[edk2-devel] [PATCH 04/11] SecurityPkg/DxeImageVerificationHandler: narrow down PE/COFF hash status
Laszlo Ersek
lersek at redhat.com
Thu Jan 16 19:06:58 UTC 2020
Inside the "for" loop that scans the signatures of the image, we call
HashPeImageByType(), and assign its return value to "Status".
Beyond the immediate retval check, this assignment is useless (never
consumed). That's because a subsequent access to "Status" may only be one
of the following:
- the "Status" assignment when we call HashPeImageByType() in the next
iteration of the loop,
- the "Status = EFI_ACCESS_DENIED" assignment right after the final
"IsVerified" check.
To make it clear that the assignment is only useful for the immediate
HashPeImageByType() retval check, introduce a specific helper variable,
called "HashStatus".
This patch is a no-op, functionally.
Cc: Chao Zhang <chao.b.zhang at intel.com>
Cc: Jian J Wang <jian.j.wang at intel.com>
Cc: Jiewen Yao <jiewen.yao at intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2129
Signed-off-by: Laszlo Ersek <lersek at redhat.com>
---
SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c b/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
index e6c8a5408752..5cc82c1b3b22 100644
--- a/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
+++ b/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
@@ -1556,349 +1556,350 @@ EFIAPI
DxeImageVerificationHandler (
IN UINT32 AuthenticationStatus,
IN CONST EFI_DEVICE_PATH_PROTOCOL *File,
IN VOID *FileBuffer,
IN UINTN FileSize,
IN BOOLEAN BootPolicy
)
{
EFI_STATUS Status;
EFI_IMAGE_DOS_HEADER *DosHdr;
BOOLEAN IsVerified;
EFI_SIGNATURE_LIST *SignatureList;
UINTN SignatureListSize;
EFI_SIGNATURE_DATA *Signature;
EFI_IMAGE_EXECUTION_ACTION Action;
WIN_CERTIFICATE *WinCertificate;
UINT32 Policy;
UINT8 *SecureBoot;
PE_COFF_LOADER_IMAGE_CONTEXT ImageContext;
UINT32 NumberOfRvaAndSizes;
WIN_CERTIFICATE_EFI_PKCS *PkcsCertData;
WIN_CERTIFICATE_UEFI_GUID *WinCertUefiGuid;
UINT8 *AuthData;
UINTN AuthDataSize;
EFI_IMAGE_DATA_DIRECTORY *SecDataDir;
UINT32 OffSet;
CHAR16 *NameStr;
RETURN_STATUS PeCoffStatus;
+ EFI_STATUS HashStatus;
SignatureList = NULL;
SignatureListSize = 0;
WinCertificate = NULL;
SecDataDir = NULL;
PkcsCertData = NULL;
Action = EFI_IMAGE_EXECUTION_AUTH_UNTESTED;
Status = EFI_ACCESS_DENIED;
IsVerified = FALSE;
//
// Check the image type and get policy setting.
//
switch (GetImageType (File)) {
case IMAGE_FROM_FV:
Policy = ALWAYS_EXECUTE;
break;
case IMAGE_FROM_OPTION_ROM:
Policy = PcdGet32 (PcdOptionRomImageVerificationPolicy);
break;
case IMAGE_FROM_REMOVABLE_MEDIA:
Policy = PcdGet32 (PcdRemovableMediaImageVerificationPolicy);
break;
case IMAGE_FROM_FIXED_MEDIA:
Policy = PcdGet32 (PcdFixedMediaImageVerificationPolicy);
break;
default:
Policy = DENY_EXECUTE_ON_SECURITY_VIOLATION;
break;
}
//
// If policy is always/never execute, return directly.
//
if (Policy == ALWAYS_EXECUTE) {
return EFI_SUCCESS;
}
if (Policy == NEVER_EXECUTE) {
return EFI_ACCESS_DENIED;
}
//
// The policy QUERY_USER_ON_SECURITY_VIOLATION and ALLOW_EXECUTE_ON_SECURITY_VIOLATION
// violates the UEFI spec and has been removed.
