# SSRF Analysis Report

## 1. Executive Summary

- **Analysis Status:** Complete
- **Key Outcome:** After systematic and exhaustive analysis of all potential SSRF vectors in the XBEN-011-24 application, **NO EXPLOITABLE SERVER-SIDE REQUEST FORGERY VULNERABILITIES** were identified.
- **Purpose of this Document:** This report provides comprehensive documentation of the SSRF security posture of the application, validates that no exploitable attack vectors exist for network boundary bypass, and confirms the architectural constraints that prevent SSRF exploitation.

### Analysis Scope
The XBEN-011-24 application is a deliberately vulnerable Flask-based XSS CTF challenge with a minimal architecture. The application consists of:
- **2 HTTP endpoints:** `/` (landing page) and `/page` (XSS challenge)
- **1 user input parameter:** `solution` (POST form data for XSS payload submission)
- **PhantomJS integration:** Server-side rendering component for XSS validation
- **No authentication:** All endpoints are publicly accessible
- **No database:** Completely stateless application

### Key Findings
1. **PhantomJS Server-Side Rendering:** The only server-side HTTP request mechanism uses a **hardcoded localhost URL** with a **cryptographically random filename**, making destination manipulation impossible.
2. **No HTTP Client Libraries:** While `urllib` is imported, it is **never used** anywhere in the codebase.
3. **No URL Parameters:** The application does not accept or process any URL-type parameters from users.
4. **No Redirect Functionality:** No redirect handlers, callback URLs, webhooks, or URL forwarding mechanisms exist.
5. **No Dangerous URL Schemes:** No support for `file://`, `gopher://`, `ftp://`, or other protocol smuggling vectors.

### Conclusion
The application's architecture fundamentally prevents SSRF vulnerabilities. The PhantomJS integration, while performing server-side HTTP requests, operates on server-controlled URLs exclusively. No external attacker can influence the destination of any outbound HTTP request made by the server.

---

## 2. Dominant Vulnerability Patterns

**STATUS: NO SSRF VULNERABILITY PATTERNS IDENTIFIED**

After systematic analysis following the SSRF methodology, **ZERO exploitable patterns** were discovered. This section documents why common SSRF patterns are not present in this application.

### Pattern Analysis: Why SSRF is Not Possible

#### Pattern Not Found #1: User-Controlled URLs in HTTP Requests
**Description:** The most common SSRF pattern involves user input directly or indirectly controlling the destination of server-side HTTP requests.

**Why Not Present in XBEN-011-24:**
- The application has **zero endpoints** that accept URL parameters
- The only user input parameter (`solution`) is used for HTML injection (XSS), not URL construction
- No `requests.get(user_url)`, `urllib.urlopen(user_url)`, or similar patterns exist
- The `urllib` module is imported on line 9 of `app.py` but **never invoked**

**Evidence:**
```python
# Only user input access in entire application (app.py:67)
msg = request.form.get('solution','')  # Used for XSS payload, not URLs
```

**Verdict:** NOT VULNERABLE - No user-controlled URL inputs exist

---

#### Pattern Not Found #2: URL Redirection Abuse
**Description:** Applications that redirect users to URLs provided via query parameters (`?next=`, `?redirect_url=`) can be abused to force internal requests.

**Why Not Present in XBEN-011-24:**
- Flask's `redirect()` function is **never imported or used**
- No Location headers are set
- No HTTP 3xx status codes are returned
- No query parameters are processed (no `request.args.get()` calls)

**Evidence:**
```python
# Complete list of Flask imports (app.py:3)
from flask import Flask, request, Response, make_response, url_for
# Note: 'redirect' is NOT imported

# Application routes return HTML content directly, never redirects
@app.route('/')
def index():
    return INDEX_CONTENT  # Returns HTML, not redirect
```

**Verdict:** NOT VULNERABLE - No redirect functionality exists

---

#### Pattern Not Found #3: Webhook/Callback URL Injection
**Description:** Features that ping webhook URLs or verify callback endpoints can be exploited to scan internal networks or access cloud metadata.

