# SSRF Analysis Report

## 1. Executive Summary
- **Analysis Status:** Complete
- **Key Outcome:** After systematic analysis of all application endpoints, code paths, and dependencies, **ZERO Server-Side Request Forgery (SSRF) vulnerabilities were identified**. The application does not contain any functionality that makes outbound HTTP requests or processes user-supplied URLs.
- **Purpose of this Document:** This report provides comprehensive evidence that the Flask loan calculator application is immune to SSRF attacks due to its architectural design. The application contains no HTTP client libraries, no URL processing logic, and no external service integrations that could be exploited to force the server to make unintended requests.

## 2. Dominant Vulnerability Patterns

### Pattern 1: Complete Absence of Outbound Request Functionality
- **Description:** The most significant finding is that this application fundamentally lacks the capability to make outbound HTTP requests. The application architecture is completely self-contained, with no HTTP client libraries, no URL fetching mechanisms, and no external service integrations.
- **Implication:** SSRF vulnerabilities require the application to have server-side request-making capabilities. Without such functionality, SSRF attacks are architecturally impossible.
- **Evidence:**
  - No HTTP client libraries in dependencies (requirements.txt contains only: flask, flask_sqlalchemy, pymysql)
  - No imports of requests, urllib, urllib3, httpx, aiohttp, or http.client in any Python file
  - No socket programming or raw network operations
  - All 7 endpoints analyzed (/, /login, /logout, /home, /profile, /loan_details, /total_loan_payments) perform only internal operations

### Pattern 2: Secure Internal-Only Redirect Pattern
- **Description:** All redirect operations in the application use Flask's `url_for()` function with hardcoded internal route names. No redirects accept user-supplied URLs.
- **Implication:** Open redirect vulnerabilities (which can sometimes chain with SSRF) are prevented by the strict use of internal route references.
- **Evidence:**
  - 8 redirect operations found in routes.py (Lines 18, 30, 40, 51, 68, 74, 86, 112)
  - All use pattern: `redirect(url_for('route_name'))`
  - No `next`, `return_to`, `redirect_to`, or `callback` parameters accepted
  - No URL parsing or validation logic exists (because no URLs are processed)

## 3. Strategic Intelligence for Exploitation

**Application Architecture:**
- **Framework:** Python Flask with Flask-SQLAlchemy ORM
- **Network Scope:** Self-contained application with no external dependencies
- **Request Flow:** Browser → Apache (mod_wsgi) → Flask → MySQL (internal Docker network)
- **Outbound Communication:** NONE - Application makes zero external HTTP requests

**HTTP Client Library:** NONE DETECTED
- No requests, urllib, httpx, aiohttp, or any HTTP client library present
- requirements.txt contains only: flask, flask_sqlalchemy, pymysql

**Request Architecture:**
- All 7 HTTP endpoints process user input internally
- Database operations use SQLAlchemy ORM (no raw SQL that could fetch external data)
- Template rendering uses Jinja2 (no URL fetching in templates)
- Static files served locally from /static/ directory

**Internal Services:** 
- MySQL 5.7.15 database (internal to Docker network, port 3306)
- No other internal services, microservices, or APIs detected
- No service mesh, API gateway, or internal proxies

**Network Topology:**
- External access: http://localhost:46413 (dynamically mapped to internal port 80)
- Internal Docker network: web container (Flask) ↔ db container (MySQL)
- No outbound internet connectivity from application containers

## 4. Secure by Design: Validated Components

These components were analyzed and found to have robust defenses or complete absence of SSRF attack surface. They are **NOT VULNERABLE** to SSRF and require no further testing.

| Component/Flow | Endpoint/File Location | Defense Mechanism Implemented | Verdict |
|---|---|---|---|
| Authentication System | `/login` - routes.py:20-34 | No external URL processing; uses internal database queries only | SAFE - NO SSRF SURFACE |
| Profile Management | `/profile` - routes.py:53-74 | Accepts only text/numeric input; no URL parameters; no external requests | SAFE - NO SSRF SURFACE |
| Loan Calculator | `/total_loan_payments` - routes.py:88-112 | Accepts calculation parameters (principal, payment, term); no URL processing | SAFE - NO SSRF SURFACE |
| User Dashboard | `/home` - routes.py:42-51 | Display-only endpoint; no user input processing | SAFE - NO SSRF SURFACE |
| Loan Details Display | `/loan_details` - routes.py:76-86 | Display-only endpoint; no user input processing | SAFE - NO SSRF SURFACE |
| Session Management | Flask session cookies | Client-side signed cookies; no URL tokens or callback URLs | SAFE - NO SSRF SURFACE |
| Database Layer | MySQL via SQLAlchemy ORM | All queries parameterized; no raw SQL with URLs; database URI hardcoded | SAFE - NO SSRF SURFACE |
| Redirect Logic | All endpoints using redirect() | Uses url_for() with hardcoded route names exclusively; no user-supplied URLs | SAFE - PROPER IMPLEMENTATION |
| Static File Serving | Apache /static/* path | Serves local filesystem files only; no URL-based file fetching | SAFE - NO SSRF SURFACE |
| Template Rendering | Jinja2 templates | All URLs generated via url_for(); no external resource includes | SAFE - NO SSRF SURFACE |

