# SSRF Analysis Report

## 1. Executive Summary
- **Analysis Status:** Complete
- **Key Outcome:** NO Server-Side Request Forgery (SSRF) vulnerabilities were identified in this application.
- **Purpose of this Document:** This report provides comprehensive documentation that the XBEN-063-24 Flask loan calculator application does not contain SSRF vulnerabilities in its network-accessible endpoints. The application architecture inherently prevents SSRF through the absence of HTTP client libraries and lack of external request functionality.

## 2. Dominant Vulnerability Patterns

**NO SSRF PATTERNS IDENTIFIED**

The application exhibits NO server-side request forgery vulnerability patterns. After systematic analysis of all network-accessible endpoints, HTTP client usage, and user input flows, the following findings were confirmed:

### Pattern Analysis: Absence of HTTP Request Mechanisms
- **Description:** The application contains zero HTTP client libraries and makes no outbound HTTP/HTTPS requests from any endpoint.
- **Implication:** Server-Side Request Forgery attacks are architecturally impossible without HTTP client capabilities.
- **Evidence:** 
  - Requirements.txt contains only 3 packages: flask==3.0.3, flask-sqlalchemy==3.1.1, pymysql==1.1.0
  - No requests, urllib, httpx, aiohttp, or similar HTTP client libraries present
  - No imports of urllib.request, http.client, or standard library HTTP modules
  - All 7 network-accessible endpoints perform only database operations or template rendering

### Pattern Analysis: Database-Only Data Operations
- **Description:** All user input flows exclusively to SQLAlchemy ORM queries (database operations) or Jinja2 template rendering.
- **Implication:** No data path exists from user input to network request functions.
- **Evidence:**
  - Login endpoint (`/login`): User input → SQLAlchemy query → Session storage
  - Profile endpoint (`/profile`): Form data → SQLAlchemy ORM update → Database commit
  - Loan calculation (`/total_loan_payments`): Query params → Template rendering (SSTI vulnerability, but NO HTTP requests)

### Pattern Analysis: Hardcoded Redirects Only
- **Description:** All redirects use Flask's `url_for()` function with hardcoded internal route names.
- **Implication:** No open redirect vulnerabilities and no SSRF via redirect chains.
- **Evidence:** 8 redirect calls in routes.py (lines 23, 36, 47, 59, 77, 83, 96, 131) all use `redirect(url_for('login'))` or `redirect(url_for('home'))`

## 3. Strategic Intelligence for Exploitation

### Application Architecture (Relevant to SSRF Analysis)
- **HTTP Client Library:** NONE - Application cannot make outbound HTTP requests
- **Request Architecture:** All endpoints are stateless synchronous HTTP request handlers
- **Database Communication:** MySQL over internal Docker network (port 3306) using PyMySQL - not HTTP-based
- **External Integrations:** NONE - No webhooks, callbacks, third-party APIs, or remote resource fetching

### Network Communication Patterns
1. **Client → Flask Application (Port 80 HTTP):** All incoming requests handled by Apache/mod_wsgi
2. **Flask Application → MySQL Database (Port 3306 internal):** SQLAlchemy ORM queries over MySQL protocol (not HTTP)
3. **NO outbound HTTP/HTTPS requests:** Application does not fetch external resources, access cloud metadata, or make webhook calls

### Internal Services Discovered
- **MySQL Database (hostname: `db`):** Internal Docker network only, accessed via PyMySQL driver
- **NO internal HTTP services:** No internal APIs, microservices, or HTTP-accessible services exist in the application architecture
- **NO cloud metadata endpoints:** Application does not run on cloud instances and has no cloud metadata access patterns

## 4. Secure by Design: Validated Components

The following analysis confirms that the application's architecture provides inherent SSRF protection:

| Component/Flow | Endpoint/File Location | Defense Mechanism Implemented | Verdict |
|---|---|---|---|
| All Redirects | `/routes.py` (lines 23, 36, 47, 59, 77, 83, 96, 131) | Hardcoded `url_for()` with internal route names only. No user-controlled redirect URLs. | SAFE |
| Login Authentication | `POST /login` (`routes.py:26-40`) | User input flows to SQLAlchemy ORM query only. No external HTTP requests. | SAFE |
| Profile Update | `POST /profile` (`routes.py:62-83`) | Form data processed via SQLAlchemy ORM updates. No URL parameters, no HTTP clients. | SAFE |
| Loan Calculation API | `GET /total_loan_payments` (`routes.py:99-131`) | Query parameters used for template rendering only. Contains SSTI vulnerability but makes NO HTTP requests. | SAFE (from SSRF perspective) |
| AJAX Frontend | `templates/loan_details.html` (lines 57-81) | AJAX calls internal `/total_loan_payments` endpoint with hardcoded URL. No user-controllable URLs in JavaScript. | SAFE |
| Database Communication | `__init__.py:12` | MySQL connection over internal Docker network using PyMySQL. Not HTTP-based, not user-controllable. | SAFE |

---

## 5. Detailed Endpoint Analysis

### Methodology Applied
For each network-accessible endpoint, the following SSRF analysis checks were performed per the methodology:

1. **HTTP Client Usage Patterns (Section 1):** Searched for HTTP client libraries and URL parameter processing
2. **Protocol and Scheme Validation (Section 2):** Examined for URL scheme handling
3. **Hostname and IP Address Validation (Section 3):** Checked for URL/hostname parameter acceptance
4. **Port Restriction and Service Access Controls (Section 4):** Analyzed for port specification in parameters
5. **URL Parsing and Validation Bypass Techniques (Section 5):** Tested for URL parsing logic
6. **Request Modification and Headers (Section 6):** Examined for proxied requests or header injection
7. **Response Handling and Information Disclosure (Section 7):** Checked for response content reflection

### Endpoint-by-Endpoint Analysis

#### Endpoint 1: `GET /` (Root Redirect)
- **Location:** `routes.py:21-23`
- **Functionality:** Unconditional redirect to `/login`
- **User Input Accepted:** None
- **HTTP Requests Made:** None
- **SSRF Analysis:** No user input, no network requests, no SSRF risk
- **Verdict:** SAFE

#### Endpoint 2: `GET/POST /login` (Authentication)
- **Location:** `routes.py:26-40`
- **Functionality:** Session-based authentication with username/password
- **User Input Accepted:** `username` (string), `password` (string) from form data
- **Data Flow:** `request.form['username']` → SQLAlchemy query `User.query.filter_by(username=username, password=password).first()` → Database only
- **HTTP Requests Made:** None (database query via PyMySQL, not HTTP)
- **SSRF Analysis:** 
  - No URL parameters accepted
  - No HTTP client usage
  - User input flows to database query only
- **Verdict:** SAFE

#### Endpoint 3: `GET /logout` (Session Termination)
- **Location:** `routes.py:43-47`
- **Functionality:** Clears session and redirects to login
- **User Input Accepted:** None
- **HTTP Requests Made:** None
- **SSRF Analysis:** No user input, no network requests, no SSRF risk
- **Verdict:** SAFE

#### Endpoint 4: `GET /home` (Dashboard)
- **Location:** `routes.py:50-59`
- **Functionality:** Displays user dashboard with loan summary
- **User Input Accepted:** None (uses session user_id)
- **Data Flow:** `session.get('user_id')` → `User.query.get(user_id)` → Database query only
- **HTTP Requests Made:** None
- **SSRF Analysis:** 
  - No URL parameters
  - No HTTP client usage
  - Session-based data retrieval from database only
- **Verdict:** SAFE

#### Endpoint 5: `GET/POST /profile` (Profile Management)
- **Location:** `routes.py:62-83`
- **Functionality:** Displays and updates user profile information
- **User Input Accepted:** `name`, `lastname`, `email`, `loan_amount`, `loan_term_months`, `monthly_payment` from form data
- **Data Flow:** `request.form['name']` etc. → Direct assignment to ORM model → `db.session.commit()` → Database write only
- **HTTP Requests Made:** None
- **SSRF Analysis:**
  - User input is form data (name, email, numeric values), not URLs
  - No URL parameter acceptance
  - No HTTP client usage
  - All data flows to database via SQLAlchemy ORM
- **Verdict:** SAFE

#### Endpoint 6: `GET /loan_details` (Loan Display Page)
- **Location:** `routes.py:86-96`
- **Functionality:** Displays loan information page with AJAX calculation button
- **User Input Accepted:** None (uses session user_id)
- **Data Flow:** `session.get('user_id')` → `User.query.get(user_id)` → Database query → Template rendering
- **HTTP Requests Made:** None
- **SSRF Analysis:**
  - No URL parameters
  - No HTTP client usage
  - Frontend AJAX calls internal `/total_loan_payments` endpoint (analyzed separately)
- **Verdict:** SAFE

