Dandan,

I’ve addressed points 1-3 in this commit:
https://github.com/corthon/edk2/tree/var_policy_dev_submission_v7

I’ve also added a note to the new ReadMe about point #6:
https://github.com/corthon/edk2/tree/var_policy_dev_submission_v7/MdeModulePkg/Library/VariablePolicyLib#disablevariablepolicy

Will put up a v7 of patches this week.

- Bret

From: Bret Barkelew via groups.io<mailto:bret.barkelew=microsoft....@groups.io>
Sent: Monday, August 17, 2020 10:24 PM
To: devel@edk2.groups.io<mailto:devel@edk2.groups.io>; 
dandan...@intel.com<mailto:dandan...@intel.com>; 
b...@corthon.com<mailto:b...@corthon.com>
Cc: Yao, Jiewen<mailto:jiewen....@intel.com>; Zhang, Chao 
B<mailto:chao.b.zh...@intel.com>; Wang, Jian J<mailto:jian.j.w...@intel.com>; 
Wu, Hao A<mailto:hao.a...@intel.com>; liming.gao<mailto:liming....@intel.com>; 
Justen, Jordan L<mailto:jordan.l.jus...@intel.com>; Laszlo 
Ersek<mailto:ler...@redhat.com>; Ard Biesheuvel<mailto:ard.biesheu...@arm.com>; 
Andrew Fish<mailto:af...@apple.com>; Ni, Ray<mailto:ray...@intel.com>
Subject: [EXTERNAL] Re: [edk2-devel] [PATCH v6 00/14] Add the VariablePolicy 
feature

Responses below…

- Bret

From: Dandan Bi via groups.io<mailto:dandan.bi=intel....@groups.io>
Sent: Tuesday, August 11, 2020 6:52 AM
To: devel@edk2.groups.io<mailto:devel@edk2.groups.io>; Bi, 
Dandan<mailto:dandan...@intel.com>; b...@corthon.com<mailto:b...@corthon.com>
Cc: Yao, Jiewen<mailto:jiewen....@intel.com>; Zhang, Chao 
B<mailto:chao.b.zh...@intel.com>; Wang, Jian J<mailto:jian.j.w...@intel.com>; 
Wu, Hao A<mailto:hao.a...@intel.com>; liming.gao<mailto:liming....@intel.com>; 
Justen, Jordan L<mailto:jordan.l.jus...@intel.com>; Laszlo 
Ersek<mailto:ler...@redhat.com>; Ard Biesheuvel<mailto:ard.biesheu...@arm.com>; 
Andrew Fish<mailto:af...@apple.com>; Ni, Ray<mailto:ray...@intel.com>
Subject: [EXTERNAL] Re: [edk2-devel] [PATCH v6 00/14] Add the VariablePolicy 
feature

Hi Bret,

Sorry for the delayed response.

Some more comments here:

1. Currently I see the LockVaribePolicy is called at ReadyToBoot by variable 
driver, could we update it to be called at EndOfDxe? We should prevent 
malicious code registering policy after EndOfDxe for security concern. And 
could we also add the test case to check the variable policy is locked at 
EndofDxe?
We could. Right now it’s at ReadyToBoot because it’s just there as a safety net 
and the platform could lock it earlier. Would it work to have a PCD for which 
EventGroup GUID the platform should lock on?

2. For patch 4, the SMM communication,  some general guidelines for SMI handler:
a)  Check whether the communication buffer is outside SMM and valid.
For this feature, please double check whether the communication buffer is 
checked, if all the range in communication buffer has already been checked 
within existing edk2 core infrastructure, please also add the comments in the 
code to mention that it has been checked.
I checked this, but I will recheck (since there’ve been a few revisions in the 
patches) and update the comments.

b) Should copy the communication buffer to SMRAM before checking the data 
fields to avoid TOC/TOU attac
For this feature, for example, when dump variable policy, if malicious code 
updates the DumpParams->TotalSize in communication buffer to smaller one to 
allocate the PaginationCache buffer, and then update it the correct one and 
dump the variable policy data into the PaginationCache buffer, it will cause 
buffer overflow in this case.  So please double check the code and copy the 
communication buffer into SMRAM to avoid such kind issue.
Will also check for this.

3. Did you do any security test for this feature?
Such as? There are both unit tests and integration tests to ensure correct 
functionality and that the disable and lock interfaces work as expected. I 
haven’t fuzzed it or anything that involved.

