gchq/CyberChef · error · OperationError

Invalid file type.

Error message

Invalid file type.

What it means

Thrown at the top of RotateImage.run() when isImage(input) returns falsy, meaning the input ArrayBuffer's magic bytes are not a recognised image type. This guard runs before Jimp.read() so non-image input is rejected cheaply.

Source

Thrown at src/core/operations/RotateImage.mjs:50

        this.args = [
            {
                name: "Rotation amount (degrees)",
                type: "number",
                value: 90,
            },
        ];
    }

    /**
     * @param {ArrayBuffer} input
     * @param {Object[]} args
     * @returns {byteArray}
     */
    async run(input, args) {
        const [degrees] = args;

        if (!isImage(input)) {
            throw new OperationError("Invalid file type.");
        }

        let image;
        try {
            image = await Jimp.read(input);
        } catch (err) {
            throw new OperationError(`Error loading image. (${err})`);
        }
        try {
            if (isWorkerEnvironment())
                self.sendStatusMessage("Rotating image...");
            image.rotate(degrees);

            let imageBuffer;
            if (image.mime === "image/gif") {
                imageBuffer = await image.getBuffer(JimpMime.png);
            } else {
                imageBuffer = await image.getBuffer(image.mime);

View on GitHub (pinned to 4290ea7539)

Solutions

1. Confirm the input is a supported image (PNG, JPEG, GIF, BMP, TIFF, WebP) using a hex viewer or the 'Detect File Type' operation.
2. Insert a 'Render Image' or 'Detect File Type' step before Rotate Image to verify the buffer.
3. Convert the source to PNG/JPEG before rotating if it is an unsupported but valid image format.

import { isImage } from "src/core/lib/FileType.mjs";
function ensureImage(buf) {
  const arr = buf instanceof Uint8Array ? buf : new Uint8Array(buf);
  if (!isImage(arr)) throw new TypeError("Input is not a recognised image type");
  return buf;
}

function isImageInput(buf) {
  return buf instanceof ArrayBuffer && isImage(new Uint8Array(buf)) !== null;
}

When it happens

Trigger: Passing a text, archive, audio, or other non-image ArrayBuffer to Rotate Image; passing an image format FileType detection does not support.

Common situations: Feeding the wrong operation output into Rotate Image; a recipe where an upstream decode fails silently leaving non-image bytes; obscure image formats not in the FileType signature table.

Related errors

• Invalid file type.
• Invalid file type.
• Invalid file type.
• Invalid file type.
• Unsupported file type (supported: jpg,png,pbm,bmp) or no fil

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/5e2ee5b983d4eb52. Report an issue: GitHub.