Improve Git password/passphrase dialog behavior (#829)

* Reset PasswordFinder retry state after authentication

* Memorize password inbetween Git commands

app/src/main/java/com/zeapo/pwdstore/git/GitAsyncTask.kt

@@ -12,6 +12,7 @@ import android.os.AsyncTask
 import com.github.ajalt.timberkt.e
 import com.zeapo.pwdstore.PasswordStore
 import com.zeapo.pwdstore.R
+import com.zeapo.pwdstore.git.config.SshjSessionFactory
 import net.schmizz.sshj.userauth.UserAuthException
 import org.eclipse.jgit.api.CommitCommand
 import org.eclipse.jgit.api.GitCommand
@@ -147,6 +148,7 @@ class GitAsyncTask(
         if (refreshListOnEnd) {
             (activity as? PasswordStore)?.resetPasswordList()
         }
+        (SshSessionFactory.getInstance() as? SshjSessionFactory)?.clearCredentials()
         SshSessionFactory.setInstance(null)
     }
 

app/src/main/java/com/zeapo/pwdstore/git/config/SshjSessionFactory.kt

@@ -7,6 +7,7 @@ package com.zeapo.pwdstore.git.config
 import android.util.Base64
 import com.github.ajalt.timberkt.d
 import com.github.ajalt.timberkt.w
+import com.zeapo.pwdstore.utils.clear
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.runBlocking
 import net.schmizz.sshj.SSHClient
@@ -33,18 +34,48 @@ import kotlin.coroutines.Continuation
 import kotlin.coroutines.suspendCoroutine
 
 sealed class SshAuthData {
-    class Password(val passwordFinder: InteractivePasswordFinder) : SshAuthData()
+    class Password(val passwordFinder: InteractivePasswordFinder) : SshAuthData() {
-    class PublicKeyFile(val keyFile: File, val passphraseFinder: InteractivePasswordFinder) : SshAuthData()
+        override fun clearCredentials() {
+            passwordFinder.clearPassword()
+        }
+    }
+
+    class PublicKeyFile(val keyFile: File, val passphraseFinder: InteractivePasswordFinder) : SshAuthData() {
+        override fun clearCredentials() {
+            passphraseFinder.clearPassword()
+        }
+    }
+
+    abstract fun clearCredentials()
 }
 
 abstract class InteractivePasswordFinder : PasswordFinder {
 
-    private var isRetry = false
-    private var shouldRetry = true
-
     abstract fun askForPassword(cont: Continuation<String?>, isRetry: Boolean)
 
+    private var isRetry = false
+    private var shouldRetry = true
+    private var lastPassword: CharArray? = null
+
+    fun resetForReuse() {
+        isRetry = false
+        shouldRetry = true
+    }
+
+    fun clearPassword() {
+        lastPassword?.clear()
+        lastPassword = null
+    }
+
     final override fun reqPassword(resource: Resource<*>?): CharArray {
+        if (lastPassword != null && !isRetry) {
+            // This instance successfully authenticated in a previous authentication step and is
+            // now being reused for a new one. We try the previous password so that the user
+            // does not have to type it again.
+            isRetry = true
+            return lastPassword!!
+        }
+        clearPassword()
         val password = runBlocking(Dispatchers.Main) {
             suspendCoroutine<String?> { cont ->
                 askForPassword(cont, isRetry)
@@ -52,7 +83,7 @@ abstract class InteractivePasswordFinder : PasswordFinder {
         }
         isRetry = true
         return if (password != null) {
-            password.toCharArray()
+            password.toCharArray().also { lastPassword = it }
         } else {
             shouldRetry = false
             CharArray(0)
@@ -67,6 +98,10 @@ class SshjSessionFactory(private val username: String, private val authData: Ssh
     override fun getSession(uri: URIish, credentialsProvider: CredentialsProvider?, fs: FS?, tms: Int): RemoteSession {
         return SshjSession(uri, username, authData, hostKeyFile).connect()
     }
+
+    fun clearCredentials() {
+        authData.clearCredentials()
+    }
 }
 
 private fun makeTofuHostKeyVerifier(hostKeyFile: File): HostKeyVerifier {
@@ -105,9 +140,11 @@ private class SshjSession(private val uri: URIish, private val username: String,
         when (authData) {
             is SshAuthData.Password -> {
                 ssh.authPassword(username, authData.passwordFinder)
+                authData.passwordFinder.resetForReuse()
             }
             is SshAuthData.PublicKeyFile -> {
                 ssh.authPublickey(username, ssh.loadKeys(authData.keyFile.absolutePath, authData.passphraseFinder))
+                authData.passphraseFinder.resetForReuse()
             }
         }
         return this

app/src/main/java/com/zeapo/pwdstore/utils/Extensions.kt

@@ -26,6 +26,12 @@ fun String.splitLines(): Array<String> {
     return split("\n".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
 }
 
+fun CharArray.clear() {
+    forEachIndexed { i, _ ->
+        this[i] = 0.toChar()
+    }
+}
+
 fun Context.resolveAttribute(attr: Int): Int {
     val typedValue = TypedValue()
     this.theme.resolveAttribute(attr, typedValue, true)