efi_loader: variable: add secure boot state transition

UEFI specification defines several global variables which are related to
the current secure boot state. In this commit, those values will be
maintained according to operations. Currently, AuditMode and DeployedMode
are defined but not implemented.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>

1 files changed, 228 insertions, 3 deletions

diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
index adb7847..fd5c41f 100644
--- a/lib/efi_loader/efi_variable.c
+++ b/lib/efi_loader/efi_variable.c
@@ -16,8 +16,16 @@
 #include <u-boot/crc.h>
 #include "../lib/crypto/pkcs7_parser.h"
 
+enum efi_secure_mode {
+	EFI_MODE_SETUP,
+	EFI_MODE_USER,
+	EFI_MODE_AUDIT,
+	EFI_MODE_DEPLOYED,
+};
+
 const efi_guid_t efi_guid_cert_type_pkcs7 = EFI_CERT_TYPE_PKCS7_GUID;
 static bool efi_secure_boot;
+static int efi_secure_mode;
 
 #define READ_ONLY BIT(31)
 
@@ -160,6 +168,210 @@ static const char *parse_attr(const char *str, u32 *attrp, u64 *timep)
 	return str;
 }
 
+static efi_status_t efi_set_variable_internal(u16 *variable_name,
+					      const efi_guid_t *vendor,
+					      u32 attributes,
+					      efi_uintn_t data_size,
+					      const void *data,
+					      bool ro_check);
+
+/**
+ * efi_transfer_secure_state - handle a secure boot state transition
+ * @mode:	new state
+ *
+ * Depending on @mode, secure boot related variables are updated.
+ * Those variables are *read-only* for users, efi_set_variable_internal()
+ * is called here.
+ *
+ * Return:	EFI_SUCCESS on success, status code (negative) on error
+ */
+static efi_status_t efi_transfer_secure_state(enum efi_secure_mode mode)
+{
+	u32 attributes;
+	u8 val;
+	efi_status_t ret;
+
+	debug("Secure state from %d to %d\n", efi_secure_mode, mode);
+
+	attributes = EFI_VARIABLE_BOOTSERVICE_ACCESS |
+		     EFI_VARIABLE_RUNTIME_ACCESS;
+	if (mode == EFI_MODE_DEPLOYED) {
+		val = 1;
+		ret = efi_set_variable_internal(L"SecureBoot",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 0;
+		ret = efi_set_variable_internal(L"SetupMode",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 0;
+		ret = efi_set_variable_internal(L"AuditMode",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 1;
+		ret = efi_set_variable_internal(L"DeployedMode",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+
+		efi_secure_boot = true;
+	} else if (mode == EFI_MODE_AUDIT) {
+		ret = efi_set_variable_internal(L"PK",
+						&efi_global_variable_guid,
+						attributes,
+						0, NULL,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 0;
+		ret = efi_set_variable_internal(L"SecureBoot",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 1;
+		ret = efi_set_variable_internal(L"SetupMode",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 1;
+		ret = efi_set_variable_internal(L"AuditMode",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 0;
+		ret = efi_set_variable_internal(L"DeployedMode",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+
+		efi_secure_boot = true;
+	} else if (mode == EFI_MODE_USER) {
+		val = 1;
+		ret = efi_set_variable_internal(L"SecureBoot",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 0;
+		ret = efi_set_variable_internal(L"SetupMode",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 0;
+		ret = efi_set_variable_internal(L"AuditMode",
+						&efi_global_variable_guid,
+						attributes,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 0;
+		ret = efi_set_variable_internal(L"DeployedMode",
+						&efi_global_variable_guid,
+						attributes,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+
+		efi_secure_boot = true;
+	} else if (mode == EFI_MODE_SETUP) {
+		val = 0;
+		ret = efi_set_variable_internal(L"SecureBoot",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 1;
+		ret = efi_set_variable_internal(L"SetupMode",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 0;
+		ret = efi_set_variable_internal(L"AuditMode",
+						&efi_global_variable_guid,
+						attributes,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+		val = 0;
+		ret = efi_set_variable_internal(L"DeployedMode",
+						&efi_global_variable_guid,
+						attributes | READ_ONLY,
+						sizeof(val), &val,
+						false);
+		if (ret != EFI_SUCCESS)
+			goto err;
+	} else {
+		return EFI_INVALID_PARAMETER;
+	}
+
+	return EFI_SUCCESS;
+
+err:
+	/* TODO: What action should be taken here? */
+	printf("ERROR: Secure state transition failed\n");
+	return ret;
+}
+
+/**
+ * efi_init_secure_state - initialize secure boot state
+ *
+ * Return:	EFI_SUCCESS on success, status code (negative) on error
+ */
+static efi_status_t efi_init_secure_state(void)
+{
+	efi_uintn_t size = 0;
+	efi_status_t ret;
+
+	ret = EFI_CALL(efi_get_variable(L"PK", &efi_global_variable_guid,
+					NULL, &size, NULL));
+	if (ret == EFI_BUFFER_TOO_SMALL && IS_ENABLED(CONFIG_EFI_SECURE_BOOT))
+		ret = efi_transfer_secure_state(EFI_MODE_USER);
+	else
+		ret = efi_transfer_secure_state(EFI_MODE_SETUP);
+
+	return ret;
+}
+
 /**
  * efi_secure_boot_enabled - return if secure boot is enabled or not
  *
@@ -910,10 +1122,19 @@ efi_status_t EFIAPI efi_set_variable_common(u16 *variable_name,
 	EFI_PRINT("setting: %s=%s\n", native_name, val);
 
 out:
-	if (env_set(native_name, val))
+	if (env_set(native_name, val)) {
 		ret = EFI_DEVICE_ERROR;
-	else
+	} else {
+		if ((u16_strcmp(variable_name, L"PK") == 0 &&
+		     guidcmp(vendor, &efi_global_variable_guid) == 0)) {
+			ret = efi_transfer_secure_state(
+					(delete ? EFI_MODE_SETUP :
+						  EFI_MODE_USER));
+			if (ret != EFI_SUCCESS)
+				goto err;
+		}
 		ret = EFI_SUCCESS;
+	}
 
 err:
 	free(native_name);
@@ -1098,5 +1319,9 @@ void efi_variables_boot_exit_notify(void)
  */
 efi_status_t efi_init_variables(void)
 {
-	return EFI_SUCCESS;
+	efi_status_t ret;
+
+	ret = efi_init_secure_state();
+
+	return ret;
 }