Computer Security

  • c. 38039
  • Introduction to Sandboxing, DAC and MAC
  • Linux Capabilities

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In these talks we're going to discuss some of the standard Access Control methods used to restrict access and strengthen sandboxing in modern Operating Systems. The goal is to understand the pros and cons of Discretionary Access Control (DAC), Mandatory Access Control (MAC) and Capability-based Access Control.

The talks can also be considered a practical introduction to Unix-style permissions, SELinux and Linux capabilities. You'll learn how to use it and configure it. Also, the slides collect many examples taken from real policies (especially from Linux and Android).

In the third talk we'll discuss how Android isolates applications from each other and from the system. We'll also introduce you to our research product SEApp (a modification to the Android Open Source Project to extend MAC to apps).

Sandboxing, DAC and MAC

  • Slides
  • Program
    • Introduction to Access control techniques, DAC and MAC
    • Unix-style permissions (managing users and groups, set-UID-root, sticky bit)
    • LSM and SELinux (kernel policy language, MLS, m4 macros, command line tools)

Linux Capabilities

  • Slides
  • Program
    • Introduction to Linux Capabilities
    • Thread capabilities vs File capabilities
    • Capability sets
    • What happens during an execve
    • Set-user-ID-root programs with capabilities
    • Textual representation, capset, get, and decoding
    • Capability-aware vs Capability-dumb programs

Isolation of apps in Android

  • Slides
  • Program
    • Application Sandboxing in Android: DAC and MAC
      • SEAndroid Context Files
      • Android Permissions and introduction to the Binder IPC
    • SEApp: Bringing Mandatory Access Control to Android Apps
      • Motivation and Idea
      • Policy language and Policy Module Constraints
      • Install time and Runtime support
      • Demo using a Pixel 2 XL / Pixel 3


  • Talk 1: 03/05/2022
  • Talk 2: 10/05/2022
  • Talk 3: 17/05/2022 - Matthew Rossi