[PATCH v3 00/11] Measured SEV boot with kernel/initrd/cmdline

[PATCH v3 00/11] Measured SEV boot with kernel/initrd/cmdline

[Dov Murik]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3457

Booting with SEV prevented the loading of kernel, initrd, and kernel
command-line via QEMU fw_cfg interface because they arrive from the VMM
which is untrusted in SEV.

However, in some cases the kernel, initrd, and cmdline are not secret
but should not be modified by the host.  In such a case, we want to
verify inside the trusted VM that the kernel, initrd, and cmdline are
indeed the ones expected by the Guest Owner, and only if that is the
case go on and boot them up (removing the need for grub inside OVMF in
that mode).

This patch series reserves an area in MEMFD (previously the last 1KB of
the launch secret page) which will contain the hashes of these three
blobs (kernel, initrd, cmdline), each under its own GUID entry.  This
tables of hashes is populated by QEMU before launch, and encrypted as
part of the initial VM memory; this makes sure these hashes are part of
the SEV measurement (which has to be approved by the Guest Owner for
secret injection, for example).  Note that populating the hashes table
requires QEMU support [1].

OVMF parses the table of hashes populated by QEMU (patch 10), and as it
reads the fw_cfg blobs from QEMU, it will verify each one against the
expected hash.  This is all done inside the trusted VM context.  If all
the hashes are correct, boot of the kernel is allowed to continue.

Any attempt by QEMU to modify the kernel, initrd, cmdline (including
dropping one of them), or to modify the OVMF code that verifies those
hashes, will cause the initial SEV measurement to change and therefore
will be detectable by the Guest Owner during launch before secret
injection.

Relevant part of OVMF serial log during boot with AmdSevX86 build and
QEMU with -kernel/-initrd/-append:

  ...
  BlobVerifierLibSevHashesConstructor: Found injected hashes table in secure location
  Select Item: 0x17
  Select Item: 0x8
  FetchBlob: loading 7379328 bytes for "kernel"
  Select Item: 0x18
  Select Item: 0x11
  VerifyBlob: Found GUID 4DE79437-ABD2-427F-B835-D5B172D2045B in table
  VerifyBlob: Hash comparison succeeded for "kernel"
  Select Item: 0xB
  FetchBlob: loading 12483878 bytes for "initrd"
  Select Item: 0x12
  VerifyBlob: Found GUID 44BAF731-3A2F-4BD7-9AF1-41E29169781D in table
  VerifyBlob: Hash comparison succeeded for "initrd"
  Select Item: 0x14
  FetchBlob: loading 86 bytes for "cmdline"
  Select Item: 0x15
  VerifyBlob: Found GUID 97D02DD8-BD20-4C94-AA78-E7714D36AB2A in table
  VerifyBlob: Hash comparison succeeded for "cmdline"
  ...

The patch series is organized as follows:

1:     Simple comment fix in adjacent area in the code.
2:     Use GenericQemuLoadImageLib to gain one location for fw_cfg blob
       fetching.
3:     Allow the (previously blocked) usage of -kernel in AmdSevX64.
4-7:   Add BlobVerifierLib with null implementation and use it in the correct
       location in QemuKernelLoaderFsDxe.
8-9:   Reserve memory for hashes table, declare this area in the reset vector.
10-11: Add the secure implementation BlobVerifierLibSevHashes and use it in
       AmdSevX64 builds.

[1] https://lore.kernel.org/qemu-devel/20210624102040.2015280-1-dovmurik@linux.ibm.com/

Code is at
https://github.com/confidential-containers-demo/edk2/tree/sev-hashes-v3

v3 changes:
 - Rename to BlobVerifierLibNull, use decimal INF_VERSION, remove unused
   DebugLib reference, fix doxygen comments, add missing IN attribute
 - Rename to BlobVerifierLibSevHashes, use decimal INF_VERSION, fix
   doxygen comments, add missing IN attribute,
   calculate buffer hash only when the guid is found in hashes table
 - SecretPei: use ALIGN_VALUE to round the hob size
 - Coding style fixes
 - Add missing 'Ref:' in patch 1 commit message
 - Fix phrasing and typos in commit messages
 - Remove Cc: Laszlo from series

v2: https://edk2.groups.io/g/devel/message/77505
v2 changes:
 - Use the last 1KB of the existing SEV launch secret page for hashes table
   (instead of reserving a whole new MEMFD page).
 - Build on top of commit cf203024745f ("OvmfPkg/GenericQemuLoadImageLib: Read
   cmdline from QemuKernelLoaderFs", 2021-06-28) to have a single location in
   which all of kernel/initrd/cmdline are fetched from QEMU.
 - Use static linking of the two BlobVerifierLib implemenatations.
 - Reorganize series.

v1: https://edk2.groups.io/g/devel/message/75567

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>

Dov Murik (8):
  OvmfPkg/AmdSev: use GenericQemuLoadImageLib in AmdSev builds
  OvmfPkg: add library class BlobVerifierLib with null implementation
  OvmfPkg: add BlobVerifierLibNull to DSC
  ArmVirtPkg: add BlobVerifierLibNull to DSC
  OvmfPkg/QemuKernelLoaderFsDxe: call VerifyBlob after fetch from fw_cfg
  OvmfPkg/AmdSev/SecretPei: build hob for full page
  OvmfPkg: add BlobVerifierLibSevHashes
  OvmfPkg/AmdSev: Enforce hash verification of kernel blobs

James Bottomley (3):
  OvmfPkg/AmdSev/SecretDxe: fix header comment to generic naming
  OvmfPkg: PlatformBootManagerLibGrub: Allow executing kernel via fw_cfg
  OvmfPkg/AmdSev: reserve MEMFD space for for firmware config hashes

 OvmfPkg/OvmfPkg.dec                                                                 |   9 +
 ArmVirtPkg/ArmVirtQemu.dsc                                                          |   5 +-
 ArmVirtPkg/ArmVirtQemuKernel.dsc                                                    |   5 +-
 OvmfPkg/AmdSev/AmdSevX64.dsc                                                        |   9 +-
 OvmfPkg/OvmfPkgIa32.dsc                                                             |   5 +-
 OvmfPkg/OvmfPkgIa32X64.dsc                                                          |   5 +-
 OvmfPkg/OvmfPkgX64.dsc                                                              |   5 +-
 OvmfPkg/AmdSev/AmdSevX64.fdf                                                        |   5 +-
 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf                             |  24 +++
 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf                        |  37 ++++
 OvmfPkg/Library/PlatformBootManagerLibGrub/PlatformBootManagerLibGrub.inf           |   2 +
 OvmfPkg/ResetVector/ResetVector.inf                                                 |   2 +
 OvmfPkg/Include/Library/BlobVerifierLib.h                                           |  38 ++++
 OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.h                            |  11 ++
 OvmfPkg/AmdSev/SecretDxe/SecretDxe.c                                                |   2 +-
 OvmfPkg/AmdSev/SecretPei/SecretPei.c                                                |   3 +-
 OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c                                  |  33 ++++
 OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c                             | 200 ++++++++++++++++++++
 OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.c                            |   5 +
 OvmfPkg/Library/{PlatformBootManagerLib => PlatformBootManagerLibGrub}/QemuKernel.c |   0
 OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c                               |   9 +
 OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm                                        |  20 ++
 OvmfPkg/ResetVector/ResetVector.nasmb                                               |   2 +
 23 files changed, 426 insertions(+), 10 deletions(-)
 create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
 create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf
 create mode 100644 OvmfPkg/Include/Library/BlobVerifierLib.h
 create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c
 create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c
 copy OvmfPkg/Library/{PlatformBootManagerLib => PlatformBootManagerLibGrub}/QemuKernel.c (100%)

-- 
2.25.1

[PATCH v3 01/11] OvmfPkg/AmdSev/SecretDxe: fix header comment to generic naming

[Dov Murik]

From: James Bottomley <jejb@linux.ibm.com>

Commit 96201ae7bf97 ("OvmfPkg/AmdSev/SecretDxe: make secret location
naming generic", 2020-12-15) replaced references to SEV with the generic
term Confidential Computing, but missed the file header comment.  Fix
the naming in that header.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Signed-off-by: James Bottomley <jejb@linux.ibm.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/AmdSev/SecretDxe/SecretDxe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/OvmfPkg/AmdSev/SecretDxe/SecretDxe.c b/OvmfPkg/AmdSev/SecretDxe/SecretDxe.c
index 308022b5b25e..934ad207632b 100644
--- a/OvmfPkg/AmdSev/SecretDxe/SecretDxe.c
+++ b/OvmfPkg/AmdSev/SecretDxe/SecretDxe.c
@@ -1,5 +1,5 @@
 /** @file
-  SEV Secret configuration table constructor
+  Confidential Computing Secret configuration table constructor
 
   Copyright (C) 2020 James Bottomley, IBM Corporation.
   SPDX-License-Identifier: BSD-2-Clause-Patent
-- 
2.25.1

[PATCH v3 02/11] OvmfPkg/AmdSev: use GenericQemuLoadImageLib in AmdSev builds

[Dov Murik]

Newer kernels support efistub and therefore don't need all the legacy
stuff in X86QemuLoadImageLib, which are harder to secure.  Specifically
the verification of kernel/initrd/cmdline blobs will be added only to
the GenericQemuLoadImageLib implementation, so use that for SEV builds.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/AmdSev/AmdSevX64.dsc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/OvmfPkg/AmdSev/AmdSevX64.dsc b/OvmfPkg/AmdSev/AmdSevX64.dsc
index 1d487befae08..a2f1324c40a6 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.dsc
+++ b/OvmfPkg/AmdSev/AmdSevX64.dsc
@@ -368,7 +368,7 @@ [LibraryClasses.common.DXE_DRIVER]
   PciLib|OvmfPkg/Library/DxePciLibI440FxQ35/DxePciLibI440FxQ35.inf
   MpInitLib|UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
   QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/DxeQemuFwCfgS3LibFwCfg.inf
-  QemuLoadImageLib|OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.inf
+  QemuLoadImageLib|OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
 !if $(TPM_ENABLE) == TRUE
   Tpm12DeviceLib|SecurityPkg/Library/Tpm12DeviceLibTcg/Tpm12DeviceLibTcg.inf
   Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibTcg2/Tpm2DeviceLibTcg2.inf
-- 
2.25.1

[PATCH v3 03/11] OvmfPkg: PlatformBootManagerLibGrub: Allow executing kernel via fw_cfg

[Dov Murik]

From: James Bottomley <jejb@linux.ibm.com>

Support QEMU's -kernel option.

