/
shim.c
2006 lines (1748 loc) · 51.7 KB
/
shim.c
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// SPDX-License-Identifier: BSD-2-Clause-Patent
/*
* shim - trivial UEFI first-stage bootloader
*
* Copyright Red Hat, Inc
* Author: Matthew Garrett
*
* Significant portions of this code are derived from Tianocore
* (http://tianocore.sf.net) and are Copyright 2009-2012 Intel
* Corporation.
*/
#include "shim.h"
#if defined(ENABLE_SHIM_CERT)
#include "shim_cert.h"
#endif /* defined(ENABLE_SHIM_CERT) */
#include <openssl/err.h>
#include <openssl/bn.h>
#include <openssl/dh.h>
#include <openssl/ocsp.h>
#include <openssl/pkcs12.h>
#include <openssl/rand.h>
#include <openssl/crypto.h>
#include <openssl/ssl.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#include <openssl/rsa.h>
#include <openssl/dso.h>
#include <Library/BaseCryptLib.h>
#include <stdint.h>
#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_LOADED_IMAGE *shim_li;
static EFI_LOADED_IMAGE shim_li_bak;
list_t sbat_var;
/*
* The vendor certificate used for validating the second stage loader
*/
extern struct {
UINT32 vendor_authorized_size;
UINT32 vendor_deauthorized_size;
UINT32 vendor_authorized_offset;
UINT32 vendor_deauthorized_offset;
} cert_table;
#define EFI_IMAGE_SECURITY_DATABASE_GUID { 0xd719b2cb, 0x3d3a, 0x4596, { 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f }}
typedef enum {
DATA_FOUND,
DATA_NOT_FOUND,
VAR_NOT_FOUND
} CHECK_STATUS;
typedef struct {
UINT32 MokSize;
UINT8 *Mok;
} MokListNode;
static void
drain_openssl_errors(void)
{
unsigned long err = -1;
while (err != 0)
err = ERR_get_error();
}
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) {
dprint(L"cert[0:1] is [%02x%02x], should be [%02x%02x]\n",
Cert[0], Cert[1], 0x30, 0x82);
return FALSE;
}
length = Cert[2]<<8 | Cert[3];
if (length != (CertSize - 4)) {
dprint(L"Cert length is %ld, expecting %ld\n",
length, CertSize);
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,
"modsign-eku",
"modsign-eku"));
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);
}
OBJ_cleanup();
return TRUE;
}
static CHECK_STATUS check_db_cert_in_ram(EFI_SIGNATURE_LIST *CertList,
UINTN dbsize,
WIN_CERTIFICATE_EFI_PKCS *data,
UINT8 *hash, CHAR16 *dbname,
EFI_GUID guid)
{
EFI_SIGNATURE_DATA *Cert;
UINTN CertSize;
BOOLEAN IsFound = FALSE;
int i = 0;
while ((dbsize > 0) && (dbsize >= CertList->SignatureListSize)) {
if (CompareGuid (&CertList->SignatureType, &EFI_CERT_TYPE_X509_GUID) == 0) {
Cert = (EFI_SIGNATURE_DATA *) ((UINT8 *) CertList + sizeof (EFI_SIGNATURE_LIST) + CertList->SignatureHeaderSize);
CertSize = CertList->SignatureSize - sizeof(EFI_GUID);
dprint(L"trying to verify cert %d (%s)\n", i++, dbname);
if (verify_x509(Cert->SignatureData, CertSize)) {
if (verify_eku(Cert->SignatureData, CertSize)) {
drain_openssl_errors();
IsFound = AuthenticodeVerify (data->CertData,
data->Hdr.dwLength - sizeof(data->Hdr),
Cert->SignatureData,
CertSize,
hash, SHA256_DIGEST_SIZE);
if (IsFound) {
