Use SSHJ for SSH public key authentication (#801)

14 files changed, 405 insertions, 350 deletions

diff --git a/app/src/main/java/com/zeapo/pwdstore/Application.kt b/app/src/main/java/com/zeapo/pwdstore/Application.kt
index d162e461..ec115639 100644
--- a/app/src/main/java/com/zeapo/pwdstore/Application.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/Application.kt
@@ -14,6 +14,8 @@ import androidx.preference.PreferenceManager
 import com.github.ajalt.timberkt.Timber.DebugTree
 import com.github.ajalt.timberkt.Timber.plant
 import com.haroldadmin.whatthestack.WhatTheStack
+import org.bouncycastle.jce.provider.BouncyCastleProvider
+import java.security.Security
 
 @Suppress("Unused")
 class Application : android.app.Application(), SharedPreferences.OnSharedPreferenceChangeListener {
@@ -29,6 +31,7 @@ class Application : android.app.Application(), SharedPreferences.OnSharedPrefere
         }
         prefs?.registerOnSharedPreferenceChangeListener(this)
         setNightMode()
+        setUpBouncyCastle()
     }
 
     override fun onTerminate() {
@@ -42,6 +45,25 @@ class Application : android.app.Application(), SharedPreferences.OnSharedPrefere
         }
     }
 
+    private fun setUpBouncyCastle() {
+        // Replace the Android BC provider with the Java BouncyCastle provider since the former does
+        // not include all the required algorithms.
+        // TODO: Verify that we are indeed using the fast Android-native implementation whenever
+        //  possible.
+        // Note: This may affect crypto operations in other parts of the application.
+        val bcIndex = Security.getProviders().indexOfFirst {
+            it.name == BouncyCastleProvider.PROVIDER_NAME
+        }
+        if (bcIndex == -1) {
+            // No Android BC found, install Java BC at lowest priority.
+            Security.addProvider(BouncyCastleProvider())
+        } else {
+            // Replace Android BC with Java BC, inserted at the same position.
+            Security.removeProvider(BouncyCastleProvider.PROVIDER_NAME)
+            Security.insertProviderAt(BouncyCastleProvider(), bcIndex + 1)
+        }
+    }
+
     private fun setNightMode() {
         AppCompatDelegate.setDefaultNightMode(when (prefs?.getString("app_theme", getString(R.string.app_theme_def))) {
             "light" -> MODE_NIGHT_NO
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/BaseGitActivity.kt b/app/src/main/java/com/zeapo/pwdstore/git/BaseGitActivity.kt
index fb7d7e82..c75f7ad3 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/BaseGitActivity.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/BaseGitActivity.kt
@@ -146,10 +146,11 @@ abstract class BaseGitActivity : AppCompatActivity() {
         }
         if (PasswordRepository.isInitialized)
             PasswordRepository.addRemote("origin", newUrl, true)
-        // HTTPS authentication sends the password to the server, so we must wipe the password when
-        // the server is changed.
-        if (previousUrl.isNotEmpty() && newUrl != previousUrl && protocol == Protocol.Https)
+        // When the server changes, remote password and host key file should be deleted.
+        if (previousUrl.isNotEmpty() && newUrl != previousUrl) {
             encryptedSettings.edit { remove("https_password") }
+            File("$filesDir/.host_key").delete()
+        }
         url = newUrl
         return GitUpdateUrlResult.Ok
     }
@@ -201,8 +202,7 @@ abstract class BaseGitActivity : AppCompatActivity() {
                     return
                 }
             }
-            op.executeAfterAuthentication(connectionMode, serverUser,
-                File("$filesDir/.ssh_key"), identity)
+            op.executeAfterAuthentication(connectionMode, serverUser, identity)
         } catch (e: Exception) {
             e.printStackTrace()
             MaterialAlertDialogBuilder(this).setMessage(e.message).show()
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/BreakOutOfDetached.kt b/app/src/main/java/com/zeapo/pwdstore/git/BreakOutOfDetached.kt
index 94ee0845..31c376eb 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/BreakOutOfDetached.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/BreakOutOfDetached.kt
@@ -62,10 +62,10 @@ class BreakOutOfDetached(fileDir: File, callingActivity: Activity) : GitOperatio
             .execute(*this.commands.toTypedArray())
     }
 
-    override fun onError(errorMessage: String) {
+    override fun onError(err: Exception) {
         MaterialAlertDialogBuilder(callingActivity)
             .setTitle(callingActivity.resources.getString(R.string.jgit_error_dialog_title))
-            .setMessage("Error occurred when checking out another branch operation $errorMessage")
+            .setMessage("Error occurred when checking out another branch operation ${err.message}")
             .setPositiveButton(callingActivity.resources.getString(R.string.dialog_ok)) { _, _ ->
                 callingActivity.finish()
             }.show()
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/CloneOperation.kt b/app/src/main/java/com/zeapo/pwdstore/git/CloneOperation.kt
index 32421d38..705566be 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/CloneOperation.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/CloneOperation.kt
@@ -34,43 +34,18 @@ class CloneOperation(fileDir: File, callingActivity: Activity) : GitOperation(fi
         return this
     }
 
