[dart:io] Loosen the HTTP header size limit

The `HttpClient` and `HttpServer` clasess now have a 1 MiB limit for the
total size of the HTTP headers when parsing a request or response,
instead of the former 8 KiB limit for each header name and value. This
limit cannot be configured at this time.

Bug: flutter/flutter#56580
Change-Id: I5f094df32a93ec3e6645a0d69d8cf8263082775a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/150500
Commit-Queue: Zichang Guo <zichangguo@google.com>
Reviewed-by: Jonas Termansen <sortie@google.com>

Author: zichangg

CHANGELOG.md

@@ -8,6 +8,10 @@
     to cancel outgoing HTTP requests and stop following IO operations.
 *   A validation check is added to `path` of class `Cookie`. Having characters
     ranging from 0x00 to 0x1f and 0x3b (";") will lead to a `FormatException`.
+*   The `HttpClient` and `HttpServer` clasess now have a 1 MiB limit for the
+    total size of the HTTP headers when parsing a request or response, instead
+    of the former 8 KiB limit for each header name and value. This limit cannot
+    be configured at this time.
 
 #### `dart:typed_data`
 

sdk/lib/_http/http_parser.dart

@@ -236,6 +236,7 @@ class _HttpParser extends Stream<_HttpIncoming> {
   Uint8List? _buffer;
   int _index = -1;
 
+  // Whether a HTTP request is being parsed (as opposed to a response).
   final bool _requestParser;
   int _state = _State.START;
   int? _httpVersionIndex;
@@ -246,8 +247,8 @@ class _HttpParser extends Stream<_HttpIncoming> {
   final List<int> _uriOrReasonPhrase = [];
   final List<int> _headerField = [];
   final List<int> _headerValue = [];
-  // The limit for method, uriOrReasonPhrase, header field and value
-  int _headerSizeLimit = 8 * 1024;
+  static const _headerTotalSizeLimit = 1024 * 1024;
+  int _headersReceivedSize = 0;
 
   int _httpVersion = _HttpVersion.UNDETERMINED;
   int _transferLength = -1;
@@ -946,6 +947,7 @@ class _HttpParser extends Stream<_HttpIncoming> {
     _messageType = _MessageType.UNDETERMINED;
     _headerField.clear();
     _headerValue.clear();
+    _headersReceivedSize = 0;
     _method.clear();
     _uriOrReasonPhrase.clear();
 
@@ -977,8 +979,7 @@ class _HttpParser extends Stream<_HttpIncoming> {
   }
 
   static bool _isValueChar(int byte) {
-    return (byte > 31 && byte < 128) ||
-        (byte == _CharCode.HT);
+    return (byte > 31 && byte < 128) || (byte == _CharCode.HT);
   }
 
   static List<String> _tokenizeFieldValue(String headerValue) {
@@ -1036,7 +1037,8 @@ class _HttpParser extends Stream<_HttpIncoming> {
   }
 
   void _addWithValidation(List<int> list, int byte) {
-    if (list.length < _headerSizeLimit) {
+    _headersReceivedSize++;
+    if (_headersReceivedSize < _headerTotalSizeLimit) {
       list.add(byte);
     } else {
       _reportSizeLimitError();
@@ -1074,7 +1076,8 @@ class _HttpParser extends Stream<_HttpIncoming> {
         throw UnsupportedError("Unexpected state: $_state");
         break;
     }
-    throw HttpException("$method exceeds the $_headerSizeLimit size limit");
+    throw HttpException(
+        "$method exceeds the $_headerTotalSizeLimit size limit");
   }
 