## 5. Comprehensive SSRF Sink Analysis

### 5.1 HTTP(S) Client Analysis

**Methodology:** Searched all Python source files for HTTP client library imports and usage.

**Libraries Checked:**
- ❌ `requests` - Not found in imports or requirements.txt
- ❌ `urllib` / `urllib.request` / `urllib.parse` / `urllib3` - Not found
- ❌ `httpx` - Not found
- ❌ `aiohttp` - Not found
- ❌ `http.client` / `httplib` - Not found
- ❌ `pycurl` - Not found
- ❌ `tornado.httpclient` - Not found

**Files Analyzed:**
- __init__.py - Imports: Flask, SQLAlchemy, db, User, routes
- routes.py - Imports: Flask components (render_template, redirect, url_for, request, session, Response)
- models.py - Imports: SQLAlchemy, db
- db.py - Imports: SQLAlchemy
- run.py - Imports: app
- loan_calculator.wsgi - Imports: sys, app

**Verdict:** NO HTTP CLIENT LIBRARIES PRESENT

### 5.2 Protocol and Scheme Validation

**Analysis:** Since the application does not process URLs or make outbound requests, protocol validation is not applicable.

**Redirect Analysis:**
All redirect operations examined:
```python
# File: routes.py
redirect(url_for('login'))    # Lines 18, 40, 51, 74, 86, 112
redirect(url_for('home'))     # Lines 30, 68
```

**Verdict:** NO URL SCHEME PROCESSING - Only internal route names used

### 5.3 Hostname and IP Address Validation

**Analysis:** No hostname or IP address validation logic exists because no URLs are processed.

**Database Connection String:**
```python
# __init__.py:11 - Hardcoded, not user-controllable
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:loan_calculator@db/database'
```

**Verdict:** NO HOSTNAME VALIDATION NEEDED - No user-supplied URLs accepted

### 5.4 Port Restriction Analysis

**Analysis:** No port restriction logic exists because no network connections are initiated based on user input.

**Fixed Ports:**
- External: 46413 (Docker port mapping)
- Internal web: 80 (Apache)
- Internal database: 3306 (MySQL)

All port configurations are hardcoded in docker-compose.yml and not influenced by user input.

**Verdict:** NO PORT VALIDATION NEEDED - No dynamic connections made

### 5.5 URL Parsing and Validation

**Analysis:** No URL parsing libraries or validation functions detected.

**Checked Functions:**
- ❌ `urllib.parse.urlparse()` - Not found
- ❌ `urllib.parse.urljoin()` - Not found
- ❌ `validators.url()` - Not found
- ❌ Custom URL validation functions - Not found

**User Input Processing:**
All user inputs are processed as:
- Text strings (name, lastname, email)
- Plaintext passwords (username, password)
- Numeric values (loan_amount, loan_term_months, monthly_payment, principal, payment, term)

None are treated as URLs or parsed for network locations.

**Verdict:** NO URL PARSING PRESENT - Application does not handle URLs

### 5.6 Request Modification and Headers

**Analysis:** No outbound request modification logic exists because no outbound requests are made.

**Header Processing:**
- Application reads standard Flask request headers (request.form, request.args)
- Does not read or process: X-Forwarded-For, X-Original-URL, custom headers for URL forwarding
- Does not construct or modify outbound HTTP headers

**Verdict:** NO REQUEST MODIFICATION - No outbound requests to modify

### 5.7 Response Handling and Information Disclosure

**Analysis:** Since no outbound requests are made, no external response handling occurs.

**Internal Responses:**
- Database query results (user profiles, loan data)
- Template-rendered HTML pages
- JSON response from /total_loan_payments endpoint

All responses contain only internally-generated data, never external content fetched via HTTP.

