jstedfast/MailKit · error · ArgumentOutOfRangeException

inputCount

Error message

inputCount

What it means

TransformBlock throws ArgumentOutOfRangeException named "inputCount" when inputCount is negative or when inputOffset + inputCount exceeds inputBuffer.Length (check: inputOffset > inputBuffer.Length - inputCount). It enforces that the block to hash lies entirely inside the input array, consistent with ICryptoTransform semantics.

Solutions

1. Clamp the final chunk: count = Math.Min(blockSize, inputBuffer.Length - inputOffset).
2. Verify count is bytes actually available: require count >= 0 && inputOffset <= inputBuffer.Length - count.
3. Fix length sources (use GetByteCount for encoded text, not string Length).
4. Validate external counts upstream before the transform loop.

Example fix

// before
transform.TransformBlock(buf, offset, blockSize, null, 0); // final short chunk overruns
// after
int count = Math.Min(blockSize, buf.Length - offset);
if (count > 0) transform.TransformBlock(buf, offset, count, null, 0);

if (inputCount < 0 || inputOffset > inputBuffer.Length - inputCount)
    throw new ArgumentOutOfRangeException(nameof(inputCount));

static bool IsValidCount(byte[] buf, int offset, int count) => count >= 0 && offset <= buf.Length - count;

try { transform.TransformBlock(buf, offset, count, null, 0); }
catch (ArgumentOutOfRangeException ex) when (ex.ParamName == "inputCount") { log.LogError(ex, "count {Count} at offset {Offset} exceeds len {Len}", count, offset, buf.Length); throw; }

When it happens

Trigger: TransformBlock(buf, off, -1, null, 0), or TransformBlock(buf, off, len, null, 0) where off + len > buf.Length — e.g. passing full length while also passing a non-zero offset, or a byte-count/char-count mixup.

Common situations: Last-chunk logic computing count as remaining + blockSize; passing Encoding string lengths (chars) instead of byte counts; reusing a constant block size for the final short chunk.

Related errors

• inputOffset
• outputOffset
• inputBuffer
• offset
• count

AI-assisted analysis of jstedfast/MailKit@9d3859a785 (2026-09-15). Data as JSON: /api/errors/7ae330c80334d674. Report an issue: GitHub.

Appendix: source

Thrown at MailKit/Security/Ntlm/MD4.cs:348

					HashCore (buffer, 0, nread);
			} while (nread > 0);

			hashValue = HashFinal ();
			Initialize ();

			return hashValue;
		}

		public int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
		{
			if (inputBuffer == null)
				throw new ArgumentNullException (nameof (inputBuffer));

			if (inputOffset < 0 || inputOffset > inputBuffer.Length)
				throw new ArgumentOutOfRangeException (nameof (inputOffset));

			if (inputCount < 0 || inputOffset > inputBuffer.Length - inputCount)
				throw new ArgumentOutOfRangeException (nameof (inputCount));

			if (outputBuffer != null) {
				if (outputOffset < 0 || outputOffset > outputBuffer.Length - inputCount)
					throw new ArgumentOutOfRangeException (nameof (outputOffset));
			}

			HashCore (inputBuffer, inputOffset, inputCount);

			if (outputBuffer != null)
				Buffer.BlockCopy (inputBuffer, inputOffset, outputBuffer, outputOffset, inputCount);

			return inputCount;
		}

		public byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
		{
			if (inputCount < 0)
				throw new ArgumentOutOfRangeException (nameof (inputCount));

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