diff --git a/radicale/acl/PAM.py b/radicale/acl/PAM.py
new file mode 100644
index 0000000..ba42465
--- /dev/null
+++ b/radicale/acl/PAM.py
@@ -0,0 +1,64 @@
+# -*- coding: utf-8 -*-
+#
+# This file is part of Radicale Server - Calendar Server
+# Copyright © 2011 Corentin Le Bail
+# Copyright © 2011 Guillaume Ayoub
+#
+# This library is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+PAM ACL.
+
+Authentication based on the ``python-ldap`` module
+(http://www.python-ldap.org/).
+
+"""
+
+import grp
+import pam
+import pwd
+from radicale import acl, config, log
+
+
+GROUP_MEMBERSHIP = config.get("acl", "group_membership")
+
+
+def has_right(owner, user, password):
+    """Check if ``user``/``password`` couple is valid."""
+    if not user or (owner not in acl.PRIVATE_USERS and user != owner):
+        # No user given, or owner is not private and is not user, forbidden
+        return False
+    
+    try: # 1 - Does the user exist in the PAM system?
+      pwd.getpwnam(user).pw_uid
+      log.LOGGER.debug("User %s found" % user)
+    except KeyError: # No such user in the PAM system
+      log.LOGGER.debug("User %s not found" % user)
+      return False
+    
+    try: # 2 - Does the user belong to the required group?
+      for member in grp.getgrnam(GROUP_MEMBERSHIP):
+	if member == user:
+	  raise Exception()
+      log.LOGGER.debug("The user doesn't belong to the required group (%s)" % GROUP_MEMBERSHIP)
+      return False
+    except KeyError:
+      log.LOGGER.debug("The membership required group (%s) doesn't exist" % GROUP_MEMBERSHIP)
+      return False
+    except Exception:
+      log.LOGGER.debug("The user belong to the required group (%s)" % GROUP_MEMBERSHIP)
+        
+    if pam.authenticate(user, password): # 3 - Does the password match ?
+      return True
+    return False # Authentication failled