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Add image verification

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This commit is contained in:
Matthew Garrett 2012-05-30 18:36:46 -04:00
parent 9d56c38fd1
commit 7f0553356c
4 changed files with 242 additions and 30 deletions
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17
Makefile
View File

@ -3,11 +3,11 @@ ARCH = $(shell uname -m | sed s,i[3456789]86,ia32,)
LIB_PATH = /usr/lib64
EFI_INCLUDE = /usr/include/efi
EFI_INCLUDES = -I$(EFI_INCLUDE) -I$(EFI_INCLUDE)/$(ARCH) -I$(EFI_INCLUDE)/protocol
EFI_INCLUDES = -nostdinc -I../Cryptlib -I../Cryptlib/Include -I$(EFI_INCLUDE) -I$(EFI_INCLUDE)/$(ARCH) -I$(EFI_INCLUDE)/protocol
EFI_PATH = /usr/lib64/gnuefi
LIB_GCC = $(shell $(CC) -print-libgcc-file-name)
EFI_LIBS = -lefi -lgnuefi $(LIB_GCC)
EFI_LIBS = -lefi -lgnuefi --start-group ../Cryptlib/libcryptlib.a ../Cryptlib/OpenSSL/libopenssl.a --end-group $(LIB_GCC)
EFI_CRT_OBJS = $(EFI_PATH)/crt0-efi-$(ARCH).o
EFI_LDS = $(EFI_PATH)/elf_$(ARCH)_efi.lds
@ -19,22 +19,23 @@ CFLAGS = -O2 -fno-stack-protector -fno-strict-aliasing -fpic -fshort-wchar \
ifeq ($(ARCH),x86_64)
CFLAGS += -DEFI_FUNCTION_WRAPPER
endif
LDFLAGS = -nostdlib -znocombreloc -T $(EFI_LDS) -shared -Bsymbolic -L$(EFI_PATH) -L$(LIB_PATH) $(EFI_CRT_OBJS)
LDFLAGS = -nostdlib -znocombreloc -T $(EFI_LDS) -shared -Bsymbolic -L$(EFI_PATH) -L$(LIB_PATH) -L../Cryptlib -L../Cryptlib/OpenSSL $(EFI_CRT_OBJS)
TARGET = shim.efi
OBJS = shim.o
all: $(TARGET)
shim.efi: $(OBJS)
shim.efi: shim.so
%.efi: %.o
$(LD) $(LDFLAGS) $^ -o $@ $(EFI_LIBS)
shim.so: $(OBJS)
$(LD) -o $@ $(LDFLAGS) $^ $(EFI_LIBS)
%.efi: %.so
objcopy -j .text -j .sdata -j .data \
-j .dynamic -j .dynsym -j .rel \
-j .rela -j .reloc \
--target=efi-app-$(ARCH) $@
strip $@
--target=efi-app-$(ARCH) $^ $@
clean:
rm -f $(TARGET) $(OBJS)

17
PeImage.h
View File

@ -760,6 +760,21 @@ typedef union {
EFI_IMAGE_OPTIONAL_HEADER_UNION *Union;
} EFI_IMAGE_OPTIONAL_HEADER_PTR_UNION;
typedef struct _WIN_CERTIFICATE {
UINT32 dwLength;
UINT16 wRevision;
UINT16 wCertificateType;
//UINT8 bCertificate[ANYSIZE_ARRAY];
} WIN_CERTIFICATE;
typedef struct {
WIN_CERTIFICATE Hdr;
UINT8 CertData[1];
} WIN_CERTIFICATE_EFI_PKCS;
#define SHA256_DIGEST_SIZE 32
#define WIN_CERT_TYPE_PKCS_SIGNED_DATA 0x0002
typedef struct {
UINT64 ImageAddress;
UINT64 ImageSize;
@ -769,7 +784,9 @@ typedef struct {
UINT16 NumberOfSections;
EFI_IMAGE_SECTION_HEADER *FirstSection;
EFI_IMAGE_DATA_DIRECTORY *RelocDir;
EFI_IMAGE_DATA_DIRECTORY *SecDir;
UINT64 NumberOfRvaAndSizes;
EFI_IMAGE_OPTIONAL_HEADER_UNION *PEHdr;
} PE_COFF_LOADER_IMAGE_CONTEXT;
#endif

1
cert.h Normal file
View File

@ -0,0 +1 @@
static UINT8 cert[] = {0x00};

