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shim.c
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/*
* shim - trivial UEFI first-stage bootloader
*
* Copyright 2012 Red Hat, Inc <[email protected]>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Significant portions of this code are derived from Tianocore
* (http://tianocore.sf.net) and are Copyright 2009-2012 Intel
* Corporation.
*/
#include <efi.h>
#include <efilib.h>
#include <Library/BaseCryptLib.h>
#include "PeImage.h"
#include "shim.h"
#include "netboot.h"
#include "httpboot.h"
#include "shim_cert.h"
#include "replacements.h"
#include "tpm.h"
#include "ucs2.h"
#include "guid.h"
#include "variables.h"
#include "efiauthenticated.h"
#include "security_policy.h"
#include "console.h"
#include "version.h"
#include <stdarg.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#define FALLBACK L"\\fb" EFI_ARCH L".efi"
#define MOK_MANAGER L"\\mm" EFI_ARCH L".efi"
#define OID_EKU_MODSIGN "1.3.6.1.4.1.2312.16.1.2"
static EFI_SYSTEM_TABLE *systab;
static EFI_HANDLE global_image_handle;
static EFI_STATUS (EFIAPI *entry_point) (EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *system_table);
static CHAR16 *second_stage;
static void *load_options;
static UINT32 load_options_size;
static UINT8 in_protocol;
#define perror(fmt, ...) ({ \
UINTN __perror_ret = 0; \
if (!in_protocol) \
__perror_ret = Print((fmt), ##__VA_ARGS__); \
__perror_ret; \
})
EFI_GUID SHIM_LOCK_GUID = { 0x605dab50, 0xe046, 0x4300, {0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23} };
/*
* The vendor certificate used for validating the second stage loader
*/
extern struct {
UINT32 vendor_cert_size;
UINT32 vendor_dbx_size;
UINT32 vendor_cert_offset;
UINT32 vendor_dbx_offset;
} cert_table;
UINT32 vendor_cert_size;
UINT32 vendor_dbx_size;
UINT8 *vendor_cert;
UINT8 *vendor_dbx;
/*
* indicator of how an image has been verified
*/
verification_method_t verification_method;
int loader_is_participating;
#define EFI_IMAGE_SECURITY_DATABASE_GUID { 0xd719b2cb, 0x3d3a, 0x4596, { 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f }}
UINT8 user_insecure_mode;
UINT8 ignore_db;
typedef enum {
DATA_FOUND,
DATA_NOT_FOUND,
VAR_NOT_FOUND
} CHECK_STATUS;
typedef struct {
UINT32 MokSize;
UINT8 *Mok;
} MokListNode;
/*
* Perform basic bounds checking of the intra-image pointers
*/
static void *ImageAddress (void *image, unsigned int size, unsigned int address)
{
if (address > size)
return NULL;
return image + address;
}
/* here's a chart:
* i686 x86_64 aarch64
* 64-on-64: nyet yes yes
* 64-on-32: nyet yes nyet
* 32-on-32: yes yes no
*/
static int
allow_64_bit(void)
{
#if defined(__x86_64__) || defined(__aarch64__)
return 1;
#elif defined(__i386__) || defined(__i686__)
/* Right now blindly assuming the kernel will correctly detect this
* and /halt the system/ if you're not really on a 64-bit cpu */
if (in_protocol)
return 1;
return 0;
#else /* assuming everything else is 32-bit... */
return 0;
#endif
}
static int
allow_32_bit(void)
{
#if defined(__x86_64__)
#if defined(ALLOW_32BIT_KERNEL_ON_X64)
if (in_protocol)
return 1;
return 0;
#else
return 0;
#endif
#elif defined(__i386__) || defined(__i686__)
return 1;
#elif defined(__arch64__)
