From 47343af30435302c087027177613412a1a83e919 Mon Sep 17 00:00:00 2001 From: Laszlo Ersek Date: Thu, 19 Nov 2020 11:53:40 +0100 Subject: MdeModulePkg/Core/Dxe: limit FwVol encapsulation section recursion MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The DXE Core sets up a protocol notify function in its entry point, for instances of the Firmware Volume Block2 Protocol: DxeMain() [DxeMain/DxeMain.c] FwVolDriverInit() [FwVol/FwVol.c] Assume that a 3rd party UEFI driver or application installs an FVB instance, with crafted contents. The notification function runs: NotifyFwVolBlock() [FwVol/FwVol.c] installing an instance of the Firmware Volume 2 Protocol on the handle. (Alternatively, assume that a 3rd party application calls gDS->ProcessFirmwareVolume(), which may also produce a Firmware Volume 2 Protocol instance.) The EFI_FIRMWARE_VOLUME2_PROTOCOL.ReadSection() member performs "a depth-first, left-to-right search algorithm through all sections found in the specified file" (quoting the PI spec), as follows: FvReadFileSection() [FwVol/FwVolRead.c] GetSection() [SectionExtraction/CoreSectionExtraction.c] FindChildNode() [SectionExtraction/CoreSectionExtraction.c] FindChildNode() // recursive call FindChildNode() is called recursively for encapsulation sections. Currently this recursion is not limited. Introduce a new PCD (fixed-at-build, or patchable-in-module), and make FindChildNode() track the section nesting depth against that PCD. Cc: Dandan Bi Cc: Hao A Wu Cc: Jian J Wang Cc: Liming Gao Cc: Philippe Mathieu-Daudé Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1743 Signed-off-by: Laszlo Ersek Reviewed-by: Liming Gao Reviewed-by: Philippe Mathieu-Daudé Message-Id: <20201119105340.16225-3-lersek@redhat.com> --- MdeModulePkg/Core/Dxe/DxeMain.inf | 1 + .../Dxe/SectionExtraction/CoreSectionExtraction.c | 33 ++++++++++++++++++++-- MdeModulePkg/MdeModulePkg.dec | 6 ++++ MdeModulePkg/MdeModulePkg.uni | 6 ++++ 4 files changed, 44 insertions(+), 2 deletions(-) diff --git a/MdeModulePkg/Core/Dxe/DxeMain.inf b/MdeModulePkg/Core/Dxe/DxeMain.inf index 1d4b11dc73..e4bca89577 100644 --- a/MdeModulePkg/Core/Dxe/DxeMain.inf +++ b/MdeModulePkg/Core/Dxe/DxeMain.inf @@ -185,6 +185,7 @@ gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPoolType ## CONSUMES gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPropertyMask ## CONSUMES gEfiMdeModulePkgTokenSpaceGuid.PcdCpuStackGuard ## CONSUMES + gEfiMdeModulePkgTokenSpaceGuid.PcdFwVolDxeMaxEncapsulationDepth ## CONSUMES # [Hob] # RESOURCE_DESCRIPTOR ## CONSUMES diff --git a/MdeModulePkg/Core/Dxe/SectionExtraction/CoreSectionExtraction.c b/MdeModulePkg/Core/Dxe/SectionExtraction/CoreSectionExtraction.c index d7f7ef4274..908617d1ca 100644 --- a/MdeModulePkg/Core/Dxe/SectionExtraction/CoreSectionExtraction.c +++ b/MdeModulePkg/Core/Dxe/SectionExtraction/CoreSectionExtraction.c @@ -955,6 +955,9 @@ CreateChildNode ( This is an in/out parameter and it is 1-based, to deal with recursions. @param SectionDefinitionGuid Guid of section definition + @param Depth Nesting depth of encapsulation sections. + Callers different from FindChildNode() are + responsible for passing in a zero Depth. @param FoundChild Output indicating the child node that is found. @param FoundStream Output indicating which section stream the child was found in. If this stream was generated as a @@ -968,6 +971,9 @@ CreateChildNode ( @retval EFI_NOT_FOUND Requested child node does not exist. @retval EFI_PROTOCOL_ERROR a required GUIDED section extraction protocol does not exist + @retval EFI_ABORTED Recursion aborted because Depth has been + greater than or equal to + PcdFwVolDxeMaxEncapsulationDepth. **/ EFI_STATUS @@ -976,6 +982,7 @@ FindChildNode ( IN EFI_SECTION_TYPE SearchType, IN OUT UINTN *SectionInstance, IN EFI_GUID *SectionDefinitionGuid, + IN UINT32 Depth, OUT CORE_SECTION_CHILD_NODE **FoundChild, OUT CORE_SECTION_STREAM_NODE **FoundStream, OUT UINT32 *AuthenticationStatus @@ -990,6 +997,10 @@ FindChildNode ( ASSERT (*SectionInstance > 0); + if (Depth >= PcdGet32 (PcdFwVolDxeMaxEncapsulationDepth)) { + return EFI_ABORTED; + } + CurrentChildNode = NULL; ErrorStatus = EFI_NOT_FOUND; @@ -1053,6 +1064,7 @@ FindChildNode ( SearchType, SectionInstance, SectionDefinitionGuid, + Depth + 1, &RecursedChildNode, &RecursedFoundStream, AuthenticationStatus @@ -1067,9 +1079,17 @@ FindChildNode ( *FoundStream = RecursedFoundStream; return EFI_SUCCESS; } else { + if (Status == EFI_ABORTED) { + // + // If the recursive call was aborted due to nesting depth, stop + // looking for the requested child node. The skipped subtree could + // throw off the instance counting. + // + return Status; + } // - // If the status is not EFI_SUCCESS, just save the error code and - // continue to find the request child node in the rest stream. + // Save the error code and continue to find the requested child node in + // the rest of the stream. // ErrorStatus = Status; } @@ -1272,11 +1292,20 @@ GetSection ( *SectionType, &Instance, SectionDefinitionGuid, + 0, // encapsulation depth &ChildNode, &ChildStreamNode, &ExtractedAuthenticationStatus ); if (EFI_ERROR (Status)) { + if (Status == EFI_ABORTED) { + DEBUG ((DEBUG_ERROR, "%a: recursion aborted due to nesting depth\n", + __FUNCTION__)); + // + // Map "aborted" to "not found". + // + Status = EFI_NOT_FOUND; + } goto GetSection_Done; } diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec index 0007552819..9b52b34494 100644 --- a/MdeModulePkg/MdeModulePkg.dec +++ b/MdeModulePkg/MdeModulePkg.dec @@ -1529,6 +1529,12 @@ # @Prompt Enable Capsule On Disk support. gEfiMdeModulePkgTokenSpaceGuid.PcdCapsuleOnDiskSupport|FALSE|BOOLEAN|0x0000002d + ## Maximum permitted encapsulation levels of sections in a firmware volume, + # in the DXE phase. Minimum value is 1. Sections nested more deeply are + # rejected. + # @Prompt Maximum permitted FwVol section nesting depth (exclusive). + gEfiMdeModulePkgTokenSpaceGuid.PcdFwVolDxeMaxEncapsulationDepth|0x10|UINT32|0x00000030 + [PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx] ## This PCD defines the Console output row. The default value is 25 according to UEFI spec. # This PCD could be set to 0 then console output would be at max column and max row. diff --git a/MdeModulePkg/MdeModulePkg.uni b/MdeModulePkg/MdeModulePkg.uni index 40884c57a4..1b347a75f6 100644 --- a/MdeModulePkg/MdeModulePkg.uni +++ b/MdeModulePkg/MdeModulePkg.uni @@ -1160,6 +1160,12 @@ "Note:
" "If Both Capsule In Ram and Capsule On Disk are provisioned at the same time, the Capsule On Disk will be bypassed." +#string STR_gEfiMdeModulePkgTokenSpaceGuid_PcdFwVolDxeMaxEncapsulationDepth_PROMPT #language en-US "Maximum permitted FwVol section nesting depth (exclusive)." + +#string STR_gEfiMdeModulePkgTokenSpaceGuid_PcdFwVolDxeMaxEncapsulationDepth_HELP #language en-US "Maximum permitted encapsulation levels of sections in a firmware volume,
" + "in the DXE phase. Minimum value is 1. Sections nested more deeply are
" + "rejected." + #string STR_gEfiMdeModulePkgTokenSpaceGuid_PcdCapsuleInRamSupport_PROMPT #language en-US "Enable Capsule In Ram support" #string STR_gEfiMdeModulePkgTokenSpaceGuid_PcdCapsuleInRamSupport_HELP #language en-US "Capsule In Ram is to use memory to deliver the capsules that will be processed after system reset.

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