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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | SECURITY RESTRICTIONS | BASH SECURITY ISSUE | EXAMPLES | FILES | SEE ALSO | VERSION | CREDITS | AUTHOR | COLOPHON |
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rrsync(1) User Commands rrsync(1)
rrsync - a script to setup restricted rsync users via ssh logins
rrsync [-ro|-rw] [-munge] [-no-del] [-no-lock] [-no-overwrite] DIR
The single non-option argument specifies the restricted DIR to
use. It can be relative to the user's home directory or an
absolute path.
The online version of this manpage (that includes cross-linking
of topics) is available at
⟨https://download.samba.org/pub/rsync/rrsync.1⟩.
A user's ssh login can be restricted to only allow the running of
an rsync transfer in one of two easy ways:
o forcing the running of the rrsync script
o forcing the running of an rsync daemon-over-ssh command.
Both of these setups use a feature of ssh that allows a command
to be forced to run instead of an interactive shell. However, if
the user's home shell is bash, please see BASH SECURITY ISSUE for
a potential issue.
To use the rrsync script, edit the user's ~/.ssh/authorized_keys
file and add a prefix like one of the following (followed by a
space) in front of each ssh-key line that should be restricted:
command="rrsync DIR"
command="rrsync -ro DIR"
command="rrsync -munge -no-del DIR"
Then, ensure that the rrsync script has your desired option
restrictions. You may want to copy the script to a local bin dir
with a unique name if you want to have multiple configurations.
One or more rrsync options can be specified prior to the DIR if
you want to further restrict the transfer.
To use an rsync daemon setup, edit the user's
~/.ssh/authorized_keys file and add a prefix like one of the
following (followed by a space) in front of each ssh-key line
that should be restricted:
command="rsync --server --daemon ."
command="rsync --server --daemon --config=/PATH/TO/rsyncd.conf ."
Then, ensure that the rsyncd.conf file is created with one or
more module names with the appropriate path and option
restrictions. If rsync's --config option is omitted, it defaults
to ~/rsyncd.conf. See the rsyncd.conf(5) manpage for details of
how to configure an rsync daemon.
When using rrsync, there can be just one restricted dir per
authorized key. A daemon setup, on the other hand, allows
multiple module names inside the config file, each one with its
own path setting.
The remainder of this manpage is dedicated to using the rrsync
script.
-ro Allow only reading from the DIR. Implies -no-del and -no-
lock.
-wo Allow only writing to the DIR.
-munge Enable rsync's --munge-links on the server side.
-no-del
Disable rsync's --delete* and --remove* options.
-no-lock
Avoid the single-run (per-user) lock check. Useful with
-munge.
-no-overwrite
Enforce --ignore-existing on the server. Prevents
overwriting existing files when the server is the
receiver.
-help, -h
Output this help message and exit.
The rrsync script validates the path arguments it is sent to try
to restrict them to staying within the specified DIR.
The rrsync script rejects rsync's --copy-links option (by
default) so that a copy cannot dereference a symlink within the
DIR to get to a file outside the DIR.
The rrsync script rejects rsync's --protect-args (-s) option
because it would allow options to be sent to the server-side that
the script cannot check. If you want to support --protect-args,
use a daemon-over-ssh setup.
The rrsync script accepts just a subset of rsync's options that
the real rsync uses when running the server command. A few extra
convenience options are also included to help it to interact with
BackupPC and accept some convenient user overrides.
The script (or a copy of it) can be manually edited if you want
it to customize the option handling.
If your users have bash set as their home shell, bash may try to
be overly helpful and ensure that the user's login bashrc files
are run prior to executing the forced command. This can be a
problem if the user can somehow update their home bashrc files,
perhaps via the restricted copy, a shared home directory, or
something similar.
One simple way to avoid the issue is to switch the user to a
simpler shell, such as dash. When choosing the new home shell,
make sure that you're not choosing bash in disguise, as it is
unclear if it avoids the security issue.
Another potential fix is to ensure that the user's home directory
is not a shared mount and that they have no means of copying
files outside of their restricted directories. This may require
you to force the enabling of symlink munging on the server side.
A future version of openssh may have a change to the handling of
forced commands that allows it to avoid using the user's home
shell.
The ~/.ssh/authorized_keys file might have lines in it like this:
command="rrsync client/logs" ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIEAzG...
command="rrsync -ro results" ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIEAmk...
~/.ssh/authorized_keys
rsync(1), rsyncd.conf(5)
This manpage is current for version 3.3.0 of rsync.
rsync is distributed under the GNU General Public License. See
the file COPYING for details.
An rsync web site is available at ⟨https://rsync.samba.org/⟩ and
its github project is ⟨https://github.com/WayneD/rsync⟩.
The original rrsync perl script was written by Joe Smith. Many
people have later contributed to it. The python version was
created by Wayne Davison.
This page is part of the rsync (a fast, versatile, remote (and
local) file-copying tool) project. Information about the project
can be found at ⟨https://rsync.samba.org/⟩. If you have a bug
report for this manual page, see
⟨https://rsync.samba.org/bugzilla.html⟩. This page was obtained
from the tarball fetched from
⟨https://download.samba.org/pub/rsync/⟩ on 2024-06-14. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to [email protected]
rrsync from rsync 3.3.0 6 Apr 2024 rrsync(1)
Pages that refer to this page: rsync(1)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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