return 0;
#else /* assuming everything else is 32-bit... */
return 1;
#endif
}
static int
image_is_64_bit(EFI_IMAGE_OPTIONAL_HEADER_UNION *PEHdr)
{
/* .Magic is the same offset in all cases */
if (PEHdr->Pe32Plus.OptionalHeader.Magic
== EFI_IMAGE_NT_OPTIONAL_HDR64_MAGIC)
return 1;
return 0;
}
static const UINT16 machine_type =
#if defined(__x86_64__)
IMAGE_FILE_MACHINE_X64;
#elif defined(__aarch64__)
IMAGE_FILE_MACHINE_ARM64;
#elif defined(__arm__)
IMAGE_FILE_MACHINE_ARMTHUMB_MIXED;
#elif defined(__i386__) || defined(__i486__) || defined(__i686__)
IMAGE_FILE_MACHINE_I386;
#elif defined(__ia64__)
IMAGE_FILE_MACHINE_IA64;
#else
#error this architecture is not supported by shim
#endif
static int
image_is_loadable(EFI_IMAGE_OPTIONAL_HEADER_UNION *PEHdr)
{
/* If the machine type doesn't match the binary, bail, unless
* we're in an allowed 64-on-32 scenario */
if (PEHdr->Pe32.FileHeader.Machine != machine_type) {
if (!(machine_type == IMAGE_FILE_MACHINE_I386 &&
PEHdr->Pe32.FileHeader.Machine == IMAGE_FILE_MACHINE_X64 &&
allow_64_bit())) {
return 0;
}
}
/* If it's not a header type we recognize at all, bail */
switch (PEHdr->Pe32Plus.OptionalHeader.Magic) {
case EFI_IMAGE_NT_OPTIONAL_HDR64_MAGIC:
case EFI_IMAGE_NT_OPTIONAL_HDR32_MAGIC:
break;
default:
return 0;
}
/* and now just check for general 64-vs-32 compatibility */
if (image_is_64_bit(PEHdr)) {
if (allow_64_bit())
return 1;
} else {
if (allow_32_bit())
return 1;
}
return 0;
}
/*
* Perform the actual relocation
*/
static EFI_STATUS relocate_coff (PE_COFF_LOADER_IMAGE_CONTEXT *context,
EFI_IMAGE_SECTION_HEADER *Section,
void *orig, void *data)
{
EFI_IMAGE_BASE_RELOCATION *RelocBase, *RelocBaseEnd;
UINT64 Adjust;
UINT16 *Reloc, *RelocEnd;
char *Fixup, *FixupBase, *FixupData = NULL;
UINT16 *Fixup16;
UINT32 *Fixup32;
UINT64 *Fixup64;
int size = context->ImageSize;
void *ImageEnd = (char *)orig + size;
int n = 0;
if (image_is_64_bit(context->PEHdr))
context->PEHdr->Pe32Plus.OptionalHeader.ImageBase = (UINT64)(unsigned long)data;
else
context->PEHdr->Pe32.OptionalHeader.ImageBase = (UINT32)(unsigned long)data;
/* Alright, so here's how this works:
*
* context->RelocDir gives us two things:
* - the VA the table of base relocation blocks are (maybe) to be
* mapped at (RelocDir->VirtualAddress)
* - the virtual size (RelocDir->Size)
*
* The .reloc section (Section here) gives us some other things:
* - the name! kind of. (Section->Name)
* - the virtual size (Section->VirtualSize), which should be the same
* as RelocDir->Size
* - the virtual address (Section->VirtualAddress)
* - the file section size (Section->SizeOfRawData), which is
* a multiple of OptHdr->FileAlignment. Only useful for image
* validation, not really useful for iteration bounds.
* - the file address (Section->PointerToRawData)
* - a bunch of stuff we don't use that's 0 in our binaries usually
* - Flags (Section->Characteristics)
*
* and then the thing that's actually at the file address is an array
* of EFI_IMAGE_BASE_RELOCATION structs with some values packed behind
* them. The SizeOfBlock field of this structure includes the
* structure itself, and adding it to that structure's address will
* yield the next entry in the array.
