Class: Memorandom::Scanner

Inherits:
Object
  • Object
show all
Defined in:
lib/memorandom/scanner.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(opts = {}) ⇒ Scanner

Returns a new instance of Scanner.



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# File 'lib/memorandom/scanner.rb', line 11

def initialize(opts={})
  plugin_names = Memorandom::PluginManager.plugins.keys

  # Allow only a subset of plugins to be selected
  if opts[:plugins]
    plugin_names = Memorandom::PluginManager.plugins.keys.select{ |name|  
      opts[:plugins].include?(name) 
    }
  end

  # Load the selected plugins
  self.plugins = plugin_names.map { |name|
    Memorandom::PluginManager.plugins[name].new(self)
  }

  self.window  = opts[:window]  || 1024*1024
  self.overlap = opts[:overlap] || 1024*4
  self.output  = opts[:output]

  FileUtils.mkdir_p(self.output) if self.output

end

Instance Attribute Details

#output ⇒ Object

Returns the value of attribute output.



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# File 'lib/memorandom/scanner.rb', line 9

def output
  @output
end

#overlap ⇒ Object

Returns the value of attribute overlap.



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# File 'lib/memorandom/scanner.rb', line 9

def overlap
  @overlap
end

#plugins ⇒ Object

Returns the value of attribute plugins.



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# File 'lib/memorandom/scanner.rb', line 8

def plugins
  @plugins
end

#source ⇒ Object

Returns the value of attribute source.



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# File 'lib/memorandom/scanner.rb', line 8

def source
  @source
end

#window ⇒ Object

Returns the value of attribute window.



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# File 'lib/memorandom/scanner.rb', line 9

def window
  @window
end

Instance Method Details

#clean_filename(name) ⇒ Object 



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# File 'lib/memorandom/scanner.rb', line 144

def clean_filename(name)
  name.gsub(/[^a-zA-Z0-9_\.\-]/, '_').gsub(/_+/, '_')
end

#display(str) ⇒ Object 



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# File 'lib/memorandom/scanner.rb', line 148

def display(str)
  $stdout.puts(str)
end

#report_hit(info) ⇒ Object 



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# File 'lib/memorandom/scanner.rb', line 113

def report_hit(info)
  unless self.output
    display("[+] #{source} #{info[:type]}@#{info[:offset]} (#{info[:data][0,32].inspect}...)")
    return
  end

  fname = source.split("/").last[0,128] + "_"
  fname << info[:data][0,16].unpack("H*").first
  fname << "_#{info[:offset]}.#{info[:type]}"
  yname = fname + ".yml"

  fname = clean_filename(fname)
  yname = clean_filename(yname)

  fpath = ::File.join(self.output, fname)
  ::File.open(fpath, "wb") { |fd| fd.write(info[:data]) }

  display("[+] #{source} #{info[:type]}@#{info[:offset]} (#{info[:data][0,32].inspect}) stored in #{fpath}")

  ypath = ::File.join(self.output, yname)
  yhash = { 
    :source    => source, 
    :type      => info[:type], 
    :offset    => info[:offset], 
    :timestamp => Time.now,
    :length    => info[:data].length
  }
  ::File.open(ypath, "wb") { |fd| fd.write(yhash.to_yaml) }

end

#scan(target, source_name = nil) ⇒ Object 



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# File 'lib/memorandom/scanner.rb', line 34

def scan(target, source_name = nil)
  fd = nil

  if target.respond_to?(:read)
    self.source = source_name || target.to_s
  else
    case target
    when '-'
      fd = $stdin
      self.source = source_name || '<stdin>'
    else
      unless ( File.file?(target) or File.blockdev?(target) or File.chardev?(target) )
        display("[-] Skipping #{target}: not a file")
        return
      end
      begin
        fd = File.open(target, "rb")
        self.source = source_name ||"file:#{target.dup}"
      rescue ::Interrupt
        raise $!
      rescue ::Exception
        display("[-] Skipping #{target}: #{$!.class} #{$!}")
        return
      end
    end
  end

  # Reset the plugin state between each target
  self.plugins.each { |plugin| plugin.reset }

  buffer = fd.read(self.window)
  offset = 0

  # Skip empty sources (an empty first read)
  return unless buffer

  while buffer.length > 0

    self.plugins.each do |plugin|
      # display("[*] Scanning #{buffer.length} bytes at offset #{offset}")

      # Track a temporary per-plugin buffer and offset
      scan_buffer = buffer
      scan_offset = offset 

      # Adjust the buffer and offset if any hits have been found that are 
      # greater than offset. This is required because of overlap between 
      # search windows. It is rare, but should be handled here so that
      # plugins don't have to worry about it.

      adjust = plugin.hits.keys.select{|hit| hit > offset }.last
      if adjust
        start_index = ( adjust - offset + 1 )
        scan_buffer = buffer[start_index, buffer.length-start_index]
        scan_offset += start_index
      end

      # Scan the buffer with the plugin
      plugin.scan(scan_buffer, scan_offset)
    end

    # Calculate the next sliding window 
    seeked = self.window - self.overlap
    offset += seeked

    nbytes = fd.read(seeked)
    break if not nbytes

    # Append new data to the end of the buffer
    buffer << nbytes

    # Delete most of the previous data from the beginning
    buffer[0, seeked] = ''
  end

  # Close the file descriptor if we opened it
  fd.close if source =~ /^file:/
end