# Authentication Analysis Report

## 1. Executive Summary

- **Analysis Status:** Complete
- **Key Outcome:** Multiple critical authentication flaws were identified across all layers of the authentication system, including transport security, session management, credential storage, and brute force protection.
- **Purpose of this Document:** This report provides strategic context on the application's authentication mechanisms, dominant flaw patterns, and architectural details necessary to effectively exploit the vulnerabilities listed in the exploitation queue.

**Critical Findings Summary:**
- ✗ **No HTTPS enforcement** - Credentials and sessions transmitted in plaintext
- ✗ **Plaintext password storage** - No cryptographic hashing whatsoever
- ✗ **Hardcoded secret key** - Session forgery possible by anyone with source access
- ✗ **No rate limiting** - Unlimited brute force attempts
- ✗ **Session fixation vulnerability** - Session IDs not rotated after authentication
- ✗ **Session replay vulnerability** - Sessions remain valid after logout
- ✗ **GET-based logout** - CSRF logout attacks possible
- ✗ **Default credentials** - Hardcoded `user:user` account

## 2. Dominant Vulnerability Patterns

### Pattern 1: Fundamentally Broken Credential Management

**Description:** The application stores passwords in plaintext without any cryptographic hashing. The User model stores the password field as a plain string, and authentication compares user-supplied passwords directly against stored plaintext values in the database query.

**Code Evidence:**
- **Location:** `app.py` lines 24-27, 60
- **User Model:** `password = db.Column(db.String(100), nullable=False)` - No hashing
- **Authentication Query:** `User.query.filter_by(username=username, password=password).first()` - Direct plaintext comparison
- **Default Credentials:** Lines 39-42 create `user:user` account with plaintext password

**Implication:** Any database compromise immediately exposes all user credentials. Combined with the hardcoded secret key and default credentials, attackers can gain immediate access to the system. This violates fundamental security principles and compliance requirements (GDPR Article 32, PCI DSS 8.2.1, OWASP A02:2021).

**Representative Findings:** `AUTH-VULN-01` (default credentials), `AUTH-VULN-02` (plaintext storage)

### Pattern 2: Session Management Failures

**Description:** Multiple critical flaws in session handling create opportunities for session hijacking, fixation, and replay attacks. The application uses client-side signed cookies with a hardcoded secret key, fails to rotate session IDs after authentication, transmits sessions over HTTP, and doesn't invalidate sessions server-side on logout.

**Code Evidence:**
- **Hardcoded Secret:** `app.py` line 10 - `app.secret_key = 'U@T!F*G(EBDOUNIX_PWU)VBDY$%^&*('`
- **No Session Rotation:** `app.py` line 62 - `login_user(user)` doesn't regenerate session ID
- **No Secure Flag:** No `SESSION_COOKIE_SECURE` configuration
- **No SameSite Flag:** No `SESSION_COOKIE_SAMESITE` configuration
- **Client-Side Sessions:** No server-side session store (uses Flask default client-side signed cookies)
- **Logout Issues:** `app.py` lines 71-75 - Only removes `_user_id` from cookie, doesn't clear session or invalidate server-side

**Session Cookie Observed (Live Testing):**
```
Set-Cookie: session=.eJwlzjESAjEIAMC_UFtAIgTuM04IMNreeZXj39Wx3mZfcKs9jztsz_3MC9weARvErEJe2nsKh7JiEReGomrTyRGLFrKxSlaamLGbBsW41lxNwrCjOnVM1xDzJj7yJ8M5zWNgj0ZjuidVLq9k67NwlOSSgm_kPHL_bwjeH_n2MLE.aQKmQQ.zmkaIcOVQn-VhJXU4pha2RsmL5g; HttpOnly; Path=/
```

**Flags Present:** HttpOnly, Path=/  
**Flags MISSING:** Secure, SameSite

**Implication:** Attackers can hijack user sessions through multiple vectors:
1. Network interception (no Secure flag - sessions sent over HTTP)
2. Session fixation (no ID rotation after login)
3. Session replay (captured cookies work indefinitely, even after logout)
4. Cookie forgery (hardcoded secret key enables arbitrary session creation)

**Representative Findings:** `AUTH-VULN-03` (session cookie flags), `AUTH-VULN-04` (session fixation), `AUTH-VULN-05` (hardcoded secret), `AUTH-VULN-08` (session replay)

### Pattern 3: Missing Abuse Prevention Controls

**Description:** The application has zero defense mechanisms against automated attacks. No rate limiting exists on any endpoint, no CAPTCHA protection, no account lockout after failed attempts, no monitoring or logging of authentication events, and no delays or throttling for repeated failures.

