On Wed, Aug 16, 2017 at 1:36 PM, Denis Kudriashov <dionisiydk@gmail.com> wrote:

Hi Eliot.

I asked David why he didn't add it to the SocketPlugin in the first place and he discussed Andreas Rabb's security concerns

It would be interesting to read about them because it looks strange that it is secure to manage OS handle from VM but not secure to manage it from image side. Both ways are requested by user directly or indirectly which means that user has OS permissions. So what the difference?

It's for when you want to allow arbitrary code to be executed in the image, yet still protect the machine from harm. This happens when sharing objects between images - an object could have malicious code attached. So in that case, before running the code, we turn on the VM file sandbox via the SecurityPlugin. This ensures that the image can only access files in a sandbox directory but not outside. But it only works if the FilePlugin is the only way to access files - meaning FFI and OSProcess etc. must be disabled, and there must not be another way to create file handles.

So IMHO, if the goal is to get a raw handle for using in FFI, then that's okay, since all security goes out the door as soon as FFI is enabled anyway. And if FFI is not enabled, then the raw file handle isn't useful, so there is no need to restrict read-access to it. Or am I missing something?

TL;DR read-only access to raw file handle may not be a security issue.

- Bert -