*/
RelocBase = ImageAddress(orig, size, Section->PointerToRawData);
/* RelocBaseEnd here is the address of the first entry /past/ the
* table. */
RelocBaseEnd = ImageAddress(orig, size, Section->PointerToRawData +
Section->Misc.VirtualSize);
if (!RelocBase && !RelocBaseEnd)
return EFI_SUCCESS;
if (!RelocBase || !RelocBaseEnd) {
perror(L"Reloc table overflows binary\n");
return EFI_UNSUPPORTED;
}
Adjust = (UINTN)data - context->ImageAddress;
if (Adjust == 0)
return EFI_SUCCESS;
while (RelocBase < RelocBaseEnd) {
Reloc = (UINT16 *) ((char *) RelocBase + sizeof (EFI_IMAGE_BASE_RELOCATION));
if ((RelocBase->SizeOfBlock == 0) || (RelocBase->SizeOfBlock > context->RelocDir->Size)) {
perror(L"Reloc %d block size %d is invalid\n", n, RelocBase->SizeOfBlock);
return EFI_UNSUPPORTED;
}
RelocEnd = (UINT16 *) ((char *) RelocBase + RelocBase->SizeOfBlock);
if ((void *)RelocEnd < orig || (void *)RelocEnd > ImageEnd) {
perror(L"Reloc %d entry overflows binary\n", n);
return EFI_UNSUPPORTED;
}
FixupBase = ImageAddress(data, size, RelocBase->VirtualAddress);
if (!FixupBase) {
perror(L"Reloc %d Invalid fixupbase\n", n);
return EFI_UNSUPPORTED;
}
while (Reloc < RelocEnd) {
Fixup = FixupBase + (*Reloc & 0xFFF);
switch ((*Reloc) >> 12) {
case EFI_IMAGE_REL_BASED_ABSOLUTE:
break;
case EFI_IMAGE_REL_BASED_HIGH:
Fixup16 = (UINT16 *) Fixup;
*Fixup16 = (UINT16) (*Fixup16 + ((UINT16) ((UINT32) Adjust >> 16)));
if (FixupData != NULL) {
*(UINT16 *) FixupData = *Fixup16;
FixupData = FixupData + sizeof (UINT16);
}
break;
case EFI_IMAGE_REL_BASED_LOW:
Fixup16 = (UINT16 *) Fixup;
*Fixup16 = (UINT16) (*Fixup16 + (UINT16) Adjust);
if (FixupData != NULL) {
*(UINT16 *) FixupData = *Fixup16;
FixupData = FixupData + sizeof (UINT16);
}
break;
case EFI_IMAGE_REL_BASED_HIGHLOW:
Fixup32 = (UINT32 *) Fixup;
*Fixup32 = *Fixup32 + (UINT32) Adjust;
if (FixupData != NULL) {
FixupData = ALIGN_POINTER (FixupData, sizeof (UINT32));
*(UINT32 *)FixupData = *Fixup32;
FixupData = FixupData + sizeof (UINT32);
}
break;
case EFI_IMAGE_REL_BASED_DIR64:
Fixup64 = (UINT64 *) Fixup;
*Fixup64 = *Fixup64 + (UINT64) Adjust;
if (FixupData != NULL) {
FixupData = ALIGN_POINTER (FixupData, sizeof(UINT64));
*(UINT64 *)(FixupData) = *Fixup64;
FixupData = FixupData + sizeof(UINT64);
}
break;
default:
perror(L"Reloc %d Unknown relocation\n", n);
return EFI_UNSUPPORTED;
}
Reloc += 1;
}
RelocBase = (EFI_IMAGE_BASE_RELOCATION *) RelocEnd;
n++;
}
return EFI_SUCCESS;
}
static BOOLEAN verify_x509(UINT8 *Cert, UINTN CertSize)
{
UINTN length;
if (!Cert || CertSize < 4)
return FALSE;
/*
* A DER encoding x509 certificate starts with SEQUENCE(0x30),
* the number of length bytes, and the number of value bytes.
* The size of a x509 certificate is usually between 127 bytes
* and 64KB. For convenience, assume the number of value bytes
* is 2, i.e. the second byte is 0x82.
