diff options
Diffstat (limited to 'src/VBox/Devices/EFI/Firmware/MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.c')
-rw-r--r-- | src/VBox/Devices/EFI/Firmware/MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.c | 345 |
1 files changed, 345 insertions, 0 deletions
diff --git a/src/VBox/Devices/EFI/Firmware/MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.c b/src/VBox/Devices/EFI/Firmware/MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.c new file mode 100644 index 00000000..38a05d34 --- /dev/null +++ b/src/VBox/Devices/EFI/Firmware/MdeModulePkg/Library/VarCheckPolicyLib/VarCheckPolicyLib.c @@ -0,0 +1,345 @@ +/** @file -- VarCheckPolicyLib.c +This is a NULL library instance that leverages the VarCheck interface +and the business logic behind the VariablePolicy code to make its decisions. + +Copyright (c) Microsoft Corporation. +SPDX-License-Identifier: BSD-2-Clause-Patent + +**/ + +#include <Library/VarCheckLib.h> +#include <Library/BaseLib.h> +#include <Library/DebugLib.h> +#include <Library/SafeIntLib.h> +#include <Library/MmServicesTableLib.h> +#include <Library/BaseMemoryLib.h> +#include <Library/MemoryAllocationLib.h> + +#include <Protocol/MmCommunication.h> + +#include <Protocol/VariablePolicy.h> +#include <Library/VariablePolicyLib.h> + +#include <Guid/VarCheckPolicyMmi.h> + +#include "VarCheckPolicyLib.h" + +//================================================ +// As a VarCheck library, we're linked into the VariableServices +// and may not be able to call them indirectly. To get around this, +// use the internal GetVariable function to query the variable store. +//================================================ +EFI_STATUS +EFIAPI +VariableServiceGetVariable ( + IN CHAR16 *VariableName, + IN EFI_GUID *VendorGuid, + OUT UINT32 *Attributes OPTIONAL, + IN OUT UINTN *DataSize, + OUT VOID *Data + ); + + +UINT8 mSecurityEvalBuffer[VAR_CHECK_POLICY_MM_COMM_BUFFER_SIZE]; + +// Pagination Cache Variables +UINT8 *mPaginationCache = NULL; +UINTN mPaginationCacheSize = 0; +UINT32 mCurrentPaginationCommand = 0; + + +/** + MM Communication Handler to recieve commands from the DXE protocol for + Variable Policies. This communication channel is used to register new policies + and poll and toggle the enforcement of variable policies. + + @param[in] DispatchHandle All parameters standard to MM communications convention. + @param[in] RegisterContext All parameters standard to MM communications convention. + @param[in,out] CommBuffer All parameters standard to MM communications convention. + @param[in,out] CommBufferSize All parameters standard to MM communications convention. + + @retval EFI_SUCCESS + @retval EFI_INVALID_PARAMETER CommBuffer or CommBufferSize is null pointer. + @retval EFI_INVALID_PARAMETER CommBuffer size is wrong. + @retval EFI_INVALID_PARAMETER Revision or signature don't match. + +**/ +STATIC +EFI_STATUS +EFIAPI +VarCheckPolicyLibMmiHandler ( + IN EFI_HANDLE DispatchHandle, + IN CONST VOID *RegisterContext, + IN OUT VOID *CommBuffer, + IN OUT UINTN *CommBufferSize + ) +{ + UINTN InternalCommBufferSize; + VOID *InternalCommBuffer; + EFI_STATUS Status; + EFI_STATUS SubCommandStatus; + VAR_CHECK_POLICY_COMM_HEADER *PolicyCommmHeader; + VAR_CHECK_POLICY_COMM_HEADER *InternalPolicyCommmHeader; + VAR_CHECK_POLICY_COMM_IS_ENABLED_PARAMS *IsEnabledParams; + VAR_CHECK_POLICY_COMM_DUMP_PARAMS *DumpParamsIn; + VAR_CHECK_POLICY_COMM_DUMP_PARAMS *DumpParamsOut; + UINT8 *DumpInputBuffer; + UINT8 *DumpOutputBuffer; + UINTN DumpTotalPages; + VARIABLE_POLICY_ENTRY *PolicyEntry; + UINTN ExpectedSize; + UINT32 TempSize; + + Status = EFI_SUCCESS; + + // + // Validate some input parameters. + // + // If either of the pointers are NULL, we can't proceed. + if (CommBuffer == NULL || CommBufferSize == NULL) { + DEBUG(( DEBUG_INFO, "%a - Invalid comm buffer pointers!