AES 256 GCM encryption decryption in nodejs - encryption

Question

I am implementing a basic encryption/decryption set of functions in nodejs and I keep getting the following error in the decryption part:
Error: Unsupported state or unable to authenticate data
This is my code so far:
import crypto from 'crypto'
import logger from './logger'
const ALGORITHM = 'aes-256-gcm'
export const encrypt = (keyBuffer, dataBuffer, aadBuffer) => {
// iv stands for "initialization vector"
const iv = Buffer.from(crypto.randomBytes(12), 'utf8')
logger.debug('iv: ', iv)
const encryptor = crypto.createCipheriv(ALGORITHM, keyBuffer, iv)
logger.debug('encryptor: ', encryptor)
logger.debug('dataBuffer: ', dataBuffer)
return Buffer.concat([iv, encryptor.update(dataBuffer, 'utf8'), encryptor.final()])
}
export const decrypt = (keyBuffer, dataBuffer, aadBuffer) => {
const iv = dataBuffer.slice(0, 96)
const decryptor = crypto.createDecipheriv(ALGORITHM, keyBuffer, iv)
return Buffer.concat([decryptor.update(dataBuffer.slice(96), 'utf8'), decryptor.final()])
}
My error happens in the last line of the decrypt function. I am storing the iv as part of the dataBuffer.
Thanks in advance!

Answer 1

I realized I had made a couple of mistakes with the original code that I posted, one of them as #TheGreatContini remarked was the size of the slicing which was being done in bits instead of bytes as it should be. Still, the biggest piece that I was missing was the authTag which always should be included in the decipher function setup.
Here is my working code for anybody interested for future references:
import crypto from 'crypto'
import logger from './logger'
const ALGORITHM = 'aes-256-gcm'
export const encrypt = (keyBuffer, dataBuffer, aadBuffer) => {
// iv stands for "initialization vector"
const iv = crypto.randomBytes(12)
const cipher = crypto.createCipheriv(ALGORITHM, keyBuffer, iv)
const encryptedBuffer = Buffer.concat([cipher.update(dataBuffer), cipher.final()])
const authTag = cipher.getAuthTag()
let bufferLength = Buffer.alloc(1)
bufferLength.writeUInt8(iv.length, 0)
return Buffer.concat([bufferLength, iv, authTag, encryptedBuffer])
}
export const decrypt = (keyBuffer, dataBuffer, aadBuffer) => {
const ivSize = dataBuffer.readUInt8(0)
const iv = dataBuffer.slice(1, ivSize + 1)
// The authTag is by default 16 bytes in AES-GCM
const authTag = dataBuffer.slice(ivSize + 1, ivSize + 17)
const decipher = crypto.createDecipheriv(ALGORITHM, keyBuffer, iv)
decipher.setAuthTag(authTag)
return Buffer.concat([decipher.update(dataBuffer.slice(ivSize + 17)), decipher.final()])
}