02. Git DAG (Directed Acyclic Graph) & Plumbing Commands (cat-file, hash-object, write-tree) • Git, System Design & Web Security (OWASP Top 10) • Rishabh Ki Kaksha

Git, System Design & Web Security (OWASP Top 10) › 02. Git DAG (Directed Acyclic Graph) & Plumbing Commands (cat-file, hash-object, write-tree)

45 mins

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Course Syllabus

Module 1: Git Internals, Plumbing Commands & DAG Graph Architecture

01. Git Internals: Blobs, Trees, Commits & Annotated Tags (The .git Directory Anatomy) 02. Git DAG (Directed Acyclic Graph) & Plumbing Commands (cat-file, hash-object, write-tree) 03. Git Three Trees Architecture: Working Directory, Staging Index & HEAD

Part 1: Git Mastery, Security Defense & Caching

Module 2: Advanced Branching Strategies & Disaster Recovery

04. Advanced Rebasing: Interactive Rebase (squash, edit, fixup) vs Merge 05. Git Disaster Recovery: git reflog, Cherry-Pick & Recovering Deleted Commits/Branches 06. Enterprise Branching: Trunk-Based Development vs GitFlow vs Feature Flag Architecture

Module 3: Web Application Security: OWASP Top 10 Defenses

07. OWASP #1 & #3: SQL Injection (SQLi) & Server-Side Request Forgery (SSRF) Hardening 08. Cross-Site Scripting (XSS): Stored, Reflected, DOM-based & Content Security Policy (CSP) 09. CSRF vs Cross-Origin Traps: SameSite Cookies, Anti-CSRF Tokens & CORS Preflight Rules 10. Broken Object-Level Authorization (BOLA/IDOR) & Role-Based Access Control (RBAC/ABAC)

Module 4: Cryptography, PKI, SSL/TLS & Mutual Auth (mTLS)

11. Asymmetric Cryptography (RSA vs ECC) & Digital Signatures with GPG Keys 12. Public Key Infrastructure (PKI), TLS 1.3 Handshake & Let's Encrypt Automation 13. Mutual TLS (mTLS) for Zero-Trust Service-to-Service Communication

Module 5: DevSecOps, Secret Scanning & Zero-Trust Security Architecture

14. Automated Secret Scanning (Gitleaks, Trufflehog) & Git Pre-Commit Hooks 15. Software Supply Chain Security: Dependabot, SBOM (Software Bill of Materials) & Signed Commits 16. Enterprise Zero-Trust Architecture: Cloud IAM, Bastion Hosts & WireGuard VPN Networks

Interactive Lesson Studio

# 02. Git DAG (Directed Acyclic Graph) & Plumbing Commands (cat-file, hash-object, write-tree)

> Git & Web Security Notes by Rishabh - Topic 02

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### 1. Porcelain vs Plumbing Commands 🚰

*   **Porcelain Commands (User-Facing):** High-level friendly commands (`git add`, `git commit`, `git checkout`, `git pull`).
*   **Plumbing Commands (Low-Level Core):** Low-level commands jo Git internal engine manipulate karte hain (`git hash-object`, `git cat-file`, `git write-tree`, `git commit-tree`).

---

### 2. Building a Real Git Commit from Scratch Using Only Plumbing! 🔬

```bash
# Step 1: Create a Blob from string and write to .git/objects/
echo "console.log('Hello Big Tech');" | git hash-object -w --stdin
# Output: 526279f041b38f... (SHA-1)

# Step 2: Inspect object type and content with cat-file:
git cat-file -t 526279f041b38f   # Outputs: blob
git cat-file -p 526279f041b38f   # Outputs: console.log('Hello Big Tech');

# Step 3: Add file to index (Staging Area):
git update-index --add --cacheinfo 100644 526279f041b38f app.js

# Step 4: Write Staging Index to a Tree Object:
git write-tree
# Output: 8b2c4e1... (Tree SHA-1)

# Step 5: Create an Immutable Commit Object pointing to Tree:
git commit-tree 8b2c4e1 -m "Plumbing commit crafted by Rishabh"
# Output: 3f91a0c... (Commit SHA-1)

# Step 6: Update main branch pointer to new commit:
git update-ref refs/heads/main 3f91a0c
```

---

### 3. Git History as a DAG (Directed Acyclic Graph) 🌐

Commits DAG nodes hote hain jisme child commit apne parent commit ko point karta hai:
$$\text{Commit C} \longrightarrow \text{Commit B} \longrightarrow \text{Commit A (Root)}$$
*   Acyclic ka matlab: Pointers strictly backward point karte hain, kabhi cycle nahi ban sakti.

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### 4. Master Comparison Matrix

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### 5. Interview Ke 3 Sawal Is Topic Se

1. **`git cat-file -p` command me `-p` flag kya karta hai?** -> Pretty-print! Object ke type ke anusaar readable format me decode karta hai (Blobs ke liye text, Trees ke liye permissions/SHA table, Commits ke liye author/tree metadata).
2. **Git SHA-1 hash calculate karte waqt header kya include karta hai?** -> `"<type> <size>\0<content>"` (e.g. `"blob 14\0Hello World\n"`).
3. **Merge commit aur Normal commit me DAG level par kya difference hota hai?** -> Normal commit ka 1 parent commit hota hai; Merge commit ke **2 (ya zyada in Octopus merge) parent commits** hote hain!

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**Next Topic:** 03. Git Three Trees Architecture: Working Directory, Staging Index & HEAD

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Rishabh Gehlot

PHP 8+ & Laravel 11 Master Track