Error decrypting AES-encrypted text from file through stdin and pipe to stdout in Node.js

Let’s say we have a file named foobar.enc and a script called decrypt-from-stdin-to-stdout.js. the file foobar.enc contains an AES-encrypted text. This text is unencrypted as follows: “foobar”.

The script is being called in this way:

cat foobar.enc | node decrypt-from-stdin-to-stdout.js

Expected output on console should be: “foobar”
But it is “fooba” instead.

Im am working with Windows 10 Professional and Cygwin and Node v20.9.0. Another test with same input file and script on a native Debian system yields the same strange result.

So what is the problem with the script?
This is the script:

const crypto = require('crypto');
const zlib = require('zlib');


function createCipherKeyBuffer(passwordStr) {
  return crypto.createHash('sha256').update(passwordStr).digest();
}


const stdoutStream = process.stdout;
const stdinStream = process.stdin;

let decipherStream;
let initVectBufferCreated = false;


stdinStream.on('data', inputBuffer => {
  if (inputBuffer.length >= 16 && !initVectBufferCreated) {
    const initVectBuffer = inputBuffer.subarray(0, 16);
    initVectBufferCreated = true;

    const unzipStream = zlib.createUnzip();

    const cipherKeyBuffer = createCipherKeyBuffer('power237');
    decipherStream = crypto.createDecipheriv('aes256', cipherKeyBuffer, initVectBuffer);

    /*stdinStream.on('end', () => {
      console.error('stdinStream on end');
    });*/

    decipherStream.write(inputBuffer.subarray(16, inputBuffer.length));
    decipherStream
      .pipe(unzipStream)
      .pipe(stdoutStream);

  } else if (inputBuffer.length < 16) {
    console.error('input too small');
    process.exit(1);

  } else {
    decipherStream.write(inputBuffer);
  }
});

Some hints:

I know using passwords in source code is a bad habit. But this code is not for production purposes but only for test. I would just like to understand the main problem.

When I use a larger text like “foobarbazboz”, everything is working fine.
The file foobarbazboz.enc contains the encrypted text.

Calling like:

cat foobarbazboz.enc | node decrypt-from-stdin-to-stdout.js

This outputs (as expected):

“foobarbazboz”

This is the Base64-encoded data for the file foobar.enc:

9BoTOZenA+Ynw0m9/Qzqij9Wzw/VkkuVGXR/jm2+YneeQ08L75ylM6gk+EmhwYJE

And this is the Base64-encoded data for the file foobarbazboz.enc:

zKTsPq7wvdW7dxSj/tNTtC9R7sAvPhrBsgbFDcvSE7CgvGY7DWyBsDtroOh1gOVwUhCv3TbBCb8Ar+UU3DeDAw==

Since the both input files contains binary (encrypted) data and because I want to avoid external resources, I have decided to encode them with Base64 and print them here.
I am sorry for that circumstance. So please first decode the strings and write them to the test files mentioned above.

You can decode them like as follows:

echo "9BoTOZenA+Ynw0m9/Qzqij9Wzw/VkkuVGXR/jm2+YneeQ08L75ylM6gk+EmhwYJE" | base64 -d > foobar.enc

echo "zKTsPq7wvdW7dxSj/tNTtC9R7sAvPhrBsgbFDcvSE7CgvGY7DWyBsDtroOh1gOVwUhCv3TbBCb8Ar+UU3DeDAw==" | base64 -d > foobarbazboz.enc