openpower/linux/0003-powerpc-ima-Add-support-to-initialize-ima-policy-rul.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Nayna Jain <nayna@linux.ibm.com>
Date: Wed, 30 Oct 2019 23:31:27 -0400
Subject: [PATCH 03/18] powerpc/ima: Add support to initialize ima policy rules

PowerNV systems use a Linux-based bootloader, which rely on the IMA
subsystem to enforce different secure boot modes. Since the
verification policy may differ based on the secure boot mode of the
system, the policies must be defined at runtime.

This patch implements arch-specific support to define IMA policy rules
based on the runtime secure boot mode of the system.

This patch provides arch-specific IMA policies if PPC_SECURE_BOOT
config is enabled.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1572492694-6520-3-git-send-email-zohar@linux.ibm.com
(cherry picked from commit 4238fad366a660cbc6499ca1ea4be42bd4d1ac5b)
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
 arch/powerpc/Kconfig           |  1 +
 arch/powerpc/kernel/Makefile   |  2 +-
 arch/powerpc/kernel/ima_arch.c | 43 ++++++++++++++++++++++++++++++++++
 include/linux/ima.h            |  3 ++-
 4 files changed, 47 insertions(+), 2 deletions(-)
 create mode 100644 arch/powerpc/kernel/ima_arch.c

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index bdf584b85199..eea6c358b86c 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -938,6 +938,7 @@ config PPC_SECURE_BOOT
 	prompt "Enable secure boot support"
 	bool
 	depends on PPC_POWERNV
+	depends on IMA_ARCH_POLICY
 	help
 	  Systems with firmware secure boot enabled need to define security
 	  policies to extend secure boot to the OS. This config allows a user
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 40170ee52178..b82f7f5e5121 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -158,7 +158,7 @@ ifneq ($(CONFIG_PPC_POWERNV)$(CONFIG_PPC_SVM),)
 obj-y				+= ucall.o
 endif
 
-obj-$(CONFIG_PPC_SECURE_BOOT)	+= secure_boot.o
+obj-$(CONFIG_PPC_SECURE_BOOT)	+= secure_boot.o ima_arch.o
 
 # Disable GCOV, KCOV & sanitizers in odd or sensitive code
 GCOV_PROFILE_prom_init.o := n
diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c
new file mode 100644
index 000000000000..d88913dc0da7
--- /dev/null
+++ b/arch/powerpc/kernel/ima_arch.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain
+ */
+
+#include <linux/ima.h>
+#include <asm/secure_boot.h>
+
+bool arch_ima_get_secureboot(void)
+{
+	return is_ppc_secureboot_enabled();
+}
+
+/*
+ * The "secure_rules" are enabled only on "secureboot" enabled systems.
+ * These rules verify the file signatures against known good values.
+ * The "appraise_type=imasig|modsig" option allows the known good signature
+ * to be stored as an xattr or as an appended signature.
+ *
+ * To avoid duplicate signature verification as much as possible, the IMA
+ * policy rule for module appraisal is added only if CONFIG_MODULE_SIG_FORCE
+ * is not enabled.
+ */
+static const char *const secure_rules[] = {
+	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
+#ifndef CONFIG_MODULE_SIG_FORCE
+	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
+#endif
+	NULL
+};
+
+/*
+ * Returns the relevant IMA arch-specific policies based on the system secure
+ * boot state.
+ */
+const char *const *arch_get_ima_policy(void)
+{
+	if (is_ppc_secureboot_enabled())
+		return secure_rules;
+
+	return NULL;
+}
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 1c37f17f7203..6d904754d858 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -29,7 +29,8 @@ extern void ima_kexec_cmdline(const void *buf, int size);
 extern void ima_add_kexec_buffer(struct kimage *image);
 #endif
 
-#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390)
+#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390) \
+	|| defined(CONFIG_PPC_SECURE_BOOT)
 extern bool arch_ima_get_secureboot(void);
 extern const char * const *arch_get_ima_policy(void);
 #else