--- name: john-the-ripper-b56f94b351ad description: >- Crack password hashes offline with John the Ripper. Use when a user asks to identify an unknown hash format, recover a forgotten password from a local database or ZIP file, run a CTF hash challenge, or audit the strength of hashes from a system they own. license: Apache-2.0 compatibility: 'John the Ripper 1.9+, Jumbo community build recommended' metadata: author: terminal-skills version: 1.0.0 category: devops repository: https://github.com/openwall/john tags: "john-the-ripper, password-cracking, hash-cracking, ctf, penetration-testing" --- # John the Ripper ## Overview John the Ripper (JtR) is the classic offline password cracker. It identifies hash formats, runs dictionary, incremental (brute-force), and rule-based attacks, and ships *2john helpers that convert common file formats (ZIP, PDF, SSH keys, KeePass, LUKS) into crackable hashes. The community "Jumbo" fork supports hundreds of formats. JtR is CPU-oriented — use hashcat for GPU work on fast hashes. ## Instructions ### Step 1: Identify the Hash Format ```bash # Let JtR guess echo '$6$saltsalt$...' > unknown.hash john unknown.hash # Loaded 1 password hash (sha512crypt, crypt(3) $6$ [SHA512 256/256 AVX2 4x]) # Or use hashid hashid '$2a$12$R9h...' # Analyzing '$2a$12$R9h...' # [+] Blowfish(OpenBSD) # [+] bcrypt # List all supported formats john --list=formats | tr ',' '\n' | grep -i bcrypt ``` ### Step 2: Convert Files into Crackable Hashes ```bash # Password-protected ZIP zip2john secret.zip > secret.hash john secret.hash # Password-protected PDF pdf2john.pl confidential.pdf > pdf.hash john pdf.hash # Encrypted SSH private key ssh2john id_rsa > idrsa.hash john idrsa.hash # KeePass database keepass2john db.kdbx > kp.hash john kp.hash # macOS keychain, Office docs, LUKS, 1Password — *2john helpers ship in Jumbo ls /usr/share/john/*2john* ``` ### Step 3: Run Attacks ```bash # Wordlist attack john --wordlist=/usr/share/wordlists/rockyou.txt secret.hash # Wordlist + rules (mangles words: "Summer" → "Summer!", "summer2026", "S0mmer") john --wordlist=rockyou.txt --rules=Jumbo secret.hash # Incremental (brute-force) — use only against fast hashes or short passwords john --incremental=ASCII secret.hash # Mask attack — you know the pattern john --mask='?u?l?l?l?l?d?d?d?d' secret.hash # ?u upper, ?l lower, ?d digit, ?s symbol, ?a all # Limit duration; resume later john --max-run-time=3600 secret.hash john --restore ``` ### Step 4: Show and Export Results ```bash # Display cracked results john --show secret.hash # secret.zip:hunter2:::::secret.zip # Only count / only uncracked john --show=left secret.hash # Pot file (already-cracked cache) lives at ~/.john/john.pot cat ~/.john/john.pot # Export cracked passwords, one per line john --show secret.hash | awk -F: 'NF>1 {print $2}' ``` ### Step 5: Tuning and Multi-Core ```bash # All CPU cores (OpenMP builds) john --fork=8 secret.hash # Distribute across machines (node 1 of 4) john --node=1/4 --fork=8 secret.hash # Benchmark your hardware john --test --format=bcrypt john --test --format=sha512crypt ``` ## Examples ### Example 1: Crack an /etc/shadow Entry (Own System) ```bash # On the system you own sudo cp /etc/shadow /tmp/shadow sudo cp /etc/passwd /tmp/passwd chmod 644 /tmp/shadow /tmp/passwd # Combine into JtR input unshadow /tmp/passwd /tmp/shadow > creds.txt head -1 creds.txt # root:$6$abc...:0:0:root:/root:/bin/bash john --wordlist=/usr/share/wordlists/rockyou.txt --rules=Single creds.txt john --show creds.txt # root:hunter2:0:0:root:/root:/bin/bash rm /tmp/shadow /tmp/passwd creds.txt ``` ### Example 2: CTF — Recover a ZIP Password ```bash # Given challenge.zip from a CTF zip2john challenge.zip > zip.hash cat zip.hash # challenge.zip:$zip2$*0*3*0*...*$/zip2$:::challenge.zip # Try rockyou first john --wordlist=/usr/share/wordlists/rockyou.txt zip.hash # Add rules if the straight dictionary fails john --wordlist=rockyou.txt --rules=KoreLogic zip.hash # Show the result john --show zip.hash # challenge.zip:flag2026 # Unzip with the recovered password unzip -P flag2026 challenge.zip ``` ## Guidelines - **Only crack hashes you own or are authorized to crack.** Possessing and cracking third-party hashes without permission is illegal in most jurisdictions. - Always identify the hash format first — picking the wrong one wastes hours or produces silent miscracks. - The "Jumbo" community build (`john-jumbo`) supports far more formats than upstream. Install via your distro or compile from source. - Order of attacks: wordlist → wordlist+rules → mask (if you know the pattern) → incremental. Don't start with brute-force. - Fast hashes (MD5, NTLM, SHA1) belong on hashcat with a GPU. JtR excels at slow hashes (bcrypt, sha512crypt, PBKDF2). - Use `--fork=N` on multi-core systems; default JtR only uses one thread. - Save partial work — JtR writes progress to `~/.john/john.rec` every minute. `john --restore` resumes. - The `john.pot` file is your institutional memory. 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