A Guide to Access AWS S3 Objects Using Pre-Signed URL

Introduction

AWS S3 (Simple Storage Service) is an Amazon Web Service (AWS) storage service. AWS S3 offers high scalability, security, data availability, and performance. We can store any data in an AWS S3 bucket. Also, we can organize the data by creating a folder(s) in a bucket. This blog will teach us the best way to access AWS S3 Objects.

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Why is a Pre-Signed URL required?

AWS S3 is the most used storage service to store files. Most developers are publicly making the AWS S3 bucket available, but this approach is not recommended for security reasons.

AWS S3 Pre-Signed is the most recommended way to share the files of the Amazon S3 bucket. Using AWS S3 Pre-Signed URL, you can set permissions, expiration time, and operation on AWS S3 Objects (Files).

Permissions: AWS S3 Pre-Signed URL has the permission of the AWS IAM User or AWS Services. Pre-Signed URLs get all the access that the IAM user or AWS Services has on a specific AWS S3 bucket.
Expiration Time: We can define the expiration time of the AWS S3 Pre-Signed URL while creating the URL. Once the expiration time passes, the Pre-Signed URL will automatically be expired.
Resources: You can specify a file or bucket name while creating the Pre-Signed URL.

Steps to create a Pre-Signed URL using AWS SDK

Step 1: Create an IAM user.

Search IAM services on the AWS console and select IAM service
Select Users options in Access Management

step1

Select Add Users

step1b

Enter your Username and select Programmatic Access as an access type. You can give any username but ensure you give programmatic access to that user.

step1c

On the next step, select Attach Existing policies directly and click on Create a policy

step1d

On the Create Policy screen. Select Amazon S3 as a service, Get Object as an action, and Amazon S3 bucket as a specific resource.

step1e

Keep everything else as default, give the policy name, and click on Create a policy

step1f

Select the policy for the IAM user you created in the previous steps. And at the end, you will receive that user’s access key, the secret key.

Note: Download that access key and secret key because this is the last time these credentials will be available to see or download.

step1g

Step 2: Generate a Pre-Signed URL using AWS-SDK

Install AWS SDK in your project to generate a pre-signed URL

npm install aws-sdk

1	npm install aws-sdk

Import downloaded SDK into your project

var AWS = require(‘aws-sdk’);

1	var AWS = require(‘aws-sdk’);

Add the following code snippet to get a pre-signed URL

In the following code snippet, initialize the AWS by passing the access key, secret key, and region. After that, initialize the Amazon S3 object. At last, call the getSignedUrl function of the Amazon S3 object by passing the bucket name, file name, and expiry time.

var AWS = require(‘aws-sdk’);

var credentials = {
  accessKeyId: xxxxx,
  secretAccessKey: xxxxx,
};

AWS.config.update({
region: 'ap-south-1',
credentials: credentials
});

var s3 = new AWS.S3(); 

var presignedURL = s3.getSignedUrl(
  ‘getObject’, 
  { 
    Bucket: ‘mayyur’, 
    Key: ‘sampleImage.jpg’, 
    Expires: 3600 
  }
);

var AWS = require(‘aws-sdk’);

var credentials = {

accessKeyId: xxxxx,

secretAccessKey: xxxxx,

};

AWS.config.update({

region: 'ap-south-1',

credentials: credentials

});

var s3 = new AWS.S3();

var presignedURL = s3.getSignedUrl(

‘getObject’,

{

Bucket: ‘mayyur’,

Key: ‘sampleImage.jpg’,

Expires: 3600

}

);

It will provide a single URL accessible for a specified period, determined by the expiry time you pass. In our case, it will be valid for 3600 seconds. You can use this pre-signed URL to access the file, whatever you passed as a key.

Conclusion

By generating a pre-signed URL, you can temporarily access a file without making it publicly available, offering a secure and controlled method for granting time-limited file access. A pre-signed URL involves appending authentication information to the URL, such as expiration time, access permissions, and other pertinent details. This enables individuals possessing the pre-signed URL to access the file within the specified timeframe without compromising its security or exposing it to the public. This approach is valuable for sharing confidential or sensitive files with specifically authorized individuals or within a restricted timeframe, ensuring that only authorized parties can access the file during the designated period.

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