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) <p...@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) {
--
2.29.2
