The State of Sandboxing in Open Source Software

Sandboxing is a technique used to restrict how software applications interact with the system. The goal is to prevent programs from accessing more resources than they need, following a principle called "least privilege." In simpler terms, if an application only needs to do a few things, it shouldn't be allowed to do everything. Sandboxes act like barriers that limit what a program can do, which helps protect the system from harmful actions.

#Importance of Sandboxing

You can't always trust software to behave correctly. Sometimes, attackers exploit weaknesses in programs to gain more control over a system. Sandboxes help reduce this risk by ensuring that programs run with the minimum permissions needed. For example, if a program shouldn't be able to access certain files or network features, the sandbox will block that access.

In the world of open-source software, sandboxing is especially important. Open-source systems are built by combining various software packages, and ensuring that these packages work safely together is crucial. Although most operating systems today provide some form of sandboxing, there isn't much standardization. Each operating system has its own set of sandboxing tools, which can sometimes make it complicated for developers to implement sandboxing.

#The Challenge of Sandboxing

Even though sandboxing is important, the actual use of sandboxing mechanisms in open-source software packages is surprisingly low. Research has shown that less than 1% of software packages directly use these mechanisms, but many packages might still rely on others that do.

To understand how developers are using sandboxing, we looked at several different operating systems. Each operating system has its own unique sandboxing tools:

• Linux uses tools like Seccomp and Landlock.
• FreeBSD offers Capsicum.
• OpenBSD has Pledge and Unveil.

#Research Questions

This study sought to answer some key questions regarding the use of sandboxing in software packages:

1. How widely are sandboxing mechanisms used in different operating systems?
2. How do these mechanisms compare in terms of complexity and security when securing the same software package across various operating systems?

#Findings on Sandboxing Usage

The investigation revealed that while many packages depend on others that employ sandboxing, the number of packages that directly use sandboxing APIs is low across all systems. We discovered instances where developers simplified their sandboxing implementation, choosing less complex methods instead of fully utilizing the capabilities of more advanced tools.

Using sandboxing requires developers to change their code to fit certain requirements. Interestingly, the more straightforward sandboxing methods, like those provided by OpenBSD’s Pledge, sometimes lead to stricter restrictions than more complex methods such as Seccomp.

#Overview of Sandboxing Mechanisms

#Seccomp

Seccomp, short for secure computing, was introduced to Linux in 2005. It allows developers to limit the system calls their applications can make. By creating a list of allowed or denied system calls, developers can control what their programs are permitted to do.

With Seccomp, developers can specify which system calls are allowed and set actions for when restricted calls are made. For example, a program can be set to terminate if it tries to make an unauthorized system call. Developers can also use a library called libseccomp, which makes it easier to use Seccomp without needing to write complex code.

#Landlock

Landlock arrived as a Linux security module in 2017. It allows developers to define access rules for files and directories. With Landlock, developers can restrict access to certain parts of the file system or limit actions to read-only. Similar to Seccomp, Landlock inherits the restrictions from parent processes.

#Pledge and Unveil

OpenBSD provides Pledge and Unveil, which are simpler systems for sandboxing compared to Seccomp and Landlock. Pledge enables developers to declare that their application will only use certain features or functions. If a program tries to perform actions outside its defined promises, it will terminate.

Unveil works alongside Pledge by limiting applications to specific directories with certain permissions. If an application tries to access files or directories it has not been granted permission for, it will be stopped.

#Capsicum

FreeBSD utilizes Capsicum, which allows developers to control access based on file descriptors. This means developers can set what a program can or cannot access based on specific files or resources. Once a program enters capability mode, it cannot access the broader system, making it a useful tool for sandboxing.

#The Study of Package Usage

To get a clearer picture of how sandboxing is adopted in different operating systems, we analyzed source code from various repositories. We focused on popular open-source systems like Debian and Fedora, as well as FreeBSD and OpenBSD. By examining their packages, we aimed to understand how many and which packages utilize sandboxing.

Packages that use sandboxing mechanisms were identified by searching for specific calls related to sandboxing in the code. We took steps to ensure that our findings were accurate, filtering out irrelevant instances where sandboxing was only present in testing code.

#Percentage of Packages Using Sandboxing

Despite examining thousands of packages, the number using sandboxing mechanisms directly was very low across all operating systems. In many cases, packages that seemed to have sandboxed code were actually relying on other packages that used sandbox mechanisms. As a result, understanding whether a program is truly sandboxed can be complex, as it may rely on several dependencies.

#Types of Applications That Use Sandboxing

When we looked at the kinds of applications that utilize sandboxing mechanisms, we noticed a clear difference between operating systems. For Linux, most sandboxed packages belonged to development and library categories. In contrast, FreeBSD and OpenBSD had a larger number of network and utility applications using sandboxing.

Network tools are particularly good candidates for sandboxing since they often interact with external users. OpenBSD stands out for having a much higher percentage of networking packages employing sandboxing compared to Linux distributions.

#What is Sandboxed Code Doing?

With sandboxing tools like Seccomp, developers have the ability to control system calls and restrict actions based on the arguments provided. Many programs go beyond simply allowing or denying system calls; they limit how those calls are executed. This often involves writing complex filters that can be difficult to create.

Interestingly, our study showed that a significant number of developers chose to implement more complex sandboxes even when simpler options were available. This suggests that many developers are interested in creating secure applications, despite the challenges involved.

#Comparing Sandboxing Across Systems

We also looked at how different systems implement sandboxing for the same application. In doing so, we discovered that Seccomp allowed for very detailed sandboxes compared to Pledge. For example, when examining a specific application called arping, we found that its sandbox in Linux was much stricter than its versions in other operating systems.

On the other hand, some applications did not take full advantage of the capabilities offered by Seccomp. In one such case, the xwallpaper package implemented Seccomp not to enhance security but merely to replicate what was already achieved with Pledge.

#Sandboxing at Startup

When we examined the processes that run right after system boot, we observed interesting trends. OpenBSD displayed a clear lead with a notable number of processes using Pledge or Unveil. On the other hand, Fedora and Debian had fewer processes utilizing their sandboxing mechanisms.

These observations highlight that while a small number of packages directly invoke sandboxing APIs, many of them depend on others that do. The true extent of sandboxing usage can often be masked by these dependencies, making it difficult to assess security accurately.

#Barriers to Sandboxing Adoption

Despite the availability of sandboxing mechanisms, there are still barriers preventing wider adoption. One challenge is that developers need to have a thorough understanding of their applications and the system calls being used. This can be daunting for large and complex programs.

Debugging sandboxed applications can also be tricky. If a program tries to perform an action outside its permitted scope, it will terminate. Developers then must analyze the error to determine what went wrong.

#Potential Solutions

To encourage the use of sandboxing, it may help for programming languages to incorporate security measures by default. By requiring developers to explicitly request permissions for certain actions, the pressure to adopt security practices becomes more significant.

Additionally, developing tools that can help monitor applications for excessive permissions could improve the situation. By offering insights into how programs use resources, developers will be more inclined to adopt sandboxing mechanisms.

#Conclusion

While sandboxing is a crucial part of ensuring security in software, the current adoption levels in open-source ecosystems are low. Although some packages employ sandboxing mechanisms, many more rely on indirect usage through dependencies. The landscape of sandboxing varies significantly between different operating systems and applications, and understanding how developers approach these mechanisms will be key to improving their adoption.

As security concerns continue to grow, finding ways to simplify the implementation of sandboxing and reinforce its importance will be essential. Through better understanding and support, we can help foster a more secure software environment in open-source ecosystems.