Andrew Tridgell
838513e96d
Refusing a shell-active %VAR% in an exec hook is a real usability cost
and it is not confined to hostile input: the check runs on every
%RSYNC_*% value, so a module whose path holds a space cannot be
interpolated into a hook at all. `path = /srv/My Backups` with a command
mentioning %RSYNC_MODULE_PATH% refuses every transfer of that module,
with no attacker involved.
That is deliberate rather than an oversight. rsync escapes a
substitution for the quoting context it sits in, which is right for the
one shell that runs the command and wrong for a command that starts a
second one -- `sh -c '... %RSYNC_USER_NAME% ...'` hands the inner shell a
bare value, where "touc?" is glob-expanded against /usr/bin and chooses
the command rather than being data for it. Escaping for an unknown
number of passes is not possible, so the value is refused instead. Nor
can the check exempt operator-supplied values: `path` may itself be
templated from a peer one (`path = /home/%RSYNC_USER_NAME%`), and once
both are inside the same string rsync cannot tell them apart.
Say so in the manual, and give the way out: the same names are exported
to the command, so $RSYNC_MODULE_PATH inside a script is unrestricted.
The test pins both halves, since a documented behaviour with no oracle
drifts. Both are fault-injected: narrowing the refused set back makes
the interpolated half pass when the manual says it must not, and dropping
the RSYNC_MODULE_PATH export fails the workaround half.
(cherry picked from commit 5bf9940de4)
WHAT IS RSYNC?
Rsync is a fast and extraordinarily versatile file copying tool for both remote and local files.
Rsync uses a delta-transfer algorithm which provides a very fast method for bringing remote files into sync. It does this by sending just the differences in the files across the link, without requiring that both sets of files are present at one of the ends of the link beforehand. At first glance this may seem impossible because the calculation of diffs between two files normally requires local access to both files.
A technical report describing the rsync algorithm is included with this package.
USAGE
Basically you use rsync just like scp, but rsync has many additional options. To get a complete list of supported options type:
rsync --help
See the manpage for more detailed information.
BUILDING AND INSTALLING
If you need to build rsync yourself, check out the INSTALL page for information on what libraries and packages you can use to get the maximum features in your build.
SETUP
Rsync normally uses ssh or rsh for communication with remote systems. It does not need to be setuid and requires no special privileges for installation. You must, however, have a working ssh or rsh system. Using ssh is recommended for its security features.
Alternatively, rsync can run in `daemon' mode, listening on a socket. This is generally used for public file distribution, although authentication and access control are available.
To install rsync, first run the "configure" script. This will create a Makefile and config.h appropriate for your system. Then type "make".
Note that on some systems you will have to force configure not to use gcc because gcc may not support some features (such as 64 bit file offsets) that your system may support. Set the environment variable CC to the name of your native compiler before running configure in this case.
Once built put a copy of rsync in your search path on the local and remote systems (or use "make install"). That's it!
RSYNC DAEMONS
Rsync can also talk to "rsync daemons" which can provide anonymous or authenticated rsync. See the rsyncd.conf(5) manpage for details on how to setup an rsync daemon. See the rsync(1) manpage for info on how to connect to an rsync daemon.
WEB SITE
For more information, visit the main rsync web site.
You'll find a FAQ list, downloads, resources, HTML versions of the manpages, etc.
MAILING LISTS
There is a mailing list for the discussion of rsync and its applications that is open to anyone to join. New releases are announced on this list, and there is also an announcement-only mailing list for those that want official announcements. See the mailing-list page for full details.
BUG REPORTS
The bug-tracking web page has full details on bug reporting.
That page contains links to the current bug list, and information on how to do a good job when reporting a bug. You might also like to try searching the Internet for the error message you've received, or looking in the mailing list archives.
To send a bug report, follow the instructions on the bug-tracking page of the web site.
Alternately, email your bug report to rsync@lists.samba.org.
For security issues please email details of the issue to rsync.project@gmail.com.
GIT REPOSITORY
If you want to get the very latest version of rsync direct from the source code repository, then you will need to use git. The git repo is hosted on GitHub and on Samba's site.
See the download page for full details on all the ways to grab the source.
COPYRIGHT
Rsync was originally written by Andrew Tridgell and Paul Mackerras. Many people from around the world have helped to maintain and improve it.
Special thanks go to Wayne Davison, who maintained rsync from 2004 to 2024.
Rsync may be used, modified and redistributed only under the terms of the GNU General Public License, found in the file COPYING in this distribution, or at the Free Software Foundation.