Add JSch (SFTP) debug logging

-App Settings->Log-File for Debugging->SFTP debug logging
-Logs to android log (logcat) if log file is not enabled
-Logs to Kp2a log file if it is enabled
-Logs are tagged as "KP2AJFS[JSch]"
-When enabled, logs ALL levels (DEBUG+).

NOTE: Sensitive SSH connection information may be logged!!

src/KeePassLib2Android/Kp2aLog.cs

@@ -58,12 +58,12 @@ namespace keepass2android
 
 		}
 
-		private static string LogFilename
+		public static string LogFilename
 		{
 			get { return Application.Context.FilesDir.CanonicalPath +"/keepass2android.log"; }
 		}
 
-		private static bool LogToFile
+		public static bool LogToFile
 		{
 			get
 			{

src/java/JavaFileStorage/app/src/main/java/keepass2android/javafilestorage/Kp2aJSchLogger.java

@@ -0,0 +1,93 @@
+package keepass2android.javafilestorage;
+
+import android.util.Log;
+
+import com.jcraft.jsch.Logger;
+
+import java.io.FileWriter;
+import java.io.PrintWriter;
+import java.util.Map;
+
+public class Kp2aJSchLogger implements Logger {
+
+    private static final String PREFIX = "KP2AJFS[JSch]";
+
+    private interface ILogger {
+        void log(String message);
+    }
+
+    private static final class LogEntry {
+        private final String levelTag;
+        private final ILogger logger;
+
+        LogEntry(String levelTag, ILogger logger) {
+            this.levelTag = levelTag;
+            this.logger = logger;
+        }
+    }
+    private static final ILogger DEBUG = msg -> Log.d(PREFIX, msg);
+    private static final LogEntry DEBUG_ENTRY = new LogEntry("D", DEBUG);
+    private static final ILogger ERROR = msg -> Log.e(PREFIX, msg);
+    private static final LogEntry DEFAULT_ENTRY = DEBUG_ENTRY;
+
+    private static final Map<Integer, LogEntry> loggers = Map.of(
+            Logger.DEBUG, DEBUG_ENTRY,
+            Logger.INFO, new LogEntry("I", msg -> Log.i(PREFIX, msg)),
+            Logger.WARN, new LogEntry("W", msg -> Log.w(PREFIX, msg)),
+            Logger.ERROR, new LogEntry("E", ERROR),
+            Logger.FATAL, new LogEntry("F", msg -> Log.wtf(PREFIX, msg))
+    );
+
+
+    private final String logFilename;
+
+    public Kp2aJSchLogger(String logFilename) {
+        this.logFilename = logFilename;
+    }
+
+    @Override
+    public boolean isEnabled(int level) {
+        return true;
+    }
+
+    @Override
+    public void log(int level, String message) {
+        if (isEnabled(level))
+            getLogger(level).log(message);
+    }
+
+    private ILogger getLogger(int level) {
+        LogEntry entry = loggers.get(level);
+        if (entry == null)
+            entry = DEFAULT_ENTRY;
+
+        ILogger logger;
+        if (logFilename != null) {
+            logger = createFileLogger(entry);
+        } else {
+            logger = entry.logger;
+        }
+
+        return logger;
+    }
+
+    private ILogger createFileLogger(LogEntry entry) {
+        try {
+            final PrintWriter p = new PrintWriter(new FileWriter(logFilename, true));
+            return msg -> {
+                try {
+                    String fullMsg = String.join(" ", entry.levelTag, PREFIX, msg);
+                    p.println(fullMsg);
+                } catch (Exception e) {
+                    ERROR.log(e.getMessage());
+                } finally {
+                    p.close();
+                }
+            };
+        } catch (Exception e) {
+            ERROR.log(e.getMessage());
+            return entry.logger;
+        }
+    }
+}
+

src/java/JavaFileStorage/app/src/main/java/keepass2android/javafilestorage/SftpStorage.java