-    /**
-     * sets the authentication for user/pwd scheme
-     *
-     * @param username the username
-     * @param password the password
-     * @return the current object
-     */
-    public override fun setAuthentication(username: String, password: String): CloneOperation {
-        super.setAuthentication(username, password)
-        return this
-    }
-
-    /**
-     * sets the authentication for the ssh-key scheme
-     *
-     * @param sshKey the ssh-key file
-     * @param username the username
-     * @param passphrase the passphrase
-     * @return the current object
-     */
-    public override fun setAuthentication(sshKey: File, username: String, passphrase: String): CloneOperation {
-        super.setAuthentication(sshKey, username, passphrase)
-        return this
-    }
-
     override fun execute() {
         (this.command as? CloneCommand)?.setCredentialsProvider(this.provider)
         GitAsyncTask(callingActivity, false, this, Intent()).execute(this.command)
     }
 
-    override fun onError(errorMessage: String) {
-        super.onError(errorMessage)
+    override fun onError(err: Exception) {
+        super.onError(err)
         MaterialAlertDialogBuilder(callingActivity)
             .setTitle(callingActivity.resources.getString(R.string.jgit_error_dialog_title))
             .setMessage("Error occurred during the clone operation, " +
                 callingActivity.resources.getString(R.string.jgit_error_dialog_text) +
-                errorMessage +
+                err.message +
                 "\nPlease check the FAQ for possible reasons why this error might occur.")
             .setPositiveButton(callingActivity.resources.getString(R.string.dialog_ok)) { _, _ -> }
             .show()
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/GitAsyncTask.java b/app/src/main/java/com/zeapo/pwdstore/git/GitAsyncTask.java
deleted file mode 100644
index 33e786a3..00000000
--- a/app/src/main/java/com/zeapo/pwdstore/git/GitAsyncTask.java
+++ /dev/null
@@ -1,145 +0,0 @@
-/*
- * Copyright © 2014-2020 The Android Password Store Authors. All Rights Reserved.
- * SPDX-License-Identifier: GPL-3.0-only
- */
-package com.zeapo.pwdstore.git;
-
-import android.app.Activity;
-import android.app.ProgressDialog;
-import android.content.Intent;
-import android.os.AsyncTask;
-
-import com.zeapo.pwdstore.PasswordStore;
-import com.zeapo.pwdstore.R;
-
-import org.eclipse.jgit.api.CommitCommand;
-import org.eclipse.jgit.api.GitCommand;
-import org.eclipse.jgit.api.PullCommand;
-import org.eclipse.jgit.api.PullResult;
-import org.eclipse.jgit.api.PushCommand;
-import org.eclipse.jgit.api.RebaseResult;
-import org.eclipse.jgit.api.StatusCommand;
-import org.eclipse.jgit.transport.PushResult;
-import org.eclipse.jgit.transport.RemoteRefUpdate;
-
-import java.lang.ref.WeakReference;
-
-public class GitAsyncTask extends AsyncTask<GitCommand, Integer, String> {
-    private WeakReference<Activity> activityWeakReference;
-    private boolean refreshListOnEnd;
-    private ProgressDialog dialog;
-    private GitOperation operation;
-    private Intent finishWithResultOnEnd;
-
-    public GitAsyncTask(
-        Activity activity,
-        boolean refreshListOnEnd,
-        GitOperation operation,
-        Intent finishWithResultOnEnd) {
-        this.activityWeakReference = new WeakReference<>(activity);
-        this.refreshListOnEnd = refreshListOnEnd;
-        this.operation = operation;
-        this.finishWithResultOnEnd = finishWithResultOnEnd;
-
-        dialog = new ProgressDialog(getActivity());
-    }
-
-    private Activity getActivity() {
-        return activityWeakReference.get();
-    }
-
-    protected void onPreExecute() {
-        this.dialog.setMessage(
-            getActivity().getResources().getString(R.string.running_dialog_text));
-        this.dialog.setCancelable(false);
-        this.dialog.show();
-    }
-
-    @Override
-    protected String doInBackground(GitCommand... commands) {
-        Integer nbChanges = null;
-        final Activity activity = getActivity();
-        for (GitCommand command : commands) {
-            try {
-                if (command instanceof StatusCommand) {
-                    // in case we have changes, we want to keep track of it
-                    org.eclipse.jgit.api.Status status = ((StatusCommand) command).call();
-                    nbChanges = status.getChanged().size() + status.getMissing().size();
-                } else if (command instanceof CommitCommand) {
-                    // the previous status will eventually be used to avoid a commit
-                    if (nbChanges == null || nbChanges > 0) command.call();
-                } else if (command instanceof PullCommand) {
-                    final PullResult result = ((PullCommand) command).call();
-                    final RebaseResult rr = result.getRebaseResult();
-
-                    if (rr.getStatus() == RebaseResult.Status.STOPPED) {
-                        return activity.getString(R.string.git_pull_fail_error);
-                    }
-
-                } else if (command instanceof PushCommand) {
-                    for (final PushResult result : ((PushCommand) command).call()) {
-                        // Code imported (modified) from Gerrit PushOp, license Apache v2
-                        for (final RemoteRefUpdate rru : result.getRemoteUpdates()) {
-                            switch (rru.getStatus()) {
-                                case REJECTED_NONFASTFORWARD:
-                                    return activity.getString(R.string.git_push_nff_error);
-                                case REJECTED_NODELETE:
-                                case REJECTED_REMOTE_CHANGED:
-                                case NON_EXISTING:
-                                case NOT_ATTEMPTED:
-                                    return activity.getString(R.string.git_push_generic_error)
-                                        + rru.getStatus().name();
-                                case REJECTED_OTHER_REASON:
-                                    if ("non-fast-forward".equals(rru.getMessage())) {
-                                        return activity.getString(R.string.git_push_other_error);
-                                    } else {
-                                        return activity.getString(R.string.git_push_generic_error)
-                                            + rru.getMessage();
-                                    }
-                                default:
-                                    break;
-                            }
-                        }
-                    }
-                } else {
-                    command.call();
-                }
-
-            } catch (Exception e) {
-                e.printStackTrace();
-                return e.getMessage() + "\nCaused by:\n" + e.getCause();
-            }
-        }
-        return "";
-    }
-
-    protected void onPostExecute(String result) {
-        if (this.dialog != null)
-            try {
-                this.dialog.dismiss();
-            } catch (Exception e) {
-                // ignore
-            }
-
-        if (result == null) result = "Unexpected error";
-
-        if (!result.isEmpty()) {
-            this.operation.onError(result);
-        } else {
-            this.operation.onSuccess();
-
-            if (finishWithResultOnEnd != null) {
-                this.getActivity().setResult(Activity.RESULT_OK, finishWithResultOnEnd);
-                this.getActivity().finish();
-            }
-
-            if (refreshListOnEnd) {
-                try {
-                    ((PasswordStore) this.getActivity()).resetPasswordList();
-                } catch (ClassCastException e) {
-                    // oups, mistake
-                }
-            }
-        }
-    }
-}
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/GitAsyncTask.kt b/app/src/main/java/com/zeapo/pwdstore/git/GitAsyncTask.kt
