Awesome Linux Containers

Table of Contents

• Foundations
• Specifications
• Clouds
• Hypervisors
• Containers
• Sandboxes
• Partial Access
• Security
  • Tools
  • Links
  • Levels of security problems
  • Technologies for security

Foundations

• OPEN CONTAINER INITIATIVE
  The Open Container Initiative is a lightweight, open governance structure, to be formed under the auspices of the Linux Foundation, for the express purpose of creating open industry standards around container formats and runtime.
• Cloud Native Computing Foundation
  The Cloud Native Computing Foundation will create and drive the adoption of a new set of common container technologies informed by technical merit and end user value, and inspired by Internet-scale computing.

Specifications

• Open Container Specifications
  This project is where the Open Container Initiative Specifications are written. This is a work in progress.
• App Container basics
  App Container (appc) is an open specification that defines several aspects of how to run applications in containers: an image format, runtime environment, and discovery protocol.

Clouds

• Developer Cloud Platform
  PaaS from Docker creators.
• Google Cloud Platform
  Run Docker containers on Google Cloud Platform, powered by Kubernetes. Google Container Engine actively schedules your containers, based on declared needs, on a managed cluster of virtual machines.
• Mesosphere
  The Mesosphere Datacenter Operating System (DCOS) is a new kind of operating system that spans all of the machines in your datacenter or cloud. It provides a highly elastic, and highly scalable way of deploying applications, services and big data infrastructure on shared resources.
• Kubernetes
  Manage a cluster of Linux containers as a single system to accelerate Dev and simplify Ops.

Hypervisors

• Docker
  An open platform for distributed applications for developers and sysadmins. Standart de facto.
• LXD
  Daemon based on liblxc offering a REST API to manage LXC containers.
• OpenVZ
  OpenVZ is container-based virtualization for Linux. OpenVZ creates multiple secure, isolated Linux containers (otherwise known as VEs or VPSs) on a single physical server enabling better server utilization and ensuring that applications do not conflict.

Containers

• runc
  runc is a CLI tool for spawning and running containers according to the OCS specification.
• Rocket
  rkt (pronounced "rock-it") is a CLI for running app containers on Linux. rkt is designed to be composable, secure, and fast. Based on AppC specification.
• LXC
  LXC is the well known set of tools, templates, library and language bindings. It's pretty low level, very flexible and covers just about every containment feature supported by the upstream kernel.
• Vagga
  Vagga is a fully-userspace container engine inspired by Vagrant and Docker, specialized for development environments.
• libct
  Libct is a containers management library which provides convenient API for frontend programs to rule a container during its whole lifetime.
• libvirt
  A big toolkit to interact with the virtualization capabilities of recent versions of Linux (and other OSes).

Sandboxes

• Firejail
  Firejail is a SUID sandbox program that reduces the risk of security breaches by restricting the running environment of untrusted applications using Linux namespaces, seccomp-bpf and Linux capabilities.
• NsJail
  NsJail is a process isolation tool for Linux. It makes use of the the namespacing, resource control, and seccomp-bpf syscall filter subsystems of the Linux kernel.
• Subuser
  Securing the Linux desktop with Docker.
• Snappy
  Snappy Ubuntu Core is a new rendition of Ubuntu with transactional updates - a minimal server image with the same libraries as today’s Ubuntu, but applications are provided through a simpler mechanism.
• xdg-app
  xdg-app is a system for building, distributing and running sandboxed desktop applications on Linux.

Partial Access

• nsenter
  Run program with namespaces of other processes. Part of the util-linux.
• ip-netns
  Process network namespace management. Part of the iproute2.
• unshare
  Run program with some namespaces unshared from parent. Part of the util-linux.
• python-nsenter
  This Python package allows entering Linux kernel namespaces (mount, IPC, net, PID, user and UTS) by doing the "setns" syscall.
• butter
  Python library to interface to low level linux features (inotify, fanotify, timerfd, signalfd, eventfd, containers) with asyncio support.
• pyspaces
  Works with Linux namespaces through glibc with pure python.

Security

Tools

• Docker bench security
  The Docker Bench for Security is a script that checks for dozens of common best-practices around deploying Docker containers in production.

