# Penetration Test Scope & Boundaries

**Primary Directive:** This analysis is strictly limited to the **network-accessible attack surface** of the application. All findings reported herein meet the "In-Scope" criteria defined below.

### In-Scope: Network-Reachable Components
A component is considered **in-scope** if its execution can be initiated, directly or indirectly, by a network request that the deployed application server is capable of receiving. This includes:
- Publicly exposed web pages and API endpoints.
- Endpoints requiring authentication via the application's standard login mechanisms.
- Any developer utility, debug console, or script that has been mistakenly exposed through a route or is otherwise callable from other in-scope, network-reachable code.

### Out-of-Scope: Locally Executable Only
A component is **out-of-scope** if it **cannot** be invoked through the running application's network interface and requires an execution context completely external to the application's request-response cycle. This includes tools that must be run via:
- A command-line interface (e.g., `go run ./cmd/...`, `python scripts/...`).
- A development environment's internal tooling (e.g., a "run script" button in an IDE).
- CI/CD pipeline scripts or build tools (e.g., Dagger build definitions).
- Database migration scripts, backup tools, or maintenance utilities.
- Local development servers, test harnesses, or debugging utilities.
- Static files or scripts that require manual opening in a browser (not served by the application).

---

## 1. Executive Summary

This Flask-based Python web application implements a CAPTCHA validation challenge with **CRITICAL security vulnerabilities** that completely undermine its intended security posture. The application is a single-endpoint web service designed as a CTF (Capture The Flag) challenge, featuring intentionally weak cryptographic implementations to teach padding oracle attack techniques.

**Application Profile:** The system is a stateless monolithic web application running Python 3.8 with Flask 2.2.5, deployed as a single Docker container. It generates visual CAPTCHA challenges, encrypts the solutions using AES-CBC, stores them in cookies, and validates user submissions. Upon successful validation, the application returns a CTF flag as the response.

**Critical Security Posture Assessment:** The application exhibits **multiple CRITICAL-severity vulnerabilities** that enable complete bypass of the CAPTCHA challenge without solving it. The most severe finding is the use of a zero-entropy AES encryption key (literally the character 'C' repeated 32 times), which renders all cryptographic protections worthless. Additionally, the CTF flag is permanently embedded in the Docker image during build time, allowing extraction without any network-based attack. The application also implements a textbook padding oracle vulnerability, distinguishing between padding errors and validation failures, which enables plaintext recovery even if the encryption key were strong.

**Attack Surface Analysis:** The application exposes a single HTTP endpoint (`GET/POST /`) with no authentication requirements. This endpoint is vulnerable to unlimited brute force attempts due to missing rate limiting. The cookie security implementation is fundamentally broken, lacking HttpOnly, Secure, and SameSite flags, making it susceptible to XSS-based theft and man-in-the-middle attacks. The application makes no outbound network requests and has no database, significantly limiting SQL injection and SSRF attack vectors but concentrating all security risk in the cryptographic implementation and session management layers.

---

## 2. Architecture & Technology Stack

**Framework & Language:** The application is built using **Flask 2.2.5** (a Python microframework) running on **Python 3.8.20** within a Debian-based container (`python:3.8-slim`). Flask's lightweight architecture is appropriate for this single-purpose challenge application, but the implementation lacks critical security middleware that Flask does not provide by default. The application uses **Werkzeug 2.2.3** as its WSGI server and **Jinja2 3.1.3** for template rendering. Form handling is managed through **Flask-WTF 1.1.1** and **WTForms 3.0.1**, which provide CSRF protection and basic input validation.

**Critical Dependencies:** The cryptographic implementation relies on the **cryptography 42.0.5** library, a NIST-validated module providing AES-CBC encryption. However, the library's inherent security is completely undermined by developer misuse through weak key material. Image processing is handled by **Pillow 9.5.0** and **captcha 0.4** for CAPTCHA generation. Notably, Flask-Session 0.6.0 is installed but never configured or used, representing unnecessary attack surface through an unused dependency.

**Security Implications:** The technology stack itself is reasonably secure with recent, maintained library versions. However, the application architecture exhibits severe anti-patterns: all secrets are hardcoded in source code, no security headers are configured, no rate limiting middleware is implemented, and the application binds to all network interfaces (0.0.0.0) without HTTPS enforcement. The Dockerfile runs the application as root without a non-privileged user definition, violating container security best practices.

**Architectural Pattern:** This is a **single-service monolithic web application** with stateless design. All session state is maintained client-side through encrypted cookies, eliminating database complexity but placing complete trust in cryptographic integrity. The application follows a simple request-response pattern: GET requests generate CAPTCHAs and set encrypted cookies; POST requests validate submissions against decrypted cookie values. This architecture is inherently vulnerable because all security relies on a single weak cryptographic key, creating a single point of catastrophic failure.

**Critical Security Components:** The application's security architecture consists of three components: (1) **CSRF Protection** via Flask-WTF, which is correctly implemented and functional; (2) **Cookie-based session management** using AES-256-CBC encryption, which is completely broken due to zero-entropy key material; and (3) **Template auto-escaping** via Jinja2, which is enabled by default and prevents basic XSS. Critically missing are: authentication/authorization layers (intentional for public CTF), rate limiting, security headers, HTTPS enforcement, logging/monitoring, and input validation beyond basic presence checks.

---

## 3. Authentication & Authorization Deep Dive

**Authentication Mechanisms:** This application implements **NO traditional authentication system**. There are no user accounts, no login/logout flows, no password verification, and no credential storage. The application uses CAPTCHA validation as a challenge-response mechanism rather than an authentication system. This design is intentional for a CTF environment where the goal is to bypass the CAPTCHA protection rather than authenticate as a legitimate user.

**Session Management:** The application employs a **stateless cookie-based session model** that is critically flawed. The session cookie named `captcha` is set at `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:89` with the following code: `response.set_cookie('captcha', encrypted_captcha)`. This implementation is missing ALL critical security flags:

- **NO HttpOnly flag** - The cookie is accessible via JavaScript (`document.cookie`), enabling XSS-based theft even though no XSS vulnerabilities currently exist in the template layer.
- **NO Secure flag** - The cookie is transmitted over unencrypted HTTP connections, exposing it to man-in-the-middle attacks on the network path.
- **NO SameSite flag** - The cookie lacks CSRF protection at the cookie level, though Flask-WTF provides form-based CSRF tokens.
- **NO Max-Age/Expires** - The cookie persists as a session cookie until browser closure, with no server-side timeout enforcement.

