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#13 - Utf8 validation.
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‎src/Microsoft.AspNet.WebSockets.Protocol/CommonWebSocket.cs‎

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Original file line numberDiff line numberDiff line change
@@ -40,6 +40,7 @@ public class CommonWebSocket : WebSocket
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private long _frameBytesRemaining;
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private int? _firstDataOpCode;
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private int _dataUnmaskOffset;
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private Utilities.Utf8MessageState _incomingUtf8MessageState = new Utilities.Utf8MessageState();
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public CommonWebSocket(Stream stream, string subProtocol, TimeSpan keepAliveInterval, int receiveBufferSize, bool maskOutput, bool useZeroMask, bool unmaskInput)
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{
@@ -251,6 +252,14 @@ public async override Task<WebSocketReceiveResult> ReceiveAsync(ArraySegment<byt
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WebSocketReceiveResult result;
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WebSocketMessageType messageType = Utilities.GetMessageType(opCode);
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if (messageType == WebSocketMessageType.Text
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&& !Utilities.TryValidateUtf8(new ArraySegment<byte>(buffer.Array, buffer.Offset, bytesToCopy), _frameInProgress.Fin, _incomingUtf8MessageState))
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{
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await CloseOutputAsync(WebSocketCloseStatus.InvalidPayloadData, string.Empty, cancellationToken);
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throw new InvalidOperationException("An invalid UTF-8 payload was received.");
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}
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if (bytesToCopy == _frameBytesRemaining)
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{
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result = new WebSocketReceiveResult(bytesToCopy, messageType, _frameInProgress.Fin);

‎src/Microsoft.AspNet.WebSockets.Protocol/Utilities.cs‎

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Original file line numberDiff line numberDiff line change
@@ -69,5 +69,77 @@ public static WebSocketMessageType GetMessageType(int opCode)
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default: throw new NotImplementedException(opCode.ToString());
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}
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}
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// For now this is stateless and does not handle sequences spliced across messages.
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// http://etutorials.org/Programming/secure+programming/Chapter+3.+Input+Validation/3.12+Detecting+Illegal+UTF-8+Characters/
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public static bool TryValidateUtf8(ArraySegment<byte> arraySegment, bool endOfMessage, Utf8MessageState state)
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{
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for (int i = arraySegment.Offset; i < arraySegment.Offset + arraySegment.Count; )
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{
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if (!state.SequenceInProgress)
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{
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state.SequenceInProgress = true;
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byte b = arraySegment.Array[i];
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if ((b & 0x80) == 0) // 0bbbbbbb, single byte
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{
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state.AdditionalBytesExpected = 0;
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}
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else if ((b & 0xC0) == 0x80)
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{
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return false; // Misplaced 10bbbbbb byte. This cannot be the first byte.
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}
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else if ((b & 0xE0) == 0xC0) // 110bbbbb 10bbbbbb
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{
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state.AdditionalBytesExpected = 1;
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}
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else if ((b & 0xF0) == 0xE0) // 1110bbbb 10bbbbbb 10bbbbbb
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{
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state.AdditionalBytesExpected = 2;
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}
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else if ((b & 0xF8) == 0xF0) // 11110bbb 10bbbbbb 10bbbbbb 10bbbbbb
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{
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state.AdditionalBytesExpected = 3;
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}
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else if ((b & 0xFC) == 0xF8) // 111110bb 10bbbbbb 10bbbbbb 10bbbbbb 10bbbbbb
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{
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state.AdditionalBytesExpected = 4;
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}
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else if ((b & 0xFE) == 0xFC) // 1111110b 10bbbbbb 10bbbbbb 10bbbbbb 10bbbbbb 10bbbbbb
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{
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state.AdditionalBytesExpected = 5;
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}
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else // 11111110 && 11111111 are not valid
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{
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return false;
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}
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i++;
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}
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while (state.AdditionalBytesExpected > 0 && i < arraySegment.Offset + arraySegment.Count)
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{
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byte b = arraySegment.Array[i];
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if ((b & 0xC0) != 0x80)
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{
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return false;
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}
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state.AdditionalBytesExpected--;
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i++;
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}
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if (state.AdditionalBytesExpected == 0)
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{
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state.SequenceInProgress = false;
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}
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}
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if (endOfMessage && state.SequenceInProgress)
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{
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return false;
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}
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return true;
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}
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public class Utf8MessageState
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{
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public bool SequenceInProgress { get; set; }
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public int AdditionalBytesExpected { get; set; }
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}
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}
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}

