efi_loader: efi_tcg2_register returns appropriate error

This commit modify efi_tcg2_register() to return the
appropriate error.
With this fix, sandbox will not boot because efi_tcg2_register()
fails due to some missing feature in GetCapabilities.
So disable sandbox if EFI_TCG2_PROTOCOL is enabled.

UEFI secure boot variable measurement is not directly related
to TCG2 protocol installation, tcg2_measure_secure_boot_variable()
is moved to the separate function.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

include/efi_loader.h

@@ -525,6 +525,8 @@ efi_status_t efi_disk_register(void);
 efi_status_t efi_rng_register(void);
 /* Called by efi_init_obj_list() to install EFI_TCG2_PROTOCOL */
 efi_status_t efi_tcg2_register(void);
+/* Called by efi_init_obj_list() to do initial measurement */
+efi_status_t efi_tcg2_do_initial_measurement(void);
 /* measure the pe-coff image, extend PCR and add Event Log */
 efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
 				   struct efi_loaded_image_obj *handle,

lib/efi_loader/Kconfig

@@ -308,6 +308,8 @@ config EFI_TCG2_PROTOCOL
 	bool "EFI_TCG2_PROTOCOL support"
 	default y
 	depends on TPM_V2
+	# Sandbox TPM currently fails on GetCapabilities needed for TCG2
+	depends on !SANDBOX
 	select SHA1
 	select SHA256
 	select SHA384

lib/efi_loader/efi_setup.c

@@ -241,6 +241,10 @@ efi_status_t efi_init_obj_list(void)
 		ret = efi_tcg2_register();
 		if (ret != EFI_SUCCESS)
 			goto out;
+
+		ret = efi_tcg2_do_initial_measurement();
+		if (ret == EFI_SECURITY_VIOLATION)
+			goto out;
 	}
 
 	/* Secure boot */

lib/efi_loader/efi_tcg2.c

@@ -153,6 +153,15 @@ static u16 alg_to_len(u16 hash_alg)
 	return 0;
 }
 
+static bool is_tcg2_protocol_installed(void)
+{
+	struct efi_handler *handler;
+	efi_status_t ret;
+
+	ret = efi_search_protocol(efi_root, &efi_guid_tcg2_protocol, &handler);
+	return ret == EFI_SUCCESS;
+}
+
 static u32 tcg_event_final_size(struct tpml_digest_values *digest_list)
 {
 	u32 len;
@@ -1664,6 +1673,14 @@ void tcg2_uninit(void)
 	event_log.buffer = NULL;
 	efi_free_pool(event_log.final_buffer);
 	event_log.final_buffer = NULL;
+
+	if (!is_tcg2_protocol_installed())
+		return;
+
+	ret = efi_remove_protocol(efi_root, &efi_guid_tcg2_protocol,
+				  (void *)&efi_tcg2_protocol);
+	if (ret != EFI_SUCCESS)
+		log_err("Failed to remove EFI TCG2 protocol\n");
 }
 
 /**
@@ -2345,12 +2362,37 @@ error:
 	return ret;
 }
 
+/**
+ * efi_tcg2_do_initial_measurement() - do initial measurement
+ *
+ * Return:	status code
+ */
+efi_status_t efi_tcg2_do_initial_measurement(void)
+{
+	efi_status_t ret;
+	struct udevice *dev;
+
+	if (!is_tcg2_protocol_installed())
+		return EFI_SUCCESS;
+
+	ret = platform_get_tpm2_device(&dev);
+	if (ret != EFI_SUCCESS)
+		return EFI_SECURITY_VIOLATION;
+
+	ret = tcg2_measure_secure_boot_variable(dev);
+	if (ret != EFI_SUCCESS)
+		goto out;
+
+out:
+	return ret;
+}
+
 /**
  * efi_tcg2_register() - register EFI_TCG2_PROTOCOL
  *
  * If a TPM2 device is available, the TPM TCG2 Protocol is registered
  *
- * Return:	An error status is only returned if adding the protocol fails.
+ * Return:	status code
  */
 efi_status_t efi_tcg2_register(void)
 {
@@ -2373,8 +2415,10 @@ efi_status_t efi_tcg2_register(void)
 	}
 
 	ret = efi_init_event_log();
-	if (ret != EFI_SUCCESS)
+	if (ret != EFI_SUCCESS) {
+		tcg2_uninit();
 		goto fail;
+	}
 
 	ret = efi_add_protocol(efi_root, &efi_guid_tcg2_protocol,
 			       (void *)&efi_tcg2_protocol);
@@ -2391,24 +2435,9 @@ efi_status_t efi_tcg2_register(void)
 		goto fail;
 	}
 
-	ret = tcg2_measure_secure_boot_variable(dev);
-	if (ret != EFI_SUCCESS) {
-		tcg2_uninit();
-		goto fail;
-	}
-
 	return ret;
 
 fail:
 	log_err("Cannot install EFI_TCG2_PROTOCOL\n");
-	/*
+	return ret;
-	 * Return EFI_SUCCESS and don't stop the EFI subsystem.
-	 * That's done for 2 reasons
-	 * - If the protocol is not installed the PCRs won't be extended.  So
-	 *   someone later in the boot flow will notice that and take the
-	 *   necessary actions.
-	 * - The TPM sandbox is limited and we won't be able to run any efi
-	 *   related tests with TCG2 enabled
-	 */
-	return EFI_SUCCESS;
 }