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efi-boot-shim/shim.c
Chris Coulson 25c8324637 Rename check_{white,black}list to check_{allow,deny}list 
v2 - updated for conflicts and to include documentation (pjones)
2021-02-16 09:12:48 +01:00

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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"
#include "hexdump.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 CHAR16 *second_stage;
void *load_options;
UINT32 load_options_size;
/*
* 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;
UINT32 vendor_authorized_size = 0;
UINT8 *vendor_authorized = NULL;
UINT32 vendor_deauthorized_size = 0;
UINT8 *vendor_deauthorized = NULL;
#if defined(ENABLE_SHIM_CERT)
UINT32 build_cert_size;
UINT8 *build_cert;
#endif /* defined(ENABLE_SHIM_CERT) */
/*
* 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;
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, CertSize, Cert->SignatureData);
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, SignatureSize, data);
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"MokList", 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(MokList, sha256hash) != DATA_FOUND\n");
}
if (cert && check_db_cert(L"MokList", 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(MokList, 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)
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;
}
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 (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 (context->SecDir->Size >= size) {
perror(L"Certificate Database size is too large\n");
return EFI_INVALID_PARAMETER;
}
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;
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;
}
static int
should_use_fallback(EFI_HANDLE image_handle)
{
EFI_LOADED_IMAGE *li;
unsigned int pathlen = 0;
CHAR16 *bootpath = NULL;
EFI_FILE_IO_INTERFACE *fio = NULL;
EFI_FILE *vh = NULL;
EFI_FILE *fh = NULL;
EFI_STATUS efi_status;
int ret = 0;
efi_status = gBS->HandleProtocol(image_handle, &EFI_LOADED_IMAGE_GUID,
(void **)&li);
if (EFI_ERROR(efi_status)) {
perror(L"Could not get image for bootx64.efi: %r\n",
efi_status);
return 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;
efi_status = gBS->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);
if (bootpath)
FreePool(bootpath);
return ret;
}
/*
* Generate the path of an executable given shim's path and the name
* of the executable
*/
static EFI_STATUS generate_path_from_image_path(EFI_LOADED_IMAGE *li,
CHAR16 *ImagePath,
CHAR16 **PathName)
{
EFI_DEVICE_PATH *devpath;
unsigned int i;
int j, last = -1;
unsigned int pathlen = 0;
EFI_STATUS efi_status = EFI_SUCCESS;
CHAR16 *bootpath;
/*
* Suuuuper lazy technique here, but check and see if this is a full
* path to something on the ESP. Backwards compatibility demands
* that we don't just use \\, because we (not particularly brightly)
* used to require that the relative file path started with that.
*
* If it is a full path, don't try to merge it with the directory
* from our Loaded Image handle.
*/
if (StrSize(ImagePath) > 5 && StrnCmp(ImagePath, L"\\EFI\\", 5) == 0) {
*PathName = StrDuplicate(ImagePath);
if (!*PathName) {
perror(L"Failed to allocate path buffer\n");
return EFI_OUT_OF_RESOURCES;
}
return EFI_SUCCESS;
}
devpath = li->FilePath;
bootpath = DevicePathToStr(devpath);
pathlen = StrLen(bootpath);
/*
* DevicePathToStr() concatenates two nodes with '/'.
* Convert '/' to '\\'.
