diff mbox series

[UNSTABLE,1/2] UBUNTU: SAUCE: integrity: Load mokx certs from the EFI MOK config table

Message ID 20210517131848.61153-2-dimitri.ledkov@canonical.com
State New
Headers show
Series Support importing mokx keys into revocation list from the mok table | expand

Commit Message

Dimitri John Ledkov May 17, 2021, 1:18 p.m. UTC 
Refactor load_moklist_certs() to load either MokListRT into db, or
MokListXRT into dbx. Call load_moklist_certs() twice - first to load
mokx certs into dbx, then mok certs into db.

This thus now attempts to load mokx certs via the EFI MOKvar config
table first, and if that fails, via the EFI variable. Previously mokx
certs were only loaded via the EFI variable. Which fails when
MokListXRT is large. Instead of large MokListXRT variable, only
MokListXRT{1,2,3} are available which are not loaded. This is the case
with Ubuntu's 15.4 based shim. This patch is required to address
CVE-2020-26541 when certificates are revoked via MokListXRT.

Fixes: ebd9c2ae369a ("integrity: Load mokx variables into the blacklist keyring")

BugLink: https://bugs.launchpad.net/bugs/1928679
Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
---
 security/integrity/platform_certs/load_uefi.c | 74 ++++++++++---------
 1 file changed, 40 insertions(+), 34 deletions(-)

Comments

Krzysztof Kozlowski May 17, 2021, 1:41 p.m. UTC | #1 
On 17/05/2021 09:18, Dimitri John Ledkov wrote:
> Refactor load_moklist_certs() to load either MokListRT into db, or
> MokListXRT into dbx. Call load_moklist_certs() twice - first to load
> mokx certs into dbx, then mok certs into db.
> 
> This thus now attempts to load mokx certs via the EFI MOKvar config
> table first, and if that fails, via the EFI variable. Previously mokx
> certs were only loaded via the EFI variable. Which fails when
> MokListXRT is large. Instead of large MokListXRT variable, only
> MokListXRT{1,2,3} are available which are not loaded. This is the case
> with Ubuntu's 15.4 based shim. This patch is required to address
> CVE-2020-26541 when certificates are revoked via MokListXRT.
> 
> Fixes: ebd9c2ae369a ("integrity: Load mokx variables into the blacklist keyring")

No blank line between tags.

> 
> BugLink: https://bugs.launchpad.net/bugs/1928679
> Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
> ---
>  security/integrity/platform_certs/load_uefi.c | 74 ++++++++++---------
>  1 file changed, 40 insertions(+), 34 deletions(-)

LGTM, but I cannot judge the context of this patch, so I would propose
to wait for upstream comments.

Best regards,
Krzysztof
Dimitri John Ledkov May 17, 2021, 2:58 p.m. UTC | #2 
On Mon, May 17, 2021 at 2:41 PM Krzysztof Kozlowski
<krzysztof.kozlowski@canonical.com> wrote:
>
> On 17/05/2021 09:18, Dimitri John Ledkov wrote:
> > Refactor load_moklist_certs() to load either MokListRT into db, or
> > MokListXRT into dbx. Call load_moklist_certs() twice - first to load
> > mokx certs into dbx, then mok certs into db.
> >
> > This thus now attempts to load mokx certs via the EFI MOKvar config
> > table first, and if that fails, via the EFI variable. Previously mokx
> > certs were only loaded via the EFI variable. Which fails when
> > MokListXRT is large. Instead of large MokListXRT variable, only
> > MokListXRT{1,2,3} are available which are not loaded. This is the case
> > with Ubuntu's 15.4 based shim. This patch is required to address
> > CVE-2020-26541 when certificates are revoked via MokListXRT.
> >
> > Fixes: ebd9c2ae369a ("integrity: Load mokx variables into the blacklist keyring")
>
> No blank line between tags.
>
> >
> > BugLink: https://bugs.launchpad.net/bugs/1928679
> > Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
> > ---
> >  security/integrity/platform_certs/load_uefi.c | 74 ++++++++++---------
> >  1 file changed, 40 insertions(+), 34 deletions(-)
>
> LGTM, but I cannot judge the context of this patch, so I would propose
> to wait for upstream comments.
>
> Best regards,
> Krzysztof

We must not sign v5.13 based kernels until this patch is in.
Otherwise, the claim that v5.13 is enough to fix CVE-2020-26541 will
not hold true for Ubuntu. And if one does stable backports of
CVE-2020-26541 which are forthcoming, they will be insufficient on
Ubuntu.

