block32.js

// server/src/services/aws/s3.js
...
const presignedPostDocument = (keyName, isPublic = false) => {
  const acl = isPublic ? 'public-read' : 'private';
  return new Promise((resolve, reject) => {
    const params = {
      Bucket: s3Bucket,
      Fields: {
        Key: keyName,
      },
      Expires: 300,
      Conditions: [
        ['content-length-range', 0, 5242880],
        ['eq', '$Content-Type', 'application/pdf'],
        { acl },
      ],
    };
    s3.createPresignedPost(params, (err, data) => {
      if (err) {
        reject('Error while creating presigned post', err);
      } else {
        resolve(data);
      }
    });
  });
};
...