Add support for modifying repeater credentials

Credits go to @fxsheep: https://forum.xda-developers.com/showpost.php?p=76298728&postcount=5

Currently it only works on later versions of Android due to usage of `killall`. A workaround is in progress.

mobile/src/main/java/be/mygod/vpnhotspot/net/wifi/P2pSupplicantConfiguration.kt

@@ -0,0 +1,61 @@
+package be.mygod.vpnhotspot.net.wifi
+
+import android.net.wifi.WifiConfiguration
+import android.util.Log
+import android.widget.Toast
+import be.mygod.vpnhotspot.App.Companion.app
+import be.mygod.vpnhotspot.loggerSu
+import be.mygod.vpnhotspot.noisySu
+import java.io.File
+
+class P2pSupplicantConfiguration {
+    companion object {
+        private const val TAG = "P2pSupplicationConf"
+        // format for ssid is much more complicated, therefore we are only trying to find the line
+        private val ssidMatcher = "^[\\r\\t ]*ssid=".toRegex()
+        private val pskParser = "^[\\r\\t ]*psk=\"(.*)\"\$".toRegex(RegexOption.MULTILINE)
+    }
+
+    private val content by lazy { loggerSu("cat /data/misc/wifi/p2p_supplicant.conf") }
+
+    fun readPsk(): String? {
+        return try {
+            pskParser.findAll(content ?: return null).single().groupValues[1]
+        } catch (e: Exception) {
+            Log.w(TAG, content)
+            e.printStackTrace()
+            Toast.makeText(app, e.message, Toast.LENGTH_LONG).show()
+            null
+        }
+    }
+
+    fun update(config: WifiConfiguration): Boolean? {
+        val content = content ?: return null
+        val tempFile = File.createTempFile("vpnhotspot-", ".conf", app.cacheDir)
+        try {
+            var ssidFound = false
+            var pskFound = false
+            tempFile.printWriter().use {
+                for (line in content.lineSequence()) it.println(when {
+                    ssidMatcher.containsMatchIn(line) -> {
+                        ssidFound = true
+                        "\tssid=" + config.SSID.toByteArray()
+                                .joinToString("") { it.toInt().toString(16).padStart(2, '0') }
+                    }
+                    pskParser.containsMatchIn(line) -> {
+                        pskFound = true
+                        "\tpsk=\"${config.preSharedKey}\""  // no control chars or weird stuff
+                    }
+                    else -> line                            // do nothing
+                })
+            }
+            if (!ssidFound || !pskFound) {
+                Log.w(TAG, "Invalid conf ($ssidFound, $pskFound): $content")
+                return false
+            }
+            return noisySu("cat ${tempFile.absolutePath} > /data/misc/wifi/p2p_supplicant.conf", "killall wpa_supplicant")
+        } finally {
+            if (!tempFile.delete()) tempFile.deleteOnExit()
+        }
+    }
+}