*/
if (Cert[0] != 0x30 || Cert[1] != 0x82)
return FALSE;
length = Cert[2]<<8 | Cert[3];
if (length != (CertSize - 4))
return FALSE;
return TRUE;
}
static BOOLEAN verify_eku(UINT8 *Cert, UINTN CertSize)
{
X509 *x509;
CONST UINT8 *Temp = Cert;
EXTENDED_KEY_USAGE *eku;
ASN1_OBJECT *module_signing;
module_signing = OBJ_nid2obj(OBJ_create(OID_EKU_MODSIGN, NULL, NULL));
x509 = d2i_X509 (NULL, &Temp, (long) CertSize);
if (x509 != NULL) {
eku = X509_get_ext_d2i(x509, NID_ext_key_usage, NULL, NULL);
if (eku) {
int i = 0;
for (i = 0; i < sk_ASN1_OBJECT_num(eku); i++) {
ASN1_OBJECT *key_usage = sk_ASN1_OBJECT_value(eku, i);
if (OBJ_cmp(module_signing, key_usage) == 0)
return FALSE;
}
EXTENDED_KEY_USAGE_free(eku);
}
X509_free(x509);
}
return TRUE;
}
static CHECK_STATUS check_db_cert_in_ram(EFI_SIGNATURE_LIST *CertList,
UINTN dbsize,
WIN_CERTIFICATE_EFI_PKCS *data,
UINT8 *hash)
{
EFI_SIGNATURE_DATA *Cert;
UINTN CertSize;
BOOLEAN IsFound = FALSE;
EFI_GUID CertType = X509_GUID;
while ((dbsize > 0) && (dbsize >= CertList->SignatureListSize)) {
if (CompareGuid (&CertList->SignatureType, &CertType) == 0) {
Cert = (EFI_SIGNATURE_DATA *) ((UINT8 *) CertList + sizeof (EFI_SIGNATURE_LIST) + CertList->SignatureHeaderSize);
CertSize = CertList->SignatureSize - sizeof(EFI_GUID);
if (verify_x509(Cert->SignatureData, CertSize)) {
if (verify_eku(Cert->SignatureData, CertSize)) {
IsFound = AuthenticodeVerify (data->CertData,
data->Hdr.dwLength - sizeof(data->Hdr),
Cert->SignatureData,
CertSize,
hash, SHA256_DIGEST_SIZE);
if (IsFound)
return DATA_FOUND;
}
} else if (verbose) {
console_notify(L"Not a DER encoding x.509 Certificate");
}
}
dbsize -= CertList->SignatureListSize;
CertList = (EFI_SIGNATURE_LIST *) ((UINT8 *) CertList + CertList->SignatureListSize);
}
return DATA_NOT_FOUND;
}
static CHECK_STATUS check_db_cert(CHAR16 *dbname, EFI_GUID guid,
WIN_CERTIFICATE_EFI_PKCS *data, UINT8 *hash)
{
CHECK_STATUS rc;
EFI_STATUS efi_status;
EFI_SIGNATURE_LIST *CertList;
UINTN dbsize = 0;
UINT8 *db;
efi_status = get_variable(dbname, &db, &dbsize, guid);
if (efi_status != EFI_SUCCESS)
return VAR_NOT_FOUND;
CertList = (EFI_SIGNATURE_LIST *)db;
rc = check_db_cert_in_ram(CertList, dbsize, data, hash);
FreePool(db);
return rc;
}
/*
* Check a hash against an EFI_SIGNATURE_LIST in a buffer
*/
static CHECK_STATUS check_db_hash_in_ram(EFI_SIGNATURE_LIST *CertList,
UINTN dbsize, UINT8 *data,
int SignatureSize, EFI_GUID CertType)
{
EFI_SIGNATURE_DATA *Cert;
UINTN CertCount, Index;
BOOLEAN IsFound = FALSE;
while ((dbsize > 0) && (dbsize >= CertList->SignatureListSize)) {
CertCount = (CertList->SignatureListSize -sizeof (EFI_SIGNATURE_LIST) - CertList->SignatureHeaderSize) / CertList->SignatureSize;
Cert = (EFI_SIGNATURE_DATA *) ((UINT8 *) CertList + sizeof (EFI_SIGNATURE_LIST) + CertList->SignatureHeaderSize);
if (CompareGuid(&CertList->SignatureType, &CertType) == 0) {
for (Index = 0; Index < CertCount; Index++) {
if (CompareMem (Cert->SignatureData, data, SignatureSize) == 0) {
//
// Find the signature in database.
