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Ticket #3008: DN objects hash differently depending on case

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Because the attrs & values in DN's, RDN's and AVA's are comparison case-
insensitive the hash value between two objects which compare as equal but
differ in case must also yield the same hash value. This is critical when
these objects are used as a dict key or in a set because dicts and sets
use the object's __hash__ value in conjunction with the objects __eq__
method to lookup the object.

The defect is the DN, RDN & AVA objects computed their hash from the case-
preserving string representation thus two otherwise equal objects
incorrectly yielded different hash values.

The problem manifests itself when one of these objects is used as a key in
a dict, for example a dn.

dn1 = DN(('cn', 'Bob'))
dn2 = DN(('cn', 'bob'))

dn1 == dn2 --> True

hash(dn1) == hash(dn2) --> False

d = {}

d[dn1] = x
d[dn2] = y

len(d) --> 2

The patch fixes the above by lower casing the string representation of
the object prior to computing it's hash.

The patch also corrects a spelling mistake and a bogus return value in
ldapupdate.py which happened to be discovered while researching this
bug.
This commit is contained in:
John Dennis 2012-08-17 15:34:40 -04:00 committed by Alexander Bokovoy
parent f397db79dd
commit 1328f984d0
3 changed files with 45 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
ipapython/dn.py
View File

@ -385,7 +385,7 @@ if container_dn in dn:
# (e.g. cmp()). The general rule is for objects supporting multiple
# values first their lengths are compared, then if the lengths match
# the respective components of each are pair-wise compared until one
# is discovered to be non-equal. The comparision is case insensitive.
# is discovered to be non-equal. The comparison is case insensitive.
Cloning (Object Copy):
@ -544,7 +544,7 @@ class AVA(object):
AVA objects support equality testing and comparsion (e.g. cmp()). When they
are compared the attr is compared first, if the 2 attr's are equal then the
values are compared. The comparision is case insensitive (because attr's map
values are compared. The comparison is case insensitive (because attr's map
to numeric OID's and their values derive from from the 'name' atribute type
(OID 2.5.4.41) whose EQUALITY MATCH RULE is caseIgnoreMatch.
@ -648,8 +648,13 @@ class AVA(object):
(key.__class__.__name__))
def __hash__(self):
# Hash is computed from AVA's string representation because it's immutable
return hash(str(self))
# Hash is computed from AVA's string representation because it's immutable.
#
# Because attrs & values are comparison case-insensitive the
# hash value between two objects which compare as equal but
# differ in case must yield the same hash value.
return hash(str(self).lower())
def __eq__(self, other):
'''
@ -676,7 +681,7 @@ class AVA(object):
if not isinstance(other, AVA):
return False
# Perform comparision between objects of same type
# Perform comparison between objects of same type
return self._attr_unicode.lower() == other.attr.lower() and \
self._value_unicode.lower() == other.value.lower()
@ -684,7 +689,7 @@ class AVA(object):
return not self.__eq__(other)
def __cmp__(self, other):
'comparision is case insensitive, see __eq__ doc for explanation'
'comparison is case insensitive, see __eq__ doc for explanation'
if not isinstance(other, AVA):
raise TypeError("expected AVA but got %s" % (other.__class__.__name__))
@ -803,8 +808,8 @@ class RDN(object):
the first AVA's properties, programmer beware! Recall the AVA's in the RDN
are sorted according the to AVA collating semantics.
RDN objects support equality testing and comparision. See AVA for the
definition of the comparision method.
RDN objects support equality testing and comparison. See AVA for the
definition of the comparison method.
RDN objects support concatenation and addition with other RDN's or AVA's
@ -933,7 +938,12 @@ class RDN(object):
def __hash__(self):
# Hash is computed from RDN's string representation because it's immutable
return hash(str(self))
#
# Because attrs & values are comparison case-insensitive the
# hash value between two objects which compare as equal but
# differ in case must yield the same hash value.
return hash(str(self).lower())
def __eq__(self, other):
# Try coercing string to RDN, if successful compare to coerced object
@ -948,7 +958,7 @@ class RDN(object):
if not isinstance(other, RDN):
return False
# Perform comparision between objects of same type
# Perform comparison between objects of same type
return self.avas == other.avas
def __ne__(self, other):
@ -1170,8 +1180,8 @@ class DN(object):
dn.insert(i, RDN(('cn','Bob')))
dn[i:i] = [('cn','Bob')]
DN objects support equality testing and comparision. See RDN for the
definition of the comparision method.
DN objects support equality testing and comparison. See RDN for the
definition of the comparison method.
DN objects implement startswith(), endswith() and the "in" membership
operator. You may pass a DN or RDN object to these. Examples:
@ -1290,7 +1300,12 @@ class DN(object):
def __hash__(self):
# Hash is computed from DN's string representation because it's immutable
return hash(str(self))
#
# Because attrs & values are comparison case-insensitive the
# hash value between two objects which compare as equal but
# differ in case must yield the same hash value.
return hash(str(self).lower())
def __eq__(self, other):
# Try coercing string to DN, if successful compare to coerced object
@ -1305,7 +1320,7 @@ class DN(object):
if not isinstance(other, DN):
return False
# Perform comparision between objects of same type
# Perform comparison between objects of same type
return self.rdns == other.rdns
def __ne__(self, other):