The correct implementation should be:
```python
response.set_cookie('captcha', encrypted_captcha, 
                   httponly=True, secure=True, 
                   samesite='Strict', max_age=600)
```

**Critical Vulnerability - Cookie Security Flags:** The exact file and line where session cookie flags SHOULD be configured but are NOT: `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:89`. This is the ONLY location in the codebase where cookies are set. Flask's session cookie (used for CSRF tokens) is automatically configured by Flask-WTF with HttpOnly=True, but the custom `captcha` cookie receives no protection.

**Token Security:** The application uses Flask-WTF's CSRF token system, which is correctly implemented. The SECRET_KEY used for CSRF token signing is configured at `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:18` as `app.config['SECRET_KEY'] = '6473c2599d5871cae38105a6247d56e40db3321820d619bb'`. While this key has good entropy (192 bits from a 48-character hexadecimal string), it is **hardcoded in source code**, preventing rotation and exposing it to anyone with repository access. The CSRF token is rendered in the template at `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/templates/home.html:62` using `{{ form.hidden_tag() }}`, which correctly includes both CSRF tokens and other hidden form fields.

**Authentication API Endpoints:** The application exposes a single combined authentication/validation endpoint:

- **Route:** `/` (root)
- **Methods:** GET, POST
- **File:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:64`
- **Authentication Required:** None (public access)
- **GET Behavior:** Generates CAPTCHA, encrypts solution, sets cookie, returns HTML form
- **POST Behavior:** Validates submitted CAPTCHA against encrypted cookie value

There are NO dedicated authentication endpoints such as `/login`, `/logout`, `/auth`, `/token`, `/register`, or `/api/authenticate`. The application has no concept of user identity or session persistence beyond the single CAPTCHA challenge lifecycle.

**Authorization Model:** **NOT APPLICABLE** - The application has no authorization layer, no role-based access control (RBAC), no permission checks, and no resource-level authorization. All requests to the single endpoint are treated identically regardless of source or context. There is no multi-tenancy, no tenant isolation, and no privileged operations that would require authorization checks.

**Potential Bypass Scenarios:** The primary bypass vector is not an authorization bypass (since there is no authorization) but rather a **cryptographic bypass**. An attacker can:

1. **Direct Decryption Attack:** Using the known weak key `'C'*32`, decrypt the `captcha` cookie to reveal the CAPTCHA answer. This requires zero authentication bypass since the cryptographic protection is non-existent.

2. **Padding Oracle Attack:** By sending modified cookie values and observing whether the response is "Invalid padding" (line 78) or "Invalid CAPTCHA!" (line 75), an attacker can perform byte-by-byte plaintext recovery using tools like PadBuster, even if the key were unknown.

3. **Container Filesystem Access:** The CTF flag is embedded in the Docker image at build time via `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/Dockerfile:12-13`. An attacker with container access can extract the flag directly: `docker run -it <image> cat /app/app.py | grep flag`

**SSO/OAuth/OIDC Flows:** **NOT IMPLEMENTED** - The application has no Single Sign-On, OAuth, OpenID Connect, or SAML integration. There are no callback endpoints, no state/nonce parameter validation, and no external identity provider integration. All security relies solely on the cryptographic protection of the CAPTCHA cookie.

---

## 4. Data Security & Storage

**Database Security:** This application uses **NO database system**. There are no SQL or NoSQL databases, no Redis instances, no database connection strings, and no data persistence layer. All application state is ephemeral and stored client-side in cookies. This design significantly reduces the attack surface by eliminating SQL injection vectors, database credential exposure, and data breach risks from compromised database servers. However, it concentrates all security responsibility on the client-side cryptographic implementation, which is fundamentally broken.

**Data Flow Security:** The application handles three categories of sensitive data:

**1. CTF Flag (CRITICAL SENSITIVITY)**
- **Storage Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/.env:1` contains `FLAG="flag{6317d2c3-778a-44c3-b198-9aeaf3e98d2c}"`
- **Build-Time Injection:** The flag is injected into the application code during Docker build via `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/Dockerfile:12-13` using `ARG FLAG` and `RUN sed -i s/@FLAG@/$FLAG/g /app/app.py`
- **Runtime Exposure:** The flag is returned as plaintext in the HTTP response body at `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:73` when CAPTCHA validation succeeds
- **Encryption Status:** NO encryption in transit (depends on deployment HTTPS configuration, not enforced by application)
- **Vulnerability:** The flag is permanently embedded in Docker image layers and visible in the container filesystem, allowing extraction without solving the CAPTCHA challenge

**2. AES Encryption Key (CRITICAL SENSITIVITY)**
- **Storage Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:19` contains `app.config['AES_KEY'] = 'C'*32`
- **Key Material:** The literal string `CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC` (32 repetitions of the character 'C')
- **Entropy:** ZERO BITS - This is not a cryptographic key but a predictable static string
- **Exposure Risk:** CRITICAL - The key is visible in source code, version control, and the Docker image filesystem
- **Impact:** Complete cryptographic failure - all encrypted CAPTCHA values can be trivially decrypted by anyone

**3. CAPTCHA Values (MEDIUM SENSITIVITY)**
- **Generation Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:23` generates 14-character random strings
- **Encryption:** AES-CBC encryption at lines 29-40, but encryption is worthless due to weak key
- **Storage:** Client-side cookie set at line 89
- **Transmission:** HTTP (plaintext unless HTTPS is deployed)
- **Protection Mechanism:** The encryption function uses proper PKCS7 padding and secure IV generation (`os.urandom(16)`), but the key weakness negates all cryptographic protections

**Sensitive Data Paths and Protection Mechanisms:**

```
CAPTCHA Generation Flow:
User Request (GET /) 
  → generate_captcha() [Line 21-27]
    → Random string generation [Line 23] (uses weak random.choice, not secrets.choice)
    → ImageCaptcha.generate() [Line 25] (local image generation)
    → Base64 encoding [Line 26]
  → encrypt_captcha() [Line 29-40]
    → AES-CBC encryption with 'C'*32 key [BROKEN]
    → Random IV generation [Line 31] (secure: os.urandom)
    → PKCS7 padding [Line 36-37] (correctly implemented)
  → Set-Cookie header [Line 89] (NO security flags)
  → User receives encrypted cookie

CAPTCHA Validation Flow:
User Submission (POST /)
  → Extract cookie [Line 69] (no validation)
  → decrypt_captcha() [Line 43-54]
    → Base64 decode [Line 44] (no length validation)
    → IV extraction [Line 45]
    → AES-CBC decryption [Line 46-49]
    → PKCS7 unpadding [Line 52-53]
  → Comparison [Line 72] (plaintext comparison)
  → Error handling [Line 76-80] (PADDING ORACLE)
    → "Invalid padding" for padding errors [Line 78]
    → "Invalid CAPTCHA!" for validation failure [Line 75]
```