Create a QemuKernel.c for PlatformBootManagerLibGrub
which is an exact copy of the file
PlatformBootManagerLib/QemuKernel.c .

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Signed-off-by: James Bottomley <jejb@linux.ibm.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/AmdSev/AmdSevX64.dsc                                                        |  1 +
 OvmfPkg/Library/PlatformBootManagerLibGrub/PlatformBootManagerLibGrub.inf           |  2 ++
 OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.h                            | 11 +++++++++++
 OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.c                            |  5 +++++
 OvmfPkg/Library/{PlatformBootManagerLib => PlatformBootManagerLibGrub}/QemuKernel.c |  0
 5 files changed, 19 insertions(+)

diff --git a/OvmfPkg/AmdSev/AmdSevX64.dsc b/OvmfPkg/AmdSev/AmdSevX64.dsc
index a2f1324c40a6..aefdcf881c99 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.dsc
+++ b/OvmfPkg/AmdSev/AmdSevX64.dsc
@@ -281,6 +281,7 @@ [LibraryClasses.common.PEIM]
   CpuExceptionHandlerLib|UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
   MpInitLib|UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf
   QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/PeiQemuFwCfgS3LibFwCfg.inf
+  QemuLoadImageLib|OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
   PcdLib|MdePkg/Library/PeiPcdLib/PeiPcdLib.inf
   QemuFwCfgLib|OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
 
diff --git a/OvmfPkg/Library/PlatformBootManagerLibGrub/PlatformBootManagerLibGrub.inf b/OvmfPkg/Library/PlatformBootManagerLibGrub/PlatformBootManagerLibGrub.inf
index 9a806d17ec45..5f6f73d18470 100644
--- a/OvmfPkg/Library/PlatformBootManagerLibGrub/PlatformBootManagerLibGrub.inf
+++ b/OvmfPkg/Library/PlatformBootManagerLibGrub/PlatformBootManagerLibGrub.inf
@@ -23,6 +23,7 @@ [Defines]
 
 [Sources]
   BdsPlatform.c
+  QemuKernel.c
   PlatformData.c
   BdsPlatform.h
 
@@ -46,6 +47,7 @@ [LibraryClasses]
   BootLogoLib
   DevicePathLib
   PciLib
+  QemuLoadImageLib
   UefiLib
   PlatformBmPrintScLib
   Tcg2PhysicalPresenceLib
diff --git a/OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.h b/OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.h
index 748c63081920..f1d3a2906c00 100644
--- a/OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.h
+++ b/OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.h
@@ -172,4 +172,15 @@ PlatformInitializeConsole (
   IN PLATFORM_CONSOLE_CONNECT_ENTRY   *PlatformConsole
   );
 
+/**
+  Loads and boots UEFI Linux via the FwCfg interface.
+
+  @retval    EFI_NOT_FOUND - The Linux kernel was not found
+
+**/
+EFI_STATUS
+TryRunningQemuKernel (
+  VOID
+  );
+
 #endif // _PLATFORM_SPECIFIC_BDS_PLATFORM_H_
diff --git a/OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.c b/OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.c
index 5c92d4fc2b09..7cceeea4879c 100644
--- a/OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.c
+++ b/OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.c
@@ -1315,6 +1315,11 @@ PlatformBootManagerAfterConsole (
   //
   Tcg2PhysicalPresenceLibProcessRequest (NULL);
 
+  //
+  // Process QEMU's -kernel command line option
+  //
+  TryRunningQemuKernel ();
+
   //
   // Perform some platform specific connect sequence
   //
diff --git a/OvmfPkg/Library/PlatformBootManagerLib/QemuKernel.c b/OvmfPkg/Library/PlatformBootManagerLibGrub/QemuKernel.c
similarity index 100%
copy from OvmfPkg/Library/PlatformBootManagerLib/QemuKernel.c
copy to OvmfPkg/Library/PlatformBootManagerLibGrub/QemuKernel.c
-- 
2.25.1

[PATCH v3 04/11] OvmfPkg: add library class BlobVerifierLib with null implementation

[Dov Murik]

BlobVerifierLib will be used to verify blobs fetching them from QEMU's
firmware config (fw_cfg) in platforms that enable such verification.

The null implementation BlobVerifierLibNull treats all blobs as valid.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 OvmfPkg/OvmfPkg.dec                                     |  3 ++
 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf | 24 +++++++++++++
 OvmfPkg/Include/Library/BlobVerifierLib.h               | 38 ++++++++++++++++++++
 OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c      | 33 +++++++++++++++++
 4 files changed, 98 insertions(+)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 6ae733f6e39f..f82228d69cc2 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -23,6 +23,9 @@ [LibraryClasses]
   ##  @libraryclass  Access bhyve's firmware control interface.
   BhyveFwCtlLib|Include/Library/BhyveFwCtlLib.h
 
+  ##  @libraryclass  Verify blobs read from the VMM
+  BlobVerifierLib|Include/Library/BlobVerifierLib.h
+
   ##  @libraryclass  Loads and boots a Linux kernel image
   #
   LoadLinuxLib|Include/Library/LoadLinuxLib.h
diff --git a/OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
new file mode 100644
index 000000000000..850d398e65a4
--- /dev/null
+++ b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
@@ -0,0 +1,24 @@
+## @file
+#
+#  Null implementation of the blob verifier library.
+#
+#  Copyright (C) 2021, IBM Corp
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 1.29
+  BASE_NAME                      = BlobVerifierLibNull
+  FILE_GUID                      = b1b5533e-e01a-43bb-9e54-414f00ca036e
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = BlobVerifierLib
+
+[Sources]
+  BlobVerifierNull.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
diff --git a/OvmfPkg/Include/Library/BlobVerifierLib.h b/OvmfPkg/Include/Library/BlobVerifierLib.h
new file mode 100644
index 000000000000..db122684f76c
--- /dev/null
+++ b/OvmfPkg/Include/Library/BlobVerifierLib.h
@@ -0,0 +1,38 @@
+/** @file
+
+  Blob verification library
+
+  This library class allows verifiying whether blobs from external sources
+  (such as QEMU's firmware config) are trusted.
+
+  Copyright (C) 2021, IBM Corporation
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#ifndef BLOB_VERIFIER_LIB_H__
+#define BLOB_VERIFIER_LIB_H__
+
+#include <Uefi/UefiBaseType.h>
+#include <Base.h>
+
+/**
+  Verify blob from an external source.
+
+  @param[in] BlobName           The name of the blob
+  @param[in] Buf                The data of the blob
+  @param[in] BufSize            The size of the blob in bytes
+
+  @retval EFI_SUCCESS           The blob was verified successfully.
+  @retval EFI_ACCESS_DENIED     The blob could not be verified, and therefore
+                                should be considered non-secure.
+**/
+EFI_STATUS
+EFIAPI
+VerifyBlob (
+  IN  CONST CHAR16    *BlobName,
+  IN  CONST VOID      *Buf,
+  IN  UINT32          BufSize
+  );
+
+#endif
diff --git a/OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c
new file mode 100644
index 000000000000..975d4dd52f80
--- /dev/null
+++ b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c
@@ -0,0 +1,33 @@
+/** @file
+
+  Null implementation of the blob verifier library.
+
+  Copyright (C) 2021, IBM Corporation
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include <Library/BaseLib.h>
+#include <Library/BlobVerifierLib.h>
+
+/**
+  Verify blob from an external source.
+
+  @param[in] BlobName           The name of the blob
+  @param[in] Buf                The data of the blob
+  @param[in] BufSize            The size of the blob in bytes
+
+  @retval EFI_SUCCESS           The blob was verified successfully.
+  @retval EFI_ACCESS_DENIED     The blob could not be verified, and therefore
+                                should be considered non-secure.
+**/
+EFI_STATUS
+EFIAPI
+VerifyBlob (
+  IN  CONST CHAR16    *BlobName,
+  IN  CONST VOID      *Buf,
+  IN  UINT32          BufSize
+  )
+{
+  return EFI_SUCCESS;
+}
-- 
2.25.1

[PATCH v3 05/11] OvmfPkg: add BlobVerifierLibNull to DSC

[Dov Murik]

This prepares the ground for calling VerifyBlob() in
QemuKernelLoaderFsDxe.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 OvmfPkg/AmdSev/AmdSevX64.dsc | 6 +++++-
 OvmfPkg/OvmfPkgIa32.dsc      | 5 ++++-
 OvmfPkg/OvmfPkgIa32X64.dsc   | 5 ++++-
 OvmfPkg/OvmfPkgX64.dsc       | 5 ++++-
 4 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/OvmfPkg/AmdSev/AmdSevX64.dsc b/OvmfPkg/AmdSev/AmdSevX64.dsc
index aefdcf881c99..b2cc96cc5a97 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.dsc
+++ b/OvmfPkg/AmdSev/AmdSevX64.dsc
@@ -173,6 +173,7 @@ [LibraryClasses]
   LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
   CustomizedDisplayLib|MdeModulePkg/Library/CustomizedDisplayLib/CustomizedDisplayLib.inf
   FrameBufferBltLib|MdeModulePkg/Library/FrameBufferBltLib/FrameBufferBltLib.inf
+  BlobVerifierLib|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
 