@@ -375,6 +375,14 @@ public class SftpStorage extends JavaFileStorageBase {
 
 	}
 
+	public void setJschLogging(boolean enabled, String logFilename) {
+		if (enabled) {
+			JSch.setLogger(new Kp2aJSchLogger(logFilename));
+		} else {
+			JSch.setLogger(null);
+		}
+	}
+
 	private String createKeyPair(String key_filename) throws JSchException, IOException {
 		String public_key_filename = key_filename + ".pub";
 		File file = new File(key_filename);

src/keepass2android/Resources/values/config.xml

@@ -98,6 +98,7 @@
 	<string name="TrayTotp_SeedField_key">TrayTotp_SeedField_key</string>
 	<string name="TrayTotp_prefs_key">TrayTotp_prefs_key</string>
   <string name="DebugLog_key">DebugLog_key</string>
+  <string name="JSchDebug_key">JSchDebug_key</string>
   <string name="DebugLog_prefs_key">DebugLog_prefs_key</string>
   <string name="DebugLog_send_key">DebugLog_send</string>
   <string name="AutofillDisabledQueriesPreference_key">AutofillDisabledQueriesPreference_key</string>

src/keepass2android/Resources/values/strings.xml

@@ -680,6 +680,7 @@
 	<string name="TrayTotp_prefs">TrayTotp</string>
   <string name="DebugLog_prefs_prefs">Log-File for Debugging</string>
   <string name="DebugLog_title">Use log file</string>
+  <string name="JSchDebug_title">SFTP debug logging</string>
   <string name="DebugLog_summary">Write app output to a local log file</string>
   <string name="DebugLog_send">Send debug log...</string>
   

src/keepass2android/Resources/xml/preferences.xml

@@ -670,10 +670,17 @@
 							  android:defaultValue="false"
 							  android:title="@string/DebugLog_title"
 							  android:key="@string/DebugLog_key" />
+
       <Preference
                android:enabled="true"
                android:title="@string/DebugLog_send"
                android:key="@string/DebugLog_send_key" />
+      <CheckBoxPreference
+							android:enabled="true"
+							  android:persistent="true"
+							  android:defaultValue="false"
+							  android:title="@string/JSchDebug_title"
+							  android:key="@string/JSchDebug_key" />
     </PreferenceScreen>
     </PreferenceScreen>
 

src/keepass2android/settings/DatabaseSettingsActivity.cs

@@ -175,6 +175,7 @@ namespace keepass2android
 
             FindPreference(GetString(Resource.String.DebugLog_key)).PreferenceChange += OnDebugLogChanged;
             FindPreference(GetString(Resource.String.DebugLog_send_key)).PreferenceClick += OnSendDebug;
+            FindPreference(GetString(Resource.String.JSchDebug_key)).PreferenceChange += OnJSchDebugChanged;
 
             HashSet<string> supportedLocales = new HashSet<string>() { "en", "af", "ar", "az", "be", "bg", "ca", "cs", "da", "de", "el", "es", "eu", "fa", "fi", "fr", "gl", "he", "hr", "hu", "id", "in", "it", "iw", "ja", "ko", "ml", "nb", "nl", "nn", "no", "pl", "pt", "ro", "ru", "si", "sk", "sl", "sr", "sv", "tr", "uk", "vi", "zh" };
 
@@ -417,16 +418,31 @@ namespace keepass2android
 
 	    private void OnDebugLogChanged(object sender, Preference.PreferenceChangeEventArgs e)
 	    {
-		    if ((bool)e.NewValue)
+            if ((bool)e.NewValue)
-		    {
+                Kp2aLog.CreateLogFile();
-			    Kp2aLog.CreateLogFile();
-		    }
 		    else
-		    {
+                Kp2aLog.FinishLogFile();
-			    Kp2aLog.FinishLogFile();
-		    }
 
-	    }
+            bool jschLogEnable = PreferenceManager.GetDefaultSharedPreferences(Application.Context)
+                .GetBoolean(Application.Context.GetString(Resource.String.JSchDebug_key), false);
+            SetJSchLogging(jschLogEnable);
+        }
+
+        private void OnJSchDebugChanged(object sender, Preference.PreferenceChangeEventArgs e)
+        {
+            SetJSchLogging((bool)e.NewValue);
+        }
+
+        private void SetJSchLogging(bool enabled)
+        {
+            var sftpStorage = new Keepass2android.Javafilestorage.SftpStorage(Context);
+            string? logFilename = null;
+            if (Kp2aLog.LogToFile)
+            {
+                logFilename = Kp2aLog.LogFilename;
+            }
+            sftpStorage.SetJschLogging(enabled, logFilename);
+        }
 
 	    private void AlgorithmPrefChange(object sender, Preference.PreferenceChangeEventArgs preferenceChangeEventArgs)
 	    {