4 research outputs found
Identifying Native Applications with High Assurance
The work described in this paper investigates the problem
of identifying and deterring stealthy malicious processes on
a host. We point out the lack of strong application iden-
tication in main stream operating systems. We solve the
application identication problem by proposing a novel iden-
tication model in which user-level applications are required
to present identication proofs at run time to be authenti-
cated by the kernel using an embedded secret key. The se-
cret key of an application is registered with a trusted kernel
using a key registrar and is used to uniquely authenticate
and authorize the application. We present a protocol for
secure authentication of applications. Additionally, we de-
velop a system call monitoring architecture that uses our
model to verify the identity of applications when making
critical system calls. Our system call monitoring can be
integrated with existing policy specication frameworks to
enforce application-level access rights. We implement and
evaluate a prototype of our monitoring architecture in Linux
as device drivers with nearly no modication of the ker-
nel. The results from our extensive performance evaluation
shows that our prototype incurs low overhead, indicating the
feasibility of our model
Improving the Policy Specification for Practical Access Control Systems
Access control systems play a crucial role in protecting the security of information systems by ensuring that only authorized users are granted access to sensitive resources, and the protection is only as good as the access control policies. For enabling a security administrator to express her desired policy conveniently, it is paramount that a policy specification is expressive, comprehensible, and free of inconsistencies. In this dissertation, we study the policy specifications for three practical access control systems (i.e., obligation systems, firewalls, and Security-Enhanced Linux in Android) and improve their expressiveness, comprehensibility, and consistency. First, we improve the expressiveness of obligation policies for handling different types of obligations. We propose a language for specifying obligations as well as an architecture for handling access control policies with these obligations, by extending XACML (i.e., the de facto standard for specifying access control policies). We also implement our design into a prototype system named ExtXACML to handle various obligations. Second, we improve the comprehensibility of firewall policies enabling administrators to better understand and manage the policies. We introduce the tri-modularized design of firewall policies for elevating them from monolithic to modular. To support legacy firewall policies, we also define a five-step process and present algorithms for converting them into their modularized form. Finally, we improve the consistency of Security-Enhanced Linux in Android (SEAndroid) policies for reducing the attack surface in Android systems. We propose a systematic approach as well as a semiautomatic tool for uncovering three classes of policy misconfigurations. We also analyze SEAndroid policies from four Android versions and seven Android phone vendors, and in all of them we observe examples of potential policy misconfigurations
Improving the Policy Specification for Practical Access Control Systems
Access control systems play a crucial role in protecting the security of information systems by ensuring that only authorized users are granted access to sensitive resources, and the protection is only as good as the access control policies. For enabling a security administrator to express her desired policy conveniently, it is paramount that a policy specification is expressive, comprehensible, and free of inconsistencies. In this dissertation, we study the policy specifications for three practical access control systems (i.e., obligation systems, firewalls, and Security-Enhanced Linux in Android) and improve their expressiveness, comprehensibility, and consistency. First, we improve the expressiveness of obligation policies for handling different types of obligations. We propose a language for specifying obligations as well as an architecture for handling access control policies with these obligations, by extending XACML (i.e., the de facto standard for specifying access control policies). We also implement our design into a prototype system named ExtXACML to handle various obligations. Second, we improve the comprehensibility of firewall policies enabling administrators to better understand and manage the policies. We introduce the tri-modularized design of firewall policies for elevating them from monolithic to modular. To support legacy firewall policies, we also define a five-step process and present algorithms for converting them into their modularized form. Finally, we improve the consistency of Security-Enhanced Linux in Android (SEAndroid) policies for reducing the attack surface in Android systems. We propose a systematic approach as well as a semiautomatic tool for uncovering three classes of policy misconfigurations. We also analyze SEAndroid policies from four Android versions and seven Android phone vendors, and in all of them we observe examples of potential policy misconfigurations