 !if $(SOURCE_DEBUG_ENABLE) == TRUE
   PeCoffExtraActionLib|SourceLevelDebugPkg/Library/PeCoffExtraActionLibDebug/PeCoffExtraActionLibDebug.inf
@@ -693,7 +694,10 @@ [Components]
       NULL|MdeModulePkg/Library/BootManagerUiLib/BootManagerUiLib.inf
       NULL|MdeModulePkg/Library/BootMaintenanceManagerUiLib/BootMaintenanceManagerUiLib.inf
   }
-  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf
+  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf {
+    <LibraryClasses>
+      NULL|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
+  }
   OvmfPkg/VirtioPciDeviceDxe/VirtioPciDeviceDxe.inf
   OvmfPkg/Virtio10Dxe/Virtio10.inf
   OvmfPkg/VirtioBlkDxe/VirtioBlk.inf
diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index f53efeae7986..7613abab6a7f 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -786,7 +786,10 @@ [Components]
       NULL|OvmfPkg/Csm/LegacyBootMaintUiLib/LegacyBootMaintUiLib.inf
 !endif
   }
-  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf
+  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf {
+    <LibraryClasses>
+      NULL|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
+  }
   OvmfPkg/VirtioPciDeviceDxe/VirtioPciDeviceDxe.inf
   OvmfPkg/Virtio10Dxe/Virtio10.inf
   OvmfPkg/VirtioBlkDxe/VirtioBlk.inf
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index b3662e17f256..8b35aaf4b44c 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -800,7 +800,10 @@ [Components.X64]
       NULL|OvmfPkg/Csm/LegacyBootMaintUiLib/LegacyBootMaintUiLib.inf
 !endif
   }
-  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf
+  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf {
+    <LibraryClasses>
+      NULL|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
+  }
   OvmfPkg/VirtioPciDeviceDxe/VirtioPciDeviceDxe.inf
   OvmfPkg/Virtio10Dxe/Virtio10.inf
   OvmfPkg/VirtioBlkDxe/VirtioBlk.inf
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 0a237a905866..0c95c74ad1a8 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -798,7 +798,10 @@ [Components]
       NULL|OvmfPkg/Csm/LegacyBootMaintUiLib/LegacyBootMaintUiLib.inf
 !endif
   }
-  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf
+  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf {
+    <LibraryClasses>
+      NULL|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
+  }
   OvmfPkg/VirtioPciDeviceDxe/VirtioPciDeviceDxe.inf
   OvmfPkg/Virtio10Dxe/Virtio10.inf
   OvmfPkg/VirtioBlkDxe/VirtioBlk.inf
-- 
2.25.1

[PATCH v3 06/11] ArmVirtPkg: add BlobVerifierLibNull to DSC

[Dov Murik]

This prepares the ground for calling VerifyBlob() in
QemuKernelLoaderFsDxe.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 ArmVirtPkg/ArmVirtQemu.dsc       | 5 ++++-
 ArmVirtPkg/ArmVirtQemuKernel.dsc | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/ArmVirtPkg/ArmVirtQemu.dsc b/ArmVirtPkg/ArmVirtQemu.dsc
index 7ef5e7297bc7..bf8bb1ec9578 100644
--- a/ArmVirtPkg/ArmVirtQemu.dsc
+++ b/ArmVirtPkg/ArmVirtQemu.dsc
@@ -440,7 +440,10 @@ [Components.common]
       NULL|MdeModulePkg/Library/BootManagerUiLib/BootManagerUiLib.inf
       NULL|MdeModulePkg/Library/BootMaintenanceManagerUiLib/BootMaintenanceManagerUiLib.inf
   }
-  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf
+  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf {
+    <LibraryClasses>
+      NULL|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
+  }
 
   #
   # Networking stack
diff --git a/ArmVirtPkg/ArmVirtQemuKernel.dsc b/ArmVirtPkg/ArmVirtQemuKernel.dsc
index a542fcb157e9..af34cb47a12d 100644
--- a/ArmVirtPkg/ArmVirtQemuKernel.dsc
+++ b/ArmVirtPkg/ArmVirtQemuKernel.dsc
@@ -376,7 +376,10 @@ [Components.common]
       NULL|MdeModulePkg/Library/BootManagerUiLib/BootManagerUiLib.inf
       NULL|MdeModulePkg/Library/BootMaintenanceManagerUiLib/BootMaintenanceManagerUiLib.inf
   }
-  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf
+  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf {
+    <LibraryClasses>
+      NULL|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
+  }
 
   #
   # Networking stack
-- 
2.25.1

[PATCH v3 07/11] OvmfPkg/QemuKernelLoaderFsDxe: call VerifyBlob after fetch from fw_cfg

[Dov Murik]

In QemuKernelLoaderFsDxeEntrypoint we use FetchBlob to read the content
of the kernel/initrd/cmdline from the QEMU fw_cfg interface.  Insert a
call to VerifyBlob after fetching to allow BlobVerifierLib
implementations to add a verification step for these blobs.

This will allow confidential computing OVMF builds to add verification
mechanisms for these blobs that originate from an untrusted source
(QEMU).

The null implementation of BlobVerifierLib does nothing in VerifyBlob,
and therefore no functional change is expected.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Co-developed-by: James Bottomley <jejb@linux.ibm.com>
Signed-off-by: James Bottomley <jejb@linux.ibm.com>
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c
index c7ddd86f5c75..6832d563bcb0 100644
--- a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c
+++ b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c
@@ -17,6 +17,7 @@
 #include <Guid/QemuKernelLoaderFsMedia.h>
 #include <Library/BaseLib.h>
 #include <Library/BaseMemoryLib.h>
+#include <Library/BlobVerifierLib.h>
 #include <Library/DebugLib.h>
 #include <Library/DevicePathLib.h>
 #include <Library/MemoryAllocationLib.h>
@@ -1039,6 +1040,14 @@ QemuKernelLoaderFsDxeEntrypoint (
     if (EFI_ERROR (Status)) {
       goto FreeBlobs;
     }
+    Status = VerifyBlob (
+               CurrentBlob->Name,
+               CurrentBlob->Data,
+               CurrentBlob->Size
+               );
+    if (EFI_ERROR (Status)) {
+      goto FreeBlobs;
+    }
     mTotalBlobBytes += CurrentBlob->Size;
   }
   KernelBlob      = &mKernelBlob[KernelBlobTypeKernel];
-- 
2.25.1

[PATCH v3 08/11] OvmfPkg/AmdSev/SecretPei: build hob for full page

[Dov Murik]

Round up the size of the SEV launch secret area to a whole page, as
required by BuildMemoryAllocationHob.  This will allow the secret
area defined in the MEMFD to take less than a whole 4KB page.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 OvmfPkg/AmdSev/SecretPei/SecretPei.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/AmdSev/SecretPei/SecretPei.c b/OvmfPkg/AmdSev/SecretPei/SecretPei.c
index ad491515dd5d..db94c26b54d1 100644
--- a/OvmfPkg/AmdSev/SecretPei/SecretPei.c
+++ b/OvmfPkg/AmdSev/SecretPei/SecretPei.c
@@ -4,6 +4,7 @@
   Copyright (C) 2020 James Bottomley, IBM Corporation.
   SPDX-License-Identifier: BSD-2-Clause-Patent
 **/
+#include <Base.h>
 #include <PiPei.h>
 #include <Library/HobLib.h>
 #include <Library/PcdLib.h>
@@ -17,7 +18,7 @@ InitializeSecretPei (
 {
   BuildMemoryAllocationHob (
     PcdGet32 (PcdSevLaunchSecretBase),
-    PcdGet32 (PcdSevLaunchSecretSize),
+    ALIGN_VALUE (PcdGet32 (PcdSevLaunchSecretSize), EFI_PAGE_SIZE),
     EfiBootServicesData
     );
 
-- 
2.25.1

[PATCH v3 09/11] OvmfPkg/AmdSev: reserve MEMFD space for for firmware config hashes

[Dov Murik]

From: James Bottomley <jejb@linux.ibm.com>

Split the existing 4KB page reserved for SEV launch secrets into two
parts: first 3KB for SEV launch secrets and last 1KB for firmware
config hashes.

The area of the firmware config hashes will be attested (measured) by
the PSP and thus the untrusted VMM can't pass in different files from
what the guest owner allows.

Declare this in the Reset Vector table using GUID
7255371f-3a3b-4b04-927b-1da6efa8d454 and a uint32_t table of a base
and size value (similar to the structure used to declare the launch
secret block).

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Co-developed-by: Dov Murik <dovmurik@linux.ibm.com>
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Signed-off-by: James Bottomley <jejb@linux.ibm.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/OvmfPkg.dec                          |  6 ++++++
 OvmfPkg/AmdSev/AmdSevX64.fdf                 |  5 ++++-
 OvmfPkg/ResetVector/ResetVector.inf          |  2 ++
 OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm | 20 ++++++++++++++++++++
 OvmfPkg/ResetVector/ResetVector.nasmb        |  2 ++
 5 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index f82228d69cc2..2ab27f0c73c2 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -324,6 +324,12 @@ [PcdsFixedAtBuild]
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase|0x0|UINT32|0x42
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize|0x0|UINT32|0x43
 
+  ## The base address and size of a hash table confirming allowed
+  #  parameters to be passed in via the Qemu firmware configuration
+  #  device
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase|0x0|UINT32|0x47
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize|0x0|UINT32|0x48
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
diff --git a/OvmfPkg/AmdSev/AmdSevX64.fdf b/OvmfPkg/AmdSev/AmdSevX64.fdf
index 9977b0f00a18..0a89749700c3 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.fdf
+++ b/OvmfPkg/AmdSev/AmdSevX64.fdf
@@ -59,9 +59,12 @@ [FD.MEMFD]
 0x00B000|0x001000
 gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase|gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaSize
 
-0x00C000|0x001000
+0x00C000|0x000C00
 gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase|gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
 
+0x00CC00|0x000400
+gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
+
 0x00D000|0x001000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
 
diff --git a/OvmfPkg/ResetVector/ResetVector.inf b/OvmfPkg/ResetVector/ResetVector.inf
index dc38f68919cd..d028c92d8cfa 100644
--- a/OvmfPkg/ResetVector/ResetVector.inf
+++ b/OvmfPkg/ResetVector/ResetVector.inf
@@ -47,3 +47,5 @@ [Pcd]
 [FixedPcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
diff --git a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
index 9c0b5853a46f..7ec3c6e980c3 100644
--- a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
+++ b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm
@@ -47,7 +47,27 @@ TIMES (15 - ((guidedStructureEnd - guidedStructureStart + 15) % 16)) DB 0
 ;
 guidedStructureStart:
 
