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vonzshik wants to merge 2 commits into from
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Enforcing the frame size for read #3782

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498bd5e
Enforcing the frame size for read
vonzshik May 24, 2021
e12bd66
Added a frame struct
vonzshik May 24, 2021
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29 changes: 29 additions & 0 deletions src/Npgsql/Internal/NpgsqlConnector.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -468,6 +468,10 @@ internal async Task Open(NpgsqlTimeout timeout, bool async, CancellationToken ca
{
await Authenticate(username, timeout, async, cancellationToken);

#if DEBUG
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@roji roji May 28, 2021

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Rather than wrapping each call with #if DEBUG, the methods themselves can have [Conditional("DEBUG")]. This automatically does what we want, and makes the call sites much nicer.

ReadBuffer.EnableFrameTracking = true;
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@roji roji May 28, 2021

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Any particular reason this shouldn't always be on (in DEBUG)? We could also use it to catch bugs in the Startup message and in authentication...

#endif

// We treat BackendKeyData as optional because some PostgreSQL-like database
// don't send it (CockroachDB, CrateDB)
var msg = await ReadMessage(async);
Expand Down Expand Up @@ -1178,6 +1182,10 @@ internal ValueTask<IBackendMessage> ReadMessage(bool async, DataRowLoadingMode d
return ReadMessageLong(this, async, dataRowLoadingMode, readingNotifications: readingNotifications);
}

#if DEBUG
ReadBuffer.NextFrame();
#endif

var messageCode = (BackendMessageCode)ReadBuffer.ReadByte();
switch (messageCode)
{
Expand All @@ -1186,6 +1194,9 @@ internal ValueTask<IBackendMessage> ReadMessage(bool async, DataRowLoadingMode d
case BackendMessageCode.ParameterStatus:
case BackendMessageCode.ErrorResponse:
ReadBuffer.ReadPosition--;
#if DEBUG
ReadBuffer.ResetFrame();
#endif
return ReadMessageLong(this, async, dataRowLoadingMode, readingNotifications: false);
case BackendMessageCode.ReadyForQuery:
break;
Expand All @@ -1196,6 +1207,9 @@ internal ValueTask<IBackendMessage> ReadMessage(bool async, DataRowLoadingMode d
if (len > ReadBuffer.ReadBytesLeft)
{
ReadBuffer.ReadPosition -= 5;
#if DEBUG
ReadBuffer.ResetFrame();
#endif
return ReadMessageLong(this, async, dataRowLoadingMode, readingNotifications: false);
}

Expand Down Expand Up @@ -1233,6 +1247,9 @@ internal ValueTask<IBackendMessage> ReadMessage(bool async, DataRowLoadingMode d
while (true)
{
await connector.ReadBuffer.Ensure(5, async, readingNotifications);
#if DEBUG
connector.ReadBuffer.NextFrame();
#endif
var messageCode = (BackendMessageCode)connector.ReadBuffer.ReadByte();
PGUtil.ValidateBackendMessageCode(messageCode);
var len = connector.ReadBuffer.ReadInt32() - 4; // Transmitted length includes itself
Expand All @@ -1244,6 +1261,9 @@ internal ValueTask<IBackendMessage> ReadMessage(bool async, DataRowLoadingMode d
if (dataRowLoadingMode == DataRowLoadingMode.Skip)
{
await connector.ReadBuffer.Skip(len, async);
#if DEBUG
connector.ReadBuffer.ResetFrame();
#endif
continue;
}
}
Expand Down Expand Up @@ -1289,6 +1309,10 @@ internal ValueTask<IBackendMessage> ReadMessage(bool async, DataRowLoadingMode d
throw connector.Break(error);
}

#if DEBUG
connector.ReadBuffer.ResetFrame();
#endif

continue;

case BackendMessageCode.ReadyForQuery:
Expand All @@ -1307,7 +1331,12 @@ internal ValueTask<IBackendMessage> ReadMessage(bool async, DataRowLoadingMode d
case BackendMessageCode.ParameterStatus:
Debug.Assert(msg == null);
if (!readingNotifications)
{
#if DEBUG
connector.ReadBuffer.ResetFrame();
#endif
continue;
}
return null;
}

Expand Down
103 changes: 103 additions & 0 deletions src/Npgsql/Internal/NpgsqlReadBuffer.cs
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Expand Up @@ -74,7 +74,87 @@ internal TimeSpan Timeout
/// </summary>
internal Encoding RelaxedTextEncoding { get; }

#if DEBUG
internal bool EnableFrameTracking { get; set; }

internal void NextFrame()
{
Debug.Assert(_currentFrame.LengthLeft == 0, "Protocol failure");
_inFrame = false;
}

internal void ResetFrame()
{
_inFrame = true;
if (_previousFrame.HasValue)
_currentFrame = _previousFrame.Value;
}

bool _inFrame;

bool _bufferReset;

struct Frame
{
public Frame(byte code, int length, int lengthLeft)
{
Code = code;
Length = length;
LengthLeft = lengthLeft;
}

public readonly byte Code;
public readonly int Length;
public int LengthLeft;
}

Frame _currentFrame;
Frame? _previousFrame;

int _readPosition;

internal int ReadPosition
{
get => _readPosition;
set
{
if (EnableFrameTracking)
{
var positionDelta = value - _readPosition;

// Setting the same position as the one we already have
if (positionDelta == 0)
return;