*/
for (i = 0; i < pathlen; i++) {
if (bootpath[i] == '/')
bootpath[i] = '\\';
}
for (i=pathlen; i>0; i--) {
if (bootpath[i] == '\\' && bootpath[i-1] == '\\')
bootpath[i] = '/';
else if (last == -1 && bootpath[i] == '\\')
last = i;
}
if (last == -1 && bootpath[0] == '\\')
last = 0;
bootpath[last+1] = '\0';
if (last > 0) {
for (i = 0, j = 0; bootpath[i] != '\0'; i++) {
if (bootpath[i] != '/') {
bootpath[j] = bootpath[i];
j++;
}
}
bootpath[j] = '\0';
}
for (i = 0, last = 0; i < StrLen(ImagePath); i++)
if (ImagePath[i] == '\\')
last = i + 1;
ImagePath = ImagePath + last;
*PathName = AllocatePool(StrSize(bootpath) + StrSize(ImagePath));
if (!*PathName) {
perror(L"Failed to allocate path buffer\n");
efi_status = EFI_OUT_OF_RESOURCES;
goto error;
}
*PathName[0] = '\0';
if (StrnCaseCmp(bootpath, ImagePath, StrLen(bootpath)))
StrCat(*PathName, bootpath);
StrCat(*PathName, ImagePath);
error:
FreePool(bootpath);
return efi_status;
}
/*
* 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 = gBS->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);
if (EFI_ERROR(efi_status))
goto done;
efi_status = generate_hash(buffer, size, &context,
sha256hash, sha1hash);
if (EFI_ERROR(efi_status))
goto done;
/* Measure the binary into the TPM */
#ifdef REQUIRE_TPM
efi_status =
#endif
tpm_log_pe((EFI_PHYSICAL_ADDRESS)(UINTN)buffer, size, 0, NULL,
sha1hash, 4);
#ifdef REQUIRE_TPM
if (EFI_ERROR(efi_status))
goto done;
#endif
if (!secure_mode()) {
efi_status = EFI_SUCCESS;
goto done;
}
efi_status = verify_buffer(buffer, size,
&context, sha256hash, sha1hash);
done:
in_protocol = 0;
return efi_status;
}
static EFI_STATUS shim_hash (char *data, int datasize,
PE_COFF_LOADER_IMAGE_CONTEXT *context,
UINT8 *sha256hash, UINT8 *sha1hash)
{
EFI_STATUS efi_status;
if (datasize < 0)
return EFI_INVALID_PARAMETER;
in_protocol = 1;
efi_status = generate_hash(data, datasize, context,
sha256hash, sha1hash);
in_protocol = 0;
return efi_status;
}
static EFI_STATUS shim_read_header(void *data, unsigned int datasize,
PE_COFF_LOADER_IMAGE_CONTEXT *context)
{
EFI_STATUS efi_status;
in_protocol = 1;
efi_status = read_header(data, datasize, context);
in_protocol = 0;
return efi_status;
}
/*
* Load and run an EFI executable
*/
EFI_STATUS start_image(EFI_HANDLE image_handle, CHAR16 *ImagePath)
{
EFI_STATUS efi_status;
EFI_LOADED_IMAGE *li, li_bak;
EFI_IMAGE_ENTRY_POINT entry_point;
EFI_PHYSICAL_ADDRESS alloc_address;
UINTN alloc_pages;
CHAR16 *PathName = NULL;
void *sourcebuffer = NULL;
UINT64 sourcesize = 0;
void *data = NULL;
int datasize;
/*
* We need to refer to the loaded image protocol on the running
* binary in order to find our path
*/
efi_status = gBS->HandleProtocol(image_handle, &EFI_LOADED_IMAGE_GUID,
(void **)&li);
if (EFI_ERROR(efi_status)) {
perror(L"Unable to init protocol\n");
return efi_status;
}
/*
* Build a new path from the existing one plus the executable name
*/
efi_status = generate_path_from_image_path(li, ImagePath, &PathName);
if (EFI_ERROR(efi_status)) {
perror(L"Unable to generate path %s: %r\n", ImagePath,
efi_status);
goto done;
}
if (findNetboot(li->DeviceHandle)) {
efi_status = parseNetbootinfo(image_handle);
if (EFI_ERROR(efi_status)) {
perror(L"Netboot parsing failed: %r\n", efi_status);
return EFI_PROTOCOL_ERROR;
}
efi_status = FetchNetbootimage(image_handle, &sourcebuffer,
&sourcesize);
if (EFI_ERROR(efi_status)) {
perror(L"Unable to fetch TFTP image: %r\n",
efi_status);
return efi_status;
}
data = sourcebuffer;
datasize = sourcesize;
