linux-apfs/Documentation/ABI/testing/ima_policy

What:		security/ima/policy
Date:		May 2008
Contact:	Mimi Zohar <zohar@us.ibm.com>
Description:
		The Trusted Computing Group(TCG) runtime Integrity
		Measurement Architecture(IMA) maintains a list of hash
		values of executables and other sensitive system files
		loaded into the run-time of this system.  At runtime,
		the policy can be constrained based on LSM specific data.
		Policies are loaded into the securityfs file ima/policy
		by opening the file, writing the rules one at a time and
		then closing the file.  The new policy takes effect after
		the file ima/policy is closed.

		IMA appraisal, if configured, uses these file measurements
		for local measurement appraisal.

		rule format: action [condition ...]

		action: measure | dont_measure | appraise | dont_appraise | audit
		condition:= base | lsm
			base:	[[func=] [mask=] [fsmagic=] [uid=] [fowner]]
			lsm:	[[subj_user=] [subj_role=] [subj_type=]
				 [obj_user=] [obj_role=] [obj_type=]]

		base: 	func:= [BPRM_CHECK][FILE_MMAP][FILE_CHECK][MODULE_CHECK]
			mask:= [MAY_READ] [MAY_WRITE] [MAY_APPEND] [MAY_EXEC]
			fsmagic:= hex value
			uid:= decimal value
			fowner:=decimal value
		lsm:  	are LSM specific

		default policy:
			# PROC_SUPER_MAGIC
			dont_measure fsmagic=0x9fa0
			dont_appraise fsmagic=0x9fa0
			# SYSFS_MAGIC
			dont_measure fsmagic=0x62656572
			dont_appraise fsmagic=0x62656572
			# DEBUGFS_MAGIC
			dont_measure fsmagic=0x64626720
			dont_appraise fsmagic=0x64626720
			# TMPFS_MAGIC
			dont_measure fsmagic=0x01021994
			dont_appraise fsmagic=0x01021994
			# RAMFS_MAGIC
			dont_measure fsmagic=0x858458f6
			dont_appraise fsmagic=0x858458f6
			# SECURITYFS_MAGIC
			dont_measure fsmagic=0x73636673
			dont_appraise fsmagic=0x73636673

			measure func=BPRM_CHECK
			measure func=FILE_MMAP mask=MAY_EXEC
			measure func=FILE_CHECK mask=MAY_READ uid=0
			measure func=MODULE_CHECK uid=0
			appraise fowner=0

		The default policy measures all executables in bprm_check,
		all files mmapped executable in file_mmap, and all files
		open for read by root in do_filp_open.  The default appraisal
		policy appraises all files owned by root.

		Examples of LSM specific definitions:

		SELinux:
			# SELINUX_MAGIC
			dont_measure fsmagic=0xf97cff8c
			dont_appraise fsmagic=0xf97cff8c

			dont_measure obj_type=var_log_t
			dont_appraise obj_type=var_log_t
			dont_measure obj_type=auditd_log_t
			dont_appraise obj_type=auditd_log_t
			measure subj_user=system_u func=FILE_CHECK mask=MAY_READ
			measure subj_role=system_r func=FILE_CHECK mask=MAY_READ

		Smack:
			measure subj_user=_ func=FILE_CHECK mask=MAY_READ