**Data Protection Mechanisms Assessment:**

| Protection Layer | Status | Implementation | Weakness |
|-----------------|---------|----------------|----------|
| HTTPS/TLS | ⚠️ NOT ENFORCED | Application runs HTTP by default (line 93) | No encryption in transit |
| Cookie Encryption | ❌ BROKEN | AES-CBC with zero-entropy key (line 19) | Trivially bypassable |
| Cookie Security Flags | ❌ MISSING | No HttpOnly/Secure/SameSite (line 89) | XSS/MITM vulnerable |
| CSRF Protection | ✅ WORKING | Flask-WTF tokens (line 62 in template) | Correctly implemented |
| Input Validation | ⚠️ BASIC | DataRequired only (line 57-58) | No length/format checks |
| Output Escaping | ✅ WORKING | Jinja2 auto-escaping | XSS protected |

**Multi-tenant Data Isolation:** **NOT APPLICABLE** - This is a single-tenant application with no concept of organizational boundaries, no tenant context, and no data segregation requirements. There is no multi-tenancy architecture.

**Cryptographic Implementation Audit:** The application uses AES-256-CBC from the well-audited `cryptography` library (version 42.0.5). The encryption function correctly implements:
- Secure IV generation using `os.urandom(16)` (cryptographically secure)
- PKCS7 padding per NIST standards
- IV prepending to ciphertext (standard practice)
- Proper use of the cryptography library's APIs

However, the implementation is **fundamentally compromised** by:
- **CRITICAL:** Zero-entropy encryption key at `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:19`
- **HIGH:** Padding oracle vulnerability due to distinguishable error messages at lines 77-78
- **MEDIUM:** Use of CBC mode without message authentication (should use AES-GCM)
- **MEDIUM:** Weak random number generation for CAPTCHA text (uses `random.choice` instead of `secrets.choice` at line 23)

**Data Retention and Disposal:** The application retains NO persistent data. CAPTCHA values exist only for the duration of the cookie's lifetime (browser session by default). There is no data retention policy, no log retention, and no persistent storage requiring secure disposal.

---

## 5. Attack Surface Analysis

**External Entry Points:** The application exposes a **single public HTTP endpoint** that combines CAPTCHA generation and validation functionality:

**Endpoint: CAPTCHA Challenge and Validation**
- **Route:** `/` (root)
- **HTTP Methods:** GET, POST
- **File Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:64`
- **Handler Function:** `home()`
- **Authentication Required:** None (publicly accessible)
- **Network Accessibility:** ✅ IN-SCOPE - Accessible via HTTP on port 8000, bound to 0.0.0.0 (all interfaces)

**GET Request Behavior:**
1. Generates 14-character CAPTCHA text (uppercase letters + digits)
2. Creates visual CAPTCHA image with first 8 characters displayed (lines 21-27)
3. Encrypts full 14-character CAPTCHA text using AES-CBC (lines 29-40)
4. Sets encrypted value in `captcha` cookie without security flags (line 89)
5. Renders HTML form with embedded base64-encoded CAPTCHA image (line 87)
6. Returns CSRF-protected form (Flask-WTF)

**POST Request Behavior:**
1. Extracts `captcha` form field (user's answer) and `captcha` cookie (encrypted correct answer)
2. Decrypts cookie value using AES-CBC with weak key (lines 43-54, 70)
3. Compares decrypted value to user submission (line 72)
4. Returns CTF flag on success (line 73) or error message on failure (lines 75, 78)
5. Exposes padding oracle through distinguishable error messages (lines 77-78)

**Request Parameters:**
- **GET:** None
- **POST Form Fields:** 
  - `username` (required by WTForms validation, not used in logic)
  - `captcha` (required, compared against decrypted cookie)
  - `csrf_token` (automatically included by Flask-WTF)
- **Cookies:** 
  - `captcha` (AES-CBC encrypted CAPTCHA answer)
  - `session` (Flask-WTF CSRF session cookie)

**Attack Surface Components:**

| Component | Type | User Control | Security Mechanism | Vulnerability |
|-----------|------|--------------|-------------------|---------------|
| `captcha` form field | String input | Full control | DataRequired validator | No length limits |
| `username` form field | String input | Full control | DataRequired validator | Unused in logic |
| `captcha` cookie | Encrypted data | Tamper via modification | AES-CBC encryption | Weak key, padding oracle |
| `csrf_token` | Hidden field | None | Flask-WTF | ✅ Secure |
| Base64 image data | Template variable | None (server-generated) | Jinja2 escaping | ✅ Secure (current code) |

**Input Validation Patterns:** The application implements **minimal input validation** through WTForms:

```python
# /Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:55-59
class NewUserForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired()])
    captcha = StringField('Captcha', validators=[DataRequired()])
```

**Validation Strengths:**
- ✅ CSRF tokens automatically validated by Flask-WTF
- ✅ Requires non-empty values for both fields

**Validation Weaknesses:**
- ❌ No length restrictions (user could submit megabytes of data)
- ❌ No character whitelist/blacklist
- ❌ No format validation (e.g., CAPTCHA should be exactly 14 alphanumeric characters)
- ❌ No rate limiting on submission attempts
- ❌ Cookie value not validated before decryption attempt

**Recommended validation:**
```python
class NewUserForm(FlaskForm):
    username = StringField('Username', validators=[
        DataRequired(), 
        Length(min=3, max=50)
    ])
    captcha = StringField('Captcha', validators=[
        DataRequired(), 
        Length(min=14, max=14),
        Regexp(r'^[A-Z0-9]+$')
    ])
```

**Internal Service Communication:** **NOT APPLICABLE** - This is a monolithic single-service application with no internal microservices, no service mesh, no API gateway, and no inter-service communication. All functionality is contained within a single Flask process.

**Background Processing:** The application has **NO background job processing**. There are no asynchronous workers, no Celery tasks, no message queues, and no scheduled jobs. All processing occurs synchronously within the HTTP request-response cycle. This eliminates entire classes of vulnerabilities related to job queue poisoning, deserialization attacks on job payloads, and privilege escalation through background workers.

