diff options
| -rw-r--r-- | arch/x86/boot/compressed/eboot.c | 3 | ||||
| -rw-r--r-- | drivers/firmware/efi/Kconfig | 10 | ||||
| -rw-r--r-- | drivers/firmware/efi/libstub/Makefile | 1 | ||||
| -rw-r--r-- | drivers/firmware/efi/libstub/arm-stub.c | 3 | ||||
| -rw-r--r-- | drivers/firmware/efi/libstub/tpm.c | 58 | ||||
| -rw-r--r-- | include/linux/efi.h | 7 |
6 files changed, 82 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c index c3e869eaef0c..a1686f3dc295 100644 --- a/arch/x86/boot/compressed/eboot.c +++ b/arch/x86/boot/compressed/eboot.c @@ -997,6 +997,9 @@ struct boot_params *efi_main(struct efi_config *c, if (boot_params->secure_boot == efi_secureboot_mode_unset) boot_params->secure_boot = efi_get_secureboot(sys_table); + /* Ask the firmware to clear memory on unclean shutdown */ + efi_enable_reset_attack_mitigation(sys_table); + setup_graphics(boot_params); setup_efi_pci(boot_params); diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig index 394db40ed374..2b4c39fdfa91 100644 --- a/drivers/firmware/efi/Kconfig +++ b/drivers/firmware/efi/Kconfig @@ -151,6 +151,16 @@ config APPLE_PROPERTIES If unsure, say Y if you have a Mac. Otherwise N. +config RESET_ATTACK_MITIGATION + bool "Reset memory attack mitigation" + depends on EFI_STUB + help + Request that the firmware clear the contents of RAM after a reboot + using the TCG Platform Reset Attack Mitigation specification. This + protects against an attacker forcibly rebooting the system while it + still contains secrets in RAM, booting another OS and extracting the + secrets. + endmenu config UEFI_CPER diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index cf81e6cf5ae8..dedf9bde44db 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -30,6 +30,7 @@ OBJECT_FILES_NON_STANDARD := y KCOV_INSTRUMENT := n lib-y := efi-stub-helper.o gop.o secureboot.o +lib-$(CONFIG_RESET_ATTACK_MITIGATION) += tpm.o # include the stub's generic dependencies from lib/ when building for ARM/arm64 arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c index 8181ac179d14..1cb2d1c070c3 100644 --- a/drivers/firmware/efi/libstub/arm-stub.c +++ b/drivers/firmware/efi/libstub/arm-stub.c @@ -192,6 +192,9 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, goto fail_free_cmdline; } + /* Ask the firmware to clear memory on unclean shutdown */ + efi_enable_reset_attack_mitigation(sys_table); + secure_boot = efi_get_secureboot(sys_table); /* diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c new file mode 100644 index 000000000000..6224cdbc9669 --- /dev/null +++ b/drivers/firmware/efi/libstub/tpm.c @@ -0,0 +1,58 @@ +/* + * TPM handling. + * + * Copyright (C) 2016 CoreOS, Inc + * Copyright (C) 2017 Google, Inc. + * Matthew Garrett <mjg59@google.com> + * + * This file is part of the Linux kernel, and is made available under the + * terms of the GNU General Public License version 2. + */ +#include <linux/efi.h> +#include <asm/efi.h> + +#include "efistub.h" + +static const efi_char16_t efi_MemoryOverWriteRequest_name[] = { + 'M', 'e', 'm', 'o', 'r', 'y', 'O', 'v', 'e', 'r', 'w', 'r', 'i', 't', + 'e', 'R', 'e', 'q', 'u', 'e', 's', 't', 'C', 'o', 'n', 't', 'r', 'o', + 'l', 0 +}; + +#define MEMORY_ONLY_RESET_CONTROL_GUID \ + EFI_GUID(0xe20939be, 0x32d4, 0x41be, 0xa1, 0x50, 0x89, 0x7f, 0x85, 0xd4, 0x98, 0x29) + +#define get_efi_var(name, vendor, ...) \ + efi_call_runtime(get_variable, \ + (efi_char16_t *)(name), (efi_guid_t *)(vendor), \ + __VA_ARGS__) + +#define set_efi_var(name, vendor, ...) \ + efi_call_runtime(set_variable, \ + (efi_char16_t *)(name), (efi_guid_t *)(vendor), \ + __VA_ARGS__) + +/* + * Enable reboot attack mitigation. This requests that the firmware clear the + * RAM on next reboot before proceeding with boot, ensuring that any secrets + * are cleared. If userland has ensured that all secrets have been removed + * from RAM before reboot it can simply reset this variable. + */ +void efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg) +{ + u8 val = 1; + efi_guid_t var_guid = MEMORY_ONLY_RESET_CONTROL_GUID; + efi_status_t status; + unsigned long datasize = 0; + + status = get_efi_var(efi_MemoryOverWriteRequest_name, &var_guid, + NULL, &datasize, NULL); + + if (status == EFI_NOT_FOUND) + return; + + set_efi_var(efi_MemoryOverWriteRequest_name, &var_guid, + EFI_VARIABLE_NON_VOLATILE | + EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val); +} diff --git a/include/linux/efi.h b/include/linux/efi.h index 4e47f78430be..c241acca0b15 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1504,6 +1504,13 @@ enum efi_secureboot_mode { }; enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table); +#ifdef CONFIG_RESET_ATTACK_MITIGATION +void efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg); +#else +static inline void +efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg) { } +#endif + /* * Arch code can implement the following three template macros, avoiding * reptition for the void/non-void return cases of {__,}efi_call_virt(): |