peass-ng/PEASS-ng · error · DataLengthException

Output buffer is too short to hold output

Error message

Output buffer is too short to hold output

What it means

Thrown by SkeinEngine's DoFinal when the caller-supplied output buffer is too small: outOff plus the configured output size in bytes exceeds outBytes.Length, so finishing the hash would write past the end of the buffer.

Source

Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/BouncyCastle/crypto/digests/SkeinEngine.cs:744

        public void Update(byte inByte)
        {
            singleByte[0] = inByte;
            Update(singleByte, 0, 1);
        }

        public void Update(byte[] inBytes, int inOff, int len)
        {
            CheckInitialised();
            ubi.Update(inBytes, inOff, len, chain);
        }

        public int DoFinal(byte[] outBytes, int outOff)
        {
            CheckInitialised();
            if (outBytes.Length < (outOff + outputSizeBytes))
            {
                throw new DataLengthException("Output buffer is too short to hold output");
            }

            // Finalise message block
            UbiFinal();

            // Process additional post-message parameters
            if (postMessageParameters != null)
            {
                for (int i = 0; i < postMessageParameters.Length; i++)
                {
                    Parameter param = postMessageParameters[i];
                    UbiComplete(param.Type, param.Value);
                }
            }

            // Perform the output transform
            int blockSize = BlockSize;
            int blocksRequired = ((outputSizeBytes + blockSize - 1) / blockSize);

View on GitHub (pinned to 53fb989abc)

Solutions

1. Allocate outBytes with at least outOff + engine output size bytes (GetDigestSize())
2. Reduce outOff or use a fresh buffer sized for the configured output
3. Lower the configured output size in the SkeinEngine constructor/SkeinParameters to match your buffer

Example fix

// before
byte[] outBytes = new byte[32];
engine.DoFinal(outBytes, 0);
// after
byte[] outBytes = new byte[engine.GetDigestSize()];
engine.DoFinal(outBytes, 0);

byte[] outBytes = new byte[engine.GetDigestSize() + outOff];
engine.DoFinal(outBytes, outOff);

static bool CanHoldDigest(byte[] buf, int off, int digestSize) => buf != null && buf.Length >= off + digestSize;

try { engine.DoFinal(outBytes, outOff); } catch (DataLengthException ex) { /* grow buffer and retry */ }

When it happens

Trigger: Calling DoFinal(outBytes, outOff) where outBytes is shorter than outOff plus the digest size configured for the engine (e.g. a 32-byte buffer for a 64-byte Skein-512 output, or a large outOff).

Common situations: Assuming a SHA-256-sized 32-byte buffer when the Skein state was configured for a larger output size; off-by-one or reused outOff in incremental hashing loops.

Related errors

• msg
• Keys > 32 are not supported
• Invalid digest length (required: 1 - 32)
• Salt length must be exactly 8 bytes
• Personalization length must be exactly 8 bytes

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/58cd333400260336. Report an issue: GitHub.