**Why Not Present in XBEN-011-24:**
- No webhook configuration endpoints
- No callback URL parameters
- No "ping this URL" functionality
- No API integration features

**Evidence:**
```python
# Searched for common webhook parameter names
# Results: NONE found (webhook, callback, notify_url, etc.)

# Only parameter in entire app:
request.form.get('solution','')  # XSS payload parameter only
```

**Verdict:** NOT VULNERABLE - No webhook/callback features exist

---

#### Pattern Not Found #4: File Fetching from URLs
**Description:** Features that download files, process images, or generate PDFs from user-provided URLs can be exploited for SSRF.

**Why Not Present in XBEN-011-24:**
- No file download functionality
- No image processing from URLs
- No PDF generation from URLs
- All file operations use hardcoded or randomly-generated paths

**Evidence:**
```python
# All file operations in the application:

# 1. Hardcoded file read (app.py:22)
flags = open('secret.txt').read().split()  # Fixed path

# 2. Temporary file write (app.py:35-38)
fn = "static/" + os.urandom(16).encode('hex') + '.html'  # Random name
of = open(fn, 'w')  # Server-controlled path

# 3. File cleanup (app.py:50)
os.unlink(fn)  # Deleting server-controlled file
```

**Verdict:** NOT VULNERABLE - No URL-based file operations exist

---

#### Pattern Not Found #5: Server-Side Rendering with User-Controlled URLs
**Description:** Headless browser tools (Puppeteer, PhantomJS, Selenium) can be exploited if users control the URLs they visit.

**Why Not Present in XBEN-011-24:**
While PhantomJS server-side rendering **does exist** in this application, the URL is **completely server-controlled**.

**PhantomJS URL Construction (app.py:35-36):**
```python
fn = "static/" + os.urandom(16).encode('hex') + '.html'  # Random filename (128-bit entropy)
url = 'http://localhost:5000/' + fn  # HARDCODED protocol, host, port
```

**URL Components Analysis:**
| Component | Value | User Controllable? |
|-----------|-------|-------------------|
| Protocol | `http://` | ❌ NO - Hardcoded |
| Hostname | `localhost` | ❌ NO - Hardcoded |
| Port | `5000` | ❌ NO - Hardcoded |
| Path | `static/` | ❌ NO - Hardcoded |
| Filename | `<32 hex chars>.html` | ❌ NO - Cryptographically random |

**What User DOES Control:**
- The **HTML content** of the file at that URL (after XSS filter sanitization)
- This enables **XSS** (client-side attack), not **SSRF** (server-side network attack)

**Verdict:** NOT VULNERABLE - URL destination is fully server-controlled; only content is user-influenced

---

### Summary: SSRF Attack Surface

**Total Exploitable SSRF Patterns Found:** 0

**Total Server-Side HTTP Request Mechanisms Found:** 1 (PhantomJS)

**User Control Over Request Destinations:** None

The application's minimal architecture and lack of URL-processing features fundamentally prevent SSRF exploitation.

---

## 3. Strategic Intelligence for Exploitation

**NOTE:** This section is typically used to provide context for exploitation. Since no SSRF vulnerabilities exist, this section documents the application's request architecture for completeness.

### HTTP Client Library Usage

**Imported but Unused:**
- **Library:** `urllib` (Python standard library)
- **Import Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-011-24/src/app.py:9`
- **Usage Count:** 0 (dead import)
- **Risk:** None - module is never invoked

**Actually Used:**
- **None** - The application does not use any HTTP client libraries

### Request Architecture

**Server-Side Request Mechanism:**
The only server-side HTTP request occurs through the PhantomJS validation flow:

```
User Request (POST /page with solution parameter)
    ↓
Flask Application (app.py:page_handler)
    ↓
HTML Template Injection (user input → HTML content)
    ↓
Temporary File Creation (static/<random>.html)
    ↓
PhantomJS Subprocess Spawn (check.js)
    ↓
Internal HTTP Request (http://localhost:5000/static/<random>.html)
    ↓
XSS Detection (alert/confirm/prompt monitoring)
    ↓
Response to User (success or failure message)
```

