sepolgen: Support named xperms

The `allowxperm` et. al. directives take a magical integer for one of
the fields, which hinders readability.  This commit adds support for
basic names for a number or group of numbers.

Notably, this does not support recursive definition of names, as that
would require a larger grammar re-write to avoid parsing conflicts.

Signed-off-by: Chris Lindee <[email protected]>

python/sepolgen/src/sepolgen/refparser.py

@@ -349,6 +349,7 @@ def p_statement(p):
  '''statement : interface
  | template
  | obj_perm_set
+ | obj_xperm_set
  | policy
  | policy_module_stmt
  | module_stmt
@@ -502,7 +503,15 @@ def p_obj_perm_set(p):
  s = refpolicy.ObjPermSet(p[4])
  s.perms = p[8]
  p[0] = s
-
+
+def p_obj_xperm_set(p):
+ 'obj_xperm_set : DEFINE OPAREN TICK IDENTIFIER SQUOTE COMMA TICK xperm_set_base SQUOTE CPAREN'
+ ids = refpolicy.XpermIdentifierDict()
+ ids.set(p[4], p[8])
+
+ p[0] = refpolicy.ObjPermSet(p[4])
+ p[0].perms = set(p[8])
+
 #
 # Basic SELinux policy language
 #
@@ -1049,8 +1058,13 @@ def p_nested_xperm_list(p):
 def p_nested_xperm_element(p):
  '''nested_xperm_element : xperm_set_base
  | nested_xperm_set
+ | IDENTIFIER
  '''
- p[0] = p[1]
+ if isinstance(p[1], refpolicy.XpermSet()):
+ p[0] = p[1]
+ else:
+ ids = refpolicy.XpermIdentifierDict()
+ p[0] = ids.get(p[1])
 
 def p_xperm_set_base(p):
  '''xperm_set_base : xperm_number

python/sepolgen/src/sepolgen/refpolicy.py

@@ -413,6 +413,24 @@ def to_string(self):
 
  return "%s{ %s }" % (compl, " ".join(vals))
 
+class XpermIdentifierDict(dict):
+ """Extended permission set identifier mapping.
+
+ This singleton class holds the mappings between named
+ extended permission and their numberic value.
+ """
+ def __new__(cls):
+ if not hasattr(cls, 'instance'):
+ cls.instance = super(XpermIdentifierDict, cls).__new__(cls)
+ return cls.instance
+
+ def set(self, key, value):
+ # TODO: warn about redefiniition
+ self[key] = value
+
+ def get(self, key):
+ return self[key]
+
 # Basic statements
 
 class TypeAttribute(Leaf):