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fix(csharp): fix double free in C# wrapper #411

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Merged
Kyle Bouchard (ptrstr) merged 1 commit into from
Aug 18, 2026
Merged

fix(csharp): fix double free in C# wrapper #411

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9 changes: 4 additions & 5 deletions wrappers/csharp/src/DecryptionStream.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,8 @@ public void FlushFinalBlock()
throw new NotSupportedException();
}

_finalBlockTransformed = true;

if (_inputBufferOffset > 0)
{
byte[] outputBuffer = DecryptLastChunk();
Expand All @@ -109,8 +111,6 @@ public void FlushFinalBlock()
}

Array.Clear(_inputBuffer, 0, _inputBuffer.Length);

_finalBlockTransformed = true;
}

public override void Flush()
Expand Down Expand Up @@ -188,14 +188,13 @@ private byte[] DecryptLastChunk()

long result = Native.OnlineDecryptorLastChunk(_native_ptr, _inputBuffer, (UIntPtr)_inputBufferOffset, aad, UIntPtr.Zero, outputBuffer, (UIntPtr)outputBuffer.Length);

_native_ptr = UIntPtr.Zero;

if (result < 0)
{
Utils.HandleError(result);
}

// Here, the pointer is freed, so let's set it to 0
_native_ptr = UIntPtr.Zero;

return outputBuffer;
}

Expand Down
9 changes: 4 additions & 5 deletions wrappers/csharp/src/EncryptionStream.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,8 @@ public void FlushFinalBlock()
throw new NotSupportedException();
}

_finalBlockTransformed = true;

if (_inputBufferOffset > 0)
{
byte[] outputBuffer = EncryptLastChunk();
Expand All @@ -97,8 +99,6 @@ public void FlushFinalBlock()
}

Array.Clear(_inputBuffer, 0, _inputBuffer.Length);

_finalBlockTransformed = true;
}

public override void Flush()
Expand Down Expand Up @@ -175,14 +175,13 @@ private byte[] EncryptLastChunk()

long result = Native.OnlineEncryptorLastChunk(_native_ptr, _inputBuffer, (UIntPtr)_inputBufferOffset, aad, UIntPtr.Zero, outputBuffer, (UIntPtr)outputBuffer.Length);

_native_ptr = UIntPtr.Zero;

if (result < 0)
{
Utils.HandleError(result);
}

// Here, the pointer is freed, so let's set it to 0
_native_ptr = UIntPtr.Zero;

return outputBuffer;
}

Expand Down
36 changes: 36 additions & 0 deletions wrappers/csharp/tests/unit-tests/TestStreams.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,5 +56,41 @@ public void DecryptStream()
Assert.IsTrue(result.Length == 1689);
Assert.IsTrue(Utils.EncodeToBase64String(result) == TestData.Base64TestDataStream);
}

[TestMethod]
public void DecryptStreamTruncatedCiphertext()
{
const int ChunkLength = 8;
const int EncryptedChunkLength = ChunkLength + 16;

byte[] plaintext = new byte[3 * ChunkLength];
byte[] header;
byte[] ciphertext;

using (MemoryStream encrypted = new MemoryStream())
{
using (EncryptionStream ec =
new EncryptionStream(TestData.BytesTestKey, [], ChunkLength, false, 0, encrypted, true))
{
header = ec.GetHeader();

ec.Write(plaintext, 0, plaintext.Length);
ec.FlushFinalBlock();
}

ciphertext = encrypted.ToArray();
}

using MemoryStream ms = new MemoryStream();

Assert.ThrowsException<DevolutionsCryptoException>(() =>
{
using DecryptionStream dc =
new DecryptionStream(TestData.BytesTestKey, [], header, false, ms, true);

dc.Write(ciphertext, 0, ciphertext.Length - EncryptedChunkLength);
dc.FlushFinalBlock();
});
}
}
}
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