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-Introduction
-------------
-
-Welcome to [schsh][SCHSH], a schroot-based shell.
-
-Its purpose is simple: I want to provide users with scp, sftp and rsync access
-to my server, such that they can only operate in a certain subdirectory.
-There are plenty of solutions for this problem out there, and all have one
-drawback in common:
-You need to manually set up a bunch of chroots, and copy the files needed for
-scp, sftp and rsync into them.
-
-I didn't like that, so here is my alternative solution: Use schroot for the
-chroots. This gets OpenSSH out of the loop when it comes to chroots, instead
-the relevant users get a special shell (schsh, the schroot shell). That shell
-essentially calls schroot and runs the desired command inside the chroot. It
-also provides some very basic command restriction (so that you can allow scp,
-sftp and rsync and nothing else).
-
-Unfortunately, this still needs a (s)chroot to be set up for each user, but at
-least no files have to be copied: Instead, schroot is configured to bind-mount
-the relevant system folders into the user-chroot. Hence no files are
-duplicated, and system updates to the relevant tools are applied inside the
-chroots automatically. For additional hardening, these bind-mounts are
-configured to be read-only and no-setuid, while the only user-writeable folder
-is no-exec.
-
-[SCHSH]: http://www.ralfj.de/projects/schsh/
-
-Setup
------
-
-Before you start, make sure you have the dependencies installed:
-schsh needs [Python 3][PYTHON] (I tested it with version 3.2) and
-[schroot][SCHROOT] (version 1.6 or newer).
-
-Installation is simple: Just run ```make install```. That will copy some files
-to ```/usr/local/bin```, and some configuration to ```/etc/schroot/```.
-Before you create any users, make sure the directory ```/var/lib/schsh``` and a
-group called ```schsh``` exist.
-
-You should also set up SSH to disallow port forwarding for users controlled by
-schsh. See ```sshd_config``` in the source folder for an appropriate snippet
-of OpenSSH configuration.
-
-Before you can set up schsh for a user, you need to create it first:
-
- adduser sandboxed --disabled-password
-
-Any existing user can be "sandboxed" by running
-
- makeschsh sandboxed
-
-This does the following:
-
-* Change the user's shell to ```/usr/local/bin/schsh```
-* Create a chroot base in ```/var/lib/schsh/sandboxed``` with some empty
- subfolders as well as ```/etc/passwd``` and ```/etc/group``` containing
- only root, this user and the ```schsh``` group
-* Add the user to the ```schsh``` group
-* Set up a schroot called ```schsh-sandboxed``` for the given folder, and an
- fstab file in ```/etc/schroot/schsh``` used by this schroot
-
-Now if the user logs in via SSH, ```/usr/local/bin/schsh``` will be executed,
-and it will lock the user into the schroot ```schsh-sandboxed```. It will
-only see some system folders and a folder called ```/data``` mapped to
-```/home/sandboxed/data```. If you want to give the user access to more
-folders, or another folder, simply edit ```/etc/schroot/schsh/sandboxed.fstab```.
-The only part of schsh writing any files is ```makeschsh```, so you can change
-the users' schroot configurations at your will.
-
-[PYTHON]: http://www.python.org
-[SCHROOT]: https://wiki.debian.org/Schroot
-
-Configuration
--------------
-
-There is not much to configure at the moment. However, there are some
-global variables at the top of both ```schsh``` and ```makeschsh``` to
-change the base paths, and to tell which commands are allowed.
-
-Source, License
----------------
-
-You can find the sources in the [git repository][GIT]. They are provided under
-the [GPLv3][GPL3]. In addition, all files except for ```schsh-rrsync``` are
-provided under the [GPLv2][GPL2] or (at your option) any later version of the
-GPL.
-
-[GIT]: http://www.ralfj.de/git/schsh.git
-[GPL3]: https://www.gnu.org/licenses/gpl.html
-[GPL2]: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
-
-Contact
--------
-
-If you found a bug, or want to leave a comment, please send me a mail:
-```post AT ralfj DOT de```.
projects / schsh.git / blobdiff