} else if (find_httpboot(li->DeviceHandle)) {
efi_status = httpboot_fetch_buffer (image_handle,
&sourcebuffer,
&sourcesize);
if (EFI_ERROR(efi_status)) {
perror(L"Unable to fetch HTTP image: %r\n",
efi_status);
return efi_status;
}
data = sourcebuffer;
datasize = sourcesize;
} else {
/*
* Read the new executable off disk
*/
efi_status = load_image(li, &data, &datasize, PathName);
if (EFI_ERROR(efi_status)) {
perror(L"Failed to load image %s: %r\n",
PathName, efi_status);
PrintErrors();
ClearErrors();
goto done;
}
}
if (datasize < 0) {
efi_status = EFI_INVALID_PARAMETER;
goto done;
}
/*
* We need to modify the loaded image protocol entry before running
* the new binary, so back it up
*/
CopyMem(&li_bak, li, sizeof(li_bak));
/*
* Update the loaded image with the second stage loader file path
*/
li->FilePath = FileDevicePath(NULL, PathName);
if (!li->FilePath) {
perror(L"Unable to update loaded image file path\n");
efi_status = EFI_OUT_OF_RESOURCES;
goto restore;
}
/*
* Verify and, if appropriate, relocate and execute the executable
*/
efi_status = handle_image(data, datasize, li, &entry_point,
&alloc_address, &alloc_pages);
if (EFI_ERROR(efi_status)) {
perror(L"Failed to load image: %r\n", efi_status);
PrintErrors();
ClearErrors();
goto restore;
}
loader_is_participating = 0;
/*
* The binary is trusted and relocated. Run it
*/
efi_status = entry_point(image_handle, systab);
restore:
if (li->FilePath)
FreePool(li->FilePath);
/*
* Restore our original loaded image values
*/
CopyMem(li, &li_bak, sizeof(li_bak));
done:
if (PathName)
FreePool(PathName);
if (data)
FreePool(data);
return efi_status;
}
/*
* Load and run grub. If that fails because grub isn't trusted, load and
* run MokManager.
*/
EFI_STATUS init_grub(EFI_HANDLE image_handle)
{
EFI_STATUS efi_status;
int use_fb = should_use_fallback(image_handle);
efi_status = start_image(image_handle, use_fb ? FALLBACK :second_stage);
if (efi_status == EFI_SECURITY_VIOLATION ||
efi_status == EFI_ACCESS_DENIED) {
efi_status = start_image(image_handle, MOK_MANAGER);
if (EFI_ERROR(efi_status)) {
console_print(L"start_image() returned %r\n", efi_status);
msleep(2000000);
return efi_status;
}
efi_status = start_image(image_handle,
use_fb ? FALLBACK : second_stage);
}
if (EFI_ERROR(efi_status)) {
console_print(L"start_image() returned %r\n", efi_status);
msleep(2000000);
}
return efi_status;
}
static inline EFI_STATUS
get_load_option_optional_data(UINT8 *data, UINTN data_size,
UINT8 **od, UINTN *ods)
{
/*
* If it's not at least Attributes + FilePathListLength +
* Description=L"" + 0x7fff0400 (EndEntrireDevicePath), it can't
* be valid.
*/
if (data_size < (sizeof(UINT32) + sizeof(UINT16) + 2 + 4))
return EFI_INVALID_PARAMETER;
UINT8 *cur = data + sizeof(UINT32);
UINT16 fplistlen = *(UINT16 *)cur;
/*
* If there's not enough space for the file path list and the
* smallest possible description (L""), it's not valid.
*/
if (fplistlen > data_size - (sizeof(UINT32) + 2 + 4))
return EFI_INVALID_PARAMETER;
cur += sizeof(UINT16);
UINTN limit = data_size - (cur - data) - fplistlen;
UINTN i;
for (i = 0; i < limit ; i++) {
/* If the description isn't valid UCS2-LE, it's not valid. */
if (i % 2 != 0) {
if (cur[i] != 0)
return EFI_INVALID_PARAMETER;
} else if (cur[i] == 0) {
/* we've found the end */
i++;
if (i >= limit || cur[i] != 0)
return EFI_INVALID_PARAMETER;
break;
}
}
i++;
if (i > limit)
return EFI_INVALID_PARAMETER;
/*
* If i is limit, we know the rest of this is the FilePathList and
* there's no optional data. So just bail now.
