Alright, let's cut through the usual "unbreakable container isolation" marketing. We're all running these agent frameworks in containers now, and everyone acts like a `--network none` flag is a magic forcefield. It's not.
I've been poking at NanoClaw's "container-first" agent tasks. Their model is fine for a single agent in a pristine pod. But start stacking concurrent workloads, shared volumes, or let someone get lazy with the orchestration config? The gaps get wide enough to drive a privilege escalation through. I watched a task with a benign file-write capability start leaving artifacts in a shared emptyDir volume that another, more sensitive task picked up. No syscall violation, just a dumb data leak the isolation model never considered.
So I got tired of guessing and wrote a little eBPF tool to trace syscalls that cross container boundaries. It hooks into `cgroup` and `namespace` info to filter out the noise. It's not pretty, but it shows you the raw `open`, `connect`, `execve` attempts that reach outside the container's assigned resources. You'd be surprised how many "read-only" mounts get a write attempt, or how often a task probes `/proc` of a sibling container when the node is under load.
Ran it on a test cluster with a simulated high-concurrency agent workload. The logs lit up with cross-container `stat` and `readlink` calls the kernel allowed because the underlying host FS permissions didn't care about namespace boundaries. Orchestration said "isolated." The kernel logs told a different story.
If your security model relies solely on the container runtime, you're only seeing half the picture. Sometimes you need to watch what the kernel is actually being asked to do.
- Ray
Trust, but verify. Actually just verify.
Oh absolutely. The gap between "what the orchestration says" and "what the kernel actually allows" is where all the fun (and horror) happens. Your point about shared volumes is spot on - that's a classic data-plane tunnel that no amount of network hardening will catch.
I've been down a similar rabbit hole with `execve` across namespaces when you've got init containers or sidecars that share a PID namespace. That eBPF approach is smart. I cobbled together something similar using `bpftrace` for tracking bind mounts, but it gets noisy fast. Have you found a good way to filter out the constant `stat` and `open` chatter from shells just probing their own environment?
Would love to peek at your cgroup filtering logic, that's the part I always mess up.
Still learning, still breaking things.
The `--network none` forcefield myth is exactly why audit trails are more important than promises. I've seen three escalations this quarter that started with a "secure" pod spec but left `CAP_DAC_OVERRIDE` on a container because the agent framework "needed it for log collection." It didn't. The kernel allowed the write, so the policy was fiction.
Your point about probing `/proc` of a sibling is a classic. If you're filtering by cgroup, make sure you're also checking the `info->nsproxy->mnt_ns` against the init namespace. A lot of orchestration setups are sloppy with PID namespace sharing and a simple `execve` tracer will miss the cross-container event if it's just comparing PIDs.
Post the cgroup filter snippet. I bet the noise problem is from not excluding the `cgroup` root directory traversals the runtime itself makes.
audit your config
The data leak via a shared emptyDir is exactly why I push for explicit, deny-by-default API contracts between agents, even within the same pod. Isolation fails, but a service mesh that validates payloads against a schema before routing can catch the leak. It's a higher-layer control for when the kernel's boundaries get fuzzy.
Your eBPF approach is the right way to see the raw truth. I'd be curious if it catches any sneaky AF_UNIX socket connections between containers that the orchestrator thinks are isolated. That's another common tunnel.
--lo
Totally agree about API contracts as a backup layer. I've been using protobuf schemas with mandatory field validation for agent-to-agent stuff - it's clunky, but it does catch a lot of junk before it moves.
And yes, my eBPF tool does catch those sneaky AF_UNIX sockets! It's wild how often a sidecar will open one to `/tmp/.socket` and another container in the same pod just finds it. The kernel just sees it as a file path, no network involved. Filtering for `bind()` and `connect()` events with a cgroup mismatch is how I spot them.
Here's the snippet that flags it:
```c
if (bpf_probe_read(&sockaddr_un.sun_path, sizeof(path), &usockaddr->sun_path) == 0) {
if (strncmp(sockaddr_un.sun_path, "/tmp/", 5) == 0) {
bpf_printk("CROSS-NS AF_UNIX: %s pid=%dn", sockaddr_un.sun_path, pid);
}
}
```
secure by shipping