   _HttpIncoming _createIncoming(int transferLength) {

tests/standalone/io/http_big_header_test.dart

@@ -0,0 +1,81 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:expect/expect.dart';
+
+// This test checks whether a big header is accepted.
+
+Future<void> testClient(int limit) async {
+  final server = await HttpServer.bind('127.0.0.1', 0);
+  final str = 'a' * (1000);
+  int size = 0;
+  server.listen((request) async {
+    for (int i = 0; i < 10000; i++) {
+      request.response.headers.add('dummy', str);
+      size += 1000;
+      if (size > limit) {
+        break;
+      }
+    }
+    await request.response.close();
+    server.close();
+  });
+
+  final client = HttpClient();
+  final request = await client.get('127.0.0.1', server.port, '/');
+  await request.close();
+}
+
+Future<void> client() async {
+  int i = 64;
+  try {
+    for (; i < 101 * 1024 * 1024; i *= 100) {
+      await testClient(i);
+    }
+  } on HttpException catch (e) {
+    Expect.isTrue(e.toString().contains('size limit'));
+    Expect.isTrue(i > 1024 * 1024);
+    return;
+  }
+  Expect.fail('An exception is expected');
+}
+
+Future<void> testServer(int limit, int port) async {
+  final str = 'a' * (1000);
+  final client = HttpClient();
+  final request = await client.get('127.0.0.1', port, '/');
+  for (int size = 0; size < limit; size += 1000) {
+    request.headers.add('dummy', str);
+  }
+  await request.close();
+}
+
+Future<void> server() async {
+  final server = await HttpServer.bind('127.0.0.1', 0);
+  int i = 64;
+  try {
+    server.listen((request) async {
+      await request.response.close();
+    });
+    for (; i < 101 * 1024 * 1024; i *= 100) {
+      print(i);
+      await testServer(i, server.port);
+    }
+  } on SocketException catch (_) {
+    // Server will close on error and writing to the socket will be blocked due
+    // to broken pipe.
+    Expect.isTrue(i > 1024 * 1024);
+    server.close();
+    return;
+  }
+  server.close();
+  Expect.fail('An exception is expected');
+}
+
+Future<void> main() async {
+  await client();
+  await server();
+}

tests/standalone_2/io/http_big_header_test.dart

@@ -0,0 +1,81 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:expect/expect.dart';
+
+// This test checks whether a big header is accepted.
+
+Future<void> testClient(int limit) async {
+  final server = await HttpServer.bind('127.0.0.1', 0);
+  final str = 'a' * (1000);
+  int size = 0;
+  server.listen((request) async {
+    for (int i = 0; i < 10000; i++) {
+      request.response.headers.add('dummy', str);
+      size += 1000;
+      if (size > limit) {
+        break;
+      }
+    }
+    await request.response.close();
+    server.close();
+  });
+
+  final client = HttpClient();
+  final request = await client.get('127.0.0.1', server.port, '/');
+  await request.close();
+}
+
+Future<void> client() async {
+  int i = 64;
+  try {
+    for (; i < 101 * 1024 * 1024; i *= 100) {
+      await testClient(i);
+    }
+  } on HttpException catch (e) {
+    Expect.isTrue(e.toString().contains('size limit'));
+    Expect.isTrue(i > 1024 * 1024);
+    return;
+  }
+  Expect.fail('An exception is expected');
+}
+
+Future<void> testServer(int limit, int port) async {
+  final str = 'a' * (1000);
+  final client = HttpClient();
+  final request = await client.get('127.0.0.1', port, '/');
+  for (int size = 0; size < limit; size += 1000) {
+    request.headers.add('dummy', str);
+  }
+  await request.close();
+}
+
+Future<void> server() async {
+  final server = await HttpServer.bind('127.0.0.1', 0);
+  int i = 64;
+  try {
+    server.listen((request) async {
+      await request.response.close();
+    });
+    for (; i < 101 * 1024 * 1024; i *= 100) {
+      print(i);
+      await testServer(i, server.port);
+    }
+  } on SocketException catch (_) {
+    // Server will close on error and writing to the socket will be blocked due
+    // to broken pipe.
+    Expect.isTrue(i > 1024 * 1024);
+    server.close();
+    return;
+  }
+  server.close();
+  Expect.fail('An exception is expected');
+}
+
+Future<void> main() async {
+  await client();
+  await server();
+}