Provided by: munge_0.5.8-7_i386 bug


       munge - MUNGE overview


       MUNGE  (MUNGE  Uid  ’N’  Gid Emporium) is an authentication service for
       creating and validating credentials.   It  is  designed  to  be  highly
       scalable for use in an HPC cluster environment.  It allows a process to
       authenticate the UID and GID of another local or remote process  within
       a  group  of  hosts having common users and groups.  These hosts form a
       security realm that is defined by a shared cryptographic key.   Clients
       within  this security realm can create and validate credentials without
       the use  of  root  privileges,  reserved  ports,  or  platform-specific


       The  need for MUNGE arose out of the HPC cluster environment.  Consider
       the scenario in which a local daemon running on a login node receives a
       client  request and forwards it on to remote daemons running on compute
       nodes within the cluster.  Since the user has already logged on to  the
       login   node,   the  local  daemon  just  needs  a  reliable  means  of
       ascertaining the UID and GID of the client process.   Furthermore,  the
       remote  daemons need a mechanism to ensure the forwarded authentication
       data has not been subsequently altered.

       A common solution to this problem is to  use  Unix  domain  sockets  to
       determine  the  identity  of  the  local  client, and then forward this
       information on to remote hosts via trusted rsh connections.   But  this
       presents  several  new  problems.   First, there is no portable API for
       determining the identity  of  a  client  over  a  Unix  domain  socket.
       Second,  rsh  connections  must  originate  from  a  reserved port; the
       limited number of reserved ports available on  a  given  host  directly
       limits  scalability.   Third,  root privileges are required in order to
       bind to a reserved port.  Finally, the remote daemons have no means  of
       determining whether the client identity is authentic.


       A  process  creates a credential by requesting one from the local MUNGE
       service.  The encoded credential  contains  the  UID  and  GID  of  the
       originating  process.   This  process  sends  the credential to another
       process within the security realm as a means of proving  its  identity.
       The  receiving  process  validates  the  credential with the use of its
       local MUNGE service.  The decoded  credential  provides  the  receiving
       process  with  a  reliable means of ascertaining the UID and GID of the
       originating process.  This information can be used  for  accounting  or
       access control decisions.

       The  contents  of  the credential (including any optional payload data)
       are encrypted with a key  shared  by  all  munged  daemons  within  the
       security  realm.   The  integrity  of  the  credential  is ensured by a
       message authentication code (MAC).   The  credential  is  valid  for  a
       limited  time  defined  by  its time-to-live (TTL).  The daemon ensures
       unexpired credentials are not replayed on a particular host.   Decoding
       of a credential can be restricted to a particular user and/or group ID.
       The payload data can  be  used  for  purposes  such  as  embedding  the
       destination’s  address  to  ensure  the  credential  is only valid on a
       specific host.  The internal format of the credential is encoded  in  a
       platform-independent  manner.   And  the  credential  itself  is base64
       encoded to allow it to be transmitted over virtually any transport.


       Chris Dunlap <>


       Copyright (C) 2002-2007 The Regents of the  University  of  California.
       Produced  at Lawrence Livermore National Laboratory.  UCRL-CODE-155910.

       MUNGE 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.


       munge(1),    remunge(1),    unmunge(1),     munge(3),     munge_ctx(3),
       munge_enum(3), munged(8).