dprint(L"AuthenticodeVerify() succeeded: %d\n", IsFound);
tpm_measure_variable(dbname, guid, CertList->SignatureSize, Cert);
drain_openssl_errors();
return DATA_FOUND;
} else {
LogError(L"AuthenticodeVerify(): %d\n", IsFound);
}
}
} else if (verbose) {
console_print(L"Not a DER encoded x.509 Certificate");
dprint(L"cert:\n");
dhexdumpat(Cert->SignatureData, CertSize, 0);
}
}
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_ERROR(efi_status))
return VAR_NOT_FOUND;
CertList = (EFI_SIGNATURE_LIST *)db;
rc = check_db_cert_in_ram(CertList, dbsize, data, hash, dbname, guid);
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,
CHAR16 *dbname, EFI_GUID guid)
{
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;
tpm_measure_variable(dbname, guid, CertList->SignatureSize, Cert);
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_ERROR(efi_status)) {
return VAR_NOT_FOUND;
}
CertList = (EFI_SIGNATURE_LIST *)db;
CHECK_STATUS rc = check_db_hash_in_ram(CertList, dbsize, data,
SignatureSize, CertType,
dbname, guid);
FreePool(db);
return rc;
}
/*
* Check whether the binary signature or hash are present in dbx or the
* built-in denylist
*/
static EFI_STATUS check_denylist (WIN_CERTIFICATE_EFI_PKCS *cert,
UINT8 *sha256hash, UINT8 *sha1hash)
{
EFI_SIGNATURE_LIST *dbx = (EFI_SIGNATURE_LIST *)vendor_deauthorized;
if (check_db_hash_in_ram(dbx, vendor_deauthorized_size, sha256hash,
SHA256_DIGEST_SIZE, EFI_CERT_SHA256_GUID, L"dbx",
EFI_SECURE_BOOT_DB_GUID) == DATA_FOUND) {
LogError(L"binary sha256hash found in vendor dbx\n");
return EFI_SECURITY_VIOLATION;
}
if (check_db_hash_in_ram(dbx, vendor_deauthorized_size, sha1hash,
SHA1_DIGEST_SIZE, EFI_CERT_SHA1_GUID, L"dbx",
EFI_SECURE_BOOT_DB_GUID) == DATA_FOUND) {
LogError(L"binary sha1hash found in vendor dbx\n");
return EFI_SECURITY_VIOLATION;
}
if (cert &&
check_db_cert_in_ram(dbx, vendor_deauthorized_size, cert, sha256hash, L"dbx",
EFI_SECURE_BOOT_DB_GUID) == DATA_FOUND) {
LogError(L"cert sha256hash found in vendor dbx\n");
return EFI_SECURITY_VIOLATION;
}
if (check_db_hash(L"dbx", EFI_SECURE_BOOT_DB_GUID, sha256hash,
SHA256_DIGEST_SIZE, EFI_CERT_SHA256_GUID) == DATA_FOUND) {
LogError(L"binary sha256hash found in system dbx\n");
return EFI_SECURITY_VIOLATION;
}
if (check_db_hash(L"dbx", EFI_SECURE_BOOT_DB_GUID, sha1hash,
SHA1_DIGEST_SIZE, EFI_CERT_SHA1_GUID) == DATA_FOUND) {
LogError(L"binary sha1hash found in system dbx\n");
return EFI_SECURITY_VIOLATION;
}
if (cert &&
check_db_cert(L"dbx", EFI_SECURE_BOOT_DB_GUID,
cert, sha256hash) == DATA_FOUND) {
LogError(L"cert sha256hash found in system dbx\n");
return EFI_SECURITY_VIOLATION;
}
if (check_db_hash(L"MokListX", SHIM_LOCK_GUID, sha256hash,
SHA256_DIGEST_SIZE, EFI_CERT_SHA256_GUID) == DATA_FOUND) {
LogError(L"binary sha256hash found in Mok dbx\n");
return EFI_SECURITY_VIOLATION;
}
if (cert &&
check_db_cert(L"MokListX", SHIM_LOCK_GUID,
cert, sha256hash) == DATA_FOUND) {
LogError(L"cert sha256hash found in Mok dbx\n");