237
shim.c
View File

@ -1,17 +1,15 @@
/* Read path */
/* Load real bootloader */
/* Check signature */
/* Relocate real bootloader */
/* Jump to real bootloader */
#include <efi.h>
#include <efilib.h>
#include <Library/BaseCryptLib.h>
#include "PeImage.h"
EFI_SYSTEM_TABLE *systab;
EFI_STATUS (EFIAPI *entry_point) (EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *system_table);
static EFI_SYSTEM_TABLE *systab;
static EFI_STATUS (EFIAPI *entry_point) (EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *system_table);
EFI_STATUS load_grub (EFI_HANDLE image_handle, void **grubdata, int *grubsize)
#include "cert.h"
static EFI_STATUS load_grub (EFI_HANDLE image_handle, void **grubdata,
int *grubsize)
{
EFI_GUID loaded_image_protocol = LOADED_IMAGE_PROTOCOL;
EFI_GUID simple_file_system_protocol = SIMPLE_FILE_SYSTEM_PROTOCOL;
@ -25,7 +23,7 @@ EFI_STATUS load_grub (EFI_HANDLE image_handle, void **grubdata, int *grubsize)
CHAR16 *PathName;
CHAR16 *Dir;
EFI_HANDLE device;
unsigned int buffersize = 0;
unsigned int buffersize = sizeof(EFI_FILE_INFO);
int i;
efi_status = uefi_call_wrapper(BS->HandleProtocol, 3, image_handle,
@ -38,7 +36,6 @@ EFI_STATUS load_grub (EFI_HANDLE image_handle, void **grubdata, int *grubsize)
DevicePathSubType(li->FilePath) != MEDIA_FILEPATH_DP)
return EFI_NOT_FOUND;
device = li->DeviceHandle;
efi_status = uefi_call_wrapper(BS->HandleProtocol, 3, device,
@ -63,10 +60,18 @@ EFI_STATUS load_grub (EFI_HANDLE image_handle, void **grubdata, int *grubsize)
0);
if (efi_status != EFI_SUCCESS) {
Print(L"Failed to open %s - %lx\n", FilePath->PathName, efi_status);
Print(L"Failed to open %s - %lx\n", FilePath->PathName,
efi_status);
return efi_status;
}
fileinfo = AllocatePool(buffersize);
if (!fileinfo) {
Print(L"Unable to allocate info buffer\n");
return EFI_OUT_OF_RESOURCES;
}
efi_status = uefi_call_wrapper(grub->GetInfo, 4, grub, &file_info_id,
&buffersize, fileinfo);
@ -113,7 +118,7 @@ EFI_STATUS load_grub (EFI_HANDLE image_handle, void **grubdata, int *grubsize)
StrCpy(PathName, Dir);
StrCat(PathName, L"\\grub.efi");
StrCat(PathName, L"grub.efi");
efi_status = uefi_call_wrapper(root->Open, 5, root, &grub, PathName,
EFI_FILE_MODE_READ, 0);
@ -154,7 +159,7 @@ EFI_STATUS load_grub (EFI_HANDLE image_handle, void **grubdata, int *grubsize)
*grubdata);
if (efi_status != EFI_SUCCESS) {
Print(L"Unexpected return from initial read\n");
Print(L"Unexpected return from initial read: %x, buffersize %x\n", efi_status, buffersize);
return efi_status;
}
@ -168,7 +173,7 @@ EFI_STATUS load_grub (EFI_HANDLE image_handle, void **grubdata, int *grubsize)
return EFI_SUCCESS;
}
EFI_STATUS read_header(void *grubdata, PE_COFF_LOADER_IMAGE_CONTEXT *context)
static EFI_STATUS read_header(void *grubdata, PE_COFF_LOADER_IMAGE_CONTEXT *context)
{
EFI_IMAGE_DOS_HEADER *DosHdr = grubdata;
EFI_IMAGE_OPTIONAL_HEADER_UNION *PEHdr = grubdata;
@ -191,8 +196,8 @@ EFI_STATUS read_header(void *grubdata, PE_COFF_LOADER_IMAGE_CONTEXT *context)
return EFI_UNSUPPORTED;
}
context->PEHdr = PEHdr;
context->ImageAddress = PEHdr->Pe32Plus.OptionalHeader.ImageBase;
PEHdr->Pe32Plus.OptionalHeader.ImageBase = (UINT64)grubdata;
context->ImageSize = (UINT64)PEHdr->Pe32Plus.OptionalHeader.SizeOfImage;
context->SizeOfHeaders = PEHdr->Pe32Plus.OptionalHeader.SizeOfHeaders;
context->EntryPoint = PEHdr->Pe32Plus.OptionalHeader.AddressOfEntryPoint;
@ -200,19 +205,196 @@ EFI_STATUS read_header(void *grubdata, PE_COFF_LOADER_IMAGE_CONTEXT *context)
