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From 9f1958a0cc911e1f79b2733ee5029dbd819ff328 Mon Sep 17 00:00:00 2001
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From: Josh Boyer <jwboyer@fedoraproject.org>
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Date: Fri, 5 May 2017 08:21:59 +0100
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Subject: [PATCH 4/4] MODSIGN: Allow the "db" UEFI variable to be suppressed
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If a user tells shim to not use the certs/hashes in the UEFI db variable
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for verification purposes, shim will set a UEFI variable called
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MokIgnoreDB.  Have the uefi import code look for this and ignore the db
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variable if it is found.
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Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
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Signed-off-by: David Howells <dhowells@redhat.com>
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---
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 certs/load_uefi.c | 44 ++++++++++++++++++++++++++++++++++----------
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 1 file changed, 34 insertions(+), 10 deletions(-)
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diff --git a/certs/load_uefi.c b/certs/load_uefi.c
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index b44e464..3d88459 100644
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--- a/certs/load_uefi.c
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+++ b/certs/load_uefi.c
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@@ -13,6 +13,26 @@ static __initdata efi_guid_t efi_cert_x509_sha256_guid = EFI_CERT_X509_SHA256_GU
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 static __initdata efi_guid_t efi_cert_sha256_guid = EFI_CERT_SHA256_GUID;
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 /*
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+ * Look to see if a UEFI variable called MokIgnoreDB exists and return true if
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+ * it does.
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+ *
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+ * This UEFI variable is set by the shim if a user tells the shim to not use
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+ * the certs/hashes in the UEFI db variable for verification purposes.  If it
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+ * is set, we should ignore the db variable also and the true return indicates
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+ * this.
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+ */
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+static __init bool uefi_check_ignore_db(void)
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+{
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+	efi_status_t status;
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+	unsigned int db = 0;
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+	unsigned long size = sizeof(db);
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+	efi_guid_t guid = EFI_SHIM_LOCK_GUID;
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+
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+	status = efi.get_variable(L"MokIgnoreDB", &guid, NULL, &size, &db);
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+	return status == EFI_SUCCESS;
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+}
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+
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+/*
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  * Get a certificate list blob from the named EFI variable.
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  */
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 static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
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@@ -113,7 +133,9 @@ static __init efi_element_handler_t get_handler_for_dbx(const efi_guid_t *sig_ty
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 }
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 /*
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- * Load the certs contained in the UEFI databases
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+ * Load the certs contained in the UEFI databases into the secondary trusted
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+ * keyring and the UEFI blacklisted X.509 cert SHA256 hashes into the blacklist
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+ * keyring.
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  */
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 static int __init load_uefi_certs(void)
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 {
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@@ -129,15 +151,17 @@ static int __init load_uefi_certs(void)
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 	/* Get db, MokListRT, and dbx.  They might not exist, so it isn't
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 	 * an error if we can't get them.
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 	 */
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-	db = get_cert_list(L"db", &secure_var, &dbsize);
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-	if (!db) {
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-		pr_err("MODSIGN: Couldn't get UEFI db list\n");
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-	} else {
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-		rc = parse_efi_signature_list("UEFI:db",
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-					      db, dbsize, get_handler_for_db);
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-		if (rc)
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-			pr_err("Couldn't parse db signatures: %d\n", rc);
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-		kfree(db);
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+	if (!uefi_check_ignore_db()) {
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+		db = get_cert_list(L"db", &secure_var, &dbsize);
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+		if (!db) {
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+			pr_err("MODSIGN: Couldn't get UEFI db list\n");
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+		} else {
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+			rc = parse_efi_signature_list("UEFI:db",
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+						      db, dbsize, get_handler_for_db);
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+			if (rc)
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+				pr_err("Couldn't parse db signatures: %d\n", rc);
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+			kfree(db);
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+		}
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 	}
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 	mok = get_cert_list(L"MokListRT", &mok_var, &moksize);
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-- 
ea38f2
2.9.3
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