**Code Evidence:**
- **No Rate Limiting Library:** `requirements.txt` and `app.py` lines 1-6 show no Flask-Limiter or similar
- **No CAPTCHA:** Login form (`templates/login.html` lines 7-17) contains only username/password fields
- **No Failed Attempt Tracking:** User model (lines 24-27) has no `failed_login_attempts` or `account_locked` fields
- **No Logging:** No logging module imported or configured in `app.py`
- **No Delays:** Login handler (lines 55-68) returns immediately on failure

**Implication:** Attackers can execute unlimited brute force, credential stuffing, or password spraying attacks at full network speed without any resistance or detection. Combined with plaintext password storage and default credentials, accounts can be compromised in minutes.

**Representative Findings:** `AUTH-VULN-06` (rate limiting missing), `AUTH-VULN-07` (no cache control)

### Pattern 4: Transport Security Gaps

**Description:** The application transmits sensitive authentication data over unencrypted HTTP without any HTTPS enforcement, HSTS headers, or secure cookie flags. The Werkzeug development server runs with `debug=True` on plain HTTP.

**Code Evidence:**
- **No HTTPS Enforcement:** No redirection, no HSTS headers, no middleware
- **No Cache Headers:** Login/logout endpoints have no `Cache-Control: no-store` or `Pragma: no-cache`
- **Development Server:** `app.py` line 119 - `app.run(host='0.0.0.0', port=5003, debug=True)`
- **Missing Secure Flag:** Session cookies transmitted over HTTP (confirmed via live testing)

**Implication:** Credentials and session cookies are transmitted in cleartext over the network, enabling man-in-the-middle attacks, credential theft, and session hijacking via network sniffing.

**Representative Findings:** `AUTH-VULN-03` (cookie flags), `AUTH-VULN-07` (cache headers)

## 3. Strategic Intelligence for Exploitation

### Authentication Method
The system uses Flask-Login for session-based authentication with client-side signed cookies. The authentication flow:

1. **Credential Submission:** User submits username/password via POST to `/login`
2. **Plaintext Verification:** Database query compares plaintext password: `User.query.filter_by(username=username, password=password).first()`
3. **Session Creation:** `login_user(user)` stores `_user_id` in Flask session
4. **Cookie Generation:** Flask's `itsdangerous` library signs session data with secret key and returns cookie
5. **Session Validation:** `@login_required` decorator checks for `_user_id` in cookie

### Session Token Details

**Format:** Flask client-side signed cookie using `itsdangerous.URLSafeTimedSerializer`

**Structure:** `base64(json_payload).timestamp.hmac_signature`

**Example Cookie:**
```
session=.eJwlzjESAjEIAMC_UFtAIgTuM04IMNreeZXj39Wx3mZfcKs9jztsz_3MC9weARvErEJe2nsKh7JiEReGomrTyRGLFrKxSlaamLGbBsW41lxNwrCjOnVM1xDzJj7yJ8M5zWNgj0ZjuidVLq9k67NwlOSSgm_kPHL_bwjeH_n2MLE.aQKmQQ.zmkaIcOVQn-VhJXU4pha2RsmL5g
```

**Decoded Payload (base64):**
```json
{
  "_user_id": "1",
  "_fresh": true
}
```

**Signature Algorithm:** HMAC-SHA256 with hardcoded key: `U@T!F*G(EBDOUNIX_PWU)VBDY$%^&*(`

**Security Properties:**
- ✓ Signed (tampering detected)
- ✗ NOT encrypted (payload readable via base64 decode)
- ✗ NO server-side storage (client-side sessions only)
- ✗ NO server-side revocation possible

**Cookie Flags (Confirmed via Live Testing):**
- ✓ HttpOnly: True (not accessible via JavaScript)
- ✗ Secure: False (transmitted over HTTP)
- ✗ SameSite: Not set (vulnerable to CSRF)

**Session Lifetime:**
- Configuration: `app.permanent_session_lifetime = timedelta(minutes=5)` (line 11)
- **Actual Behavior:** Sessions do NOT expire because `session.permanent` is never set to `True`
- **Result:** Sessions valid until browser closes (non-permanent sessions)

