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x86/ima: define arch_get_ima_policy() for x86 

On x86, there are two methods of verifying a kexec'ed kernel image
signature being loaded via the kexec_file_load syscall - an architecture
specific implementaton or a IMA KEXEC_KERNEL_CHECK appraisal rule. Neither
of these methods verify the kexec'ed kernel image signature being loaded
via the kexec_load syscall.

Secure boot enabled systems require kexec images to be signed. Therefore,
this patch loads an IMA KEXEC_KERNEL_CHECK policy rule on secure boot
enabled systems not configured with CONFIG_KEXEC_VERIFY_SIG enabled.

When IMA_APPRAISE_BOOTPARAM is configured, different IMA appraise modes
(eg. fix, log) can be specified on the boot command line, allowing unsigned
or invalidly signed kernel images to be kexec'ed. This patch permits
enabling IMA_APPRAISE_BOOTPARAM or IMA_ARCH_POLICY, but not both.

Signed-off-by: Eric Richter <erichte@linux.ibm.com>
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Peter Jones <pjones@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Eric Richter 2018-10-09 23:00:37 +05:30 committed by Mimi Zohar
parent 6191706246
commit d958083a8f
3 changed files with 27 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
arch/x86/kernel/ima_arch.c
View File

@ -15,3 +15,19 @@ bool arch_ima_get_secureboot(void)
else
return false;
}
/* secureboot arch rules */
static const char * const sb_arch_rules[] = {
#if !IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG)
"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 (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot())
return sb_arch_rules;
return NULL;
}

3
include/linux/ima.h
View File

@ -32,17 +32,18 @@ extern void ima_add_kexec_buffer(struct kimage *image);
#ifdef CONFIG_X86
extern bool arch_ima_get_secureboot(void);
extern const char * const *arch_get_ima_policy(void);
#else
static inline bool arch_ima_get_secureboot(void)
{
return false;
}
#endif
static inline const char * const *arch_get_ima_policy(void)
{
return NULL;
}
#endif
#else
static inline int ima_bprm_check(struct linux_binprm *bprm)

10
security/integrity/ima/Kconfig
View File

@ -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 KEXEC_VERIFY_SIG || 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
@ -217,7 +225,7 @@ config IMA_APPRAISE_REQUIRE_POLICY_SIGS
config IMA_APPRAISE_BOOTPARAM
bool "ima_appraise boot parameter"
depends on IMA_APPRAISE
depends on IMA_APPRAISE && !IMA_ARCH_POLICY
default y
help
This option enables the different "ima_appraise=" modes