[PATCH v3 4/4] powerpc: load firmware trusted keys/hashes into kernel keyring

Nayna Jain
2019-08-26T13:24:21Z

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>
---
security/integrity/Kconfig | 8 ++
security/integrity/Makefile | 3 +
.../integrity/platform_certs/load_powerpc.c | 88 +++++++++++++++++++
3 files changed, 99 insertions(+)
create mode 100644 security/integrity/platform_certs/load_powerpc.c

diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
index 0bae6adb63a9..26abee23e4e3 100644
--- a/security/integrity/Kconfig
+++ b/security/integrity/Kconfig
@@ -72,6 +72,14 @@ 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
+ 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
diff --git a/security/integrity/Makefile b/security/integrity/Makefile
index 525bf1d6e0db..9eeb6b053de3 100644
--- a/security/integrity/Makefile
+++ b/security/integrity/Makefile
@@ -14,6 +14,9 @@ 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)/load_uefi.o: KBUILD_CFLAGS += -fshort-wchar

subdir-$(CONFIG_IMA) += ima
diff --git a/security/integrity/platform_certs/load_powerpc.c b/security/integrity/platform_certs/load_powerpc.c
new file mode 100644
index 000000000000..359d5063d4da
--- /dev/null
+++ b/security/integrity/platform_certs/load_powerpc.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain <nayna@linux.ibm.com>
+ *
+ * - 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 <asm/secboot.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 db var: %d\n", 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;
+
+ if (!secvar_ops)
+ 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", 3, &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);
+ }
+
+ return rc;
+}
+late_initcall(load_powerpc_certs);
--
2.20.1