OvmfPkg: Sec: assert the build-time calculated end of the scratch buffer

The DecompressMemFvs() function in "OvmfPkg/Sec/SecMain.c" uses more
memory, temporarily, than what PEIFV and DXEFV will ultimately need.
First, it uses an output buffer for decompression, second, the
decompression itself needs a scratch buffer (and this scratch buffer is
the highest area that SEC uses).

DecompressMemFvs() used to be called on normal boots only (ie. not on S3
resume), which is why the decompression output buffer and the scratch
buffer were allowed to scribble over RAM. However, we'll soon start to
worry during S3 resume that the runtime OS might tamper with the
pre-decompressed PEIFV, and we'll decompress the firmware volumes on S3
resume too, from pristine flash. For this we'll need to know the end of
the scratch buffer in advance, so we can prepare a non-malicious OS for
it.

Calculate the end of the scratch buffer statically in the FDF files, and
assert in DecompressMemFvs() that the runtime decompression will match it.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19036 6f19259b-4bc3-4df7-8a09-765794883524

8 files changed, 93 insertions, 3 deletions

diff --git a/OvmfPkg/DecomprScratchEnd.fdf.inc b/OvmfPkg/DecomprScratchEnd.fdf.inc
new file mode 100644
index 0000000000..eb5cd49470
--- /dev/null
+++ b/OvmfPkg/DecomprScratchEnd.fdf.inc
@@ -0,0 +1,72 @@
+## @file

+#  This FDF include file computes the end of the scratch buffer used in

+#  DecompressMemFvs() [OvmfPkg/Sec/SecMain.c]. It is based on the decompressed

+#  (ie. original) size of the LZMA-compressed section of the one FFS file in

+#  the FVMAIN_COMPACT firmware volume.

+#

+#  Copyright (C) 2015, Red Hat, Inc.

+#

+#  This program and the accompanying materials are licensed and made available

+#  under the terms and conditions of the BSD License which accompanies this

+#  distribution. The full text of the license may be found at

+#  http://opensource.org/licenses/bsd-license.php

+#

+#  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,

+#  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR

+#  IMPLIED.

+##

+

+# The GUID EE4E5898-3914-4259-9D6E-DC7BD79403CF means "LzmaCustomDecompress".

+# The decompressed output will have the following structure (see the file

+# "9E21FD93-9C72-4c15-8C4B-E77F1DB2D792SEC1.guided.dummy" in the

+# Build/Ovmf*/*/FV/Ffs/9E21FD93-9C72-4c15-8C4B-E77F1DB2D792/ directory):

+#

+# Size                 Contents

+# -------------------  --------------------------------------------------------

+#                   4  EFI_COMMON_SECTION_HEADER, stating size 124 (0x7C) and

+#                      type 0x19 (EFI_SECTION_RAW). The purpose of this section

+#                      is to pad the start of PEIFV to 128 bytes.

+#                 120  Zero bytes (padding).

+#

+#                   4  EFI_COMMON_SECTION_HEADER, stating size

+#                      (PcdOvmfPeiMemFvSize + 4), and type 0x17

+#                      (EFI_SECTION_FIRMWARE_VOLUME_IMAGE).

+# PcdOvmfPeiMemFvSize  PEIFV. Note that the above sizes pad the offset of this

+#                      object to 128 bytes. See also the "guided.dummy.txt"

+#                      file in the same directory.

+#

+#                   4  EFI_COMMON_SECTION_HEADER, stating size 12 (0xC) and

+#                      type 0x19 (EFI_SECTION_RAW). The purpose of this section

+#                      is to pad the start of DXEFV to 16 bytes.

+#                   8  Zero bytes (padding).

+#

+#                   4  EFI_COMMON_SECTION_HEADER, stating size

+#                      (PcdOvmfDxeMemFvSize + 4), and type 0x17

+#                      (EFI_SECTION_FIRMWARE_VOLUME_IMAGE).

+# PcdOvmfDxeMemFvSize  DXEFV. Note that the above sizes pad the offset of this

+#                      object to 16 bytes. See also the "guided.dummy.txt" file

+#                      in the same directory.

+#

+# The total size after decompression is (128 + PcdOvmfPeiMemFvSize + 16 +

+# PcdOvmfDxeMemFvSize).

+

+DEFINE OUTPUT_SIZE = (128 + gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvSize + 16 + gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDxeMemFvSize)

+

+# LzmaCustomDecompressLib uses a constant scratch buffer size of 64KB; see

+# SCRATCH_BUFFER_REQUEST_SIZE in

+# "MdeModulePkg/Library/LzmaCustomDecompressLib/LzmaDecompress.c".

+

+DEFINE DECOMP_SCRATCH_SIZE = 0x00010000

+

+# Note: when we use PcdOvmfDxeMemFvBase in this context, BaseTools have not yet

+# offset it with MEMFD's base address. For that reason we have to do it manually.

+#

+# The calculation below mirrors DecompressMemFvs() [OvmfPkg/Sec/SecMain.c].

