use app-private path for home/ssh directory by default, and make a menu

option to Copy App-private Path

NOTES

@@ -621,9 +621,30 @@ READ_EXTERNAL_STORAGE, so long as I explicitly request
 WRITE_EXTERNAL_STORAGE.
 
 
-XXX - make sure to create the app-private files/ on first startup
-XXX - add options menu "copy app-private path", or something
-XXX - change default from /sdcard/ssh to app-private/files for new installs, or something
+May 19, 2018.
+
+Michael Mess wrote to let me know that he can't use authorized_keys file
+because the /sdcard/ssh/authorized_keys file is group-readwritable.  I
+know regular OpenSSH on a PC does complain if the authorized_keys file is
+world-writable, so this made sense to me.  He says it is a security flaw,
+but really, it is not, because any app that can run code and write to
+/sdcard/ssh already has all of the permissions that SimpleSSHD has
+(except network, but whatever) -- it isn't escalation, just a horizontal
+spreading.
+
+He suggested moving the SSH config into app-private, which is something
+I've been toying with anyways.
+
+So after some internal debate, I decided to do two changes:
+
+  * add "Copy app-private path" to the options menu, which brings up a
+    dialog showing the app-private path, with an option "Copy" to put it
+    in the clipboard.
+  * make the default for new installs for "home" and "path" be the
+    app-private dir
+
+I look forward to seeing if anyone complains about it.
+
 
 XXX - upgrade project.properties to android-26
 XXX - call checkSelfPermission/requestPermission to get WRITE_EXTERNAL_STORAGE

doc/index.html

@@ -29,8 +29,8 @@ Port 2222
 </pre>
 <li> Launch SimpleSSHD, and in Settings enable "Start on Boot", then
 manually start it for the first time.
-<li> Create <tt>/sdcard/ssh/authorized_keys</tt>
-<li> Optionally make <tt>/sdcard/ssh/.profile</tt>
+<li> Create <tt>authorized_keys</tt> in the home directory
+<li> Optionally make <tt>.profile</tt>
 </ul>
 
 <p>If SimpleSSHD does not find an <tt>authorized_keys</tt> file when a
@@ -45,6 +45,15 @@ file.</p>
 is supported.  If you screw up your <tt>authorized_keys</tt> file, use
 the options menu (upper right) -> Reset Keys.</p>
 
+<p>The default home directory is now the app-private directory, which
+will generally be something like
+<tt>/data/data/org.galexander.sshd/files</tt>, but may vary depending on
+your device.  Use options menu -> Copy App-private Path to view the path
+or copy it onto the clipboard.  A nice feature of the app-private
+directory is it generally supports the full range of Unix of file
+permissions, including execute!  A disadvantage is that these files all
+disappear if you uninstall SimpleSSHD.</p>
+
 <p>Once you get setup, you may want BusyBox.  Check out
 <a href="https://play.google.com/store/apps/details?id=org.galexander.busybox">SimpleBusyBox</a>.</p>
 
@@ -77,8 +86,10 @@ and then click "QUIT" when you are done.</dd>
 greater than 1024 (because SimpleSSHD does not have root).</dd>
 
 <dt>SSH Path</dt>
-<dd>Path for general dropbear files, which defaults to
-<tt>/sdcard/ssh</tt>.  Most importantly, this is where
+<dd>Path for general dropbear files, which now defaults to
+the app-private directory (usually something like
+<tt>/data/data/org.galexander.sshd/files</tt>).
+Most importantly, this is where
 <tt>authorized_keys</tt> 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 <tt>/sdcard</tt>.</dd>
@@ -106,8 +117,9 @@ SuperSU.</dd>
 
 <dt>Home Directory</dt>
 <dd>The login shell's home directory, which also defaults
-to <tt>/sdcard/ssh</tt>.  This is where your ssh session starts out, and is
-where <tt>.profile</tt> will be found if it is present.</dd>
+to the app-private directory.
+This is where your ssh session starts out, and is where <tt>.profile</tt>
+will be found if it is present.</dd>
 
 <dt>Extra Commandline</dt>
 <dd>You can specify additional commandline options for dropbear server.
@@ -158,6 +170,8 @@ harmless.
 <h2>Change Log</h2>
 
 <ul>
+<li> <b>2018/05/19 Version 19:</b> Use the app-private directory by
+default on new installs for the SSH/home dir.
 <li> <b>2018/05/16 Version 18:</b> Use correct idiom for <tt>su</tt> as a
 login shell (so busybox <tt>su</tt> can work).  Add environment variables
 to settings.

