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AWS - S3 Unauthenticated Enum

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S3 Public Buckets

A bucket is considered “public” if any user can list the contents of the bucket, and “private” if the bucket's contents can only be listed or written by certain users.
Companies might have buckets permissions miss-configured giving access either to everything or to everyone authenticated in AWS in any account (so to anyone). Note, that even with such misconfigurations some actions might not be able to be performed as buckets might have their own access control lists (ACLs).
Learn about AWS-S3 misconfiguration here: http://flaws.cloud and http://flaws2.cloud/

Finding AWS Buckets

Different methods to find when a webpage is using AWS to storage some resources:

Enumeration & OSINT:

  • Using wappalyzer browser plugin
  • Using burp (spidering the web) or by manually navigating through the page all resources loaded will be save in the History.
  • Check for resources in domains like:
  • Check for CNAMES as resources.domain.com might have the CNAME bucket.s3.amazonaws.com
  • Check https://buckets.grayhatwarfare.com, a web with already discovered open buckets.
  • The bucket name and the bucket domain name needs to be the same.


You can find buckets by brute-forcing names related to the company you are pentesting:
# Generate a wordlist to create permutations
curl -s https://raw.githubusercontent.com/cujanovic/goaltdns/master/words.txt > /tmp/words-s3.txt.temp
curl -s https://raw.githubusercontent.com/jordanpotti/AWSBucketDump/master/BucketNames.txt >>/tmp/words-s3.txt.temp
cat /tmp/words-s3.txt.temp | sort -u > /tmp/words-s3.txt
# Generate a wordlist based on the domains and subdomains to test
## Write those domains and subdomains in subdomains.txt
cat subdomains.txt > /tmp/words-hosts-s3.txt
cat subdomains.txt | tr "." "-" >> /tmp/words-hosts-s3.txt
cat subdomains.txt | tr "." "\n" | sort -u >> /tmp/words-hosts-s3.txt
# Create permutations based in a list with the domains and subdomains to attack
goaltdns -l /tmp/words-hosts-s3.txt -w /tmp/words-s3.txt -o /tmp/final-words-s3.txt.temp
## The previous tool is specialized increating permutations for subdomains, lets filter that list
### Remove lines ending with "."
cat /tmp/final-words-s3.txt.temp | grep -Ev "\.$" > /tmp/final-words-s3.txt.temp2
### Create list without TLD
cat /tmp/final-words-s3.txt.temp2 | sed -E 's/\.[a-zA-Z0-9]+$//' > /tmp/final-words-s3.txt.temp3
### Create list without dots
cat /tmp/final-words-s3.txt.temp3 | tr -d "." > /tmp/final-words-s3.txt.temp4http://phantom.s3.amazonaws.com/
### Create list without hyphens
cat /tmp/final-words-s3.txt.temp3 | tr "." "-" > /tmp/final-words-s3.txt.temp5
## Generate the final wordlist
cat /tmp/final-words-s3.txt.temp2 /tmp/final-words-s3.txt.temp3 /tmp/final-words-s3.txt.temp4 /tmp/final-words-s3.txt.temp5 | grep -v -- "-\." | awk '{print tolower($0)}' | sort -u > /tmp/final-words-s3.txt
## Call s3scanner
s3scanner --threads 100 scan --buckets-file /tmp/final-words-s3.txt | grep bucket_exists

Loot S3 Buckets

Given S3 open buckets, BucketLoot can automatically search for interesting information.

Find the Region

You can find all the supported regions by AWS in https://docs.aws.amazon.com/general/latest/gr/s3.html


You can get the region of a bucket with a dig and nslookup by doing a DNS request of the discovered IP:
dig flaws.cloud
flaws.cloud. 5 IN A
Non-authoritative answer: name = s3-website-us-west-2.amazonaws.com.
Check that the resolved domain have the word "website". You can access the static website going to: flaws.cloud.s3-website-us-west-2.amazonaws.com or you can access the bucket visiting: flaws.cloud.s3-us-west-2.amazonaws.com

By Trying

If you try to access a bucket, but in the domain name you specify another region (for example the bucket is in bucket.s3.amazonaws.com but you try to access bucket.s3-website-us-west-2.amazonaws.com, then you will be indicated to the correct location:

Enumerating the bucket

To test the openness of the bucket a user can just enter the URL in their web browser. A private bucket will respond with "Access Denied". A public bucket will list the first 1,000 objects that have been stored.
Open to everyone:
You can also check this with the cli:
#Use --no-sign-request for check Everyones permissions
#Use --profile <PROFILE_NAME> to indicate the AWS profile(keys) that youwant to use: Check for "Any Authenticated AWS User" permissions
#--recursive if you want list recursivelyls
#Opcionally you can select the region if you now it
aws s3 ls s3://flaws.cloud/ [--no-sign-request] [--profile <PROFILE_NAME>] [ --recursive] [--region us-west-2]
If the bucket doesn't have a domain name, when trying to enumerate it, only put the bucket name and not the whole AWSs3 domain. Example: s3://<BUCKETNAME>

Public URL template



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