//
IsFound = TRUE;
break;
}
Cert = (EFI_SIGNATURE_DATA *) ((UINT8 *) Cert + CertList->SignatureSize);
}
if (IsFound) {
break;
}
}
dbsize -= CertList->SignatureListSize;
CertList = (EFI_SIGNATURE_LIST *) ((UINT8 *) CertList + CertList->SignatureListSize);
}
if (IsFound)
return DATA_FOUND;
return DATA_NOT_FOUND;
}
/*
* Check a hash against an EFI_SIGNATURE_LIST in a UEFI variable
*/
static CHECK_STATUS check_db_hash(CHAR16 *dbname, EFI_GUID guid, UINT8 *data,
int SignatureSize, EFI_GUID CertType)
{
EFI_STATUS efi_status;
EFI_SIGNATURE_LIST *CertList;
UINTN dbsize = 0;
UINT8 *db;
efi_status = get_variable(dbname, &db, &dbsize, guid);
if (efi_status != EFI_SUCCESS) {
return VAR_NOT_FOUND;
}
CertList = (EFI_SIGNATURE_LIST *)db;
CHECK_STATUS rc = check_db_hash_in_ram(CertList, dbsize, data,
SignatureSize, CertType);
FreePool(db);
return rc;
}
/*
* Check whether the binary signature or hash are present in dbx or the
* built-in blacklist
*/
static EFI_STATUS check_blacklist (WIN_CERTIFICATE_EFI_PKCS *cert,
UINT8 *sha256hash, UINT8 *sha1hash)
{
EFI_GUID secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
EFI_GUID shim_var = SHIM_LOCK_GUID;
EFI_SIGNATURE_LIST *dbx = (EFI_SIGNATURE_LIST *)vendor_dbx;
if (check_db_hash_in_ram(dbx, vendor_dbx_size, sha256hash,
SHA256_DIGEST_SIZE, EFI_CERT_SHA256_GUID) ==
DATA_FOUND)
return EFI_SECURITY_VIOLATION;
if (check_db_hash_in_ram(dbx, vendor_dbx_size, sha1hash,
SHA1_DIGEST_SIZE, EFI_CERT_SHA1_GUID) ==
DATA_FOUND)
return EFI_SECURITY_VIOLATION;
if (cert && check_db_cert_in_ram(dbx, vendor_dbx_size, cert,
sha256hash) == DATA_FOUND)
return EFI_SECURITY_VIOLATION;
if (check_db_hash(L"dbx", secure_var, sha256hash, SHA256_DIGEST_SIZE,
EFI_CERT_SHA256_GUID) == DATA_FOUND)
return EFI_SECURITY_VIOLATION;
if (check_db_hash(L"dbx", secure_var, sha1hash, SHA1_DIGEST_SIZE,
EFI_CERT_SHA1_GUID) == DATA_FOUND)
return EFI_SECURITY_VIOLATION;
if (cert && check_db_cert(L"dbx", secure_var, cert, sha256hash) ==
DATA_FOUND)
return EFI_SECURITY_VIOLATION;
if (check_db_hash(L"MokListX", shim_var, sha256hash, SHA256_DIGEST_SIZE,
EFI_CERT_SHA256_GUID) == DATA_FOUND) {
return EFI_SECURITY_VIOLATION;
}
if (cert && check_db_cert(L"MokListX", shim_var, cert, sha256hash) ==
DATA_FOUND) {
return EFI_SECURITY_VIOLATION;
}
return EFI_SUCCESS;
}
static void update_verification_method(verification_method_t method)
{
if (verification_method == VERIFIED_BY_NOTHING)
verification_method = method;
}
/*
* Check whether the binary signature or hash are present in db or MokList
*/
static EFI_STATUS check_whitelist (WIN_CERTIFICATE_EFI_PKCS *cert,
UINT8 *sha256hash, UINT8 *sha1hash)
{
EFI_GUID secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
EFI_GUID shim_var = SHIM_LOCK_GUID;
if (!ignore_db) {
if (check_db_hash(L"db", secure_var, sha256hash, SHA256_DIGEST_SIZE,
EFI_CERT_SHA256_GUID) == DATA_FOUND) {
update_verification_method(VERIFIED_BY_HASH);
return EFI_SUCCESS;
}
if (check_db_hash(L"db", secure_var, sha1hash, SHA1_DIGEST_SIZE,
EFI_CERT_SHA1_GUID) == DATA_FOUND) {
verification_method = VERIFIED_BY_HASH;
