powerpc: Load firmware trusted keys/hashes into kernel keyring

The keys used to verify the Host OS kernel are managed by firmware as
secure variables. This patch loads the verification keys into the
.platform keyring and revocation hashes into .blacklist keyring. This
enables verification and loading of the kernels signed by the boot
time keys which are trusted by firmware.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Eric Richter <erichte@linux.ibm.com>
[mpe: Search by compatible in load_powerpc_certs(), not using format]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1573441836-3632-5-git-send-email-nayna@linux.ibm.com

security/integrity/Kconfig

@@ -72,6 +72,15 @@ config LOAD_IPL_KEYS
        depends on S390
        def_bool y
 
+config LOAD_PPC_KEYS
+	bool "Enable loading of platform and blacklisted keys for POWER"
+	depends on INTEGRITY_PLATFORM_KEYRING
+	depends on PPC_SECURE_BOOT
+	default y
+	help
+	  Enable loading of keys to the .platform keyring and blacklisted
+	  hashes to the .blacklist keyring for powerpc based platforms.
+
 config INTEGRITY_AUDIT
 	bool "Enables integrity auditing support "
 	depends on AUDIT

security/integrity/Makefile

@@ -14,6 +14,8 @@ integrity-$(CONFIG_LOAD_UEFI_KEYS) += platform_certs/efi_parser.o \
 				      platform_certs/load_uefi.o \
 				      platform_certs/keyring_handler.o
 integrity-$(CONFIG_LOAD_IPL_KEYS) += platform_certs/load_ipl_s390.o
-
+integrity-$(CONFIG_LOAD_PPC_KEYS) += platform_certs/efi_parser.o \
+                                     platform_certs/load_powerpc.o \
+                                     platform_certs/keyring_handler.o
 obj-$(CONFIG_IMA)			+= ima/
 obj-$(CONFIG_EVM)			+= evm/

security/integrity/platform_certs/load_powerpc.c

@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain
+ *
+ *      - loads keys and hashes stored and controlled by the firmware.
+ */
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/cred.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <asm/secure_boot.h>
+#include <asm/secvar.h>
+#include "keyring_handler.h"
+
+/*
+ * Get a certificate list blob from the named secure variable.
+ */
+static __init void *get_cert_list(u8 *key, unsigned long keylen, uint64_t *size)
+{
+	int rc;
+	void *db;
+
+	rc = secvar_ops->get(key, keylen, NULL, size);
+	if (rc) {
+		pr_err("Couldn't get size: %d\n", rc);
+		return NULL;
+	}
+
+	db = kmalloc(*size, GFP_KERNEL);
+	if (!db)
+		return NULL;
+
+	rc = secvar_ops->get(key, keylen, db, size);
+	if (rc) {
+		kfree(db);
+		pr_err("Error reading %s var: %d\n", key, rc);
+		return NULL;
+	}
+
+	return db;
+}
+
+/*
+ * Load the certs contained in the keys databases into the platform trusted
+ * keyring and the blacklisted X.509 cert SHA256 hashes into the blacklist
+ * keyring.
+ */
+static int __init load_powerpc_certs(void)
+{
+	void *db = NULL, *dbx = NULL;
+	uint64_t dbsize = 0, dbxsize = 0;
+	int rc = 0;
+	struct device_node *node;
+
+	if (!secvar_ops)
+		return -ENODEV;
+
+	/* The following only applies for the edk2-compat backend. */
+	node = of_find_compatible_node(NULL, NULL, "ibm,edk2-compat-v1");
+	if (!node)
+		return -ENODEV;
+
+	/*
+	 * Get db, and dbx. They might not exist, so it isn't an error if we
+	 * can't get them.
+	 */
+	db = get_cert_list("db", 3, &dbsize);
+	if (!db) {
+		pr_err("Couldn't get db list from firmware\n");
+	} else {
+		rc = parse_efi_signature_list("powerpc: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("dbx", 4,  &dbxsize);
+	if (!dbx) {
+		pr_info("Couldn't get dbx list from firmware\n");
+	} else {
+		rc = parse_efi_signature_list("powerpc:dbx", dbx, dbxsize,
+					      get_handler_for_dbx);
+		if (rc)
+			pr_err("Couldn't parse dbx signatures: %d\n", rc);
+		kfree(dbx);
+	}
+
+	of_node_put(node);
+
+	return rc;
+}
+late_initcall(load_powerpc_certs);