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234 lines
9.8 KiB
HTML
234 lines
9.8 KiB
HTML
<html><head><title>SimpleSSHD</title>
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<meta name="HandheldFriendly" content="true"/>
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<style type="text/css">
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pre {
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</head>
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<body>
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<p style="float:right; width:30%;"><img style="width:100%;" src="icon.png"></p>
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<h1>SimpleSSHD</h1>
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<p>SimpleSSHD is an SSH2 server based on dropbear that supports scp,
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sftp, and rsync. It only supports public-key based authentication (no
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password/interactive auth except for bootstrapping). It does not use
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root, which means it must listen on a port over 1024 (defaults to port
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2222).</p>
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<h2>Quick start</h2>
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<ul>
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<li> Install SimpleSSHD.
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<li> On any computer which will connect to your Android device, set the
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port to 2222. With OpenSSH, this can be done by putting these lines in
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<tt>~/.ssh/config</tt>:
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<pre>
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Host myphone
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Port 2222
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</pre>
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<li> Launch SimpleSSHD, and in Settings enable "Start on Boot", then
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manually start it for the first time.
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<li> Create <tt>authorized_keys</tt> in the home directory (do not use <tt>ssh-copy-id</tt>)
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<li> Optionally make <tt>.profile</tt>
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</ul>
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<p>If SimpleSSHD does not find an <tt>authorized_keys</tt> file when a
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client connects, then it generates a single-use password at that time and
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displays it in the console log. So the procedure to login the first time
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is to initiate the ssh connection, then look at the phone and type in the
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password that is on the screen in the SimpleSSHD app. It is recommended
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to use that shell session to install the <tt>authorized_keys</tt>
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file.</p>
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<p>Once <tt>authorized_keys</tt> exists, only public key authentication
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is supported. If you screw up your <tt>authorized_keys</tt> file, use
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the options menu (upper right) -> Reset Keys.</p>
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<p>The default home directory is now the app-private directory, which
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will generally be something like
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<tt>/data/data/org.galexander.sshd/files</tt>, but may vary depending on
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your device. Use options menu -> Copy App-private Path to view the path
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or copy it onto the clipboard. A nice feature of the app-private
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directory is it generally supports the full range of Unix file
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permissions, including execute! A disadvantage is that these files all
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disappear if you uninstall SimpleSSHD.</p>
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<p>Once you get setup, you may want BusyBox. Check out
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<a href="https://play.google.com/store/apps/details?id=org.galexander.busybox">SimpleBusyBox</a>.</p>
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<h2>Settings</h2>
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<p>Generally speaking, you must re-start the SimpleSSHD service for any
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of these settings to take effect.</p>
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<dl>
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<dt>Start on Boot</dt>
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<dd>Automatically start the SimpleSSHD service when the phone powers on.</dd>
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<dt>Start on Open</dt>
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<dd>Run the SimpleSSHD service whenever the app is launched. The "STOP"
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button will be replaced with a "QUIT" button that stops the service and
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exits the app. This is useful if you want to only run the service when
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you really need it -- start the app to start listening for connections,
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and then click "QUIT" when you are done.</dd>
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<dt>Foreground Service</dt>
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<dd>Run the SimpleSSHD service as an Android "foreground service." This
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means a notification will be displayed for the service (you might be able
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to block the notification by long tapping the notification).
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On newer versions of Android (since Marshmallow), this may also make
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SimpleSSHD more responsive if the phone has been in Doze mode. It does
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not seem to increase battery consumption much.</dd>
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<dt>Port Number</dt>
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<dd>This is the port number that SimpleSSHD will listen on. It must be
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greater than 1024 (because SimpleSSHD does not have root).</dd>
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<dt>Buffer hack for rsync+SuperSU</dt>
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<dd>A bug in SuperSU interacts with an infelicity in rsync to cause an
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occasional deadlock. This is a real pain because I use SuperSU+rsync
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for system-wide backups, which will always eventually trigger the
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deadlock. To work around this, there is a "Buffer hack" option that
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should be enabled if you use rsync with SuperSU. It adds a miniscule
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overhead to rsync, but isn't harmful even if you aren't using
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SuperSU.</dd>
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<dt>Extra Commandline</dt>
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<dd>You can specify additional commandline options for dropbear server.
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The options which are hardcoded are:
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<blockquote><pre>-R -F -p :portno</pre></blockquote>
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You can use <tt>\</tt> or <tt>"</tt> to escape characters in this
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commandline.</dd>
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<dt>Environment Variables</dt>
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<dd>You can specify environment variables to define before executing the
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shell. There is one variable per line, with a
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"<em>name</em><tt>=</tt><em>value</em>" format.
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A common use would be
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"<tt>ENV=>/data/data/org.galexander.sshd/files/.profile</tt>",
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if your device has a
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build of <tt>mksh</tt> that does not execute a <tt>.profile</tt>
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automatically.</dd>
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<dt>SSH Path</dt>
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<dd>Path for general dropbear files, which now defaults to
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the app-private directory (usually something like
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<tt>/data/data/org.galexander.sshd/files</tt>).
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Most importantly, this is where
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<tt>authorized_keys</tt> is found. It is also where host keys wind up
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(they are created on demand), and where temporary files go. Other than
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the app-private directory, it may go under <tt>/sdcard</tt>.</dd>
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<dt>Home Directory</dt>
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<dd>The login shell's home directory, which also defaults
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to the app-private directory.