### Default Credentials

**Username:** `user`  
**Password:** `user`

**Creation Logic:** `app.py` lines 39-42
```python
if not User.query.filter_by(username='user').first():
    user = User(username='user', password='user')
    db.session.add(user)
    db.session.commit()
```

**Impact:** Immediate authentication bypass for attackers who know these default credentials.

### Password Policy

**Strength Requirements:** NONE - No server-side validation  
**Length Requirements:** NONE - No minimum/maximum enforced  
**Complexity Requirements:** NONE - No character class requirements  
**Storage:** Plaintext (no hashing) - `password = db.Column(db.String(100), nullable=False)`

### Error Messages

**Failed Login Response:** `"Invalid credentials, please try again."`  
**User Enumeration:** ✓ Protected - Generic error message for both invalid username and invalid password  
**Timing Differences:** Minimal - Both scenarios execute same SQLite query

### Endpoints

**Authentication Endpoints:**
- `GET /` - Redirects to `/login`
- `GET /login` - Renders login form
- `POST /login` - Processes credentials (no CSRF token required)
- `GET /logout` - Terminates session (CSRF vulnerable - should be POST)

**Protected Endpoints (require authentication):**
- `GET /transactions` - View user's transactions
- `GET /add_transaction` - Render transaction form
- `POST /add_transaction` - Create transaction
- `GET /remind` - Payment reminder (also has SSTI vulnerability)

**Password Reset:** ✗ Does not exist

### Debug Mode

**Status:** ENABLED in production (`app.py` line 119: `debug=True`)

**Implications:**
- Werkzeug interactive debugger accessible on errors
- Detailed stack traces expose code structure
- Console PIN can sometimes be obtained for RCE
- Should be disabled in production

## 4. Secure by Design: Validated Components

These components were analyzed and found to have adequate defenses. They are low-priority for authentication exploitation.

| Component/Flow | Endpoint/File Location | Defense Mechanism Implemented | Verdict |
|---|---|---|---|
| SQL Injection Prevention | `app.py` line 60, 85-87, 96-97 | SQLAlchemy ORM parameterization - all queries use `.filter_by()` with keyword arguments | SAFE |
| User Enumeration Prevention | `app.py` line 65 | Generic error message: "Invalid credentials, please try again." - Does not distinguish between invalid username vs password | SAFE |
| HttpOnly Cookie Flag | Flask default configuration | Session cookie has HttpOnly flag (confirmed via live testing), preventing JavaScript access | SAFE |
| Session Signing | Flask's `itsdangerous` library | Session cookies signed with HMAC-SHA256, tampering detected (though secret is hardcoded) | SAFE (integrity only) |

**Notes:**
- While session cookies are properly signed and prevent tampering, the hardcoded secret key undermines this protection
- User enumeration is prevented through generic error messages, but unlimited brute force attempts compensate for this
- SQL injection protection via ORM is effective, but other injection vectors exist (SSTI in `/remind`)

## 5. Attack Vectors for Exploitation Phase

### Vector 1: Default Credential Authentication Bypass
**Entry Point:** POST /login  
**Credentials:** `user:user`  
**Expected Outcome:** Immediate authentication with valid session cookie  
**Follow-up:** Access all authenticated endpoints, exploit SSTI in `/remind` for RCE

### Vector 2: Brute Force Attack (Unlimited Attempts)
**Entry Point:** POST /login  
**Technique:** Automated password guessing with tools like Hydra or Burp Intruder  
**Advantage:** No rate limiting, no CAPTCHA, no account lockout, no delays  
**Expected Speed:** 1000+ attempts per second possible  
**Target:** Default `user` account or discovered usernames

### Vector 3: Session Cookie Forgery
**Entry Point:** Direct cookie manipulation  
**Required Knowledge:** Secret key (hardcoded in source: `U@T!F*G(EBDOUNIX_PWU)VBDY$%^&*(`)  
**Technique:** Use Flask's `itsdangerous` library to craft cookie with arbitrary `_user_id`  
**Expected Outcome:** Authentication as any user without credentials

### Vector 4: Session Hijacking (Network Interception)
**Entry Point:** HTTP traffic sniffing  
**Technique:** Capture session cookie from unencrypted HTTP traffic (missing Secure flag)  
**Tool:** Wireshark, tcpdump, mitmproxy  
**Expected Outcome:** Replay captured cookie to impersonate user