Links

• CIS Security Benchmarks
• Are Docker containers really secure?
• Bringing new security features to Docker
• Docker, Linux Containers (LXC), and security
• For containers, security is problem #1
• Linux Container Security
• Ask HN: Best Linux sandbox?
• CIS Docker 1.6 Benchmark v1.0.0
• Understanding docker security and best practices

Levels of security problems

1. regular application

• always untrusted -> know it
• suid bit -> mount with nosuid
• limit available syscall -> seccomp-bpf, grsec
• leak to another container (bug in namespaces, filesystem) -> user namespaces with different uid inside for each cotainer: 1000 in container - 14293 and 15398 outside; security modules like selinux or apparmor

2. system services like cron, ssh

• run as root -> isolate via bastion host or vm
• using /dev -> "devices" control group
  The following device nodes are created in the container by default.
  The Docker images are also mounted with nodev, which means that even if a device node was pre-created in the image, it could not be used by processes within the container to talk to the kernel.
  /dev/console,/dev/null,/dev/zero,/dev/full,/dev/tty*,/dev/urandom,/dev/random,/dev/fuse
• root calls -> capabilities (cap_sys_admin warning!)
  Here is the current list of capabilities that Docker uses: chown, dac_override, fowner, kill, setgid, setuid, setpcap, net_bind_service, net_raw, sys_chroot, mknod, setfcap, and audit_write.
  Docker removes several of these capabilities including the following:
  CAP_SETPCAP Modify process capabilities
  CAP_SYS_MODULE Insert/Remove kernel modules
  CAP_SYS_RAWIO Modify Kernel Memory
  CAP_SYS_PACCT Configure process accounting
  CAP_SYS_NICE Modify Priority of processes
  CAP_SYS_RESOURCE Override Resource Limits
  CAP_SYS_TIME Modify the system clock
  CAP_SYS_TTY_CONFIG Configure tty devices
  CAP_AUDIT_WRITE Write the audit log
  CAP_AUDIT_CONTROL Configure Audit Subsystem
  CAP_MAC_OVERRIDE Ignore Kernel MAC Policy
  CAP_MAC_ADMIN Configure MAC Configuration
  CAP_SYSLOG Modify Kernel printk behavior
  CAP_NET_ADMIN Configure the network
  CAP_SYS_ADMIN Catch all
  uses /proc, /sys -> remount ro, drop cap_sys_admin; security modules like selinux or apparmor; some part of this fs are "namespace-aware"
  Docker mounts these file systems into the container as "read-only" mount points.
  . /sys
  . /proc/sys
  . /proc/sysrq-trigger
  . /proc/irq
  . /proc/bus
  Copy-on-write file systems
  Docker uses copy-on-write file systems. This means containers can use the same file system image as the base for the container. When a container writes content to the image, it gets written to a container specific file system. This prevents one container from seeing the changes of another container even if they wrote to the same file system image. Just as important, one container can not change the image content to effect the processes in another container.
• uid 0 -> user namespaces, uid 0 mappet to random uid outside

3. system services like devices, network, filesystems

• root -> more of services should work on host outside; isolate sensitive functions, run as non-privilaged context
• full privilages -> isolate on kernel level

4. kernel drivers, network stack, security policies

• absolute privilages -> run it in separate vm

5. general like immutable infrastructure

• container is ro
• write to small separate rw nosuid part

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Technologies for security

Things are better. For example, most modern container technologies can make use of Linux's built-in security tools such as:
AppArmor, SELinux and Seccomp policies;
Grsecurity;
Control groups (cgroups);
Kernel namespaces
src

Sure, you're deploying seccomp, but you can't use selinux inside your container, because the policy isn't per-namespace (?? lxc uses apparmore for each container...)
sVirt - selinux for kvm
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Major kernel subsystems are not namespaced like:

• SELinux
• Cgroups
• file systems under /sys
• /proc/sys, /proc/sysrq-trigger, /proc/irq, /proc/bus

Devices are not namespaced:

• /dev/mem
• /dev/sd* file system devices
• kernel modules

If you can communicate or attack one of these as a privileged process, you can own the system.
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