return EFI_SECURITY_VIOLATION;
}
drain_openssl_errors();
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_allowlist (WIN_CERTIFICATE_EFI_PKCS *cert,
UINT8 *sha256hash, UINT8 *sha1hash)
{
if (!ignore_db) {
if (check_db_hash(L"db", EFI_SECURE_BOOT_DB_GUID, sha256hash, SHA256_DIGEST_SIZE,
EFI_CERT_SHA256_GUID) == DATA_FOUND) {
update_verification_method(VERIFIED_BY_HASH);
return EFI_SUCCESS;
} else {
LogError(L"check_db_hash(db, sha256hash) != DATA_FOUND\n");
}
if (check_db_hash(L"db", EFI_SECURE_BOOT_DB_GUID, sha1hash, SHA1_DIGEST_SIZE,
EFI_CERT_SHA1_GUID) == DATA_FOUND) {
verification_method = VERIFIED_BY_HASH;
update_verification_method(VERIFIED_BY_HASH);
return EFI_SUCCESS;
} else {
LogError(L"check_db_hash(db, sha1hash) != DATA_FOUND\n");
}
if (cert && check_db_cert(L"db", EFI_SECURE_BOOT_DB_GUID, cert, sha256hash)
== DATA_FOUND) {
verification_method = VERIFIED_BY_CERT;
update_verification_method(VERIFIED_BY_CERT);
return EFI_SUCCESS;
} else if (cert) {
LogError(L"check_db_cert(db, sha256hash) != DATA_FOUND\n");
}
}
#if defined(VENDOR_DB_FILE)
EFI_SIGNATURE_LIST *db = (EFI_SIGNATURE_LIST *)vendor_db;
if (check_db_hash_in_ram(db, vendor_db_size,
sha256hash, SHA256_DIGEST_SIZE,
EFI_CERT_SHA256_GUID, L"vendor_db",
EFI_SECURE_BOOT_DB_GUID) == DATA_FOUND) {
verification_method = VERIFIED_BY_HASH;
update_verification_method(VERIFIED_BY_HASH);
return EFI_SUCCESS;
} else {
LogError(L"check_db_hash(vendor_db, sha256hash) != DATA_FOUND\n");
}
if (cert &&
check_db_cert_in_ram(db, vendor_db_size,
cert, sha256hash, L"vendor_db",
EFI_SECURE_BOOT_DB_GUID) == DATA_FOUND) {
verification_method = VERIFIED_BY_CERT;
update_verification_method(VERIFIED_BY_CERT);
return EFI_SUCCESS;
} else if (cert) {
LogError(L"check_db_cert(vendor_db, sha256hash) != DATA_FOUND\n");
}
#endif
if (check_db_hash(L"MokListRT", SHIM_LOCK_GUID, sha256hash,
SHA256_DIGEST_SIZE, EFI_CERT_SHA256_GUID)
== DATA_FOUND) {
verification_method = VERIFIED_BY_HASH;
update_verification_method(VERIFIED_BY_HASH);
return EFI_SUCCESS;
} else {
LogError(L"check_db_hash(MokListRT, sha256hash) != DATA_FOUND\n");
}
if (cert && check_db_cert(L"MokListRT", SHIM_LOCK_GUID, cert, sha256hash)
== DATA_FOUND) {
verification_method = VERIFIED_BY_CERT;
update_verification_method(VERIFIED_BY_CERT);
return EFI_SUCCESS;
} else if (cert) {
LogError(L"check_db_cert(MokListRT, sha256hash) != DATA_FOUND\n");
}
update_verification_method(VERIFIED_BY_NOTHING);
return EFI_NOT_FOUND;
}
/*
* Check whether we're in Secure Boot and user mode
*/
BOOLEAN secure_mode (void)
{
static int first = 1;
if (user_insecure_mode)
return FALSE;
if (variable_is_secureboot() != 1) {
if (verbose && !in_protocol && first) {
CHAR16 *title = L"Secure boot not enabled";
CHAR16 *message = L"Press any key to continue";
console_countdown(title, message, 5);
}
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) {
CHAR16 *title = L"Platform is in setup mode";
CHAR16 *message = L"Press any key to continue";