*/
if (i == limit) {
*od = NULL;
*ods = 0;
return EFI_SUCCESS;
}
cur += i;
limit -= i;
limit += fplistlen;
i = 0;
while (limit - i >= 4) {
struct {
UINT8 type;
UINT8 subtype;
UINT16 len;
} dp = {
.type = cur[i],
.subtype = cur[i+1],
/*
* it's a little endian UINT16, but we're not
* guaranteed alignment is sane, so we can't just
* typecast it directly.
*/
.len = (cur[i+3] << 8) | cur[i+2],
};
/*
* We haven't found an EndEntire, so this has to be a valid
* EFI_DEVICE_PATH in order for the data to be valid. That
* means it has to fit, and it can't be smaller than 4 bytes.
*/
if (dp.len < 4 || dp.len > limit)
return EFI_INVALID_PARAMETER;
/*
* see if this is an EndEntire node...
*/
if (dp.type == 0x7f && dp.subtype == 0xff) {
/*
* if we've found the EndEntire node, it must be 4
* bytes
*/
if (dp.len != 4)
return EFI_INVALID_PARAMETER;
i += dp.len;
break;
}
/*
* It's just some random DP node; skip it.
*/
i += dp.len;
}
if (i != fplistlen)
return EFI_INVALID_PARAMETER;
/*
* if there's any space left, it's "optional data"
*/
*od = cur + i;
*ods = limit - i;
return EFI_SUCCESS;
}
static int is_our_path(EFI_LOADED_IMAGE *li, CHAR16 *path)
{
CHAR16 *dppath = NULL;
CHAR16 *PathName = NULL;
EFI_STATUS efi_status;
int ret = 1;
dppath = DevicePathToStr(li->FilePath);
if (!dppath)
return 0;
efi_status = generate_path_from_image_path(li, path, &PathName);
if (EFI_ERROR(efi_status)) {
perror(L"Unable to generate path %s: %r\n", path,
efi_status);
goto done;
}
dprint(L"dppath: %s\n", dppath);
dprint(L"path: %s\n", path);
if (StrnCaseCmp(dppath, PathName, StrLen(dppath)))
ret = 0;
done:
FreePool(dppath);
FreePool(PathName);
return ret;
}
/*
* Check the load options to specify the second stage loader
*/
EFI_STATUS set_second_stage (EFI_HANDLE image_handle)
{
EFI_STATUS efi_status;
EFI_LOADED_IMAGE *li = NULL;
CHAR16 *start = NULL;
int remaining_size = 0;
CHAR16 *loader_str = NULL;
UINTN loader_len = 0;
unsigned int i;
UINTN second_stage_len;
second_stage_len = (StrLen(DEFAULT_LOADER) + 1) * sizeof(CHAR16);
second_stage = AllocatePool(second_stage_len);
if (!second_stage) {
perror(L"Could not allocate %lu bytes\n", second_stage_len);
return EFI_OUT_OF_RESOURCES;
}
StrCpy(second_stage, DEFAULT_LOADER);
load_options = NULL;
load_options_size = 0;
efi_status = gBS->HandleProtocol(image_handle, &LoadedImageProtocol,
(void **) &li);
if (EFI_ERROR(efi_status)) {
perror (L"Failed to get load options: %r\n", efi_status);
return efi_status;
}
/* So, load options are a giant pain in the ass. If we're invoked
* from the EFI shell, we get something like this:
00000000 5c 00 45 00 36 00 49 00 5c 00 66 00 65 00 64 00 |\.E.F.I.\.f.e.d.|
00000010 6f 00 72 00 61 00 5c 00 73 00 68 00 69 00 6d 00 |o.r.a.\.s.h.i.m.|
00000020 78 00 36 00 34 00 2e 00 64 00 66 00 69 00 20 00 |x.6.4...e.f.i. .|
00000030 5c 00 45 00 46 00 49 00 5c 00 66 00 65 00 64 00 |\.E.F.I.\.f.e.d.|
00000040 6f 00 72 00 61 00 5c 00 66 00 77 00 75 00 70 00 |o.r.a.\.f.w.u.p.|
00000050 64 00 61 00 74 00 65 00 2e 00 65 00 66 00 20 00 |d.a.t.e.e.f.i. .|
00000060 00 00 66 00 73 00 30 00 3a 00 5c 00 00 00 |..f.s.0.:.\...|
*
* which is just some paths rammed together separated by a UCS-2 NUL.
