RubySMB

This is a native Ruby implementation of the SMB Protocol Family. It currently supports:

1. [MS-SMB]
2. [MS-SMB2]

The RubySMB library provides client-level and packet-level support for the protocol. A user can parse and manipulate raw SMB packets, or use the client to perform higher-level SMB operations.

See the Wiki for more information on this project's long-term goals, style guide, and developer tips.

Installation

Add this line to your application's Gemfile:

gem 'ruby_smb'

And then execute:

$ bundle

Or install it yourself as:

$ gem install ruby_smb

Usage

Defining a packet

All packets are implemented in a declarative style with BinData. Nested data structures are used where appropriate to give users an easy method of manipulating individual fields inside of a packet.

SMB1

SMB1 Packets are made up of three basic components:

1. The SMB Header - This is a standard SMB Header. All SMB1 packets use the same SMB header.
2. The Parameter Block - This is where function parameters are passed across the wire in the packet. Parameter blocks will always have a 'Word Count' field that gives the size of the parameter block in words (2-bytes)
3. The Data Block - This is the data section of the packet. The data block will always have a 'byte count' field that gives the size of the Data block in bytes.

The SMB Header can always just be declared as a field in the BinData DSL for the packet class, because its structure never changes. For the Parameter block and data blocks, we always define subclasses for this particular packet. They inherit the 'Word Count' and 'Byte Count' fields, along with the auto-calculation routines for those fields, from their ancestors. Any other fields are then defined in our subclass before we start the DSL declarations for the packet.

Example:

module RubySMB
  module SMB1
    module Packet

      # This class represents an SMB1 TreeConnect Request Packet as defined in
      # [2.2.4.7.1 Client Request Extensions](https://msdn.microsoft.com/en-us/library/cc246330.aspx)
      class TreeConnectRequest < RubySMB::GenericPacket

        # A SMB1 Parameter Block as defined by the {TreeConnectRequest}
        class ParameterBlock < RubySMB::SMB1::ParameterBlock
          and_x_block          :andx_block
          tree_connect_flags   :flags
          uint16               :password_length, label: 'Password Length', initial_value: 0x01
        end

        class DataBlock < RubySMB::SMB1::DataBlock
          stringz  :password, label: 'Password Field', initial_value: '',    length: lambda { self.parent.parameter_block.password_length }
          stringz  :path,     label: 'Resource Path'
          stringz  :service,  label: 'Resource Type',  initial_value: '?????'
        end

        smb_header        :smb_header
        parameter_block   :parameter_block
        data_block        :data_block

        def initialize_instance
          super
          smb_header.command = RubySMB::SMB1::Commands::SMB_COM_TREE_CONNECT
        end

      end
    end
  end
end

SMB2

SMB2 Packets are far simpler than their older SMB1 counterparts. We still abstract out the SMB2 header since it is the same structure used for every packet. Beyond that, the SMB2 packet is relatively flat in comparison to SMB1.

Example:

module RubySMB
  module SMB2
    module Packet

      # An SMB2 TreeConnectRequest Packet as defined in
      # [2.2.9 SMB2 TREE_CONNECT Request](https://msdn.microsoft.com/en-us/library/cc246567.aspx)
      class TreeConnectRequest < RubySMB::GenericPacket
        endian       :little
        smb2_header  :smb2_header
        uint16       :structure_size, label: 'Structure Size', initial_value: 9
        uint16       :flags,          label: 'Flags',          initial_value: 0x00
        uint16       :path_offset,    label: 'Path Offset',    initial_value: 0x48
        uint16       :path_length,    label: 'Path Length',    initial_value: lambda { self.path.length }
        string       :path,           label: 'Path Buffer'

        def initialize_instance
          super
          smb2_header.command = RubySMB::SMB2::Commands::TREE_CONNECT
        end

        def encode_path(path)
          self.path = path.encode("utf-16le")
        end
      end
    end
  end
end

Using a Packet class

Manually

You can create an instance of any particular packet class, and then reach into the data structure to set or read explicit values in a fairly straightforward manner.

Example:

2.3.3 :001 > packet = RubySMB::SMB1::Packet::TreeConnectRequest.new
 => {:smb_header=>{:protocol=>4283649346, :command=>117, :nt_status=>0, :flags=>{:reply=>0, :opbatch=>0, :oplock=>0, :canonicalized_paths=>1, :case_insensitive=>1, :reserved=>0, :buf_avail=>0, :lock_and_read_ok=>0}, :flags2=>{:reserved1=>0, :is_long_name=>0, :reserved2=>0, :signature_required=>0, :compressed=>0, :security_signature=>0, :eas=>0, :long_names=>1, :unicode=>0, :nt_status=>1, :paging_io=>1, :dfs=>0, :extended_security=>0, :reparse_path=>0}, :pid_high=>0, :security_features=>"\x00\x00\x00\x00\x00\x00\x00\x00", :reserved=>0, :tid=>0, :pid_low=>0, :uid=>0, :mid=>0}, :parameter_block=>{:word_count=>4, :andx_block=>{:andx_command=>255, :andx_reserved=>0, :andx_offset=>0}, :flags=>{:reserved=>0, :extended_response=>1, :extended_signature=>0, :reserved2=>0, :disconnect=>0, :reserved3=>0, :reserved4=>0}, :password_length=>1}, :data_block=>{:byte_count=>8, :password=>"", :path=>"", :service=>"?????"}}
2.3.3 :002 > packet.parameter_block
 => {:word_count=>4, :andx_block=>{:andx_command=>255, :andx_reserved=>0, :andx_offset=>0}, :flags=>{:reserved=>0, :extended_response=>1, :extended_signature=>0, :reserved2=>0, :disconnect=>0, :reserved3=>0, :reserved4=>0}, :password_length=>1}
2.3.3 :003 > packet.parameter_block.flags
 => {:reserved=>0, :extended_response=>1, :extended_signature=>0, :reserved2=>0, :disconnect=>0, :reserved3=>0, :reserved4=>0}
2.3.3 :004 > packet.parameter_block.flags.extended_signature = 1
 => 1
2.3.3 :005 > packet.parameter_block.flags
 => {:reserved=>0, :extended_response=>1, :extended_signature=>1, :reserved2=>0, :disconnect=>0, :reserved3=>0, :reserved4=>0}
2.3.3 :006 >
2.3.3 :006 > packet.data_block.password = 'guest'
 => "guest"
2.3.3 :007 > packet.data_block.password
 => "guest"
2.3.3 :008 > packet.data_block
 => {:byte_count=>13, :password=>"guest", :path=>"", :service=>"?????"}
2.3.3 :009 >

You can also pass field/value pairs into the packet constructor as arguments, defaulting individual fields as desired.

Example:

2.3.3 :017 > packet = RubySMB::SMB2::Packet::TreeConnectRequest.new(path:'test')
 => {:smb2_header=>{:protocol=>4266872130, :structure_size=>64, :credit_charge=>0, :nt_status=>0, :command=>0, :credits=>0, :flags=>{:reserved3=>0, :signed=>0, :related_operations=>0, :async_command=>0, :reply=>0, :reserved2=>0, :reserved1=>0, :replay_operation=>0, :dfs_operation=>0}, :next_command=>0, :message_id=>0, :process_id=>65279, :tree_id=>0, :session_id=>0, :signature=>"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}, :structure_size=>9, :flags=>0, :path_offset=>72, :path_length=>4, :path=>"test"}
2.3.3 :018 > packet.path
 => "test"

Reading from a Binary Blob

Sometimes you need to read a binary data and apply one of the packet structures to it. For example, when you are reading a response packet, you will need to read the raw response string into an actual packet class. This is done using the #read class method.

2.3.3 :014 > blob = "\xFFSMB+\x00\x00\x00\x00\x98\x01`\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00"
 => "\xFFSMB+\u0000\u0000\u0000\u0000\x98\u0001`\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0001\u0000\u0000\u0000\u0000"
2.3.3 :015 > packet = RubySMB::SMB1::Packet::EchoResponse.read(blob)
 => {:smb_header=>{:protocol=>4283649346, :command=>43, :nt_status=>0, :flags=>{:reply=>1, :opbatch=>0, :oplock=>0, :canonicalized_paths=>1, :case_insensitive=>1, :reserved=>0, :buf_avail=>0, :lock_and_read_ok=>0}, :flags2=>{:reserved1=>0, :is_long_name=>0, :reserved2=>0, :signature_required=>0, :compressed=>0, :security_signature=>0, :eas=>0, :long_names=>1, :unicode=>0, :nt_status=>1, :paging_io=>1, :dfs=>0, :extended_security=>0, :reparse_path=>0}, :pid_high=>0, :security_features=>"\x00\x00\x00\x00\x00\x00\x00\x00", :reserved=>0, :tid=>0, :pid_low=>0, :uid=>0, :mid=>0}, :parameter_block=>{:word_count=>1, :sequence_number=>0}, :data_block=>{:byte_count=>0, :data=>""}}
2.3.3 :016 >

Outputting to a Binary Blob

Any structure or packet in RubySMB can also be converted back into a binary blob using BinData's #to_binary_s method.