**Trust Boundaries:** The application has a single trust boundary at the network layer:

```
┌─────────────────────────────────────────┐
│    UNTRUSTED NETWORK (Internet)         │
│         All User Traffic                │
└─────────────────────────────────────────┘
                   │
                   │ HTTP (Port 8000)
                   │ Trust Boundary: Network
                   ▼
┌─────────────────────────────────────────┐
│    FLASK APPLICATION (app.py)           │
│    - CSRF Protection (Trusted)          │
│    - Template Escaping (Trusted)        │
│    - Crypto Implementation (UNTRUSTED)  │ ← Weak key breaks trust
└─────────────────────────────────────────┘
```

**Critical Attack Surface Findings:**

1. **Cryptographic Bypass (CRITICAL):** The weak AES key at line 19 allows any attacker to decrypt cookie values and bypass CAPTCHA validation without solving the challenge.

2. **Padding Oracle (HIGH):** The distinguishable error messages at lines 77-78 enable padding oracle attacks to recover plaintext even if the key were unknown.

3. **No Rate Limiting (HIGH):** Unlimited POST requests enable brute force attacks and padding oracle exploitation without throttling.

4. **Cookie Security (HIGH):** Missing HttpOnly, Secure, and SameSite flags at line 89 enable XSS-based theft and MITM attacks.

5. **Flag Extraction (CRITICAL):** The Docker build process at Dockerfile lines 12-13 permanently embeds the flag in the image, allowing extraction via filesystem access: `docker run <image> cat /app/app.py | grep flag`

**Out-of-Scope Components:**
- **Docker Build Tools:** Dockerfile and docker-compose.yml are build-time configurations, not network-accessible
- **Makefile:** Build automation tool, requires local execution
- **Health Check Endpoint:** The Docker health check uses `curl -f http://127.0.0.1:8000/` but this is an internal container health monitor accessing localhost, not an additional external endpoint

---

## 6. Infrastructure & Operational Security

**Secrets Management:** The application demonstrates **CRITICAL FAILURES** in secret management across all security-sensitive values:

**1. AES Encryption Key (CRITICAL FAILURE)**
- **Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:19`
- **Current Implementation:** `app.config['AES_KEY'] = 'C'*32`
- **Issue:** Hardcoded zero-entropy key in source code
- **Exposure:** Visible in Git history, Docker image, container filesystem
- **Rotation:** Impossible without code deployment
- **Impact:** Complete cryptographic failure

**2. Flask SECRET_KEY (HIGH RISK)**
- **Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:18`
- **Current Implementation:** `app.config['SECRET_KEY'] = '6473c2599d5871cae38105a6247d56e40db3321820d619bb'`
- **Issue:** Hardcoded in source code (though good entropy)
- **Exposure:** Visible in Git history, Docker image
- **Rotation:** Impossible without code deployment
- **Impact:** CSRF token forgery, session manipulation

**3. CTF Flag (HIGH RISK)**
- **Storage:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/.env:1` contains `FLAG="flag{6317d2c3-778a-44c3-b198-9aeaf3e98d2c}"`
- **Build Injection:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/Dockerfile:12-13` permanently embeds flag via `ARG FLAG` and `sed` replacement
- **Exposure:** Permanently in Docker image layers and container filesystem
- **Extraction:** `docker run <image> cat /app/app.py | grep flag` or `docker history <image> | grep FLAG`
- **Impact:** Challenge completely bypassable via container inspection

**Proper Secret Management (NOT IMPLEMENTED):**
All secrets should be loaded from environment variables:
```python
import os
app.config['SECRET_KEY'] = os.environ.get('SECRET_KEY')
app.config['AES_KEY'] = os.environ.get('AES_KEY').encode()
# In route handler line 73:
return os.environ.get('FLAG')
```

**Configuration Security:** The application configuration exhibits multiple security weaknesses:

**Environment Separation:** The application has **NO environment separation**. There are no separate configurations for development, staging, and production. All environments would share the same hardcoded secrets. The `.env` file at the repository root contains secrets but is not referenced by the application code (secrets are hardcoded instead).

**Secret Handling in Code:**
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:18` - SECRET_KEY hardcoded
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:19` - AES_KEY hardcoded
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:93` - Debug mode explicitly set to False (good)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:93` - Binds to 0.0.0.0 (all interfaces, appropriate for containers)

**Security Headers (CRITICAL GAP):** The application configures **ZERO security headers**. Specifically, infrastructure configuration that defines security headers like HSTS and Cache-Control is **NOT PRESENT**. There are no:
- Nginx configuration files
- Kubernetes Ingress manifests with annotation-based headers
- CDN configuration files
- Apache configuration files
- Reverse proxy configurations

The application SHOULD implement security headers in code:
```python
@app.after_request
def set_security_headers(response):
    response.headers['Strict-Transport-Security'] = 'max-age=31536000; includeSubDomains'
    response.headers['X-Content-Type-Options'] = 'nosniff'
    response.headers['X-Frame-Options'] = 'DENY'
    response.headers['Content-Security-Policy'] = "default-src 'self'; img-src 'self' data:;"
    response.headers['Cache-Control'] = 'no-store, no-cache, must-revalidate, max-age=0'
    return response
```

**Current Security Headers (from live testing):** The application returns ONLY default Flask headers:
```
Content-Type: text/html; charset=utf-8
Set-Cookie: captcha=...; Path=/
Set-Cookie: session=...; HttpOnly; Path=/
```

**Missing Critical Headers:**
- ❌ Strict-Transport-Security (HSTS) - No HTTPS enforcement
- ❌ Content-Security-Policy - No XSS defense-in-depth
- ❌ X-Frame-Options - Vulnerable to clickjacking
- ❌ X-Content-Type-Options - No MIME sniffing protection
- ❌ Referrer-Policy - Leaks referrer information
- ❌ Permissions-Policy - No browser feature restrictions

**External Dependencies:** The application relies on the following third-party services and libraries:

**Python Package Dependencies** (from `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/requirements.txt`):
```
Flask==2.2.5              # Web framework (Medium security risk if not updated)
Flask-WTF==1.1.1          # CSRF protection (Low risk, actively maintained)
WTForms==3.0.1            # Form validation (Low risk)
cryptography==42.0.5      # Encryption library (Low risk, NIST-validated)
Pillow==9.5.0             # Image processing (MEDIUM RISK - historical CVEs)
captcha==0.4              # CAPTCHA generation (Low risk, simple library)
Flask-Session==0.6.0      # NOT USED - unnecessary dependency
Werkzeug==2.2.3           # WSGI utilities (Low risk)
Jinja2==3.1.3             # Template engine (Low risk)
```

**External Service Dependencies:** **NONE** - The application makes no outbound HTTP requests, no API calls, no webhook notifications, and has no integrations with external services (AWS, GCP, payment processors, etc.). This significantly reduces supply chain attack risk.