console_countdown(title, message, 5);
}
first = 0;
return FALSE;
}
first = 0;
return TRUE;
}
static EFI_STATUS
verify_one_signature(WIN_CERTIFICATE_EFI_PKCS *sig,
UINT8 *sha256hash, UINT8 *sha1hash)
{
EFI_STATUS efi_status;
/*
* Ensure that the binary isn't forbidden
*/
drain_openssl_errors();
efi_status = check_denylist(sig, sha256hash, sha1hash);
if (EFI_ERROR(efi_status)) {
perror(L"Binary is forbidden: %r\n", efi_status);
PrintErrors();
ClearErrors();
crypterr(efi_status);
return efi_status;
}
/*
* Check whether the binary is authorized in any of the firmware
* databases
*/
drain_openssl_errors();
efi_status = check_allowlist(sig, sha256hash, sha1hash);
if (EFI_ERROR(efi_status)) {
if (efi_status != EFI_NOT_FOUND) {
dprint(L"check_allowlist(): %r\n", efi_status);
PrintErrors();
ClearErrors();
crypterr(efi_status);
}
} else {
drain_openssl_errors();
return efi_status;
}
efi_status = EFI_NOT_FOUND;
#if defined(ENABLE_SHIM_CERT)
/*
* Check against the shim build key
*/
drain_openssl_errors();
if (build_cert && build_cert_size) {
dprint("verifying against shim cert\n");
}
if (build_cert && build_cert_size &&
AuthenticodeVerify(sig->CertData,
sig->Hdr.dwLength - sizeof(sig->Hdr),
build_cert, build_cert_size, sha256hash,
SHA256_DIGEST_SIZE)) {
dprint(L"AuthenticodeVerify(shim_cert) succeeded\n");
update_verification_method(VERIFIED_BY_CERT);
tpm_measure_variable(L"Shim", SHIM_LOCK_GUID,
build_cert_size, build_cert);
efi_status = EFI_SUCCESS;
drain_openssl_errors();
return efi_status;
} else {
dprint(L"AuthenticodeVerify(shim_cert) failed\n");
PrintErrors();
ClearErrors();
crypterr(EFI_NOT_FOUND);
}
#endif /* defined(ENABLE_SHIM_CERT) */
#if defined(VENDOR_CERT_FILE)
/*
* And finally, check against shim's built-in key
*/
drain_openssl_errors();
if (vendor_cert_size) {
dprint("verifying against vendor_cert\n");
}
if (vendor_cert_size &&
AuthenticodeVerify(sig->CertData,
sig->Hdr.dwLength - sizeof(sig->Hdr),
vendor_cert, vendor_cert_size,
sha256hash, SHA256_DIGEST_SIZE)) {
dprint(L"AuthenticodeVerify(vendor_cert) succeeded\n");
update_verification_method(VERIFIED_BY_CERT);
tpm_measure_variable(L"Shim", SHIM_LOCK_GUID,
vendor_cert_size, vendor_cert);
efi_status = EFI_SUCCESS;
drain_openssl_errors();
return efi_status;
} else {
dprint(L"AuthenticodeVerify(vendor_cert) failed\n");
PrintErrors();
ClearErrors();
crypterr(EFI_NOT_FOUND);
}
#endif /* defined(VENDOR_CERT_FILE) */
return efi_status;
}
/*
* Check that the signature is valid and matches the binary
*/
EFI_STATUS
verify_buffer_authenticode (char *data, int datasize,
PE_COFF_LOADER_IMAGE_CONTEXT *context,
UINT8 *sha256hash, UINT8 *sha1hash)
{
EFI_STATUS ret_efi_status;
size_t size = datasize;
size_t offset = 0;
unsigned int i = 0;
if (datasize < 0)
return EFI_INVALID_PARAMETER;
/*
* Clear OpenSSL's error log, because we get some DSO unimplemented
* errors during its intialization, and we don't want those to look
* like they're the reason for validation failures.