new file mode 100644
index 00000000..631bbf88
--- /dev/null
+++ b/app/src/main/java/com/zeapo/pwdstore/git/GitAsyncTask.kt
@@ -0,0 +1,148 @@
+/*
+ * Copyright © 2014-2020 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+package com.zeapo.pwdstore.git
+
+import android.app.Activity
+import android.app.ProgressDialog
+import android.content.Context
+import android.content.Intent
+import android.os.AsyncTask
+import com.github.ajalt.timberkt.e
+import com.zeapo.pwdstore.PasswordStore
+import com.zeapo.pwdstore.R
+import net.schmizz.sshj.userauth.UserAuthException
+import org.eclipse.jgit.api.CommitCommand
+import org.eclipse.jgit.api.GitCommand
+import org.eclipse.jgit.api.PullCommand
+import org.eclipse.jgit.api.PushCommand
+import org.eclipse.jgit.api.RebaseResult
+import org.eclipse.jgit.api.StatusCommand
+import org.eclipse.jgit.transport.RemoteRefUpdate
+import java.io.IOException
+import java.lang.ref.WeakReference
+
+
+class GitAsyncTask(
+    activity: Activity,
+    private val refreshListOnEnd: Boolean,
+    private val operation: GitOperation,
+    private val finishWithResultOnEnd: Intent?) : AsyncTask<GitCommand<*>, Int, GitAsyncTask.Result>() {
+
+    private val activityWeakReference: WeakReference<Activity> = WeakReference(activity)
+    private val activity: Activity?
+        get() = activityWeakReference.get()
+    private val context: Context = activity.applicationContext
+    private val dialog = ProgressDialog(activity)
+
+    sealed class Result {
+        object Ok : Result()
+        data class Err(val err: Exception) : Result()
+    }
+
+    override fun onPreExecute() {
+        dialog.run {
+            setMessage(activity!!.resources.getString(R.string.running_dialog_text))
+            setCancelable(false)
+            show()
+        }
+    }
+
+    override fun doInBackground(vararg commands: GitCommand<*>): Result? {
+        var nbChanges: Int? = null
+        for (command in commands) {
+            try {
+                when (command) {
+                    is StatusCommand -> {
+                        // in case we have changes, we want to keep track of it
+                        val status = command.call()
+                        nbChanges = status.changed.size + status.missing.size
+                    }
+                    is CommitCommand -> {
+                        // the previous status will eventually be used to avoid a commit
+                        if (nbChanges == null || nbChanges > 0) command.call()
+                    }
+                    is PullCommand -> {
+                        val result = command.call()
+                        val rr = result.rebaseResult
+                        if (rr.status === RebaseResult.Status.STOPPED) {
+                            return Result.Err(IOException(context.getString(R.string
+                                .git_pull_fail_error)))
+                        }
+                    }
+                    is PushCommand -> {
+                        for (result in command.call()) {
+                            // Code imported (modified) from Gerrit PushOp, license Apache v2
+                            for (rru in result.remoteUpdates) {
+                                val error = when (rru.status) {
+                                    RemoteRefUpdate.Status.REJECTED_NONFASTFORWARD ->
+                                        context.getString(R.string.git_push_nff_error)
+                                    RemoteRefUpdate.Status.REJECTED_NODELETE,
+                                    RemoteRefUpdate.Status.REJECTED_REMOTE_CHANGED,
+                                    RemoteRefUpdate.Status.NON_EXISTING,
+                                    RemoteRefUpdate.Status.NOT_ATTEMPTED ->
+                                        (activity!!.getString(R.string.git_push_generic_error) + rru.status.name)
+                                    RemoteRefUpdate.Status.REJECTED_OTHER_REASON -> {
+                                        if
+                                            ("non-fast-forward" == rru.message) {
+                                            context.getString(R.string.git_push_other_error)
+                                        } else {
+                                            (context.getString(R.string.git_push_generic_error)
+                                                + rru.message)
+                                        }
+                                    }
+                                    else -> null
+
+                                }
+                                if (error != null)
+                                    Result.Err(IOException(error))
+                            }
+                        }
+                    }
+                    else -> {
+                        command.call()
+                    }
+                }
+            } catch (e: Exception) {
+                return Result.Err(e)
+            }
+        }
+        return Result.Ok
+    }
+
+    private fun rootCauseException(e: Exception): Exception {
+        var rootCause = e
+        // JGit's TransportException hides the more helpful SSHJ exceptions.
+        // Also, SSHJ's UserAuthException about exhausting available authentication methods hides
+        // more useful exceptions.
+        while ((rootCause is org.eclipse.jgit.errors.TransportException ||
+                rootCause is org.eclipse.jgit.api.errors.TransportException ||
+                (rootCause is UserAuthException &&
+                    rootCause.message == "Exhausted available authentication methods"))) {
+            rootCause = rootCause.cause as? Exception ?: break
+        }
+        return rootCause
+    }
+
+    override fun onPostExecute(maybeResult: Result?) {
+        dialog.dismiss()
+        when (val result = maybeResult ?: Result.Err(IOException("Unexpected error"))) {
+            is Result.Err -> {
+                e(result.err)
+                operation.onError(rootCauseException(result.err))
+            }
+            is Result.Ok -> {
+                operation.onSuccess()
+                if (finishWithResultOnEnd != null) {
+                    activity?.setResult(Activity.RESULT_OK, finishWithResultOnEnd)
+                    activity?.finish()
+                }
+                if (refreshListOnEnd) {
+                    (activity as? PasswordStore)?.resetPasswordList()
+                }
+            }
+        }
+    }
+
+}
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/GitOperation.kt b/app/src/main/java/com/zeapo/pwdstore/git/GitOperation.kt
index 712d1bc5..bfcf2f11 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/GitOperation.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/GitOperation.kt
@@ -13,15 +13,14 @@ import androidx.preference.PreferenceManager
 import com.google.android.material.checkbox.MaterialCheckBox
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
 import com.google.android.material.textfield.TextInputEditText
-import com.jcraft.jsch.JSch
-import com.jcraft.jsch.JSchException
-import com.jcraft.jsch.KeyPair
 import com.zeapo.pwdstore.R
 import com.zeapo.pwdstore.UserPreference
 import com.zeapo.pwdstore.git.config.ConnectionMode
 import com.zeapo.pwdstore.git.config.GitConfigSessionFactory
+import com.zeapo.pwdstore.git.config.InteractivePasswordFinder
 import com.zeapo.pwdstore.git.config.SshApiSessionFactory
-import com.zeapo.pwdstore.git.config.SshConfigSessionFactory
+import com.zeapo.pwdstore.git.config.SshAuthData
+import com.zeapo.pwdstore.git.config.SshjSessionFactory
 import com.zeapo.pwdstore.utils.PasswordRepository
 import com.zeapo.pwdstore.utils.getEncryptedPrefs
 import com.zeapo.pwdstore.utils.requestInputFocusOnView
@@ -30,6 +29,7 @@ import org.eclipse.jgit.lib.Repository
 import org.eclipse.jgit.transport.SshSessionFactory
 import org.eclipse.jgit.transport.UsernamePasswordCredentialsProvider
 import java.io.File
+import kotlin.coroutines.resume
 
