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Commit 503ceaef authored by Mimi Zohar's avatar Mimi Zohar
Browse files

ima: define a set of appraisal rules requiring file signatures 



The builtin "ima_appraise_tcb" policy should require file signatures for
at least a few of the hooks (eg. kernel modules, firmware, and the kexec
kernel image), but changing it would break the existing userspace/kernel
ABI.

This patch defines a new builtin policy named "secure_boot", which
can be specified on the "ima_policy=" boot command line, independently
or in conjunction with the "ima_appraise_tcb" policy, by specifing
ima_policy="appraise_tcb | secure_boot".  The new appraisal rules
requiring file signatures will be added prior to the "ima_appraise_tcb"
rules.

Signed-off-by: default avatarMimi Zohar <zohar@linux.vnet.ibm.com>

Changelog:
- Reference secure boot in the new builtin policy name. (Thiago Bauermann)
parent 33ce9549

Documentation/admin-guide/kernel-parameters.txt

+5 −1
Original line number Diff line number Diff line
@@ -1478,7 +1478,7 @@ 


	ima_policy=	[IMA]

			The builtin policies to load during IMA setup.

			Format: "tcb | appraise_tcb"

			Format: "tcb | appraise_tcb | secure_boot"



			The "tcb" policy measures all programs exec'd, files

			mmap'd for exec, and all files opened with the read
@@ -1489,6 +1489,10 @@ 
			all files owned by root. (This is the equivalent

			of ima_appraise_tcb.)



			The "secure_boot" policy appraises the integrity

			of files (eg. kexec kernel image, kernel modules,

			firmware, policy, etc) based on file signatures.



	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.

			Load a policy which meets the needs of the Trusted

			Computing Base.  This means IMA will measure all

security/integrity/ima/ima_policy.c

+25 −1
Original line number Diff line number Diff line
@@ -153,6 +153,17 @@ static struct ima_rule_entry default_appraise_rules[] __ro_after_init = { 
#endif

};



static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {

	{.action = APPRAISE, .func = MODULE_CHECK,

	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},

	{.action = APPRAISE, .func = FIRMWARE_CHECK,

	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},

	{.action = APPRAISE, .func = KEXEC_KERNEL_CHECK,

	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},

	{.action = APPRAISE, .func = POLICY_CHECK,

	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},

};



static LIST_HEAD(ima_default_rules);

static LIST_HEAD(ima_policy_rules);

static LIST_HEAD(ima_temp_rules);
@@ -171,6 +182,7 @@ static int __init default_measure_policy_setup(char *str) 
__setup("ima_tcb", default_measure_policy_setup);



static bool ima_use_appraise_tcb __initdata;

static bool ima_use_secure_boot __initdata;

static int __init policy_setup(char *str)

{

	char *p;
@@ -182,6 +194,8 @@ static int __init policy_setup(char *str) 
			ima_policy = DEFAULT_TCB;

		else if (strcmp(p, "appraise_tcb") == 0)

			ima_use_appraise_tcb = 1;

		else if (strcmp(p, "secure_boot") == 0)

			ima_use_secure_boot = 1;

	}



	return 1;
@@ -410,12 +424,14 @@ void ima_update_policy_flag(void) 
 */

void __init ima_init_policy(void)

{

	int i, measure_entries, appraise_entries;

	int i, measure_entries, appraise_entries, secure_boot_entries;



	/* if !ima_policy set entries = 0 so we load NO default rules */

	measure_entries = ima_policy ? ARRAY_SIZE(dont_measure_rules) : 0;

	appraise_entries = ima_use_appraise_tcb ?

			 ARRAY_SIZE(default_appraise_rules) : 0;

	secure_boot_entries = ima_use_secure_boot ?

			ARRAY_SIZE(secure_boot_rules) : 0;



	for (i = 0; i < measure_entries; i++)

		list_add_tail(&dont_measure_rules[i].list, &ima_default_rules);
@@ -434,6 +450,14 @@ void __init ima_init_policy(void) 
		break;

	}



	/*

	 * Insert the appraise rules requiring file signatures, prior to

	 * any other appraise rules.

	 */

	for (i = 0; i < secure_boot_entries; i++)

		list_add_tail(&secure_boot_rules[i].list,

			      &ima_default_rules);



	for (i = 0; i < appraise_entries; i++) {

		list_add_tail(&default_appraise_rules[i].list,

			      &ima_default_rules);