I don't know how to mark this as a blocking issue for unstable-5.13
upload into impish.
diff mbox series

Patch

diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c
index d3e7ae04f5be..b010b4ab5d52 100644
--- a/security/integrity/platform_certs/load_uefi.c
+++ b/security/integrity/platform_certs/load_uefi.c
@@ -68,17 +68,18 @@  static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
 }
 
 /*
- * load_moklist_certs() - Load MokList certs
+ * load_moklist_certs() - Load Mok(X)List certs
+ * @load_db: Load MokListRT into db when true; MokListXRT into dbx when false
  *
- * Load the certs contained in the UEFI MokListRT database into the
- * platform trusted keyring.
+ * Load the certs contained in the UEFI MokList(X)RT database into the
+ * platform trusted/denied keyring.
  *
  * This routine checks the EFI MOK config table first. If and only if
- * that fails, this routine uses the MokListRT ordinary UEFI variable.
+ * that fails, this routine uses the MokList(X)RT ordinary UEFI variable.
  *
  * Return:	Status
  */
-static int __init load_moklist_certs(void)
+static int __init load_moklist_certs(const bool load_db)
 {
 	struct efi_mokvar_table_entry *mokvar_entry;
 	efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
@@ -86,41 +87,55 @@  static int __init load_moklist_certs(void)
 	unsigned long moksize;
 	efi_status_t status;
 	int rc;
+	const char *mokvar_name = "MokListRT";
+	/* Should be const, but get_cert_list() doesn't have it as const yet */
+	efi_char16_t *efivar_name = L"MokListRT";
+	const char *parse_mokvar_name = "UEFI:MokListRT (MOKvar table)";
+	const char *parse_efivar_name = "UEFI:MokListRT";
+	efi_element_handler_t (*get_handler_for_guid)(const efi_guid_t *) = get_handler_for_db;
+
+	if (!load_db) {
+		mokvar_name = "MokListXRT";
+		efivar_name = L"MokListXRT";
+		parse_mokvar_name = "UEFI:MokListXRT (MOKvar table)";
+		parse_efivar_name = "UEFI:MokListXRT";
+		get_handler_for_guid = get_handler_for_dbx;
+	}
 
 	/* First try to load certs from the EFI MOKvar config table.
 	 * It's not an error if the MOKvar config table doesn't exist
 	 * or the MokListRT entry is not found in it.
 	 */
-	mokvar_entry = efi_mokvar_entry_find("MokListRT");
+	mokvar_entry = efi_mokvar_entry_find(mokvar_name);
 	if (mokvar_entry) {
-		rc = parse_efi_signature_list("UEFI:MokListRT (MOKvar table)",
+		rc = parse_efi_signature_list(parse_mokvar_name,
 					      mokvar_entry->data,
 					      mokvar_entry->data_size,
-					      get_handler_for_db);
+					      get_handler_for_guid);
 		/* All done if that worked. */
 		if (!rc)
 			return rc;
 
-		pr_err("Couldn't parse MokListRT signatures from EFI MOKvar config table: %d\n",
-		       rc);
+		pr_err("Couldn't parse %s signatures from EFI MOKvar config table: %d\n",
+		       mokvar_name, rc);
 	}
 
 	/* Get MokListRT. It might not exist, so it isn't an error
 	 * if we can't get it.
 	 */
-	mok = get_cert_list(L"MokListRT", &mok_var, &moksize, &status);
+	mok = get_cert_list(efivar_name, &mok_var, &moksize, &status);
 	if (mok) {
-		rc = parse_efi_signature_list("UEFI:MokListRT",
-					      mok, moksize, get_handler_for_db);
+		rc = parse_efi_signature_list(parse_efivar_name,
+					      mok, moksize, get_handler_for_guid);
 		kfree(mok);
 		if (rc)
-			pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
+			pr_err("Couldn't parse %s signatures: %d\n", mokvar_name, rc);
 		return rc;
 	}
 	if (status == EFI_NOT_FOUND)
-		pr_debug("MokListRT variable wasn't found\n");
+		pr_debug("%s variable wasn't found\n", mokvar_name);
 	else
-		pr_info("Couldn't get UEFI MokListRT\n");
+		pr_info("Couldn't get UEFI %s\n", mokvar_name);
 	return 0;
 }
 
@@ -134,9 +149,8 @@  static int __init load_moklist_certs(void)
 static int __init load_uefi_certs(void)
 {
 	efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
-	efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
-	void *db = NULL, *dbx = NULL, *mokx = NULL;
-	unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0;
+	void *db = NULL, *dbx = NULL;
+	unsigned long dbsize = 0, dbxsize = 0;
 	efi_status_t status;
 	int rc = 0;
 
@@ -178,23 +192,15 @@  static int __init load_uefi_certs(void)
 		kfree(dbx);
 	}
 
-	mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status);
-	if (!mokx) {
-		if (status == EFI_NOT_FOUND)
-			pr_debug("mokx variable wasn't found\n");
-		else
-			pr_info("Couldn't get mokx list\n");
-	} else {
-		rc = parse_efi_signature_list("UEFI:MokListXRT",
-					      mokx, mokxsize,
-					      get_handler_for_dbx);
-		if (rc)
-			pr_err("Couldn't parse mokx signatures %d\n", rc);
-		kfree(mokx);
-	}
+	/* Load the MokListXRT certs */
+	rc = load_moklist_certs(false);
+	if (rc)
+		pr_err("Couldn't parse mokx signatures: %d\n", rc);
 
 	/* Load the MokListRT certs */
-	rc = load_moklist_certs();
+	rc = load_moklist_certs(true);
+	if (rc)
+		pr_err("Couldn't parse mok signatures: %d\n", rc);
 
 	return rc;
 }