Today, let’s pivot from hacking into the mysterious realm of containers. Containers are the backbone of today’s infrastructure, providing lightweight environments for running applications. Docker might ring a bell, but ever wondered about the magic behind the scenes? Let’s delve deep by building our container using Go, a popular programming language known for its simplicity and efficiency.
Why Go?
Just as we prefer particular tools for specific vulnerabilities, the world of containers loves Go for its straightforward syntax, combined with its vast standard library, making it ideal for system-level programming.
Step 1: Setting the Stage
Just like our initial scan in hacking, setting up the environment is crucial. Go provides native support for Linux namespaces and cgroups, which makes it a top choice for crafting containers. These systems help in process isolation and resource limitation, respectively.
Step 2: Namespaces and cgroups
In the hacking realm, we focus on privileges, ensuring we have the right access levels. Similarly, when diving into containers, ensuring process isolation is critical. This is where Linux namespaces come into play. With Go, we can manipulate these namespaces to ensure our process feels it’s alone in the universe, even though it’s sharing the host with many others.
Likewise, cgroups ensure our container doesn’t hog all available resources. Just as we limit the processes in our HTB challenges, we need to ensure our container behaves well, limiting its greediness.
Step 3: The Heart – Code
Here’s a tiny snippet that demonstrates the Go magic:
cmd := exec.Command("/proc/self/exe", append([]string{"child"}, command...)...) cmd.SysProcAttr = &syscall.SysProcAttr{ Cloneflags: syscall.CLONE_NEWUTS | syscall.CLONE_NEWPID | syscall.CLONE_NEWNS | syscall.CLONE_NEWUSER, }
This code is equivalent to our reverse shell techniques, creating a process but with isolated namespaces.
Step 4: Chroot – The Alpinelinux Filesystem
In our hacking adventures, we often encounter different file systems and have to navigate them. Here, we’ll pull a minimal Linux filesystem, Alpinelinux. Using the Chroot system call, we change the apparent root directory, ensuring our process doesn’t see beyond the bounds of our container.
Dive Deeper:
- For a comprehensive walkthrough of how this container was built with Go, check out my GitHub repository.
- Deep Into Container: Build Your Own Container with Golang
- Understanding Containers
Closing Thoughts
Containers might seem like a complex realm, but with languages like Go, the fog lifts. It’s similar to cracking that tough box on HTB; once you understand the underlying principles, it becomes second nature. Just remember, the essence of learning is exploration and experimentation. So, roll up your sleeves, and let’s continue coding and hacking!
See you in the next post! 😉
VostDev 