\n", __FUNCTION__ )); + return EFI_INVALID_PARAMETER; + } + // Make sure that the buffer does not overlap SMM. + // This should be covered by the SmiManage infrastructure, but just to be safe... + InternalCommBufferSize = *CommBufferSize; + if (InternalCommBufferSize > VAR_CHECK_POLICY_MM_COMM_BUFFER_SIZE || + !VarCheckPolicyIsBufferOutsideValid((UINTN)CommBuffer, (UINT64)InternalCommBufferSize)) { + DEBUG ((DEBUG_ERROR, "%a - Invalid CommBuffer supplied! 0x%016lX[0x%016lX]\n", __FUNCTION__, CommBuffer, InternalCommBufferSize)); + return EFI_INVALID_PARAMETER; + } + // If the size does not meet a minimum threshold, we cannot proceed. + ExpectedSize = sizeof(VAR_CHECK_POLICY_COMM_HEADER); + if (InternalCommBufferSize < ExpectedSize) { + DEBUG(( DEBUG_INFO, "%a - Bad comm buffer size! %d < %d\n", __FUNCTION__, InternalCommBufferSize, ExpectedSize )); + return EFI_INVALID_PARAMETER; + } + + // + // Before proceeding any further, copy the buffer internally so that we can compare + // without worrying about TOCTOU. + // + InternalCommBuffer = &mSecurityEvalBuffer[0]; + CopyMem(InternalCommBuffer, CommBuffer, InternalCommBufferSize); + PolicyCommmHeader = CommBuffer; + InternalPolicyCommmHeader = InternalCommBuffer; + // Check the revision and the signature of the comm header. + if (InternalPolicyCommmHeader->Signature != VAR_CHECK_POLICY_COMM_SIG || + InternalPolicyCommmHeader->Revision != VAR_CHECK_POLICY_COMM_REVISION) { + DEBUG(( DEBUG_INFO, "%a - Signature or revision are incorrect!\n", __FUNCTION__ )); + // We have verified the buffer is not null and have enough size to hold Result field. + PolicyCommmHeader->Result = EFI_INVALID_PARAMETER; + return EFI_SUCCESS; + } + + // If we're in the middle of a paginated dump and any other command is sent, + // pagination cache must be cleared. + if (mPaginationCache != NULL && InternalPolicyCommmHeader->Command != mCurrentPaginationCommand) { + FreePool (mPaginationCache); + mPaginationCache = NULL; + mPaginationCacheSize = 0; + mCurrentPaginationCommand = 0; + } + + // + // Now we can process the command as it was sent. + // + PolicyCommmHeader->Result = EFI_ABORTED; // Set a default return for incomplete commands. + switch(InternalPolicyCommmHeader->Command) { + case VAR_CHECK_POLICY_COMMAND_DISABLE: + PolicyCommmHeader->Result = DisableVariablePolicy(); + break; + + case VAR_CHECK_POLICY_COMMAND_IS_ENABLED: + // Make sure that we're dealing with a reasonable size. + // This add should be safe because these are fixed sizes so far. + ExpectedSize += sizeof(VAR_CHECK_POLICY_COMM_IS_ENABLED_PARAMS); + if (InternalCommBufferSize < ExpectedSize) { + DEBUG(( DEBUG_INFO, "%a - Bad comm buffer size! %d < %d\n", __FUNCTION__, InternalCommBufferSize, ExpectedSize )); + PolicyCommmHeader->Result = EFI_INVALID_PARAMETER; + break; + } + + // Now that we know we've got a valid size, we can fill in the rest of the data. + IsEnabledParams = (VAR_CHECK_POLICY_COMM_IS_ENABLED_PARAMS*)((UINT8*)CommBuffer + sizeof(VAR_CHECK_POLICY_COMM_HEADER)); + IsEnabledParams->State = IsVariablePolicyEnabled(); + PolicyCommmHeader->Result = EFI_SUCCESS; + break; + + case VAR_CHECK_POLICY_COMMAND_REGISTER: + // Make sure that we're dealing with a reasonable size. + // This add should be safe because these are fixed sizes so far. + ExpectedSize += sizeof(VARIABLE_POLICY_ENTRY); + if (InternalCommBufferSize < ExpectedSize) { + DEBUG(( DEBUG_INFO, "%a - Bad comm buffer size! %d < %d\n", __FUNCTION__, InternalCommBufferSize, ExpectedSize )); + PolicyCommmHeader->Result = EFI_INVALID_PARAMETER; + break; + } + + // At the very least, we can assume that we're working with a valid policy entry. + // Time to compare its internal size. + PolicyEntry = (VARIABLE_POLICY_ENTRY*)((UINT8*)InternalCommBuffer + sizeof(VAR_CHECK_POLICY_COMM_HEADER)); + if (PolicyEntry->Version != VARIABLE_POLICY_ENTRY_REVISION || + PolicyEntry->Size < sizeof(VARIABLE_POLICY_ENTRY) || + EFI_ERROR(SafeUintnAdd(sizeof(VAR_CHECK_POLICY_COMM_HEADER), PolicyEntry->Size, &ExpectedSize)) || + InternalCommBufferSize < ExpectedSize) { + DEBUG(( DEBUG_INFO, "%a - Bad policy entry contents!\n", __FUNCTION__ )); + PolicyCommmHeader->Result = EFI_INVALID_PARAMETER; + break; + } + + PolicyCommmHeader->Result = RegisterVariablePolicy( PolicyEntry ); + break; + + case VAR_CHECK_POLICY_COMMAND_DUMP: + // Make sure that we're dealing with a reasonable size. + // This add should be safe because these are fixed sizes so far. + ExpectedSize += sizeof(VAR_CHECK_POLICY_COMM_DUMP_PARAMS) + VAR_CHECK_POLICY_MM_DUMP_BUFFER_SIZE; + if (InternalCommBufferSize < ExpectedSize) { + DEBUG(( DEBUG_INFO, "%a - Bad comm buffer size! %d < %d\n", __FUNCTION__, InternalCommBufferSize, ExpectedSize )); + PolicyCommmHeader->Result = EFI_INVALID_PARAMETER; + break; + } + + // Now that we know we've got a valid size, we can fill in the rest of the data. + DumpParamsIn = (VAR_CHECK_POLICY_COMM_DUMP_PARAMS*)(InternalPolicyCommmHeader + 1); + DumpParamsOut = (VAR_CHECK_POLICY_COMM_DUMP_PARAMS*)(PolicyCommmHeader + 1); + + // If we're requesting the first page, initialize the cache and get the sizes. + if (DumpParamsIn->PageRequested == 0) { + if (mPaginationCache != NULL) { + FreePool (mPaginationCache); + mPaginationCache = NULL; + } + + // Determine what the required size is going to be. + DumpParamsOut->TotalSize = 0; + DumpParamsOut->PageSize = 0; + DumpParamsOut->HasMore = FALSE; + TempSize = 0; + SubCommandStatus = DumpVariablePolicy (NULL, &TempSize); + if (SubCommandStatus == EFI_BUFFER_TOO_SMALL && TempSize > 0) { + mCurrentPaginationCommand = VAR_CHECK_POLICY_COMMAND_DUMP; + mPaginationCacheSize = TempSize; + DumpParamsOut->TotalSize = TempSize; + mPaginationCache = AllocatePool (mPaginationCacheSize); + if (mPaginationCache == NULL) { + SubCommandStatus = EFI_OUT_OF_RESOURCES; + } + } + + // If we've allocated our pagination cache, we're good to cache. + if (mPaginationCache != NULL) { + SubCommandStatus = DumpVariablePolicy (mPaginationCache, &TempSize); + } + + // Populate the remaining fields and we can boogie. + if (!EFI_ERROR (SubCommandStatus) && mPaginationCache != NULL) { + DumpParamsOut->HasMore = TRUE; + } + } else if (mPaginationCache != NULL) { + DumpParamsOut->TotalSize = (UINT32)mPaginationCacheSize; + DumpOutputBuffer = (UINT8*)(DumpParamsOut + 1); + + // Make sure that we don't