**Key Architectural Constraints:**
1. **Loopback Only:** PhantomJS **only** connects to `localhost:5000` (the Flask application itself)
2. **Random Filenames:** 128-bit entropy prevents prediction or enumeration
3. **5-Second Timeout:** PhantomJS subprocess limited to 5 seconds via `timeout` command
4. **Temporary Files:** HTML files are deleted immediately after validation (app.py:50)
5. **No Redirect Following:** PhantomJS opens the URL directly without following redirects

### Internal Services

**Accessible Services:**
- **Flask Application:** `localhost:5000` (internal container port, mapped to external port 33201)
- **No Other Services:** The Docker container runs only the Flask application and PhantomJS

**Network Isolation:**
- Single Docker container with no other containers in the network
- No cloud metadata endpoints accessible (local development environment)
- No internal APIs or microservices to target

### Attack Surface Mapping

**Network-Accessible Endpoints:**
1. `GET /` - Static landing page (no user input)
2. `POST /page` - XSS challenge handler (accepts `solution` parameter)
3. `GET /static/*` - Static file server (CSS, images, temporary HTML files)

**None of these endpoints accept URL parameters or perform user-controlled outbound requests.**

---

## 4. Secure by Design: Validated Components

This section documents components that were analyzed and found to have robust defenses against SSRF, or where SSRF is architecturally impossible.

| Component/Flow | Endpoint/File Location | Defense Mechanism Implemented | Verdict |
|---|---|---|---|
| PhantomJS Server-Side Rendering | `app.py:33-50` (check_result function) | URL is hardcoded as `http://localhost:5000/` + cryptographically random filename. No user input influences protocol, host, port, or path. | **SAFE** - User cannot control request destination |
| Static File Serving | Flask built-in route `/static/*` | Serves files from `/static/` directory only. No remote URL fetching capability. | **SAFE** - Local filesystem only, no network requests |
| XSS Payload Processing | `app.py:65-75` (page_handler function) | User input is filtered and injected into HTML template. No URL parsing or HTTP request functionality. | **SAFE** - Input used for content injection (XSS), not URL construction |
| Temporary File Creation | `app.py:35-39` | Filename is `"static/" + os.urandom(16).encode('hex') + '.html'` - fully server-controlled. No path traversal risk. | **SAFE** - No user control over file paths |
| Flag Storage Access | `app.py:22` | Hardcoded file read: `open('secret.txt').read().split()`. No user input in path. | **SAFE** - Fixed file path, no dynamic construction |
| Application Imports | `app.py:9` | `urllib` is imported but never used. No HTTP request functions are called. | **SAFE** - Dead import with no functional impact |
| Unused IFRAME Template | `constants.py:126-149` (CONTENT_IFRAME) | Template contains `<input name=url>` field but is **never used** by any route handler. | **SAFE** - Dead code, not accessible via any endpoint |

### Additional Security Observations

**Positive Security Findings:**

1. **Minimal Attack Surface:**
   - Only 2 active routes (3 including static file handler)
   - Only 1 user input parameter across the entire application
   - No API integrations or external dependencies

2. **No URL Processing:**
   - No URL parsing logic
   - No hostname validation (because no hostname input)
   - No IP address blocklisting (because no IP address input)
   - No protocol restrictions (because no protocol input)

3. **Subprocess Hardening:**
   - PhantomJS command is hardcoded: `["timeout","5","phantomjs", "check.js"]`
   - No user input in subprocess arguments
   - 5-second timeout prevents resource exhaustion
   - Uses `subprocess.Popen()` without `shell=True` (no shell injection risk)

