Documentation/ABI/testing/ima_policy

   1 What:           security/ima/policy
   2 Date:           May 2008
   3 Contact:        Mimi Zohar <zohar@us.ibm.com>
   4 Description:
   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                 rule format: action [condition ...]
  19
  20                 action: measure | dont_measure | appraise | dont_appraise |
  21                         audit | hash | dont_hash
  22                 condition:= base | lsm  [option]
  23                         base:   [[func=] [mask=] [fsmagic=] [fsuuid=] [uid=]
  24                                 [euid=] [fowner=]]
  25                         lsm:    [[subj_user=] [subj_role=] [subj_type=]
  26                                  [obj_user=] [obj_role=] [obj_type=]]
  27                         option: [[appraise_type=]] [permit_directio]
  28
  29                 base:   func:= [BPRM_CHECK][MMAP_CHECK][FILE_CHECK][MODULE_CHECK]
  30                                 [FIRMWARE_CHECK]
  31                                 [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
  32                         mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
  33                                [[^]MAY_EXEC]
  34                         fsmagic:= hex value
  35                         fsuuid:= file system UUID (e.g 8bcbe394-4f13-4144-be8e-5aa9ea2ce2f6)
  36                         uid:= decimal value
  37                         euid:= decimal value
  38                         fowner:= decimal value
  39                 lsm:    are LSM specific
  40                 option: appraise_type:= [imasig]
  41                         pcr:= decimal value
  42
  43                 default policy:
  44                         # PROC_SUPER_MAGIC
  45                         dont_measure fsmagic=0x9fa0
  46                         dont_appraise fsmagic=0x9fa0
  47                         # SYSFS_MAGIC
  48                         dont_measure fsmagic=0x62656572
  49                         dont_appraise fsmagic=0x62656572
  50                         # DEBUGFS_MAGIC
  51                         dont_measure fsmagic=0x64626720
  52                         dont_appraise fsmagic=0x64626720
  53                         # TMPFS_MAGIC
  54                         dont_measure fsmagic=0x01021994
  55                         dont_appraise fsmagic=0x01021994
  56                         # RAMFS_MAGIC
  57                         dont_appraise fsmagic=0x858458f6
  58                         # DEVPTS_SUPER_MAGIC
  59                         dont_measure fsmagic=0x1cd1
  60                         dont_appraise fsmagic=0x1cd1
  61                         # BINFMTFS_MAGIC
  62                         dont_measure fsmagic=0x42494e4d
  63                         dont_appraise fsmagic=0x42494e4d
  64                         # SECURITYFS_MAGIC
  65                         dont_measure fsmagic=0x73636673
  66                         dont_appraise fsmagic=0x73636673
  67                         # SELINUX_MAGIC
  68                         dont_measure fsmagic=0xf97cff8c
  69                         dont_appraise fsmagic=0xf97cff8c
  70                         # CGROUP_SUPER_MAGIC
  71                         dont_measure fsmagic=0x27e0eb
  72                         dont_appraise fsmagic=0x27e0eb
  73                         # NSFS_MAGIC
  74                         dont_measure fsmagic=0x6e736673
  75                         dont_appraise fsmagic=0x6e736673
  76
  77                         measure func=BPRM_CHECK
  78                         measure func=FILE_MMAP mask=MAY_EXEC
  79                         measure func=FILE_CHECK mask=MAY_READ uid=0
  80                         measure func=MODULE_CHECK
  81                         measure func=FIRMWARE_CHECK
  82                         appraise fowner=0
  83
  84                 The default policy measures all executables in bprm_check,
  85                 all files mmapped executable in file_mmap, and all files
  86                 open for read by root in do_filp_open.  The default appraisal
  87                 policy appraises all files owned by root.
  88
  89                 Examples of LSM specific definitions:
  90
  91                 SELinux:
  92                         dont_measure obj_type=var_log_t
  93                         dont_appraise obj_type=var_log_t
  94                         dont_measure obj_type=auditd_log_t
  95                         dont_appraise obj_type=auditd_log_t
  96                         measure subj_user=system_u func=FILE_CHECK mask=MAY_READ
  97                         measure subj_role=system_r func=FILE_CHECK mask=MAY_READ
  98
  99                 Smack:
 100                         measure subj_user=_ func=FILE_CHECK mask=MAY_READ
 101
 102                 Example of measure rules using alternate PCRs:
 103
 104                         measure func=KEXEC_KERNEL_CHECK pcr=4
 105                         measure func=KEXEC_INITRAMFS_CHECK pcr=5