Pre-signing Amazon S3 URLs for Both HEAD and GET Verbs: A Guide

Pre-signing Amazon S3 URLs for Both HEAD and GET Verbs: A Guide

As a data scientist or software engineer, you may need to provide temporary access to an Amazon S3 object. You can achieve this using a method known as pre-signing URLs. In this article, we’ll explain how to pre-sign Amazon S3 URLs for both HEAD and GET verbs.

What is a Pre-signed URL?

A pre-signed URL provides secure, temporary access to Amazon S3 objects. It’s a URL for an Amazon S3 resource, appended with security credentials, an expiration time, and any other necessary information. You can use pre-signed URLs when you want to share an object with someone who does not have AWS security credentials or to provide a temporary download/upload link.

How to Pre-sign S3 URLs for HEAD Verb

The HEAD verb retrieves metadata from an object without returning the object itself. This verb is useful if you’re only interested in an object’s metadata. To pre-sign a URL for the HEAD verb, you can use the AWS SDK for Python (Boto3). Here’s how:

import boto3
from botocore.exceptions import NoCredentialsError

def create_presigned_url(bucket_name, object_name, expiration=3600):
    """
    Generate a pre-signed URL for the S3 object
    """
    s3_client = boto3.client('s3')
    try:
        response = s3_client.generate_presigned_url('head_object', Params={'Bucket': bucket_name, 'Key': object_name}, ExpiresIn=expiration)
    except NoCredentialsError:
        print("Credentials not available")
        return None
    return response

How to Pre-sign S3 URLs for GET Verb

The GET verb is used to download an object. Here’s how to generate a pre-signed URL for the GET verb:

def create_presigned_url(bucket_name, object_name, expiration=3600):
    """
    Generate a pre-signed URL for the S3 object
    """
    s3_client = boto3.client('s3')
    try:
        response = s3_client.generate_presigned_url('get_object', Params={'Bucket': bucket_name, 'Key': object_name}, ExpiresIn=expiration)
    except NoCredentialsError:
        print("Credentials not available")
        return None
    return response

In both examples, the generate_presigned_url method of the S3 client object is used. You need to pass the name of the operation (head_object or get_object), the bucket name, and the object key. You can also specify an optional expiration time in seconds.

Conclusion

Pre-signing Amazon S3 URLs is a powerful feature that allows you to securely share your objects with others. Whether you want to retrieve an object’s metadata with the HEAD verb or download it using the GET verb, mastering this technique is a highly valuable skill for any data scientist or software engineer working with AWS.

Remember that while pre-signed URLs are secure, they should still be handled with care, as anyone in possession of the URL has the granted access. Always ensure to set an appropriate expiration time for your URLs.

Stay tuned for more posts on how to leverage AWS services for your data science and software engineering needs!

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