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