*/
drain_openssl_errors();
ret_efi_status = generate_hash(data, datasize, context, sha256hash, sha1hash);
if (EFI_ERROR(ret_efi_status)) {
dprint(L"generate_hash: %r\n", ret_efi_status);
PrintErrors();
ClearErrors();
crypterr(ret_efi_status);
return ret_efi_status;
}
/*
* Ensure that the binary isn't forbidden by hash
*/
drain_openssl_errors();
ret_efi_status = check_denylist(NULL, sha256hash, sha1hash);
if (EFI_ERROR(ret_efi_status)) {
// perror(L"Binary is forbidden\n");
// dprint(L"Binary is forbidden: %r\n", ret_efi_status);
PrintErrors();
ClearErrors();
crypterr(ret_efi_status);
return ret_efi_status;
}
/*
* Check whether the binary is authorized by hash in any of the
* firmware databases
*/
drain_openssl_errors();
ret_efi_status = check_allowlist(NULL, sha256hash, sha1hash);
if (EFI_ERROR(ret_efi_status)) {
LogError(L"check_allowlist(): %r\n", ret_efi_status);
dprint(L"check_allowlist: %r\n", ret_efi_status);
if (ret_efi_status != EFI_NOT_FOUND) {
dprint(L"check_allowlist(): %r\n", ret_efi_status);
PrintErrors();
ClearErrors();
crypterr(ret_efi_status);
return ret_efi_status;
}
} else {
drain_openssl_errors();
return ret_efi_status;
}
if (context->SecDir->Size == 0) {
dprint(L"No signatures found\n");
return EFI_SECURITY_VIOLATION;
}
if (checked_add(context->SecDir->Size, context->SecDir->VirtualAddress, &offset) ||
offset > size) {
perror(L"Certificate Database size is too large\n");
return EFI_INVALID_PARAMETER;
}
offset = 0;
ret_efi_status = EFI_NOT_FOUND;
do {
WIN_CERTIFICATE_EFI_PKCS *sig = NULL;
size_t sz;
sig = ImageAddress(data, size,
context->SecDir->VirtualAddress + offset);
if (!sig)
break;
if ((uint64_t)(uintptr_t)&sig[1]
> (uint64_t)(uintptr_t)data + datasize) {
perror(L"Certificate size is too large for secruity database");
return EFI_INVALID_PARAMETER;
}
sz = offset + offsetof(WIN_CERTIFICATE_EFI_PKCS, Hdr.dwLength)
+ sizeof(sig->Hdr.dwLength);
if (sz > context->SecDir->Size) {
perror(L"Certificate size is too large for secruity database");
return EFI_INVALID_PARAMETER;
}
sz = sig->Hdr.dwLength;
if (sz > context->SecDir->Size - offset) {
perror(L"Certificate size is too large for secruity database");
return EFI_INVALID_PARAMETER;
}
if (sz < sizeof(sig->Hdr)) {
perror(L"Certificate size is too small for certificate data");
return EFI_INVALID_PARAMETER;
}
if (sig->Hdr.wCertificateType == WIN_CERT_TYPE_PKCS_SIGNED_DATA) {
EFI_STATUS efi_status;
dprint(L"Attempting to verify signature %d:\n", i++);
efi_status = verify_one_signature(sig, sha256hash, sha1hash);
/*
* If we didn't get EFI_SECURITY_VIOLATION from
* checking the hashes above, then any dbx entries are
* for a certificate, not this individual binary.
*
* So don't clobber successes with security violation
* here; that just means it isn't a success.
*/
if (ret_efi_status != EFI_SUCCESS)
ret_efi_status = efi_status;
} else {
perror(L"Unsupported certificate type %x\n",
sig->Hdr.wCertificateType);
}
offset = ALIGN_VALUE(offset + sz, 8);
} while (offset < context->SecDir->Size);
if (ret_efi_status != EFI_SUCCESS) {
dprint(L"Binary is not authorized\n");
PrintErrors();
ClearErrors();
crypterr(EFI_SECURITY_VIOLATION);
ret_efi_status = EFI_SECURITY_VIOLATION;
}
drain_openssl_errors();
return ret_efi_status;
}
/*
* Check that the binary is permitted to load by SBAT.
