Network isolation with RLIMIT_NETWORK, cont'd.

Michael Stone
2009-12-13T03:25:15Z

Dear lkml,

A few months ago [1], I asked for feedback on a new network isolation primitive
named "RLIMIT_NETWORK" designed for use with Unix sandboxing utilities like
Rainbow, Plash, and friends [2]. Thank you to all those CC'ed for your helpful
early remarks.

Here is an updated patchset with responses to the following criticisms:

1. ptrace()

It was pointed out by Alan Cox, Andi Kleen, and others that processes
which dropped their RLIMIT_NETWORK rlimit were still able to directly
perform networking through a ptrace()'d victim.

The new patchset adds an access check to __ptrace_may_access() to prevent
this behavior.

2. unshare(CLONE_NEWNET)

It was pointed out by James Morris that network namespaces could be used
to implement behavior similar to the behavior this patchset is designed to
implement. To address this criticism, I added support for network
namespaces to my sandboxing utility (Rainbow).

Unfortunately, I have discovered that network namespaces in their current
form are not appropriate for my use cases because they prevent the
namespace'd apps from connecting to the X server, even over plain old
AF_UNIX sockets.

The RLIMIT_NETWORK facility I propose contains a specific exception for
AF_UNIX filesystem sockets since those sockets are already bound by
regular Unix discretionary access control.

3. style

I have made the patches more consistent with the kernel style
guidelines.

Further suggestions?

Michael

[1] http://kerneltrap.org/mailarchive/linux-netdev/2009/1/7/4624864
[2] http://sandboxing.org