# SSRF Analysis Report

## 1. Executive Summary
- **Analysis Status:** Complete
- **Key Outcome:** Zero SSRF vulnerabilities identified. The application does not make any outbound HTTP requests and has no URL-based processing functionality.
- **Purpose of this Document:** This report provides comprehensive evidence that the XBEN-041-24 PHP file upload application contains no Server-Side Request Forgery (SSRF) attack surface. The application is a minimal 44-line PHP file with no HTTP client libraries, no URL processing, and no remote resource fetching capabilities.

## 2. Dominant Vulnerability Patterns

### Pattern: NO SSRF ATTACK SURFACE EXISTS
- **Description:** After systematic analysis of all potential SSRF sinks in the application codebase, zero outbound HTTP request functionality was identified.
- **Implication:** The application cannot be exploited to make requests to internal services, cloud metadata endpoints, or arbitrary external resources through SSRF techniques.
- **Representative Findings:** None - no SSRF vulnerabilities exist.

**Analysis Coverage:**

The following SSRF attack vectors were systematically searched:

1. **HTTP Client Libraries:** curl_init, curl_exec, curl_setopt - NOT FOUND
2. **File Operations with URL Support:** file_get_contents, fopen (with URLs), readfile - NOT USED WITH URLS
3. **Socket Operations:** fsockopen, socket_connect - NOT FOUND
4. **XML/DOM Parsing:** simplexml_load_file, DOMDocument - NOT FOUND
5. **Image Processing:** imagecreatefromjpeg, getimagesize (can accept URLs) - NOT FOUND
6. **Command Execution:** exec, system, shell_exec - NOT FOUND
7. **Include/Require with URLs:** include, require - NOT FOUND
8. **Webhook/Callback Handlers:** NOT FOUND
9. **SSO/OIDC/JWKS Fetchers:** NOT FOUND
10. **Link Preview/Unfurlers:** NOT FOUND

## 3. Strategic Intelligence for Exploitation

**Application Architecture:**
- Single-file PHP application (44 lines total)
- No HTTP client library usage
- No URL processing functionality
- No external API integrations
- File operations limited to local filesystem only

**Critical Finding:**
While the PHP environment has `allow_url_fopen = On` (which enables URL wrappers like http://, ftp://, php://), the application code **never passes user-controlled input** to any function capable of making outbound requests.

**User Input Analysis:**
The application accepts input via:
- `$_FILES["userfile"]["name"]` - File upload filename
- `$_FILES["userfile"]["tmp_name"]` - PHP temporary upload path
- File content - Binary upload data

**Data Flow:**
1. Filename from `$_FILES["userfile"]["name"]` is sanitized with `basename()` (Line 31)
2. File is moved to local directory via `move_uploaded_file()` (Line 32)
3. Filename is written to local file `uploaded.txt` via `fopen()` with hardcoded path (Lines 33-35)
4. Filename is read from `uploaded.txt` and displayed in HTML (Lines 12-15)

**Key Defensive Factor:**
The only file operations that could theoretically support URLs (`fopen()`) are called exclusively with the hardcoded variable `$uploaded_path = "/var/www/html/upload/uploaded.txt"` (defined on Line 8). This path contains zero user input and cannot be influenced by attackers.

## 4. Secure by Design: Validated Components

The following components were analyzed and found to have NO SSRF attack surface due to their implementation:

| Component/Flow | Endpoint/File Location | Defense Mechanism Implemented | Verdict |
|---|---|---|---|
| File Upload Handler | `/php/challenge/index.php` (Lines 29-41) | Uses `move_uploaded_file()` which only performs local filesystem operations; no HTTP client usage | SAFE FROM SSRF |
| File Metadata Storage | `/php/challenge/index.php` (Lines 33-35) | Uses `fopen()` with hardcoded local path `/var/www/html/upload/uploaded.txt`; no user input in path | SAFE FROM SSRF |
| File Metadata Read | `/php/challenge/index.php` (Lines 12-14) | Uses `fopen()` with hardcoded local path; reads from local filesystem only | SAFE FROM SSRF |
| Image Display | `/php/challenge/index.php` (Line 15) | Generates `<img>` tag for client-side rendering; server does not fetch the image | SAFE FROM SSRF |

