Implement inquire_names_for_mech in low-level API

This commit implements the inquire_names_for_mech method
from RFC 2744, and adds a simple test as well.

Part of #10

Author: DirectXMan12

gssapi/raw/misc.pyx

@@ -22,6 +22,10 @@ cdef extern from "gssapi.h":
     OM_uint32 gss_indicate_mechs(OM_uint32 *minor_status,
                                  gss_OID_set *mech_set)
 
+    OM_uint32 gss_inquire_names_for_mech(OM_uint32 *minor_status,
+                                         const gss_OID mech_type,
+                                         gss_OID_set *name_types)
+
 
 def indicate_mechs():
     """
@@ -43,6 +47,35 @@ def indicate_mechs():
         raise GSSError(maj_stat, min_stat)
 
 
+def inquire_names_for_mech(OID mech_type not None):
+    """Get the name types supported by a mechanism.
+
+    This method retrives the different name types supported by
+    the given mechanism.
+
+    Args:
+        mech_type (OID): the mechanism in question
+
+    Returns:
+        list: the name type OIDs supported by the given mechanism
+
+    Raises:
+        GSSError
+    """
+
+    cdef gss_OID_set name_types
+
+    cdef OM_uint32 maj_stat, min_stat
+
+    maj_stat = gss_inquire_names_for_mech(&min_stat, &mech_type.raw_oid,
+                                          &name_types)
+
+    if maj_stat == GSS_S_COMPLETE:
+        return c_create_oid_set(name_types)
+    else:
+        raise GSSError(maj_stat, min_stat)
+
+
 def _display_status(unsigned int error_code, bint is_major_code,
                     OID mech_type=None, unsigned int message_context=0):
     """

gssapi/tests/test_raw.py

@@ -365,6 +365,12 @@ def test_error_dispatch(self):
         err.should_be_a(gb.NameReadError)
         err.maj_code.should_be(err_code1 | err_code2)
 
+    def test_inquire_names_for_mech(self):
+        res = gb.inquire_names_for_mech(gb.MechType.kerberos)
+
+        res.shouldnt_be_none()
+        res.should_include(gb.NameType.kerberos_principal)
+
 
 class TestIntEnumFlagSet(unittest.TestCase):
     def test_create_from_int(self):