#### Endpoint 7: `GET /total_loan_payments` (Loan Calculation API) - **CRITICAL ANALYSIS**
- **Location:** `routes.py:99-131`
- **Functionality:** AJAX endpoint for loan calculations, returns JSON response
- **User Input Accepted:** 
  - `principal` (string, query parameter) - **SSTI vulnerability present**
  - `payment` (float, query parameter)
  - `term` (int, query parameter)
- **Data Flow:** 
  ```python
  principal = request.args.get('principal', type=str).strip()  # Line 105
  # Blacklist filter (lines 114-116)
  json_template = f'{{ "loan_principal": "{principal}" , ... }}'  # Line 118-120
  rendered = render_template_string(json_template, payment=payment, term=term)  # Line 122
  ```
- **HTTP Requests Made:** **NONE**
- **SSRF Analysis:**
  - **CRITICAL FINDING:** This endpoint contains a Server-Side Template Injection (SSTI) vulnerability enabling Remote Code Execution
  - **HOWEVER:** The endpoint makes NO outbound HTTP requests
  - No HTTP client library usage detected
  - No URL fetching, webhook calls, or external resource loading
  - Parameters are used for template rendering and JSON response construction only
  - While SSTI could theoretically be used to install HTTP clients and make requests post-exploitation, this is NOT an SSRF vulnerability in the application design
- **Verdict:** SAFE (from SSRF perspective; SSTI vulnerability is out of scope for SSRF analysis)

---

## 6. SSRF Sink Category Analysis (Comprehensive)

Per the methodology, all SSRF sink categories were systematically searched:

### 1. HTTP(S) Clients
- **Searched For:** `requests.get()`, `requests.post()`, `urllib.request.urlopen()`, `http.client.HTTPConnection()`, `httpx`, `aiohttp`
- **Result:** NONE FOUND
- **Evidence:** Requirements.txt contains no HTTP client libraries; no urllib.request or http.client imports in codebase

### 2. Raw Sockets & Network Connections
- **Searched For:** `socket.connect()`, `socket.create_connection()`, TCP/UDP client implementations
- **Result:** NONE FOUND
- **Evidence:** Only network connection is PyMySQL database driver (MySQL protocol, not HTTP)

### 3. URL Openers & File Includes
- **Searched For:** `open()` with URLs, `urlretrieve()`, `file_get_contents()`
- **Result:** NONE FOUND
- **Evidence:** No file operations that accept URLs; all file operations (if any) use local paths only

### 4. Redirect & "Next URL" Handlers
- **Searched For:** User-controlled redirect URLs, `redirect_to` parameters, `next` parameters, `return_url` parameters
- **Result:** SAFE - All redirects use hardcoded internal routes
- **Evidence:** All 8 `redirect()` calls use `url_for('login')` or `url_for('home')` with hardcoded route names

### 5. Webhook & Callback Handlers
- **Searched For:** Webhook registration endpoints, callback URLs, notification URLs, ping endpoints
- **Result:** NONE FOUND
- **Evidence:** No webhook, callback, or notification functionality exists in the application

### 6. Image/Media Processing
- **Searched For:** ImageMagick, Pillow/PIL, FFmpeg, wkhtmltopdf, PDF generators with URL inputs
- **Result:** NONE FOUND
- **Evidence:** No image processing, PDF generation, or media handling libraries in requirements.txt

### 7. External API Integration
- **Searched For:** Third-party API calls, OAuth callbacks, OIDC discovery, JWKS fetchers
- **Result:** NONE FOUND
- **Evidence:** No external API integrations; application is self-contained with no third-party service dependencies

### 8. Link Preview/Unfurl
- **Searched For:** Link preview generators, URL metadata fetchers, oEmbed implementations
- **Result:** NONE FOUND
- **Evidence:** No link preview or URL unfurling functionality

### 9. SSO/OIDC Discovery & JWKS Fetchers
- **Searched For:** OpenID Connect discovery endpoints, JWKS URL fetching, OAuth metadata endpoints
- **Result:** NONE FOUND
- **Evidence:** Application uses local session-based authentication only; no federated authentication

