Add back AES256 key assignment (from TODO list)

TODO.md

@@ -1,7 +1,6 @@
 # Remaining tasks before declaring 1.0
 
 * add a low level settings screen (let user change any of the RadioConfig parameters)
-* if user edits the channel, generate a new AES256 key
 * add play store link with https://developers.google.com/analytics/devguides/collection/android/v4/campaigns#google-play-url-builder and the play icon
 
 Things for the betaish period.

app/src/main/java/com/geeksville/mesh/model/Channel.kt

@@ -14,10 +14,12 @@ data class Channel(
     val settings: MeshProtos.ChannelSettings = MeshProtos.ChannelSettings.getDefaultInstance()
 ) {
     companion object {
+        // Note: this string _SHOULD NOT BE LOCALIZED_ because it directly hashes to values used on the device for the default channel name.
+        val defaultChannelName = "Default"
+
         // Placeholder when emulating
         val emulated = Channel(
-            // Note: this string _SHOULD NOT BE LOCALIZED_ because it directly hashes to values used on the device for the default channel name.
-            MeshProtos.ChannelSettings.newBuilder().setName("Default")
+            MeshProtos.ChannelSettings.newBuilder().setName(defaultChannelName)
                 .setModemConfig(MeshProtos.ChannelSettings.ModemConfig.Bw125Cr45Sf128).build()
         )
 

app/src/main/java/com/geeksville/mesh/ui/ChannelFragment.kt

@@ -18,12 +18,15 @@ import com.geeksville.android.GeeksvilleApplication
 import com.geeksville.android.Logging
 import com.geeksville.android.hideKeyboard
 import com.geeksville.mesh.R
+import com.geeksville.mesh.model.Channel
 import com.geeksville.mesh.model.UIViewModel
 import com.geeksville.mesh.service.MeshService
 import com.geeksville.util.Exceptions
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
 import com.google.android.material.snackbar.Snackbar
+import com.google.protobuf.ByteString
 import kotlinx.android.synthetic.main.channel_fragment.*
+import java.security.SecureRandom
 
 
 // Make an image view dim
@@ -142,7 +145,15 @@ class ChannelFragment : ScreenFragment("Channel"), Logging {
                         UIViewModel.getChannel(model.radioConfig.value)?.let { old ->
                             val newSettings = old.settings.toBuilder()
                             newSettings.name = channelNameEdit.text.toString().trim()
-                            // FIXME, regenerate a new preshared key!
+
+                            // Generate a new AES256 key (for any channel not named Default)
+                            if (newSettings.name != Channel.defaultChannelName) {
+                                debug("ASSIGNING NEW AES256 KEY")
+                                val random = SecureRandom()
+                                val bytes = ByteArray(32)
+                                random.nextBytes(bytes)
+                                newSettings.psk = ByteString.copyFrom(bytes)
+                            }
 
                             // Try to change the radio, if it fails, tell the user why and throw away their redits
                             try {
@@ -150,7 +161,7 @@ class ChannelFragment : ScreenFragment("Channel"), Logging {
                                 // Since we are writing to radioconfig, that will trigger the rest of the GUI update (QR code etc)
                             } catch (ex: RemoteException) {
                                 setGUIfromModel() // Throw away user edits
-                                
+
                                 // Tell the user to try again
                                 Snackbar.make(
                                     editableCheckbox,