res/menu/main_menu.xml

@@ -3,6 +3,8 @@
     <item android:id="@+id/settings"
           android:icon="@android:drawable/ic_menu_manage"
           android:title="Settings" />
+    <item android:id="@+id/copypriv"
+          android:title="Copy App-private Path" />
     <item android:id="@+id/resetkeys"
           android:icon="@android:drawable/ic_secure"
           android:title="Reset Keys" />

res/xml/preferences.xml

@@ -24,7 +24,7 @@
 	android:key="path"
 	android:title="SSH Path"
 	android:summary="Location of misc dropbear files (put authorized_keys here)."
-	android:defaultValue="/sdcard/ssh" />
+	android:defaultValue="/xxx" />
     <EditTextPreference
 	android:key="shell"
 	android:title="Login Shell"
@@ -38,7 +38,7 @@
 	android:key="home"
 	android:title="Home Directory"
 	android:summary="Default directory after login (put .profile here)."
-	android:defaultValue="/sdcard/ssh" />
+	android:defaultValue="/xxx" />
     <EditTextPreference
 	android:key="extra"
 	android:title="Extra Commandline"

src/org/galexander/sshd/Prefs.java

@@ -10,6 +10,7 @@ public class Prefs {
 	public static void init(Context c) {
 		if (pref == null) {
 			pref = PreferenceManager.getDefaultSharedPreferences(c);
+			set_defaults();
 		}
 	}
 
@@ -35,13 +36,13 @@ public class Prefs {
 		return ret;
 	}
 	public static String get_path() {
-		return pref.getString("path", "/sdcard/ssh");
+		return pref.getString("path", SimpleSSHD.app_private);
 	}
 	public static String get_shell() {
 		return pref.getString("shell", "/system/bin/sh");
 	}
 	public static String get_home() {
-		return pref.getString("home", "/sdcard/ssh");
+		return pref.getString("home", SimpleSSHD.app_private);
 	}
 	public static String get_extra() {
 		return pref.getString("extra", "");
@@ -50,7 +51,21 @@ public class Prefs {
 		return pref.getString("env", "");
 	}
 
-	public static SharedPreferences.Editor edit() {
-		return pref.edit();
+	/* NB - other defaults can be filled in by either Prefs or Settings as
+	 * needed */
+	private static void set_defaults() {
+		boolean need_path = (pref.getString("path", null) == null);
+		boolean need_home = (pref.getString("home", null) == null);
+		if (!need_path && !need_home) {
+			return;
+		}
+		SharedPreferences.Editor edit = pref.edit();
+		if (need_path) {
+			edit.putString("path", SimpleSSHD.app_private);
+		}
+		if (need_home) {
+			edit.putString("home", SimpleSSHD.app_private);
+		}
+		edit.commit();
 	}
 };

src/org/galexander/sshd/SimpleSSHD.java

@@ -7,13 +7,15 @@ import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.Intent;
 import android.content.DialogInterface;
-import android.widget.CheckBox;
-import android.widget.EditText;
-import android.widget.TextView;
-import android.widget.Button;
+import android.text.ClipboardManager;
 import android.view.View;
 import android.view.Menu;
 import android.view.MenuItem;
+import android.widget.Button;
+import android.widget.CheckBox;
+import android.widget.EditText;
+import android.widget.TextView;
+import android.widget.Toast;
 import android.net.Uri;
 import java.io.File;
 import java.io.FileReader;
@@ -30,10 +32,12 @@ public class SimpleSSHD extends Activity
 	private Button startstop_view;
 	private TextView ip_view;
 	public static SimpleSSHD curr = null;
+	public static String app_private = null;
 	private UpdaterThread updater = null;
 
 	public void onCreate(Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
+		app_private = getFilesDir().toString();
 		Prefs.init(this);
 		setContentView(R.layout.main);
 		log_view = (EditText)findViewById(R.id.log);
@@ -74,6 +78,9 @@ public class SimpleSSHD extends Activity
 			case R.id.settings:
 				startActivity(new Intent(this, Settings.class));
 				return true;
+			case R.id.copypriv:
+				copy_app_private();
+				return true;
 			case R.id.resetkeys:
 				reset_keys();
 				return true;
@@ -237,6 +244,32 @@ public class SimpleSSHD extends Activity
 		return ret;
 	}
 
+	private void copy_app_private() {
+		new AlertDialog.Builder(this)
+		  .setCancelable(true)
+		  .setPositiveButton("OK",
+			new DialogInterface.OnClickListener() {
+				public void onClick(DialogInterface di,
+					int which) { }
+			})
+		  .setNegativeButton("Copy",
+			new DialogInterface.OnClickListener() {
+				public void onClick(DialogInterface di,
+					int which) {
+					ClipboardManager cl = (ClipboardManager)
+						getSystemService(
+						Context.CLIPBOARD_SERVICE);
+					if (cl != null) {
+						cl.setText(app_private);
+					}
+				}
+			})
+		  .setIcon(android.R.drawable.ic_dialog_info)
+		  .setTitle("App-private path")
+		  .setMessage(app_private)
+		  .show();
+	}
+
 	private void do_reset_keys() {
 		new File(Prefs.get_path(), "authorized_keys").delete();
 	}