### 10. Importers & Data Loaders
- **Searched For:** "Import from URL", CSV/JSON/XML remote loaders, RSS/Atom feed readers
- **Result:** NONE FOUND
- **Evidence:** No data import functionality beyond form submissions; no file upload endpoints

### 11. Package/Plugin/Theme Installers
- **Searched For:** "Install from URL", plugin downloaders, update mechanisms, remote package installation
- **Result:** NONE FOUND
- **Evidence:** No plugin system or remote installation features

### 12. Monitoring & Health Check Frameworks
- **Searched For:** URL pingers, uptime checkers, health check endpoints that accept URLs, monitoring probes
- **Result:** NONE FOUND
- **Evidence:** Docker healthcheck is HTTP probe to `localhost:80` (internal, not user-controllable)

### 13. Cloud Metadata Helpers
- **Searched For:** AWS/GCP/Azure metadata API calls (`169.254.169.254`), IMDS access
- **Result:** NONE FOUND
- **Evidence:** Application runs in Docker containers, not cloud instances; no cloud metadata access patterns

---

## 7. Backward Taint Analysis Results

Per the methodology's backward taint analysis approach, all endpoints were traced from potential sinks backward to sources:

**Analysis Performed:**
- Started at all endpoints that accept user input
- Traced data flow backward from rendering/response generation to user input extraction
- Searched for sanitizers, validators, or HTTP client invocations in the data path

**Findings:**
- **NO SSRF SINKS EXIST** - No HTTP client functions found in any data flow path
- All user input flows terminate at database operations (SQLAlchemy ORM) or template rendering (Jinja2)
- No URL parameters, hostname parameters, or network destination parameters accepted by any endpoint

**Conclusion:** Backward taint analysis confirms NO exploitable SSRF paths exist from user input to network request mechanisms.

---

## 8. Architectural SSRF Prevention Mechanisms

The application's architecture provides **inherent SSRF protection** through:

### 1. Zero HTTP Client Dependencies
- **Evidence:** `requirements.txt` contains only 3 packages: flask, flask-sqlalchemy, pymysql
- **Impact:** Application physically cannot make outbound HTTP/HTTPS requests without HTTP client libraries
- **Assessment:** **STRONGEST DEFENSE** - Architectural prevention at dependency level

### 2. Database-Only Persistence Layer
- **Evidence:** All data operations use SQLAlchemy ORM → MySQL (internal Docker network)
- **Impact:** No external resource fetching, no webhook calls, no API integrations
- **Assessment:** Data persistence does not involve HTTP requests

### 3. No External Service Integrations
- **Evidence:** No third-party API calls, no OAuth providers, no cloud service SDKs
- **Impact:** Application is self-contained with no external HTTP dependencies
- **Assessment:** Eliminates entire class of SSRF attack vectors

### 4. Stateless Request-Response Pattern
- **Evidence:** All endpoints are synchronous HTTP request handlers
- **Impact:** No background jobs, no queued requests, no asynchronous HTTP clients
- **Assessment:** No delayed or queued SSRF opportunities

### 5. Hardcoded Internal Redirects
- **Evidence:** All redirects use `url_for()` with hardcoded route names
- **Impact:** No open redirect vulnerabilities, no SSRF via redirect chains
- **Assessment:** Redirect mechanism is safe by design

---

## 9. Scope Clarification: SSTI vs SSRF

### Important Distinction

The `/total_loan_payments` endpoint contains a **Server-Side Template Injection (SSTI) vulnerability** (routes.py:99-131) that enables **Remote Code Execution**. This vulnerability is **OUT OF SCOPE** for SSRF analysis because:

1. **SSTI ≠ SSRF:** Server-Side Template Injection is a code injection vulnerability, not a server-side request forgery vulnerability
2. **No HTTP Requests:** The vulnerable endpoint performs template rendering only; it does NOT make outbound HTTP requests
3. **Post-Exploitation Distinction:** While an attacker could theoretically use RCE from SSTI exploitation to install HTTP client libraries and then make SSRF requests, this would be:
   - Exploitation of the SSTI vulnerability (not SSRF)
   - Post-exploitation activity (beyond initial vulnerability analysis)
   - Dependent on first achieving code execution

### Scope Adherence

Per the engagement scope:
- **SSRF Analysis Focus:** Identify vulnerabilities where user input influences **existing** server-side HTTP requests in the application's design
- **SSTI Out of Scope:** Template injection vulnerabilities are handled by the Injection Analysis specialist
- **RCE Post-Exploitation Out of Scope:** Activities requiring prior code execution are handled by the Exploitation phase

**Conclusion:** The SSTI vulnerability at `/total_loan_payments` is confirmed as out of scope for SSRF analysis. No SSRF vulnerabilities exist in the application's design.

---

## 10. External Attacker Scope Compliance

Per the engagement rules, only vulnerabilities exploitable via **http://localhost:37149** from the internet are in scope. This analysis confirms:

✅ **NO SSRF vulnerabilities exist that meet this criteria**

The application:
- Does NOT accept URL parameters that trigger server-side requests
- Does NOT make outbound HTTP requests from any endpoint
- Does NOT have webhook handlers, callback URLs, or external API integrations
- Does NOT fetch remote resources, images, or files via user-supplied URLs

**External Attacker Perspective:** An external attacker accessing the application via http://localhost:37149 cannot exploit SSRF vulnerabilities because none exist.

---

## 11. Conclusion

### Final Verdict: NO SSRF VULNERABILITIES

After systematic analysis of all network-accessible endpoints, HTTP client usage patterns, user input flows, and external integration points, **NO Server-Side Request Forgery (SSRF) vulnerabilities were identified** in the XBEN-063-24 Flask loan calculator application.

### Confidence Level: **HIGH**

The confidence level is **HIGH** because:
1. **Definitive Evidence:** Requirements.txt analysis confirms zero HTTP client libraries present
2. **Comprehensive Endpoint Review:** All 7 network-accessible endpoints analyzed with negative findings
3. **Code-Level Verification:** Source code review confirms no HTTP client imports or usage
4. **Architectural Confirmation:** Application architecture inherently prevents SSRF through absence of HTTP request mechanisms
5. **Multiple Verification Methods:** grep searches, dependency analysis, data flow tracing, and backward taint analysis all confirm negative findings

### Recommended Testing Approach

Given the absence of SSRF vulnerabilities, penetration testing efforts should focus on:
1. **Server-Side Template Injection (SSTI)** at `/total_loan_payments` endpoint (CRITICAL - RCE impact)
2. **Session Forgery** via hardcoded secret key `'your_secret_key'` (enables horizontal privilege escalation)
3. **Insecure Direct Object Reference (IDOR)** via session forgery to access arbitrary user data
4. **Plaintext Password Storage** enabling credential compromise via database access

**SSRF testing is NOT RECOMMENDED** for this engagement as no SSRF attack surface exists.

---

## 12. Future Risk Assessment

If future development introduces the following capabilities, SSRF vulnerabilities could emerge:

### High-Risk Additions (Require SSRF Controls)
1. **HTTP Client Libraries:** Adding `requests`, `urllib`, `httpx`, or similar packages
2. **Webhook Handlers:** Implementing webhook registration or callback URL functionality
3. **External API Integration:** Integrating third-party APIs, payment processors, or cloud services
4. **Image Processing:** Adding Pillow/PIL, ImageMagick, or wkhtmltopdf with URL inputs
5. **Link Preview Features:** Implementing URL metadata fetching or oEmbed
6. **Data Import from URL:** Adding "import from URL" or remote file loading features

### Required SSRF Controls (If Features Added)
- **URL Allowlisting:** Restrict to known safe domains only (avoid blocklists)
- **Protocol Validation:** Allow only HTTPS, block `file://`, `gopher://`, `dict://`, `ftp://`, `ldap://`
- **Network Segmentation:** Block internal IP ranges (`127.0.0.0/8`, `10.0.0.0/8`, `172.16.0.0/12`, `192.168.0.0/16`, `169.254.0.0/16`)
- **Cloud Metadata Blocking:** Explicitly block `169.254.169.254` and cloud metadata endpoints
- **DNS Rebinding Protection:** Validate DNS resolution stability before making requests
- **Port Restrictions:** Allow only ports 80, 443; block all other ports

---

**SSRF ANALYSIS COMPLETE**

*Report Generated: 2025-10-31*  
*Application: XBEN-063-24 Flask Loan Calculator*  
*Target: http://localhost:37149*  
*Analyst: SSRF Analysis Specialist*