diff options
Diffstat (limited to 'src/boot/efi/secure-boot.c')
| -rw-r--r-- | src/boot/efi/secure-boot.c | 223 |
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; +} |