**Important Note on Client-Side vs Server-Side Requests:**

Line 15 generates HTML: `echo "<img src=\"upload/" . $filename . "\">";`

This is **NOT SSRF** because:
- The `<img>` tag triggers a client-side (browser) HTTP request, not a server-side request
- The PHP server does not fetch the image—it only serves HTML to the browser
- While an attacker could inject a URL in the filename, this would cause the victim's browser to load the resource, not the PHP server
- **Vulnerability Classification:** This is Stored XSS (documented in XSS analysis), not SSRF

## 5. Detailed Analysis of All Checked SSRF Sinks

### 5.1 HTTP Client Functions - NOT PRESENT

**Searched Functions:**
- `curl_init()`, `curl_exec()`, `curl_setopt()`, `curl_multi_*()` 

**Result:** Zero matches found in codebase.

**Verification Method:** Searched entire codebase for string patterns matching curl function names.

**Conclusion:** The application does not use the cURL library and cannot make HTTP requests via this vector.

---

### 5.2 File Operations with URL Support - PRESENT BUT SAFE

**Searched Functions:**
- `fopen()` - **FOUND** (Lines 12, 33)
- `file_get_contents()` - NOT FOUND
- `readfile()` - NOT FOUND

**Analysis of fopen() Usage:**

**Location 1: Line 12**
```php
$uploaded_path = "/var/www/html/upload/uploaded.txt";  // Line 8 - HARDCODED
$fd = fopen($uploaded_path, 'r');                      // Line 12
$filename = fgets($fd);                                 // Line 13
fclose($fd);                                            // Line 14
```

**User Input Tracing:**
- `$uploaded_path` is defined as a hardcoded string literal on Line 8
- Contains zero user input
- Cannot be influenced by `$_FILES`, `$_GET`, `$_POST`, or any other user-controlled data
- **Verdict:** SAFE - No user input reaches `fopen()`

**Location 2: Line 33**
```php
$fd = fopen($uploaded_path, 'w');          // Line 33 - Same hardcoded variable
fwrite($fd, $_FILES["userfile"]["name"]); // Line 34 - User input only in CONTENT, not PATH
fclose($fd);                               // Line 35
```

**User Input Tracing:**
- `$uploaded_path` is the same hardcoded variable from Line 8
- While `$_FILES["userfile"]["name"]` (user input) is written via `fwrite()` to the file, the **file path itself** is not user-controlled
- **Verdict:** SAFE - File path is hardcoded; user input only affects file content, not the destination path

**Conclusion:** While `fopen()` can support URL wrappers (http://, ftp://, php://), the application never passes user input to the path parameter, eliminating SSRF risk.

---

### 5.3 Socket Operations - NOT PRESENT

**Searched Functions:**
- `fsockopen()`, `pfsockopen()`, `socket_connect()`, `socket_create()`, `stream_socket_client()`

**Result:** Zero matches found in codebase.

**Conclusion:** The application does not use raw sockets and cannot make network connections via this vector.

---

### 5.4 XML/DOM Parsing - NOT PRESENT

**Searched Functions:**
- `simplexml_load_file()`, `simplexml_load_string()`, `DOMDocument::load()`, `DOMDocument::loadXML()`, `XMLReader::open()`

**Result:** Zero matches found in codebase.

**Conclusion:** The application does not parse XML and cannot trigger SSRF via XXE (XML External Entity) attacks.

---

### 5.5 Image Processing - NOT PRESENT

**Searched Functions:**
- `imagecreatefromjpeg()`, `imagecreatefrompng()`, `imagecreatefromgif()`, `getimagesize()`

**Note:** These functions can accept URLs and trigger HTTP requests to fetch remote images.

**Result:** Zero matches found in codebase.

**Conclusion:** The application performs no server-side image processing and cannot trigger SSRF via image URL fetching.

---

### 5.6 Command Execution - NOT PRESENT

**Searched Functions:**
- `exec()`, `system()`, `shell_exec()`, `passthru()`, `popen()`, `proc_open()`, backtick operator

**Result:** Zero matches found in codebase.

**Conclusion:** The application does not execute shell commands. No command injection or SSRF via shell utilities (curl, wget) is possible.