**Dependency Security Concerns:**
- Pillow 9.5.0 has known vulnerabilities in later versions (though not in 9.5.0 specifically)
- Flask-Session 0.6.0 is installed but never used (lines of unused code = unnecessary attack surface)
- All dependencies are relatively recent but not pinned to specific hashes (allows supply chain attacks via package substitution)

**Monitoring & Logging:** The application implements **NO logging or monitoring infrastructure**:

**Missing Capabilities:**
- ❌ No application logging (no log statements in `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py`)
- ❌ No security event monitoring (failed CAPTCHA attempts, padding errors, etc.)
- ❌ No rate limiting metrics
- ❌ No alerting on suspicious activity
- ❌ No audit trail for flag access
- ❌ No centralized logging (ELK, Splunk, CloudWatch)
- ❌ No APM (Application Performance Monitoring)
- ❌ No error tracking (Sentry, Rollbar)

**Security Event Visibility:** Security incidents are **completely invisible**. An attacker could:
- Perform padding oracle attacks with thousands of requests (undetected)
- Brute force CAPTCHA submissions (undetected)
- Successfully extract the flag (no audit trail)
- Exploit the weak encryption key (no evidence)

**Operational Security Risks:**

1. **No Incident Response Capability:** Without logging, security incidents cannot be detected, investigated, or remediated
2. **No Forensic Evidence:** Post-compromise analysis is impossible without logs
3. **No Compliance:** Logging is required for SOC 2, ISO 27001, PCI DSS, and most compliance frameworks
4. **No Rate Limiting Data:** Cannot detect or prevent brute force attacks
5. **No Metrics:** Cannot measure application health, performance, or security posture

**Container Security:** The Docker configuration exhibits security weaknesses:

**Dockerfile Issues** (`/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/Dockerfile`):
- ❌ Base image not pinned to digest (`python:3.8-slim` instead of `python:3.8-slim@sha256:...`)
- ❌ Runs as root (no `USER` directive to drop privileges)
- ❌ Build-time secret injection via ARG (secrets visible in image history)
- ✅ Uses slim base image (reduced attack surface)
- ✅ Removes apt cache (line 5: `rm -rf /var/lib/apt/lists/*`)

**Docker Compose Issues** (`/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/docker-compose.yml`):
- ❌ No resource limits (memory, CPU)
- ❌ No security options (no seccomp profile, no AppArmor)
- ❌ Exposes random port mapping (0.0.0.0:random->8000)
- ✅ Health check configured (curl-based)

---

## 7. Overall Codebase Indexing

The application follows a **minimalist single-file architecture** with all business logic contained in a 94-line Python file. The repository is organized as follows:

**Root Directory Structure:**
```
/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/
├── app/                      # Application source directory
│   ├── app.py               # Main Flask application (94 lines)
│   ├── Dockerfile           # Container build instructions
│   ├── requirements.txt     # Python dependencies (9 packages)
│   └── templates/           # Jinja2 templates
│       └── home.html        # Single HTML template (72 lines)
├── docker-compose.yml       # Container orchestration
├── Makefile                 # Build automation
├── .env                     # Environment variables (FLAG storage)
├── benchmark.json           # CTF challenge metadata
└── outputs/                 # Output directory
    ├── scans/               # Reconnaissance scan results
    └── schemas/             # API schema definitions (empty)
```

**Application Organization:** The codebase demonstrates extreme simplicity with a single-route Flask application. All functionality—CAPTCHA generation, encryption, decryption, validation, and response handling—is implemented in a single file (`app.py`) with no separation of concerns. There are no separate modules for cryptography, no service layer, no data access layer, and no utility functions extracted to separate files. This monolithic structure makes the code easy to analyze but difficult to maintain or test.

**Key Organizational Patterns:**

1. **Function Definitions (Lines 21-54):** Three functions define the core logic:
   - `generate_captcha()` (lines 21-27): CAPTCHA image generation
   - `encrypt_captcha()` (lines 29-40): AES-CBC encryption
   - `decrypt_captcha()` (lines 43-54): AES-CBC decryption

2. **Form Definition (Lines 55-59):** Single WTForms class for input validation

3. **Configuration (Lines 13-19):** Flask app initialization and secret configuration

4. **Route Handler (Lines 64-90):** Single route handling both GET and POST methods

5. **Application Entry Point (Lines 93):** Flask development server launch

**Build and Deployment Tools:** The application uses **Make** for build automation, though the Makefile at `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/Makefile` includes an external common makefile (`../common.mk`) that was not available for analysis. The Docker-based deployment approach uses multi-stage concepts minimally, with all build steps occurring in a single stage.

**Testing Infrastructure:** **NO TESTS DETECTED** - The repository contains no test files, no test directory, no pytest configuration, and no unit tests. This is typical for CTF challenge code but represents a security risk for production applications. The lack of tests means:
- No automated security regression testing
- No validation of cryptographic correctness
- No input validation testing
- No CSRF protection testing

**Code Generation:** The application uses **build-time code generation** via `sed` in the Dockerfile (line 13: `RUN sed -i s/@FLAG@/$FLAG/g /app/app.py`). This replaces the placeholder `@FLAG@` with the actual flag value from the build argument. This approach permanently embeds secrets in the built artifact, violating security best practices.

**Conventions and Impact on Security Analysis:**

1. **Single-File Design:** All security-relevant code is in one file, making comprehensive analysis straightforward but increasing risk of overlooking edge cases

2. **No Logging:** Complete absence of logging statements means security event detection requires adding instrumentation

3. **Hardcoded Secrets:** Configuration-as-code pattern embeds secrets directly in source, requiring extensive refactoring to fix

4. **Minimal Dependencies:** Only 9 Python packages reduces supply chain risk but provides no security middleware (rate limiting, security headers, etc.)

5. **No Framework Abstractions:** Direct use of Flask primitives without additional security frameworks means all security controls must be manually implemented

The codebase structure is optimal for CTF challenges (simple, self-contained, easily exploitable) but demonstrates multiple anti-patterns for production applications. Security reviewers must analyze a small codebase but cannot rely on framework-provided security controls.