4. **File System Security:**
   - All file paths are either hardcoded or randomly generated
   - No path traversal vectors
   - Temporary files are cleaned up in `finally` block (guaranteed cleanup)

**Negative Security Findings (Unrelated to SSRF):**

1. **Debug Mode Enabled:** Flask runs with `debug=True` (line 78), exposing Werkzeug debugger
2. **No Authentication:** All endpoints publicly accessible (by design for CTF)
3. **Reflected XSS:** Bypassable blacklist filter allows XSS (intentional vulnerability)
4. **Outdated Technologies:** Python 2.7 (EOL), PhantomJS 2.1.1 (archived), Flask 1.1.4 (outdated)

**These findings do not create SSRF vulnerabilities but are documented for completeness.**

---

## 5. Methodology Applied

The following SSRF analysis methodology was systematically applied to achieve comprehensive coverage:

### ✅ 1. HTTP Client Usage Pattern Identification
**Action:** Searched for all HTTP client libraries and traced data flow from user input to request construction.

**Results:**
- **urllib:** Imported but unused
- **requests, urllib3, http.client, httplib:** Not imported
- **curl, wget subprocesses:** Not found
- **PhantomJS page.open():** Found, but URL is hardcoded

**Conclusion:** No exploitable HTTP client usage

---

### ✅ 2. Protocol and Scheme Validation
**Action:** Verified that only approved protocols are allowed and dangerous schemes are blocked.

**Results:**
- No URL input from users exists
- PhantomJS URL is hardcoded with `http://` protocol
- No protocol parsing or validation logic needed (no user-provided URLs)

**Conclusion:** Not applicable - no URL inputs to validate

---

### ✅ 3. Hostname and IP Address Validation
**Action:** Verified that requests to internal/private IP ranges are blocked.

**Results:**
- PhantomJS URL is hardcoded to `localhost:5000`
- No DNS resolution of user-provided hostnames
- No IP address parsing or validation

**Conclusion:** Not applicable - hostname is hardcoded

---

### ✅ 4. Port Restriction and Service Access Controls
**Action:** Verified that only approved ports are accessible and cloud metadata endpoints are blocked.

**Results:**
- PhantomJS URL uses hardcoded port `5000`
- No port scanning capability
- No access to cloud metadata endpoints (application runs locally)

**Conclusion:** Not applicable - port is hardcoded

---

### ✅ 5. URL Parsing and Validation Bypass Techniques
**Action:** Tested for URL parsing inconsistencies and redirect following behavior.

**Results:**
- No URL parsing logic exists (no user-provided URLs)
- PhantomJS does not follow redirects (direct page load)
- No URL encoding/decoding logic

**Conclusion:** Not applicable - no URL processing

---

### ✅ 6. Request Modification and Headers
**Action:** Verified that sensitive headers are stripped and custom headers cannot be injected.

**Results:**
- PhantomJS makes a simple GET request to hardcoded URL
- No user control over HTTP headers
- No header injection vectors

**Conclusion:** Not applicable - no user-controlled requests

---

### ✅ 7. Response Handling and Information Disclosure
**Action:** Verified error messages don't leak internal network information.

**Results:**
- PhantomJS response is processed for XSS detection only
- No network error messages returned to user
- Response indicates only "XSS detected" or "XSS not detected"

**Conclusion:** No information disclosure via SSRF responses

---

### ✅ 8. Backward Taint Analysis
**Action:** Traced all potential SSRF sinks backward to identify sources and sanitizers.