* But if we're invoked from BDS, we get something more like:
*
00000000 01 00 00 00 62 00 4c 00 69 00 6e 00 75 00 78 00 |....b.L.i.n.u.x.|
00000010 20 00 46 00 69 00 72 00 6d 00 77 00 61 00 72 00 | .F.i.r.m.w.a.r.|
00000020 65 00 20 00 55 00 70 00 64 00 61 00 74 00 65 00 |e. .U.p.d.a.t.e.|
00000030 72 00 00 00 40 01 2a 00 01 00 00 00 00 08 00 00 |r.....*.........|
00000040 00 00 00 00 00 40 06 00 00 00 00 00 1a 9e 55 bf |.....@........U.|
00000050 04 57 f2 4f b4 4a ed 26 4a 40 6a 94 02 02 04 04 |.W.O.:.&J@j.....|
00000060 34 00 5c 00 45 00 46 00 49 00 5c 00 66 00 65 00 |4.\.E.F.I.f.e.d.|
00000070 64 00 6f 00 72 00 61 00 5c 00 73 00 68 00 69 00 |o.r.a.\.s.h.i.m.|
00000080 6d 00 78 00 36 00 34 00 2e 00 65 00 66 00 69 00 |x.6.4...e.f.i...|
00000090 00 00 7f ff 40 00 20 00 5c 00 66 00 77 00 75 00 |...... .\.f.w.u.|
000000a0 70 00 78 00 36 00 34 00 2e 00 65 00 66 00 69 00 |p.x.6.4...e.f.i.|
000000b0 00 00 |..|
*
* which is clearly an EFI_LOAD_OPTION filled in halfway reasonably.
* In short, the UEFI shell is still a useless piece of junk.
*
* But then on some versions of BDS, we get:
00000000 5c 00 66 00 77 00 75 00 70 00 78 00 36 00 34 00 |\.f.w.u.p.x.6.4.|
00000010 2e 00 65 00 66 00 69 00 00 00 |..e.f.i...|
0000001a
* which as you can see is one perfectly normal UCS2-EL string
* containing the load option from the Boot#### variable.
*
* We also sometimes find a guid or partial guid at the end, because
* BDS will add that, but we ignore that here.
*/
/*
* Maybe there just aren't any options...
*/
if (li->LoadOptionsSize == 0)
return EFI_SUCCESS;
/*
* In either case, we've got to have at least a UCS2 NUL...
*/
if (li->LoadOptionsSize < 2)
return EFI_BAD_BUFFER_SIZE;
/*
* Some awesome versions of BDS will add entries for Linux. On top
* of that, some versions of BDS will "tag" any Boot#### entries they
* create by putting a GUID at the very end of the optional data in
* the EFI_LOAD_OPTIONS, thus screwing things up for everybody who
* tries to actually *use* the optional data for anything. Why they
* did this instead of adding a flag to the spec to /say/ it's
* created by BDS, I do not know. For shame.
*
* Anyway, just nerf that out from the start. It's always just
* garbage at the end.
*/
if (li->LoadOptionsSize > 16) {
if (CompareGuid((EFI_GUID *)(li->LoadOptions
+ (li->LoadOptionsSize - 16)),
&BDS_GUID) == 0)
li->LoadOptionsSize -= 16;
}
/*
* Apparently sometimes we get L"\0\0"? Which isn't useful at all.
*/
if (is_all_nuls(li->LoadOptions, li->LoadOptionsSize))
return EFI_SUCCESS;
/*
* Check and see if this is just a list of strings. If it's an
* EFI_LOAD_OPTION, it'll be 0, since we know EndEntire device path
* won't pass muster as UCS2-LE.
