implementation's interoperability and security properties.