 /**
  * Creates a new git operation
@@ -42,6 +42,8 @@ abstract class GitOperation(fileDir: File, internal val callingActivity: Activit
     protected val repository: Repository? = PasswordRepository.getRepository(fileDir)
     internal var provider: UsernamePasswordCredentialsProvider? = null
     internal var command: GitCommand<*>? = null
+    private val sshKeyFile = callingActivity.filesDir.resolve(".ssh_key")
+    private val hostKeyFile = callingActivity.filesDir.resolve(".host_key")
 
     /**
      * Sets the authentication using user/pwd scheme
@@ -56,16 +58,8 @@ abstract class GitOperation(fileDir: File, internal val callingActivity: Activit
         return this
     }
 
-    /**
-     * Sets the authentication using ssh-key scheme
-     *
-     * @param sshKey the ssh-key file
-     * @param username the username
-     * @param passphrase the passphrase
-     * @return the current object
-     */
-    internal open fun setAuthentication(sshKey: File, username: String, passphrase: String): GitOperation {
-        val sessionFactory = SshConfigSessionFactory(sshKey.absolutePath, username, passphrase)
+    private fun withPublicKeyAuthentication(username: String, passphraseFinder: InteractivePasswordFinder): GitOperation {
+        val sessionFactory = SshjSessionFactory(username, SshAuthData.PublicKeyFile(sshKeyFile, passphraseFinder), hostKeyFile)
         SshSessionFactory.setInstance(sessionFactory)
         this.provider = null
         return this
@@ -93,38 +87,17 @@ abstract class GitOperation(fileDir: File, internal val callingActivity: Activit
      *
      * @param connectionMode the server-connection mode
      * @param username the username
-     * @param sshKey the ssh-key file to use in ssh-key connection mode
      * @param identity the api identity to use for auth in OpenKeychain connection mode
      */
     fun executeAfterAuthentication(
         connectionMode: ConnectionMode,
         username: String,
-        sshKey: File?,
         identity: SshApiSessionFactory.ApiIdentity?
     ) {
-        executeAfterAuthentication(connectionMode, username, sshKey, identity, false)
-    }
-
-    /**
-     * Executes the GitCommand in an async task after creating the authentication
-     *
-     * @param connectionMode the server-connection mode
-     * @param username the username
-     * @param sshKey the ssh-key file to use in ssh-key connection mode
-     * @param identity the api identity to use for auth in OpenKeychain connection mode
-     * @param showError show the passphrase edit text in red
-     */
-    private fun executeAfterAuthentication(
-        connectionMode: ConnectionMode,
-        username: String,
-        sshKey: File?,
-        identity: SshApiSessionFactory.ApiIdentity?,
-        showError: Boolean
-    ) {
         val encryptedSettings = callingActivity.applicationContext.getEncryptedPrefs("git_operation")
         when (connectionMode) {
             ConnectionMode.SshKey -> {
-                if (sshKey == null || !sshKey.exists()) {
+                if (!sshKeyFile.exists()) {
                     MaterialAlertDialogBuilder(callingActivity)
                         .setMessage(callingActivity.resources.getString(R.string.ssh_preferences_dialog_text))
                         .setTitle(callingActivity.resources.getString(R.string.ssh_preferences_dialog_title))
@@ -156,65 +129,47 @@ abstract class GitOperation(fileDir: File, internal val callingActivity: Activit
                             callingActivity.finish()
                         }.show()
                 } else {
-                    val layoutInflater = LayoutInflater.from(callingActivity)
-                    @SuppressLint("InflateParams") val dialogView = layoutInflater.inflate(R.layout.git_passphrase_layout, null)
-                    val passphrase = dialogView.findViewById<TextInputEditText>(R.id.git_auth_passphrase)
-                    val sshKeyPassphrase = encryptedSettings.getString("ssh_key_local_passphrase", null)
-                    if (showError) {
-                        passphrase.error = callingActivity.resources.getString(R.string.git_operation_wrong_passphrase)
-                    }
-                    val jsch = JSch()
-                    try {
-                        val keyPair = KeyPair.load(jsch, callingActivity.filesDir.toString() + "/.ssh_key")
+                    withPublicKeyAuthentication(username, InteractivePasswordFinder { cont, isRetry ->
+                        val storedPassphrase = encryptedSettings.getString("ssh_key_local_passphrase", null)
+                        if (isRetry)
+                            encryptedSettings.edit { putString("ssh_key_local_passphrase", null) }
+                        if (storedPassphrase.isNullOrEmpty()) {
+                            val layoutInflater = LayoutInflater.from(callingActivity)
 
-                        if (keyPair.isEncrypted) {
-                            if (sshKeyPassphrase != null && sshKeyPassphrase.isNotEmpty()) {
-                                if (keyPair.decrypt(sshKeyPassphrase)) {
-                                    // Authenticate using the ssh-key and then execute the command
-                                    setAuthentication(sshKey, username, sshKeyPassphrase).execute()
-                                } else {
-                                    // call back the method
-                                    executeAfterAuthentication(connectionMode, username, sshKey, identity, true)
-                                }
-                            } else {
-                                val dialog = MaterialAlertDialogBuilder(callingActivity)
-                                    .setTitle(callingActivity.resources.getString(R.string.passphrase_dialog_title))
-                                    .setMessage(callingActivity.resources.getString(R.string.passphrase_dialog_text))
-                                    .setView(dialogView)
-                                    .setPositiveButton(callingActivity.resources.getString(R.string.dialog_ok)) { _, _ ->
-                                        if (keyPair.decrypt(passphrase.text.toString())) {
