ObjectClassStatements

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[edit] Object Class and Permission Statements

For those who write or manager SELinux policy, there is no need to define new objects and their associated permissions as these would be done by those who actually design and/or write object managers.

A list of object classes used by the Reference Policy can be found in the ./policy/flask/security_classes file.

There are two variants of the class statement for writing policy:

  1. There is the class statement that declares the actual class identifier or name.
  2. There is a further refinement of the class statement that associates permissions to the class as discussed in the Associating Permissions to a Class section.

[edit] class

Object classes are declared within a policy as follows:

The statement definition is:

class class_id

Where:

class The class keyword.
class_id The class identifier.


The statement is valid in:

Monolithic Policy
Base Policy
Module Policy
Yes
Yes
No
if Statement
optional Statement
require Statement
No
No
Yes


Example:

# Define the PostgreSQL db_tuple object class
#
class db_tuple

[edit] Associating Permissions to a Class

Permissions can be defined within policy in two ways:

  1. Define a set of common permissions that can then be inherited by one or more object classes using further class statements.
  2. Define class specific permissions. This is where permissions are declared for a specific object class only (i.e. the permission is not inherited by any other object class).

A list of classes and their permissions used by the Reference Policy can be found in the ./policy/flask/access_vectors file.

[edit] common

Declare a common identifier and associate one or more common permissions.

The statement definition is:

common common_id { perm_set }

Where:

common The common keyword.
common_id The common identifier.
perm_set One or more permission identifiers in a space separated list enclosed within braces ({}).


The statement is valid in:

Monolithic Policy
Base Policy
Module Policy
Yes
Yes
No
if Statement
optional Statement
require Statement
No
No
No


Example:

# Define the common PostgreSQL permissions
#
common database { create drop getattr setattr relabelfrom relabelto }

[edit] class

Inherit and / or associate permissions to a previously declared class identifier.

The statement definition is:

class class_id [ inherits common_set ] [ { perm_set } ]

Where:

class The class keyword.
class_id The previously declared class identifier.
inherits The optional inherits keyword that allows a set of common permissions to be inherited.
common_set A previously declared common identifier.
perm_set One or more optional permission identifiers in a space separated list enclosed within braces ({}).


Note:

There must be at least one common_set or one perm_set defined within the statement.

The statement is valid in:

Monolithic Policy
Base Policy
Module Policy
Yes
Yes
No
if Statement
optional Statement
require Statement
No
No
Yes


Examples:

# The following example shows the db_tuple object class being 
# allocated two permissions: 

class db_tuple { relabelfrom relabelto }

# The following example shows the db_blob object class
# inheriting permissions from the database set of common
# permissions (as described in the "Associating Permissions
# to a Class" section): 

class db_blob inherits database
# The following example (from the access_vector file) shows the 
# db_blob object class inheriting permissions from the database 
# set of common permissions and adding a further four permissions: 

class db_blob inherits database { read write import export }


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