v811_spc009/external/selinux/secilc/docs/cil_conditional_statements.md

Conditional Statements

boolean

Declares a run time boolean as true or false in the current namespace. The booleanif statement contains the CIL code that will be in the binary policy file.

Statement definition:

(boolean boolean_id true|false)

Where:

boolean	The boolean keyword.
boolean_id	The boolean identifier.
true | false	The initial state of the boolean. This can be changed at run time using setsebool(8) and its status queried using getsebool(8).

Example:

See the booleanif statement for an example.

booleanif

Contains the run time conditional statements that are instantiated in the binary policy according to the computed boolean identifier(s) state.

call statements are allowed within a booleanif, however the contents of the resulting macro must be limited to those of the booleanif statement (i.e. allow, auditallow, dontaudit, typemember, typetransition, typechange and the compile time tunableif statement)).

Statement definition:

(booleanif boolean_id | expr ...)
    (true
        cil_statements
        ...)
    (false
        cil_statements
        ...)
)

Where:

booleanif	The booleanif keyword.
boolean_id	Either a single boolean identifier or one or more expr's.
expr	Zero or more expr's, the valid operators and syntax are: (and (boolean_id boolean_id)) (or (boolean_id boolean_id)) (xor (boolean_id boolean_id)) (eq (boolean_id boolean_id)) (neq (boolean_id boolean_id)) (not (boolean_id))
true	An optional set of CIL statements that will be instantiated when the boolean is evaluated as true.
false	An optional set of CIL statements that will be instantiated when the boolean is evaluated as false.

Examples:

The second example also shows the kernel policy language equivalent:

(boolean disableAudio false)

(booleanif disableAudio
    (false
        (allow process mediaserver.audio_device (chr_file_set (rw_file_perms)))
    )
)

(boolean disableAudioCapture false)

;;; if(!disableAudio && !disableAudioCapture) {
(booleanif (and (not disableAudio) (not disableAudioCapture))
    (true
        (allow process mediaserver.audio_capture_device (chr_file_set (rw_file_perms)))
    )
)

tunable

Tunables are similar to booleans, however they are used to manage areas of CIL statements that may or may not be in the final CIL policy that will be compiled (whereas booleans are embedded in the binary policy and can be enabled or disabled during run-time).

Note that tunables can be treated as booleans by the CIL compiler command line parameter -P or --preserve-tunables flags.

Statement definition:

(tunable tunable_id true|false)

Where:

tunable	The tunable keyword.
tunable_id	The tunable identifier.
true | false	The initial state of the tunable.

Example:

See the tunableif statement for an example.

tunableif

Compile time conditional statement that may or may not add CIL statements to be compiled.

Statement definition:

(tunableif tunable_id | expr ...)
    (true
        cil_statements
        ...)
    (false
        cil_statements
        ...)
)

Where:

tunableif	The tunableif keyword.
tunable_id	Either a single tunable identifier or one or more expr's.
expr	Zero or more expr's, the valid operators and syntax are: (and (tunable_id tunable_id)) (or (tunable_id tunable_id)) (xor (tunable_id tunable_id)) (eq (tunable_id tunable_id)) (neq (tunable_id tunable_id)) (not (tunable_id))
true	An optional set of CIL statements that will be instantiated when the tunable is evaluated as true.
false	An optional set of CIL statements that will be instantiated when the tunable is evaluated as false.

Example:

This example will not add the range transition rule to the binary policy:

(tunable range_trans_rule false)

(block init
    (class process (process))
    (type process)

    (tunableif range_trans_rule
        (true
            (rangetransition process sshd.exec process low_high)
        )
    ) ; End tunableif
) ; End block