// Buffer reset
if (!_bufferReset)
{
if (!_inFrame)
{
Debug.Assert(positionDelta == 1, "Protocol failure");
Debug.Assert(ReadBytesLeft >= 5);
var frameCode = Buffer[_readPosition];
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@roji roji May 28, 2021

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Convert to BackendMessageCode?

var frameLength = BinaryPrimitives.ReverseEndianness(Unsafe.ReadUnaligned<int>(ref Buffer[_readPosition + 1])) + 1;
var frameLengthLeft = frameLength - 1;
_previousFrame = _currentFrame;
_currentFrame = new Frame(frameCode, frameLength, frameLengthLeft);
_inFrame = true;
}
else
{
_currentFrame.LengthLeft -= positionDelta;
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@roji roji May 28, 2021

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nit: maybe better to have Position (in the frame) - just like the the buffer's ReadPosition - which gets incremented, rather than LengthLeft which gets decremented.

Debug.Assert(_currentFrame.LengthLeft <= _currentFrame.Length && _currentFrame.LengthLeft >= 0, "Going outside of frame bounds");
}
}
}

_readPosition = value;
}
}
#else
internal int ReadPosition { get; set; }
#endif

internal int ReadBytesLeft => FilledBytes - ReadPosition;

internal readonly byte[] Buffer;
Expand Down Expand Up @@ -159,9 +239,17 @@ static async Task EnsureLong(
}
else if (count > buffer.Size - buffer.FilledBytes)
{
#if DEBUG
buffer._bufferReset = true;
#endif

Array.Copy(buffer.Buffer, buffer.ReadPosition, buffer.Buffer, 0, buffer.ReadBytesLeft);
buffer.FilledBytes = buffer.ReadBytesLeft;
buffer.ReadPosition = 0;

#if DEBUG
buffer._bufferReset = false;
#endif
}

var finalCt = async && buffer.Timeout != TimeSpan.Zero
Expand Down Expand Up @@ -277,6 +365,15 @@ internal NpgsqlReadBuffer AllocateOversize(int count)
tempBuf.Timeout = Timeout;
CopyTo(tempBuf);
Clear();

#if DEBUG
tempBuf._currentFrame = _currentFrame;
tempBuf._previousFrame = _previousFrame;
tempBuf._inFrame = _inFrame;
tempBuf.EnableFrameTracking = EnableFrameTracking;
ResetFrame();
#endif

return tempBuf;
}

Expand Down Expand Up @@ -637,8 +734,14 @@ public void Dispose()

internal void Clear()
{
#if DEBUG
_bufferReset = true;
#endif
ReadPosition = 0;
FilledBytes = 0;
#if DEBUG
_bufferReset = false;
#endif
}

internal void CopyTo(NpgsqlReadBuffer other)
Expand Down
8 changes: 8 additions & 0 deletions src/Npgsql/NpgsqlDataReader.cs
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Expand Up @@ -232,11 +232,19 @@ public override Task<bool> ReadAsync(CancellationToken cancellationToken)
var readBuf = Connector.ReadBuffer;
if (readBuf.ReadBytesLeft < 5)
return null;

#if DEBUG
readBuf.NextFrame();
#endif

var messageCode = (BackendMessageCode)readBuf.ReadByte();
var len = readBuf.ReadInt32() - 4; // Transmitted length includes itself
if (messageCode != BackendMessageCode.DataRow || readBuf.ReadBytesLeft < len)
{
readBuf.ReadPosition -= 5;
#if DEBUG
readBuf.ResetFrame();
#endif
return null;
}

Expand Down
3 changes: 2 additions & 1 deletion src/Npgsql/NpgsqlNestedDataReader.cs
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Expand Up @@ -381,13 +381,14 @@ public override bool Read()
{
CheckResultSet();

Buffer.ReadPosition = _nextRowBufferPos;
if (_nextRowIndex == _numRows)
{
_readerState = ReaderState.AfterRows;
return false;
}

Buffer.ReadPosition = _nextRowBufferPos;

if (_nextRowIndex++ != 0)
Buffer.ReadInt32(); // Length of record

Expand Down
8 changes: 4 additions & 4 deletions test/Npgsql.Tests/Support/PgServerMock.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -325,7 +325,7 @@ internal PgServerMock WriteCopyInResponse()
{
CheckDisposed();
_writeBuffer.WriteByte((byte)BackendMessageCode.CopyInResponse);
_writeBuffer.WriteInt32(5);
_writeBuffer.WriteInt32(9);
_writeBuffer.WriteByte(0);
_writeBuffer.WriteInt16(1);
_writeBuffer.WriteInt16(0);
Expand All @@ -341,9 +341,9 @@ internal PgServerMock WriteErrorResponse(string code, string severity, string me
_writeBuffer.WriteByte((byte)BackendMessageCode.ErrorResponse);
_writeBuffer.WriteInt32(
4 +
1 + Encoding.GetByteCount(code) +
1 + Encoding.GetByteCount(severity) +
1 + Encoding.GetByteCount(message) +
1 + Encoding.GetByteCount(code) + 1 +
1 + Encoding.GetByteCount(severity) + 1 +
1 + Encoding.GetByteCount(message) + 1 +
1);
_writeBuffer.WriteByte((byte)ErrorOrNoticeMessage.ErrorFieldTypeCode.Code);
_writeBuffer.WriteNullTerminatedString(code);
Expand Down