| 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 | hash | dont_hash |
| 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][CREDS_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] |
| pcr:= decimal value |
| |
| 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 |