+; SEV Hash Table Block
 ;
+; This describes the guest ram area where the hypervisor should
+; install a table describing the hashes of certain firmware configuration
+; device files that would otherwise be passed in unchecked.  The current
+; use is for the kernel, initrd and command line values, but others may be
+; added.  The data format is:
+;
+; base physical address (32 bit word)
+; table length (32 bit word)
+;
+; GUID (SEV FW config hash block): 7255371f-3a3b-4b04-927b-1da6efa8d454
+;
+sevFwHashBlockStart:
+    DD      SEV_FW_HASH_BLOCK_BASE
+    DD      SEV_FW_HASH_BLOCK_SIZE
+    DW      sevFwHashBlockEnd - sevFwHashBlockStart
+    DB      0x1f, 0x37, 0x55, 0x72, 0x3b, 0x3a, 0x04, 0x4b
+    DB      0x92, 0x7b, 0x1d, 0xa6, 0xef, 0xa8, 0xd4, 0x54
+sevFwHashBlockEnd:
+
 ; SEV Secret block
 ;
 ; This describes the guest ram area where the hypervisor should
diff --git a/OvmfPkg/ResetVector/ResetVector.nasmb b/OvmfPkg/ResetVector/ResetVector.nasmb
index 5fbacaed5f9d..8d0bab02f8cb 100644
--- a/OvmfPkg/ResetVector/ResetVector.nasmb
+++ b/OvmfPkg/ResetVector/ResetVector.nasmb
@@ -88,5 +88,7 @@
   %define SEV_ES_AP_RESET_IP  FixedPcdGet32 (PcdSevEsWorkAreaBase)
   %define SEV_LAUNCH_SECRET_BASE  FixedPcdGet32 (PcdSevLaunchSecretBase)
   %define SEV_LAUNCH_SECRET_SIZE  FixedPcdGet32 (PcdSevLaunchSecretSize)
+  %define SEV_FW_HASH_BLOCK_BASE  FixedPcdGet32 (PcdQemuHashTableBase)
+  %define SEV_FW_HASH_BLOCK_SIZE  FixedPcdGet32 (PcdQemuHashTableSize)
 %include "Ia16/ResetVectorVtf0.asm"
 
-- 
2.25.1

[PATCH v3 10/11] OvmfPkg: add BlobVerifierLibSevHashes

[Dov Murik]

Add an implementation for BlobVerifierLib that locates the SEV hashes
table and verifies that the calculated hashes of the kernel, initrd, and
cmdline blobs indeed match the expected hashes stated in the hashes
table.

If there's a missing hash or a hash mismatch then EFI_ACCESS_DENIED is
returned which will cause a failure to load a kernel image.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Co-developed-by: James Bottomley <jejb@linux.ibm.com>
Signed-off-by: James Bottomley <jejb@linux.ibm.com>
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf |  37 ++++
 OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c      | 200 ++++++++++++++++++++
 2 files changed, 237 insertions(+)

diff --git a/OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf
new file mode 100644
index 000000000000..76ca0b8154ce
--- /dev/null
+++ b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf
@@ -0,0 +1,37 @@
+## @file
+#
+#  Blob verifier library that uses SEV hashes table.  The hashes table holds the
+#  allowed hashes of the kernel, initrd, and cmdline blobs.
+#
+#  Copyright (C) 2021, IBM Corp
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 1.29
+  BASE_NAME                      = BlobVerifierLibSevHashes
+  FILE_GUID                      = 59e713b5-eff3-46a7-8d8b-46f4c004ad7b
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = BlobVerifierLib
+  CONSTRUCTOR                    = BlobVerifierLibSevHashesConstructor
+
+[Sources]
+  BlobVerifierSevHashes.c
+
+[Packages]
+  CryptoPkg/CryptoPkg.dec
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
+
+[LibraryClasses]
+  BaseCryptLib
+  BaseMemoryLib
+  DebugLib
+  PcdLib
+
+[FixedPcd]
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
diff --git a/OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c
new file mode 100644
index 000000000000..797d63d18067
--- /dev/null
+++ b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c
@@ -0,0 +1,200 @@
+/** @file
+
+  Blob verifier library that uses SEV hashes table.  The hashes table holds the
+  allowed hashes of the kernel, initrd, and cmdline blobs.
+
+  Copyright (C) 2021, IBM Corporation
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include <Library/BaseCryptLib.h>
+#include <Library/BaseLib.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/DebugLib.h>
+#include <Library/BlobVerifierLib.h>
+
+/**
+  The SEV Hashes table must be in encrypted memory and has the table
+  and its entries described by
+
+  <GUID>|UINT16 <len>|<data>
+
+  With the whole table GUID being 9438d606-4f22-4cc9-b479-a793d411fd21
+
+  The current possible table entries are for the kernel, the initrd
+  and the cmdline:
+
+  4de79437-abd2-427f-b835-d5b172d2045b  kernel
+  44baf731-3a2f-4bd7-9af1-41e29169781d  initrd
+  97d02dd8-bd20-4c94-aa78-e7714d36ab2a  cmdline
+
+  The size of the entry is used to identify the hash, but the
+  expectation is that it will be 32 bytes of SHA-256.
+**/
+
+#define SEV_HASH_TABLE_GUID \
+  (GUID) { 0x9438d606, 0x4f22, 0x4cc9, { 0xb4, 0x79, 0xa7, 0x93, 0xd4, 0x11, 0xfd, 0x21 } }
+#define SEV_KERNEL_HASH_GUID \
+  (GUID) { 0x4de79437, 0xabd2, 0x427f, { 0xb8, 0x35, 0xd5, 0xb1, 0x72, 0xd2, 0x04, 0x5b } }
+#define SEV_INITRD_HASH_GUID \
+  (GUID) { 0x44baf731, 0x3a2f, 0x4bd7, { 0x9a, 0xf1, 0x41, 0xe2, 0x91, 0x69, 0x78, 0x1d } }
+#define SEV_CMDLINE_HASH_GUID \
+  (GUID) { 0x97d02dd8, 0xbd20, 0x4c94, { 0xaa, 0x78, 0xe7, 0x71, 0x4d, 0x36, 0xab, 0x2a } }
+
+STATIC CONST EFI_GUID mSevKernelHashGuid = SEV_KERNEL_HASH_GUID;
+STATIC CONST EFI_GUID mSevInitrdHashGuid = SEV_INITRD_HASH_GUID;
+STATIC CONST EFI_GUID mSevCmdlineHashGuid = SEV_CMDLINE_HASH_GUID;
+
+#pragma pack (1)
+typedef struct {
+  GUID   Guid;
+  UINT16 Len;
+  UINT8  Data[];
+} HASH_TABLE;
+#pragma pack ()
+
+STATIC HASH_TABLE *mHashesTable;
+STATIC UINT16 mHashesTableSize;
+
+STATIC
+CONST GUID*
+FindBlobEntryGuid (
+  IN  CONST CHAR16    *BlobName
+  )
+{
+  if (StrCmp (BlobName, L"kernel") == 0) {
+    return &mSevKernelHashGuid;
+  } else if (StrCmp (BlobName, L"initrd") == 0) {
+    return &mSevInitrdHashGuid;
+  } else if (StrCmp (BlobName, L"cmdline") == 0) {
+    return &mSevCmdlineHashGuid;
+  } else {
+    return NULL;
+  }
+}
+
+/**
+  Verify blob from an external source.
+
+  @param[in] BlobName           The name of the blob
+  @param[in] Buf                The data of the blob
+  @param[in] BufSize            The size of the blob in bytes
+
+  @retval EFI_SUCCESS           The blob was verified successfully.
+  @retval EFI_ACCESS_DENIED     The blob could not be verified, and therefore
+                                should be considered non-secure.
+**/
+EFI_STATUS
+EFIAPI
+VerifyBlob (
+  IN  CONST CHAR16    *BlobName,
+  IN  CONST VOID      *Buf,
+  IN  UINT32          BufSize
+  )
+{
+  CONST GUID *Guid;
+  INT32 Len;
+  HASH_TABLE *Entry;
+
+  if (mHashesTable == NULL || mHashesTableSize == 0) {
+    DEBUG ((DEBUG_ERROR,
+      "%a: Verifier called but no hashes table discoverd in MEMFD\n",
+      __FUNCTION__));
+    return EFI_ACCESS_DENIED;
+  }
+
+  Guid = FindBlobEntryGuid (BlobName);
+  if (Guid == NULL) {
+    DEBUG ((DEBUG_ERROR, "%a: Unknown blob name \"%s\"\n", __FUNCTION__,
+      BlobName));
+    return EFI_ACCESS_DENIED;
+  }
+
+  for (Entry = mHashesTable, Len = 0;
+       Len < (INT32)mHashesTableSize;
+       Len += Entry->Len,
+       Entry = (HASH_TABLE *)((UINT8 *)Entry + Entry->Len)) {
+    UINTN EntrySize;
+    EFI_STATUS Status;
+    UINT8 Hash[SHA256_DIGEST_SIZE];
+
+    if (!CompareGuid (&Entry->Guid, Guid)) {
+      continue;
+    }
+
+    DEBUG ((DEBUG_INFO, "%a: Found GUID %g in table\n", __FUNCTION__, Guid));
+
+    EntrySize = Entry->Len - sizeof (Entry->Guid) - sizeof (Entry->Len);
+    if (EntrySize != SHA256_DIGEST_SIZE) {
+      DEBUG ((DEBUG_ERROR, "%a: Hash has the wrong size %d != %d\n",
+        __FUNCTION__, EntrySize, SHA256_DIGEST_SIZE));
+      return EFI_ACCESS_DENIED;
+    }
+
+    //
+    // Calculate the buffer's hash and verify that it is identical to the
+    // expected hash table entry
+    //
+    Sha256HashAll (Buf, BufSize, Hash);
+
+    if (CompareMem (Entry->Data, Hash, EntrySize) == 0) {
+      Status = EFI_SUCCESS;
+      DEBUG ((DEBUG_INFO, "%a: Hash comparison succeeded for \"%s\"\n",
+        __FUNCTION__, BlobName));
+    } else {
+      Status = EFI_ACCESS_DENIED;
+      DEBUG ((DEBUG_ERROR, "%a: Hash comparison failed for \"%s\"\n",
+        __FUNCTION__, BlobName));
+    }
+    return Status;
+  }
+
+  DEBUG ((DEBUG_ERROR, "%a: Hash GUID %g not found in table\n", __FUNCTION__,
+    Guid));
+  return EFI_ACCESS_DENIED;
+}
+
+/**
+  Locate the SEV hashes table.
+
+  This function always returns success, even if the table can't be found.  The
+  subsequent VerifyBlob calls will fail if no table was found.
+
+  @retval RETURN_SUCCESS   The verifier tables were set up correctly
+**/
+RETURN_STATUS
+EFIAPI
+BlobVerifierLibSevHashesConstructor (
+  VOID
+  )
+{
+  HASH_TABLE *Ptr = (void *)(UINTN)FixedPcdGet64 (PcdQemuHashTableBase);
+  UINT32 Size = FixedPcdGet32 (PcdQemuHashTableSize);
+
+  mHashesTable = NULL;
+  mHashesTableSize = 0;
+
+  if (Ptr == NULL || Size == 0) {
+    return RETURN_SUCCESS;
+  }
+
+  if (!CompareGuid (&Ptr->Guid, &SEV_HASH_TABLE_GUID)) {
+    return RETURN_SUCCESS;
+  }
+
+  if (Ptr->Len < (sizeof Ptr->Guid + sizeof Ptr->Len)) {
+    return RETURN_SUCCESS;
+  }
+
+  DEBUG ((DEBUG_INFO, "%a: Found injected hashes table in secure location\n",
+    __FUNCTION__));
+
+  mHashesTable = (HASH_TABLE *)Ptr->Data;
+  mHashesTableSize = Ptr->Len - sizeof Ptr->Guid - sizeof Ptr->Len;
+
+  DEBUG ((DEBUG_VERBOSE, "%a: mHashesTable=0x%p, Size=%u\n", __FUNCTION__,
+    mHashesTable, mHashesTableSize));
+
+  return RETURN_SUCCESS;
+}
-- 
2.25.1

[PATCH v3 11/11] OvmfPkg/AmdSev: Enforce hash verification of kernel blobs

[Dov Murik]

In the AmdSevX64 build, use BlobVerifierLibSevHashes to enforce
verification of hashes of the kernel/initrd/cmdline blobs fetched from
firmware config.

