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=] [fsname=]]
  25                         lsm:    [[subj_user=] [subj_role=] [subj_type=]
  26                                  [obj_user=] [obj_role=] [obj_type=]]
  27                         option: [[appraise_type=]] [template=] [permit_directio]
  28                                 [appraise_flag=] [keyrings=]
  29                 base:   func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
  30                                 [FIRMWARE_CHECK]
  31                                 [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
  32                                 [KEXEC_CMDLINE] [KEY_CHECK]
  33                         mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
  34                                [[^]MAY_EXEC]
  35                         fsmagic:= hex value
  36                         fsuuid:= file system UUID (e.g 8bcbe394-4f13-4144-be8e-5aa9ea2ce2f6)
  37                         uid:= decimal value
  38                         euid:= decimal value
  39                         fowner:= decimal value
  40                 lsm:    are LSM specific
  41                 option: appraise_type:= [imasig] [imasig|modsig]
  42                         appraise_flag:= [check_blacklist]
  43                         Currently, blacklist check is only for files signed with appended
  44                         signature.
  45                         keyrings:= list of keyrings
  46                         (eg, .builtin_trusted_keys|.ima). Only valid
  47                         when action is "measure" and func is KEY_CHECK.
  48                         template:= name of a defined IMA template type
  49                         (eg, ima-ng). Only valid when action is "measure".
  50                         pcr:= decimal value
  51
  52                 default policy:
  53                         # PROC_SUPER_MAGIC
  54                         dont_measure fsmagic=0x9fa0
  55                         dont_appraise fsmagic=0x9fa0
  56                         # SYSFS_MAGIC
  57                         dont_measure fsmagic=0x62656572
  58                         dont_appraise fsmagic=0x62656572
  59                         # DEBUGFS_MAGIC
  60                         dont_measure fsmagic=0x64626720
  61                         dont_appraise fsmagic=0x64626720
  62                         # TMPFS_MAGIC
  63                         dont_measure fsmagic=0x01021994
  64                         dont_appraise fsmagic=0x01021994
  65                         # RAMFS_MAGIC
  66                         dont_appraise fsmagic=0x858458f6
  67                         # DEVPTS_SUPER_MAGIC
  68                         dont_measure fsmagic=0x1cd1
  69                         dont_appraise fsmagic=0x1cd1
  70                         # BINFMTFS_MAGIC
  71                         dont_measure fsmagic=0x42494e4d
  72                         dont_appraise fsmagic=0x42494e4d
  73                         # SECURITYFS_MAGIC
  74                         dont_measure fsmagic=0x73636673
  75                         dont_appraise fsmagic=0x73636673
  76                         # SELINUX_MAGIC
  77                         dont_measure fsmagic=0xf97cff8c
  78                         dont_appraise fsmagic=0xf97cff8c
  79                         # CGROUP_SUPER_MAGIC
  80                         dont_measure fsmagic=0x27e0eb
  81                         dont_appraise fsmagic=0x27e0eb
  82                         # NSFS_MAGIC
  83                         dont_measure fsmagic=0x6e736673
  84                         dont_appraise fsmagic=0x6e736673
  85
  86                         measure func=BPRM_CHECK
  87                         measure func=FILE_MMAP mask=MAY_EXEC
  88                         measure func=FILE_CHECK mask=MAY_READ uid=0
  89                         measure func=MODULE_CHECK
  90                         measure func=FIRMWARE_CHECK
  91                         appraise fowner=0
  92
  93                 The default policy measures all executables in bprm_check,
  94                 all files mmapped executable in file_mmap, and all files
  95                 open for read by root in do_filp_open.  The default appraisal
  96                 policy appraises all files owned by root.
  97
  98                 Examples of LSM specific definitions:
  99
 100                 SELinux:
 101                         dont_measure obj_type=var_log_t
 102                         dont_appraise obj_type=var_log_t
 103                         dont_measure obj_type=auditd_log_t
 104                         dont_appraise obj_type=auditd_log_t
 105                         measure subj_user=system_u func=FILE_CHECK mask=MAY_READ
 106                         measure subj_role=system_r func=FILE_CHECK mask=MAY_READ
 107
 108                 Smack:
 109                         measure subj_user=_ func=FILE_CHECK mask=MAY_READ
 110
 111                 Example of measure rules using alternate PCRs:
 112
 113                         measure func=KEXEC_KERNEL_CHECK pcr=4
 114                         measure func=KEXEC_INITRAMFS_CHECK pcr=5
 115
 116                 Example of appraise rule allowing modsig appended signatures:
 117
 118                         appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig
 119
 120                 Example of measure rule using KEY_CHECK to measure all keys:
 121
 122                         measure func=KEY_CHECK
 123
 124                 Example of measure rule using KEY_CHECK to only measure
 125                 keys added to .builtin_trusted_keys or .ima keyring:
 126
 127                         measure func=KEY_CHECK keyrings=.builtin_trusted_keys|.ima