Introduce a new config option CONFIG_EFI_SECURE_BOOT_VAR_DISABLE to allow disabling EFI secure boot when the platform is operating in User Mode and there is an NV+BS EFI variable called "SecureBootDisable". Otherwise, keep it enabled by default.
Signed-off-by: Paulo Alcantara (SUSE) pc@cjr.nz --- lib/efi_loader/Kconfig | 13 +++++++++ lib/efi_loader/efi_var_common.c | 48 ++++++++++++++++++++++++++++++++- 2 files changed, 60 insertions(+), 1 deletion(-)
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig index 29ea14b2ee2a..d453905c7666 100644 --- a/lib/efi_loader/Kconfig +++ b/lib/efi_loader/Kconfig @@ -224,5 +224,18 @@ config EFI_SECURE_BOOT Once SecureBoot mode is enforced, any EFI binary can run only if it is signed with a trusted key. To do that, you need to install, at least, PK, KEK and db. + Note that SecureBoot mode may no longer be enforced when + EFI_SECURE_BOOT_VAR_DISABLE option is enabled. + +config EFI_SECURE_BOOT_VAR_DISABLE + bool "Permit to disable EFI secure boot when in User Mode" + depends on EFI_SECURE_BOOT + default n + help + Select this option to allow disabling EFI secure boot when + the platform is operating in User Mode (e.g. PK is enrolled) + and there is an NV+BS EFI variable called + "SecureBootDisable". A platform reset is also required to + actually disable it.
endif diff --git a/lib/efi_loader/efi_var_common.c b/lib/efi_loader/efi_var_common.c index 1c7459266a38..89aa944180a4 100644 --- a/lib/efi_loader/efi_var_common.c +++ b/lib/efi_loader/efi_var_common.c @@ -241,6 +241,48 @@ err: return ret; }
+ +#ifdef CONFIG_EFI_SECURE_BOOT_VAR_DISABLE +/** + * efi_secure_boot_in_user_mode - check if secure boot enabled in User Mode + * + * @enabled: true if enabled, false if disabled + * + * Return: status code + */ +static efi_status_t efi_secure_boot_in_user_mode(u8 *enabled) +{ + efi_status_t ret; + efi_uintn_t size = 0; + u32 attributes; + u32 mask = EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS; + + ret = efi_get_variable_int(L"SecureBootDisable", + &efi_global_variable_guid, + &attributes, &size, NULL, NULL); + if (ret == EFI_BUFFER_TOO_SMALL) { + if (attributes ^ mask) { + log_err("Unable to disable secure boot. Required attributes for SecureBootDisable variable: NV+BS\n"); + *enabled = 1; + } else { + EFI_PRINT("Disabling secure boot due to existing SecureBootDisable variable\n"); + *enabled = 0; + } + ret = EFI_SUCCESS; + } else if (ret == EFI_NOT_FOUND) { + *enabled = 1; + ret = EFI_SUCCESS; + } + return ret; +} +#else +static efi_status_t efi_secure_boot_in_user_mode(u8 *enabled) +{ + *enabled = 1; + return EFI_SUCCESS; +} +#endif + /** * efi_transfer_secure_state - handle a secure boot state transition * @mode: new state @@ -274,7 +316,11 @@ static efi_status_t efi_transfer_secure_state(enum efi_secure_mode mode) if (ret != EFI_SUCCESS) goto err; } else if (mode == EFI_MODE_USER) { - ret = efi_set_secure_state(1, 0, 0, 0); + u8 secure_boot; + ret = efi_secure_boot_in_user_mode(&secure_boot); + if (ret != EFI_SUCCESS) + goto err; + ret = efi_set_secure_state(secure_boot, 0, 0, 0); if (ret != EFI_SUCCESS) goto err; } else if (mode == EFI_MODE_SETUP) {