This allows for secure (measured) boot of SEV guests with QEMU's
-kernel/-initrd/-append switches (with the corresponding QEMU support
for injecting the hashes table into initial measured guest memory).

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
---
 OvmfPkg/AmdSev/AmdSevX64.dsc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/OvmfPkg/AmdSev/AmdSevX64.dsc b/OvmfPkg/AmdSev/AmdSevX64.dsc
index b2cc96cc5a97..c01599ea354f 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.dsc
+++ b/OvmfPkg/AmdSev/AmdSevX64.dsc
@@ -173,7 +173,7 @@ [LibraryClasses]
   LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
   CustomizedDisplayLib|MdeModulePkg/Library/CustomizedDisplayLib/CustomizedDisplayLib.inf
   FrameBufferBltLib|MdeModulePkg/Library/FrameBufferBltLib/FrameBufferBltLib.inf
-  BlobVerifierLib|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
+  BlobVerifierLib|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf
 
 !if $(SOURCE_DEBUG_ENABLE) == TRUE
   PeCoffExtraActionLib|SourceLevelDebugPkg/Library/PeCoffExtraActionLibDebug/PeCoffExtraActionLibDebug.inf
@@ -696,7 +696,7 @@ [Components]
   }
   OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf {
     <LibraryClasses>
-      NULL|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
+      NULL|OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf
   }
   OvmfPkg/VirtioPciDeviceDxe/VirtioPciDeviceDxe.inf
   OvmfPkg/Virtio10Dxe/Virtio10.inf
-- 
2.25.1

Re: [PATCH v3 04/11] OvmfPkg: add library class BlobVerifierLib with null implementation

[Lendacky, Thomas]

On 7/20/21 3:03 AM, Dov Murik wrote:
> BlobVerifierLib will be used to verify blobs fetching them from QEMU's
> firmware config (fw_cfg) in platforms that enable such verification.
> 
> The null implementation BlobVerifierLibNull treats all blobs as valid.
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>  OvmfPkg/OvmfPkg.dec                                     |  3 ++
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf | 24 +++++++++++++
>  OvmfPkg/Include/Library/BlobVerifierLib.h               | 38 ++++++++++++++++++++
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c      | 33 +++++++++++++++++
>  4 files changed, 98 insertions(+)
> 

Re: [PATCH v3 05/11] OvmfPkg: add BlobVerifierLibNull to DSC

[Lendacky, Thomas]

On 7/20/21 3:03 AM, Dov Murik wrote:
> This prepares the ground for calling VerifyBlob() in
> QemuKernelLoaderFsDxe.
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>  OvmfPkg/AmdSev/AmdSevX64.dsc | 6 +++++-
>  OvmfPkg/OvmfPkgIa32.dsc      | 5 ++++-
>  OvmfPkg/OvmfPkgIa32X64.dsc   | 5 ++++-
>  OvmfPkg/OvmfPkgX64.dsc       | 5 ++++-
>  4 files changed, 17 insertions(+), 4 deletions(-)

Re: [PATCH v3 07/11] OvmfPkg/QemuKernelLoaderFsDxe: call VerifyBlob after fetch from fw_cfg

[Lendacky, Thomas]

On 7/20/21 3:03 AM, Dov Murik wrote:
> In QemuKernelLoaderFsDxeEntrypoint we use FetchBlob to read the content
> of the kernel/initrd/cmdline from the QEMU fw_cfg interface.  Insert a
> call to VerifyBlob after fetching to allow BlobVerifierLib
> implementations to add a verification step for these blobs.
> 
> This will allow confidential computing OVMF builds to add verification
> mechanisms for these blobs that originate from an untrusted source
> (QEMU).
> 
> The null implementation of BlobVerifierLib does nothing in VerifyBlob,
> and therefore no functional change is expected.
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Co-developed-by: James Bottomley <jejb@linux.ibm.com>
> Signed-off-by: James Bottomley <jejb@linux.ibm.com>
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

Re: [PATCH v3 08/11] OvmfPkg/AmdSev/SecretPei: build hob for full page

[Lendacky, Thomas]

On 7/20/21 3:03 AM, Dov Murik wrote:
> Round up the size of the SEV launch secret area to a whole page, as
> required by BuildMemoryAllocationHob.  This will allow the secret
> area defined in the MEMFD to take less than a whole 4KB page.
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>  OvmfPkg/AmdSev/SecretPei/SecretPei.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 

Re: [PATCH v3 08/11] OvmfPkg/AmdSev/SecretPei: build hob for full page

[Brijesh Singh]

On 7/20/21 3:03 AM, Dov Murik wrote:
> Round up the size of the SEV launch secret area to a whole page, as
> required by BuildMemoryAllocationHob.  This will allow the secret
> area defined in the MEMFD to take less than a whole 4KB page.
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>

Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>

thanks

Re: [PATCH v3 09/11] OvmfPkg/AmdSev: reserve MEMFD space for for firmware config hashes

[Brijesh Singh]

On 7/20/21 3:03 AM, Dov Murik wrote:
> From: James Bottomley <jejb@linux.ibm.com>
> 
> Split the existing 4KB page reserved for SEV launch secrets into two
> parts: first 3KB for SEV launch secrets and last 1KB for firmware
> config hashes.
> 
> The area of the firmware config hashes will be attested (measured) by
> the PSP and thus the untrusted VMM can't pass in different files from
> what the guest owner allows.
> 
> Declare this in the Reset Vector table using GUID
> 7255371f-3a3b-4b04-927b-1da6efa8d454 and a uint32_t table of a base
> and size value (similar to the structure used to declare the launch
> secret block).
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Co-developed-by: Dov Murik <dovmurik@linux.ibm.com>
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
> Signed-off-by: James Bottomley <jejb@linux.ibm.com>
> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>

thanks

Re: [PATCH v3 10/11] OvmfPkg: add BlobVerifierLibSevHashes

[Lendacky, Thomas]

On 7/20/21 3:04 AM, Dov Murik wrote:
> Add an implementation for BlobVerifierLib that locates the SEV hashes
> table and verifies that the calculated hashes of the kernel, initrd, and
> cmdline blobs indeed match the expected hashes stated in the hashes
> table.
> 
> If there's a missing hash or a hash mismatch then EFI_ACCESS_DENIED is
> returned which will cause a failure to load a kernel image.
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Co-developed-by: James Bottomley <jejb@linux.ibm.com>
> Signed-off-by: James Bottomley <jejb@linux.ibm.com>
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>

A comment about the use of INT32 in the for loop to protect against a
large entry length value would be useful. I don't think it's worth another
version, but if you have to make any updates it would be nice to add.

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf |  37 ++++
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c      | 200 ++++++++++++++++++++
>  2 files changed, 237 insertions(+)
> 

Re: [PATCH v3 11/11] OvmfPkg/AmdSev: Enforce hash verification of kernel blobs

[Lendacky, Thomas]

On 7/20/21 3:04 AM, Dov Murik wrote:
> In the AmdSevX64 build, use BlobVerifierLibSevHashes to enforce
> verification of hashes of the kernel/initrd/cmdline blobs fetched from
> firmware config.
> 
> This allows for secure (measured) boot of SEV guests with QEMU's
> -kernel/-initrd/-append switches (with the corresponding QEMU support
> for injecting the hashes table into initial measured guest memory).
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>  OvmfPkg/AmdSev/AmdSevX64.dsc | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 

Re: [PATCH v3 00/11] Measured SEV boot with kernel/initrd/cmdline

[Lendacky, Thomas]

On 7/20/21 3:03 AM, Dov Murik wrote:
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3457

I believe the convention is that this line be in the individual patch
commit messages just like this (i.e. with the BZ: tag and the first line),
not as a Ref: tag at the end of the commit message.

I'll let Ard decide on that, though.