### Vector 5: Session Fixation
**Entry Point:** Pre-authentication session manipulation  
**Technique:** Provide victim with a known session ID before authentication  
**Exploit:** Session ID not rotated after successful login (line 62: only `login_user()`, no regeneration)  
**Expected Outcome:** Attacker knows victim's session ID after they log in

### Vector 6: Session Replay After Logout
**Entry Point:** Captured session cookie  
**Technique:** Replay session cookie after user has logged out  
**Why It Works:** `logout_user()` only removes `_user_id` from cookie client-side, no server-side revocation  
**Expected Outcome:** Captured cookie remains valid indefinitely

### Vector 7: CSRF Logout Attack
**Entry Point:** GET /logout  
**Technique:** Embed logout request in malicious page: `<img src="http://localhost:5093/logout">`  
**Why It Works:** Logout uses GET method (line 71), no CSRF protection (disabled on line 18)  
**Expected Outcome:** Force victim logout, potentially chain with session fixation

## 6. Exploitation Constraints & Considerations

### Network Access Requirements
All vulnerabilities are exploitable from external network via `http://localhost:5093`. No VPN or internal access required.

### Prerequisites
- **Default Credentials:** No prerequisites - credentials are `user:user`
- **Brute Force:** Requires username knowledge (mitigated by default account existence)
- **Session Forgery:** Requires source code access to obtain secret key
- **Session Hijacking:** Requires network position (MitM) or XSS to steal cookie
- **Session Fixation:** Requires victim interaction (click link with fixed session)

### Rate Limiting Considerations
**NONE** - No rate limiting exists. Exploitation can proceed at full speed.

### Detection Risk
**VERY LOW** - No authentication logging, no monitoring, no alerting. Attacks are invisible to defenders.

### Multi-Step Attack Chains

**Chain 1: Default Login → SSTI RCE**
1. Authenticate with `user:user`
2. Navigate to `/remind?date={{SSTI_PAYLOAD}}`
3. Execute arbitrary Python code (documented in INJECTION analysis)

**Chain 2: Session Forgery → Account Takeover**
1. Obtain secret key from source code
2. Craft cookie with target user's `_user_id`
3. Send cookie with any request to authenticated endpoints

**Chain 3: Brute Force → Session Hijacking → Persistence**
1. Brute force login to obtain valid credentials
2. Capture session cookie (stored indefinitely)
3. Use cookie even after victim logs out (session replay)

## 7. Code-Level Implementation Notes for Exploitation

### Session Cookie Forgery Example
```python
from itsdangerous import URLSafeTimedSerializer

secret_key = 'U@T!F*G(EBDOUNIX_PWU)VBDY$%^&*('
serializer = URLSafeTimedSerializer(secret_key)

# Forge session for user_id=1
session_data = {'_user_id': '1', '_fresh': True}
forged_cookie = serializer.dumps(session_data)

# Use forged_cookie in Cookie header
```

### Brute Force Attack Pattern
```bash
# Using Hydra
hydra -l user -P /usr/share/wordlists/rockyou.txt localhost -s 5093 http-post-form "/login:username=^USER^&password=^PASS^:Invalid credentials"

# Using Burp Intruder - no delays needed
# POST /login, payload positions on password field
```

### Session Replay Test
```bash
# 1. Login and capture cookie
curl -i -X POST http://localhost:5093/login -d "username=user&password=user" -c cookies.txt

# 2. Access authenticated endpoint
curl -b cookies.txt http://localhost:5093/transactions

# 3. Logout
curl -b cookies.txt http://localhost:5093/logout

# 4. Replay original cookie - STILL WORKS
curl -b cookies.txt http://localhost:5093/transactions
```

## 8. Remediation Priority (For Reference Only)

**P0 (Critical - Immediate):**
1. Hash passwords with bcrypt/argon2
2. Remove default credentials
3. Move secret key to environment variable
4. Disable debug mode

**P1 (High - Urgent):**
5. Implement rate limiting (Flask-Limiter)
6. Add session ID rotation after login
7. Enable HTTPS with Secure cookie flag
8. Change logout to POST method
9. Implement server-side session storage

**P2 (Medium):**
10. Add CAPTCHA to login form
11. Implement account lockout
12. Add cache-control headers
13. Add SameSite cookie flag
14. Implement authentication logging

---

**Report Generated:** 2025-10-29  
**Analysis Scope:** Authentication mechanisms only (AuthN)  
**Next Phase:** Exploitation - weaponize findings via exploitation queue  
**Related Analysis:** See INJECTION analysis for SSTI/RCE vulnerability in `/remind` endpoint