feat: address review comments

- in ping response, daemon says whether or not it accepts public keys from the client
- added abbreviations in SshnpArg for the new flags
- corrected some code comments and added to others

packages/dart/noports_core/lib/src/common/features.dart

@@ -1,5 +1,9 @@
 /// Features which can be supported by the NoPorts Daemon
 enum DaemonFeatures {
+  /// daemon will accept public keys sent by clients (i.e. daemon has been
+  /// started with the `--sshpublickey` or `-s` flag)
+  acceptsPublicKeys,
+
   /// authenticate when connecting to the Socket Rendezvous (sr)
   srAuth,
 

packages/dart/noports_core/lib/src/sshnp/models/sshnp_arg.dart

@@ -352,6 +352,7 @@ class SshnpArg {
   );
   static const authenticateClientToRvdArg = SshnpArg(
     name: 'authenticate-client-to-rvd',
+    abbr: 'a',
     help: 'When false, client will not authenticate itself to rvd',
     defaultsTo: DefaultArgs.authenticateClientToRvd,
     format: ArgFormat.flag,
@@ -360,6 +361,7 @@ class SshnpArg {
   );
   static const authenticateDeviceToRvdArg = SshnpArg(
     name: 'authenticate-device-to-rvd',
+    abbr: 'A',
     help: 'When false, device will not authenticate to the socket rendezvous',
     defaultsTo: DefaultArgs.authenticateDeviceToRvd,
     format: ArgFormat.flag,
@@ -368,6 +370,7 @@ class SshnpArg {
   );
   static const encryptRvdTrafficArg = SshnpArg(
     name: 'encrypt-rvd-traffic',
+    abbr: 'E',
     help: 'When true, traffic via the socket rendezvous is encrypted,'
         ' in addition to whatever encryption the traffic already has'
         ' (e.g. an ssh session)',
@@ -378,6 +381,7 @@ class SshnpArg {
   );
   static const discoverDaemonFeaturesArg = SshnpArg(
     name: 'discover-daemon-features',
+    abbr: 'F',
     help: 'When this flag is set, this client starts by pinging the daemon to'
         ' discover what features it supports, and exits if this client has '
         ' requested use of a feature which the daemon does not support.'

packages/dart/noports_core/lib/src/sshnp/util/sshnpd_channel/sshnpd_channel.dart

@@ -86,9 +86,8 @@ abstract class SshnpdChannel with AsyncInitialization, AtClientBindings {
   @protected
   Future<SshnpdAck> handleSshnpdPayload(AtNotification notification);
 
-  /// Wait until we've received an acknowledgement from the daemon.
-  /// Returns true if the daemon acknowledged our request.
-  /// Returns false if a timeout occurred.
+  /// Wait until we've received an acknowledgement from the daemon, or
+  /// have timed out while waiting.
   Future<SshnpdAck> waitForDaemonResponse({int maxWaitMillis = 15000}) async {
     // Timer to timeout after 10 Secs or after the Ack of connected/Errors
     for (int counter = 1; counter <= 100; counter++) {

packages/dart/noports_core/lib/src/sshnpd/sshnpd_impl.dart

@@ -309,6 +309,7 @@ class SshnpdImpl implements Sshnpd {
       'supportedFeatures': {
         DaemonFeatures.srAuth.name: true,
         DaemonFeatures.srE2ee.name: true,
+        DaemonFeatures.acceptsPublicKeys.name: addSshPublicKeys,
       },
     };
     unawaited(

packages/dart/noports_core/lib/src/sshrvd/signature_verifying_socket_authenticator.dart

@@ -49,6 +49,19 @@ class SignatureAuthVerifier {
     return atChops.verify(input);
   }
 
+  /// We expect the authenticating client to send a JSON message with
+  /// this structure:
+  /// ```json
+  /// {
+  /// "signature":"<signature>",
+  /// "hashingAlgo":"<algo>",
+  /// "signingAlgo":"<algo>",
+  /// "payload":<the data which was signed>
+  /// }
+  /// ```
+  /// The signature is verified against [dataToVerify] and, although not
+  /// strictly necessary, the rvdNonce is also checked in what the client
+  /// send in the payload
   Future<(bool, Stream<Uint8List>?)> authenticate(Socket socket) async {
     Completer<(bool, Stream<Uint8List>?)> completer = Completer();
     bool authenticated = false;
@@ -61,13 +74,6 @@ class SignatureAuthVerifier {
         try {
           final message = String.fromCharCodes(data);
           logger.info('SignatureAuthVerifier $tag received data: $message');
-          // Expected message to be the JSON format with the below structure:
-          // {
-          // "signature":"<signature>",
-          // "hashingAlgo":"<algo>",
-          // "signingAlgo":"<algo>",
-          // "payload":{<the data which was signed>}
-          // }
           var envelope = jsonDecode(message);
 
           final hashingAlgo =