Thanks,
Tom

> 
> Booting with SEV prevented the loading of kernel, initrd, and kernel
> command-line via QEMU fw_cfg interface because they arrive from the VMM
> which is untrusted in SEV.
> 
> However, in some cases the kernel, initrd, and cmdline are not secret
> but should not be modified by the host.  In such a case, we want to
> verify inside the trusted VM that the kernel, initrd, and cmdline are
> indeed the ones expected by the Guest Owner, and only if that is the
> case go on and boot them up (removing the need for grub inside OVMF in
> that mode).
> 
> This patch series reserves an area in MEMFD (previously the last 1KB of
> the launch secret page) which will contain the hashes of these three
> blobs (kernel, initrd, cmdline), each under its own GUID entry.  This
> tables of hashes is populated by QEMU before launch, and encrypted as
> part of the initial VM memory; this makes sure these hashes are part of
> the SEV measurement (which has to be approved by the Guest Owner for
> secret injection, for example).  Note that populating the hashes table
> requires QEMU support [1].
> 
> OVMF parses the table of hashes populated by QEMU (patch 10), and as it
> reads the fw_cfg blobs from QEMU, it will verify each one against the
> expected hash.  This is all done inside the trusted VM context.  If all
> the hashes are correct, boot of the kernel is allowed to continue.
> 
> Any attempt by QEMU to modify the kernel, initrd, cmdline (including
> dropping one of them), or to modify the OVMF code that verifies those
> hashes, will cause the initial SEV measurement to change and therefore
> will be detectable by the Guest Owner during launch before secret
> injection.
> 
> Relevant part of OVMF serial log during boot with AmdSevX86 build and
> QEMU with -kernel/-initrd/-append:
> 
>   ...
>   BlobVerifierLibSevHashesConstructor: Found injected hashes table in secure location
>   Select Item: 0x17
>   Select Item: 0x8
>   FetchBlob: loading 7379328 bytes for "kernel"
>   Select Item: 0x18
>   Select Item: 0x11
>   VerifyBlob: Found GUID 4DE79437-ABD2-427F-B835-D5B172D2045B in table
>   VerifyBlob: Hash comparison succeeded for "kernel"
>   Select Item: 0xB
>   FetchBlob: loading 12483878 bytes for "initrd"
>   Select Item: 0x12
>   VerifyBlob: Found GUID 44BAF731-3A2F-4BD7-9AF1-41E29169781D in table
>   VerifyBlob: Hash comparison succeeded for "initrd"
>   Select Item: 0x14
>   FetchBlob: loading 86 bytes for "cmdline"
>   Select Item: 0x15
>   VerifyBlob: Found GUID 97D02DD8-BD20-4C94-AA78-E7714D36AB2A in table
>   VerifyBlob: Hash comparison succeeded for "cmdline"
>   ...
> 
> The patch series is organized as follows:
> 
> 1:     Simple comment fix in adjacent area in the code.
> 2:     Use GenericQemuLoadImageLib to gain one location for fw_cfg blob
>        fetching.
> 3:     Allow the (previously blocked) usage of -kernel in AmdSevX64.
> 4-7:   Add BlobVerifierLib with null implementation and use it in the correct
>        location in QemuKernelLoaderFsDxe.
> 8-9:   Reserve memory for hashes table, declare this area in the reset vector.
> 10-11: Add the secure implementation BlobVerifierLibSevHashes and use it in
>        AmdSevX64 builds.
> 
> [1] https://lore.kernel.org/qemu-devel/20210624102040.2015280-1-dovmurik@linux.ibm.com/
> 
> Code is at
> https://github.com/confidential-containers-demo/edk2/tree/sev-hashes-v3
> 
> v3 changes:
>  - Rename to BlobVerifierLibNull, use decimal INF_VERSION, remove unused
>    DebugLib reference, fix doxygen comments, add missing IN attribute
>  - Rename to BlobVerifierLibSevHashes, use decimal INF_VERSION, fix
>    doxygen comments, add missing IN attribute,
>    calculate buffer hash only when the guid is found in hashes table
>  - SecretPei: use ALIGN_VALUE to round the hob size
>  - Coding style fixes
>  - Add missing 'Ref:' in patch 1 commit message
>  - Fix phrasing and typos in commit messages
>  - Remove Cc: Laszlo from series
> 
> v2: https://edk2.groups.io/g/devel/message/77505
> v2 changes:
>  - Use the last 1KB of the existing SEV launch secret page for hashes table
>    (instead of reserving a whole new MEMFD page).
>  - Build on top of commit cf203024745f ("OvmfPkg/GenericQemuLoadImageLib: Read
>    cmdline from QemuKernelLoaderFs", 2021-06-28) to have a single location in
>    which all of kernel/initrd/cmdline are fetched from QEMU.
>  - Use static linking of the two BlobVerifierLib implemenatations.
>  - Reorganize series.
> 
> v1: https://edk2.groups.io/g/devel/message/75567
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Leif Lindholm <leif@nuviainc.com>
> Cc: Sami Mujawar <sami.mujawar@arm.com>
> 
> Dov Murik (8):
>   OvmfPkg/AmdSev: use GenericQemuLoadImageLib in AmdSev builds
>   OvmfPkg: add library class BlobVerifierLib with null implementation
>   OvmfPkg: add BlobVerifierLibNull to DSC
>   ArmVirtPkg: add BlobVerifierLibNull to DSC
>   OvmfPkg/QemuKernelLoaderFsDxe: call VerifyBlob after fetch from fw_cfg
>   OvmfPkg/AmdSev/SecretPei: build hob for full page
>   OvmfPkg: add BlobVerifierLibSevHashes
>   OvmfPkg/AmdSev: Enforce hash verification of kernel blobs
> 
> James Bottomley (3):
>   OvmfPkg/AmdSev/SecretDxe: fix header comment to generic naming
>   OvmfPkg: PlatformBootManagerLibGrub: Allow executing kernel via fw_cfg
>   OvmfPkg/AmdSev: reserve MEMFD space for for firmware config hashes
> 
>  OvmfPkg/OvmfPkg.dec                                                                 |   9 +
>  ArmVirtPkg/ArmVirtQemu.dsc                                                          |   5 +-
>  ArmVirtPkg/ArmVirtQemuKernel.dsc                                                    |   5 +-
>  OvmfPkg/AmdSev/AmdSevX64.dsc                                                        |   9 +-
>  OvmfPkg/OvmfPkgIa32.dsc                                                             |   5 +-
>  OvmfPkg/OvmfPkgIa32X64.dsc                                                          |   5 +-
>  OvmfPkg/OvmfPkgX64.dsc                                                              |   5 +-
>  OvmfPkg/AmdSev/AmdSevX64.fdf                                                        |   5 +-
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf                             |  24 +++
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf                        |  37 ++++
>  OvmfPkg/Library/PlatformBootManagerLibGrub/PlatformBootManagerLibGrub.inf           |   2 +
>  OvmfPkg/ResetVector/ResetVector.inf                                                 |   2 +
>  OvmfPkg/Include/Library/BlobVerifierLib.h                                           |  38 ++++
>  OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.h                            |  11 ++
>  OvmfPkg/AmdSev/SecretDxe/SecretDxe.c                                                |   2 +-
>  OvmfPkg/AmdSev/SecretPei/SecretPei.c                                                |   3 +-
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c                                  |  33 ++++
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c                             | 200 ++++++++++++++++++++
>  OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.c                            |   5 +
>  OvmfPkg/Library/{PlatformBootManagerLib => PlatformBootManagerLibGrub}/QemuKernel.c |   0
>  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c                               |   9 +
>  OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm                                        |  20 ++
>  OvmfPkg/ResetVector/ResetVector.nasmb                                               |   2 +
>  23 files changed, 426 insertions(+), 10 deletions(-)
>  create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
>  create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf
>  create mode 100644 OvmfPkg/Include/Library/BlobVerifierLib.h
>  create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c
>  create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c
>  copy OvmfPkg/Library/{PlatformBootManagerLib => PlatformBootManagerLibGrub}/QemuKernel.c (100%)
> 

Re: [PATCH v3 00/11] Measured SEV boot with kernel/initrd/cmdline

[Ard Biesheuvel]

On Tue, 20 Jul 2021 at 19:22, Tom Lendacky <thomas.lendacky@amd.com> wrote:
>
> On 7/20/21 3:03 AM, Dov Murik wrote:
> > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
>
> I believe the convention is that this line be in the individual patch
> commit messages just like this (i.e. with the BZ: tag and the first line),
> not as a Ref: tag at the end of the commit message.
>
> I'll let Ard decide on that, though.
>

Using Ref: in the signoff section of the patch is perfectly fine with me.

I'll go over this series on Thursday and merge it if everything looks ok.

Thanks all for the review.

