[Paper Review] Towards Least Privilege Containers with Cimplifier

Vaibhav Rastogi, Drew Davidson+3 more|arXiv (Cornell University)|Feb 26, 2016

Cloud Computing and Resource Management4 references4 citations

TL;DR

Cimplifier is a tool that automatically partitions monolithic containers into minimal, privilege-separated containers by analyzing system call logs to identify necessary resources, then uses remote process execution to preserve functionality. It reduces container image sizes by 58–95% while processing large containers in under 30 seconds, enforcing least privilege without requiring source code or specific runtimes.

ABSTRACT

Application containers, such as Docker containers, have recently gained popularity as a solution for agile and seamless deployment of applications. These light-weight virtualization environments run applications that are packed together with their resources and configuration information, and thus can be deployed across various software platforms. However, these software ecosystems are not conducive to the true and tried security principles of privilege separation (PS) and principle of least privilege (PLP). We propose algorithms and a tool Cimplifier, which address these concerns in the context of containers. Specifically, given a container our tool partitions them into simpler containers, which are only provided enough resources to perform their functionality. As part our solution, we develop techniques for analyzing resource usage, for performing partitioning, and gluing the containers together to preserve functionality. Our evaluation on real-world containers demonstrates that Cimplifier can preserve the original functionality, leads to reduction in image size of 58-95%, and processes even large containers in under thirty seconds.

Motivation & Objective

• To address the lack of privilege separation and least privilege enforcement in modern container ecosystems like Docker.
• To reduce container image bloat by eliminating unnecessary resources while preserving application functionality.
• To enable fine-grained privilege separation between components within a single application by partitioning monolithic containers into smaller, focused containers.
• To provide a lightweight, automated, and portable solution that does not require source code or runtime-specific dependencies.
• To develop a mechanism for inter-container communication that maintains security boundaries while enabling transparent execution across containers.

Proposed method

• Dynamic analysis of system call logs to identify resource usage patterns and associate them with individual executables in the container.
• A partitioning algorithm guided by user-defined policies that groups executables and their required resources into isolated containers.
• Remote Process Execution (RPE) as a lightweight mechanism enabling one container to invoke programs in another without breaking isolation or relaxing privilege boundaries.
• Resource minimization by including only the necessary files, libraries, and configurations per partitioned container.
• Use of Linux capabilities and container-level isolation to enforce privilege separation between components.
• An end-to-end prototype that takes a container, system call traces, and user policies as input, and outputs a set of minimal, secure, and functionally equivalent containers.

Experimental results

Research questions

• RQ1 Can dynamic analysis of system calls effectively identify the minimal set of resources required by each executable in a container?
• RQ2 How can monolithic containers be automatically partitioned into smaller, privilege-separated containers while preserving functional correctness?
• RQ3 What lightweight inter-container communication mechanism can maintain security boundaries while enabling transparent execution across containers?
• RQ4 To what extent can container image size be reduced without sacrificing functionality or introducing significant performance overhead?
• RQ5 How effective is the approach on real-world, complex applications such as wikis, databases, and log-analysis stacks?

Key findings

• Cimplifier successfully partitions real-world containers into smaller, minimal containers while preserving the original application functionality.
• The tool reduces container image sizes by 58% to 95% across diverse workloads, including complex applications like wikis and log-analysis stacks.
• Even large and complex containers are processed in under thirty seconds, demonstrating low runtime overhead.
• Remote Process Execution (RPE) enables secure, transparent inter-container communication without requiring kernel support or state migration.
• The approach is effective across a wide range of applications, including those written in different languages and using diverse runtime stacks, without requiring source code or special programming constructs.
• The solution is robust to incomplete test coverage, with potential for future enhancement via user guidance or pattern-based resource expansion.