What's in Your Dongle and Bank Account? Mandatory and Discretionary Protection of Android External Resources

To address this challenge, we present in this paper SEACAT, a new security system for fine-grained, flexible protection on external resources. SEACAT supports both MAC and DAC, and integrates their enforcement mechanisms across the Android middleware and the Linux kernel. It extends SEAndroid for specifying policies on external resources, and also hosts a DAC policy base. Both sets of policies are managed under the same policy engine and Access Vector Cache that support policy checks within the security hooks distributed across the framework and the Linux kernel layers, over different channels. This integrated security model was carefully designed to ensure that misconfigured DAC policies will not affect the enforcement of MAC policies, which manufacturers and system administrators can leverage to define their security rules. In the meantime, a policy management service is offered to the ordinary Android users for setting policies that protect the resources provided by the third party. This service translates simple user selections into SELinux-compatible policies in the background. Our implementation is capable of thwarting all known attacks on external resources at a negligible performance cost.