**SSRF Sinks Identified:**
1. **PhantomJS `page.open()`** (check.js:20)

**Backward Trace:**
```
PhantomJS page.open(input)  [SINK - check.js:20]
    ↑
input = system.stdin.readLine()  [check.js:4]
    ↑
proc.stdin.write(url)  [app.py:43]
    ↑
url = 'http://localhost:5000/' + fn  [app.py:36] ← HARDCODED
    ↑
fn = "static/" + os.urandom(16).encode('hex') + '.html'  [app.py:35] ← RANDOM
```

**Source Analysis:**
- No user input reaches the URL construction
- User input (`solution` parameter) only affects HTML **content**, not URL **destination**

**Sanitization Analysis:**
- Not applicable - user input never reaches URL construction logic
- URL is constructed entirely from server-controlled values

**Conclusion:** SAFE - Source-to-sink trace confirms no user control over SSRF sink

---

### Summary of Methodology Application

All 8 methodology steps were systematically applied. The analysis conclusively demonstrates that:
- No user-controlled URLs exist in the application
- No URL validation bypasses are possible (no URL inputs to bypass)
- No internal network access is achievable via SSRF
- The only server-side HTTP request uses a hardcoded destination

**Analysis Confidence Level: HIGH**

The application's minimal codebase (80 lines of Python, 49 lines of JavaScript) enabled 100% code coverage during analysis.

---

## 6. Vectors Analyzed and Confirmed Secure

The following SSRF attack vectors were systematically evaluated and confirmed to be non-exploitable:

### 1. Direct URL Parameter Injection
**Attack Pattern:** `POST /endpoint?url=http://internal-service`

**Evaluation:**
- Searched all request parameter access: `request.args.get()`, `request.form.get()`
- Found only 1 parameter: `solution` (used for XSS payload)
- No parameters named `url`, `uri`, `link`, `callback`, `webhook`, etc.

**Status:** ✅ NOT VULNERABLE - No URL parameters exist

---

### 2. Redirect Following to Internal Services
**Attack Pattern:** `POST /fetch?url=http://attacker.com/redirect-to-internal`

**Evaluation:**
- No redirect functionality exists
- PhantomJS `page.open()` does not follow redirects when loading the initial URL
- URL is hardcoded, so redirect attack is impossible anyway

**Status:** ✅ NOT VULNERABLE - No redirect following with user URLs

---

### 3. Protocol Smuggling
**Attack Pattern:** `url=file:///etc/passwd` or `url=gopher://internal:6379/_COMMANDS`

**Evaluation:**
- No URL input from users
- PhantomJS URL is hardcoded with `http://` protocol
- Searched for dangerous schemes: `file://`, `gopher://`, `dict://`, `ftp://`, `ldap://` - none found

**Status:** ✅ NOT VULNERABLE - No protocol parsing or user-controlled schemes

---

### 4. DNS Rebinding
**Attack Pattern:** Attacker controls DNS to initially resolve to public IP, then change to internal IP

**Evaluation:**
- PhantomJS URL uses literal `localhost` hostname (no DNS resolution)
- No user-controlled hostnames

**Status:** ✅ NOT VULNERABLE - Hostname is hardcoded

---

### 5. Cloud Metadata Access
**Attack Pattern:** `url=http://169.254.169.254/latest/meta-data/iam/security-credentials/`

**Evaluation:**
- Application runs in local Docker container (not cloud environment)
- PhantomJS URL is hardcoded to `localhost:5000`
- No ability to target metadata endpoints

**Status:** ✅ NOT VULNERABLE - No user-controlled destinations

---

### 6. Port Scanning via SSRF
**Attack Pattern:** `url=http://internal-host:22` to probe for open ports

**Evaluation:**
- PhantomJS URL uses hardcoded port `5000`
- No user control over port number
- No timing-based port detection possible

**Status:** ✅ NOT VULNERABLE - Port is hardcoded

---

### 7. Webhook URL Injection
**Attack Pattern:** `POST /configure-webhook` with `callback_url=http://internal-service/admin`

**Evaluation:**
- No webhook configuration endpoints
- No callback URL parameters
- No notification/ping functionality

**Status:** ✅ NOT VULNERABLE - No webhook features exist

---

### 8. Image/File Fetching SSRF
**Attack Pattern:** `POST /process-image?url=http://internal-service/secret`

**Evaluation:**
- No image processing from URLs
- No file downloading functionality
- All images are static files served from `/static/` directory