2
ipaserver/install/ldapupdate.py
View File

@ -265,7 +265,7 @@ class LDAPUpdate:
if not all_updates.get(dn):
all_updates[dn] = update
return all_updates
return
existing_update = all_updates[dn]
if 'default' in update:

30
tests/test_ipapython/test_dn.py
View File

@ -267,12 +267,12 @@ class TestAVA(unittest.TestCase):
self.assertEqual(result, -1)
def test_hashing(self):
# create AVA's that have the same value
immutable_ava1 = AVA((self.attr1, self.value1))
immutable_ava2 = AVA((self.attr1, self.value1))
# create AVA's that are equal but differ in case
immutable_ava1 = AVA((self.attr1.lower(), self.value1.upper()))
immutable_ava2 = AVA((self.attr1.upper(), self.value1.lower()))
mutable_ava1 = EditableAVA((self.attr1, self.value1))
mutable_ava2 = EditableAVA((self.attr1, self.value1))
mutable_ava1 = EditableAVA((self.attr1.lower(), self.value1.upper()))
mutable_ava2 = EditableAVA((self.attr1.upper(), self.value1.lower()))
# Immutable AVA's that are equal should hash to the same value.
# Mutable AVA's should not be hashable.
@ -828,12 +828,12 @@ class TestRDN(unittest.TestCase):
def test_hashing(self):
# create RDN's that have the same value
immutable_rdn1 = RDN((self.attr1, self.value1))
immutable_rdn2 = RDN((self.attr1, self.value1))
# create RDN's that are equal but differ in case
immutable_rdn1 = RDN((self.attr1.lower(), self.value1.upper()))
immutable_rdn2 = RDN((self.attr1.upper(), self.value1.lower()))
mutable_rdn1 = EditableRDN((self.attr1, self.value1))
mutable_rdn2 = EditableRDN((self.attr1, self.value1))
mutable_rdn1 = EditableRDN((self.attr1.lower(), self.value1.upper()))
mutable_rdn2 = EditableRDN((self.attr1.upper(), self.value1.lower()))
# Immutable RDN's that are equal should hash to the same value.
# Mutable RDN's should not be hashable.
@ -1706,12 +1706,12 @@ class TestDN(unittest.TestCase):
self.assertExpectedClass(DN_class, dn[i][j], 'AVA')
def test_hashing(self):
# create DN's that have the same value
immutable_dn1 = DN((self.attr1, self.value1))
immutable_dn2 = DN((self.attr1, self.value1))
# create DN's that are equal but differ in case
immutable_dn1 = DN((self.attr1.lower(), self.value1.upper()))
immutable_dn2 = DN((self.attr1.upper(), self.value1.lower()))
mutable_dn1 = EditableDN((self.attr1, self.value1))
mutable_dn2 = EditableDN((self.attr1, self.value1))
mutable_dn1 = EditableDN((self.attr1.lower(), self.value1.upper()))
mutable_dn2 = EditableDN((self.attr1.upper(), self.value1.lower()))
# Immutable DN's that are equal should hash to the same value.
# Mutable DN's should not be hashable.