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rrsync(1)                        User Commands                       rrsync(1)


NAME

       rrsync - a script to setup restricted rsync users via ssh logins


SYNOPSIS

       rrsync [-ro|-rw] [-munge] [-no-del] [-no-lock] 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.


DESCRIPTION

       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.


OPTIONS

       -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.

       -help, -h
              Output this help message and exit.


SECURITY RESTRICTIONS

       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.


BASH SECURITY ISSUE

       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.


EXAMPLES

       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...


FILES

       ~/.ssh/authorized_keys


SEE ALSO

       rsync(1), rsyncd.conf(5)


VERSION

       This manpage is current for version 3.2.7 of rsync.


CREDITS

       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.


AUTHOR

       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.

rrsync from rsync 3.2.7           20 Oct 2022                        rrsync(1)

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