mobile/src/main/java/be/mygod/vpnhotspot/net/wifi/WifiApDialog.kt

@@ -0,0 +1,97 @@
+package be.mygod.vpnhotspot.net.wifi
+
+import android.content.Context
+import android.content.DialogInterface
+import android.net.wifi.WifiConfiguration
+import android.net.wifi.WifiConfiguration.AuthAlgorithm
+import android.os.Bundle
+import android.support.v7.app.AlertDialog
+import android.text.Editable
+import android.text.InputType
+import android.text.TextWatcher
+import android.view.View
+import android.widget.CheckBox
+import android.widget.EditText
+import android.widget.TextView
+import be.mygod.vpnhotspot.R
+import java.nio.charset.Charset
+
+/**
+ * https://android.googlesource.com/platform/packages/apps/Settings/+/39b4674/src/com/android/settings/wifi/WifiApDialog.java
+ */
+class WifiApDialog(mContext: Context, private val mListener: DialogInterface.OnClickListener,
+                   private val mWifiConfig: WifiConfiguration?) : AlertDialog(mContext), View.OnClickListener, TextWatcher {
+    companion object {
+        private const val BUTTON_SUBMIT = DialogInterface.BUTTON_POSITIVE
+    }
+
+    private lateinit var mView: View
+    private lateinit var mSsid: TextView
+    private lateinit var mPassword: EditText
+    /**
+     * TODO: SSID in WifiConfiguration for soft ap
+     * is being stored as a raw string without quotes.
+     * This is not the case on the client side. We need to
+     * make things consistent and clean it up
+     */
+    val config: WifiConfiguration?
+        get() {
+            val config = WifiConfiguration()
+            config.SSID = mSsid.text.toString()
+            config.allowedAuthAlgorithms.set(AuthAlgorithm.OPEN)
+            if (mPassword.length() != 0) {
+                val password = mPassword.text.toString()
+                config.preSharedKey = password
+            }
+            return config
+        }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        mView = layoutInflater.inflate(R.layout.dialog_wifi_ap, null)
+        setView(mView)
+        val context = context
+        setTitle(R.string.repeater_configure)
+        mSsid = mView.findViewById(R.id.ssid)
+        mPassword = mView.findViewById(R.id.password)
+        setButton(BUTTON_SUBMIT, context.getString(R.string.wifi_save), mListener)
+        setButton(DialogInterface.BUTTON_NEGATIVE,
+                context.getString(R.string.wifi_cancel), mListener)
+        setButton(DialogInterface.BUTTON_NEUTRAL, context.getString(R.string.repeater_reset_credentials), mListener)
+        if (mWifiConfig != null) {
+            mSsid.text = mWifiConfig.SSID
+            mPassword.setText(mWifiConfig.preSharedKey)
+        }
+        mSsid.addTextChangedListener(this)
+        mPassword.addTextChangedListener(this)
+        (mView.findViewById(R.id.show_password) as CheckBox).setOnClickListener(this)
+        super.onCreate(savedInstanceState)
+        validate()
+    }
+
+    override fun onRestoreInstanceState(savedInstanceState: Bundle) {
+        super.onRestoreInstanceState(savedInstanceState)
+        mPassword.inputType = InputType.TYPE_CLASS_TEXT or
+                if ((mView.findViewById(R.id.show_password) as CheckBox).isChecked)
+                    InputType.TYPE_TEXT_VARIATION_VISIBLE_PASSWORD
+                else InputType.TYPE_TEXT_VARIATION_PASSWORD
+    }
+
+    private fun validate() {
+        val mSsidString = mSsid.text.toString()
+        getButton(BUTTON_SUBMIT).isEnabled = mSsid.length() != 0 &&
+                mPassword.length() >= 8 && Charset.forName("UTF-8").encode(mSsidString).limit() <= 32
+    }
+
+    override fun onClick(view: View) {
+        mPassword.inputType = InputType.TYPE_CLASS_TEXT or if ((view as CheckBox).isChecked)
+            InputType.TYPE_TEXT_VARIATION_VISIBLE_PASSWORD
+        else
+            InputType.TYPE_TEXT_VARIATION_PASSWORD
+    }
+
+    override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) { }
+    override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) { }
+    override fun afterTextChanged(editable: Editable) {
+        validate()
+    }
+}

mobile/src/main/java/be/mygod/vpnhotspot/net/wifi/WifiApManager.kt

@@ -1,4 +1,4 @@
-package be.mygod.vpnhotspot.net
+package be.mygod.vpnhotspot.net.wifi
 
 import android.content.Context
 import android.net.wifi.WifiConfiguration

mobile/src/main/java/be/mygod/vpnhotspot/net/wifi/WifiP2pManagerHelper.kt

@@ -1,4 +1,4 @@
-package be.mygod.vpnhotspot.net
+package be.mygod.vpnhotspot.net.wifi
 
 import android.annotation.SuppressLint
 import android.net.wifi.WpsInfo