update_verification_method(VERIFIED_BY_HASH);
return EFI_SUCCESS;
}
if (cert && check_db_cert(L"db", secure_var, cert, sha256hash)
== DATA_FOUND) {
verification_method = VERIFIED_BY_CERT;
update_verification_method(VERIFIED_BY_CERT);
return EFI_SUCCESS;
}
}
if (check_db_hash(L"MokList", shim_var, sha256hash, SHA256_DIGEST_SIZE,
EFI_CERT_SHA256_GUID) == DATA_FOUND) {
verification_method = VERIFIED_BY_HASH;
update_verification_method(VERIFIED_BY_HASH);
return EFI_SUCCESS;
}
if (cert && check_db_cert(L"MokList", shim_var, cert, sha256hash) ==
DATA_FOUND) {
verification_method = VERIFIED_BY_CERT;
update_verification_method(VERIFIED_BY_CERT);
return EFI_SUCCESS;
}
update_verification_method(VERIFIED_BY_NOTHING);
return EFI_SECURITY_VIOLATION;
}
/*
* Check whether we're in Secure Boot and user mode
*/
static BOOLEAN secure_mode (void)
{
static int first = 1;
if (user_insecure_mode)
return FALSE;
if (variable_is_secureboot() != 1) {
if (verbose && !in_protocol && first)
console_notify(L"Secure boot not enabled");
first = 0;
return FALSE;
}
/* If we /do/ have "SecureBoot", but /don't/ have "SetupMode",
* then the implementation is bad, but we assume that secure boot is
* enabled according to the status of "SecureBoot". If we have both
* of them, then "SetupMode" may tell us additional data, and we need
* to consider it.
*/
if (variable_is_setupmode(0) == 1) {
if (verbose && !in_protocol && first)
console_notify(L"Platform is in setup mode");
first = 0;
return FALSE;
}
first = 0;
return TRUE;
}
#define check_size_line(data, datasize_in, hashbase, hashsize, l) ({ \
if ((unsigned long)hashbase > \
(unsigned long)data + datasize_in) { \
status = EFI_INVALID_PARAMETER; \
perror(L"shim.c:%d Invalid hash base 0x%016x\n", l, \
hashbase); \
goto done; \
} \
if ((unsigned long)hashbase + hashsize > \
(unsigned long)data + datasize_in) { \
status = EFI_INVALID_PARAMETER; \
perror(L"shim.c:%d Invalid hash size 0x%016x\n", l, \
hashsize); \
goto done; \
} \
})
#define check_size(d,ds,h,hs) check_size_line(d,ds,h,hs,__LINE__)
/*
* Calculate the SHA1 and SHA256 hashes of a binary
*/
static EFI_STATUS generate_hash (char *data, unsigned int datasize_in,
PE_COFF_LOADER_IMAGE_CONTEXT *context,
UINT8 *sha256hash, UINT8 *sha1hash)
{
unsigned int sha256ctxsize, sha1ctxsize;
unsigned int size = datasize_in;
void *sha256ctx = NULL, *sha1ctx = NULL;
char *hashbase;
unsigned int hashsize;
unsigned int SumOfBytesHashed, SumOfSectionBytes;
unsigned int index, pos;
unsigned int datasize;
EFI_IMAGE_SECTION_HEADER *Section;
EFI_IMAGE_SECTION_HEADER *SectionHeader = NULL;
EFI_STATUS status = EFI_SUCCESS;
EFI_IMAGE_DOS_HEADER *DosHdr = (void *)data;
unsigned int PEHdr_offset = 0;
if (datasize_in < 0) {
perror(L"Invalid data size\n");
return EFI_INVALID_PARAMETER;
}
size = datasize = (unsigned int)datasize_in;
if (datasize <= sizeof (*DosHdr) ||
DosHdr->e_magic != EFI_IMAGE_DOS_SIGNATURE) {
perror(L"Invalid signature\n");
return EFI_INVALID_PARAMETER;
}
PEHdr_offset = DosHdr->e_lfanew;
sha256ctxsize = Sha256GetContextSize();
sha256ctx = AllocatePool(sha256ctxsize);