*
* If there are 3 strings, we're launched from the shell most likely,
* But we actually only care about the second one.
*/
UINTN strings = count_ucs2_strings(li->LoadOptions,
li->LoadOptionsSize);
/*
* If it's not string data, try it as an EFI_LOAD_OPTION.
*/
if (strings == 0) {
/*
* We at least didn't find /enough/ strings. See if it works
* as an EFI_LOAD_OPTION.
*/
efi_status = get_load_option_optional_data(li->LoadOptions,
li->LoadOptionsSize,
(UINT8 **)&start,
&loader_len);
if (EFI_ERROR(efi_status))
return EFI_SUCCESS;
remaining_size = 0;
} else if (strings >= 2) {
/*
* UEFI shell copies the whole line of the command into
* LoadOptions. We ignore the string before the first L' ',
* i.e. the name of this program.
* Counting by two bytes is safe, because we know the size is
* compatible with a UCS2-LE string.
*/
UINT8 *cur = li->LoadOptions;
for (i = 0; i < li->LoadOptionsSize - 2; i += 2) {
CHAR16 c = (cur[i+1] << 8) | cur[i];
if (c == L' ') {
start = (CHAR16 *)&cur[i+2];
remaining_size = li->LoadOptionsSize - i - 2;
break;
}
}
if (!start || remaining_size <= 0 || start[0] == L'\0')
return EFI_SUCCESS;
for (i = 0; start[i] != '\0'; i++) {
if (start[i] == L' ')
start[i] = L'\0';
if (start[i] == L'\0') {
loader_len = 2 * i + 2;
break;
}
}
if (loader_len)
remaining_size -= loader_len;
} else {
/* only find one string */
start = li->LoadOptions;
loader_len = li->LoadOptionsSize;
}
/*
* Just to be sure all that math is right...
*/
if (loader_len % 2 != 0)
return EFI_INVALID_PARAMETER;
strings = count_ucs2_strings((UINT8 *)start, loader_len);
if (strings < 1)
return EFI_SUCCESS;
/*
* And then I found a version of BDS that gives us our own path in
* LoadOptions:
77162C58 5c 00 45 00 46 00 49 00 |\.E.F.I.|
77162C60 5c 00 42 00 4f 00 4f 00 54 00 5c 00 42 00 4f 00 |\.B.O.O.T.\.B.O.|
77162C70 4f 00 54 00 58 00 36 00 34 00 2e 00 45 00 46 00 |O.T.X.6.4...E.F.|
77162C80 49 00 00 00 |I...|
* which is just cruel... So yeah, just don't use it.
*/
if (strings == 1 && is_our_path(li, start))
return EFI_SUCCESS;
/*
* Set up the name of the alternative loader and the LoadOptions for
* the loader
*/
if (loader_len > 0) {
loader_str = AllocatePool(loader_len);
if (!loader_str) {
perror(L"Failed to allocate loader string\n");
return EFI_OUT_OF_RESOURCES;
}
for (i = 0; i < loader_len / 2; i++)
loader_str[i] = start[i];
loader_str[loader_len/2-1] = L'\0';
second_stage = loader_str;
load_options = remaining_size ? start + (loader_len/2) : NULL;
load_options_size = remaining_size;
}
return EFI_SUCCESS;
}
static void *
ossl_malloc(size_t num)
{
return AllocatePool(num);
}
static void
ossl_free(void *addr)
{
FreePool(addr);
}
static void
init_openssl(void)
{
CRYPTO_set_mem_functions(ossl_malloc, NULL, ossl_free);
OPENSSL_init();
CRYPTO_set_mem_functions(ossl_malloc, NULL, ossl_free);
ERR_load_ERR_strings();
ERR_load_BN_strings();
ERR_load_RSA_strings();
ERR_load_DH_strings();
ERR_load_EVP_strings();
ERR_load_BUF_strings();
ERR_load_OBJ_strings();
ERR_load_PEM_strings();
ERR_load_X509_strings();
ERR_load_ASN1_strings();
ERR_load_CONF_strings();
ERR_load_CRYPTO_strings();
ERR_load_COMP_strings();
ERR_load_BIO_strings();
ERR_load_PKCS7_strings();
ERR_load_X509V3_strings();
ERR_load_PKCS12_strings();
ERR_load_RAND_strings();
ERR_load_DSO_strings();
ERR_load_OCSP_strings();
}
static SHIM_LOCK shim_lock_interface;
static EFI_HANDLE shim_lock_handle;
EFI_STATUS
install_shim_protocols(void)
{
SHIM_LOCK *shim_lock;
EFI_STATUS efi_status;
/*
* Did another instance of shim earlier already install the
* protocol? If so, get rid of it.
