linux-kernel - [PATCH 1/5] MODSIGN: do not load mok when secure boot disabled

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Date:   Tue, 13 Mar 2018 18:35:55 +0800
From:   "Lee, Chun-Yi" <jlee@...e.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-fs@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/5] MODSIGN: do not load mok when secure boot disabled

The mok can not be trusted when the secure boot is disabled. Which
means that the kernel embedded certificate is the only trusted key.

Due to db/dbx are authenticated variables, they needs manufacturer's
KEK for update. So db/dbx are secure when secureboot disabled.

Cc: David Howells <dhowells@...hat.com>
Cc: Josh Boyer <jwboyer@...oraproject.org>
Cc: James Bottomley <James.Bottomley@...senPartnership.com>
Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
---
 certs/load_uefi.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/certs/load_uefi.c b/certs/load_uefi.c
index 3d88459..d6de4d0 100644
--- a/certs/load_uefi.c
+++ b/certs/load_uefi.c
@@ -164,17 +164,6 @@ static int __init load_uefi_certs(void)
 		}
 	}
 
-	mok = get_cert_list(L"MokListRT", &mok_var, &moksize);
-	if (!mok) {
-		pr_info("MODSIGN: Couldn't get UEFI MokListRT\n");
-	} else {
-		rc = parse_efi_signature_list("UEFI:MokListRT",
-					      mok, moksize, get_handler_for_db);
-		if (rc)
-			pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
-		kfree(mok);
-	}
-
 	dbx = get_cert_list(L"dbx", &secure_var, &dbxsize);
 	if (!dbx) {
 		pr_info("MODSIGN: Couldn't get UEFI dbx list\n");
@@ -187,6 +176,21 @@ static int __init load_uefi_certs(void)
 		kfree(dbx);
 	}
 
+	/* the MOK can not be trusted when secure boot is disabled */
+	if (!efi_enabled(EFI_SECURE_BOOT))
+		return 0;
+
+	mok = get_cert_list(L"MokListRT", &mok_var, &moksize);
+	if (!mok) {
+		pr_info("MODSIGN: Couldn't get UEFI MokListRT\n");
+	} else {
+		rc = parse_efi_signature_list("UEFI:MokListRT",
+					      mok, moksize, get_handler_for_db);
+		if (rc)
+			pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
+		kfree(mok);
+	}
+
 	return rc;
 }
 late_initcall(load_uefi_certs);
-- 
2.10.2