sha1ctxsize = Sha1GetContextSize();
sha1ctx = AllocatePool(sha1ctxsize);
if (!sha256ctx || !sha1ctx) {
perror(L"Unable to allocate memory for hash context\n");
return EFI_OUT_OF_RESOURCES;
}
if (!Sha256Init(sha256ctx) || !Sha1Init(sha1ctx)) {
perror(L"Unable to initialise hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Hash start to checksum */
hashbase = data;
hashsize = (char *)&context->PEHdr->Pe32.OptionalHeader.CheckSum -
hashbase;
check_size(data, datasize_in, hashbase, hashsize);
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
perror(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;
check_size(data, datasize_in, hashbase, hashsize);
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
perror(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Hash end of certificate table to end of image header */
EFI_IMAGE_DATA_DIRECTORY *dd = context->SecDir + 1;
hashbase = (char *)dd;
hashsize = context->SizeOfHeaders - (unsigned long)((char *)dd - data);
if (hashsize > datasize_in) {
perror(L"Data Directory size %d is invalid\n", hashsize);
status = EFI_INVALID_PARAMETER;
goto done;
}
check_size(data, datasize_in, hashbase, hashsize);
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
perror(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Sort sections */
SumOfBytesHashed = context->SizeOfHeaders;
/* Validate section locations and sizes */
for (index = 0, SumOfSectionBytes = 0; index < context->PEHdr->Pe32.FileHeader.NumberOfSections; index++) {
EFI_IMAGE_SECTION_HEADER *SectionPtr;
/* Validate SectionPtr is within image */
SectionPtr = ImageAddress(data, datasize,
PEHdr_offset +
sizeof (UINT32) +
sizeof (EFI_IMAGE_FILE_HEADER) +
context->PEHdr->Pe32.FileHeader.SizeOfOptionalHeader +
(index * sizeof(*SectionPtr)));
if (!SectionPtr) {
perror(L"Malformed section %d\n", index);
status = EFI_INVALID_PARAMETER;
goto done;
}
/* Validate section size is within image. */
if (SectionPtr->SizeOfRawData >
datasize - SumOfBytesHashed - SumOfSectionBytes) {
perror(L"Malformed section %d size\n", index);
status = EFI_INVALID_PARAMETER;
goto done;
}
SumOfSectionBytes += SectionPtr->SizeOfRawData;
}
SectionHeader = (EFI_IMAGE_SECTION_HEADER *) AllocateZeroPool (sizeof (EFI_IMAGE_SECTION_HEADER) * context->PEHdr->Pe32.FileHeader.NumberOfSections);
if (SectionHeader == NULL) {
perror(L"Unable to allocate section header\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
/* Already validated above */
Section = ImageAddress(data, datasize,
PEHdr_offset +
sizeof (UINT32) +
sizeof (EFI_IMAGE_FILE_HEADER) +
context->PEHdr->Pe32.FileHeader.SizeOfOptionalHeader);
/* 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(data, size, Section->PointerToRawData);
if (!hashbase) {
perror(L"Malformed section header\n");
status = EFI_INVALID_PARAMETER;
goto done;
}
/* Verify hashsize within image. */
if (Section->SizeOfRawData >
datasize - Section->PointerToRawData) {
perror(L"Malformed section raw size %d\n", index);
status = EFI_INVALID_PARAMETER;
goto done;
}
hashsize = (unsigned int) Section->SizeOfRawData;
