Fix CRA authenticate to include salt

Author: muzzammilshahid

lib/src/auth/wampcra.dart

@@ -3,6 +3,7 @@ import "dart:math";
 import "dart:typed_data";
 
 import "package:crypto/crypto.dart";
+import "package:pointycastle/pointycastle.dart";
 import "package:wampproto/messages.dart";
 import "package:wampproto/src/auth/auth.dart";
 
@@ -14,11 +15,36 @@ class WAMPCRAAuthenticator extends IClientAuthenticator {
 
   @override
   Authenticate authenticate(Challenge challenge) {
-    String signed = signWampCRAChallenge(challenge.extra["challenge"], utf8.encode(_secret));
+    Uint8List? rawSecret;
+    String? saltStr = challenge.extra["salt"] as String?;
+    if (saltStr != null && saltStr.isNotEmpty) {
+      int iters = challenge.extra["iterations"] as int? ?? 0;
+      int keylen = challenge.extra["keylen"] as int? ?? 32;
+
+      rawSecret = deriveCRAKey(saltStr, _secret, iters, keylen);
+    } else {
+      rawSecret = Uint8List.fromList(utf8.encode(_secret));
+    }
+
+    String signed = signWampCRAChallenge(challenge.extra["challenge"], rawSecret);
     return Authenticate(signed, {});
   }
 }
 
+Uint8List deriveCRAKey(String saltStr, String secret, int iterations, int keyLength) {
+  final salt = utf8.encode(saltStr);
+  final secretBytes = utf8.encode(secret);
+
+  final iter = iterations > 0 ? iterations : 1000;
+  final keyLen = keyLength > 0 ? keyLength : 32;
+
+  final params = Pbkdf2Parameters(Uint8List.fromList(salt), iter, keyLen);
+  final pbkdf2 = KeyDerivator("SHA-256/HMAC/PBKDF2")..init(params);
+  final derivedKey = pbkdf2.process(Uint8List.fromList(secretBytes));
+
+  return Uint8List.fromList(base64.encode(derivedKey).codeUnits);
+}
+
 String generateNonce() {
   final random = Random.secure();
   final nonceBytes = Uint8List.fromList(List.generate(16, (_) => random.nextInt(256)));

pubspec.yaml

@@ -13,6 +13,7 @@ dependencies:
   crypto: ^3.0.3
   msgpack_dart: ^1.0.1
   pinenacl: ^0.6.0
+  pointycastle: ^3.9.1
 
 dev_dependencies:
   lints: ^3.0.0

test/interoptests/auth_test.dart

@@ -2,6 +2,7 @@ import "package:pinenacl/ed25519.dart";
 import "package:test/test.dart";
 
 import "package:wampproto/auth.dart";
+import "package:wampproto/messages.dart";
 import "package:wampproto/src/auth/cryptosign.dart";
 import "package:wampproto/src/auth/wampcra.dart";
 
@@ -59,6 +60,19 @@ void main() {
     const testSecret = "private";
     var testSecretBytes = Uint8List.fromList(testSecret.codeUnits);
 
+    const String authID = "foo";
+    const String salt = "salt";
+    const int keyLength = 32;
+    const int iterations = 1000;
+    const String craChallenge =
+        '''{"nonce":"cdcb3b12d56e12825be99f38f55ba43f","authprovider":"provider","authid":"foo","authrole":"anonymous","authmethod":"wampcra","session":1,"timestamp":"2024-05-07T09:25:13.307Z"}''';
+    final Map<String, dynamic> authExtra = {
+      "challenge": craChallenge,
+      "salt": salt,
+      "iterations": iterations,
+      "keylen": keyLength,
+    };
+
     test("GenerateCRAChallenge", () async {
       var challenge = generateWampCRAChallenge(1, "anonymous", "anonymous", "static");
 
@@ -89,5 +103,29 @@ void main() {
       var isVerified = verifyWampCRASignature(signature.trim(), challenge.trim(), testSecretBytes);
       expect(isVerified, true);
     });
+
+    test("SignCRAChallengeWithSalt", () async {
+      final challenge = Challenge(WAMPCRAAuthenticator.type, authExtra);
+      final authenticator = WAMPCRAAuthenticator(authID, authExtra, testSecret);
+
+      final authenticate = authenticator.authenticate(challenge);
+      final saltSecret = await runCommand("auth cra derive-key $salt $testSecret -i $iterations -l $keyLength");
+
+      await runCommand("auth cra verify-signature $craChallenge ${authenticate.signature} ${saltSecret.trim()}");
+    });
+
+    test("VerifyCRASignatureWithSalt", () async {
+      final challenge = await runCommand("auth cra generate-challenge 1 $authID anonymous provider");
+      final saltSecret = await runCommand("auth cra derive-key $salt $testSecret -i $iterations -l $keyLength");
+
+      final signature = await runCommand("auth cra sign-challenge ${challenge.trim()} ${saltSecret.trim()}");
+
+      final isVerified = verifyWampCRASignature(
+        signature.trim(),
+        challenge.trim(),
+        Uint8List.fromList(saltSecret.trim().codeUnits),
+      );
+      expect(isVerified, true);
+    });
   });
 }