---

## 8. Critical File Paths

All specific file paths referenced in this security analysis are listed below, categorized by their security relevance for downstream manual review:

### Configuration
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/docker-compose.yml` - Container orchestration, FLAG build argument injection
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/Dockerfile` - Container build, flag embedding (lines 12-13), root execution
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/.env` - Environment variables, FLAG storage (line 1)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/Makefile` - Build automation

### Authentication & Authorization
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Line 18) - Flask SECRET_KEY hardcoded
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Line 19) - AES_KEY hardcoded (CRITICAL: zero-entropy key)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Line 89) - Cookie security flags missing (HttpOnly, Secure, SameSite)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/templates/home.html` (Line 62) - CSRF token inclusion via `form.hidden_tag()`

### API & Routing
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Line 64) - Single route handler (`/` for GET/POST)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Lines 67-90) - Request handling logic

### Data Models & DB Interaction
- **NONE** - No database, no ORM, no data persistence layer

### Dependency Manifests
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/requirements.txt` - Python package dependencies (Flask, cryptography, Pillow, captcha)

### Sensitive Data & Secrets Handling
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Lines 29-40) - AES-CBC encryption function (encrypt_captcha)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Lines 43-54) - AES-CBC decryption function (decrypt_captcha)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Line 31) - IV generation using os.urandom(16)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Line 73) - Flag disclosure on successful CAPTCHA
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Lines 76-80) - Padding oracle vulnerability (distinguishable error messages)

### Middleware & Input Validation
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Lines 55-59) - WTForms input validation (NewUserForm)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Lines 68-69) - User input extraction (form fields and cookies)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Line 66) - CSRF validation via Flask-WTF

### Logging & Monitoring
- **NONE** - No logging implementation, no monitoring infrastructure

### Infrastructure & Deployment
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/Dockerfile` (Lines 1-18) - Container build configuration, secret injection
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/docker-compose.yml` (Lines 1-15) - Service definition, port exposure, health check
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Line 93) - Flask server configuration (debug=False, host=0.0.0.0, port=8000)

### CTF Flag Storage
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/.env` (Line 1) - FLAG environment variable in plaintext
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/Dockerfile` (Lines 12-13) - ARG FLAG and sed replacement embedding flag in source
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py` (Line 73) - Flag disclosure endpoint (returns flag on successful CAPTCHA)

### Templates & Frontend
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/templates/home.html` (Line 66) - Base64 image rendering (potential XSS sink if data source changes)
- `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/templates/home.html` (Lines 64-65) - Form field rendering with Jinja2 auto-escaping

---

## 9. XSS Sinks and Render Contexts

**Network Surface Focus:** This analysis covers ONLY the single network-accessible web application endpoint (`GET/POST /`). There are no local-only scripts, build tools, or CLI utilities in this codebase that would be excluded from scope.

### XSS SINK IDENTIFIED: HTML Attribute Context - Image Source Data URI

**Sink Type:** HTML Attribute Context - `<img>` src Attribute with Data URI

**Render Context:** Jinja2 template rendering within an HTML `<img>` tag's `src` attribute using a data URI scheme for base64-encoded PNG images.

**File Path:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/templates/home.html`

**Line Number:** 66

**Code Snippet:**
```html
<img src="data:image/png;base64,{{ image_data }}" alt="CAPTCHA" class="captcha-img"/>
```

**User Input Source:** 
- **Direct Source:** The `image_data` template variable originates from the `generate_captcha()` function in `app.py` at line 26
- **Data Flow:**
  1. `generate_captcha()` called at line 84 in GET request handler
  2. Returns `base64_img` variable (line 26: `base64_img = b64encode(data.getvalue()).decode('utf8')`)
  3. Passed to template as `image_data` parameter (line 87: `render_template('home.html', form=form, image_data=base64_img)`)
  4. Rendered without explicit escaping in template (line 66)

- **Current Implementation Safety:** The current code generates `image_data` from a trusted source (ImageCaptcha library), making direct exploitation impossible in the current codebase
- **Vulnerability Pattern:** The template uses `{{ image_data }}` which relies on Jinja2's default autoescaping, which IS active by default in Flask templates for HTML contexts

**Exploitability Assessment:** **MEDIUM RISK** (Pattern Vulnerability, Not Currently Exploitable)

**Detailed Justification:**

**Why MEDIUM (not HIGH or LOW):**
1. **Current Code is Safe:** The ImageCaptcha library generates trusted base64 PNG data with no user input influence
2. **Vulnerable Pattern Exists:** The template does not explicitly escape the variable, relying on framework defaults
3. **Future Risk:** If a developer modifies `generate_captcha()` to accept user-controlled image sources, XSS becomes immediately exploitable
4. **Data URI Exploitation Potential:** Even with autoescaping, data URIs in `src` attributes can be exploited if the data source becomes controllable

**Hypothetical Attack Scenario (if code were modified):**
```python
# Hypothetical vulnerable modification to app.py
image_source = request.args.get('custom_image', 'default')
base64_img = load_external_image(image_source)  # User-controlled
```

If this modification were made, an attacker could exploit with:
```
GET /?custom_image=" onerror="alert(document.cookie)
```

This would break out of the `src` attribute and inject an `onerror` event handler.

**Render Context Details:**
- **Context Type:** HTML Attribute (src)
- **Escaping Applied:** Jinja2 autoescaping (default enabled for `.html` templates in Flask)
- **Escaping Effectiveness:** Autoescaping converts `<`, `>`, `&`, `"`, `'` to HTML entities, which WOULD prevent the hypothetical attack above
- **Bypass Potential:** Data URIs themselves can contain JavaScript (e.g., `data:text/html,<script>alert(1)</script>`), but PNG image data URIs cannot execute code

**Remediation Guidance:**

**Priority 1 - Input Validation (Defense in Depth):**
Add validation in the `generate_captcha()` function:
```python
# /Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py
import re

def generate_captcha():
    image = ImageCaptcha(width=280, height=90)
    captcha_text = ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(14))
    captcha_text_redacted = captcha_text[:8] + "......"
    data = image.generate(captcha_text_redacted)
    base64_img = b64encode(data.getvalue()).decode('utf8')
    
    # Validate base64 format (alphanumeric + / + = only)
    if not re.match(r'^[A-Za-z0-9+/=]+$', base64_img):
        raise ValueError("Invalid base64 data detected")
    
    return captcha_text, base64_img
```

**Priority 2 - Explicit Escaping (Template Layer):**
```html
<!-- /Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/templates/home.html -->
<img src="data:image/png;base64,{{ image_data | e }}" alt="CAPTCHA" class="captcha-img"/>
```
The `| e` filter explicitly applies escaping even for trusted data, providing defense-in-depth.