-                                            if (dialogView.findViewById<MaterialCheckBox>(R.id.git_auth_remember_passphrase).isChecked) {
-                                                encryptedSettings.edit { putString("ssh_key_local_passphrase", passphrase.text.toString()) }
-                                            }
-                                            // Authenticate using the ssh-key and then execute the command
-                                            setAuthentication(sshKey, username, passphrase.text.toString()).execute()
-                                        } else {
-                                            encryptedSettings.edit { putString("ssh_key_local_passphrase", null) }
-                                            // call back the method
-                                            executeAfterAuthentication(connectionMode, username, sshKey, identity, true)
+                            @SuppressLint("InflateParams")
+                            val dialogView = layoutInflater.inflate(R.layout.git_passphrase_layout, null)
+                            val editPassphrase = dialogView.findViewById<TextInputEditText>(R.id.git_auth_passphrase)
+                            val rememberPassphrase = dialogView.findViewById<MaterialCheckBox>(R.id.git_auth_remember_passphrase)
+                            if (isRetry)
+                                editPassphrase.error = callingActivity.resources.getString(R.string.git_operation_wrong_passphrase)
+                            MaterialAlertDialogBuilder(callingActivity).run {
+                                setTitle(R.string.passphrase_dialog_title)
+                                setMessage(R.string.passphrase_dialog_text)
+                                setView(dialogView)
+                                setPositiveButton(R.string.dialog_ok) { _, _ ->
+                                    val passphrase = editPassphrase.text.toString()
+                                    if (rememberPassphrase.isChecked) {
+                                        encryptedSettings.edit {
+                                            putString("ssh_key_local_passphrase", passphrase)
                                         }
                                     }
-                                    .setNegativeButton(callingActivity.resources.getString(R.string.dialog_cancel)) { _, _ ->
-                                        callingActivity.finish()
-                                    }
-                                    .setOnCancelListener { callingActivity.finish() }
-                                    .create()
-                                dialog.requestInputFocusOnView<TextInputEditText>(R.id.git_auth_passphrase)
-                                dialog.show()
+                                    cont.resume(passphrase)
+                                }
+                                setNegativeButton(R.string.dialog_cancel) { _, _ ->
+                                    cont.resume(null)
+                                }
+                                setOnCancelListener {
+                                    cont.resume(null)
+                                }
+                                create()
+                            }.run {
+                                requestInputFocusOnView<TextInputEditText>(R.id.git_auth_passphrase)
+                                show()
                             }
                         } else {
-                            setAuthentication(sshKey, username, "").execute()
+                            cont.resume(storedPassphrase)
                         }
-                    } catch (e: JSchException) {
-                        e.printStackTrace()
-                        MaterialAlertDialogBuilder(callingActivity)
-                            .setTitle(callingActivity.resources.getString(R.string.git_operation_unable_to_open_ssh_key_title))
-                            .setMessage(callingActivity.resources.getString(R.string.git_operation_unable_to_open_ssh_key_message))
-                            .setPositiveButton(callingActivity.resources.getString(R.string.dialog_ok)) { _, _ ->
-                                callingActivity.finish()
-                            }
-                            .show()
-                    }
+                    }).execute()
                 }
             }
             ConnectionMode.OpenKeychain -> {
@@ -256,18 +211,23 @@ abstract class GitOperation(fileDir: File, internal val callingActivity: Activit
     /**
      * Action to execute on error
      */
-    open fun onError(errorMessage: String) {
+    open fun onError(err: Exception) {
         // Clear various auth related fields on failure
-        if (SshSessionFactory.getInstance() is SshApiSessionFactory) {
-            PreferenceManager.getDefaultSharedPreferences(callingActivity.applicationContext)
-                .edit { putString("ssh_openkeystore_keyid", null) }
-            callingActivity.applicationContext
-                .getEncryptedPrefs("git_operation")
-                .edit { remove("ssh_key_local_passphrase") }
-        } else if (SshSessionFactory.getInstance() is GitConfigSessionFactory) {
-            callingActivity.applicationContext
-                .getEncryptedPrefs("git_operation")
-                .edit { remove("https_password") }
+        when (SshSessionFactory.getInstance()) {
+            is SshApiSessionFactory -> {
+                PreferenceManager.getDefaultSharedPreferences(callingActivity.applicationContext)
+                    .edit { putString("ssh_openkeystore_keyid", null) }
+            }
+            is SshjSessionFactory -> {
+                callingActivity.applicationContext
+                    .getEncryptedPrefs("git_operation")
+                    .edit { remove("ssh_key_local_passphrase") }
+            }
+            is GitConfigSessionFactory -> {
+                callingActivity.applicationContext
+                    .getEncryptedPrefs("git_operation")
+                    .edit { remove("https_password") }
+            }
         }
     }
 
