[common_crypto] add hmac sha256 calculator

Author: boyan01

packages/common_crypto/lib/src/aes.dart

@@ -6,16 +6,6 @@ import 'package:ffi/ffi.dart';
 import 'common_crypto_bindings_generated.dart';
 import 'tools.dart';
 
-extension _Uint8ListPointer on Uint8List {
-  Pointer<Uint8> get pointer {
-    final pointer = malloc<Uint8>(length);
-    for (var i = 0; i < length; i++) {
-      pointer[i] = this[i];
-    }
-    return pointer;
-  }
-}
-
 Uint8List _aesCrypt({
   required Uint8List key,
   required Uint8List data,

packages/common_crypto/lib/src/hmac.dart

@@ -0,0 +1,50 @@
+import 'dart:ffi';
+import 'dart:typed_data';
+
+import 'package:ffi/ffi.dart';
+
+import 'common_crypto_bindings_generated.dart';
+import 'tools.dart';
+
+const _kDigestDataCount = 32;
+
+class HMacSha256 implements Finalizable {
+  static Uint8List hmacSha256({
+    required Uint8List key,
+    required Uint8List data,
+  }) {
+    final hmac = HMacSha256(key);
+    hmac.update(data);
+    final result = hmac.finalize();
+    hmac.dispose();
+    return result;
+  }
+
+  final Uint8List key;
+
+  final context = malloc<CCHmacContext>();
+
+  HMacSha256(this.key) {
+    final keyRef = key.pointer;
+    bindings.CCHmacInit(context, kCCHmacAlgSHA256, keyRef.cast(), key.length);
+    malloc.free(keyRef);
+  }
+
+  void update(Uint8List data) {
+    final dataRef = data.pointer;
+    bindings.CCHmacUpdate(context, dataRef.cast(), data.length);
+    malloc.free(dataRef);
+  }
+
+  Uint8List finalize() {
+    final digest = malloc<Uint8>(_kDigestDataCount);
+    bindings.CCHmacFinal(context, digest.cast());
+    final result = Uint8List.fromList(digest.asTypedList(_kDigestDataCount));
+    malloc.free(digest);
+    return result;
+  }
+
+  void dispose() {
+    malloc.free(context);
+  }
+}

packages/common_crypto/lib/src/tools.dart

@@ -1,5 +1,8 @@
 import 'dart:ffi';
 import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:ffi/ffi.dart';
 
 import 'common_crypto_bindings_generated.dart';
 
@@ -12,3 +15,13 @@ final DynamicLibrary _dylib = () {
 
 /// The bindings to the native functions in [_dylib].
 final CommonCryptoBindings bindings = CommonCryptoBindings(_dylib);
+
+extension Uint8ListPointer on Uint8List {
+  Pointer<Uint8> get pointer {
+    final pointer = malloc<Uint8>(length);
+    for (var i = 0; i < length; i++) {
+      pointer[i] = this[i];
+    }
+    return pointer;
+  }
+}

packages/common_crypto/test/hmac_test.dart

@@ -0,0 +1,17 @@
+import 'dart:convert';
+import 'dart:typed_data';
+
+import 'package:common_crypto/src/hmac.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  test('hmac 256 test', () {
+    final key = base64Decode('Y9hRHsqr9adyX29DYsjWhg==');
+    final data = Uint8List.fromList(utf8.encode('Mixin'));
+    final result = HMacSha256.hmacSha256(key: key, data: data);
+    expect(
+      base64Encode(result),
+      equals('Zg/Z5GkXYHKPR/uPVOe4Z5ZPzSgRoDL72mrm5/TyCrQ='),
+    );
+  });
+}