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14. Amazon S3: Buckets, Objects, Policies and Presigned URLs

14.5 Versioning and Lifecycle Rules

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Versioning on kela ki pratyek overwrite aani delete nantar juna version surakshit rahto. Chukun delete zala tari file parat milte – aani ransomware ne overwrite kela tari.

aws s3api put-bucket-versioning --bucket ravindra-demo-files-pune \
  --versioning-configuration Status=Enabled
echo "v1" > note.txt && aws s3 cp note.txt s3://ravindra-demo-files-pune/note.txt
echo "v2" > note.txt && aws s3 cp note.txt s3://ravindra-demo-files-pune/note.txt
aws s3api list-object-versions --bucket ravindra-demo-files-pune --prefix note.txt
aws s3 rm s3://ravindra-demo-files-pune/note.txt        # adds a "delete marker" only
# restore: delete the delete marker (use the VersionId shown by list-object-versions)
aws s3api delete-object --bucket ravindra-demo-files-pune --key note.txt --version-id <MarkerVersionId>
Action with versioning ON Result
Upload same key again New version; old version kept
Delete without version ID A delete marker hides the object; data still there
Delete a specific version ID That version is gone permanently
Suspend versioning New uploads get no version; old versions remain

Old versions cost storage, so add a lifecycle rule: for example, move objects under logs/ to Standard-IA after 30 days, and permanently delete non-current versions after 60 days (console: Management → Create lifecycle rule).

{ "Rules": [ {
    "ID": "clean-old-versions", "Status": "Enabled", "Filter": { "Prefix": "" },
    "NoncurrentVersionExpiration": { "NoncurrentDays": 60 },
    "AbortIncompleteMultipartUpload": { "DaysAfterInitiation": 7 }
} ] }

aws s3api put-bucket-lifecycle-configuration --bucket ravindra-demo-files-pune \
  --lifecycle-configuration file://lifecycle.json

Why this matters for security

Versioning protects integrity (अखंडता) and availability (उपलब्धता): an attacker or a buggy script that overwrites or deletes files cannot destroy the older versions without also having s3:DeleteObjectVersion. For critical backups, companies add MFA Delete or S3 Object Lock so even an administrator cannot erase them quickly.

Ravindra Bagale's Tip

After turning versioning on, students run aws s3 rm and then ask "the file is gone, so versioning doesn't work?" – but it's only hidden by a delete marker. Run list-object-versions and you'll see all the versions there. And don't forget a lifecycle rule – otherwise old versions quietly keep increasing your storage.

Practice task

Enable versioning, upload three versions of note.txt, delete it, then restore it by removing the delete marker. Add a lifecycle rule that expires non-current versions after 30 days.

Extended teaching notes

Why this lesson matters

Use this lesson to strengthen systems you own: understand the risk, practise safely in a lab, then write and apply the fix.

Apply the fix across stacks

Same class of bug, same idea in every language.

Java / Spring Boot

Parameterise queries, encode output, CSRF tokens, limited Actuator, dependency scanning.

ASP.NET Core

EF Core / parameterised SQL, Razor encoding, HTTPS, Data Protection.

Node.js / Express

helmet, parameterised SQL, npm audit, avoid eval and shell concat.

Python / Django / Flask / FastAPI

ORM, autoescape, pip-audit, Bandit; never shell=True with user input.

PHP / Laravel

PDO/Eloquent, Blade escaping, composer audit.

Go / Ruby

database/sql placeholders / ActiveRecord; html/template / ERB escaping; govulncheck / Brakeman.

nginx / Apache / Tomcat

Hide versions, TLS, security headers, least-open ports.

MySQL / PostgreSQL / MongoDB / Redis

Private networks, auth on, least-privilege users, no 0.0.0.0/0.

AWS / Azure / GCP

Roles not long-lived keys, private data stores, cloud audit logs on.

Mini case study

Suppose we are on a purple-team exercise for an Indian mid-size company (sample data). Red notes a technique from this lesson against a lab clone. Blue must show the control that stops it, the log that would have fired, and the ticket that hardens production. That is the standard this course trains you for.

Defender's worksheet (do this today)

  1. Write the lesson title, date and the exact lab target you are allowed to use.
  2. List three owned systems (VMs, apps, or cloud accounts) where this lesson applies.
  3. Run one safe check from the lesson on a lab system only. Paste the command and output.
  4. Write a two-sentence fix you would give a teammate.
  5. Name one related public advisory (CERT-In, CISA, NVD, or a vendor bulletin) with its date.

Indian workplace (sample data)

Suppose we are a junior analyst at Infosys, TCS, Wipro or a fintech SOC in Bengaluru/Pune. Turn this lesson into one checklist item with an owner, a due date and a place to store evidence (ticket + screenshot).

Global practice

Compare your notes with OWASP, CIS Benchmarks, NIST CSF/IR guidance or a cloud Well-Architected security question. Write five lines on what overlaps.

Everyday analogy

Explain the risk and the fix to a family member without jargon. If they can repeat the warning, you understand it well enough to teach juniors.

Key terms

  • Control: a safeguard (patch, config, process, detection).
  • Finding: a weakness backed by evidence.
  • Remediation: the fix plus how you verified it.
  • Scope: systems you have written permission to touch.
  • Least privilege: only the access the task needs.
  • Defence in depth: several layers so one failure does not end the story.

Common mistakes

  • Skipping written permission "just for a quick scan".
  • Practising on hostel, office or public targets without authorisation.
  • Collecting tool output without writing the fix.
  • Copying attack steps onto production to "verify". Defenders verify with versions, configs and patches.
  • Publishing screenshots that contain secrets, cookies or internal hostnames.

Recap

  • Evidence, fix, owner, date.
  • Own lab only.
  • Fix > spectacle.