*
* We have to uninstall shim's protocol here, because if we're
* On the fallback.efi path, then our call pathway is:
*
* shim->fallback->shim->grub
* ^ ^ ^
* | | \- gets protocol #0
* | \- installs its protocol (#1)
* \- installs its protocol (#0)
* and if we haven't removed this, then grub will get the *first*
* shim's protocol, but it'll get the second shim's systab
* replacements. So even though it will participate and verify
* the kernel, the systab never finds out.
*/
efi_status = LibLocateProtocol(&SHIM_LOCK_GUID, (VOID **)&shim_lock);
if (!EFI_ERROR(efi_status))
uninstall_shim_protocols();
/*
* Install the protocol
*/
efi_status = gBS->InstallProtocolInterface(&shim_lock_handle,
&SHIM_LOCK_GUID,
EFI_NATIVE_INTERFACE,
&shim_lock_interface);
if (EFI_ERROR(efi_status)) {
console_error(L"Could not install security protocol",
efi_status);
return efi_status;
}
if (!secure_mode())
return EFI_SUCCESS;
#if defined(OVERRIDE_SECURITY_POLICY)
/*
* Install the security protocol hook
*/
security_policy_install(shim_verify);
#endif
return EFI_SUCCESS;
}
void
uninstall_shim_protocols(void)
{
/*
* If we're back here then clean everything up before exiting
*/
gBS->UninstallProtocolInterface(shim_lock_handle, &SHIM_LOCK_GUID,
&shim_lock_interface);
if (!secure_mode())
return;
#if defined(OVERRIDE_SECURITY_POLICY)
/*
* Clean up the security protocol hook
*/
security_policy_uninstall();
#endif
}
EFI_STATUS
shim_init(void)
{
EFI_STATUS efi_status;
dprint(L"%a", shim_version);
/* Set the second stage loader */
efi_status = set_second_stage(global_image_handle);
if (EFI_ERROR(efi_status)) {
perror(L"set_second_stage() failed: %r\n", efi_status);
return efi_status;
}
if (secure_mode()) {
if (vendor_authorized_size || vendor_deauthorized_size) {
/*
* If shim includes its own certificates then ensure
* that anything it boots has performed some
* validation of the next image.
*/
hook_system_services(systab);
loader_is_participating = 0;
}
}
hook_exit(systab);
efi_status = install_shim_protocols();
if (EFI_ERROR(efi_status))
perror(L"install_shim_protocols() failed: %r\n", efi_status);
return efi_status;
}
void
shim_fini(void)
{
/*
* Remove our protocols
*/
uninstall_shim_protocols();
if (secure_mode()) {
/*
* Remove our hooks from system services.
