selinux/secilc/docs/cil_constraint_statements.md

Constraint Statements

constrain

Enable constraints to be placed on the specified permissions of the object class based on the source and target security context components.

Statement definition:

    (constrain classpermissionset_id ... expression | expr ...)

Where:

constrain	The constrain keyword.
classpermissionset_id	A single named or anonymous classpermissionset or a single set of classmap/classmapping identifiers.
expression	There must be one constraint expression or one or more expr's. The expression consists of an operator and two operands as follows: (op u1 u2) (role_op r1 r2) (op t1 t2) (op u1 user_id | (user_id ...)) (op u2 user_id | (user_id ...)) (op r1 role_id | (role_id ...)) (op r2 role_id | (role_id ...)) (op t1 type_id | (type_id ...)) (op t2 type_id | (type_id ...)) where: u1, r1, t1 = Source context: user, role or type u2, r2, t2 = Target context: user, role or type and: op : eq neq role_op : eq neq dom domby incomp user_id : A single user or userattribute identifier. role_id : A single role or roleattribute identifier. type_id : A single type, typealias or typeattribute identifier.
expr	Zero or more expr's, the valid operators and syntax are: (and expression expression) (or expression expression) (not expression)

Examples:

Two constrain statements are shown with their equivalent kernel policy language statements:

    ;; constrain { file } { write }
    ;;    (( t1 == unconfined.process  ) and ( t2 == unconfined.object  ) or ( r1 eq r2 ));
    (constrain (file (write))
        (or
            (and
                (eq t1 unconfined.process)
                (eq t2 unconfined.object)
            )
            (eq r1 r2)
        )
    )

    ;; constrain { file } { read }
    ;;    (not( t1 == unconfined.process  ) and ( t2 == unconfined.object  ) or ( r1 eq r2 ));
    (constrain (file (read))
        (not
            (or
                (and
                    (eq t1 unconfined.process)
                    (eq t2 unconfined.object)
                )
                (eq r1 r2)
            )
        )
    )

validatetrans

The validatetrans statement is only used for file related object classes where it is used to control the ability to change the objects security context based on old, new and the current process security context.

Statement definition:

    (validatetrans class_id expression | expr ...)

Where:

validatetrans	The validatetrans keyword.
class_id	A single previously declared class or classmap identifier.
expression	There must be one constraint expression or one or more expr's. The expression consists of an operator and two operands as follows: (op u1 u2) (role_op r1 r2) (op t1 t2) (op u1 user_id) (op u2 user_id) (op u3 user_id) (op r1 role_id) (op r2 role_id) (op r3 role_id) (op t1 type_id) (op t2 type_id) (op t3 type_id) where: u1, r1, t1 = Old context: user, role or type u2, r2, t2 = New context: user, role or type u3, r3, t3 = Process context: user, role or type and: op : eq neq role_op : eq neq dom domby incomp user_id : A single user or userattribute identifier. role_id : A single role or roleattribute identifier. type_id : A single type, typealias or typeattribute identifier.
expr	Zero or more expr's, the valid operators and syntax are: (and expression expression) (or expression expression) (not expression)

Example:

A validate transition statement with the equivalent kernel policy language statement:

    ; validatetrans { file } ( t1 == unconfined.process  );

    (validatetrans file (eq t1 unconfined.process))

mlsconstrain

Enable MLS constraints to be placed on the specified permissions of the object class based on the source and target security context components.

Statement definition:

    (mlsconstrain classpermissionset_id ... expression | expr ...)

Where:

mlsconstrain	The mlsconstrain keyword.
classpermissionset_id	A single named or anonymous classpermissionset or a single set of classmap/classmapping identifiers.
expression	There must be one constraint expression or one or more expr's. The expression consists of an operator and two operands as follows: (op u1 u2) (mls_role_op r1 r2) (op t1 t2) (mls_role_op l1 l2) (mls_role_op l1 h2) (mls_role_op h1 l2) (mls_role_op h1 h2) (mls_role_op l1 h1) (mls_role_op l2 h2) (op u1 user_id) (op u2 user_id) (op r1 role_id) (op r2 role_id) (op t1 type_id) (op t2 type_id) where: u1, r1, t1, l1, h1 = Source context: user, role, type, low level or high level u2, r2, t2, l2, h2 = Target context: user, role, type, low level or high level and: op : eq neq mls_role_op : eq neq dom domby incomp user_id : A single user or userattribute identifier. role_id : A single role or roleattribute identifier. type_id : A single type, typealias or typeattribute identifier.
expr	Zero or more expr's, the valid operators and syntax are: (and expression expression) (or expression expression) (not expression)

Example:

An MLS constrain statement with the equivalent kernel policy language statement:

    ;; mlsconstrain { file } { open }
    ;;     (( l1 eq l2 ) and ( u1 == u2 ) or ( r1 != r2 ));

    (mlsconstrain (file (open))
        (or
            (and
                (eq l1 l2)
                (eq u1 u2)
            )
            (neq r1 r2)
        )
    )

mlsvalidatetrans

The mlsvalidatetrans statement is only used for file related object classes where it is used to control the ability to change the objects security context based on old, new and the current process security context.

Statement definition:

    (mlsvalidatetrans class_id expression | expr ...)

Where:

mlsvalidatetrans	The mlsvalidatetrans keyword.
class_id	A single previously declared class or classmap identifier.
expression	There must be one constraint expression or one or more expr's. The expression consists of an operator and two operands as follows: (op u1 u2) (mls_role_op r1 r2) (op t1 t2) (mls_role_op l1 l2) (mls_role_op l1 h2) (mls_role_op h1 l2) (mls_role_op h1 h2) (mls_role_op l1 h1) (mls_role_op l2 h2) (op u1 user_id) (op u2 user_id) (op u3 user_id) (op r1 role_id) (op r2 role_id) (op r3 role_id) (op t1 type_id) (op t2 type_id) (op t3 type_id) where: u1, r1, t1, l1, h1 = Source context: user, role, type, low level or high level u2, r2, t2, l2, h2 = Target context: user, role, type, low level or high level u3, r3, t3 = Process context: user, role or type and: op : eq neq mls_role_op : eq neq dom domby incomp user_id : A single user or userattribute identifier. role_id : A single role or roleattribute identifier. type_id : A single type, typealias or typeattribute identifier.
expr	Zero or more expr's, the valid operators and syntax are: (and expression expression) (or expression expression) (not expression)

Example:

An MLS validate transition statement with the equivalent kernel policy language statement:

    ;; mlsvalidatetrans { file } ( l1 domby h2 );

    (mlsvalidatetrans file (domby l1 h2))