Example:

2.3.3 :012 > packet = RubySMB::SMB1::Packet::EchoResponse.new
 => {:smb_header=>{:protocol=>4283649346, :command=>43, :nt_status=>0, :flags=>{:reply=>1, :opbatch=>0, :oplock=>0, :canonicalized_paths=>1, :case_insensitive=>1, :reserved=>0, :buf_avail=>0, :lock_and_read_ok=>0}, :flags2=>{:reserved1=>0, :is_long_name=>0, :reserved2=>0, :signature_required=>0, :compressed=>0, :security_signature=>0, :eas=>0, :long_names=>1, :unicode=>0, :nt_status=>1, :paging_io=>1, :dfs=>0, :extended_security=>0, :reparse_path=>0}, :pid_high=>0, :security_features=>"\x00\x00\x00\x00\x00\x00\x00\x00", :reserved=>0, :tid=>0, :pid_low=>0, :uid=>0, :mid=>0}, :parameter_block=>{:word_count=>1, :sequence_number=>0}, :data_block=>{:byte_count=>0, :data=>""}}
2.3.3 :013 > packet.to_binary_s
 => "\xFFSMB+\x00\x00\x00\x00\x98\x01`\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00"

Using the Client

Sitting on top of the packet layer in RubySMB is the RubySMB::Client class. This is the abstraction that most users of RubySMB will interact with. It provides simple conveience methods for performing SMB actions. It handles the creation, sending and receiving of packets for the user, providing reasonable defaults in many cases.

Negotiation

The RubySMB client is capable of multi-protocol negotiation. The user simply specifies whether SMB1 and/or SMB2 should be supported, and the client negotiates the protocol and dialect behind the scenes.

In the following example, we tell the client that both SMB1 and SMB2 should be supported. The client will then negotiate with the server which version should be used.

Negotiation Example:

  sock = TCPSocket.new address, 445
  dispatcher = RubySMB::Dispatcher::Socket.new(sock)

  client = RubySMB::Client.new(dispatcher, username: 'msfadmin', password: 'msfadmin')
  client.negotiate

Authentication

RubySMB uses the Ruby NTLM gem for authentication. While the client will not currently attempt older basic authentication on its own, it will attempt an anonymous login if no user credentials are supplied.

Authenticated Example:

  sock = TCPSocket.new address, 445
  dispatcher = RubySMB::Dispatcher::Socket.new(sock)

  client = RubySMB::Client.new(dispatcher, username: 'msfadmin', password: 'msfadmin')
  client.negotiate
  client.authenticate

Anonymous Example:

      sock = TCPSocket.new address, 445
      dispatcher = RubySMB::Dispatcher::Socket.new(sock)

      client = RubySMB::Client.new(dispatcher, username: '', password: '')
      client.negotiate
      client.authenticate

Connecting to a Tree

While there is one RubySMB::Client object that supports both SMB1 and SMB2, once the library connects to an SMB tree, it returns a protocol-specific RubySMB::Tree object. This Tree object executes all subsequent file operations on the tree.

In the below example we see a simple script to connect to a remote tree, and list all files in a given sub-directory.

Example:

      sock = TCPSocket.new address, 445
      dispatcher = RubySMB::Dispatcher::Socket.new(sock)

      client = RubySMB::Client.new(dispatcher, username: 'msfadmin', password: 'msfadmin')
      client.negotiate
      client.authenticate

      begin
        tree = client.tree_connect('TEST_SHARE')
        puts "Connected to #{path} successfully!"
      rescue StandardError => e
        puts "Failed to connect to #{path}: #{e.message}"
      end

      files = tree.list(directory: 'subdir1')

      files.each do |file|
        create_time = file.create_time.to_datetime.to_s
        access_time = file.last_access.to_datetime.to_s
        change_time = file.last_change.to_datetime.to_s
        file_name   = file.file_name.encode("UTF-8")

        puts "FILE: #{file_name}\n\tSIZE(BYTES):#{file.end_of_file}\n\tSIZE_ON_DISK(BYTES):#{file.allocation_size}\n\tCREATED:#{create_time}\n\tACCESSED:#{access_time}\n\tCHANGED:#{change_time}\n\n"
      end

Developer tips

It is useful to have Wireshark and a reference SMB client, such as Impacket's installed to help debug and compare output:

Wireshark

Configure Wireshark in Debian-based systems to be able to capture traffic without root user privileges:

• sudo apt-get install wireshark
• sudo dpkg-reconfigure wireshark-common
• sudo addgroup wireshark
• sudo usermod -a -G wireshark <USERNAME>

Impacket

• sudo apt-get install python-setuptools
• sudo easy_install pyasn1 pycrypto
• Download from GitHub (https://github.com/coresecurity/impacket)
• sudo python setup.py install
• cd examples && python smbclient.py <USER>:<PASS>@<WINDOWS HOST IP>

License

ruby_smb is released under a 3-clause BSD license. See LICENSE.txt for full text.

Contributing

1. Fork it ( https://github.com/rapid7/ruby_smb/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request