In a WASM + seccomp implementation, the whole WASM runtime runs inside seccomp. Breaking out of WASM leaves one running arbitrary asm inside seccomp, which has exactly the same attack surface as directly running untrusted binaries inside seccomp. The WASM layer in WASM + seccomp simply requires an additional exploit.

You’re referring to seccomp-bpf, not seccomp. Seccomp-bpf + wasm has a dramatically larger attack surface than just seccomp. Please check references if you do not know the difference between seccomp-bpf and seccomp: https://en.wikipedia.org/wiki/Seccomp

> Using wasm in addition to seccomp strictly increases your attack surface. If you want to maximize security you would only use seccomp.

Huh? How so?

The wasm vm has to parse, validate, and compile untrusted input. It also exposes host calls. Those are all potential attack vectors. That’s at least roughly 50K LOC.

>It also exposes host calls.

Only if you grant explicit access to them. What usually happens is that there is a vendor provided API that only gives you access to exactly what you need which is significantly less powerful than a complete linux process that can write to files, spawn background threads, etc all by default.

Yes you can block access to these things but you're going to miss something at some point.

In seccomp the only syscalls available are read, write, exit, and sigreturn. There is nothing to miss