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This is where your ssh session starts out, and is where <tt>.profile</tt>
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will be found if it is present.</dd>
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<dt>Login Shell</dt>
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<dd>Path to the command shell. The default Android shell is
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<tt>/system/bin/sh</tt>, but you may prefer to use the one that comes with
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busybox or whatever. If you set it to the su binary (i.e.,
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<tt>/system/xbin/su</tt>, or maybe <tt>/su/bin/su</tt>),
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then scp, sftp, and rsync will run as root and
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should be able to access files outside of <tt>/sdcard</tt>. If the name
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of the shell contains "<tt>su</tt>" in it, instead of putting
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"<tt>-</tt>" before <tt>argv[0]</tt> to indicate the login shell,
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SimpleSSHD puts "<tt>-</tt>" as <tt>argv[1]</tt>. That is, a regular
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login shell would be invoked as "<tt>-sh</tt>", but su will be invoked as
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"<tt>su -</tt>".</dd>
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<h2>Frequently Asked Questions</h2>
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<p>Here are some common complaints:</p>
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<ul>
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<li> Writing to an SD card is not generally possible -- your mileage may
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vary. Modern Android (since about Kit Kat) only allows write access to
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an SD card through the Android Java API, but shell commands usually use
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Unix APIs (POSIX, C). I don't know a work-around. Most phones let you
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write to <tt>/sdcard</tt>, but it's often in the phone's internal memory.
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<li> <tt>rsync</tt> will do too much work for an update, because there is
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usually no way to update the ctime, mtime, or atime on files in
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<tt>/sdcard</tt>. Use <tt>rynsc --size-only</tt>, and it will compare
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the file sizes instead of the modification time.
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<li> For the same reason, <tt>rsync -a</tt> will generally fail. Use
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<tt>rsync -r</tt> instead.
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<li> "<tt>Not backgrounding</tt>" is just the string that dropbear
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outputs when it isn't asked to <tt>fork()</tt> when it starts up -- it's
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harmless.
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<li> If you really must specify which IP to listen on, consider setting
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<b>Port Number</b> to 22 (which will fail and be ignored), and then add
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<tt>-p 192.168.1.123:2222</tt> to <b>Extra Commandline</b>.
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<li> <tt>ed25519</tt> keys are not supported by Dropbear (yet). Use a
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regular <tt>rsa</tt> key for greatest compatibility.
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<li> Do not use <tt>ssh-copy-id</tt>, it will try to put the
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<tt>authorized_keys</tt> file in the wrong place.
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</ul>
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<h2>Change Log</h2>
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<ul>
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<li> <b>2018/05/19 Version 19:</b> Use the app-private directory by
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default on new installs for the SSH/home dir. Organize settings. Fix
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black-on-black text on some devices.
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<li> <b>2018/05/16 Version 18:</b> Use correct idiom for <tt>su</tt> as a
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login shell (so busybox <tt>su</tt> can work). Add environment variables
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to settings.
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<li> <b>2018/03/24 Version 17:</b> Add native x86 support.
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<li> <b>2017/10/28 Version 16:</b> Fix rsync on Android 8.0 (Oreo).
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<li> <b>2016/10/17 Version 15:</b> Fix crash on pre-Nougat versions of Android.
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<li> <b>2016/10/16 Version 14:</b> Support single-use passwords for
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bootstrapping.
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<li> <b>2016/10/16 Version 13:</b> Support foreground service (fewer
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stalls with newer Android). Add "Start on Open" mode.
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<li> <b>2016/08/08 Version 1.11:</b> Fix stall initializing random number generator.
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<li> <b>2016/07/22 Version 1.10:</b> Enable TCP port forwarding.
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<li> <b>2016/07/04 Version 1.9:</b> Restart sshd if the system kills it.
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<li> <b>2016/06/21 Version 1.8:</b> sftp, rsync, and scp now work on
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files bigger than 2GB.
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<li> <b>2016/06/19 Version 1.7:</b> Don't clear environment variables (so
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you can use <tt>am</tt> or <tt>pm</tt> more easily). Add "Authorized
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Keys" menu option to help maintain the <tt>authorized_keys</tt> file.
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<li> <b>2016/06/12 Version 1.6:</b> Fix typo that broke scp/sftp/rsync in
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version 1.5.
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<li> <b>2016/06/11 Version 1.5:</b> SuperSU+rsync hack now limits the
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buffer size to 1MB.
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<li> <b>2015/11/23 Version 1.4:</b> Don't abort if IP address lookup fails, and make proper "About" menu.
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<li> <b>2015/06/21 Version 1.3:</b> Hack to make rsync work with SuperSU.
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<li> <b>2015/01/18 Version 1.2:</b> Displays the IP address it's listening on.
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<li> <b>2014/12/29 Version 1.1:</b> Works with Lollipop now.
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<li> <b>2014/12/22 Version 1.0:</b> Initial public release.
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</ul>
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<h2>About</h2>
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<p>SimpleSSHD is built using parts from open source projects:
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<a href="https://matt.ucc.asn.au/dropbear/dropbear.html">Dropbear SSH</a>,
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<a href="http://www.openssh.com/">openssh</a> (for scp and sftp-server),
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and <a href="http://rsync.samba.org/">rsync</a>. Those projects in turn
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are built on other projects. A lot of people's work is represented here,
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and very little of my own.</p>
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<p>But if you find bugs/infelicities, it's probably my fault, so email
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me:<br>
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<img src="/email.png"></p>
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<p>To get the source:</p>
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<pre>git clone http://galexander.org/git/simplesshd.git</pre>
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<p>Direct APK download:
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<a href="SimpleSSHD-19.apk">SimpleSSHD-19.apk</a> - last version to target SDK 11, Android 3.0 Honeycomb.</p>
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</body></html>
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