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.