Abusing Bleeding Edge Web Standards for AppSec Glory presented at Defcon 2016

by Ryan Lester, Bryant Zadegan,

Summary : Through cooperation between browser vendors and standards bodies in the recent past, numerous standards have been created to enforce stronger client-side control for web applications. As web appsec practitioners continue to shift from mitigating vulnerabilities to implementing proactive controls, each new standard adds another layer of defense for attack patterns previously accepted as risks. With the most basic controls complete, attention is shifting toward mitigating more complex threats. As a result of the drive to control for these threats client-side, standards such as SubResource Integrity (SRI), Content Security Policy (CSP), and HTTP Public Key Pinning (HPKP) carry larger implementation risks than others such as HTTP Strict Transport Security (HSTS). Builders supporting legacy applications actively make trade-offs between implementing the latest standards versus accepting risks simply because of the increased risks newer web standards pose. In this talk, we'll strictly explore the risks posed by SRI, CSP, and HPKP; demonstrate effective mitigation strategies and compromises which may make these standards more accessible to builders and defenders supporting legacy applications; as well as examine emergent properties of standards such as HPKP to cover previously unforeseen scenarios. As a bonus for the breakers, we'll explore and demonstrate exploitations of the emergent risks in these more volatile standards, to include multiple vulnerabilities uncovered quite literally during our research for this talk (which will hopefully be mitigated by d-day).