sc-auth

sc-auth is a skill for Claude Code from fatihkan/badi. It costs 19 tokens per session (1,163 once invoked), scanned A, a copy of sc-auth, MIT.

An authentication security review skill for checking how applications verify users. It covers passwords, sessions, tokens, OAuth, API keys, and multi-factor authentication.

In plain words
What is it for?
It is for reviewing login and registration code, password storage, brute-force protection, credential handling, password recovery, and multi-factor authentication.
Why use it?
It helps uncover ways an attacker could guess credentials, bypass sign-in, steal or misuse sessions, or reset a password insecurely.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Part of the badi plugin — 81 skills, 86 commands, 30 agents, 7 hooks shipped together

Good fit It is for reviewing login and registration code, password storage, brute-force protection, credential handling, password recovery, and multi-factor authentication.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/fatihkan/badi/sc-auth
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add fatihkan/badi --skill sc-auth
Clone the repo
git clone --depth 1 https://github.com/fatihkan/badi

Made for: Claude Code.

Or install badi, the plugin that ships this one along with the rest of its 81 skills, 86 commands, 30 agents, 7 hooks.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for sc-auth

README.md
[![agentmods](https://agentmods.dev/badge/skills/fatihkan/badi/sc-auth.svg)](https://agentmods.dev/skills/fatihkan/badi/sc-auth)
Your own site
<a href="https://agentmods.dev/skills/fatihkan/badi/sc-auth"><img src="https://agentmods.dev/badge/skills/fatihkan/badi/sc-auth.svg" alt="Measured on agentmods" height="20"></a>
Per session 19 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,163 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 94% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00019 $0.01163
Opus 5 $0.00010 $0.00581
Sonnet 5 $0.00004 $0.00233
Haiku 4.5 $0.00002 $0.00116

Measured yesterday against content hash 25b22f904563, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

sc-auth scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

94% identical to sc-auth — 1 line differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.claude/skills-vault/security-check/sc-auth/SKILL.md · 135 lines

How it starts

The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SC: Authentication Flaws

Purpose

Detects authentication vulnerabilities including weak password policies, missing brute force protection, insecure password storage, authentication bypass, hardcoded credentials, insecure password reset flows, and missing multi-factor authentication. Covers session-based, JWT, OAuth, and API key authentication models.

Activation

Called by sc-orchestrator during Phase 2. Runs against all web applications and APIs.

Phase 1: Discovery

File Patterns to Search

**/*auth*, **/*login*, **/*signin*, **/*signup*, **/*register*,
**/*password*, **/*credential*, **/*token*, **/*session*,
**/*oauth*, **/*mfa*, **/*2fa*, **/middleware/*, **/guards/*

Keyword Patterns to Search

# Password hashing
"md5(", "sha1(", "sha256(", "hashlib.md5", "hashlib.sha1",
"MessageDigest.getInstance(\"MD5\"", "MessageDigest.getInstance(\"SHA-1\"",
"bcrypt", "argon2", "scrypt", "pbkdf2", "password_hash(",
"crypto.createHash("

# Authentication logic
"password ==", "password ===", "password.equals(",
"authenticate(", "login(", "verify_password(", "check_password(",
"compareSync(", "compare("

# Hardcoded credentials
"password = \"", "password = '", "passwd", "secret",
"api_key = \"", "token = \"", "admin:admin", "root:root"

# Brute force protection
"rate_limit", "throttle", "max_attempts", "lockout",
"login_attempts", "failed_attempts"

Vulnerability Categories

1. Weak Password Hashing:

# VULNERABLE: MD5/SHA for password storage
password_hash = hashlib.md5(password.encode()).hexdigest()

# SAFE: bcrypt with appropriate cost factor
password_hash = bcrypt.hashpw(password.encode(), bcrypt.gensalt(rounds=12))

2. Missing Brute Force Protection:

// VULNERABLE: No rate limiting on login
app.post('/login', async (req, res) => {
  const user = await User.findOne({ email: req.body.email });
  if (user && await bcrypt.compare(req.body.password, user.password)) {
    return res.json({ token: generateToken(user) });
  }
  return res.status(401).json({ error: 'Invalid credentials' });
});

// SAFE: With rate limiting
const loginLimiter = rateLimit({ windowMs: 15 * 60 * 1000, max: 5 });
app.post('/login', loginLimiter, async (req, res) => { /* ... */ });

Read the full file on GitHub · 135 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 135 lines · 19 tokens per session scan A 25b22f904563

Subscribe to this mod's changes

sc-auth is a skill published in the GitHub repository fatihkan/badi (7 stars, last pushed 2d ago), licensed MIT. It adds 19 tokens to every session and 1,163 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 94% identical to sc-auth, differing in 1 line, and is treated as a copy.

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