*/
EFI_STATUS
verify_buffer_sbat (char *data, int datasize,
PE_COFF_LOADER_IMAGE_CONTEXT *context)
{
int i;
EFI_IMAGE_SECTION_HEADER *Section;
char *SBATBase = NULL;
size_t SBATSize = 0;
Section = context->FirstSection;
for (i = 0; i < context->NumberOfSections; i++, Section++) {
if ((uint64_t)(uintptr_t)&Section[1]
> (uintptr_t)(uintptr_t)data + datasize) {
perror(L"Section exceeds bounds of image\n");
return EFI_UNSUPPORTED;
}
if (CompareMem(Section->Name, ".sbat\0\0\0", 8) != 0)
continue;
if (SBATBase || SBATSize) {
perror(L"Image has multiple SBAT sections\n");
return EFI_UNSUPPORTED;
}
if (Section->NumberOfRelocations != 0 ||
Section->PointerToRelocations != 0) {
perror(L"SBAT section has relocations\n");
return EFI_UNSUPPORTED;
}
/* The virtual size corresponds to the size of the SBAT
* metadata and isn't necessarily a multiple of the file
* alignment. The on-disk size is a multiple of the file
* alignment and is zero padded. Make sure that the
* on-disk size is at least as large as virtual size,
* and ignore the section if it isn't. */
if (Section->SizeOfRawData &&
Section->SizeOfRawData >= Section->Misc.VirtualSize) {
uint64_t boundary;
SBATBase = ImageAddress(data, datasize,
Section->PointerToRawData);
SBATSize = Section->SizeOfRawData;
dprint(L"sbat section base:0x%lx size:0x%lx\n",
SBATBase, SBATSize);
if (checked_add((uint64_t)(uintptr_t)SBATBase, SBATSize, &boundary) ||
(boundary > (uint64_t)(uintptr_t)data + datasize)) {
perror(L"Section exceeds bounds of image\n");
return EFI_UNSUPPORTED;
}
}
}
return verify_sbat_section(SBATBase, SBATSize);
}
/*
* Check that the signature is valid and matches the binary and that
* the binary is permitted to load by SBAT.
*/
EFI_STATUS
verify_buffer (char *data, int datasize,
PE_COFF_LOADER_IMAGE_CONTEXT *context,
UINT8 *sha256hash, UINT8 *sha1hash)
{
EFI_STATUS efi_status;
efi_status = verify_buffer_authenticode(data, datasize, context, sha256hash, sha1hash);
if (EFI_ERROR(efi_status))
return efi_status;
return verify_buffer_sbat(data, datasize, context);
}
static int
is_removable_media_path(EFI_LOADED_IMAGE *li)
{
unsigned int pathlen = 0;
CHAR16 *bootpath = NULL;
int ret = 0;
bootpath = DevicePathToStr(li->FilePath);
/* Check the beginning of the string and the end, to avoid
* caring about which arch this is. */
/* I really don't know why, but sometimes bootpath gives us
* L"\\EFI\\BOOT\\/BOOTX64.EFI". So just handle that here...
*/
if (StrnCaseCmp(bootpath, L"\\EFI\\BOOT\\BOOT", 14) &&
StrnCaseCmp(bootpath, L"\\EFI\\BOOT\\/BOOT", 15) &&
StrnCaseCmp(bootpath, L"EFI\\BOOT\\BOOT", 13) &&
StrnCaseCmp(bootpath, L"EFI\\BOOT\\/BOOT", 14))
goto error;
pathlen = StrLen(bootpath);
if (pathlen < 5 || StrCaseCmp(bootpath + pathlen - 4, L".EFI"))
goto error;
ret = 1;
error:
if (bootpath)
FreePool(bootpath);
return ret;
}
static int
should_use_fallback(EFI_HANDLE image_handle)
{
EFI_LOADED_IMAGE *li;
EFI_FILE_IO_INTERFACE *fio = NULL;
EFI_FILE *vh = NULL;
EFI_FILE *fh = NULL;
EFI_STATUS efi_status;
int ret = 0;
efi_status = BS->HandleProtocol(image_handle, &EFI_LOADED_IMAGE_GUID,
(void **)&li);
if (EFI_ERROR(efi_status)) {
perror(L"Could not get image for boot" EFI_ARCH L".efi: %r\n",
efi_status);
return 0;
}
if (!is_removable_media_path(li))
goto error;
efi_status = BS->HandleProtocol(li->DeviceHandle, &FileSystemProtocol,
(void **) &fio);
if (EFI_ERROR(efi_status)) {
perror(L"Could not get fio for li->DeviceHandle: %r\n",
efi_status);
goto error;
}
efi_status = fio->OpenVolume(fio, &vh);
if (EFI_ERROR(efi_status)) {
perror(L"Could not open fio volume: %r\n", efi_status);
goto error;
}
efi_status = vh->Open(vh, &fh, L"\\EFI\\BOOT" FALLBACK,
EFI_FILE_MODE_READ, 0);
if (EFI_ERROR(efi_status)) {
/* Do not print the error here - this is an acceptable case
* for removable media, where we genuinely don't want
* fallback.efi to exist.
