[cfe-dev] Implementing linux randstruct plugin for clang?

[Friedman, Eli via cfe-dev]

Hi all,

Recently our team was asked about the possibility of implementing 
functionality equivalent to the Linux kernel's randstruct gcc plugin for 
clang.  Essentially, what the plugin does is modify the AST to put the 
members of structs marked with "__attribute__((randomize_layout))" in a 
random order (order chosen at compile-time, and controlled by a provided 
seed).  The idea is that this provides security hardening by making it 
harder for an attacker to guess where a field is stored in memory.  See 
https://lwn.net/Articles/722293/ for more details.

I can see the following possible approaches for implementing this with 
clang:

1. A source-rewriting plugin which generates a new version of the source 
code with reordered structs.  This probably doesn't require any changes 
to clang itself, but it introduces a bunch of complexity interacting 
with the build system for a project.

2. Some new kind of plugin which hooks deeply into semantic analysis; 
not sure what this would look like.

3. Modifying clang's structure layout code.  This is probably easiest to 
write the code for, but merging it to the clang repo would require 
consensus that this is actually generally useful.

Has anyone else looked at this?

-Eli

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project