over-index the cache. + DumpTotalPages = mPaginationCacheSize / VAR_CHECK_POLICY_MM_DUMP_BUFFER_SIZE; + if (mPaginationCacheSize % VAR_CHECK_POLICY_MM_DUMP_BUFFER_SIZE != 0) { + DumpTotalPages++; + } + if (DumpParamsIn->PageRequested > DumpTotalPages) { + SubCommandStatus = EFI_INVALID_PARAMETER; + } else { + // Figure out how far into the page cache we need to go for our next page. + // We know the blind subtraction won't be bad because we already checked for page 0. + DumpInputBuffer = &mPaginationCache[VAR_CHECK_POLICY_MM_DUMP_BUFFER_SIZE * (DumpParamsIn->PageRequested - 1)]; + TempSize = VAR_CHECK_POLICY_MM_DUMP_BUFFER_SIZE; + // If we're getting the last page, adjust the PageSize. + if (DumpParamsIn->PageRequested == DumpTotalPages) { + TempSize = mPaginationCacheSize % VAR_CHECK_POLICY_MM_DUMP_BUFFER_SIZE; + } + CopyMem (DumpOutputBuffer, DumpInputBuffer, TempSize); + DumpParamsOut->PageSize = TempSize; + // If we just got the last page, settle up the cache. + if (DumpParamsIn->PageRequested == DumpTotalPages) { + DumpParamsOut->HasMore = FALSE; + FreePool (mPaginationCache); + mPaginationCache = NULL; + mPaginationCacheSize = 0; + mCurrentPaginationCommand = 0; + // Otherwise, we could do more here. + } else { + DumpParamsOut->HasMore = TRUE; + } + + // If we made it this far, we're basically good. + SubCommandStatus = EFI_SUCCESS; + } + // If we've requested any other page than 0 and the cache is empty, we must have timed out. + } else { + DumpParamsOut->TotalSize = 0; + DumpParamsOut->PageSize = 0; + DumpParamsOut->HasMore = FALSE; + SubCommandStatus = EFI_TIMEOUT; + } + + // There's currently no use for this, but it shouldn't be hard to implement. + PolicyCommmHeader->Result = SubCommandStatus; + break; + + case VAR_CHECK_POLICY_COMMAND_LOCK: + PolicyCommmHeader->Result = LockVariablePolicy(); + break; + + default: + // Mark unknown requested command as EFI_UNSUPPORTED. + DEBUG(( DEBUG_INFO, "%a - Invalid command requested! %d\n", __FUNCTION__, PolicyCommmHeader->Command )); + PolicyCommmHeader->Result = EFI_UNSUPPORTED; + break; + } + + DEBUG(( DEBUG_VERBOSE, "%a - Command %d returning %r.\n", __FUNCTION__, + PolicyCommmHeader->Command, PolicyCommmHeader->Result )); + + return Status; +} + + +/** + Constructor function of VarCheckPolicyLib to register VarCheck handler and + SW MMI handlers. + + @retval EFI_SUCCESS The constructor executed correctly. + +**/ +EFI_STATUS +EFIAPI +VarCheckPolicyLibCommonConstructor ( + VOID + ) +{ + EFI_STATUS Status; + EFI_HANDLE DiscardedHandle; + + // Initialize the business logic with the internal GetVariable handler. + Status = InitVariablePolicyLib( VariableServiceGetVariable ); + + // Only proceed with init if the business logic could be initialized. + if (!EFI_ERROR( Status )) { + // Register the VarCheck handler for SetVariable filtering. + // Forward the check to the business logic of the library. + VarCheckLibRegisterSetVariableCheckHandler( ValidateSetVariable ); + + // Register the MMI handlers for receiving policy commands. + DiscardedHandle = NULL; + Status = gMmst->MmiHandlerRegister( VarCheckPolicyLibMmiHandler, + &gVarCheckPolicyLibMmiHandlerGuid, + &DiscardedHandle ); + } + // Otherwise, there's not much we can do. + else { + DEBUG(( DEBUG_ERROR, "%a - Cannot Initialize VariablePolicyLib! %r\n", __FUNCTION__, Status )); + ASSERT_EFI_ERROR( Status ); + } + + return Status; +} |