More tweaks for Actions.

[rsync.git] / support / rrsync.1.md

diff --git a/support/rrsync.1.md b/support/rrsync.1.md
index a7365323277aa8c90abe92437f63808003c6b3f6..5f33930e28a4c5e7a2590a45faa31859e25b3274 100644 (file)
--- a/support/rrsync.1.md
+++ b/support/rrsync.1.md
@@ -5,7 +5,7 @@ rrsync - a script to setup restricted rsync users via ssh logins
 ## SYNOPSIS
 
 ```
-rrsync [-ro|-rw] [-munge] [-no-del] [-no-lock] DIR
+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
@@ -22,6 +22,10 @@ transfer in one of two easy ways:
 * forcing the running of the rrsync script
 * 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:
@@ -81,6 +85,11 @@ The remainder of this manpage is dedicated to using the rrsync script.
 
     Avoid the single-run (per-user) lock check.  Useful with [`-munge`](#opt).
 
+0.  `-no-overwrite`
+
+    Enforce `--ignore-existing` on the server. Prevents overwriting existing
+    files when the server is the receiver.
+
 0.  `-help`, `-h`
 
     Output this help message and exit.
@@ -107,6 +116,26 @@ 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:
@@ -134,7 +163,7 @@ rsync is distributed under the GNU General Public License.  See the file
 [COPYING](COPYING) for details.
 
 An rsync web site is available at <https://rsync.samba.org/> and its github
-project is <https://github.com/WayneD/rsync>.
+project is <https://github.com/RsyncProject/rsync>.
 
 ## AUTHOR