4. Currently, LockVariablePolicy can prevent RegisterVariablePolicy and 
DisableVariablePolicy. So in SMI hander, could we check the variable policy is 
locked or not firstly and then decide whether need to check and execution for 
VAR_CHECK_POLICY_COMMAND_REGISTER and VAR_CHECK_POLICY_COMMAND_DISABLE?
I’ll take a look, but my gut says this may be an unnecessary complication.

5. Since there is the logic when variable policy is disabled, it will permit 
deletion of auth/protected variables. Could we add some comments in code to 
mention that variable policy should always be enabled for security concern to 
avoid giving bad example?
I’m happy to think about how to document this, but I’m not immediately inclined 
to outright say it shouldn’t be disabled. I’d be happy to say that it shouldn’t 
be disabled in “normal, production configuration”, but it’s entirely reasonable 
to be disabled in a Manufacturing or R&R environment and we would actually 
prefer this be used because it would at least be consistent across platforms, 
rather than being something done ad hoc by each platform that needs it. Would 
that be sufficient?

Thanks,
Dandan
> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Dandan
> Bi
> Sent: Thursday, July 2, 2020 10:14 AM
> To: devel@edk2.groups.io; b...@corthon.com
> Cc: Yao, Jiewen <jiewen....@intel.com>; Zhang, Chao B
> <chao.b.zh...@intel.com>; Wang, Jian J <jian.j.w...@intel.com>; Wu, Hao
> A <hao.a...@intel.com>; Gao, Liming <liming....@intel.com>; Justen,
> Jordan L <jordan.l.jus...@intel.com>; Laszlo Ersek <ler...@redhat.com>;
> Ard Biesheuvel <ard.biesheu...@arm.com>; Andrew Fish
> <af...@apple.com>; Ni, Ray <ray...@intel.com>
> Subject: Re: [edk2-devel] [PATCH v6 00/14] Add the VariablePolicy feature
>
> Hi Bret,
>
> Thanks for the contribution.
>
> I have taken an overview of this patch series and have some small comments
> in the related patches, please check in sub-patch.
>
> I will review the patch series more in details and bring more comments back
> if have. Do you have a branch for these patches in GitHub? Which should be
> easy for review.
>
>
> Thanks,
> Dandan
>
> > -----Original Message-----
> > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Bret
> > Barkelew
> > Sent: Tuesday, June 23, 2020 2:41 PM
> > To: devel@edk2.groups.io
> > Cc: Yao, Jiewen <jiewen....@intel.com>; Zhang, Chao B
> > <chao.b.zh...@intel.com>; Wang, Jian J <jian.j.w...@intel.com>; Wu,
> > Hao A <hao.a...@intel.com>; Gao, Liming <liming....@intel.com>;
> > Justen, Jordan L <jordan.l.jus...@intel.com>; Laszlo Ersek
> > <ler...@redhat.com>; Ard Biesheuvel <ard.biesheu...@arm.com>;
> Andrew
> > Fish <af...@apple.com>; Ni, Ray <ray...@intel.com>
> > Subject: [edk2-devel] [PATCH v6 00/14] Add the VariablePolicy feature
> >
> > REF:https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.tianocore.org%2Fshow_bug.cgi%3Fid%3D2522&amp;data=02%7C01%7CBret.Barkelew%40microsoft.com%7C91eed7c4a0d54e2eff6008d83dfdc4ec%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637327507431539442&amp;sdata=cLpx7VZsG%2F6r6GCXmiCS4DmmgOH4iKfX3VSAAYUOU00%3D&amp;reserved=0
> >
> > The 14 patches in this series add the VariablePolicy feature to the
> > core, deprecate Edk2VarLock (while adding a compatibility layer to
> > reduce code churn), and integrate the VariablePolicy libraries and
> > protocols into Variable Services.
> >
> > Since the integration requires multiple changes, including adding
> > libraries, a protocol, an SMI communication handler, and
> > VariableServices integration, the patches are broken up by individual
> > library additions and then a final integration. Security-sensitive
> > changes like bypassing Authenticated Variable enforcement are also
> > broken out into individual patches so that attention can be called directly 
> > to
> them.
> >
> > Platform porting instructions are described in this wiki entry:
