HI Bret
Thanks for the work. The design doc is very good.
Some feedback/questions below:
This seems a perfect potential attack point. If the attacker wants to modify a read-only variable. He or she may trigger the MFG mode, then no variable is locked. Then the attacker can update the RO variable then reset the system
to normal mode. Is that threat considered?
Thank you
Yao Jiewen
Expanding the audience beyond the RFC list….
If no one has additional input, I’ll try to start formatting these as patches later this week. Thanks!
- Bret
From: Bret Barkelew
Sent: Tuesday, January 28, 2020 5:36 PM
To: rfc@edk2.groups.io
Subject: [RFC] VariablePolicy - Protocol, Libraries, and Implementation for VariableLock Alternative
All,
VariablePolicy is our proposal for an expanded “VarLock-like” interface to constrain and govern platform variables.
I brought this up back in May to get initial comments on the interface and implications of the interface and the approach. We implemented it in Mu over the summer and it is not our defacto variable solution. It plugs in easily to the existing
variable infrastructure, but does want to control some of the things that are currently managed by VarLock.
There are also some tweaks that would be needed if this were desired to be 100% optional code, but that’s no different than the current VarLock implementation which has implementation code directly tied to some of the common variable code.
I’ve structured this RFC in two pieces:
The code can be found in the following two branches:
https://github.com/corthon/edk2/tree/personal/brbarkel/var_policy_rfc_core
https://github.com/corthon/edk2/tree/personal/brbarkel/var_policy_rfc_extra
A convenient way to see all the changes in one place is to look at a comparison:
https://github.com/corthon/edk2/compare/master...corthon:personal/brbarkel/var_policy_rfc_core
There’s additional documentation in the PPT and DOC files in the core branch:
https://github.com/corthon/edk2/blob/personal/brbarkel/var_policy_rfc_core/RFC%20VariablePolicy%20Proposal%20Presentation.pptx
https://github.com/corthon/edk2/blob/personal/brbarkel/var_policy_rfc_core/RFC%20VariablePolicy%20Whitepaper.docx
(You’d need to download those to view.)
My ultimate intention for this is to submit it as a series of patches for acceptance into EDK2 as a replacement for VarLock. For now, I’m just looking for initial feedback on any broad changes that might be needed to get this into shape
for more detailed code review on the devel list.
Thanks!
- Bret