1What:		/sys/kernel/security/*/ima/policy
2Date:		May 2008
3Contact:	Mimi Zohar <zohar@us.ibm.com>
4Description:
5		The Trusted Computing Group(TCG) runtime Integrity
6		Measurement Architecture(IMA) maintains a list of hash
7		values of executables and other sensitive system files
8		loaded into the run-time of this system.  At runtime,
9		the policy can be constrained based on LSM specific data.
10		Policies are loaded into the securityfs file ima/policy
11		by opening the file, writing the rules one at a time and
12		then closing the file.  The new policy takes effect after
13		the file ima/policy is closed.
14
15		IMA appraisal, if configured, uses these file measurements
16		for local measurement appraisal.
17
18		::
19
20		  rule format: action [condition ...]
21
22		  action: measure | dont_measure | appraise | dont_appraise |
23			  audit | hash | dont_hash
24		  condition:= base | lsm  [option]
25			base:	[[func=] [mask=] [fsmagic=] [fsuuid=] [fsname=]
26				[uid=] [euid=] [gid=] [egid=]
27				[fowner=] [fgroup=]]
28			lsm:	[[subj_user=] [subj_role=] [subj_type=]
29				 [obj_user=] [obj_role=] [obj_type=]]
30			option:	[[appraise_type=]] [template=] [permit_directio]
31				[appraise_flag=] [appraise_algos=] [keyrings=]
32		  base:
33			func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
34				[FIRMWARE_CHECK]
35				[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
36				[KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA]
37				[SETXATTR_CHECK]
38			mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
39			       [[^]MAY_EXEC]
40			fsmagic:= hex value
41			fsuuid:= file system UUID (e.g 8bcbe394-4f13-4144-be8e-5aa9ea2ce2f6)
42			uid:= decimal value
43			euid:= decimal value
44			gid:= decimal value
45			egid:= decimal value
46			fowner:= decimal value
47			fgroup:= decimal value
48		  lsm:  are LSM specific
49		  option:
50			appraise_type:= [imasig] [imasig|modsig]
51			appraise_flag:= [check_blacklist]
52			Currently, blacklist check is only for files signed with appended
53			signature.
54			keyrings:= list of keyrings
55			(eg, .builtin_trusted_keys|.ima). Only valid
56			when action is "measure" and func is KEY_CHECK.
57			template:= name of a defined IMA template type
58			(eg, ima-ng). Only valid when action is "measure".
59			pcr:= decimal value
60			label:= [selinux]|[kernel_info]|[data_label]
61			data_label:= a unique string used for grouping and limiting critical data.
62			For example, "selinux" to measure critical data for SELinux.
63			appraise_algos:= comma-separated list of hash algorithms
64			For example, "sha256,sha512" to only accept to appraise
65			files where the security.ima xattr was hashed with one
66			of these two algorithms.
67
68		  default policy:
69			# PROC_SUPER_MAGIC
70			dont_measure fsmagic=0x9fa0
71			dont_appraise fsmagic=0x9fa0
72			# SYSFS_MAGIC
73			dont_measure fsmagic=0x62656572
74			dont_appraise fsmagic=0x62656572
75			# DEBUGFS_MAGIC
76			dont_measure fsmagic=0x64626720
77			dont_appraise fsmagic=0x64626720
78			# TMPFS_MAGIC
79			dont_measure fsmagic=0x01021994
80			dont_appraise fsmagic=0x01021994
81			# RAMFS_MAGIC
82			dont_appraise fsmagic=0x858458f6
83			# DEVPTS_SUPER_MAGIC
84			dont_measure fsmagic=0x1cd1
85			dont_appraise fsmagic=0x1cd1
86			# BINFMTFS_MAGIC
87			dont_measure fsmagic=0x42494e4d
88			dont_appraise fsmagic=0x42494e4d
89			# SECURITYFS_MAGIC
90			dont_measure fsmagic=0x73636673
91			dont_appraise fsmagic=0x73636673
92			# SELINUX_MAGIC
93			dont_measure fsmagic=0xf97cff8c
94			dont_appraise fsmagic=0xf97cff8c
95			# CGROUP_SUPER_MAGIC
96			dont_measure fsmagic=0x27e0eb
97			dont_appraise fsmagic=0x27e0eb
98			# NSFS_MAGIC
99			dont_measure fsmagic=0x6e736673
100			dont_appraise fsmagic=0x6e736673
101
102			measure func=BPRM_CHECK
103			measure func=FILE_MMAP mask=MAY_EXEC
104			measure func=FILE_CHECK mask=MAY_READ uid=0
105			measure func=MODULE_CHECK
106			measure func=FIRMWARE_CHECK
107			appraise fowner=0
108
109		The default policy measures all executables in bprm_check,
110		all files mmapped executable in file_mmap, and all files
111		open for read by root in do_filp_open.  The default appraisal
112		policy appraises all files owned by root.
113
114		Examples of LSM specific definitions:
115
116		SELinux::
117
118			dont_measure obj_type=var_log_t
119			dont_appraise obj_type=var_log_t
120			dont_measure obj_type=auditd_log_t
121			dont_appraise obj_type=auditd_log_t
122			measure subj_user=system_u func=FILE_CHECK mask=MAY_READ
123			measure subj_role=system_r func=FILE_CHECK mask=MAY_READ
124
125		Smack::
126
127			measure subj_user=_ func=FILE_CHECK mask=MAY_READ
128
129		Example of measure rules using alternate PCRs::
130
131			measure func=KEXEC_KERNEL_CHECK pcr=4
132			measure func=KEXEC_INITRAMFS_CHECK pcr=5
133
134		Example of appraise rule allowing modsig appended signatures:
135
136			appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig
137
138		Example of measure rule using KEY_CHECK to measure all keys:
139
140			measure func=KEY_CHECK
141
142		Example of measure rule using KEY_CHECK to only measure
143		keys added to .builtin_trusted_keys or .ima keyring:
144
145			measure func=KEY_CHECK keyrings=.builtin_trusted_keys|.ima
146
147		Example of the special SETXATTR_CHECK appraise rule, that
148		restricts the hash algorithms allowed when writing to the
149		security.ima xattr of a file:
150
151			appraise func=SETXATTR_CHECK appraise_algos=sha256,sha384,sha512
152