> >
> > Booting with SEV prevented the loading of kernel, initrd, and kernel
> > command-line via QEMU fw_cfg interface because they arrive from the VMM
> > which is untrusted in SEV.
> >
> > However, in some cases the kernel, initrd, and cmdline are not secret
> > but should not be modified by the host.  In such a case, we want to
> > verify inside the trusted VM that the kernel, initrd, and cmdline are
> > indeed the ones expected by the Guest Owner, and only if that is the
> > case go on and boot them up (removing the need for grub inside OVMF in
> > that mode).
> >
> > This patch series reserves an area in MEMFD (previously the last 1KB of
> > the launch secret page) which will contain the hashes of these three
> > blobs (kernel, initrd, cmdline), each under its own GUID entry.  This
> > tables of hashes is populated by QEMU before launch, and encrypted as
> > part of the initial VM memory; this makes sure these hashes are part of
> > the SEV measurement (which has to be approved by the Guest Owner for
> > secret injection, for example).  Note that populating the hashes table
> > requires QEMU support [1].
> >
> > OVMF parses the table of hashes populated by QEMU (patch 10), and as it
> > reads the fw_cfg blobs from QEMU, it will verify each one against the
> > expected hash.  This is all done inside the trusted VM context.  If all
> > the hashes are correct, boot of the kernel is allowed to continue.
> >
> > Any attempt by QEMU to modify the kernel, initrd, cmdline (including
> > dropping one of them), or to modify the OVMF code that verifies those
> > hashes, will cause the initial SEV measurement to change and therefore
> > will be detectable by the Guest Owner during launch before secret
> > injection.
> >
> > Relevant part of OVMF serial log during boot with AmdSevX86 build and
> > QEMU with -kernel/-initrd/-append:
> >
> >   ...
> >   BlobVerifierLibSevHashesConstructor: Found injected hashes table in secure location
> >   Select Item: 0x17
> >   Select Item: 0x8
> >   FetchBlob: loading 7379328 bytes for "kernel"
> >   Select Item: 0x18
> >   Select Item: 0x11
> >   VerifyBlob: Found GUID 4DE79437-ABD2-427F-B835-D5B172D2045B in table
> >   VerifyBlob: Hash comparison succeeded for "kernel"
> >   Select Item: 0xB
> >   FetchBlob: loading 12483878 bytes for "initrd"
> >   Select Item: 0x12
> >   VerifyBlob: Found GUID 44BAF731-3A2F-4BD7-9AF1-41E29169781D in table
> >   VerifyBlob: Hash comparison succeeded for "initrd"
> >   Select Item: 0x14
> >   FetchBlob: loading 86 bytes for "cmdline"
> >   Select Item: 0x15
> >   VerifyBlob: Found GUID 97D02DD8-BD20-4C94-AA78-E7714D36AB2A in table
> >   VerifyBlob: Hash comparison succeeded for "cmdline"
> >   ...
> >
> > The patch series is organized as follows:
> >
> > 1:     Simple comment fix in adjacent area in the code.
> > 2:     Use GenericQemuLoadImageLib to gain one location for fw_cfg blob
> >        fetching.
> > 3:     Allow the (previously blocked) usage of -kernel in AmdSevX64.
> > 4-7:   Add BlobVerifierLib with null implementation and use it in the correct
> >        location in QemuKernelLoaderFsDxe.
> > 8-9:   Reserve memory for hashes table, declare this area in the reset vector.
> > 10-11: Add the secure implementation BlobVerifierLibSevHashes and use it in
> >        AmdSevX64 builds.
> >
> > [1] https://lore.kernel.org/qemu-devel/20210624102040.2015280-1-dovmurik@linux.ibm.com/
> >
> > Code is at
> > https://github.com/confidential-containers-demo/edk2/tree/sev-hashes-v3
> >
> > v3 changes:
> >  - Rename to BlobVerifierLibNull, use decimal INF_VERSION, remove unused
> >    DebugLib reference, fix doxygen comments, add missing IN attribute
> >  - Rename to BlobVerifierLibSevHashes, use decimal INF_VERSION, fix
> >    doxygen comments, add missing IN attribute,
> >    calculate buffer hash only when the guid is found in hashes table
> >  - SecretPei: use ALIGN_VALUE to round the hob size
> >  - Coding style fixes
> >  - Add missing 'Ref:' in patch 1 commit message
> >  - Fix phrasing and typos in commit messages
> >  - Remove Cc: Laszlo from series
> >
> > v2: https://edk2.groups.io/g/devel/message/77505
> > v2 changes:
> >  - Use the last 1KB of the existing SEV launch secret page for hashes table
> >    (instead of reserving a whole new MEMFD page).
> >  - Build on top of commit cf203024745f ("OvmfPkg/GenericQemuLoadImageLib: Read
> >    cmdline from QemuKernelLoaderFs", 2021-06-28) to have a single location in
> >    which all of kernel/initrd/cmdline are fetched from QEMU.
> >  - Use static linking of the two BlobVerifierLib implemenatations.
> >  - Reorganize series.
> >
> > v1: https://edk2.groups.io/g/devel/message/75567
> >
> > Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> > Cc: Jordan Justen <jordan.l.justen@intel.com>
> > Cc: Ashish Kalra <ashish.kalra@amd.com>
> > Cc: Brijesh Singh <brijesh.singh@amd.com>
> > Cc: Erdem Aktas <erdemaktas@google.com>
> > Cc: James Bottomley <jejb@linux.ibm.com>
> > Cc: Jiewen Yao <jiewen.yao@intel.com>
> > Cc: Min Xu <min.m.xu@intel.com>
> > Cc: Tom Lendacky <thomas.lendacky@amd.com>
> > Cc: Leif Lindholm <leif@nuviainc.com>
> > Cc: Sami Mujawar <sami.mujawar@arm.com>
> >
> > Dov Murik (8):
> >   OvmfPkg/AmdSev: use GenericQemuLoadImageLib in AmdSev builds
> >   OvmfPkg: add library class BlobVerifierLib with null implementation
> >   OvmfPkg: add BlobVerifierLibNull to DSC
> >   ArmVirtPkg: add BlobVerifierLibNull to DSC
> >   OvmfPkg/QemuKernelLoaderFsDxe: call VerifyBlob after fetch from fw_cfg
> >   OvmfPkg/AmdSev/SecretPei: build hob for full page
> >   OvmfPkg: add BlobVerifierLibSevHashes
> >   OvmfPkg/AmdSev: Enforce hash verification of kernel blobs
> >
> > James Bottomley (3):
> >   OvmfPkg/AmdSev/SecretDxe: fix header comment to generic naming
> >   OvmfPkg: PlatformBootManagerLibGrub: Allow executing kernel via fw_cfg
> >   OvmfPkg/AmdSev: reserve MEMFD space for for firmware config hashes
> >
> >  OvmfPkg/OvmfPkg.dec                                                                 |   9 +
> >  ArmVirtPkg/ArmVirtQemu.dsc                                                          |   5 +-
> >  ArmVirtPkg/ArmVirtQemuKernel.dsc                                                    |   5 +-
> >  OvmfPkg/AmdSev/AmdSevX64.dsc                                                        |   9 +-
> >  OvmfPkg/OvmfPkgIa32.dsc                                                             |   5 +-
> >  OvmfPkg/OvmfPkgIa32X64.dsc                                                          |   5 +-
> >  OvmfPkg/OvmfPkgX64.dsc                                                              |   5 +-
> >  OvmfPkg/AmdSev/AmdSevX64.fdf                                                        |   5 +-
> >  OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf                             |  24 +++
> >  OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf                        |  37 ++++
> >  OvmfPkg/Library/PlatformBootManagerLibGrub/PlatformBootManagerLibGrub.inf           |   2 +
> >  OvmfPkg/ResetVector/ResetVector.inf                                                 |   2 +
> >  OvmfPkg/Include/Library/BlobVerifierLib.h                                           |  38 ++++
> >  OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.h                            |  11 ++
> >  OvmfPkg/AmdSev/SecretDxe/SecretDxe.c                                                |   2 +-
> >  OvmfPkg/AmdSev/SecretPei/SecretPei.c                                                |   3 +-
> >  OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c                                  |  33 ++++
> >  OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c                             | 200 ++++++++++++++++++++
> >  OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.c                            |   5 +
> >  OvmfPkg/Library/{PlatformBootManagerLib => PlatformBootManagerLibGrub}/QemuKernel.c |   0
> >  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c                               |   9 +
> >  OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm                                        |  20 ++
> >  OvmfPkg/ResetVector/ResetVector.nasmb                                               |   2 +
> >  23 files changed, 426 insertions(+), 10 deletions(-)
> >  create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf
> >  create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf
> >  create mode 100644 OvmfPkg/Include/Library/BlobVerifierLib.h
> >  create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c
> >  create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c
> >  copy OvmfPkg/Library/{PlatformBootManagerLib => PlatformBootManagerLibGrub}/QemuKernel.c (100%)
> >

Re: [PATCH v3 10/11] OvmfPkg: add BlobVerifierLibSevHashes

[Brijesh Singh]

On 7/20/21 3:04 AM, Dov Murik wrote:
> Add an implementation for BlobVerifierLib that locates the SEV hashes
> table and verifies that the calculated hashes of the kernel, initrd, and
> cmdline blobs indeed match the expected hashes stated in the hashes
> table.
> 
> If there's a missing hash or a hash mismatch then EFI_ACCESS_DENIED is
> returned which will cause a failure to load a kernel image.
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Co-developed-by: James Bottomley <jejb@linux.ibm.com>
> Signed-off-by: James Bottomley <jejb@linux.ibm.com>
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
> ---

Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>

thanks

Re: [PATCH v3 00/11] Measured SEV boot with kernel/initrd/cmdline

[Dov Murik]

On 20/07/2021 20:27, Ard Biesheuvel wrote:
> On Tue, 20 Jul 2021 at 19:22, Tom Lendacky <thomas.lendacky@amd.com> wrote:
>>
>> On 7/20/21 3:03 AM, Dov Murik wrote:
>>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
>>
>> I believe the convention is that this line be in the individual patch
>> commit messages just like this (i.e. with the BZ: tag and the first line),
>> not as a Ref: tag at the end of the commit message.
>>
>> I'll let Ard decide on that, though.
>>
> 
> Using Ref: in the signoff section of the patch is perfectly fine with me.
> 
> I'll go over this series on Thursday and merge it if everything looks ok.


Please hold off - I think I found a bug in patch 10 (parsing of the SEV
hashes GUIDed structure).

I'll update with my findings soon.


> 
> Thanks all for the review.

Thank you Tom and Brijesh for the review -- you helped improve our
contribution.


-Dov

Re: [PATCH v3 10/11] OvmfPkg: add BlobVerifierLibSevHashes

[Dov Murik]

Tom, Brijesh, Ard,

I think I found a bug in this patch.  I used libfuzzer to test the
VerifyBlob implementation here, and it immediately found a few "read
memory out of range" issues.  See details below in VerifyBlob.

If the Guest Owner properly validates the measurement (which includes
the expected well-formatted hashes table), then QEMU cannot modify it by
including problematic length fields, etc.  So I this bug is not a
security issue - it doesn't allow QEMU to circumvent the
kernel/initrd/cmdline measurement check.

That said, I think that OVMF should not access memory ranges it's not
supposed to, and that's why I think hardening this parsing function is a
good idea.

I'll submit another version with added validity checks of the hashes
table structure. I'll also add the INT32 explanation comment per Tom's
suggestion.



