Ubuntu Manpage: munged - MUNGE daemon

NAME

       munged - MUNGE daemon

SYNOPSIS

       munged [OPTION]...

DESCRIPTION

The munged daemon is responsible for authenticating local MUNGE clients and servicing
their credential encode & decode requests.

All munged daemons within a security realm share a common key. All hosts within this
realm are expected to have common users/UIDs and groups/GIDs. The key is used to
cryptographically protect the credentials; it is created with the mungekey command.

When a credential is created, munged embeds metadata within it including the effective UID
and GID of the requesting client (as determined by munged) 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 client.

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.

OPTIONS

-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, --stop
Stop the daemon bound to the socket and wait for it to shut down. Use with the
--socket option to target a daemon bound to a non-default socket location. This
option exits with a zero status if the specified daemon was successfully stopped,
or a non-zero status otherwise.

-S, --socket path
Specify the local domain socket for communicating with clients.

-v, --verbose
Be verbose.

--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 mechanism.

--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 passing mechanism.

--benchmark
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 last update.

--group-update-time seconds
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 key file.

--log-file path
Specify an alternate pathname to the log 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 credential requests.

--origin address
Specify the origin address that will be encoded into credential metadata. This can
be a hostname or IPv4 address; it can also be the name of a local network
interface, in which case the first IPv4 address found assigned to that interface
will be used. The default value is the IPv4 address of the hostname returned by
gethostname(). Failure to lookup the address will result in an error; if
overridden, the origin will be set to the null address.

--pid-file path
Specify an alternate pathname for storing the Process ID of the daemon.

--seed-file path
Specify an alternate pathname to the PRNG seed file.

--syslog
Redirect log messages to syslog when the daemon is running in the background.

--trusted-group group
Specify the group name or GID of the "trusted group". This is used for permission
checks on a directory hierarchy. Directories with group write permissions are
allowed if they are owned by the trusted group (or the sticky bit is set).

SIGNALS

       SIGHUP Immediately update the supplementary group membership mapping  instead  of  waiting
              for the next scheduled update; this mapping is used when restricting credentials by
              GID.

       SIGTERM
              Terminate the daemon.

NOTES

       All clocks within a security realm must be kept in sync within the credential time-to-live
       setting.

       While munged 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.

AUTHOR

       Chris Dunlap <cdunlap@llnl.gov>

COPYRIGHT

       Copyright (C) 2007-2022 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 version.

       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.