diff options
Diffstat (limited to 'Documentation/ABI/testing/ima_policy')
| -rw-r--r-- | Documentation/ABI/testing/ima_policy | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy new file mode 100644 index 000000000..db17fc8a0 --- /dev/null +++ b/Documentation/ABI/testing/ima_policy @@ -0,0 +1,190 @@ +What: /sys/kernel/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=] [fsname=] + [uid=] [euid=] [gid=] [egid=] + [fowner=] [fgroup=]] + lsm: [[subj_user=] [subj_role=] [subj_type=] + [obj_user=] [obj_role=] [obj_type=]] + option: [digest_type=] [template=] [permit_directio] + [appraise_type=] [appraise_flag=] + [appraise_algos=] [keyrings=] + base: + func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK] + [FIRMWARE_CHECK] + [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK] + [KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA] + [SETXATTR_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 + gid:= decimal value + egid:= decimal value + fowner:= decimal value + fgroup:= decimal value + lsm: are LSM specific + option: + appraise_type:= [imasig] | [imasig|modsig] | [sigv3] + where 'imasig' is the original or the signature + format v2. + where 'modsig' is an appended signature, + where 'sigv3' is the signature format v3. (Currently + limited to fsverity digest based signatures + stored in security.ima xattr. Requires + specifying "digest_type=verity" first.) + + appraise_flag:= [check_blacklist] + Currently, blacklist check is only for files signed with appended + signature. + digest_type:= verity + Require fs-verity's file digest instead of the + regular IMA file hash. + keyrings:= list of keyrings + (eg, .builtin_trusted_keys|.ima). Only valid + when action is "measure" and func is KEY_CHECK. + template:= name of a defined IMA template type + (eg, ima-ng). Only valid when action is "measure". + pcr:= decimal value + label:= [selinux]|[kernel_info]|[data_label] + data_label:= a unique string used for grouping and limiting critical data. + For example, "selinux" to measure critical data for SELinux. + appraise_algos:= comma-separated list of hash algorithms + For example, "sha256,sha512" to only accept to appraise + files where the security.ima xattr was hashed with one + of these two algorithms. + + 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 + + Example of appraise rule allowing modsig appended signatures: + + appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig + + Example of measure rule using KEY_CHECK to measure all keys: + + measure func=KEY_CHECK + + Example of measure rule using KEY_CHECK to only measure + keys added to .builtin_trusted_keys or .ima keyring: + + measure func=KEY_CHECK keyrings=.builtin_trusted_keys|.ima + + Example of the special SETXATTR_CHECK appraise rule, that + restricts the hash algorithms allowed when writing to the + security.ima xattr of a file: + + appraise func=SETXATTR_CHECK appraise_algos=sha256,sha384,sha512 + + Example of a 'measure' rule requiring fs-verity's digests + with indication of type of digest in the measurement list. + + measure func=FILE_CHECK digest_type=verity \ + template=ima-ngv2 + + Example of 'measure' and 'appraise' rules requiring fs-verity + signatures (format version 3) stored in security.ima xattr. + + The 'measure' rule specifies the 'ima-sigv3' template option, + which includes the indication of type of digest and the file + signature in the measurement list. + + measure func=BPRM_CHECK digest_type=verity \ + template=ima-sigv3 + + + The 'appraise' rule specifies the type and signature format + version (sigv3) required. + + appraise func=BPRM_CHECK digest_type=verity \ + appraise_type=sigv3 + + All of these policy rules could, for example, be constrained + either based on a filesystem's UUID (fsuuid) or based on LSM + labels. |