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Re: [PATCH v6 00/14] Add the VariablePolicy feature

Dandan Bi
 

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?

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.

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.

3. Did you do any security test for this feature?

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?

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?


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; bret@...
Cc: Yao, Jiewen <jiewen.yao@...>; Zhang, Chao B
<chao.b.zhang@...>; Wang, Jian J <jian.j.wang@...>; Wu, Hao
A <hao.a.wu@...>; Gao, Liming <liming.gao@...>; Justen,
Jordan L <jordan.l.justen@...>; Laszlo Ersek <lersek@...>;
Ard Biesheuvel <ard.biesheuvel@...>; Andrew Fish
<afish@...>; Ni, Ray <ray.ni@...>
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.yao@...>; Zhang, Chao B
<chao.b.zhang@...>; Wang, Jian J <jian.j.wang@...>; Wu,
Hao A <hao.a.wu@...>; Gao, Liming <liming.gao@...>;
Justen, Jordan L <jordan.l.justen@...>; Laszlo Ersek
<lersek@...>; Ard Biesheuvel <ard.biesheuvel@...>;
Andrew
Fish <afish@...>; Ni, Ray <ray.ni@...>
Subject: [edk2-devel] [PATCH v6 00/14] Add the VariablePolicy feature

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2522

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://github.com/tianocore/tianocore.github.io/wiki/VariablePolicy-
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://edk2.groups.io/g/devel/message/53712
(the code branches shared in that discussion are now out of date, but
the whitepapers and discussion are relevant).

Cc: Jiewen Yao <jiewen.yao@...>
Cc: Chao Zhang <chao.b.zhang@...>
Cc: Jian J Wang <jian.j.wang@...>
Cc: Hao A Wu <hao.a.wu@...>
Cc: Liming Gao <liming.gao@...>
Cc: Jordan Justen <jordan.l.justen@...>
Cc: Laszlo Ersek <lersek@...>
Cc: Ard Biesheuvel <ard.biesheuvel@...>
Cc: Andrew Fish <afish@...>
Cc: Ray Ni <ray.ni@...>
Cc: Bret Barkelew <brbarkel@...>
Signed-off-by: Bret Barkelew <brbarkel@...>

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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