191 lines
6.3 KiB
Plaintext
191 lines
6.3 KiB
Plaintext
|
What: /sys/kernel/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 | hash | dont_hash
|
||
|
|
condition:= base | lsm [option]
|
||
|
|
base: [[func=] [mask=] [fsmagic=] [fsuuid=] [fsname=]
|
||
|
|
[uid=] [euid=] [gid=] [egid=]
|
||
|
|
[fowner=] [fgroup=]]
|
||
|
|
lsm: [[subj_user=] [subj_role=] [subj_type=]
|
||
|
|
[obj_user=] [obj_role=] [obj_type=]]
|
||
|
|
option: [digest_type=] [template=] [permit_directio]
|
||
|
|
[appraise_type=] [appraise_flag=]
|
||
|
|
[appraise_algos=] [keyrings=]
|
||
|
|
base:
|
||
|
|
func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
|
||
|
|
[FIRMWARE_CHECK]
|
||
|
|
[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
|
||
|
|
[KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA]
|
||
|
|
[SETXATTR_CHECK][MMAP_CHECK_REQPROT]
|
||
|
|
mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
|
||
|
|
[[^]MAY_EXEC]
|
||
|
|
fsmagic:= hex value
|
||
|
|
fsuuid:= file system UUID (e.g 8bcbe394-4f13-4144-be8e-5aa9ea2ce2f6)
|
||
|
|
uid:= decimal value
|
||
|
|
euid:= decimal value
|
||
|
|
gid:= decimal value
|
||
|
|
egid:= decimal value
|
||
|
|
fowner:= decimal value
|
||
|
|
fgroup:= decimal value
|
||
|
|
lsm: are LSM specific
|
||
|
|
option:
|
||
|
|
appraise_type:= [imasig] | [imasig|modsig] | [sigv3]
|
||
|
|
where 'imasig' is the original or the signature
|
||
|
|
format v2.
|
||
|
|
where 'modsig' is an appended signature,
|
||
|
|
where 'sigv3' is the signature format v3. (Currently
|
||
|
|
limited to fsverity digest based signatures
|
||
|
|
stored in security.ima xattr. Requires
|
||
|
|
specifying "digest_type=verity" first.)
|
||
|
|
|
||
|
|
appraise_flag:= [check_blacklist]
|
||
|
|
Currently, blacklist check is only for files signed with appended
|
||
|
|
signature.
|
||
|
|
digest_type:= verity
|
||
|
|
Require fs-verity's file digest instead of the
|
||
|
|
regular IMA file hash.
|
||
|
|
keyrings:= list of keyrings
|
||
|
|
(eg, .builtin_trusted_keys|.ima). Only valid
|
||
|
|
when action is "measure" and func is KEY_CHECK.
|
||
|
|
template:= name of a defined IMA template type
|
||
|
|
(eg, ima-ng). Only valid when action is "measure".
|
||
|
|
pcr:= decimal value
|
||
|
|
label:= [selinux]|[kernel_info]|[data_label]
|
||
|
|
data_label:= a unique string used for grouping and limiting critical data.
|
||
|
|
For example, "selinux" to measure critical data for SELinux.
|
||
|
|
appraise_algos:= comma-separated list of hash algorithms
|
||
|
|
For example, "sha256,sha512" to only accept to appraise
|
||
|
|
files where the security.ima xattr was hashed with one
|
||
|
|
of these two algorithms.
|
||
|
|
|
||
|
|
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_appraise fsmagic=0x858458f6
|
||
|
|
# DEVPTS_SUPER_MAGIC
|
||
|
|
dont_measure fsmagic=0x1cd1
|
||
|
|
dont_appraise fsmagic=0x1cd1
|
||
|
|
# BINFMTFS_MAGIC
|
||
|
|
dont_measure fsmagic=0x42494e4d
|
||
|
|
dont_appraise fsmagic=0x42494e4d
|
||
|
|
# SECURITYFS_MAGIC
|
||
|
|
dont_measure fsmagic=0x73636673
|
||
|
|
dont_appraise fsmagic=0x73636673
|
||
|
|
# SELINUX_MAGIC
|
||
|
|
dont_measure fsmagic=0xf97cff8c
|
||
|
|
dont_appraise fsmagic=0xf97cff8c
|
||
|
|
# CGROUP_SUPER_MAGIC
|
||
|
|
dont_measure fsmagic=0x27e0eb
|
||
|
|
dont_appraise fsmagic=0x27e0eb
|
||
|
|
# NSFS_MAGIC
|
||
|
|
dont_measure fsmagic=0x6e736673
|
||
|
|
dont_appraise fsmagic=0x6e736673
|
||
|
|
|
||
|
|
measure func=BPRM_CHECK
|
||
|
|
measure func=FILE_MMAP mask=MAY_EXEC
|
||
|
|
measure func=FILE_CHECK mask=MAY_READ uid=0
|
||
|
|
measure func=MODULE_CHECK
|
||
|
|
measure func=FIRMWARE_CHECK
|
||
|
|
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::
|
||
|
|
|
||
|
|
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
|
||
|
|
|
||
|
|
Example of measure rules using alternate PCRs::
|
||
|
|
|
||
|
|
measure func=KEXEC_KERNEL_CHECK pcr=4
|
||
|
|
measure func=KEXEC_INITRAMFS_CHECK pcr=5
|
||
|
|
|
||
|
|
Example of appraise rule allowing modsig appended signatures:
|
||
|
|
|
||
|
|
appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig
|
||
|
|
|
||
|
|
Example of measure rule using KEY_CHECK to measure all keys:
|
||
|
|
|
||
|
|
measure func=KEY_CHECK
|
||
|
|
|
||
|
|
Example of measure rule using KEY_CHECK to only measure
|
||
|
|
keys added to .builtin_trusted_keys or .ima keyring:
|
||
|
|
|
||
|
|
measure func=KEY_CHECK keyrings=.builtin_trusted_keys|.ima
|
||
|
|
|
||
|
|
Example of the special SETXATTR_CHECK appraise rule, that
|
||
|
|
restricts the hash algorithms allowed when writing to the
|
||
|
|
security.ima xattr of a file:
|
||
|
|
|
||
|
|
appraise func=SETXATTR_CHECK appraise_algos=sha256,sha384,sha512
|
||
|
|
|
||
|
|
Example of a 'measure' rule requiring fs-verity's digests
|
||
|
|
with indication of type of digest in the measurement list.
|
||
|
|
|
||
|
|
measure func=FILE_CHECK digest_type=verity \
|
||
|
|
template=ima-ngv2
|
||
|
|
|
||
|
|
Example of 'measure' and 'appraise' rules requiring fs-verity
|
||
|
|
signatures (format version 3) stored in security.ima xattr.
|
||
|
|
|
||
|
|
The 'measure' rule specifies the 'ima-sigv3' template option,
|
||
|
|
which includes the indication of type of digest and the file
|
||
|
|
signature in the measurement list.
|
||
|
|
|
||
|
|
measure func=BPRM_CHECK digest_type=verity \
|
||
|
|
template=ima-sigv3
|
||
|
|
|
||
|
|
|
||
|
|
The 'appraise' rule specifies the type and signature format
|
||
|
|
version (sigv3) required.
|
||
|
|
|
||
|
|
appraise func=BPRM_CHECK digest_type=verity \
|
||
|
|
appraise_type=sigv3
|
||
|
|
|
||
|
|
All of these policy rules could, for example, be constrained
|
||
|
|
either based on a filesystem's UUID (fsuuid) or based on LSM
|
||
|
|
labels.
|