SimpleSSHD

SimpleSSHD is an SSH2 server based on dropbear that supports scp, sftp, and rsync. It only supports public-key based authentication (no password/interactive auth). It does not use root, which means it must listen on a port over 1024 (defaults to port 2222).

Quick start

• Install SimpleSSHD.
• Either:
  • Go to SimpleSSHD -> Menu (upper right) -> Authorized Keys, and either cut and paste an SSH public key or "Fetch" one via HTTP.
  • OR: Make a directory /sdcard/ssh, and put an authorized_keys file in that directory.
• On any computer which will connect to your Android device, set the port to 2222. With OpenSSH, this can be done by putting these lines in ~/.ssh/config:

  Host myphone
  Port 2222
  

• Launch SimpleSSHD, and in Settings enable "Start on Boot", and manually start it for the first time.
• You might want to put a .profile in /sdcard/ssh, too.

Voila! You can use ssh/scp/sftp/rsync to talk to your Android device!

Settings

Generally speaking, you must re-start the SimpleSSHD service for any of these settings to take effect.

Start on Boot

Automatically start the SimpleSSHD service when the phone powers on.

Foreground Service

Run the SimpleSSHD service as an Android "foreground service." This means a notification will be displayed for the service (you might be able to block the notification by long tapping the notification). On newer versions of Android (since Marshmallow), this may also make SimpleSSHD more responsive if the phone has been in Doze mode. It does not seem to increase battery consumption much.

Start on Open

Run the SimpleSSHD service whenever the app is launched. The "STOP" button will be replaced with a "QUIT" button that stops the service and exits the app. This is useful if you want to only run the service when you really need it -- start the app to start listening for connections, and then click "QUIT" when you are done.

Port Number

This is the port number that SimpleSSHD will listen on. It must be greater than 1024 (because SimpleSSHD does not have root).

SSH Path

Path for general dropbear files, which defaults to /sdcard/ssh. Most importantly, this is where authorized_keys is found. It is also where host keys wind up (they are created on demand), and where temporary files go. This path should probably be under /sdcard.

Login Shell

Path to the command shell. The default Android shell is /system/bin/sh, but you may prefer to use the one that comes with busybox or whatever. If you set it to the su binary (i.e., /system/xbin/su), then scp, sftp, and rsync will run as root and should be able to access files outside of the sdcard.

Buffer hack for rsync+SuperSU

A bug in SuperSU interacts with an infelicity in rsync to cause an occasional deadlock. This is a real pain because I use SuperSU+rsync for system-wide backups, which will always eventually trigger the deadlock. To work around this, there is a "Buffer hack" option that should be enabled if you use rsync with SuperSU. It adds a miniscule overhead to rsync, but isn't harmful even if you aren't using SuperSU.

Home Directory

The login shell's home directory, which also defaults to /sdcard/ssh. This is where your ssh session starts out, and is where .profile will be found if it is present.

Extra Commandline

You can specify additional commandline options for dropbear server. The options which are hardcoded are:

-R -F -p :portno

You can use \ or " to escape characters in this commandline.

Change Log

• 2016/10/xx Version 13: Support foreground service (fewer stalls with newer Android). Add "Start on Open" mode.
• 2016/08/08 Version 1.11: Fix stall initializing random number generator.
• 2016/07/22 Version 1.10: Enable TCP port forwarding.
• 2016/07/04 Version 1.9: Restart sshd if the system kills it.
• 2016/06/21 Version 1.8: sftp, rsync, and scp now work on files bigger than 2GB.
• 2016/06/19 Version 1.7: Don't clear environment variables (so you can use am or pm more easily). Add "Authorized Keys" menu option to help maintain the authorized_keys file.
• 2016/06/12 Version 1.6: Fix typo that broke scp/sftp/rsync in version 1.5.
• 2016/06/11 Version 1.5: SuperSU+rsync hack now limits the buffer size to 1MB.
• 2015/11/23 Version 1.4: Don't abort if IP address lookup fails, and make proper "About" menu.
• 2015/06/21 Version 1.3: Hack to make rsync work with SuperSU.
• 2015/01/18 Version 1.2: Displays the IP address it's listening on.
• 2014/12/29 Version 1.1: Works with Lollipop now.
• 2014/12/22 Version 1.0: Initial public release.

About

SimpleSSHD is built using parts from open source projects: Dropbear SSH, openssh (for scp and sftp-server), and rsync. Those projects in turn are built on other projects. A lot of people's work is represented here, and very little of my own.

But if you find bugs/infelicities, it's probably my fault, so email me:

To get the source:

git clone http://galexander.org/git/simplesshd.git