> > https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Ftianocore%2Ftianocore.github.io%2Fwiki%2FVariablePolicy-&amp;data=02%7C01%7CBret.Barkelew%40microsoft.com%7C91eed7c4a0d54e2eff6008d83dfdc4ec%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637327507431539442&amp;sdata=%2FYNgK7yixA5Gi7E9bHw3LIUNAQpZMh9ykTUqCqv2SRY%3D&amp;reserved=0<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Ftianocore%2Ftianocore.github.io%2Fwiki%2FVariablePolicy-&data=02%7C01%7Cbret.barkelew%40microsoft.com%7C51274073e4134461747308d843370a1b%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637333250980602108&sdata=fR%2F3c27FBmYi0SxMyBgY20asvdiur4kOtASBBZt5iTg%3D&reserved=0>
> > Protocol---Enhanced-Method-for-Managing-Variables#platform-porting
> >
> > Discussion of the feature can be found in multiple places throughout
> > the last year on the RFC channel, staging branches, and in devel.
> >
> > Most recently, this subject was discussed in this thread:
> > https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fedk2.groups.io%2Fg%2Fdevel%2Fmessage%2F53712&amp;data=02%7C01%7CBret.Barkelew%40microsoft.com%7C91eed7c4a0d54e2eff6008d83dfdc4ec%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637327507431539442&amp;sdata=i7qaO6eZT8%2BzCT0satTptMWwCNspDz%2BS05eJmGGR628%3D&amp;reserved=0<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fedk2.groups.io%2Fg%2Fdevel%2Fmessage%2F53712&data=02%7C01%7Cbret.barkelew%40microsoft.com%7C51274073e4134461747308d843370a1b%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637333250980612106&sdata=fRMoSDlZ0tyrL3fGqowQlipsVdn31LGn1gRQXRKa3pQ%3D&reserved=0>
> > (the code branches shared in that discussion are now out of date, but
> > the whitepapers and discussion are relevant).
> >
> > Cc: Jiewen Yao <jiewen....@intel.com>
> > Cc: Chao Zhang <chao.b.zh...@intel.com>
> > Cc: Jian J Wang <jian.j.w...@intel.com>
> > Cc: Hao A Wu <hao.a...@intel.com>
> > Cc: Liming Gao <liming....@intel.com>
> > Cc: Jordan Justen <jordan.l.jus...@intel.com>
> > Cc: Laszlo Ersek <ler...@redhat.com>
> > Cc: Ard Biesheuvel <ard.biesheu...@arm.com>
> > Cc: Andrew Fish <af...@apple.com>
> > Cc: Ray Ni <ray...@intel.com>
> > Cc: Bret Barkelew <brbar...@microsoft.com>
> > Signed-off-by: Bret Barkelew <brbar...@microsoft.com>
> >
> > v6 changes:
> > * Fix an issue with uninitialized Status in InitVariablePolicyLib()
> > and
> > DeinitVariablePolicyLib()
> > * Fix GCC building in shell-based functional test
> > * Rebase on latest origin/master
> >
> > v5 changes:
> > * Fix the CONST mismatch in VariablePolicy.h and
> > VariablePolicySmmDxe.c
> > * Fix EFIAPI mismatches in the functional unittest
> > * Rebase on latest origin/master
> >
> > v4 changes:
> > * Remove Optional PcdAllowVariablePolicyEnforcementDisable PCD from
> > platforms
> > * Rebase on master
> > * Migrate to new MmCommunicate2 protocol
> > * Fix an oversight in the default return value for
> > InitMmCommonCommBuffer
> > * Fix in VariablePolicyLib to allow ExtraInitRuntimeDxe to consume
> > variables
> >
> > V3 changes:
> > * Address all non-unittest issues with ECC
> > * Make additional style changes
> > * Include section name in hunk headers in "ini-style" files
> > * Remove requirement for the EdkiiPiSmmCommunicationsRegionTable
> > driver
> >   (now allocates its own buffer)
> > * Change names from VARIABLE_POLICY_PROTOCOL and
> > gVariablePolicyProtocolGuid
> >   to EDKII_VARIABLE_POLICY_PROTOCOL and
> > gEdkiiVariablePolicyProtocolGuid
> > * Fix GCC warning about initializing externs
> > * Add UNI strings for new PCD
> > * Add patches for ArmVirtPkg, OvmfXen, and UefiPayloadPkg
> > * Reorder patches according to Liming's feedback about adding to
> platforms
> >   before changing variable driver
> >
> > V2 changes:
> > * Fixed implementation for RuntimeDxe
> > * Add PCD to block DisableVariablePolicy
> > * Fix the DumpVariablePolicy pagination in SMM
> >
