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/* SPDX-License-Identifier: LGPL-2.1+ */
/*
* Port to systemd-boot
* Copyright © 2017 Max Resch <resch.max@gmail.com>
*
* Security Policy Handling
* Copyright © 2012 <James.Bottomley@HansenPartnership.com>
* https://github.com/mjg59/efitools
*/
#include <efi.h>
#include <efilib.h>
#include "util.h"
#include "shim.h"
#if defined(__x86_64__) || defined(__i386__)
#define __sysv_abi__ __attribute__((sysv_abi))
#else
#define __sysv_abi__
#endif
struct ShimLock {
EFI_STATUS __sysv_abi__ (*shim_verify) (VOID *buffer, UINT32 size);
/* context is actually a struct for the PE header, but it isn't needed so void is sufficient just do define the interface
* see shim.c/shim.h and PeHeader.h in the github shim repo */
EFI_STATUS __sysv_abi__ (*generate_hash) (VOID *data, UINT32 datasize, VOID *context, UINT8 *sha256hash, UINT8 *sha1hash);
EFI_STATUS __sysv_abi__ (*read_header) (VOID *data, UINT32 datasize, VOID *context);
};
static const EFI_GUID simple_fs_guid = SIMPLE_FILE_SYSTEM_PROTOCOL;
static const EFI_GUID global_guid = EFI_GLOBAL_VARIABLE;
static const EFI_GUID security_protocol_guid = { 0xa46423e3, 0x4617, 0x49f1, {0xb9, 0xff, 0xd1, 0xbf, 0xa9, 0x11, 0x58, 0x39 } };
static const EFI_GUID security2_protocol_guid = { 0x94ab2f58, 0x1438, 0x4ef1, {0x91, 0x52, 0x18, 0x94, 0x1a, 0x3a, 0x0e, 0x68 } };
static const EFI_GUID shim_lock_guid = { 0x605dab50, 0xe046, 0x4300, {0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23} };
BOOLEAN shim_loaded(void) {
struct ShimLock *shim_lock;
return uefi_call_wrapper(BS->LocateProtocol, 3, (EFI_GUID*) &shim_lock_guid, NULL, (VOID**) &shim_lock) == EFI_SUCCESS;
}
static BOOLEAN shim_validate(VOID *data, UINT32 size) {
struct ShimLock *shim_lock;
if (!data)
return FALSE;
if (uefi_call_wrapper(BS->LocateProtocol, 3, (EFI_GUID*) &shim_lock_guid, NULL, (VOID**) &shim_lock) != EFI_SUCCESS)
return FALSE;
if (!shim_lock)
return FALSE;
return shim_lock->shim_verify(data, size) == EFI_SUCCESS;
}
BOOLEAN secure_boot_enabled(void) {
_cleanup_freepool_ CHAR8 *b = NULL;
UINTN size;
if (efivar_get_raw(&global_guid, L"SecureBoot", &b, &size) == EFI_SUCCESS)
return *b > 0;
return FALSE;
}
/*
* See the UEFI Platform Initialization manual (Vol2: DXE) for this
*/
struct _EFI_SECURITY2_PROTOCOL;
struct _EFI_SECURITY_PROTOCOL;
struct _EFI_DEVICE_PATH_PROTOCOL;
typedef struct _EFI_SECURITY2_PROTOCOL EFI_SECURITY2_PROTOCOL;
typedef struct _EFI_SECURITY_PROTOCOL EFI_SECURITY_PROTOCOL;
typedef struct _EFI_DEVICE_PATH_PROTOCOL EFI_DEVICE_PATH_PROTOCOL;
typedef EFI_STATUS (EFIAPI *EFI_SECURITY_FILE_AUTHENTICATION_STATE) (
const EFI_SECURITY_PROTOCOL *This,
UINT32 AuthenticationStatus,
const EFI_DEVICE_PATH_PROTOCOL *File
);
typedef EFI_STATUS (EFIAPI *EFI_SECURITY2_FILE_AUTHENTICATION) (
const EFI_SECURITY2_PROTOCOL *This,
const EFI_DEVICE_PATH_PROTOCOL *DevicePath,
VOID *FileBuffer,
UINTN FileSize,
BOOLEAN BootPolicy
);
struct _EFI_SECURITY2_PROTOCOL {
EFI_SECURITY2_FILE_AUTHENTICATION FileAuthentication;
};
struct _EFI_SECURITY_PROTOCOL {
EFI_SECURITY_FILE_AUTHENTICATION_STATE FileAuthenticationState;
};
/* Handle to the original authenticator for security1 protocol */
static EFI_SECURITY_FILE_AUTHENTICATION_STATE esfas = NULL;
/* Handle to the original authenticator for security2 protocol */
static EFI_SECURITY2_FILE_AUTHENTICATION es2fa = NULL;
/*
* Perform shim/MOK and Secure Boot authentication on a binary that's already been
* loaded into memory. This function does the platform SB authentication first
* but preserves its return value in case of its failure, so that it can be
* returned in case of a shim/MOK authentication failure. This is done because
* the SB failure code seems to vary from one implementation to another, and I
* don't want to interfere with that at this time.