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/PullOperation.kt b/app/src/main/java/com/zeapo/pwdstore/git/PullOperation.kt
index ec511a5b..2d5f6bbe 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/PullOperation.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/PullOperation.kt
@@ -38,13 +38,13 @@ class PullOperation(fileDir: File, callingActivity: Activity) : GitOperation(fil
         GitAsyncTask(callingActivity, false, this, Intent()).execute(this.command)
     }
 
-    override fun onError(errorMessage: String) {
-        super.onError(errorMessage)
+    override fun onError(err: Exception) {
+        super.onError(err)
         MaterialAlertDialogBuilder(callingActivity)
             .setTitle(callingActivity.resources.getString(R.string.jgit_error_dialog_title))
             .setMessage("Error occurred during the pull operation, " +
                 callingActivity.resources.getString(R.string.jgit_error_dialog_text) +
-                errorMessage +
+                err.message +
                 "\nPlease check the FAQ for possible reasons why this error might occur.")
             .setPositiveButton(callingActivity.resources.getString(R.string.dialog_ok)) { _, _ -> callingActivity.finish() }
             .show()
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/PushOperation.kt b/app/src/main/java/com/zeapo/pwdstore/git/PushOperation.kt
index b2e87322..52e6e537 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/PushOperation.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/PushOperation.kt
@@ -38,12 +38,12 @@ class PushOperation(fileDir: File, callingActivity: Activity) : GitOperation(fil
         GitAsyncTask(callingActivity, false, this, Intent()).execute(this.command)
     }
 
-    override fun onError(errorMessage: String) {
+    override fun onError(err: Exception) {
         // TODO handle the "Nothing to push" case
-        super.onError(errorMessage)
+        super.onError(err)
         MaterialAlertDialogBuilder(callingActivity)
             .setTitle(callingActivity.resources.getString(R.string.jgit_error_dialog_title))
-            .setMessage(callingActivity.getString(R.string.jgit_error_push_dialog_text) + errorMessage)
+            .setMessage(callingActivity.getString(R.string.jgit_error_push_dialog_text) + err.message)
             .setPositiveButton(callingActivity.resources.getString(R.string.dialog_ok)) { _, _ -> callingActivity.finish() }
             .show()
     }
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/ResetToRemoteOperation.kt b/app/src/main/java/com/zeapo/pwdstore/git/ResetToRemoteOperation.kt
index 41427c09..c652889d 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/ResetToRemoteOperation.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/ResetToRemoteOperation.kt
@@ -45,14 +45,14 @@ class ResetToRemoteOperation(fileDir: File, callingActivity: Activity) : GitOper
             .execute(this.addCommand, this.fetchCommand, this.resetCommand)
     }
 
