rsync/support/rrsync.1.md

NAME

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

SYNOPSIS

rrsync [-ro|-rw] [-munge] [-no-del] DIR

DESCRIPTION

A user's ssh login can be restricted to only allow the running of an rsync transfer in one of two easy ways: forcing the running of the rrsync script or forcing the running of an rsync daemon-over-ssh command.

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 the --config option is omitted, it defaults to ~/rsyncd.conf. See the rsyncd.conf man page 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 man page is dedicated to using the rrsync script.

OPTION SUMMARY

-ro        Allow only reading from the DIR. Implies -no-del.
-wo        Allow only writing to the DIR.
-no-del    Disable rsync's --delete* and --remove* options.
-munge     Enable rsync's --munge-links on the server side.
-help, -h  Output this help message and exit.

A single non-option argument specifies the restricted DIR to use. It can be relative to the user's home directory or an absolute path.

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 could not 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.

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...