*/
static EFIAPI EFI_STATUS security2_policy_authentication (const EFI_SECURITY2_PROTOCOL *this,
const EFI_DEVICE_PATH_PROTOCOL *device_path,
VOID *file_buffer, UINTN file_size, BOOLEAN boot_policy) {
EFI_STATUS status;
/* Chain original security policy */
status = uefi_call_wrapper(es2fa, 5, this, device_path, file_buffer, file_size, boot_policy);
/* if OK, don't bother with MOK check */
if (status == EFI_SUCCESS)
return status;
if (shim_validate(file_buffer, file_size))
return EFI_SUCCESS;
return status;
}
/*
* Perform both shim/MOK and platform Secure Boot authentication. This function loads
* the file and performs shim/MOK authentication first simply to avoid double loads
* of Linux kernels, which are much more likely to be shim/MOK-signed than platform-signed,
* since kernels are big and can take several seconds to load on some computers and
* filesystems. This also has the effect of returning whatever the platform code is for
* authentication failure, be it EFI_ACCESS_DENIED, EFI_SECURITY_VIOLATION, or something
* else. (This seems to vary between implementations.)
*/
static EFIAPI EFI_STATUS security_policy_authentication (const EFI_SECURITY_PROTOCOL *this, UINT32 authentication_status,
const EFI_DEVICE_PATH_PROTOCOL *device_path_const) {
EFI_STATUS status;
_cleanup_freepool_ EFI_DEVICE_PATH *dev_path = NULL;
_cleanup_freepool_ CHAR16 *dev_path_str = NULL;
EFI_HANDLE h;
EFI_FILE *root;
_cleanup_freepool_ CHAR8 *file_buffer = NULL;
UINTN file_size;
if (!device_path_const)
return EFI_INVALID_PARAMETER;
dev_path = DuplicateDevicePath((EFI_DEVICE_PATH*) device_path_const);
status = uefi_call_wrapper(BS->LocateDevicePath, 3, (EFI_GUID*) &simple_fs_guid, &dev_path, &h);
if (status != EFI_SUCCESS)
return status;
/* No need to check return value, this already happened in efi_main() */
root = LibOpenRoot(h);
dev_path_str = DevicePathToStr(dev_path);
status = file_read(root, dev_path_str, 0, 0, &file_buffer, &file_size);
if (EFI_ERROR(status))
return status;
uefi_call_wrapper(root->Close, 1, root);
if (shim_validate(file_buffer, file_size))
return EFI_SUCCESS;
/* Try using the platform's native policy.... */
return uefi_call_wrapper(esfas, 3, this, authentication_status, device_path_const);
}
EFI_STATUS security_policy_install(void) {
EFI_SECURITY_PROTOCOL *security_protocol;
EFI_SECURITY2_PROTOCOL *security2_protocol = NULL;
EFI_STATUS status;
/* Already Installed */
if (esfas)
return EFI_ALREADY_STARTED;
/*
* Don't bother with status here. The call is allowed
* to fail, since SECURITY2 was introduced in PI 1.2.1.
* Use security2_protocol == NULL as indicator.
*/
uefi_call_wrapper(BS->LocateProtocol, 3, (EFI_GUID*) &security2_protocol_guid, NULL, (VOID**) &security2_protocol);
status = uefi_call_wrapper(BS->LocateProtocol, 3, (EFI_GUID*) &security_protocol_guid, NULL, (VOID**) &security_protocol);
/* This one is mandatory, so there's a serious problem */
if (status != EFI_SUCCESS)
return status;
esfas = security_protocol->FileAuthenticationState;
security_protocol->FileAuthenticationState = security_policy_authentication;
if (security2_protocol) {
es2fa = security2_protocol->FileAuthentication;
security2_protocol->FileAuthentication = security2_policy_authentication;
}
return EFI_SUCCESS;
}
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