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Containers have a history of escape vulnerabilities, for reasons like sharing a kernel with the host and other containers. VMs are designed from the ground up

Containers have a history of escape vulnerabilities, for reasons like sharing a kernel with the host and other containers. VMs are designed from the ground up to isolate guests, rather than focusing on application deployment. Firecracker is the modern container alternative in untrusted compute scenarios, with Fly.io even converting container images into Firecracker VMs.

NovemberWhiskey 4y ago
>Containers have a history of escape vulnerabilities Generally agreed, but for this use-case do we care?
- nneonneo 4y ago
  I haven’t gotten any of the challenges to load, but if you’re going to simulate a sysadmin it would make sense to give you high privileges (or even root) on the box. The more privileged you are inside a container, the more attack surface you expose.
  - BossingAround 4y ago
    Which is why you create a "dummy" host VM that hosts containers. Nobody's saying "host containers on your prod webserver." On the other hand, spinning up a VM for every user seems insane to me.
encryptluks2 4y ago
User mapping is now a standard feature in Kubernetes, so escape vulnerabilities aren't so much an issue anymore. Additionally, you can use gVisor.
- paulfurtado 4y ago
  User namespaces have resulted in multiple new container breakout CVEs in the last year. Some guides actually recommend disabling user namespaces because they are still somewhat new and perilous.
  - encryptluks2 4y ago
    What are the ones in the last year? They provide security benefits as well. I mean, you could say the Linux kernel is also dangerous and the Windows kernel and pretty much anything that has ever had a CVE. You can also limit it to specific users too if that is a major concern.
  - cyphar 4y ago
    You're talking about creating new user namespaces inside a container, not running a container in a user namespace. Running a container in a user namespace is strictly a security improvement over running it in the host user namespace. Also, all container runtimes automatically block unshare(CLONE_NEWUSER) with seccomp already (unless they've disabled seccomp, which I'm not sure if Kubernetes still does).

NovemberWhiskey 4y ago

>Containers have a history of escape vulnerabilities Generally agreed, but for this use-case do we care?

nneonneo 4y ago
I haven’t gotten any of the challenges to load, but if you’re going to simulate a sysadmin it would make sense to give you high privileges (or even root) on the box. The more privileged you are inside a container, the more attack surface you expose.
- BossingAround 4y ago
  Which is why you create a "dummy" host VM that hosts containers. Nobody's saying "host containers on your prod webserver." On the other hand, spinning up a VM for every user seems insane to me.

encryptluks2 4y ago

User mapping is now a standard feature in Kubernetes, so escape vulnerabilities aren't so much an issue anymore. Additionally, you can use gVisor.

paulfurtado 4y ago
User namespaces have resulted in multiple new container breakout CVEs in the last year. Some guides actually recommend disabling user namespaces because they are still somewhat new and perilous.
- encryptluks2 4y ago
  What are the ones in the last year? They provide security benefits as well. I mean, you could say the Linux kernel is also dangerous and the Windows kernel and pretty much anything that has ever had a CVE. You can also limit it to specific users too if that is a major concern.
- cyphar 4y ago
  You're talking about creating new user namespaces inside a container, not running a container in a user namespace. Running a container in a user namespace is strictly a security improvement over running it in the host user namespace. Also, all container runtimes automatically block unshare(CLONE_NEWUSER) with seccomp already (unless they've disabled seccomp, which I'm not sure if Kubernetes still does).