On Tue, Jul 20, 2021 at 08:04:00AM +0000, Dov Murik wrote:
> Add an implementation for BlobVerifierLib that locates the SEV hashes
> table and verifies that the calculated hashes of the kernel, initrd, and
> cmdline blobs indeed match the expected hashes stated in the hashes
> table.
> 
> If there's a missing hash or a hash mismatch then EFI_ACCESS_DENIED is
> returned which will cause a failure to load a kernel image.
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ashish Kalra <ashish.kalra@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> Co-developed-by: James Bottomley <jejb@linux.ibm.com>
> Signed-off-by: James Bottomley <jejb@linux.ibm.com>
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
> ---
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf |  37 ++++
>  OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c      | 200 ++++++++++++++++++++
>  2 files changed, 237 insertions(+)
> 
> diff --git a/OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf
> new file mode 100644
> index 000000000000..76ca0b8154ce
> --- /dev/null
> +++ b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf
> @@ -0,0 +1,37 @@
> +## @file
> +#
> +#  Blob verifier library that uses SEV hashes table.  The hashes table holds the
> +#  allowed hashes of the kernel, initrd, and cmdline blobs.
> +#
> +#  Copyright (C) 2021, IBM Corp
> +#
> +#  SPDX-License-Identifier: BSD-2-Clause-Patent
> +#
> +##
> +
> +[Defines]
> +  INF_VERSION                    = 1.29
> +  BASE_NAME                      = BlobVerifierLibSevHashes
> +  FILE_GUID                      = 59e713b5-eff3-46a7-8d8b-46f4c004ad7b
> +  MODULE_TYPE                    = BASE
> +  VERSION_STRING                 = 1.0
> +  LIBRARY_CLASS                  = BlobVerifierLib
> +  CONSTRUCTOR                    = BlobVerifierLibSevHashesConstructor
> +
> +[Sources]
> +  BlobVerifierSevHashes.c
> +
> +[Packages]
> +  CryptoPkg/CryptoPkg.dec
> +  MdePkg/MdePkg.dec
> +  OvmfPkg/OvmfPkg.dec
> +
> +[LibraryClasses]
> +  BaseCryptLib
> +  BaseMemoryLib
> +  DebugLib
> +  PcdLib
> +
> +[FixedPcd]
> +  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase
> +  gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
> diff --git a/OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c
> new file mode 100644
> index 000000000000..797d63d18067
> --- /dev/null
> +++ b/OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c
> @@ -0,0 +1,200 @@
> +/** @file
> +
> +  Blob verifier library that uses SEV hashes table.  The hashes table holds the
> +  allowed hashes of the kernel, initrd, and cmdline blobs.
> +
> +  Copyright (C) 2021, IBM Corporation
> +
> +  SPDX-License-Identifier: BSD-2-Clause-Patent
> +**/
> +
> +#include <Library/BaseCryptLib.h>
> +#include <Library/BaseLib.h>
> +#include <Library/BaseMemoryLib.h>
> +#include <Library/DebugLib.h>
> +#include <Library/BlobVerifierLib.h>
> +
> +/**
> +  The SEV Hashes table must be in encrypted memory and has the table
> +  and its entries described by
> +
> +  <GUID>|UINT16 <len>|<data>
> +
> +  With the whole table GUID being 9438d606-4f22-4cc9-b479-a793d411fd21
> +
> +  The current possible table entries are for the kernel, the initrd
> +  and the cmdline:
> +
> +  4de79437-abd2-427f-b835-d5b172d2045b  kernel
> +  44baf731-3a2f-4bd7-9af1-41e29169781d  initrd
> +  97d02dd8-bd20-4c94-aa78-e7714d36ab2a  cmdline
> +
> +  The size of the entry is used to identify the hash, but the
> +  expectation is that it will be 32 bytes of SHA-256.
> +**/
> +
> +#define SEV_HASH_TABLE_GUID \
> +  (GUID) { 0x9438d606, 0x4f22, 0x4cc9, { 0xb4, 0x79, 0xa7, 0x93, 0xd4, 0x11, 0xfd, 0x21 } }
> +#define SEV_KERNEL_HASH_GUID \
> +  (GUID) { 0x4de79437, 0xabd2, 0x427f, { 0xb8, 0x35, 0xd5, 0xb1, 0x72, 0xd2, 0x04, 0x5b } }
> +#define SEV_INITRD_HASH_GUID \
> +  (GUID) { 0x44baf731, 0x3a2f, 0x4bd7, { 0x9a, 0xf1, 0x41, 0xe2, 0x91, 0x69, 0x78, 0x1d } }
> +#define SEV_CMDLINE_HASH_GUID \
> +  (GUID) { 0x97d02dd8, 0xbd20, 0x4c94, { 0xaa, 0x78, 0xe7, 0x71, 0x4d, 0x36, 0xab, 0x2a } }
> +
> +STATIC CONST EFI_GUID mSevKernelHashGuid = SEV_KERNEL_HASH_GUID;
> +STATIC CONST EFI_GUID mSevInitrdHashGuid = SEV_INITRD_HASH_GUID;
> +STATIC CONST EFI_GUID mSevCmdlineHashGuid = SEV_CMDLINE_HASH_GUID;
> +
> +#pragma pack (1)
> +typedef struct {
> +  GUID   Guid;
> +  UINT16 Len;
> +  UINT8  Data[];
> +} HASH_TABLE;
> +#pragma pack ()
> +
> +STATIC HASH_TABLE *mHashesTable;
> +STATIC UINT16 mHashesTableSize;
> +
> +STATIC
> +CONST GUID*
> +FindBlobEntryGuid (
> +  IN  CONST CHAR16    *BlobName
> +  )
> +{
> +  if (StrCmp (BlobName, L"kernel") == 0) {
> +    return &mSevKernelHashGuid;
> +  } else if (StrCmp (BlobName, L"initrd") == 0) {
> +    return &mSevInitrdHashGuid;
> +  } else if (StrCmp (BlobName, L"cmdline") == 0) {
> +    return &mSevCmdlineHashGuid;
> +  } else {
> +    return NULL;
> +  }
> +}
> +
> +/**
> +  Verify blob from an external source.
> +
> +  @param[in] BlobName           The name of the blob
> +  @param[in] Buf                The data of the blob
> +  @param[in] BufSize            The size of the blob in bytes
> +
> +  @retval EFI_SUCCESS           The blob was verified successfully.
> +  @retval EFI_ACCESS_DENIED     The blob could not be verified, and therefore
> +                                should be considered non-secure.
> +**/
> +EFI_STATUS
> +EFIAPI
> +VerifyBlob (
> +  IN  CONST CHAR16    *BlobName,
> +  IN  CONST VOID      *Buf,
> +  IN  UINT32          BufSize
> +  )
> +{
> +  CONST GUID *Guid;
> +  INT32 Len;
> +  HASH_TABLE *Entry;
> +
> +  if (mHashesTable == NULL || mHashesTableSize == 0) {
> +    DEBUG ((DEBUG_ERROR,
> +      "%a: Verifier called but no hashes table discoverd in MEMFD\n",
> +      __FUNCTION__));
> +    return EFI_ACCESS_DENIED;
> +  }
> +
> +  Guid = FindBlobEntryGuid (BlobName);
> +  if (Guid == NULL) {
> +    DEBUG ((DEBUG_ERROR, "%a: Unknown blob name \"%s\"\n", __FUNCTION__,
> +      BlobName));
> +    return EFI_ACCESS_DENIED;
> +  }
> +
> +  for (Entry = mHashesTable, Len = 0;
> +       Len < (INT32)mHashesTableSize;
> +       Len += Entry->Len,
> +       Entry = (HASH_TABLE *)((UINT8 *)Entry + Entry->Len)) {
> +    UINTN EntrySize;
> +    EFI_STATUS Status;
> +    UINT8 Hash[SHA256_DIGEST_SIZE];
> +
> +    if (!CompareGuid (&Entry->Guid, Guid)) {

Bug: This can access memory above the mHashTableSize limit.  Consider
mHashTableSize == 1.  We enter the for loop but CompareGuid will "read"
16 bytes of Entry->Guid, which is past the limit.


> +      continue;
> +    }
> +
> +    DEBUG ((DEBUG_INFO, "%a: Found GUID %g in table\n", __FUNCTION__, Guid));
> +
> +    EntrySize = Entry->Len - sizeof (Entry->Guid) - sizeof (Entry->Len);

Bug: This can access memory above the mHashTableSize limit.  Consider
mHashTableSize == 16.  CompareGuid is OK but Entry->Len accesses the 2
bytes at offset 16, which is after the limit.


> +    if (EntrySize != SHA256_DIGEST_SIZE) {
> +      DEBUG ((DEBUG_ERROR, "%a: Hash has the wrong size %d != %d\n",
> +        __FUNCTION__, EntrySize, SHA256_DIGEST_SIZE));
> +      return EFI_ACCESS_DENIED;
> +    }
> +
> +    //
> +    // Calculate the buffer's hash and verify that it is identical to the
> +    // expected hash table entry
> +    //
> +    Sha256HashAll (Buf, BufSize, Hash);
> +
> +    if (CompareMem (Entry->Data, Hash, EntrySize) == 0) {

Bug: This can access memory above the mHashTableSize limit.  Consider
mHashTableSize == 21.  CompareGuid is OK and Entry->Len == 50 as
expected (18 bytes header and 32 bytes for SHA256).  But CompareMem will
try to read the 32 bytes when it's only allowed to read 3 bytes
(21 - 18).


-Dov


> +      Status = EFI_SUCCESS;
> +      DEBUG ((DEBUG_INFO, "%a: Hash comparison succeeded for \"%s\"\n",
> +        __FUNCTION__, BlobName));
> +    } else {
> +      Status = EFI_ACCESS_DENIED;
> +      DEBUG ((DEBUG_ERROR, "%a: Hash comparison failed for \"%s\"\n",
> +        __FUNCTION__, BlobName));
> +    }
> +    return Status;
> +  }
> +
> +  DEBUG ((DEBUG_ERROR, "%a: Hash GUID %g not found in table\n", __FUNCTION__,
> +    Guid));
> +  return EFI_ACCESS_DENIED;
> +}
> +
> +/**
> +  Locate the SEV hashes table.
> +
> +  This function always returns success, even if the table can't be found.  The
> +  subsequent VerifyBlob calls will fail if no table was found.
> +
> +  @retval RETURN_SUCCESS   The verifier tables were set up correctly
> +**/
> +RETURN_STATUS
> +EFIAPI
> +BlobVerifierLibSevHashesConstructor (
> +  VOID
> +  )
> +{
> +  HASH_TABLE *Ptr = (void *)(UINTN)FixedPcdGet64 (PcdQemuHashTableBase);
> +  UINT32 Size = FixedPcdGet32 (PcdQemuHashTableSize);
> +
> +  mHashesTable = NULL;
> +  mHashesTableSize = 0;
> +
> +  if (Ptr == NULL || Size == 0) {
> +    return RETURN_SUCCESS;
> +  }
> +
> +  if (!CompareGuid (&Ptr->Guid, &SEV_HASH_TABLE_GUID)) {
> +    return RETURN_SUCCESS;
> +  }
> +
> +  if (Ptr->Len < (sizeof Ptr->Guid + sizeof Ptr->Len)) {
> +    return RETURN_SUCCESS;
> +  }
> +
> +  DEBUG ((DEBUG_INFO, "%a: Found injected hashes table in secure location\n",
> +    __FUNCTION__));
> +
> +  mHashesTable = (HASH_TABLE *)Ptr->Data;
> +  mHashesTableSize = Ptr->Len - sizeof Ptr->Guid - sizeof Ptr->Len;
> +
> +  DEBUG ((DEBUG_VERBOSE, "%a: mHashesTable=0x%p, Size=%u\n", __FUNCTION__,
> +    mHashesTable, mHashesTableSize));
> +
> +  return RETURN_SUCCESS;
> +}
> -- 
> 2.25.1
>