diff options
Diffstat (limited to 'src/boot/efi/shim.c')
| -rw-r--r-- | src/boot/efi/shim.c | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/src/boot/efi/shim.c b/src/boot/efi/shim.c new file mode 100644 index 0000000..f6ffed1 --- /dev/null +++ b/src/boot/efi/shim.c @@ -0,0 +1,207 @@ +/* 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" + +/* 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 happend 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; +} |