> > Bret Barkelew (14):
> >   MdeModulePkg: Define the VariablePolicy protocol interface
> >   MdeModulePkg: Define the VariablePolicyLib
> >   MdeModulePkg: Define the VariablePolicyHelperLib
> >   MdeModulePkg: Define the VarCheckPolicyLib and SMM interface
> >   OvmfPkg: Add VariablePolicy engine to OvmfPkg platform
> >   EmulatorPkg: Add VariablePolicy engine to EmulatorPkg platform
> >   ArmVirtPkg: Add VariablePolicy engine to ArmVirtPkg platform
> >   UefiPayloadPkg: Add VariablePolicy engine to UefiPayloadPkg platform
> >   MdeModulePkg: Connect VariablePolicy business logic to
> >     VariableServices
> >   MdeModulePkg: Allow VariablePolicy state to delete protected variables
> >   SecurityPkg: Allow VariablePolicy state to delete authenticated
> >     variables
> >   MdeModulePkg: Change TCG MOR variables to use VariablePolicy
> >   MdeModulePkg: Drop VarLock from RuntimeDxe variable driver
> >   MdeModulePkg: Add a shell-based functional test for VariablePolicy
> >
> >  MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.c
> > |  320 +++
> >
> > MdeModulePkg/Library/VariablePolicyHelperLib/VariablePolicyHelperLib.c
> > |  396 ++++
> >  MdeModulePkg/Library/VariablePolicyLib/VariablePolicyExtraInitNull.c
> > |   46 +
> >
> >
> MdeModulePkg/Library/VariablePolicyLib/VariablePolicyExtraInitRuntimeDx
> > e.c               |   85 +
> >  MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLib.c
> > |  816 +++++++
> >
> >
> MdeModulePkg/Library/VariablePolicyLib/VariablePolicyUnitTest/VariablePo
> > licyUnitTest.c   | 2440 ++++++++++++++++++++
> >
> >
> MdeModulePkg/Test/ShellTest/VariablePolicyFuncTestApp/VariablePolicyFu
> > ncTestApp.c        | 1978 ++++++++++++++++
> >  MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockDxe.c
> > |   52 +-
> >  MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockSmm.c
> > |   60 +-
> >  MdeModulePkg/Universal/Variable/RuntimeDxe/VarCheck.c
> > |   49 +-
> >  MdeModulePkg/Universal/Variable/RuntimeDxe/VariableDxe.c
> > |   53 +
> >
> >
> MdeModulePkg/Universal/Variable/RuntimeDxe/VariableLockRequstToLock
> > .c                    |   71 +
> >  MdeModulePkg/Universal/Variable/RuntimeDxe/VariablePolicySmmDxe.c
> > |  642 +++++
> >
> >
> MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeDxe.
> > c                       |   14 +
> >  SecurityPkg/Library/AuthVariableLib/AuthService.c                          
> >               |
> 22
> > +-
> >  ArmVirtPkg/ArmVirt.dsc.inc                                                 
> >               |    4 +
> >  EmulatorPkg/EmulatorPkg.dsc                                                
> >               |    3 +
> >  MdeModulePkg/Include/Guid/VarCheckPolicyMmi.h
> |
> > 54 +
> >  MdeModulePkg/Include/Library/VariablePolicyHelperLib.h
> > |  164 ++
> >  MdeModulePkg/Include/Library/VariablePolicyLib.h                           
> >               |
> > 207 ++
> >  MdeModulePkg/Include/Protocol/VariablePolicy.h                             
> >               |
> > 157 ++
> >  MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.inf
> > |   42 +
> >  MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.uni
> > |   12 +
> >
> > MdeModulePkg/Library/VariablePolicyHelperLib/VariablePolicyHelperLib.i
> > nf
> > |   35 +
> >
> > MdeModulePkg/Library/VariablePolicyHelperLib/VariablePolicyHelperLib.u
> > ni
> > |   12 +
> >  MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLib.inf
> > |   44 +
> >  MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLib.uni
> > |   12 +
> >
> > MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLibRuntimeDxe.inf
> > |   51 +
> >
> >
> MdeModulePkg/Library/VariablePolicyLib/VariablePolicyUnitTest/VariablePo
> > licyUnitTest.inf |   40 +
> >  MdeModulePkg/MdeModulePkg.ci.yaml                                          
> >               |    4
> +-
> >  MdeModulePkg/MdeModulePkg.dec                                              