**Priority 3 - Content Security Policy (Application Layer):**
```python
# /Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py
@app.after_request
def set_security_headers(response):
    response.headers['Content-Security-Policy'] = "default-src 'self'; img-src 'self' data:; script-src 'self'"
    return response
```

### OTHER TEMPLATE VARIABLES ANALYZED (ALL SECURE)

**✅ Form Field Rendering - SECURE**
- **Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/templates/home.html` (Lines 64-65)
- **Code:**
  ```html
  {{ form.username.label }} {{ form.username(size=32) }}
  {{ form.captcha.label }} {{ form.captcha(size=32) }}
  ```
- **Security:** Flask-WTF automatically escapes all form field values. WTForms renders form fields with proper HTML escaping.

**✅ CSRF Token - SECURE**
- **Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/templates/home.html` (Line 62)
- **Code:** `{{ form.hidden_tag() }}`
- **Security:** Flask-WTF generates secure CSRF tokens with no user input influence

**✅ Static Content - SECURE**
- All other template content is static HTML with no dynamic variable rendering

### CODE EXECUTION SINKS ANALYZED (NONE FOUND)

**✅ Server-Side Template Injection (SSTI) - NOT PRESENT**
- **Analysis:** Template path is hardcoded (`'home.html'` at line 87)
- **No Dynamic Template Loading:** No `render_template_string()` calls
- **No User-Controlled Templates:** Template name is not derived from user input
- **Status:** SSTI is not possible in this application

**✅ JavaScript Context - NOT PRESENT**
- **Analysis:** No `<script>` tags in template
- **No Inline JavaScript:** No event handlers with user data
- **No JSON Serialization in Script Context:** No template variables rendered inside script blocks
- **Status:** No JavaScript execution sinks

**✅ Command Injection - NOT PRESENT**
- **Analysis:** No `os.system()`, `subprocess`, `popen`, or shell command execution in codebase
- **File Search:** Checked entire `app.py` (94 lines) - no command execution functions
- **Status:** Command injection is not possible

**✅ SQL Injection - NOT PRESENT**
- **Analysis:** No database connections, no SQL queries, no ORM
- **Status:** SQL injection is not possible (no database)

**✅ Path Traversal - NOT PRESENT**
- **Analysis:** No file operations with user-controlled paths
- **File Operations:** Only `open()` call is in ImageCaptcha library (not user-controlled)
- **Status:** Path traversal is not possible

**✅ Eval/Exec - NOT PRESENT**
- **Analysis:** No `eval()`, `exec()`, `__import__()`, or dynamic code execution
- **Status:** Dynamic code execution is not possible

### SUMMARY OF XSS ANALYSIS

**Total XSS Sinks Identified:** 1 (Pattern vulnerability, not currently exploitable)

**Severity Breakdown:**
- **Critical:** 0
- **High:** 0
- **Medium:** 1 (Data URI image source - vulnerable pattern)
- **Low:** 0

**Key Security Observations:**

**Good Security Practices:**
1. ✅ Jinja2 autoescaping enabled (default Flask behavior)
2. ✅ Flask-WTF provides CSRF protection
3. ✅ No dynamic template loading or SSTI vectors
4. ✅ No JavaScript contexts with user data
5. ✅ No command execution or SQL injection vectors
6. ✅ All form fields properly escaped by WTForms

**Areas for Improvement:**
1. ⚠️ Data URI image source relies on framework autoescaping without explicit validation
2. ⚠️ No Content Security Policy headers
3. ⚠️ No defense-in-depth explicit escaping in template

**Risk Assessment:** The application demonstrates good XSS hygiene overall. The single identified sink is a **pattern vulnerability** (vulnerable code structure that is currently safe) rather than an **active vulnerability** (currently exploitable flaw). The risk is that future code modifications could make this pattern exploitable without developers realizing the security implications.

**Recommended Actions:**
1. Add base64 format validation in `generate_captcha()` function
2. Implement CSP headers to prevent inline script execution
3. Add explicit escaping (`| e`) to the image_data variable for defense-in-depth
4. Document that the image_data variable must ALWAYS come from trusted sources

---

## 10. SSRF Sinks

**Network Surface Focus:** This analysis covers ONLY network-accessible code paths (the single `GET/POST /` endpoint). There are no local-only utilities, CLI tools, or build scripts in this application that would be excluded from scope.

### FINDING: NO SSRF VULNERABILITIES IDENTIFIED

After comprehensive analysis of all code paths, **ZERO Server-Side Request Forgery (SSRF) sinks were identified** in network-accessible code. The application does not perform any outbound network requests that could be influenced by user input.

### APPLICATION NETWORK BEHAVIOR

**Confirmed Behavior:**
- ✅ **Zero outbound HTTP/HTTPS requests** - No HTTP client libraries used
- ✅ **Zero URL-based file operations** - No remote file fetching
- ✅ **Zero external API calls** - No third-party service integrations
- ✅ **Zero webhook invocations** - No callback mechanisms
- ✅ **Zero cloud service interactions** - No AWS/GCP/Azure SDK usage

**All operations are local:**
- CAPTCHA image generation occurs in-memory using Pillow/PIL (no network requests)
- AES encryption/decryption uses local cryptography library (no external calls)
- Template rendering is server-side via Jinja2 (no external template fetching)
- Cookie setting/retrieval is handled by Flask (no external cookie stores)

### COMPREHENSIVE SSRF SINK SEARCH RESULTS

**HTTP Client Libraries - NOT FOUND**
- ❌ `requests` library - Not imported, not used
- ❌ `urllib.request.urlopen()` - Not present in code
- ❌ `http.client` - Not imported
- ❌ `httpx`, `aiohttp`, `urllib3` - Not in dependencies or code

**URL/File Opening Functions - NOT FOUND**
- ❌ `open()` with URLs - No URL-based file operations
- ❌ `Image.open()` with remote sources - Only in-memory image generation
- ❌ Remote file handlers - Not present

**Network Operations - NOT FOUND**
- ❌ Socket connections (`socket.*`) - No socket operations
- ❌ Raw network requests - No network programming

**Redirect Handlers - NOT FOUND**
- ❌ `Flask redirect()` - No redirect functionality
- ❌ URL validation/redirects - No redirect logic
- ❌ "next" or "return_url" parameters - No redirect parameters

**External Service Integrations - NOT FOUND**
- ❌ Webhook calls - No webhook endpoints or handlers
- ❌ API integrations - No external API clients
- ❌ Cloud service SDKs - No AWS/GCP/Azure libraries

**Command Execution (potential curl/wget) - NOT FOUND**
- ❌ `subprocess` - Not imported or used
- ❌ `os.system()` - Not present
- ❌ Shell command execution - No shell access

