1 files changed, 108 insertions, 0 deletions
diff --git a/src/boot/efi/shim.c b/src/boot/efi/shim.c
new file mode 100644
index 0000000..df136ed
--- /dev/null
+++ b/src/boot/efi/shim.c
@@ -0,0 +1,108 @@
+/* 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 "device-path-util.h"
+#include "secure-boot.h"
+#include "shim.h"
+#include "util.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) (const void *buffer, uint32_t 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_t datasize, void *context, uint8_t *sha256hash, uint8_t *sha1hash);
+
+        EFI_STATUS __sysv_abi__ (*read_header) (void *data, uint32_t datasize, void *context);
+};
+
+#define SHIM_LOCK_GUID \
+        { 0x605dab50, 0xe046, 0x4300, { 0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23 } }
+
+bool shim_loaded(void) {
+        struct ShimLock *shim_lock;
+
+        return BS->LocateProtocol(MAKE_GUID_PTR(SHIM_LOCK), NULL, (void **) &shim_lock) == EFI_SUCCESS;
+}
+
+static bool shim_validate(
+                const void *ctx, const EFI_DEVICE_PATH *device_path, const void *file_buffer, size_t file_size) {
+
+        EFI_STATUS err;
+        _cleanup_free_ char *file_buffer_owned = NULL;
+
+        if (!file_buffer) {
+                if (!device_path)
+                        return false;
+
+                EFI_HANDLE device_handle;
+                EFI_DEVICE_PATH *file_dp = (EFI_DEVICE_PATH *) device_path;
+                err = BS->LocateDevicePath(
+                                MAKE_GUID_PTR(EFI_SIMPLE_FILE_SYSTEM_PROTOCOL), &file_dp, &device_handle);
+                if (err != EFI_SUCCESS)
+                        return false;
+
+                _cleanup_(file_closep) EFI_FILE *root = NULL;
+                err = open_volume(device_handle, &root);
+                if (err != EFI_SUCCESS)
+                        return false;
+
+                _cleanup_free_ char16_t *dp_str = NULL;
+                err = device_path_to_str(file_dp, &dp_str);
+                if (err != EFI_SUCCESS)
+                        return false;
+
+                err = file_read(root, dp_str, 0, 0, &file_buffer_owned, &file_size);
+                if (err != EFI_SUCCESS)
+                        return false;
+
+                file_buffer = file_buffer_owned;
+        }
+
+        struct ShimLock *shim_lock;
+        err = BS->LocateProtocol(MAKE_GUID_PTR(SHIM_LOCK), NULL, (void **) &shim_lock);
+        if (err != EFI_SUCCESS)
+                return false;
+
+        return shim_lock->shim_verify(file_buffer, file_size) == EFI_SUCCESS;
+}
+
+EFI_STATUS shim_load_image(EFI_HANDLE parent, const EFI_DEVICE_PATH *device_path, EFI_HANDLE *ret_image) {
+        assert(device_path);
+        assert(ret_image);
+
+        bool have_shim = shim_loaded();
+
+        if (have_shim)
+                install_security_override(shim_validate, NULL);
+
+        EFI_STATUS ret = BS->LoadImage(
+                        /*BootPolicy=*/false, parent, (EFI_DEVICE_PATH *) device_path, NULL, 0, ret_image);
+
+        if (have_shim)
+                uninstall_security_override();
+
+        return ret;
+}
+
+void shim_retain_protocol(void) {
+        uint8_t value = 1;
+
+        /* Ask Shim to avoid uninstalling its security protocol, so that we can use it from sd-stub to
+         * validate PE addons. By default, Shim uninstalls its protocol when calling StartImage().
+         * Requires Shim 15.8. */
+        (void) efivar_set_raw(MAKE_GUID_PTR(SHIM_LOCK), u"ShimRetainProtocol", &value, sizeof(value), 0);
+}