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-rw-r--r--src/boot/efi/shim.c210
1 files changed, 210 insertions, 0 deletions
diff --git a/src/boot/efi/shim.c b/src/boot/efi/shim.c
new file mode 100644
index 0000000..3dc1008
--- /dev/null
+++ b/src/boot/efi/shim.c
@@ -0,0 +1,210 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * 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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