* Print(L"Could not open \"\\EFI\\BOOT%s\": %r\n", FALLBACK,
* efi_status);
*/
goto error;
}
ret = 1;
error:
if (fh)
fh->Close(fh);
if (vh)
vh->Close(vh);
return ret;
}
/*
* Open the second stage bootloader and read it into a buffer
*/
static EFI_STATUS load_image (EFI_LOADED_IMAGE *li, void **data,
int *datasize, CHAR16 *PathName)
{
EFI_STATUS efi_status;
EFI_HANDLE device;
EFI_FILE_INFO *fileinfo = NULL;
EFI_FILE_IO_INTERFACE *drive;
EFI_FILE *root, *grub;
UINTN buffersize = sizeof(EFI_FILE_INFO);
device = li->DeviceHandle;
dprint(L"attempting to load %s\n", PathName);
/*
* Open the device
*/
efi_status = BS->HandleProtocol(device, &EFI_SIMPLE_FILE_SYSTEM_GUID,
(void **) &drive);
if (EFI_ERROR(efi_status)) {
perror(L"Failed to find fs: %r\n", efi_status);
goto error;
}
efi_status = drive->OpenVolume(drive, &root);
if (EFI_ERROR(efi_status)) {
perror(L"Failed to open fs: %r\n", efi_status);
goto error;
}
/*
* And then open the file
*/
efi_status = root->Open(root, &grub, PathName, EFI_FILE_MODE_READ, 0);
if (EFI_ERROR(efi_status)) {
perror(L"Failed to open %s - %r\n", PathName, efi_status);
goto error;
}
fileinfo = AllocatePool(buffersize);
if (!fileinfo) {
perror(L"Unable to allocate file info buffer\n");
efi_status = EFI_OUT_OF_RESOURCES;
goto error;
}
/*
* Find out how big the file is in order to allocate the storage
* buffer
*/
efi_status = grub->GetInfo(grub, &EFI_FILE_INFO_GUID, &buffersize,
fileinfo);
if (efi_status == EFI_BUFFER_TOO_SMALL) {
FreePool(fileinfo);
fileinfo = AllocatePool(buffersize);
if (!fileinfo) {
perror(L"Unable to allocate file info buffer\n");
efi_status = EFI_OUT_OF_RESOURCES;
goto error;
}
efi_status = grub->GetInfo(grub, &EFI_FILE_INFO_GUID,
&buffersize, fileinfo);
}
if (EFI_ERROR(efi_status)) {
perror(L"Unable to get file info: %r\n", efi_status);
goto error;
}
buffersize = fileinfo->FileSize;
*data = AllocatePool(buffersize);
if (!*data) {
perror(L"Unable to allocate file buffer\n");
efi_status = EFI_OUT_OF_RESOURCES;
goto error;
}
/*
* Perform the actual read
*/
efi_status = grub->Read(grub, &buffersize, *data);
if (efi_status == EFI_BUFFER_TOO_SMALL) {
FreePool(*data);
*data = AllocatePool(buffersize);
efi_status = grub->Read(grub, &buffersize, *data);
}
if (EFI_ERROR(efi_status)) {
perror(L"Unexpected return from initial read: %r, buffersize %x\n",
efi_status, buffersize);
goto error;
}
*datasize = buffersize;
FreePool(fileinfo);
return EFI_SUCCESS;
error:
if (*data) {
FreePool(*data);
*data = NULL;
}
if (fileinfo)
FreePool(fileinfo);
return efi_status;
}
/*
* Protocol entry point. If secure boot is enabled, verify that the provided
* buffer is signed with a trusted key.
*/
EFI_STATUS shim_verify (void *buffer, UINT32 size)
{
EFI_STATUS efi_status = EFI_SUCCESS;
PE_COFF_LOADER_IMAGE_CONTEXT context;
UINT8 sha1hash[SHA1_DIGEST_SIZE];
UINT8 sha256hash[SHA256_DIGEST_SIZE];
if ((INT32)size < 0)
return EFI_INVALID_PARAMETER;
loader_is_participating = 1;
in_protocol = 1;
efi_status = read_header(buffer, size, &context);