munged - MUNGE daemon
daemon is responsible for authenticating local MUNGE clients
and servicing their credential encode & decode requests. All munged
daemons within a security realm share a secret key. This key is used to
protect the contents of a credential.
When a credential is created, munged
embeds metadata within it including
the effective UID and GID of the requesting client (as determined by
) and the current time (as determined by the local clock). It
then compresses the data, computes a message authentication code, encrypts the
data, and base64-encodes the result before returning the credential to the
When a credential is validated, munged
first checks the message
authentication code to ensure the credential has not been subsequently
altered. Next, it checks the embedded UID/GID restrictions to determine
whether the requesting client is allowed to decode it. Then, it checks the
embedded encode time against the current time; if this difference exceeds the
embedded time-to-live, the credential has expired. Finally, it checks whether
this credential has been previously decoded on this host; if so, the
credential has been replayed. If all checks pass, the credential metadata and
payload are returned to the client.
- -h, --help
- Display a summary of the command-line options.
- -L, --license
- Display license information.
- -V, --version
- Display version information.
- -f, --force
- Force the daemon to run if at all possible. This overrides
warnings for an existing local domain socket, a lack of entropy for the
PRNG, and insecure file/directory permissions. Use with caution as
overriding these warnings can affect security.
- -F, --foreground
- Run the daemon in the foreground.
- -M, --mlockall
- Lock all current and future pages in the virtual memory
address space. Access to locked pages will never be delayed by a page
fault. This can improve performance and help the daemon remain responsive
when the system is under heavy memory pressure. This typically requires
root privileges or the CAP_IPC_LOCK capability.
- -S, --socket path
- Specify the local domain socket for communicating with
- --auth-server-dir directory
- Specify an alternate directory in which the daemon will
create the pipe used to authenticate clients. The recommended permissions
for this directory are 0711. This option is only valid on platforms where
client authentication is performed via a file-descriptor passing
- --auth-client-dir directory
- Specify an alternate directory in which clients will create
the file used to authenticate themselves to the daemon. The recommended
permissions for this directory are 1733. This option is only valid on
platforms where client authentication is performed via a file-descriptor
- Disable recurring timers in order to reduce some noise
while benchmarking. This affects the PRNG entropy pool, supplementary
group mapping, and credential replay hash. Do not enable this option when
running in production.
- --group-check-mtime boolean
- Specify whether the modification time of /etc/group
should be checked before updating the supplementary group membership
mapping. If this value is non-zero, the check will be enabled and the
mapping will not be updated unless the file has been modified since the
- --group-update-time integer
- Specify the number of seconds between updates to the
supplementary group membership mapping; this mapping is used when
restricting credentials by GID. A value of 0 causes it to be computed
initially but never updated (unless triggered by a SIGHUP). A value
of -1 causes it to be disabled.
- --key-file path
- Specify an alternate pathname to the secret key file.
- --max-ttl integer
- Specify the maximum allowable time-to-live value (in
seconds) for a credential. This setting has an upper-bound imposed by the
hard-coded MUNGE_MAXIMUM_TTL value. Reducing it will limit the maximum
growth of the credential replay cache. This is viable if clocks within the
MUNGE realm can be kept in sync with minimal skew.
- --num-threads integer
- Specify the number of threads to spawn for processing
- --pid-file path
- Specify an alternate pathname for storing the Process ID of
- Redirect log messages to syslog when the daemon is running
in the background.
- Immediately update the supplementary group membership
mapping instead of waiting for the next scheduled update; this mapping is
used when restricting credentials by GID.
- Terminate the daemon.
All clocks within a security realm must be kept in sync within the credential
prevents a given credential from being decoded on a
particular host more than once, nothing prevents a credential from being
decoded on multiple hosts within the security realm before it expires.
Chris Dunlap <firstname.lastname@example.org>
Copyright (C) 2007-2016 Lawrence Livermore National Security, LLC.
Copyright (C) 2002-2007 The Regents of the University of California.
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, either version 3 of the License, or (at your option) any later
Additionally for the MUNGE library (libmunge), you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.