Commit 8db5da0b authored by Mimi Zohar's avatar Mimi Zohar
Browse files

x86/ima: require signed kernel modules 



Have the IMA architecture specific policy require signed kernel modules
on systems with secure boot mode enabled; and coordinate the different
signature verification methods, so only one signature is required.

Requiring appended kernel module signatures may be configured, enabled
on the boot command line, or with this patch enabled in secure boot
mode.  This patch defines set_module_sig_enforced().

To coordinate between appended kernel module signatures and IMA
signatures, only define an IMA MODULE_CHECK policy rule if
CONFIG_MODULE_SIG is not enabled.  A custom IMA policy may still define
and require an IMA signature.

Signed-off-by: default avatarMimi Zohar <zohar@linux.ibm.com>
Reviewed-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Acked-by: default avatarJessica Yu <jeyu@kernel.org>
parent 8d93e952

arch/x86/kernel/ima_arch.c

+8 −1
Original line number Diff line number Diff line
@@ -64,12 +64,19 @@ static const char * const sb_arch_rules[] = { 
	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig",

#endif /* CONFIG_KEXEC_VERIFY_SIG */

	"measure func=KEXEC_KERNEL_CHECK",

#if !IS_ENABLED(CONFIG_MODULE_SIG)

	"appraise func=MODULE_CHECK appraise_type=imasig",

#endif

	"measure func=MODULE_CHECK",

	NULL

};



const char * const *arch_get_ima_policy(void)

{

	if (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot())

	if (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot()) {

		if (IS_ENABLED(CONFIG_MODULE_SIG))

			set_module_sig_enforced();

		return sb_arch_rules;

	}

	return NULL;

}

include/linux/module.h

+5 −0
Original line number Diff line number Diff line
@@ -676,6 +676,7 @@ static inline bool is_livepatch_module(struct module *mod) 
#endif /* CONFIG_LIVEPATCH */



bool is_module_sig_enforced(void);

void set_module_sig_enforced(void);



#else /* !CONFIG_MODULES... */
@@ -796,6 +797,10 @@ static inline bool is_module_sig_enforced(void) 
	return false;

}



static inline void set_module_sig_enforced(void)

{

}



/* Dereference module function descriptor */

static inline

void *dereference_module_function_descriptor(struct module *mod, void *ptr)

kernel/module.c

+5 −0
Original line number Diff line number Diff line
@@ -286,6 +286,11 @@ bool is_module_sig_enforced(void) 
}

EXPORT_SYMBOL(is_module_sig_enforced);



void set_module_sig_enforced(void)

{

	sig_enforce = true;

}



/* Block module loading/unloading? */

int modules_disabled = 0;

core_param(nomodule, modules_disabled, bint, 0);

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