-    override fun onError(errorMessage: String) {
-        super.onError(errorMessage)
+    override fun onError(err: Exception) {
+        super.onError(err)
         MaterialAlertDialogBuilder(callingActivity)
             .setTitle(callingActivity.resources.getString(R.string.jgit_error_dialog_title))
             .setMessage("Error occurred during the sync operation, " +
                 "\nPlease check the FAQ for possible reasons why this error might occur." +
                 callingActivity.resources.getString(R.string.jgit_error_dialog_text) +
-                errorMessage)
+                err)
             .setPositiveButton(callingActivity.resources.getString(R.string.dialog_ok)) { _, _ -> }
             .show()
     }
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/SyncOperation.kt b/app/src/main/java/com/zeapo/pwdstore/git/SyncOperation.kt
index 5188baff..1f241c64 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/SyncOperation.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/SyncOperation.kt
@@ -53,14 +53,14 @@ class SyncOperation(fileDir: File, callingActivity: Activity) : GitOperation(fil
         GitAsyncTask(callingActivity, false, this, Intent()).execute(this.addCommand, this.statusCommand, this.commitCommand, this.pullCommand, this.pushCommand)
     }
 
-    override fun onError(errorMessage: String) {
-        super.onError(errorMessage)
+    override fun onError(err: Exception) {
+        super.onError(err)
         MaterialAlertDialogBuilder(callingActivity)
             .setTitle(callingActivity.resources.getString(R.string.jgit_error_dialog_title))
             .setMessage("Error occurred during the sync operation, " +
                 "\nPlease check the FAQ for possible reasons why this error might occur." +
                 callingActivity.resources.getString(R.string.jgit_error_dialog_text) +
-                errorMessage)
+                err)
             .setPositiveButton(callingActivity.resources.getString(R.string.dialog_ok)) { _, _ -> callingActivity.finish() }
             .show()
     }
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/config/SshConfigSessionFactory.kt b/app/src/main/java/com/zeapo/pwdstore/git/config/SshConfigSessionFactory.kt
deleted file mode 100644
index 9be49345..00000000
--- a/app/src/main/java/com/zeapo/pwdstore/git/config/SshConfigSessionFactory.kt
+++ /dev/null
@@ -1,58 +0,0 @@
-/*
- * Copyright © 2014-2020 The Android Password Store Authors. All Rights Reserved.
- * SPDX-License-Identifier: GPL-3.0-only
- */
-package com.zeapo.pwdstore.git.config
-
-import com.jcraft.jsch.JSch
-import com.jcraft.jsch.JSchException
-import com.jcraft.jsch.Session
-import org.eclipse.jgit.errors.UnsupportedCredentialItem
-import org.eclipse.jgit.transport.CredentialItem
-import org.eclipse.jgit.transport.CredentialsProvider
-import org.eclipse.jgit.transport.CredentialsProviderUserInfo
-import org.eclipse.jgit.transport.OpenSshConfig
-import org.eclipse.jgit.transport.URIish
-import org.eclipse.jgit.util.FS
-
-class SshConfigSessionFactory(private val sshKey: String, private val username: String, private val passphrase: String) : GitConfigSessionFactory() {
-
-    @Throws(JSchException::class)
-    override fun getJSch(hc: OpenSshConfig.Host, fs: FS): JSch {
-        val jsch = super.getJSch(hc, fs)
-        jsch.removeAllIdentity()
-        jsch.addIdentity(sshKey)
-        return jsch
-    }
-
-    override fun configure(hc: OpenSshConfig.Host, session: Session) {
-        session.setConfig("StrictHostKeyChecking", "no")
-        session.setConfig("PreferredAuthentications", "publickey,password")
-
-        val provider = object : CredentialsProvider() {
-            override fun isInteractive(): Boolean {
-                return false
-            }
-
-            override fun supports(vararg items: CredentialItem): Boolean {
-                return true
-            }
-
-            @Throws(UnsupportedCredentialItem::class)
-            override fun get(uri: URIish, vararg items: CredentialItem): Boolean {
-                for (item in items) {
-                    if (item is CredentialItem.Username) {
-                        item.value = username
-                        continue
-                    }
-                    if (item is CredentialItem.StringType) {
-                        item.value = passphrase
-                    }
-                }
-                return true
-            }
-        }
-        val userInfo = CredentialsProviderUserInfo(session, provider)
-        session.userInfo = userInfo
-    }
-}
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/config/SshjSessionFactory.kt b/app/src/main/java/com/zeapo/pwdstore/git/config/SshjSessionFactory.kt
new file mode 100644
index 00000000..5287989a
--- /dev/null
+++ b/app/src/main/java/com/zeapo/pwdstore/git/config/SshjSessionFactory.kt
@@ -0,0 +1,148 @@
+/*
+ * Copyright © 2014-2020 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+package com.zeapo.pwdstore.git.config
+
+import android.util.Base64
+import com.github.ajalt.timberkt.d
+import com.github.ajalt.timberkt.w
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.runBlocking
+import net.schmizz.sshj.SSHClient
+import net.schmizz.sshj.common.Buffer.PlainBuffer
+import net.schmizz.sshj.common.SSHRuntimeException
+import net.schmizz.sshj.common.SecurityUtils
+import net.schmizz.sshj.connection.channel.direct.Session
+import net.schmizz.sshj.transport.verification.FingerprintVerifier
+import net.schmizz.sshj.transport.verification.HostKeyVerifier
+import net.schmizz.sshj.userauth.password.PasswordFinder
+import net.schmizz.sshj.userauth.password.Resource
+import org.eclipse.jgit.transport.CredentialsProvider
