Upload file to s3 with MD5 hash-check

s3-upload-with-md5.js

const crypt = require('crypto');
const fs = require('fs').promises;

const aws = require('aws-sdk');

async function uploadFileToS3WithMd5Hash(bucket, filename, s3Key = null) {
  const data = await fs.readFile(filename);
  const md5Base64 = crypt.createHash("md5").update(data).digest('base64');

  if (!s3Key) {
    s3Key = filename;
  }

  /** Should you want to get the MD5 in hex format: */
  // const md5Hex = Buffer.from(md5Base64, 'base64').toString('hex');

  return new Promise((res, rej) => {
    const s3 = new aws.S3();
    s3.putObject({
      Bucket: bucket,
      Key: s3Key,
      Body: data,
      ContentMD5: md5Base64,
    }, (err, resp) => err ? rej(err) : res(resp));
  })
}

uploadFileToS3WithMd5Hash('your-own-bucket', 'file.txt')
  .then(console.log)
  .catch(console.error);

A successful response will be something like

{
  ETag: '"535aa38d175bdf635b64cd3fa0f43fc6"',
  ...
}

Where ETag is the md5 hash in hex (with quotes around 🤷)