This patch implements an example arch-specific IMA policy for x86 to enable measurement and appraisal of any kernel images loaded for kexec, and disables the kexec_load syscall.
To avoid conflicting with the existing CONFIG_KERNEL_VERIFY_SIG option, the policy only "appraises" the target image on kexec_load. Without this, the target kexec image would have to be verified by both the above option as well as by IMA appraisal. Since signature verification for kexec_load is not possible via appraisal (or VERIFY_SIG), this results in a failure and thus effectively prevents the kexec_load syscall from succeeding when set. Signed-off-by: Eric Richter <eric...@linux.vnet.ibm.com> --- arch/x86/kernel/Makefile | 2 ++ arch/x86/kernel/ima_arch.c | 27 +++++++++++++++++++++++++++ include/linux/ima.h | 8 ++++++++ security/integrity/ima/Kconfig | 8 ++++++++ 4 files changed, 45 insertions(+) create mode 100644 arch/x86/kernel/ima_arch.c diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 02d6f5cf4e7..f3e1d76ed9b 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -149,3 +149,5 @@ ifeq ($(CONFIG_X86_64),y) obj-$(CONFIG_MMCONF_FAM10H) += mmconf-fam10h_64.o obj-y += vsmp_64.o endif + +obj-$(CONFIG_IMA_ARCH_POLICY) += ima_arch.o diff --git a/arch/x86/kernel/ima_arch.c b/arch/x86/kernel/ima_arch.c new file mode 100644 index 00000000000..5eb10e29db0 --- /dev/null +++ b/arch/x86/kernel/ima_arch.c @@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Copyright (C) 2018 IBM Corporation + */ +#include <linux/efi.h> +#include <linux/ima.h> + +extern struct boot_params boot_params; + +/* arch rules for audit and user mode */ +static const char * const sb_arch_rules[] = { +#ifdef CONFIG_KEXEC_VERIFY_SIG + "appraise func=KEXEC_ORIG_KERNEL_CHECK appraise_type=imasig", +#else + "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig", +#endif /* CONFIG_KEXEC_VERIFY_SIG */ + "measure func=KEXEC_KERNEL_CHECK", + NULL +}; + +const char * const *arch_get_ima_policy(void) +{ + if (efi_enabled(EFI_BOOT) && + (boot_params.secure_boot == efi_secureboot_mode_enabled)) + return sb_arch_rules; + return NULL; +} diff --git a/include/linux/ima.h b/include/linux/ima.h index 7fd272f0b1f..495fa290b14 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -30,10 +30,14 @@ extern void ima_post_path_mknod(struct dentry *dentry); extern void ima_add_kexec_buffer(struct kimage *image); #endif +#if defined(CONFIG_IMA_ARCH_POLICY) && defined(CONFIG_X86) +extern const char * const *arch_get_ima_policy(void); +#else static inline const char * const *arch_get_ima_policy(void) { return NULL; } +#endif #else static inline int ima_bprm_check(struct linux_binprm *bprm) @@ -77,6 +81,10 @@ static inline void ima_post_path_mknod(struct dentry *dentry) return; } +static inline const char * const *arch_get_ima_policy(void) +{ + return NULL; +} #endif /* CONFIG_IMA */ #ifndef CONFIG_IMA_KEXEC diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig index 13b446328dd..18de132bbda 100644 --- a/security/integrity/ima/Kconfig +++ b/security/integrity/ima/Kconfig @@ -157,6 +157,14 @@ config IMA_APPRAISE <http://linux-ima.sourceforge.net> If unsure, say N. +config IMA_ARCH_POLICY + bool "Enable loading an IMA architecture specific policy" + depends on IMA_APPRAISE && INTEGRITY_ASYMMETRIC_KEYS + default n + help + This option enables loading an IMA architecture specific policy + based on run time secure boot flags. + config IMA_APPRAISE_BUILD_POLICY bool "IMA build time configured policy rules" depends on IMA_APPRAISE && INTEGRITY_ASYMMETRIC_KEYS -- 2.14.4 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html