+import org.eclipse.jgit.transport.RemoteSession
+import org.eclipse.jgit.transport.SshSessionFactory
+import org.eclipse.jgit.transport.URIish
+import org.eclipse.jgit.util.FS
+import java.io.File
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+import java.security.GeneralSecurityException
+import java.util.concurrent.TimeUnit
+import kotlin.coroutines.Continuation
+import kotlin.coroutines.suspendCoroutine
+
+sealed class SshAuthData {
+    class Password(val passwordFinder: InteractivePasswordFinder) : SshAuthData()
+    class PublicKeyFile(val keyFile: File, val passphraseFinder: InteractivePasswordFinder) : SshAuthData()
+}
+
+class InteractivePasswordFinder(val askForPassword: (cont: Continuation<String?>, isRetry: Boolean) -> Unit) : PasswordFinder {
+
+    private var isRetry = false
+    private var shouldRetry = true
+
+    override fun reqPassword(resource: Resource<*>?): CharArray {
+        val password = runBlocking(Dispatchers.Main) {
+            suspendCoroutine<String?> { cont ->
+                askForPassword(cont, isRetry)
+            }
+        }
+        isRetry = true
+        return if (password != null) {
+            password.toCharArray()
+        } else {
+            shouldRetry = false
+            CharArray(0)
+        }
+    }
+
+    override fun shouldRetry(resource: Resource<*>?) = shouldRetry
+}
+
+class SshjSessionFactory(private val username: String, private val authData: SshAuthData, private val hostKeyFile: File) : SshSessionFactory() {
+
+    override fun getSession(uri: URIish, credentialsProvider: CredentialsProvider?, fs: FS?, tms: Int): RemoteSession {
+        return SshjSession(uri, username, authData, hostKeyFile).connect()
+    }
+}
+
+private fun makeTofuHostKeyVerifier(hostKeyFile: File): HostKeyVerifier {
+    if (!hostKeyFile.exists()) {
+        return HostKeyVerifier { _, _, key ->
+            val digest = try {
+                SecurityUtils.getMessageDigest("SHA-256")
+            } catch (e: GeneralSecurityException) {
+                throw SSHRuntimeException(e)
+            }
+            digest.update(PlainBuffer().putPublicKey(key).compactData)
+            val digestData = digest.digest()
+            val hostKeyEntry = "SHA256:${Base64.encodeToString(digestData, Base64.NO_WRAP)}"
+            d { "Trusting host key on first use: $hostKeyEntry" }
+            hostKeyFile.writeText(hostKeyEntry)
+            true
+        }
+    } else {
+        val hostKeyEntry = hostKeyFile.readText()
+        d { "Pinned host key: $hostKeyEntry" }
+        return FingerprintVerifier.getInstance(hostKeyEntry)
+    }
+}
+
+private class SshjSession(private val uri: URIish, private val username: String, private val authData: SshAuthData, private val hostKeyFile: File) : RemoteSession {
+
+    private lateinit var ssh: SSHClient
+    private var currentCommand: Session? = null
+
+    fun connect(): SshjSession {
+        ssh = SSHClient()
+        ssh.addHostKeyVerifier(makeTofuHostKeyVerifier(hostKeyFile))
+        ssh.connect(uri.host, uri.port.takeUnless { it == -1 } ?: 22)
+        if (!ssh.isConnected)
+            throw IOException()
+        when (authData) {
+            is SshAuthData.Password -> {
+                ssh.authPassword(username, authData.passwordFinder)
+            }
+            is SshAuthData.PublicKeyFile -> {
+                ssh.authPublickey(username, ssh.loadKeys(authData.keyFile.absolutePath, authData.passphraseFinder))
+            }
+        }
+        return this
+    }
+
+    override fun exec(commandName: String?, timeout: Int): Process {
+        if (currentCommand != null) {
+            w { "Killing old session" }
+            currentCommand?.close()
+            currentCommand = null
+        }
+        val session = ssh.startSession()
+        currentCommand = session
+        return SshjProcess(session.exec(commandName), timeout.toLong())
+    }
+
+    override fun disconnect() {
+        currentCommand?.close()
+        ssh.close()
+    }
+}
+
+private class SshjProcess(private val command: Session.Command, private val timeout: Long) : Process() {
+
+    override fun waitFor(): Int {
+        command.join(timeout, TimeUnit.SECONDS)
+        command.close()
+        return exitValue()
+    }
+
+    override fun destroy() = command.close()
+
+    override fun getOutputStream(): OutputStream = command.outputStream
+
+    override fun getErrorStream(): InputStream = command.errorStream
+
+    override fun exitValue(): Int = command.exitStatus
+
+    override fun getInputStream(): InputStream = command.inputStream
+}
diff --git a/app/src/main/java/com/zeapo/pwdstore/sshkeygen/SshKeyGenFragment.kt b/app/src/main/java/com/zeapo/pwdstore/sshkeygen/SshKeyGenFragment.kt
index a7ed82b8..9b9d58f5 100644
--- a/app/src/main/java/com/zeapo/pwdstore/sshkeygen/SshKeyGenFragment.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/sshkeygen/SshKeyGenFragment.kt
@@ -17,6 +17,7 @@ import com.jcraft.jsch.JSch
 import com.jcraft.jsch.KeyPair
 import com.zeapo.pwdstore.R
 import com.zeapo.pwdstore.databinding.FragmentSshKeygenBinding
+import com.zeapo.pwdstore.utils.getEncryptedPrefs
 import com.zeapo.pwdstore.utils.viewBinding
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
@@ -74,6 +75,10 @@ class SshKeyGenFragment : Fragment(R.layout.fragment_ssh_keygen) {
         } catch (e: Exception) {
             e.printStackTrace()
             e
+        } finally {
+            requireContext().getEncryptedPrefs("git_operation").edit {
+                remove("ssh_key_local_passphrase")
+            }
         }
         val activity = requireActivity()
         binding.generate.text = getString(R.string.ssh_keygen_generating_done)