/* SPDX-License-Identifier: LGPL-2.1+ */ /* * Port to systemd-boot * Copyright © 2017 Max Resch * * Security Policy Handling * Copyright © 2012 * https://github.com/mjg59/efitools */ #include #include #include "util.h" #include "shim.h" /* well known shim lock guid */ #define SHIM_LOCK_GUID struct ShimLock { EFI_STATUS __attribute__((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 __attribute__((sysv_abi)) (*generate_hash) (VOID *data, UINT32 datasize, VOID *context, UINT8 *sha256hash, UINT8 *sha1hash); EFI_STATUS __attribute__((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; }