‎test/Microsoft.AspNet.WebSockets.Protocol.Test/Utf8ValidationTests.cs‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,62 @@
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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
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// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
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using System;
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using System.Text;
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using Xunit;
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namespace Microsoft.AspNet.WebSockets.Protocol.Test
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{
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public class Utf8ValidationTests
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{
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[Theory]
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[InlineData(new byte[] { })]
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[InlineData(new byte[] { 0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x20, 0x57, 0x6F, 0x72, 0x6C, 0x64 })] // Hello World
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[InlineData(new byte[] { 0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x2D, 0xC2, 0xB5, 0x40, 0xC3, 0x9F, 0xC3, 0xB6, 0xC3, 0xA4, 0xC3, 0xBC, 0xC3, 0xA0, 0xC3, 0xA1 })] // "Hello-µ@ßöäüàá";
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public void ValidateSingleValidSegments_Valid(byte[] data)
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{
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var state = new Utilities.Utf8MessageState();
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Assert.True(Utilities.TryValidateUtf8(new ArraySegment<byte>(data), endOfMessage: true, state: state));
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}
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[Theory]
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[InlineData(new byte[] { }, new byte[] { }, new byte[] { })]
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[InlineData(new byte[] { 0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x20 }, new byte[] { }, new byte[] { 0x57, 0x6F, 0x72, 0x6C, 0x64 })] // Hello ,, World
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[InlineData(new byte[] { 0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x2D, 0xC2, }, new byte[] { 0xB5, 0x40, 0xC3, 0x9F, 0xC3, 0xB6, 0xC3, 0xA4, }, new byte[] { 0xC3, 0xBC, 0xC3, 0xA0, 0xC3, 0xA1 })] // "Hello-µ@ßöäüàá";
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public void ValidateMultipleValidSegments_Valid(byte[] data1, byte[] data2, byte[] data3)
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{
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var state = new Utilities.Utf8MessageState();
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Assert.True(Utilities.TryValidateUtf8(new ArraySegment<byte>(data1), endOfMessage: false, state: state));
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Assert.True(Utilities.TryValidateUtf8(new ArraySegment<byte>(data2), endOfMessage: false, state: state));
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Assert.True(Utilities.TryValidateUtf8(new ArraySegment<byte>(data3), endOfMessage: true, state: state));
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}
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[Theory]
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[InlineData(new byte[] { 0xfe })]
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[InlineData(new byte[] { 0xff })]
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[InlineData(new byte[] { 0xfe, 0xfe, 0xff, 0xff })]
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// [InlineData(new byte[] { 0xc0, 0xaf })]
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// [InlineData(new byte[] { 0xe0, 0x80, 0xaf })]
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// [InlineData(new byte[] { 0xf4, 0x90, 0x80, 0x80 })]
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// [InlineData(new byte[] { 0xf0, 0x80, 0x80, 0xaf })]
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// [InlineData(new byte[] { 0xf8, 0x80, 0x80, 0x80, 0xaf })]
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// [InlineData(new byte[] { 0xfc, 0x80, 0x80, 0x80, 0x80, 0xaf })]
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// [InlineData(new byte[] { 0xc1, 0xbf })]
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// [InlineData(new byte[] { 0xed, 0xa0, 0x80, 0x65, 0x64, 0x69, 0x74, 0x65, 0x64 })] // 0xEDA080 decodes to 0xD800, which is a reserved high surrogate character.
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public void ValidateSingleInvalidSegment_Invalid(byte[] data)
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{
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var state = new Utilities.Utf8MessageState();
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Assert.False(Utilities.TryValidateUtf8(new ArraySegment<byte>(data), endOfMessage: true, state: state));
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}
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/*
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[Theory]
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// [InlineData(true, new byte[] { 0xce, 0xba, 0xe1, 0xbd, 0xb9, 0xcf, 0x83, 0xce, 0xbc, 0xce, 0xb5, 0xf4 }, false, new byte[] { 0x90 }, true, new byte[] { })]
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public void ValidateMultipleInvalidSegments_Invalid(bool valid1, byte[] data1, bool valid2, byte[] data2, bool valid3, byte[] data3)
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{
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var state = new Utilities.Utf8MessageState();
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Assert.True(valid1 == Utilities.TryValidateUtf8(new ArraySegment<byte>(data1), endOfMessage: false, state: state), "1st");
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Assert.True(valid2 == Utilities.TryValidateUtf8(new ArraySegment<byte>(data2), endOfMessage: false, state: state), "2nd");
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Assert.True(valid3 == Utilities.TryValidateUtf8(new ArraySegment<byte>(data3), endOfMessage: true, state: state), "3rd");
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}*/
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}
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}

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