context->NumberOfRvaAndSizes = PEHdr->Pe32Plus.OptionalHeader.NumberOfRvaAndSizes;
context->NumberOfSections = PEHdr->Pe32.FileHeader.NumberOfSections;
context->FirstSection = (EFI_IMAGE_SECTION_HEADER *)((char *)PEHdr + PEHdr->Pe32.FileHeader.SizeOfOptionalHeader + sizeof(UINT32) + sizeof(EFI_IMAGE_FILE_HEADER));
context->SecDir = (EFI_IMAGE_DATA_DIRECTORY *) &PEHdr->Pe32Plus.OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY];
if (context->SecDir->VirtualAddress >= context->ImageSize) {
Print(L"Malformed security header\n");
return EFI_INVALID_PARAMETER;
}
if (context->SecDir->Size == 0) {
Print(L"Empty security header\n");
return EFI_INVALID_PARAMETER;
}
return EFI_SUCCESS;
}
void *ImageAddress (void *image, int size, unsigned int address)
static void *ImageAddress (void *image, int size, unsigned int address)
{
if (address > size)
return 0;
return NULL;
return image + address;
}
EFI_STATUS relocate_grub (PE_COFF_LOADER_IMAGE_CONTEXT *context, void *grubdata)
static EFI_STATUS verify_grub (PE_COFF_LOADER_IMAGE_CONTEXT *context, char *grubdata, int grubsize)
{
unsigned int size = grubsize;
unsigned int ctxsize;
void *ctx;
UINT8 hash[SHA256_DIGEST_SIZE];
EFI_STATUS status = EFI_ACCESS_DENIED;
char *hashbase;
unsigned int hashsize;
WIN_CERTIFICATE_EFI_PKCS *cer;
unsigned int SumOfBytesHashed, SumOfSectionBytes;
unsigned int index, pos;
EFI_IMAGE_SECTION_HEADER *Section;
EFI_IMAGE_SECTION_HEADER *SectionHeader;
EFI_IMAGE_SECTION_HEADER *SectionCache;
cert = ImageAddress (grubdata, size, context->SecDir->VirtualAddress);
if (cer->Hdr.wCertificateType != WIN_CERT_TYPE_PKCS_SIGNED_DATA) {
Print(L"Unsupported certificate type %x\n",
cert->Hdr.wCertificateType);
return EFI_UNSUPPORTED;
}
/* Check which kind of hash */
ctxsize = Sha256GetContextSize();
ctx = AllocatePool(ctxsize);
if (!ctx) {
Print(L"Unable to allocate memory for hash context\n");
return EFI_OUT_OF_RESOURCES;
}
if (!Sha256Init(ctx)) {
Print(L"Unable to initialise hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Hash start to checksum */
hashbase = grubdata;
hashsize = (char *)&context->PEHdr->Pe32.OptionalHeader.CheckSum -
hashbase;
if (!(Sha256Update(ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Hash post-checksum to start of certificate table */
hashbase = (char *)&context->PEHdr->Pe32.OptionalHeader.CheckSum +
sizeof (int);
hashsize = (char *)context->SecDir - hashbase;
if (!(Sha256Update(ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Hash end of certificate table to end of image header */
hashbase = (char *) &context->PEHdr->Pe32Plus.OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY + 1];
hashsize = context->PEHdr->Pe32Plus.OptionalHeader.SizeOfHeaders -
(int) ((char *) (&context->PEHdr->Pe32Plus.OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY + 1]) - grubdata);
if (!(Sha256Update(ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Sort sections and hash SizeOfRawData of each section */
SumOfBytesHashed = context->PEHdr->Pe32Plus.OptionalHeader.SizeOfHeaders;
Section = (EFI_IMAGE_SECTION_HEADER *) (
(char *)context->PEHdr + sizeof (UINT32) +
sizeof (EFI_IMAGE_FILE_HEADER) +
context->PEHdr->Pe32.FileHeader.SizeOfOptionalHeader
);
SectionCache = Section;
for (index = 0, SumOfSectionBytes = 0; index < context->PEHdr->Pe32.FileHeader.NumberOfSections; index++, SectionCache++) {
SumOfSectionBytes += SectionCache->SizeOfRawData;
}
if (SumOfSectionBytes >= grubsize) {
Print(L"Malformed binary: %x %x\n", SumOfSectionBytes, size);
status = EFI_INVALID_PARAMETER;
goto done;
}
