Fork, clone, and npm install. Then npm install -g nodemon.

By the end of this lesson, students should be able to:

• Upload files to AWS S3 from a node application
• Write files from a Buffer to the file-system.
• Create path names with a low chance of duplication
• Store information about uploaded files in MongoDB via Mongoose
• Upload files from a browser to express and store them in the file-system or AWS S3.

• An AWS (Amazon Web Services) account
• Familiarity with express middleware

What are the parts of file upload? What are the issues to guard against?

Why is this important?

We'll go through the steps necessary to allow authenticated uploads without allowing other access to AWS.

From the AWS console open tabs for IAM (Identity and Access Management) and S3 (Simple Storage Service).

In the IAM tab, select Users and then the IAM user you want to use for uploads. Alternatively, you can create and select a new user. We'll need the User ARN (Amazon Resource Name) to grant access to the S3 bucket we'll use for uploads. We'll also need an Access Key (Access Key Id and Secret Access Key) for this IAM User to upload files.

In the S3 tab, create a new bucket for uploads. Open Permissions and click on Add bucket policy. Click on AWS Policy Generator at the bottom of the Bucket Policy Editor modal. This will open the AWS Policy Generator page.

On the AWS Policy Generator page, select S3 Bucket Policy as the type of policy to generate. Copy the User ARN from the IAM user page and paste it into the Principal text box. Select Amazon S3 as the AWS Service. Select PutObject and PutObjectAcl in the actions multi-select. Enter arn:aws:s3:::<bucket_name>/<key_name> into the Amazon Resource Name (ARN) text box. key_name is a directory equivalent, we'll use *. After all that, click the Add Statement button then the Generate Policy button. The Policy JSON Document modal that opens contains the bucket policy we'll use (an example follows). Select and copy the JSON then go back to the S3 tab and paste the JSON into the Bucket Policy Editor and click save.

{
  "Version": "2012-10-17",
  "Id": "Policy1439826519004",
  "Statement": [
    {
      "Sid": "Stmt1439826516658",
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::<AWS Account Id>:user/<IAM User Name>"
      },
      "Action": [
        "s3:PutObjectAcl",
        "s3:PutObject"
      ],
      "Resource": "arn:aws:s3:::<bucket_name>/<key_name>"
    }
  ]
}

With this configuration, we only allow upload access to this the one bucket.

This is one specific and restrictive way of implementing access control. AWS provides many different mechanisms to grant and restrict access.

We'll build a command line script to upload a file to AWS.

We'll use AWS.S3, specifically the upload method, to send files to AWS S3.

Why build a command line uploader?

We'll use the following node modules.

• aws-sdk
• crypto
• dotenv
• file-type
• fs
• mongoose

We'll run the script using npm run upload-aws <file> [comment].

We'll separate out the parts that aren't about a command line script so we can reuse them.

We'll build a command line script to "upload" a file to the file-system.

Why build a command line uploader? What do we have to take care of that AWS handles for us?

We'll use the same node modules but omit aws-sdk.

We'll separate out the parts that aren't about a command line script so we can reuse them.

Fork and clone https://github.com/ga-wdi-boston/jquery-ajax-form-data-upload.

We'll use a form with attribute enctype="multipart/form-data" to allow uploading of one or more files.

We'll use the FormData object with jQuery's $.ajax function to POST data to an echo server, http://httpbin.org. Later we'll use this front end to POST data to express/multer.

We'll use the following express modules in addition to the modules from the file-system code along:

• multer
• body-parser
• cors
• debug
• express
• morgan
• multer

We'll need to add aws-sdk to the modules we're using.