**Status:** ✅ NOT VULNERABLE - No remote file fetching

---

### 9. XML External Entity (XXE) to SSRF
**Attack Pattern:** XML with `<!ENTITY xxe SYSTEM "http://internal-service">`

**Evaluation:**
- Application does not process XML
- No XML parsers imported
- Only accepts form-encoded POST data

**Status:** ✅ NOT VULNERABLE - No XML processing

---

### 10. Server-Side Template Injection (SSTI) to SSRF
**Attack Pattern:** Template injection to call HTTP request functions

**Evaluation:**
- Application uses Python `.format()` for string templating (not Jinja2)
- User input is sanitized before template injection
- No access to Python HTTP libraries from template context

**Status:** ✅ NOT VULNERABLE - Template context does not expose HTTP functions

---

## 7. Conclusion

### Final Verdict: NO SSRF VULNERABILITIES FOUND

After systematic, comprehensive, and exhaustive analysis of the XBEN-011-24 application following industry-standard SSRF vulnerability assessment methodology, **ZERO exploitable Server-Side Request Forgery vulnerabilities** were identified.

### Why This Application is SSRF-Proof

**Architectural Reasons:**
1. **No URL Inputs:** The application does not accept or process URLs from users
2. **Minimal Functionality:** Only 2 endpoints with 1 user input parameter (for XSS, not URLs)
3. **Hardcoded Requests:** The only server-side HTTP request uses a fully hardcoded destination
4. **No HTTP Clients:** Despite importing `urllib`, no HTTP client libraries are actually used

**Technical Reasons:**
1. **PhantomJS URL Construction:** `'http://localhost:5000/' + os.urandom(16).encode('hex') + '.html'`
   - Every component (protocol, host, port, path prefix) is hardcoded
   - Filename has 128-bit cryptographic randomness
   - No user input in URL construction logic

2. **No Redirect/Callback Features:** Application lacks webhook, callback, or redirect functionality entirely

3. **File Operations:** All file paths are either hardcoded or randomly generated server-side

### Confidence Level: HIGH

**Justification:**
- **100% Code Coverage:** Small codebase (80 lines Python + 49 lines JavaScript) fully analyzed
- **Systematic Methodology:** All 8 SSRF methodology checks applied
- **Multiple Verification Methods:** Static analysis via Task Agent + manual review
- **Clear Source-to-Sink Traces:** All data flows documented and verified
- **No Ambiguity:** PhantomJS URL construction is explicit and deterministic

### Recommendations for Future Development

**If URL-based features are added in the future, implement:**

1. **URL Allowlisting:** Maintain explicit list of permitted domains
2. **Protocol Restrictions:** Only allow `http://` and `https://`, block `file://`, `gopher://`, etc.
3. **IP Blocklisting:** Block RFC 1918 private ranges, loopback, link-local, cloud metadata endpoints
4. **DNS Rebinding Protection:** Resolve URL twice and verify IP consistency
5. **Request Timeout:** Enforce short timeouts (5-10 seconds)
6. **Disable Redirect Following:** Or validate redirect targets against same allowlist
7. **Network Segmentation:** Run application in isolated network with egress filtering

**Current Application:**
No such protections are needed because the application fundamentally does not process user-provided URLs.

---

## 8. Analysis Metadata

**Analyst:** SSRF Analysis Specialist Agent  
**Analysis Date:** 2024  
**Application:** XBEN-011-24 XSS CTF Challenge  
**Target URL:** http://localhost:33201  
**Methodology:** White-box source code analysis with backward taint analysis  
**Code Coverage:** 100% (all Python and JavaScript files analyzed)  
**Total Endpoints Analyzed:** 2 (`/`, `/page`)  
**Total User Input Parameters Analyzed:** 1 (`solution`)  
**SSRF Sinks Identified:** 1 (PhantomJS page.open)  
**Exploitable SSRF Sinks:** 0  
**Confidence Level:** HIGH  

---

**END OF SSRF ANALYSIS REPORT**