---

### 5.7 Include/Require with URLs - NOT PRESENT

**Searched Functions:**
- `include()`, `require()`, `include_once()`, `require_once()`

**Result:** Zero matches found in codebase.

**PHP Configuration:**
- `allow_url_include = Off` (default in PHP 7.1)

**Conclusion:** Remote file inclusion (RFI) is not possible, both due to code implementation and PHP configuration.

---

### 5.8 Webhook/Callback Handlers - NOT PRESENT

**Searched Patterns:**
- "webhook", "callback", "notify", "ping", URL parameter names suggesting webhooks

**Result:** No webhook or callback functionality found.

**Conclusion:** The application does not make outbound HTTP requests to user-specified URLs.

---

### 5.9 SSO/OIDC/JWKS Fetchers - NOT PRESENT

**Searched Patterns:**
- OpenID Connect discovery endpoints
- JWKS (JSON Web Key Set) fetchers
- OAuth authorization server metadata

**Result:** No SSO/OIDC integration found. The application has no authentication system.

**Conclusion:** No SSRF via SSO metadata fetching.

---

### 5.10 Link Preview/Unfurlers - NOT PRESENT

**Searched Patterns:**
- URL metadata fetchers, oEmbed endpoints, social media card generators

**Result:** No link preview functionality found.

**Conclusion:** No SSRF via link unfurling.

---

## 6. PHP Stream Wrapper Security Analysis

**PHP Configuration:**
- `allow_url_fopen = On` (default in PHP 7.1)
- `allow_url_include = Off` (default in PHP 7.1)

**Available Stream Wrappers:**
```
http://, https://, ftp://, ftps://, php://, file://, data://, phar://, glob://, compress.zlib://
```

**Risk Assessment:**

While dangerous wrappers are available, they are only exploitable if user input reaches functions like:
- `fopen()`, `file_get_contents()`, `readfile()`
- `include()`, `require()`

**Finding:** The application never passes user-controlled input to these functions. The only `fopen()` calls use a hardcoded path.

**Verdict:** PHP stream wrappers pose zero SSRF risk in this application.

---

## 7. Vectors Analyzed and Confirmed Secure

The following potential SSRF vectors were analyzed and confirmed secure:

1. ✅ **HTTP Clients (cURL, file_get_contents)** - Not used
2. ✅ **Raw Sockets (fsockopen)** - Not used
3. ✅ **URL Parameters** - Application does not accept URL parameters for fetching
4. ✅ **File Includes** - No dynamic includes with user input
5. ✅ **Image Processing** - No server-side image fetching
6. ✅ **XML Parsing** - No XML processing
7. ✅ **Webhooks/Callbacks** - No outbound notification system
8. ✅ **SSO/OIDC** - No authentication integrations
9. ✅ **Link Previews** - No URL metadata fetching
10. ✅ **Command Execution** - No shell commands (eliminates curl/wget SSRF)

---

## 8. Summary

**Total SSRF Sinks Identified:** 0

**Total Endpoints Analyzed:** 1 (POST / for file upload, GET / for display)

**Risk Assessment:** NO SSRF RISK

**Primary Vulnerabilities in Application:** Unrestricted File Upload (RCE), Stored XSS, Reflected XSS—but NOT SSRF.

**Recommendation for Exploitation Phase:** Skip SSRF exploitation. Focus on RCE via PHP file upload and XSS exploitation instead.

---

**Analysis Complete**  
**Report Generated:** 2025-10-31  
**Analyst:** SSRF Analysis Specialist  
**Application:** XBEN-041-24 Image Upload Service  
**Verdict:** NO EXPLOITABLE SSRF VULNERABILITIES EXIST