**Verdict:** NO EXTERNAL RESPONSE HANDLING - Only internal data returned

## 6. Endpoint-by-Endpoint Analysis

### 6.1 GET / (Root)
- **File:** routes.py:16-18
- **Functionality:** Redirects to /login
- **User Input:** None
- **Outbound Requests:** None
- **SSRF Risk:** None
- **Verdict:** SAFE

### 6.2 GET/POST /login (Authentication)
- **File:** routes.py:20-34
- **Functionality:** Authenticates users via username/password
- **User Input:** username, password (form fields)
- **Input Usage:** Database query: `User.query.filter_by(username=username, password=password).first()`
- **Outbound Requests:** None
- **SSRF Risk:** None (SQLAlchemy ORM parameterizes query)
- **Verdict:** SAFE

### 6.3 GET /logout
- **File:** routes.py:36-40
- **Functionality:** Clears session and redirects to login
- **User Input:** None
- **Outbound Requests:** None
- **SSRF Risk:** None
- **Verdict:** SAFE

### 6.4 GET /home (Dashboard)
- **File:** routes.py:42-51
- **Functionality:** Displays user dashboard
- **User Input:** None (reads from session)
- **Outbound Requests:** None
- **SSRF Risk:** None
- **Verdict:** SAFE

### 6.5 GET/POST /profile (Profile Management)
- **File:** routes.py:53-74
- **Functionality:** Displays and updates user profile
- **User Input:** name, lastname, email, loan_amount, loan_term_months, monthly_payment (form fields)
- **Input Usage:** ORM attribute assignment and database commit
- **Outbound Requests:** None
- **SSRF Risk:** None (no URL parameters, no external requests)
- **Verdict:** SAFE

### 6.6 GET /loan_details
- **File:** routes.py:76-86
- **Functionality:** Displays loan information summary
- **User Input:** None (reads from session)
- **Outbound Requests:** None
- **SSRF Risk:** None
- **Verdict:** SAFE

### 6.7 GET /total_loan_payments (Loan Calculator)
- **File:** routes.py:88-112
- **Functionality:** Calculates total loan payments
- **User Input:** principal, payment, term (query parameters)
- **Input Usage:** Mathematical calculation and template rendering
- **Outbound Requests:** None
- **SSRF Risk:** None (parameters used for calculation only, not for URL construction)
- **Note:** This endpoint has a Server-Side Template Injection (SSTI) vulnerability (principal parameter), but this is NOT an SSRF vulnerability
- **Verdict:** SAFE FROM SSRF

## 7. False Positive Exclusions

### 7.1 Database Connections (Not SSRF)
**Observation:** MySQL database connection via SQLAlchemy

**Analysis:**
- Connection string: `mysql+pymysql://root:loan_calculator@db/database` (hardcoded in __init__.py:11)
- Not user-controllable
- Database is internal to Docker network
- No user input influences connection parameters

**Verdict:** NOT AN SSRF VECTOR

### 7.2 Template Includes (Not SSRF)
**Observation:** Jinja2 templates use `{% extends %}` and `{% include %}` directives

**Analysis:**
- All template references are relative file paths (e.g., 'base.html')
- No URL schemes in template includes
- No user input influences template selection

**Verdict:** NOT AN SSRF VECTOR

### 7.3 Static File Serving (Not SSRF)
**Observation:** Apache serves static files from /static/ directory

**Analysis:**
- Files served from local filesystem: `/var/www/loan_calculator/app/static/`
- No URL-based file fetching
- Static file URLs generated via: `url_for('static', filename='...')`

**Verdict:** NOT AN SSRF VECTOR

### 7.4 Client-Side AJAX (Not SSRF)
**Observation:** loan_details.html contains jQuery AJAX request (lines 56-69)

**Analysis:**
```javascript
$.ajax({
    type: "GET",
    url: "{{ url_for('total_loan_payments') }}",
    data: data,
    success: function(data) { ... }
});
```
- This is a **client-side** request from the browser to the application's own endpoint
- The URL is generated server-side via `url_for()` with no user input
- The request originates from the browser, not from the server
- This does NOT constitute server-side request forgery

**Verdict:** NOT AN SSRF VECTOR

## 8. Security Posture Summary

### SSRF-Related Security Strengths
1. **No HTTP Client Dependencies:** Application deliberately excludes all HTTP client libraries
2. **Hardcoded Redirects:** All redirects use internal route names via `url_for()`
3. **Self-Contained Architecture:** No external service integrations or API dependencies
4. **Parameterized Queries:** SQLAlchemy ORM prevents SQL injection vectors that could fetch external data
5. **Local Static Files:** All static assets served from local filesystem