check_size(data, datasize_in, hashbase, hashsize);
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
perror(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
SumOfBytesHashed += Section->SizeOfRawData;
}
/* Hash all remaining data */
if (datasize > SumOfBytesHashed) {
hashbase = data + SumOfBytesHashed;
hashsize = datasize - context->SecDir->Size - SumOfBytesHashed;
if ((datasize - SumOfBytesHashed < context->SecDir->Size) ||
(SumOfBytesHashed + hashsize != context->SecDir->VirtualAddress)) {
perror(L"Malformed binary after Attribute Certificate Table\n");
status = EFI_INVALID_PARAMETER;
goto done;
}
check_size(data, datasize_in, hashbase, hashsize);
if (!(Sha256Update(sha256ctx, hashbase, hashsize)) ||
!(Sha1Update(sha1ctx, hashbase, hashsize))) {
perror(L"Unable to generate hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
}
if (!(Sha256Final(sha256ctx, sha256hash)) ||
!(Sha1Final(sha1ctx, sha1hash))) {
perror(L"Unable to finalise hash\n");
status = EFI_OUT_OF_RESOURCES;
goto done;
}
done:
if (SectionHeader)
FreePool(SectionHeader);
if (sha1ctx)
FreePool(sha1ctx);
if (sha256ctx)
FreePool(sha256ctx);
return status;
}
/*
* Ensure that the MOK database hasn't been set or modified from an OS
*/
static EFI_STATUS verify_mok (void) {
EFI_GUID shim_lock_guid = SHIM_LOCK_GUID;
EFI_STATUS status = EFI_SUCCESS;
UINT8 *MokListData = NULL;
UINTN MokListDataSize = 0;
UINT32 attributes;
status = get_variable_attr(L"MokList", &MokListData, &MokListDataSize,
shim_lock_guid, &attributes);
if (!EFI_ERROR(status) && attributes & EFI_VARIABLE_RUNTIME_ACCESS) {
perror(L"MokList is compromised!\nErase all keys in MokList!\n");
if (LibDeleteVariable(L"MokList", &shim_lock_guid) != EFI_SUCCESS) {
perror(L"Failed to erase MokList\n");
return EFI_SECURITY_VIOLATION;
}
}
if (MokListData)
FreePool(MokListData);
return EFI_SUCCESS;
}
/*
* Check that the signature is valid and matches the binary
*/
static EFI_STATUS verify_buffer (char *data, int datasize,
PE_COFF_LOADER_IMAGE_CONTEXT *context)
{
UINT8 sha256hash[SHA256_DIGEST_SIZE];
UINT8 sha1hash[SHA1_DIGEST_SIZE];
EFI_STATUS status = EFI_SECURITY_VIOLATION;
WIN_CERTIFICATE_EFI_PKCS *cert = NULL;
unsigned int size = datasize;
if (context->SecDir->Size != 0) {
if (context->SecDir->Size >= size) {
perror(L"Certificate Database size is too large\n");
return EFI_INVALID_PARAMETER;
}
cert = ImageAddress (data, size,
context->SecDir->VirtualAddress);
if (!cert) {
perror(L"Certificate located outside the image\n");
return EFI_INVALID_PARAMETER;
}
if (cert->Hdr.dwLength > context->SecDir->Size) {
perror(L"Certificate list size is inconsistent with PE headers");
return EFI_INVALID_PARAMETER;
}
if (cert->Hdr.wCertificateType !=
WIN_CERT_TYPE_PKCS_SIGNED_DATA) {
perror(L"Unsupported certificate type %x\n",
cert->Hdr.wCertificateType);
return EFI_UNSUPPORTED;
}
}
status = generate_hash(data, datasize, context, sha256hash, sha1hash);
if (status != EFI_SUCCESS)
return status;
/*
* Check that the MOK database hasn't been modified
*/
status = verify_mok();
if (status != EFI_SUCCESS)
return status;