1 files changed, 238 insertions, 0 deletions
diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c
new file mode 100644
index 000000000..d1fdd1134
--- /dev/null
+++ b/security/integrity/platform_certs/load_uefi.c
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/cred.h>
+#include <linux/dmi.h>
+#include <linux/err.h>
+#include <linux/efi.h>
+#include <linux/slab.h>
+#include <linux/ima.h>
+#include <keys/asymmetric-type.h>
+#include <keys/system_keyring.h>
+#include "../integrity.h"
+#include "keyring_handler.h"
+
+/*
+ * On T2 Macs reading the db and dbx efi variables to load UEFI Secure Boot
+ * certificates causes occurrence of a page fault in Apple's firmware and
+ * a crash disabling EFI runtime services. The following quirk skips reading
+ * these variables.
+ */
+static const struct dmi_system_id uefi_skip_cert[] = {
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,1") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,2") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,3") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,4") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,1") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,2") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,3") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,4") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,1") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,2") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir9,1") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "Macmini8,1") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacPro7,1") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,1") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,2") },
+	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMacPro1,1") },
+	{ }
+};
+
+/*
+ * Look to see if a UEFI variable called MokIgnoreDB exists and return true if
+ * it does.
+ *
+ * This UEFI variable is set by the shim if a user tells the shim to not use
+ * the certs/hashes in the UEFI db variable for verification purposes.  If it
+ * is set, we should ignore the db variable also and the true return indicates
+ * this.
+ */
+static __init bool uefi_check_ignore_db(void)
+{
+	efi_status_t status;
+	unsigned int db = 0;
+	unsigned long size = sizeof(db);
+	efi_guid_t guid = EFI_SHIM_LOCK_GUID;
+
+	status = efi.get_variable(L"MokIgnoreDB", &guid, NULL, &size, &db);
+	return status == EFI_SUCCESS;
+}
+
+/*
+ * Get a certificate list blob from the named EFI variable.
+ */
+static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
+				  unsigned long *size, efi_status_t *status)
+{
+	unsigned long lsize = 4;
+	unsigned long tmpdb[4];
+	void *db;
+
+	*status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb);
+	if (*status == EFI_NOT_FOUND)
+		return NULL;
+
+	if (*status != EFI_BUFFER_TOO_SMALL) {
+		pr_err("Couldn't get size: 0x%lx\n", *status);
+		return NULL;
+	}
+
+	db = kmalloc(lsize, GFP_KERNEL);
+	if (!db)
+		return NULL;
+
+	*status = efi.get_variable(name, guid, NULL, &lsize, db);
+	if (*status != EFI_SUCCESS) {
+		kfree(db);
+		pr_err("Error reading db var: 0x%lx\n", *status);
+		return NULL;
+	}
+
+	*size = lsize;
+	return db;
+}
+
+/*
+ * load_moklist_certs() - Load MokList certs
+ *
+ * Load the certs contained in the UEFI MokListRT database into the
+ * platform trusted keyring.
+ *
+ * This routine checks the EFI MOK config table first. If and only if
+ * that fails, this routine uses the MokListRT ordinary UEFI variable.
+ *
+ * Return:	Status
+ */
+static int __init load_moklist_certs(void)
+{
+	struct efi_mokvar_table_entry *mokvar_entry;
+	efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
+	void *mok;
+	unsigned long moksize;
+	efi_status_t status;
+	int rc;
+
+	/* 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");
+	if (mokvar_entry) {
+		rc = parse_efi_signature_list("UEFI:MokListRT (MOKvar table)",
+					      mokvar_entry->data,
+					      mokvar_entry->data_size,
+					      get_handler_for_mok);
+		/* All done if that worked. */
+		if (!rc)
+			return rc;
+
+		pr_err("Couldn't parse MokListRT signatures from EFI MOKvar config table: %d\n",
+		       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);
+	if (mok) {
+		rc = parse_efi_signature_list("UEFI:MokListRT",
+					      mok, moksize, get_handler_for_mok);
+		kfree(mok);
+		if (rc)
+			pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
+		return rc;
+	}
+	if (status == EFI_NOT_FOUND)
+		pr_debug("MokListRT variable wasn't found\n");
+	else
+		pr_info("Couldn't get UEFI MokListRT\n");
+	return 0;
+}
+
+/*
+ * load_uefi_certs() - Load certs from UEFI sources
+ *
+ * Load the certs contained in the UEFI databases into the platform trusted
+ * keyring and the UEFI blacklisted X.509 cert SHA256 hashes into the blacklist
+ * keyring.
+ */
+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;
+	efi_status_t status;
+	int rc = 0;
+	const struct dmi_system_id *dmi_id;
+
+	dmi_id = dmi_first_match(uefi_skip_cert);
+	if (dmi_id) {
+		pr_err("Reading UEFI Secure Boot Certs is not supported on T2 Macs.\n");
+		return false;
+	}
+
+	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
+		return false;
+
+	/* Get db and dbx.  They might not exist, so it isn't an error
+	 * if we can't get them.
+	 */
+	if (!uefi_check_ignore_db()) {
+		db = get_cert_list(L"db", &secure_var, &dbsize, &status);
+		if (!db) {
+			if (status == EFI_NOT_FOUND)
+				pr_debug("MODSIGN: db variable wasn't found\n");
+			else
+				pr_err("MODSIGN: Couldn't get UEFI db list\n");
+		} else {
+			rc = parse_efi_signature_list("UEFI:db",
+					db, dbsize, get_handler_for_db);
+			if (rc)
+				pr_err("Couldn't parse db signatures: %d\n",
+				       rc);
+			kfree(db);
+		}
+	}
+
+	dbx = get_cert_list(L"dbx", &secure_var, &dbxsize, &status);
+	if (!dbx) {
+		if (status == EFI_NOT_FOUND)
+			pr_debug("dbx variable wasn't found\n");
+		else
+			pr_info("Couldn't get UEFI dbx list\n");
+	} else {
+		rc = parse_efi_signature_list("UEFI:dbx",
+					      dbx, dbxsize,
+					      get_handler_for_dbx);
+		if (rc)
+			pr_err("Couldn't parse dbx signatures: %d\n", rc);
+		kfree(dbx);
+	}
+
+	/* the MOK/MOKx can not be trusted when secure boot is disabled */
+	if (!arch_ima_get_secureboot())
+		return 0;
+
+	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 MokListRT certs */
+	rc = load_moklist_certs();
+
+	return rc;
+}
+late_initcall(load_uefi_certs);