+

+DEFINE OUTPUT_BASE                   = ($(MEMFD_BASE_ADDRESS) + gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDxeMemFvBase + 0x00100000)

+DEFINE DECOMP_SCRATCH_BASE_UNALIGNED = ($(OUTPUT_BASE) + $(OUTPUT_SIZE))

+DEFINE DECOMP_SCRATCH_BASE_ALIGNMENT = 0x000FFFFF

+DEFINE DECOMP_SCRATCH_BASE_MASK      = 0xFFF00000

+DEFINE DECOMP_SCRATCH_BASE           = (($(DECOMP_SCRATCH_BASE_UNALIGNED) + $(DECOMP_SCRATCH_BASE_ALIGNMENT)) & $(DECOMP_SCRATCH_BASE_MASK))

+

+SET gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd = $(DECOMP_SCRATCH_BASE) + $(DECOMP_SCRATCH_SIZE)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 47b0e69629..1c9f8312b5 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -106,6 +106,7 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfLockBoxStorageBase|0x0|UINT32|0x18

   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfLockBoxStorageSize|0x0|UINT32|0x19

   gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize|0x0|UINT32|0x1a

+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd|0x0|UINT32|0x1f

 

 [PcdsDynamic, PcdsDynamicEx]

   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2

diff --git a/OvmfPkg/OvmfPkg.fdf.inc b/OvmfPkg/OvmfPkg.fdf.inc
index 486bbc61ea..441c35acfa 100644
--- a/OvmfPkg/OvmfPkg.fdf.inc
+++ b/OvmfPkg/OvmfPkg.fdf.inc
@@ -60,3 +60,5 @@ SET gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingSize = $(BLOCK_SIZ
 

 SET gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashNvStorageFtwSpareBase = gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashNvStorageFtwWorkingBase + gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingSize

 SET gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize = 0x10000

+

+DEFINE MEMFD_BASE_ADDRESS = 0x800000

diff --git a/OvmfPkg/OvmfPkgIa32.fdf b/OvmfPkg/OvmfPkgIa32.fdf
index d4ae2f98ac..30bd3bc79f 100644
--- a/OvmfPkg/OvmfPkgIa32.fdf
+++ b/OvmfPkg/OvmfPkgIa32.fdf
@@ -78,7 +78,7 @@ FV = SECFV
 ################################################################################

 

 [FD.MEMFD]

-BaseAddress   = 0x800000

+BaseAddress   = $(MEMFD_BASE_ADDRESS)

 Size          = 0xA00000

 ErasePolarity = 1

 BlockSize     = 0x10000

@@ -384,6 +384,8 @@ FILE FV_IMAGE = 9E21FD93-9C72-4c15-8C4B-E77F1DB2D792 {
    }

  }

 

+!include DecomprScratchEnd.fdf.inc

+

 ################################################################################

 

 [Rule.Common.SEC]

diff --git a/OvmfPkg/OvmfPkgIa32X64.fdf b/OvmfPkg/OvmfPkgIa32X64.fdf
index 5b4d9dc464..59c3362950 100644
--- a/OvmfPkg/OvmfPkgIa32X64.fdf
+++ b/OvmfPkg/OvmfPkgIa32X64.fdf
@@ -78,7 +78,7 @@ FV = SECFV
 ################################################################################

 

 [FD.MEMFD]

-BaseAddress   = 0x800000

+BaseAddress   = $(MEMFD_BASE_ADDRESS)

 Size          = 0xA00000

 ErasePolarity = 1

 BlockSize     = 0x10000

@@ -384,6 +384,8 @@ FILE FV_IMAGE = 9E21FD93-9C72-4c15-8C4B-E77F1DB2D792 {
    }

  }

 

+!include DecomprScratchEnd.fdf.inc

+

 ################################################################################

 

 [Rule.Common.SEC]

diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf
index 8b4dd60605..6ba1948faa 100644
--- a/OvmfPkg/OvmfPkgX64.fdf
+++ b/OvmfPkg/OvmfPkgX64.fdf
@@ -78,7 +78,7 @@ FV = SECFV
 ################################################################################

 

 [FD.MEMFD]

-BaseAddress   = 0x800000

+BaseAddress   = $(MEMFD_BASE_ADDRESS)

 Size          = 0xA00000

 ErasePolarity = 1

 BlockSize     = 0x10000

@@ -384,6 +384,8 @@ FILE FV_IMAGE = 9E21FD93-9C72-4c15-8C4B-E77F1DB2D792 {
    }

  }

 

+!include DecomprScratchEnd.fdf.inc

+

 ################################################################################

 

 [Rule.Common.SEC]

diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 0cf127af84..93e3594e29 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -362,6 +362,14 @@ DecompressMemFvs (
 

   OutputBuffer = (VOID*) ((UINT8*)(UINTN) PcdGet32 (PcdOvmfDxeMemFvBase) + SIZE_1MB);

   ScratchBuffer = ALIGN_POINTER ((UINT8*) OutputBuffer + OutputBufferSize, SIZE_1MB);

+

+  DEBUG ((EFI_D_VERBOSE, "%a: OutputBuffer@%p+0x%x ScratchBuffer@%p+0x%x "

+    "PcdOvmfDecompressionScratchEnd=0x%x\n", __FUNCTION__, OutputBuffer,

+    OutputBufferSize, ScratchBuffer, ScratchBufferSize,

+    PcdGet32 (PcdOvmfDecompressionScratchEnd)));

+  ASSERT ((UINTN)ScratchBuffer + ScratchBufferSize ==

+    PcdGet32 (PcdOvmfDecompressionScratchEnd));

+

   Status = ExtractGuidedSectionDecode (

              Section,

              &OutputBuffer,

diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index 415731ce54..9e8571dddd 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -70,3 +70,4 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize

   gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress

   gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize

+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd