From 6dc1de9781ab211a43d24cbaed7969d98abc1cc1 Mon Sep 17 00:00:00 2001
From: Lukas Slebodnik <lslebodn@redhat.com>
Date: Feb 15 2018 15:11:36 +0000
Subject: test_memory_cache: Regression test for #3571


Resolves:
https://pagure.io/SSSD/sssd/issue/3592

Reviewed-by: Sumit Bose <sbose@redhat.com>

---

diff --git a/src/tests/intg/test_memory_cache.py b/src/tests/intg/test_memory_cache.py
index cac9feb..0d13273 100644
--- a/src/tests/intg/test_memory_cache.py
+++ b/src/tests/intg/test_memory_cache.py
@@ -22,10 +22,15 @@ import ent
 import grp
 import pwd
 import config
+import random
 import signal
+import string
+import struct
 import subprocess
 import time
 import pytest
+import pysss_murmur
+
 import ds_openldap
 import ldap_ent
 import sssd_id
@@ -770,6 +775,82 @@ def test_invalidate_everything_after_stop(ldap_conn, sanity_rfc2307):
     assert_missing_mc_records_for_user1()
 
 
+def get_random_string(length):
+    return ''.join([random.choice(string.ascii_letters + string.digits)
+                    for n in range(length)])
+
+
+class MemoryCache(object):
+    SIZEOF_UINT32_T = 4
+
+    def __init__(self, path):
+        with open(path, "rb") as fin:
+            fin.seek(4 * self.SIZEOF_UINT32_T)
+            self.seed = struct.unpack('i', fin.read(4))[0]
+            self.data_size = struct.unpack('i', fin.read(4))[0]
+            self.ft_size = struct.unpack('i', fin.read(4))[0]
+            hash_len = struct.unpack('i', fin.read(4))[0]
+            self.hash_size = hash_len / self.SIZEOF_UINT32_T
+
+    def sss_nss_mc_hash(self, key):
+        input_key = key + '\0'
+        input_len = len(key) + 1
+
+        murmur_hash = pysss_murmur.murmurhash3(input_key, input_len, self.seed)
+        return murmur_hash % self.hash_size
+
+
+def test_colliding_hashes(ldap_conn, sanity_rfc2307):
+    """
+    Regression test for ticket:
+    https://pagure.io/SSSD/sssd/issue/3571
+    """
+
+    first_user = 'user1'
+
+    # initialize data in memcache
+    ent.assert_passwd_by_name(
+        first_user,
+        dict(name='user1', passwd='*', uid=1001, gid=2001,
+             gecos='1001', shell='/bin/bash'))
+
+    mem_cache = MemoryCache(config.MCACHE_PATH + '/passwd')
+
+    colliding_hash = mem_cache.sss_nss_mc_hash(first_user)
+
+    while True:
+        # string for colliding hash need to be longer then data for user1
+        # stored in memory cache (almost equivalent to:
+        #   `getent passwd user1 | wc -c` ==> 45
+        second_user = get_random_string(80)
+        val = mem_cache.sss_nss_mc_hash(second_user)
+        if val == colliding_hash:
+            break
+
+    # add new user to LDAP
+    ent_list = ldap_ent.List(ldap_conn.ds_inst.base_dn)
+    ent_list.add_user(second_user, 5001, 5001)
+    ldap_conn.add_s(ent_list[0][0], ent_list[0][1])
+
+    ent.assert_passwd_by_name(
+        second_user,
+        dict(name=second_user, passwd='*', uid=5001, gid=5001,
+             gecos='5001', shell='/bin/bash'))
+
+    stop_sssd()
+
+    # check that both users are stored in cache
+    ent.assert_passwd_by_name(
+        first_user,
+        dict(name='user1', passwd='*', uid=1001, gid=2001,
+             gecos='1001', shell='/bin/bash'))
+
+    ent.assert_passwd_by_name(
+        second_user,
+        dict(name=second_user, passwd='*', uid=5001, gid=5001,
+             gecos='5001', shell='/bin/bash'))
+
+
 def test_removed_mc(ldap_conn, sanity_rfc2307):
     """
     Regression test for ticket: