Sandcastle - A Python Script For AWS S3 Bucket Enumeration

Sandcastle – A Python Script For AWS S3 Bucket Enumeration


Inspired by a conversation with Instacart’s @nickelser on HackerOne, I’ve optimised and published Sandcastle – a Python script for AWS S3 bucket enumeration, formerly known as bucketCrawler.
The script takes a target’s name as the stem argument (e.g. shopify) and iterates through a file of bucket name permutations, such as the ones below:


Getting started
Here’s how to get started:

  1. Clone this repo (PyPi distribution temporarily disabled).
  2. Run with a target name and input file (grab an example from this repo)
  3. Matching bucket permutations will be identified, and read permissions tested.
usage: [-h] -t targetStem [-f inputFile]

-h, --help show this help message and exit
-t targetStem, --target targetStem
Select a target stem name (e.g. 'shopify')
-f inputFile, --file inputFile
Select a bucket permutation file (default: bucket-
   ____             __             __  __
/ __/__ ____ ___/ /______ ____ / /_/ /__
_ / _ `/ _ / _ / __/ _ `(_-</ __/ / -_)

S3 bucket enumeration // release v1.2.4 // ysx

[*] Commencing enumeration of 'shopify', reading 138 lines from 'bucket-names.txt'.

[+] Checking potential match: shopify-content --> 403

An error occurred (AccessDenied) when calling the ListObjects operation: Access Denied

Status codes and testing

Status codeDefinitionNotes
404Bucket Not FoundNot a target for analysis (hidden by default)
403Access DeniedPotential target for analysis via the CLI
200Publicly AccessiblePotential target for analysis via the CLI

AWS CLI commands
Here’s a quick reference of some useful AWS CLI commands:

  • List Files: aws s3 ls s3://bucket-name
  • Download Files: aws s3 cp s3://bucket-name/<file> <destination>
  • Upload Files: aws s3 cp/mv test-file.txt s3://bucket-name
  • Remove Files: aws s3 rm s3://bucket-name/test-file.txt

What is S3?
From the Amazon documentation, Working with Amazon S3 Buckets:

Amazon S3 [Simple Storage Service] is cloud storage for the Internet. To upload your data (photos, videos, documents etc.), you first create a bucket in one of the AWS Regions. You can then upload any number of objects to the bucket.

In terms of implementation, buckets and objects are resources, and Amazon S3 provides APIs for you to manage them.

Closing remarks

  • This is my first public security project. Sandcastle is published under the MIT License.
  • Usage acknowlegements:
    • Castle (icon) by Andrew Doane from the Noun Project
    • Nixie One (logo typeface) free by Jovanny Lemonad

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