*/
unhook_system_services();
}
unhook_exit();
/*
* Free the space allocated for the alternative 2nd stage loader
*/
if (load_options_size > 0 && second_stage)
FreePool(second_stage);
console_fini();
}
extern EFI_STATUS
efi_main(EFI_HANDLE passed_image_handle, EFI_SYSTEM_TABLE *passed_systab);
static void
__attribute__((__optimize__("0")))
debug_hook(void)
{
UINT8 *data = NULL;
UINTN dataSize = 0;
EFI_STATUS efi_status;
register volatile UINTN x = 0;
extern char _text, _data;
const CHAR16 * const debug_var_name =
#ifdef ENABLE_SHIM_DEVEL
L"SHIM_DEVEL_DEBUG";
#else
L"SHIM_DEBUG";
#endif
if (x)
return;
efi_status = get_variable(debug_var_name, &data, &dataSize,
SHIM_LOCK_GUID);
if (EFI_ERROR(efi_status)) {
return;
}
FreePool(data);
console_print(L"add-symbol-file "DEBUGDIR
L"shim" EFI_ARCH L".efi.debug 0x%08x -s .data 0x%08x\n",
&_text, &_data);
console_print(L"Pausing for debugger attachment.\n");
console_print(L"To disable this, remove the EFI variable %s-%g .\n",
debug_var_name, &SHIM_LOCK_GUID);
x = 1;
while (x++) {
/* Make this so it can't /totally/ DoS us. */
#if defined(__x86_64__) || defined(__i386__) || defined(__i686__)
if (x > 4294967294ULL)
break;
#elif defined(__aarch64__)
if (x > 1000)
break;
#else
if (x > 12000)
break;
#endif
pause();
}
x = 1;
}
EFI_STATUS
efi_main (EFI_HANDLE passed_image_handle, EFI_SYSTEM_TABLE *passed_systab)
{
EFI_STATUS efi_status;
EFI_HANDLE image_handle;
verification_method = VERIFIED_BY_NOTHING;
vendor_authorized_size = cert_table.vendor_authorized_size;
vendor_authorized = (UINT8 *)&cert_table + cert_table.vendor_authorized_offset;
vendor_deauthorized_size = cert_table.vendor_deauthorized_size;
vendor_deauthorized = (UINT8 *)&cert_table + cert_table.vendor_deauthorized_offset;
#if defined(ENABLE_SHIM_CERT)
build_cert_size = sizeof(shim_cert);
build_cert = shim_cert;
#endif /* defined(ENABLE_SHIM_CERT) */
CHAR16 *msgs[] = {
L"import_mok_state() failed",
L"shim_init() failed",
NULL
};
int msg = 0;
/*
* Set up the shim lock protocol so that grub and MokManager can
* call back in and use shim functions
*/
shim_lock_interface.Verify = shim_verify;
shim_lock_interface.Hash = shim_hash;
shim_lock_interface.Context = shim_read_header;
systab = passed_systab;
image_handle = global_image_handle = passed_image_handle;
/*
* Ensure that gnu-efi functions are available
*/
InitializeLib(image_handle, systab);
setup_verbosity();
dprint(L"vendor_authorized:0x%08lx vendor_authorized_size:%lu\n",
vendor_authorized, vendor_authorized_size);
dprint(L"vendor_deauthorized:0x%08lx vendor_deauthorized_size:%lu\n",
vendor_deauthorized, vendor_deauthorized_size);
init_openssl();
/*
* if SHIM_DEBUG is set, wait for a debugger to attach.
*/
debug_hook();
/*
* Before we do anything else, validate our non-volatile,
* boot-services-only state variables are what we think they are.
*/
efi_status = import_mok_state(image_handle);
if (!secure_mode() && efi_status == EFI_INVALID_PARAMETER) {
/*
* Make copy failures fatal only if secure_mode is enabled, or
* the error was anything else than EFI_INVALID_PARAMETER.
* There are non-secureboot firmware implementations that don't
* reserve enough EFI variable memory to fit the variable.
*/
console_print(L"Importing MOK states has failed: %s: %r\n",
msgs[msg], efi_status);
console_print(L"Continuing boot since secure mode is disabled");
} else if (EFI_ERROR(efi_status)) {
die:
console_print(L"Something has gone seriously wrong: %s: %r\n",
msgs[msg], efi_status);
msleep(5000000);
gRT->ResetSystem(EfiResetShutdown, EFI_SECURITY_VIOLATION,
0, NULL);
}
efi_status = shim_init();
if (EFI_ERROR(efi_status)) {
msg = 1;
goto die;
}
/*
* Tell the user that we're in insecure mode if necessary
*/
if (user_insecure_mode) {
console_print(L"Booting in insecure mode\n");
msleep(2000000);
}
/*
* Hand over control to the second stage bootloader
*/
efi_status = init_grub(image_handle);
shim_fini();
return efi_status;
}
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