Client-side File Encryption: Backend

server.js

app.post('/file', function(req, res) {

    //We create a write stream which will save the file to gridfs.
    //"gridfs-stream" is great at this.
    var writestream = gfs.createWriteStream({
        filename: req.files.file.name
    });

    //fs.createReadStream() will read the file uploaded to tmp directory and
    //pipe it to the write stream.
    fs.createReadStream(req.files.file.path).pipe(
        writestream.on('close', function(file) {

            //The temporary file is deleted from local filesystem
            fs.unlink(req.files.file.path);

            //and the id sent back to angular so we can build a link to the file
            res.send(file._id.toString())
        }));
});

app.get('/file/:id', function(req, res) {

    //We set up a read stream with the file id
    var readstream = gfs.createReadStream({
        _id: req.params.id
    });

    //Not really needed
    res.set({
        'Content-Type': 'application/octet-stream'
    });

    //This is a helper method which will set "Content-disposition: attachment"
    //so the browser will download the file instead of trying to open it.
    res.attachment();

    //Finally we pipe the stream 
    readstream.pipe(res);
});