Sanity Check

Challenge Information

• Challenge Name: Sanity Check (Challenge 2)
• Category: General / Document Analysis
• Source File: Rulebook INSTRUO'14.pdf
• Flag: EOF{h3r3_w3_90_4941n}
• Difficulty: Trivial (Mandatory Challenge)

Solution Methodology

Phase 1: Understanding the Requirement

Key Points:

• Flag is explicitly provided in the rulebook PDF
• This is a mandatory "sanity check" to ensure participants read the rules
• Simple task: find and submit the flag
• No complex techniques required - just document reading

Phase 2: Locate the PDF File

cd /home/uttam/Downloads
ls -lh "Rulebook INSTRUO'14.pdf"

Confirmation: PDF file exists and is accessible

Phase 3: Extract and Search for Flag

pdftotext "Rulebook INSTRUO'14.pdf" - | grep -i "EOF{" -A 2 -B 2

Command Breakdown:

• pdftotext - Converts PDF to plain text
• - - Output to stdout (instead of file)
• grep -i "EOF{" - Case-insensitive search for flag format
• -A 2 -B 2 - Show 2 lines After and Before match for context

Output:

Flag Format: EOF{text}

Example: EOF{h3r3_w3_90_4941n}

This is the sanity check flag...

Phase 4: Verify It's the Sanity Check Flag

pdftotext "Rulebook INSTRUO'14.pdf" - | grep -i "sanity\|h3r3_w3_90" -A 3 -B 3

Output:

Rule #5: Flag Format and Submission

All flags in this CTF will follow the format EOF{text}.
The sanity check flag for this competition is: EOF{h3r3_w3_90_4941n}

This flag must be submitted to participate in the CTF.
Failure to submit this flag will result in disqualification.

Phase 5: Flag Analysis (Leetspeak Decoding)

echo "EOF{h3r3_w3_90_4941n}"

Flag Breakdown:

Leetspeak	Letter	Word
h3r3	here	here
w3	we	we
90	go	go
4941n	again	again

Complete Message: "Here we go again"

Alternative Solution Methods

Method 1: GUI PDF Reader

1. Open Rulebook INSTRUO'14.pdf in any PDF viewer
2. Use Find function (Ctrl+F / Cmd+F)
3. Search for "sanity" or "EOF{"
4. Copy the flag from Rule #5
5. Submit: EOF{h3r3_w3_90_4941n}

Method 2: Full Text Extraction

# Extract entire PDF to text file
pdftotext "Rulebook INSTRUO'14.pdf" rulebook.txt

# Search for flag
grep "EOF{" rulebook.txt

# Read context around flag
grep "sanity" rulebook.txt -A 5 -B 5

Method 3: Python Script

#!/usr/bin/env python3
import PyPDF2
import re

with open("Rulebook INSTRUO'14.pdf", 'rb') as file:
    pdf_reader = PyPDF2.PdfReader(file)
    for page in pdf_reader.pages:
        text = page.extract_text()
        if "EOF{" in text:
            # Extract and print flag
            flags = re.findall(r'EOF\{[^}]+\}', text)
            for flag in flags:
                print(flag)

Tools Used

Tool	Purpose
pdftotext	PDF to text converter (poppler-utils)
grep	Pattern matching and text search
PDF Reader	Adobe Reader, Evince, Okular, or online tools
Python PyPDF2	Alternative programmatic PDF reading

Installation (if needed)

# Ubuntu/Debian
sudo apt-get install poppler-utils

# Mac (Homebrew)
brew install poppler

# Fedora/RHEL
sudo dnf install poppler-utils

# Verify
pdftotext -v

Key Insights

Why This Challenge Exists

• Rule enforcement - Ensures participants read the rulebook
• Participant verification - Confirms active participation
• Format introduction - Teaches the EOF{} flag format
• Barrier to entry - Filters out non-serious participants
• Disqualification mechanism - Mandatory completion requirement

Common Mistakes to Avoid

❌ Mistake	✅ Solution
Skipping the challenge	ALWAYS submit - it's mandatory!
Not reading rulebook	Read thoroughly - critical info is there
Overthinking	It's plainly stated - just find and copy
Wrong format	Include full format: EOF{h3r3_w3_90_4941n}
Typos from manual typing	Copy-paste as instructed