REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1194
Speculative execution is used by processor to avoid having to wait for
data to arrive from memory, or for previous operations to finish, the
processor may speculate as to what will be executed.
If the speculation is incorrect, the speculatively executed instructions
might leave hints such as which memory locations have been brought into
cache. Malicious actors can use the bounds check bypass method (code
gadgets with controlled external inputs) to infer data values that have
been used in speculative operations to reveal secrets which should not
otherwise be accessed.
This commit will focus on the SMI handler(s) registered within the
Variable\RuntimeDxe driver and insert AsmLfence API to mitigate the
bounds check bypass issue.
For SMI handler SmmVariableHandler():
Under "case SMM_VARIABLE_FUNCTION_GET_VARIABLE:",
'SmmVariableHeader->NameSize' can be a potential cross boundary access of
the 'CommBuffer' (controlled external input) during speculative execution.
This cross boundary access is later used as the index to access array
'SmmVariableHeader->Name' by code:
"SmmVariableHeader->Name[SmmVariableHeader->NameSize/sizeof (CHAR16) - 1]"
One can observe which part of the content within array was brought into
cache to possibly reveal the value of 'SmmVariableHeader->NameSize'.
Hence, this commit adds a AsmLfence() after the boundary/range checks of
'CommBuffer' to prevent the speculative execution.
And there are 2 similar cases under
"case SMM_VARIABLE_FUNCTION_SET_VARIABLE:" and
"case SMM_VARIABLE_FUNCTION_VAR_CHECK_VARIABLE_PROPERTY_GET:" as well.
This commits also handles them.
Also, under "case SMM_VARIABLE_FUNCTION_SET_VARIABLE:",
'(UINT8 *)SmmVariableHeader->Name + SmmVariableHeader->NameSize' points to
the 'CommBuffer' (with some offset) and then passed as parameter 'Data' to
function VariableServiceSetVariable().
Within function VariableServiceSetVariable(), there is a sanity check for
EFI_VARIABLE_AUTHENTICATION_2 descriptor for the data pointed by 'Data'.
If this check is speculatively bypassed, potential cross-boundary data
access for 'Data' is possible to be revealed via the below function calls
sequence during speculative execution:
AuthVariableLibProcessVariable()
ProcessVarWithPk() or ProcessVarWithKek()
Within function ProcessVarWithPk() or ProcessVarWithKek(), for the code
"PayloadSize = DataSize - AUTHINFO2_SIZE (Data);", 'AUTHINFO2_SIZE (Data)'
can be a cross boundary access during speculative execution.
Then, 'PayloadSize' is possible to be revealed by the function call
sequence:
AuthServiceInternalUpdateVariableWithTimeStamp()
mAuthVarLibContextIn->UpdateVariable()
VariableExLibUpdateVariable()
UpdateVariable()
CopyMem()
Hence, this commit adds a AsmLfence() after the sanity check for
EFI_VARIABLE_AUTHENTICATION_2 descriptor upon 'Data' within function
VariableServiceSetVariable() to prevent the speculative execution.
Also, please note that the change made within function
VariableServiceSetVariable() will affect DXE as well. However, since we
only focuses on the SMM codes, the commit will introduce a new module
internal function called VariableLoadFence() to handle this. This internal
function will have 2 implementations (1 for SMM, 1 for DXE). For the SMM
implementation, it is a wrapper to call the AsmLfence() API; for the DXE
implementation, it is empty.
A more detailed explanation of the purpose of commit is under the
'Bounds check bypass mitigation' section of the below link:
https://software.intel.com/security-software-guidance/insights/host-firmware-speculative-execution-side-channel-mitigation
And the document at:
https://software.intel.com/security-software-guidance/api-app/sites/default/files/337879-analyzing-potential-bounds-Check-bypass-vulnerabilities.pdf
Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
(cherry picked from commit e83d841fdc)
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=290
Current SmmVariableGetStatistics() in VariableSmm.c is always
checking input InfoSize against the first variable info,
it is incorrect.
For instance, there are three variables.
BootOrder
Boot0000
Boot0001
If the input InfoEntry is holding the second variable info (Boot0000)
and InfoSize is sizeof (VARIABLE_INFO_ENTRY) + StrSize (L"Boot0000"),
current code will return EFI_BUFFER_TOO_SMALL, but it should return
the third variable info (Boot0001).
This patch is to refine the code logic.
Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Current code in SmmVariableHandler() checks CommBufferSize
buffer to make sure it points to outside SMRAM in
"case SMM_VARIABLE_FUNCTION_GET_STATISTICS".
But after eaae7b33b1,
CommBufferSize buffer points to SMRAM that was used by
SMM core to cache CommSize from SmmCommunication protocol,
then the check will fail definitely and GET_STATISTICS
feature breaks.
In fact, do not need check CommBufferSize buffer at all
even before eaae7b33b1.
Before eaae7b33b1,
CommBufferSize buffer pointed to gSmmCorePrivate->BufferSize
that is outside SMRAM, the check will success definitely;
after eaae7b33b1,
CommBufferSize buffer points to local variable BufferSize
(in SMRAM) in SmmEntryPoint(), the check is not needed
definitely.
The patch is to remove the check.
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jeff Fan <jeff.fan@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Instead of comparing a GUID with gZeroGuid via the CompareGuid API, the
commit uses the IsZeroGuid API to check if the given GUID is a zero GUID.
Cc: Feng Tian <feng.tian@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Feng Tian <feng.tian@Intel.com>
Since the variable check service has be separated to VarCheckLib
from Variable driver, so update Variable driver to consume the
separated VarCheckLib.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18286 6f19259b-4bc3-4df7-8a09-765794883524
What to do:
1. Merge from Auth Variable driver in SecurityPkg to Variable drive in
MdeModulePkg. Then the merged Variable driver in MdeModulePkg will
link to AuthVariableLib and TpmMeasurementLib.
AuthVariableLibNull and TpmMeasurementLibNull in MdeModulePkg
could be used for non auth variable support.
AuthVariableLib and DxeTpmMeasurementLib in SecurityPkg
may be used for auth variable support.
Why to do:
1. Remove code duplication and reduce maintenance effort.
After auth variable service separated from Auth Variable driver in SecurityPkg
to AuthVariableLib. The remaining code logic of Auth Variable driver in SecurityPkg
will be almost same with Variable driver in MdeModulePkg. Now it is to
merge them.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17765 6f19259b-4bc3-4df7-8a09-765794883524
As the drivers and library do not reference gEfiSmmAccess2ProtocolGuid explicitly now
after SmmMemLib introduced.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16760 6f19259b-4bc3-4df7-8a09-765794883524
2. Add check to ensure CommBufferPayloadSize not exceed mVariableBufferPayloadSize or is enough to hold function structure in VariableSmm and FtwSmm.
3. Align FtwGetLastWrite() in FaultTolerantWriteSmmDxe.c to FtwGetLastWrite() in FaultTolerantWrite.c.
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14325 6f19259b-4bc3-4df7-8a09-765794883524
