Sandcastle : A Python Script For AWS S3 Bucket Enumeration

Inspired by a conversation with Instacart’s @nickelser on HackerOne, I’ve optimized 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:

-training
-bucket
-dev
-attachments
-photos
-elasticsearch […]

Getting Started

• Here’s how to get started:
  • Clone this repo (PyPi distribution temporarily disabled).
  • Run sandcastle.py with a target name and input file (grab an example from this repo)
  • Matching bucket permutations will be identified, and read permissions tested.

Usage: sandcastle.py [-h] -t targetStem [-f inputFile]
Arguments:
-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-
names.txt)

>>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

Also Read – MSSQLi-DUET : MSSQL Injection-based Domain User Enumeration Tool

Status Codes & Testing

Status code	Definition	Notes
404	Bucket Not Found	Not a target for analysis (hidden by default)
403	Access Denied	Potential target for analysis via the CLI
200	Publicly Accessible	Potential 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 acknowledgements:
  • Castle (icon) by Andrew Doane from the Noun Project
  • Nixie One (logo typeface) free by Jovanny Lemonad