Re: [PATCH v2 04/11] OvmfPkg: add library class BlobVerifierLib with null implementation


Dov Murik
 

On 19/07/2021 18:50, Tom Lendacky wrote:
On 7/6/21 3:54 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 NullBlobVerifierLib treats all blobs as valid.

Cc: Laszlo Ersek <lersek@redhat.com>
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/NullBlobVerifierLib.inf | 27 ++++++++++++++
OvmfPkg/Include/Library/BlobVerifierLib.h | 38 ++++++++++++++++++++
OvmfPkg/Library/BlobVerifierLib/NullBlobVerifier.c | 34 ++++++++++++++++++
4 files changed, 102 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/NullBlobVerifierLib.inf b/OvmfPkg/Library/BlobVerifierLib/NullBlobVerifierLib.inf
new file mode 100644
index 000000000000..c8942ad05d96
--- /dev/null
+++ b/OvmfPkg/Library/BlobVerifierLib/NullBlobVerifierLib.inf
@@ -0,0 +1,27 @@
+## @file
+#
+# Null implementation of the blob verifier library.
+#
+# Copyright (C) 2021, IBM Corp
+#
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+ INF_VERSION = 0x00010005
You can specify the INF_VERSION using x.y format now, and I believe the
latest is 1.29.
Thanks, I'll change that.


+ BASE_NAME = NullBlobVerifierLib
Typically, the NULL libraries would be named BlobVerifierLibNull.
You're right; I'll rename.



+ FILE_GUID = b1b5533e-e01a-43bb-9e54-414f00ca036e
+ MODULE_TYPE = BASE
+ VERSION_STRING = 1.0
+ LIBRARY_CLASS = BlobVerifierLib
+
+[Sources]
+ NullBlobVerifier.c
+
+[Packages]
+ MdePkg/MdePkg.dec
+ OvmfPkg/OvmfPkg.dec
+
+[LibraryClasses]
+ DebugLib
Is this library (and associated include below) needed?
Probably not; I'll remove.


diff --git a/OvmfPkg/Include/Library/BlobVerifierLib.h b/OvmfPkg/Include/Library/BlobVerifierLib.h
new file mode 100644
index 000000000000..667024766681
--- /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 BlobName The name of the blob
I believe this is supposed to be @param[in]
OK.

+ @param Buf The data of the blob
+ @param 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,
+ UINT32 BufSize
Missing "IN" here (same below for these).
You're right. I'll add it.

Thanks,
-Dov


Thanks,
Tom

+ );
+
+#endif
diff --git a/OvmfPkg/Library/BlobVerifierLib/NullBlobVerifier.c b/OvmfPkg/Library/BlobVerifierLib/NullBlobVerifier.c
new file mode 100644
index 000000000000..7b31b6ec767d
--- /dev/null
+++ b/OvmfPkg/Library/BlobVerifierLib/NullBlobVerifier.c
@@ -0,0 +1,34 @@
+/** @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/DebugLib.h>
+#include <Library/BlobVerifierLib.h>
+
+/**
+ Verify blob from an external source.
+
+ @param BlobName The name of the blob
+ @param Buf The data of the blob
+ @param 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,
+ UINT32 BufSize
+ )
+{
+ return EFI_SUCCESS;
+}

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