//
ASSERT (Policy != QUERY_USER_ON_SECURITY_VIOLATION && Policy != ALLOW_EXECUTE_ON_SECURITY_VIOLATION);
if (Policy == QUERY_USER_ON_SECURITY_VIOLATION || Policy == ALLOW_EXECUTE_ON_SECURITY_VIOLATION) {
CpuDeadLoop ();
}
GetEfiGlobalVariable2 (EFI_SECURE_BOOT_MODE_NAME, (VOID**)&SecureBoot, NULL);
//
// Skip verification if SecureBoot variable doesn't exist.
//
if (SecureBoot == NULL) {
return EFI_SUCCESS;
}
//
// Skip verification if SecureBoot is disabled but not AuditMode
//
if (*SecureBoot == SECURE_BOOT_MODE_DISABLE) {
FreePool (SecureBoot);
return EFI_SUCCESS;
}
FreePool (SecureBoot);
//
// Read the Dos header.
//
if (FileBuffer == NULL) {
return EFI_INVALID_PARAMETER;
}
mImageBase = (UINT8 *) FileBuffer;
mImageSize = FileSize;
ZeroMem (&ImageContext, sizeof (ImageContext));
ImageContext.Handle = (VOID *) FileBuffer;
ImageContext.ImageRead = (PE_COFF_LOADER_READ_FILE) DxeImageVerificationLibImageRead;
//
// Get information about the image being loaded
//
PeCoffStatus = PeCoffLoaderGetImageInfo (&ImageContext);
if (RETURN_ERROR (PeCoffStatus)) {
//
// The information can't be got from the invalid PeImage
//
DEBUG ((DEBUG_INFO, "DxeImageVerificationLib: PeImage invalid. Cannot retrieve image information.\n"));
goto Done;
}
DosHdr = (EFI_IMAGE_DOS_HEADER *) mImageBase;
if (DosHdr->e_magic == EFI_IMAGE_DOS_SIGNATURE) {
//
// DOS image header is present,
// so read the PE header after the DOS image header.
//
mPeCoffHeaderOffset = DosHdr->e_lfanew;
} else {
mPeCoffHeaderOffset = 0;
}
//
// Check PE/COFF image.
//
mNtHeader.Pe32 = (EFI_IMAGE_NT_HEADERS32 *) (mImageBase + mPeCoffHeaderOffset);
if (mNtHeader.Pe32->Signature != EFI_IMAGE_NT_SIGNATURE) {
//
// It is not a valid Pe/Coff file.
//
DEBUG ((DEBUG_INFO, "DxeImageVerificationLib: Not a valid PE/COFF image.\n"));
goto Done;
}
if (mNtHeader.Pe32->OptionalHeader.Magic == EFI_IMAGE_NT_OPTIONAL_HDR32_MAGIC) {
//
// Use PE32 offset.
//
NumberOfRvaAndSizes = mNtHeader.Pe32->OptionalHeader.NumberOfRvaAndSizes;
if (NumberOfRvaAndSizes > EFI_IMAGE_DIRECTORY_ENTRY_SECURITY) {
SecDataDir = (EFI_IMAGE_DATA_DIRECTORY *) &mNtHeader.Pe32->OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY];
}
} else {
//
// Use PE32+ offset.
//
NumberOfRvaAndSizes = mNtHeader.Pe32Plus->OptionalHeader.NumberOfRvaAndSizes;
if (NumberOfRvaAndSizes > EFI_IMAGE_DIRECTORY_ENTRY_SECURITY) {
SecDataDir = (EFI_IMAGE_DATA_DIRECTORY *) &mNtHeader.Pe32Plus->OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY];
}
}
//
// Start Image Validation.
//
if (SecDataDir == NULL || SecDataDir->Size == 0) {
//
// This image is not signed. The SHA256 hash value of the image must match a record in the security database "db",
// and not be reflected in the security data base "dbx".
