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- 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 [option]
- base: [[func=] [mask=] [fsmagic=] [fsuuid=] [uid=]
- [euid=] [fowner=]]
- lsm: [[subj_user=] [subj_role=] [subj_type=]
- [obj_user=] [obj_role=] [obj_type=]]
- option: [[appraise_type=]] [permit_directio]
- base: func:= [BPRM_CHECK][MMAP_CHECK][FILE_CHECK][MODULE_CHECK]
- [FIRMWARE_CHECK]
- [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
- 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
- fowner:=decimal value
- lsm: are LSM specific
- option: appraise_type:= [imasig]
- 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
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