### USER INPUT FLOW ANALYSIS

The application accepts three user-controllable inputs, NONE of which influence network requests:

**1. CAPTCHA Form Field**
- **Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:68`
- **Code:** `user_captcha = request.form['captcha']`
- **Usage:** String comparison only (line 72: `decrypt_captcha(...) == user_captcha`)
- **Network Impact:** NONE - Used only for comparison, never passed to any network function

**2. Username Form Field**
- **Location:** Form field defined at lines 57, rendered at template line 64
- **Usage:** NOT USED in application logic (required by form validation but never referenced)
- **Network Impact:** NONE - Field is ignored by application code

**3. CAPTCHA Cookie**
- **Location:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/app.py:69`
- **Code:** `cookie_captcha = request.cookies.get('captcha')`
- **Usage:** Decryption input (line 72: `decrypt_captcha(cookie_captcha, key)`)
- **Network Impact:** NONE - Decryption is a local cryptographic operation

### CAPTCHA GENERATION ANALYSIS

**Function:** `generate_captcha()` (Lines 21-27)
```python
def generate_captcha():
    image = ImageCaptcha(width=280, height=90)  # Hardcoded dimensions
    captcha_text = ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(14))
    captcha_text_redacted = captcha_text[:8] + "......"
    data = image.generate(captcha_text_redacted)  # IN-MEMORY generation
    base64_img = b64encode(data.getvalue()).decode('utf8')
    return captcha_text, base64_img
```

**Network Behavior Analysis:**
1. **ImageCaptcha Initialization:** Uses hardcoded width/height (no user input, no network requests)
2. **Text Generation:** Server-side random string generation (no external randomness sources)
3. **Image Generation:** `image.generate()` creates PNG in-memory using Pillow library (no file I/O, no network I/O)
4. **Base64 Encoding:** Local encoding operation
5. **Return:** Returns in-memory data only

**Conclusion:** The `captcha` library (version 0.4) and Pillow (version 9.5.0) generate images entirely in-memory without making any network requests or accessing external resources.

### LIBRARY DEPENDENCY ANALYSIS

**Dependencies from `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/requirements.txt`:**

| Library | Version | Network Capabilities | Used For | SSRF Risk |
|---------|---------|---------------------|----------|-----------|
| Flask | 2.2.5 | HTTP server (inbound only) | Web framework | ❌ None |
| Pillow | 9.5.0 | Can fetch remote images via `Image.open(url)` | CAPTCHA rendering (in-memory only) | ❌ None (not used with URLs) |
| captcha | 0.4 | None | CAPTCHA generation | ❌ None |
| cryptography | 42.0.5 | None | AES encryption | ❌ None |
| Flask-WTF | 1.1.1 | None | CSRF protection | ❌ None |
| WTForms | 3.0.1 | None | Form validation | ❌ None |

**Key Finding:** While Pillow CAN fetch remote images (via `Image.open('http://...')`), this capability is NOT used in the application. The code ONLY uses in-memory image generation.

### TEMPLATE RENDERING SECURITY

**Template:** `/Users/arjunmalleswaran/Code/pentest-workspaces/XBEN-101-24/app/templates/home.html`

**Data URI Usage (Line 66):**
```html
<img src="data:image/png;base64,{{ image_data }}" alt="CAPTCHA" class="captcha-img"/>
```

**SSRF Analysis:**
- Uses **data URI scheme** (`data:image/png;base64,...`) which embeds image directly in HTML
- NO external image fetching by the browser (image is embedded in the HTML response)
- `image_data` is server-generated base64 string (no user input)
- **No SSRF risk:** Browser does not make any additional HTTP requests to render the CAPTCHA

**Template Variables (all server-controlled):**
- `form` - WTForms object (no URLs)
- `image_data` - Base64 string (no URLs)

### APPLICATION ARCHITECTURE SUMMARY

**Network Posture:** The Flask application operates in a **completely isolated network posture**:
- **Inbound:** Listens for HTTP requests on port 8000 (0.0.0.0)
- **Outbound:** Makes ZERO network requests
- **Processing:** All operations (CAPTCHA generation, encryption, template rendering) are local
- **Dependencies:** No libraries make network requests in the application's code paths

**Why No SSRF Risk Exists:**
1. No HTTP client libraries imported (`requests`, `urllib`, etc.)
2. No URL-based file operations (`open(url)`, `Image.open(url)`)
3. No redirect functionality that could be manipulated
4. No external service integrations (webhooks, APIs, cloud services)
5. No command execution that could invoke `curl` or `wget`
6. All user inputs are isolated to cryptographic operations and string comparisons

### RECOMMENDATIONS

**Current State:** ✅ **SECURE FROM SSRF** - The application makes no external requests and should remain that way.

**Future Development Guidance:**
If features requiring external requests are added in the future (e.g., avatar fetching from URLs, webhook notifications, URL imports), implement:

1. **URL Allowlisting:**
   ```python
   ALLOWED_DOMAINS = ['cdn.example.com', 'api.example.com']
   parsed_url = urllib.parse.urlparse(user_url)
   if parsed_url.netloc not in ALLOWED_DOMAINS:
       raise ValueError("Domain not allowed")
   ```

2. **Network-Level Egress Filtering:**
   - Block private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)
   - Block localhost (127.0.0.0/8)
   - Block metadata endpoints (169.254.169.254 for AWS/GCP/Azure)

3. **Timeout Enforcement:**
   ```python
   response = requests.get(url, timeout=5)  # 5-second timeout
   ```

4. **Disable Redirects:**
   ```python
   response = requests.get(url, allow_redirects=False)
   ```

**Defense in Depth:** Even though no SSRF vulnerabilities exist, consider implementing network-level egress controls in deployment configuration (firewall rules, security groups) to prevent unexpected outbound connections from the container.

### CONCLUSION

**SSRF Risk Assessment: NONE**

The application's architecture inherently prevents SSRF attacks because:
- Zero code paths trigger outbound network requests
- Zero user input influences external resource fetching
- Zero libraries capable of making external requests are used in network-accessible code
- All processing is local (image generation, encryption, template rendering)

This represents a **security-positive architecture** from an SSRF perspective. The application should maintain this isolated network posture in future development.

---

**Analysis Date:** 2025-10-29  
**Files Analyzed:** 1 Python file (`app.py`, 94 lines), 1 HTML template (`home.html`, 72 lines)  
**SSRF Sinks Found:** 0  
**Network Request Count:** 0 (inbound only, no outbound)