Secure Mail Shell

Secure Mail Shell (or smash for short) is a utility for securely executing commands on a remote system via email.

I wrote smash to ease administration of a remote system that is only intermittently connected to the internet. Although using ssh was perfectly feasible, ssh depends on the target system being accessible right here and now. And the remote system was almost never connected when I wanted to log in.

My solution (or rather: work-around?) for this was to write smash, which enables me to queue commands for later execution on the remote system (via email), and later receive the output (again via email). Email in both directions is encrypted & signed using GnuPG to provide a secure, authentificated communication.

Since the commands will execute unattended, this is only useful for non-interactive commands. Because of this (and other factors), it should not be considered as a replacement for ssh.

Practically, it is a bit like using at(1), but remotely and without being able to predict when the commands will be executed.

Warning

smash is currently in the late alpha stage. It is probably safe to assume that it contains multiple security holes and bugs. Use at your own risk.

License

smash is released under the GNU General Public License, version 2.

Download

Under Debian GNU/Linux all you have to do is to add these lines to /etc/apt/sources.list (preferably near the end of the file):

deb     http://www.karl.jorgensen.com/debian stable main contrib 
deb-src http://www.karl.jorgensen.com/debian stable main contrib

and run:

# apt-get update

followed by:

# apt-get install package-name

Apt will take care of the download, dependencies etc.

If you prefer to download the files by hand (if you're not using Debian and apt, then you'll have to), then you can find them here. And you will have to resolve any dependencies and conflicts by hand too.

Bugs

If you (God Forbid!) find bugs in my software, then I would very much like to know about it:

• Read www.chiark.greenend.org.uk/~sgtatham/bugs.html first. The author has stated things better than I could have hoped to.

• Email me a bug report.