1 files changed, 223 insertions, 0 deletions
diff --git a/src/boot/efi/secure-boot.c b/src/boot/efi/secure-boot.c
new file mode 100644
index 0000000..f76d2f4
--- /dev/null
+++ b/src/boot/efi/secure-boot.c
@@ -0,0 +1,223 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "console.h"
+#include "proto/security-arch.h"
+#include "secure-boot.h"
+#include "util.h"
+#include "vmm.h"
+
+bool secure_boot_enabled(void) {
+        bool secure = false;  /* avoid false maybe-uninitialized warning */
+        EFI_STATUS err;
+
+        err = efivar_get_boolean_u8(MAKE_GUID_PTR(EFI_GLOBAL_VARIABLE), u"SecureBoot", &secure);
+
+        return err == EFI_SUCCESS && secure;
+}
+
+SecureBootMode secure_boot_mode(void) {
+        bool secure, audit = false, deployed = false, setup = false;
+        EFI_STATUS err;
+
+        err = efivar_get_boolean_u8(MAKE_GUID_PTR(EFI_GLOBAL_VARIABLE), u"SecureBoot", &secure);
+        if (err != EFI_SUCCESS)
+                return SECURE_BOOT_UNSUPPORTED;
+
+        /* We can assume false for all these if they are abscent (AuditMode and
+         * DeployedMode may not exist on older firmware). */
+        (void) efivar_get_boolean_u8(MAKE_GUID_PTR(EFI_GLOBAL_VARIABLE), u"AuditMode", &audit);
+        (void) efivar_get_boolean_u8(MAKE_GUID_PTR(EFI_GLOBAL_VARIABLE), u"DeployedMode", &deployed);
+        (void) efivar_get_boolean_u8(MAKE_GUID_PTR(EFI_GLOBAL_VARIABLE), u"SetupMode", &setup);
+
+        return decode_secure_boot_mode(secure, audit, deployed, setup);
+}
+
+EFI_STATUS secure_boot_enroll_at(EFI_FILE *root_dir, const char16_t *path, bool force) {
+        assert(root_dir);
+        assert(path);
+
+        EFI_STATUS err;
+
+        clear_screen(COLOR_NORMAL);
+
+        /* Enrolling secure boot keys is safe to do in virtualized environments as there is nothing
+         * we can brick there. */
+        bool is_safe = in_hypervisor();
+
+        if (!is_safe && !force)
+                return EFI_SUCCESS;
+
+        printf("Enrolling secure boot keys from directory: %ls\n", path);
+
+        if (!is_safe) {
+                printf("Warning: Enrolling custom Secure Boot keys might soft-brick your machine!\n");
+
+                unsigned timeout_sec = 15;
+                for (;;) {
+                        printf("\rEnrolling in %2u s, press any key to abort.", timeout_sec);
+
+                        uint64_t key;
+                        err = console_key_read(&key, 1000 * 1000);
+                        if (err == EFI_NOT_READY)
+                                continue;
+                        if (err == EFI_TIMEOUT) {
+                                if (timeout_sec == 0) /* continue enrolling keys */
+                                        break;
+                                timeout_sec--;
+                                continue;
+                        }
+                        if (err != EFI_SUCCESS)
+                                return log_error_status(
+                                                err,
+                                                "Error waiting for user input to enroll Secure Boot keys: %m");
+
+                        /* user aborted, returning EFI_SUCCESS here allows the user to go back to the menu */
+                        return EFI_SUCCESS;
+                }
+
+                printf("\n");
+        }
+
+        _cleanup_(file_closep) EFI_FILE *dir = NULL;
+
+        err = open_directory(root_dir, path, &dir);
+        if (err != EFI_SUCCESS)
+                return log_error_status(err, "Failed opening keys directory %ls: %m", path);
+
+        struct {
+                const char16_t *name;
+                const char16_t *filename;
+                const EFI_GUID vendor;
+                char *buffer;
+                size_t size;
+        } sb_vars[] = {
+                { u"db",  u"db.auth",  EFI_IMAGE_SECURITY_DATABASE_GUID, NULL, 0 },
+                { u"KEK", u"KEK.auth", EFI_GLOBAL_VARIABLE, NULL, 0 },
+                { u"PK",  u"PK.auth",  EFI_GLOBAL_VARIABLE, NULL, 0 },
+        };
+
+        /* Make sure all keys files exist before we start enrolling them by loading them from the disk first. */
+        for (size_t i = 0; i < ELEMENTSOF(sb_vars); i++) {
+                err = file_read(dir, sb_vars[i].filename, 0, 0, &sb_vars[i].buffer, &sb_vars[i].size);
+                if (err != EFI_SUCCESS) {
+                        log_error_status(err, "Failed reading file %ls\\%ls: %m", path, sb_vars[i].filename);
+                        goto out_deallocate;
+                }
+        }
+
+        for (size_t i = 0; i < ELEMENTSOF(sb_vars); i++) {
+                uint32_t sb_vars_opts =
+                        EFI_VARIABLE_NON_VOLATILE |
+                        EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                        EFI_VARIABLE_RUNTIME_ACCESS |
+                        EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS;
+
+                err = efivar_set_raw(&sb_vars[i].vendor, sb_vars[i].name, sb_vars[i].buffer, sb_vars[i].size, sb_vars_opts);
+                if (err != EFI_SUCCESS) {
+                        log_error_status(err, "Failed to write %ls secure boot variable: %m", sb_vars[i].name);
+                        goto out_deallocate;
+                }
+        }
+
+        printf("Custom Secure Boot keys successfully enrolled, rebooting the system now!\n");
+        /* The system should be in secure boot mode now and we could continue a regular boot. But at least
+         * TPM PCR7 measurements should change on next boot. Reboot now so that any OS we load does not end
+         * up relying on the old PCR state. */
+        RT->ResetSystem(EfiResetCold, EFI_SUCCESS, 0, NULL);
+        assert_not_reached();
+
+out_deallocate:
+        for (size_t i = 0; i < ELEMENTSOF(sb_vars); i++)
+                free(sb_vars[i].buffer);
+
+        return err;
+}
+
+static struct SecurityOverride {
+        EFI_SECURITY_ARCH_PROTOCOL *security;
+        EFI_SECURITY2_ARCH_PROTOCOL *security2;
+        EFI_SECURITY_FILE_AUTHENTICATION_STATE original_hook;
+        EFI_SECURITY2_FILE_AUTHENTICATION original_hook2;
+
+        security_validator_t validator;
+        const void *validator_ctx;
+} security_override;
+
+static EFIAPI EFI_STATUS security_hook(
+                const EFI_SECURITY_ARCH_PROTOCOL *this,
+                uint32_t authentication_status,
+                const EFI_DEVICE_PATH *file) {
+
+        assert(security_override.validator);
+        assert(security_override.security);
+        assert(security_override.original_hook);
+
+        if (security_override.validator(security_override.validator_ctx, file, NULL, 0))
+                return EFI_SUCCESS;
+
+        return security_override.original_hook(security_override.security, authentication_status, file);
+}
+
+static EFIAPI EFI_STATUS security2_hook(
+                const EFI_SECURITY2_ARCH_PROTOCOL *this,
+                const EFI_DEVICE_PATH *device_path,
+                void *file_buffer,
+                size_t file_size,
+                bool boot_policy) {
+
+        assert(security_override.validator);
+        assert(security_override.security2);
+        assert(security_override.original_hook2);
+
+        if (security_override.validator(security_override.validator_ctx, device_path, file_buffer, file_size))
+                return EFI_SUCCESS;
+
+        return security_override.original_hook2(
+                        security_override.security2, device_path, file_buffer, file_size, boot_policy);
+}
+
+/* This replaces the platform provided security arch protocols hooks (defined in the UEFI Platform
+ * Initialization Specification) with our own that uses the given validator to decide if a image is to be
+ * trusted. If not running in secure boot or the protocols are not available nothing happens. The override
+ * must be removed with uninstall_security_override() after LoadImage() has been called.
+ *
+ * This is a hack as we do not own the security protocol instances and modifying them is not an official part
+ * of their spec. But there is little else we can do to circumvent secure boot short of implementing our own
+ * PE loader. We could replace the firmware instances with our own instance using
+ * ReinstallProtocolInterface(), but some firmware will still use the old ones. */
+void install_security_override(security_validator_t validator, const void *validator_ctx) {
+        EFI_STATUS err;
+
+        assert(validator);
+
+        if (!secure_boot_enabled())
+                return;
+
+        security_override = (struct SecurityOverride) {
+                .validator = validator,
+                .validator_ctx = validator_ctx,
+        };
+
+        EFI_SECURITY_ARCH_PROTOCOL *security = NULL;
+        err = BS->LocateProtocol(MAKE_GUID_PTR(EFI_SECURITY_ARCH_PROTOCOL), NULL, (void **) &security);
+        if (err == EFI_SUCCESS) {
+                security_override.security = security;
+                security_override.original_hook = security->FileAuthenticationState;
+                security->FileAuthenticationState = security_hook;
+        }
+
+        EFI_SECURITY2_ARCH_PROTOCOL *security2 = NULL;
+        err = BS->LocateProtocol(MAKE_GUID_PTR(EFI_SECURITY2_ARCH_PROTOCOL), NULL, (void **) &security2);
+        if (err == EFI_SUCCESS) {
+                security_override.security2 = security2;
+                security_override.original_hook2 = security2->FileAuthentication;
+                security2->FileAuthentication = security2_hook;
+        }
+}
+
+void uninstall_security_override(void) {
+        if (security_override.original_hook)
+                security_override.security->FileAuthenticationState = security_override.original_hook;
+        if (security_override.original_hook2)
+                security_override.security2->FileAuthentication = security_override.original_hook2;
+}