> >               |   26 +-
> >  MdeModulePkg/MdeModulePkg.dsc                                              
> >               |   15 +
> >  MdeModulePkg/MdeModulePkg.uni                                              
> >               |    7 +
> >  MdeModulePkg/Test/MdeModulePkgHostTest.dsc
> |
> > 11 +
> >  MdeModulePkg/Test/ShellTest/VariablePolicyFuncTestApp/Readme.md
> > |   55 +
> >
> >
> MdeModulePkg/Test/ShellTest/VariablePolicyFuncTestApp/VariablePolicyFu
> > ncTestApp.inf      |   42 +
> >  MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe.inf
> > |    5 +
> >  MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.inf
> > |    4 +
> >
> >
> MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeDxe.i
> > nf                     |   10 +
> >
> >
> MdeModulePkg/Universal/Variable/RuntimeDxe/VariableStandaloneMm.inf
> > |    4 +
> >  OvmfPkg/OvmfPkgIa32.dsc                                                    
> >               |    5 +
> >  OvmfPkg/OvmfPkgIa32X64.dsc                                                 
> >               |    5 +
> >  OvmfPkg/OvmfPkgX64.dsc                                                     
> >               |    5 +
> >  OvmfPkg/OvmfXen.dsc                                                        
> >               |    4 +
> >  SecurityPkg/Library/AuthVariableLib/AuthVariableLib.inf                    
> >               |
> > 2 +
> >  UefiPayloadPkg/UefiPayloadPkgIa32.dsc                                      
> >               |    4 +
> >  UefiPayloadPkg/UefiPayloadPkgIa32X64.dsc                                   
> >               |    4 +
> >  47 files changed, 8015 insertions(+), 78 deletions(-)  create mode
> > 100644 MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.c
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyHelperLib/VariablePolicyHelperLib.c
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyLib/VariablePolicyExtraInitNull.c
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyLib/VariablePolicyExtraInitRuntimeD
> > x
> > e.c
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLib.c
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyLib/VariablePolicyUnitTest/Variable
> > Po
> > licyUnitTest.c
> >  create mode 100644
> >
> MdeModulePkg/Test/ShellTest/VariablePolicyFuncTestApp/VariablePolicyFu
> > ncTestApp.c
> >  create mode 100644
> >
> MdeModulePkg/Universal/Variable/RuntimeDxe/VariableLockRequstToLock
> > .c
> >  create mode 100644
> > MdeModulePkg/Universal/Variable/RuntimeDxe/VariablePolicySmmDxe.c
> >  create mode 100644 MdeModulePkg/Include/Guid/VarCheckPolicyMmi.h
> >  create mode 100644
> > MdeModulePkg/Include/Library/VariablePolicyHelperLib.h
> >  create mode 100644 MdeModulePkg/Include/Library/VariablePolicyLib.h
> >  create mode 100644 MdeModulePkg/Include/Protocol/VariablePolicy.h
> >  create mode 100644
> > MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.inf
> >  create mode 100644
> > MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.uni
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyHelperLib/VariablePolicyHelperLib.i
> > nf
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyHelperLib/VariablePolicyHelperLib.u
> > ni
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLib.inf
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLib.uni
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyLib/VariablePolicyLibRuntimeDxe.inf
> >  create mode 100644
> > MdeModulePkg/Library/VariablePolicyLib/VariablePolicyUnitTest/Variable
> > Po
> > licyUnitTest.inf
> >  create mode 100644
> > MdeModulePkg/Test/ShellTest/VariablePolicyFuncTestApp/Readme.md
> >  create mode 100644
> >
> MdeModulePkg/Test/ShellTest/VariablePolicyFuncTestApp/VariablePolicyFu
> > ncTestApp.inf
> >
> > --
> > 2.26.2.windows.1.8.g01c50adf56.20200515075929
> >
> >
> >
>
>
>





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