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| author | Tobin Feldman-Fitzthum <tobin@linux.ibm.com> | 2024-04-29 20:07:19 +0000 |
|---|---|---|
| committer | mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> | 2024-06-25 15:27:42 +0000 |
| commit | 10b4bb8d6d0c515ed9663691aea3684be8f7b0fc (patch) | |
| tree | 257b4d0f0f94c467b75401852a700406aa814a62 | |
| parent | 56059941ec8c2f4d8fb126227b1154f8a869ac2b (diff) | |
| download | edk2-10b4bb8d6d0c515ed9663691aea3684be8f7b0fc.zip edk2-10b4bb8d6d0c515ed9663691aea3684be8f7b0fc.tar.gz edk2-10b4bb8d6d0c515ed9663691aea3684be8f7b0fc.tar.bz2 | |
AmdSev: Halt on failed blob allocation
A malicious host may be able to undermine the fw_cfg
interface such that loading a blob fails.
In this case rather than continuing to the next boot
option, the blob verifier should halt.
For non-confidential guests, the error should be non-fatal.
Signed-off-by: Tobin Feldman-Fitzthum <tobin@linux.ibm.com>
4 files changed, 35 insertions, 15 deletions
diff --git a/OvmfPkg/AmdSev/BlobVerifierLibSevHashes/BlobVerifierSevHashes.c b/OvmfPkg/AmdSev/BlobVerifierLibSevHashes/BlobVerifierSevHashes.c index 37c38e9..bc2d5da 100644 --- a/OvmfPkg/AmdSev/BlobVerifierLibSevHashes/BlobVerifierSevHashes.c +++ b/OvmfPkg/AmdSev/BlobVerifierLibSevHashes/BlobVerifierSevHashes.c @@ -83,6 +83,7 @@ FindBlobEntryGuid ( @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
+ @param[in] FetchStatus The status of the previous blob fetch
@retval EFI_SUCCESS The blob was verified successfully or was not
found in the hash table.
@@ -94,13 +95,27 @@ EFIAPI VerifyBlob (
IN CONST CHAR16 *BlobName,
IN CONST VOID *Buf,
- IN UINT32 BufSize
+ IN UINT32 BufSize,
+ IN EFI_STATUS FetchStatus
)
{
CONST GUID *Guid;
INT32 Remaining;
HASH_TABLE *Entry;
+ // Enter a dead loop if the fetching of this blob
+ // failed. This prevents a malicious host from
+ // circumventing the following checks.
+ if (EFI_ERROR (FetchStatus)) {
+ DEBUG ((
+ DEBUG_ERROR,
+ "%a: Fetching blob failed.\n",
+ __func__
+ ));
+
+ CpuDeadLoop ();
+ }
+
if ((mHashesTable == NULL) || (mHashesTableSize == 0)) {
DEBUG ((
DEBUG_WARN,
diff --git a/OvmfPkg/Include/Library/BlobVerifierLib.h b/OvmfPkg/Include/Library/BlobVerifierLib.h index 7e1af27..09af1b7 100644 --- a/OvmfPkg/Include/Library/BlobVerifierLib.h +++ b/OvmfPkg/Include/Library/BlobVerifierLib.h @@ -22,17 +22,20 @@ @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
+ @param[in] FetchStatus The status of fetching this blob
- @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.
+ @retval EFI_SUCCESS The blob was verified successfully or was not
+ found in the hash table.
+ @retval EFI_ACCESS_DENIED Kernel hashes not supported but the boot can
+ continue safely.
**/
EFI_STATUS
EFIAPI
VerifyBlob (
IN CONST CHAR16 *BlobName,
IN CONST VOID *Buf,
- IN UINT32 BufSize
+ IN UINT32 BufSize,
+ IN EFI_STATUS FetchStatus
);
#endif
diff --git a/OvmfPkg/Library/BlobVerifierLibNull/BlobVerifierNull.c b/OvmfPkg/Library/BlobVerifierLibNull/BlobVerifierNull.c index e817c3c..db53205 100644 --- a/OvmfPkg/Library/BlobVerifierLibNull/BlobVerifierNull.c +++ b/OvmfPkg/Library/BlobVerifierLibNull/BlobVerifierNull.c @@ -16,18 +16,21 @@ @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
+ @param[in] FetchStatus The status of the fetch of this blob
- @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.
+ @retval EFI_SUCCESS The blob was verified successfully or was not
+ found in the hash table.
+ @retval EFI_ACCESS_DENIED Kernel hashes not supported but the boot can
+ continue safely.
**/
EFI_STATUS
EFIAPI
VerifyBlob (
IN CONST CHAR16 *BlobName,
IN CONST VOID *Buf,
- IN UINT32 BufSize
+ IN UINT32 BufSize,
+ IN EFI_STATUS FetchStatus
)
{
- return EFI_SUCCESS;
+ return FetchStatus;
}
diff --git a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c index 3c12085..cf58c97 100644 --- a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c +++ b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c @@ -1042,6 +1042,7 @@ QemuKernelLoaderFsDxeEntrypoint ( KERNEL_BLOB *CurrentBlob;
KERNEL_BLOB *KernelBlob;
EFI_STATUS Status;
+ EFI_STATUS FetchStatus;
EFI_HANDLE FileSystemHandle;
EFI_HANDLE InitrdLoadFile2Handle;
@@ -1060,15 +1061,13 @@ QemuKernelLoaderFsDxeEntrypoint ( //
for (BlobType = 0; BlobType < KernelBlobTypeMax; ++BlobType) {
CurrentBlob = &mKernelBlob[BlobType];
- Status = FetchBlob (CurrentBlob);
- if (EFI_ERROR (Status)) {
- goto FreeBlobs;
- }
+ FetchStatus = FetchBlob (CurrentBlob);
Status = VerifyBlob (
CurrentBlob->Name,
CurrentBlob->Data,
- CurrentBlob->Size
+ CurrentBlob->Size,
+ FetchStatus
);
if (EFI_ERROR (Status)) {
goto FreeBlobs;
|