rrsync(1) rrsync from rsync 3.3.0 rrsync(1)
User Commands User Commands
6 Apr 2024
NAME
rrsync - a script to setup restricted rsync users via ssh logins
SYNOPSIS
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
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
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rrsync(1) rrsync from rsync 3.3.0 rrsync(1)
User Commands User Commands
6 Apr 2024
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.
-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.
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
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rrsync(1) rrsync from rsync 3.3.0 rrsync(1)
User Commands User Commands
6 Apr 2024
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 3.3.0 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 and its github project is
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.
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