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+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] (deprecated)
+ Setting the check_blacklist flag is no longer necessary.
+ All appraisal functions set it by default.
+ 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.