Properly handle octet (byte) strings when converting LDAP responses

If LDAP returns a UUID as an octet string the LDAP driver will fail to
convert it to something meaningful. The error usually looks something
like:

  ID attribute objectGUID not found in LDAP object

Microsoft AD's `objectGUID` parameter is stored and transmitted as an
octet string [0]. If you attempt to use the `objectGUID` to generate
user or group IDs, you'll get an HTTP 404 because keystone can't decode
it properly. This is unfortunate because `objectGUID` are a fixed
length, UUID format, and ideal for generating IDs in keystone. As
opposed to using the object's CN, which is variable length, and can
generate hashes that are larger than keystone's database table limit for
user IDs.

[0] https://docs.microsoft.com/en-us/windows/win32/ad/reading-an-objectampaposs-objectguid-and-creating-a-string-representation-of-the-guid

Change-Id: Id80b17bdff015e10340e636102576b7435bd564f
Closes-Bug: 1889936

3 files changed, 30 insertions, 1 deletions

diff --git a/keystone/identity/backends/ldap/common.py b/keystone/identity/backends/ldap/common.py
index 91e071335..d819467d9 100644
--- a/keystone/identity/backends/ldap/common.py
+++ b/keystone/identity/backends/ldap/common.py
@@ -18,6 +18,7 @@ import functools
 import os.path
 import re
 import sys
+import uuid
 import weakref
 
 import ldap.controls
@@ -93,7 +94,16 @@ def utf8_decode(value):
     :raises UnicodeDecodeError: for invalid UTF-8 encoding
     """
     if isinstance(value, bytes):
-        return _utf8_decoder(value)[0]
+        try:
+            return _utf8_decoder(value)[0]
+        except UnicodeDecodeError:
+            # NOTE(lbragstad): We could be dealing with a UUID in byte form,
+            # which some LDAP implementations use.
+            uuid_byte_string_length = 16
+            if len(value) == uuid_byte_string_length:
+                return str(uuid.UUID(bytes_le=value))
+            else:
+                raise
     return str(value)
 
 
diff --git a/keystone/tests/unit/identity/backends/test_ldap_common.py b/keystone/tests/unit/identity/backends/test_ldap_common.py
index 029ded643..6674d9e14 100644
--- a/keystone/tests/unit/identity/backends/test_ldap_common.py
+++ b/keystone/tests/unit/identity/backends/test_ldap_common.py
@@ -520,6 +520,20 @@ class CommonLdapTestCase(unit.BaseTestCase):
             # The user name should still be a string value.
             self.assertEqual(user_name, py_result[0][1]['user_name'][0])
 
+    def test_user_id_attribute_is_uuid_in_byte_form(self):
+        results = [(
+            'cn=alice,dc=example,dc=com',
+            {
+                'cn': [b'cn=alice'],
+                'objectGUID': [b'\xdd\xd8Rt\xee]bA\x8e(\xe39\x0b\xe1\xf8\xe8'],
+                'email': [uuid.uuid4().hex],
+                'sn': [uuid.uuid4().hex]
+            }
+        )]
+        py_result = common_ldap.convert_ldap_result(results)
+        exp_object_guid = '7452d8dd-5dee-4162-8e28-e3390be1f8e8'
+        self.assertEqual(exp_object_guid, py_result[0][1]['objectGUID'][0])
+
 
 class LDAPFilterQueryCompositionTest(unit.BaseTestCase):
     """These test cases test LDAP filter generation."""
diff --git a/releasenotes/notes/bug-1889936-78d6853b5212b8f1.yaml b/releasenotes/notes/bug-1889936-78d6853b5212b8f1.yaml
new file mode 100644
index 000000000..de96b27f7
--- /dev/null
+++ b/releasenotes/notes/bug-1889936-78d6853b5212b8f1.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    [`bug 1889936 <https://bugs.launchpad.net/keystone/+bug/1889936>`_]
+    Properly decode octet strings, or byte arrays, returned from LDAP.