title: Amazon S3 bucket policy for anonymously uploading photos to a bucket
body: <p>I am planning on using Amazon S3 to let users upload photos from an iPhone and then let them be publicly viewable.</p>
  
  <p>I am having some trouble understanding how to set up these security constraints in the bucket policy:</p>
  
  <ul>
  <li>Everyone can read every file.</li>
  <li>Everyone can upload a <em>new</em> file that is maximum 256K large.</li>
  <li>No one can delete any file.</li>
  <li>No one can modify any file.</li>
  </ul>