SectionHeader = (EFI_IMAGE_SECTION_HEADER *) AllocateZeroPool (sizeof (EFI_IMAGE_SECTION_HEADER) * context->PEHdr->Pe32.FileHeader.NumberOfSections);
if (SectionHeader == NULL) {
Print(L"Unable to allocate section header\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Sort the section headers */
for (index = 0; index < context->PEHdr->Pe32.FileHeader.NumberOfSections; index++) {
pos = index;
while ((pos > 0) && (Section->PointerToRawData < SectionHeader[pos - 1].PointerToRawData)) {
CopyMem (&SectionHeader[pos], &SectionHeader[pos - 1], sizeof (EFI_IMAGE_SECTION_HEADER));
pos--;
}
CopyMem (&SectionHeader[pos], Section, sizeof (EFI_IMAGE_SECTION_HEADER));
Section += 1;
}
/* Hash the sections */
for (index = 0; index < context->PEHdr->Pe32.FileHeader.NumberOfSections; index++) {
Section = &SectionHeader[index];
if (Section->SizeOfRawData == 0) {
continue;
}
hashbase = ImageAddress(grubdata, size, Section->PointerToRawData);
hashsize = (unsigned int) Section->SizeOfRawData;
if (!(Sha256Update(ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
SumOfBytesHashed += Section->SizeOfRawData;
}
/* Hash all remaining data */
if (size > SumOfBytesHashed) {
hashbase = grubdata + SumOfBytesHashed;
hashsize = (unsigned int)(
size -
context->PEHdr->Pe32Plus.OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_SECURITY].Size -
SumOfBytesHashed);
if (!(Sha256Update(ctx, hashbase, hashsize))) {
Print(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
}
if (!(Sha256Final(ctx, hash))) {
Print(L"Unable to finalise hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
if (!AuthenticodeVerify(WinCertificate->CertData,
context->SecDir->Size - sizeof(WinCertificate->Hdr),
cert, sizeof(cert), hash,
SHA256_DIGEST_SIZE)) {
Print(L"Invalid signature\n");
status = EFI_ACCESS_DENIED;
} else {
status = EFI_SUCCESS;
}
done:
if (ctx)
FreePool(ctx);
return status;
}
static EFI_STATUS relocate_grub (PE_COFF_LOADER_IMAGE_CONTEXT *context, void *grubdata)
{
EFI_IMAGE_BASE_RELOCATION *RelocBase, *RelocBaseEnd;
UINT64 Adjust;
@ -224,6 +406,8 @@ EFI_STATUS relocate_grub (PE_COFF_LOADER_IMAGE_CONTEXT *context, void *grubdata)
int size = context->ImageSize;
void *ImageEnd = (char *)grubdata + size;
context->PEHdr->Pe32Plus.OptionalHeader.ImageBase = (UINT64)grubdata;
if (context->NumberOfRvaAndSizes <= EFI_IMAGE_DIRECTORY_ENTRY_BASERELOC) {
Print(L"Image has no relocation entry\n");
return EFI_UNSUPPORTED;
@ -311,7 +495,7 @@ EFI_STATUS relocate_grub (PE_COFF_LOADER_IMAGE_CONTEXT *context, void *grubdata)
}
EFI_STATUS handle_grub (void *grubdata, int grubsize)
static EFI_STATUS handle_grub (void *grubdata, int grubsize)
{
EFI_STATUS efi_status;
char *buffer;
@ -319,13 +503,20 @@ EFI_STATUS handle_grub (void *grubdata, int grubsize)
EFI_IMAGE_SECTION_HEADER *Section;
char *base, *end;
PE_COFF_LOADER_IMAGE_CONTEXT context;
efi_status = read_header(grubdata, &context);
if (efi_status != EFI_SUCCESS) {
Print(L"Failed to read header\n");
return efi_status;
}
efi_status = verify_grub(&context, grubdata, grubsize);
if (efi_status != EFI_SUCCESS) {
Print(L"Verification failed\n");
return efi_status;
}
buffer = AllocatePool(context.ImageSize);
if (!buffer) {
@ -387,8 +578,10 @@ EFI_STATUS efi_main (EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *passed_systab)
efi_status = load_grub(image_handle, &grubdata, &grubsize);
if (efi_status != EFI_SUCCESS)
if (efi_status != EFI_SUCCESS) {
Print(L"Failed to load grub\n");
return efi_status;
}
efi_status = handle_grub(grubdata, grubsize);