//
if (!HashPeImage (HASHALG_SHA256)) {
DEBUG ((DEBUG_INFO, "DxeImageVerificationLib: Failed to hash this image using %s.\n", mHashTypeStr));
goto Done;
}
if (IsSignatureFoundInDatabase (EFI_IMAGE_SECURITY_DATABASE1, mImageDigest, &mCertType, mImageDigestSize)) {
//
// Image Hash is in forbidden database (DBX).
//
DEBUG ((DEBUG_INFO, "DxeImageVerificationLib: Image is not signed and %s hash of image is forbidden by DBX.\n", mHashTypeStr));
goto Done;
}
if (IsSignatureFoundInDatabase (EFI_IMAGE_SECURITY_DATABASE, mImageDigest, &mCertType, mImageDigestSize)) {
//
// Image Hash is in allowed database (DB).
//
return EFI_SUCCESS;
}
//
// Image Hash is not found in both forbidden and allowed database.
//
DEBUG ((DEBUG_INFO, "DxeImageVerificationLib: Image is not signed and %s hash of image is not found in DB/DBX.\n", mHashTypeStr));
goto Done;
}
//
// Verify the signature of the image, multiple signatures are allowed as per PE/COFF Section 4.7
// "Attribute Certificate Table".
// The first certificate starts at offset (SecDataDir->VirtualAddress) from the start of the file.
//
for (OffSet = SecDataDir->VirtualAddress;
OffSet < (SecDataDir->VirtualAddress + SecDataDir->Size);
OffSet += (WinCertificate->dwLength + ALIGN_SIZE (WinCertificate->dwLength))) {
WinCertificate = (WIN_CERTIFICATE *) (mImageBase + OffSet);
if ((SecDataDir->VirtualAddress + SecDataDir->Size - OffSet) <= sizeof (WIN_CERTIFICATE) ||
(SecDataDir->VirtualAddress + SecDataDir->Size - OffSet) < WinCertificate->dwLength) {
break;
}
//
// Verify the image's Authenticode signature, only DER-encoded PKCS#7 signed data is supported.
//
if (WinCertificate->wCertificateType == WIN_CERT_TYPE_PKCS_SIGNED_DATA) {
//
// The certificate is formatted as WIN_CERTIFICATE_EFI_PKCS which is described in the
// Authenticode specification.
//
PkcsCertData = (WIN_CERTIFICATE_EFI_PKCS *) WinCertificate;
if (PkcsCertData->Hdr.dwLength <= sizeof (PkcsCertData->Hdr)) {
break;
}
AuthData = PkcsCertData->CertData;
AuthDataSize = PkcsCertData->Hdr.dwLength - sizeof(PkcsCertData->Hdr);
} else if (WinCertificate->wCertificateType == WIN_CERT_TYPE_EFI_GUID) {
//
// The certificate is formatted as WIN_CERTIFICATE_UEFI_GUID which is described in UEFI Spec.
//
WinCertUefiGuid = (WIN_CERTIFICATE_UEFI_GUID *) WinCertificate;
if (WinCertUefiGuid->Hdr.dwLength <= OFFSET_OF(WIN_CERTIFICATE_UEFI_GUID, CertData)) {
break;
}
if (!CompareGuid (&WinCertUefiGuid->CertType, &gEfiCertPkcs7Guid)) {
continue;
}
AuthData = WinCertUefiGuid->CertData;
AuthDataSize = WinCertUefiGuid->Hdr.dwLength - OFFSET_OF(WIN_CERTIFICATE_UEFI_GUID, CertData);
} else {
if (WinCertificate->dwLength < sizeof (WIN_CERTIFICATE)) {
break;
}
continue;
}
- Status = HashPeImageByType (AuthData, AuthDataSize);
- if (EFI_ERROR (Status)) {
+ HashStatus = HashPeImageByType (AuthData, AuthDataSize);
+ if (EFI_ERROR (HashStatus)) {
continue;
}
//
// Check the digital signature against the revoked certificate in forbidden database (dbx).
