1MUNGE(7) MUNGE Uid 'N' Gid Emporium MUNGE(7)
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7 munge - MUNGE overview
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11 MUNGE (MUNGE Uid 'N' Gid Emporium) is an authentication service for
12 creating and validating credentials. It is designed to be highly scal‐
13 able for use in an HPC cluster environment. It allows a process to
14 authenticate the UID and GID of another local or remote process within
15 a group of hosts having common users and groups. These hosts form a
16 security realm that is defined by a shared cryptographic key. Clients
17 within this security realm can create and validate credentials without
18 the use of root privileges, reserved ports, or platform-specific meth‐
19 ods.
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23 The need for MUNGE arose out of the HPC cluster environment. Consider
24 the scenario in which a local daemon running on a login node receives a
25 client request and forwards it on to remote daemons running on compute
26 nodes within the cluster. Since the user has already logged on to the
27 login node, the local daemon just needs a reliable means of ascertain‐
28 ing the UID and GID of the client process. Furthermore, the remote
29 daemons need a mechanism to ensure the forwarded authentication data
30 has not been subsequently altered.
31 A common solution to this problem is to use Unix domain sockets to
33 determine the identity of the local client, and then forward this
34 information on to remote hosts via trusted rsh connections. But this
35 presents several new problems. First, there is no portable API for
36 determining the identity of a client over a Unix domain socket. Sec‐
37 ond, rsh connections must originate from a reserved port; the limited
38 number of reserved ports available on a given host directly limits
39 scalability. Third, root privileges are required in order to bind to a
40 reserved port. Finally, the remote daemons have no means of determin‐
41 ing whether the client identity is authentic.
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45 A process creates a credential by requesting one from the local MUNGE
46 service. The encoded credential contains the UID and GID of the origi‐
47 nating process. This process sends the credential to another process
48 within the security realm as a means of proving its identity. The
49 receiving process validates the credential with the use of its local
50 MUNGE service. The decoded credential provides the receiving process
51 with a reliable means of ascertaining the UID and GID of the originat‐
52 ing process. This information can be used for accounting or access
53 control decisions.
54 The contents of the credential (including any optional payload data)
56 are encrypted with a key shared by all munged daemons within the secu‐
57 rity realm. The integrity of the credential is ensured by a message
58 authentication code (MAC). The credential is valid for a limited time
59 defined by its time-to-live (TTL). The daemon ensures unexpired cre‐
60 dentials are not replayed on a particular host. Decoding of a creden‐
61 tial can be restricted to a particular user and/or group ID. The pay‐
62 load data can be used for purposes such as embedding the destination's
63 address to ensure the credential is only valid on a specific host. The
64 internal format of the credential is encoded in a platform-independent
65 manner. And the credential itself is base64 encoded to allow it to be
66 transmitted over virtually any transport.
67
70 Chris Dunlap <cdunlap@llnl.gov>
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74 Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
75 Copyright (C) 2002-2007 The Regents of the University of California.
76 MUNGE is free software: you can redistribute it and/or modify it under
78 the terms of the GNU General Public License as published by the Free
79 Software Foundation, either version 3 of the License, or (at your
80 option) any later version. Additionally for the MUNGE library (lib‐
81 munge), you can redistribute it and/or modify it under the terms of the
82 GNU Lesser General Public License as published by the Free Software
83 Foundation, either version 3 of the License, or (at your option) any
84 later version.
85
88 munge(1), remunge(1), unmunge(1), munge(3), munge_ctx(3),
89 munge_enum(3), munged(8).
90 http://home.gna.org/munge/
92munge-0.5.9 2010-03-23 MUNGE(7)