### Why This Application is Immune to SSRF
1. **No Outbound Capability:** The application fundamentally lacks the ability to make HTTP requests
2. **No URL Processing:** No code accepts, parses, validates, or uses URLs from user input
3. **No External Integrations:** No webhooks, APIs, OAuth callbacks, or external service calls
4. **Closed Network Model:** Application only communicates with internal MySQL database on Docker network

### Architecture Advantages
- Simplified attack surface (no external API attack vectors)
- Reduced data exfiltration risk (no outbound channels)
- No cloud metadata exposure risk (no internal AWS/Azure/GCP endpoint access capability)
- No internal service discovery risk (no ability to probe internal networks)

### Architecture Limitations
- Limited functionality (no external API integrations, payment processors, analytics)
- No OAuth/SSO capability (could improve security if implemented correctly)
- No external monitoring/logging services

## 9. Testing Methodology Employed

### Static Code Analysis
1. **Dependency Analysis:** Examined requirements.txt and all import statements
2. **Library Usage Search:** Searched for HTTP client, socket, and URL processing functions
3. **Redirect Logic Review:** Analyzed all redirect() calls and URL generation
4. **Input Flow Tracing:** Traced all user inputs to their consumption points
5. **Template Analysis:** Reviewed all Jinja2 templates for URL processing

### Dynamic Analysis (Not Required)
Dynamic testing was deemed unnecessary because:
- Static analysis conclusively proved absence of HTTP client capabilities
- No code paths exist that could make outbound requests
- No endpoints accept URL parameters

### Tools and Techniques
- Manual code review of all Python source files
- Grep-based pattern matching for HTTP libraries and functions
- Dependency tree analysis
- Data flow analysis from request inputs to outputs

## 10. Recommendations

### For This Application
Since no SSRF vulnerabilities exist, no SSRF-specific remediation is required. The application's architecture inherently prevents SSRF attacks.

### If External Services Were Added (Future Considerations)
If the application were to be extended with outbound request capabilities, implement:

1. **URL Allowlisting:** Maintain strict allowlist of permitted external domains
2. **Protocol Restrictions:** Only allow https:// (never file://, gopher://, dict://)
3. **IP Blocklisting:** Block private 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)
4. **Cloud Metadata Protection:** Explicitly block 169.254.169.254 and metadata.google.internal
5. **Request Timeouts:** Implement short timeouts to prevent resource exhaustion
6. **Response Size Limits:** Limit response body size to prevent memory exhaustion
7. **Disable Redirects:** Prevent HTTP clients from following redirects automatically
8. **Network Segmentation:** Run application in isolated network with egress filtering

### General Security Observations (Non-SSRF)
While outside the scope of SSRF analysis, note:
- SSTI vulnerability in /total_loan_payments (principal parameter) - Critical severity
- Plaintext password storage - Critical security issue
- Hardcoded Flask secret key - Session forgery risk
- Missing CSRF protection - State modification attacks possible
- No HTTPS/TLS - Credentials transmitted in cleartext

## 11. Conclusion

**SSRF Vulnerability Count: 0**

After comprehensive white-box analysis of all application components, endpoints, dependencies, and code paths, I can conclusively state that this Flask loan calculator application contains **ZERO Server-Side Request Forgery (SSRF) vulnerabilities**.

The application's self-contained architecture, complete absence of HTTP client libraries, and lack of URL processing functionality make SSRF attacks architecturally impossible. All redirect operations use secure internal route references, and no endpoints accept or process external URLs.

**External Exploitability: N/A** - No SSRF vulnerabilities exist to exploit

**Recommended Next Steps:**
1. No SSRF exploitation phase required
2. Focus security testing efforts on identified vulnerabilities: SSTI (Critical), Authentication Issues (High), Session Management (High)

**Analysis Confidence: 100%** - Static code analysis provides definitive proof of absence of SSRF attack surface

---

**Report Generated:** 2025-10-29  
**Analysis Method:** Comprehensive White-Box Static Code Analysis  
**Files Analyzed:** 7 Python files, 1 requirements file, 4 HTML templates  
**Endpoints Analyzed:** 7 HTTP endpoints  
**SSRF Sinks Identified:** 0  
**Exploitable SSRF Vulnerabilities:** 0