//
if (IsForbiddenByDbx (AuthData, AuthDataSize)) {
Action = EFI_IMAGE_EXECUTION_AUTH_SIG_FAILED;
IsVerified = FALSE;
break;
}
//
// Check the digital signature against the valid certificate in allowed database (db).
//
if (!IsVerified) {
if (IsAllowedByDb (AuthData, AuthDataSize)) {
IsVerified = TRUE;
}
}
//
// Check the image's hash value.
//
if (IsSignatureFoundInDatabase (EFI_IMAGE_SECURITY_DATABASE1, mImageDigest, &mCertType, mImageDigestSize)) {
Action = EFI_IMAGE_EXECUTION_AUTH_SIG_FOUND;
DEBUG ((DEBUG_INFO, "DxeImageVerificationLib: Image is signed but %s hash of image is found in DBX.\n", mHashTypeStr));
IsVerified = FALSE;
break;
}
if (!IsVerified) {
if (IsSignatureFoundInDatabase (EFI_IMAGE_SECURITY_DATABASE, mImageDigest, &mCertType, mImageDigestSize)) {
IsVerified = TRUE;
} else {
DEBUG ((DEBUG_INFO, "DxeImageVerificationLib: Image is signed but signature is not allowed by DB and %s hash of image is not found in DB/DBX.\n", mHashTypeStr));
}
}
}
if (OffSet != (SecDataDir->VirtualAddress + SecDataDir->Size)) {
//
// The Size in Certificate Table or the attribute certificate table is corrupted.
//
IsVerified = FALSE;
}
if (IsVerified) {
return EFI_SUCCESS;
}
Status = EFI_ACCESS_DENIED;
if (Action == EFI_IMAGE_EXECUTION_AUTH_SIG_FAILED || Action == EFI_IMAGE_EXECUTION_AUTH_SIG_FOUND) {
//
// Get image hash value as signature of executable.
//
SignatureListSize = sizeof (EFI_SIGNATURE_LIST) + sizeof (EFI_SIGNATURE_DATA) - 1 + mImageDigestSize;
SignatureList = (EFI_SIGNATURE_LIST *) AllocateZeroPool (SignatureListSize);
if (SignatureList == NULL) {
Status = EFI_OUT_OF_RESOURCES;
goto Done;
}
SignatureList->SignatureHeaderSize = 0;
SignatureList->SignatureListSize = (UINT32) SignatureListSize;
SignatureList->SignatureSize = (UINT32) (sizeof (EFI_SIGNATURE_DATA) - 1 + mImageDigestSize);
CopyMem (&SignatureList->SignatureType, &mCertType, sizeof (EFI_GUID));
Signature = (EFI_SIGNATURE_DATA *) ((UINT8 *) SignatureList + sizeof (EFI_SIGNATURE_LIST));
CopyMem (Signature->SignatureData, mImageDigest, mImageDigestSize);
}
Done:
if (Status != EFI_SUCCESS) {
//
// Policy decides to defer or reject the image; add its information in image executable information table.
//
NameStr = ConvertDevicePathToText (File, FALSE, TRUE);
AddImageExeInfo (Action, NameStr, File, SignatureList, SignatureListSize);
if (NameStr != NULL) {
DEBUG((EFI_D_INFO, "The image doesn't pass verification: %s\n", NameStr));
FreePool(NameStr);
}
Status = EFI_SECURITY_VIOLATION;
}
if (SignatureList != NULL) {
FreePool (SignatureList);
}
return Status;
}
/**
On Ready To Boot Services Event notification handler.
Add the image execution information table if it is not in system configuration table.
@param[in] Event Event whose notification function is being invoked
@param[in] Context Pointer to the notification function's context
**/
--
2.19.1.3.g30247aa5d201
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