Class: Tem::Mr::Search::QueryBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/tem_mr_search/query_builder.rb

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ QueryBuilder

Returns a new instance of QueryBuilder.



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# File 'lib/tem_mr_search/query_builder.rb', line 174

def initialize
  @check_bytes = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  @query_key = Tem::Keys::Symmetric.generate
end

Class Method Details

.query {|builder| ... } ⇒ Object

Build a Query.

Yields:

  • (builder) 


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# File 'lib/tem_mr_search/query_builder.rb', line 6

def self.query
  builder = self.new
  yield builder
  builder.query
end

Instance Method Details

#attributes(attributes) ⇒ Object

Defines the object attributes imported into the map method.



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# File 'lib/tem_mr_search/query_builder.rb', line 13

def attributes(attributes)
  @attributes = attributes.to_a.map do |k, v|
    { :name => k,
      :type => v,
      :length => Tem::Abi.send(:"#{v}_length")        
    }
  end
end

#id_attribute(id_attribute) ⇒ Object

Defines the object attribute that’s used as an object ID.



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# File 'lib/tem_mr_search/query_builder.rb', line 23

def id_attribute(id_attribute)
  @id_attribute = id_attribute.to_sym
end

#map ⇒ Object

Defines the query’s map procedure.



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# File 'lib/tem_mr_search/query_builder.rb', line 28

def map
  @map_secpack = Tem::Assembler.assemble do |s|
    s.label :_secret
    s.label :_key
    s.data :tem_ubyte, @query_key.to_tem_key
    s.label :_check_bytes
    s.data :tem_ubyte, @check_bytes
    
    # User-provided ranking procedure (secret).
    s.label :_ranking
    yield s
    s.ret
    
    s.entry
    s.ldbc 24
    s.outnew
    # Compute score.
    s.call :_ranking      
    # Compute padding.
    s.ldbc 3
    s.ldwc :_nonce
    s.rnd
    s.mcfxb :from => :_check_bytes, :to => :_check,
            :size => @check_bytes.length
    
    # Encrypt output.
    s.ldwc :const => :_key
    s.rdk
    s.kefxb :from => :_id, :size => 23, :to => 0xFFFF
    s.halt
    
    s.label :_plain
    
    # Make room for query attributes.
    @attributes.each do |attribute|
      s.label attribute[:name]
      s.zeros attribute[:type], 1
    end
    # Object ID.
    s.label :_id
    s.zeros :tem_ubyte, 8
    # Object score.
    s.label :score
    s.zeros :tem_short, 1
    # Random nonce to prevent matching map outputs.
    s.label :_nonce
    s.zeros :tem_ubyte, 3
    # Check bytes to prevent malicious input corruption.
    s.label :_check
    s.zeros :tem_ubyte, @check_bytes.length
    
    s.stack 64
  end    
end

#query ⇒ Object 



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# File 'lib/tem_mr_search/query_builder.rb', line 164

def query
  raise "Map procedure not specified" unless @map_secpack
  raise "Reduce procedure not specified" unless @reduce_secpack
  raise "ID attribute not specified" unless @id_attribute
  
  ClientQuery.new :key => @query_key, :attributes => @attributes,
                  :map => @map_secpack, :reduce => @reduce_secpack,
                  :id_attribute => @id_attribute
end

#reduce ⇒ Object

Defines the query’s reduce procedure.



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# File 'lib/tem_mr_search/query_builder.rb', line 84

def reduce
  @reduce_secpack = Tem::Assembler.assemble do |s|
    s.label :_secret
    s.label :_key
    s.data :tem_ubyte, @query_key.to_tem_key
    s.label :_check
    s.data :tem_ubyte, @check_bytes
    
    s.label :_signed
    # User-provided comparison procedure (signed).
    s.label :_comparison_proc
    yield s
    s.ret
    
    s.entry
    s.ldbc :const => 24
    s.outnew      
    # Decrypt inputs.
    s.ldwc :const => :_key
    s.rdk
    s.stw :_key_id
    [1, 2].each do |i|
      s.ldw :_key_id
      s.kdfxb :from => :"_output#{i}", :to => :"_id#{i}", :size => 24
      
      # Compare the check bytes and abort if the inputs were tampered with.
      s.mcmpfxb :op1 => :"_check#{i}", :op2 => :"_check",
                :size => @check_bytes.length
      s.jz :"_check_#{i}_ok"
      s.halt
      s.label :"_check_#{i}_ok"
    end
    
    # Compare and output.
    s.call :_comparison_proc
    s.ldw :comparison
    s.jae :_output1_wins
    s.mcfxb :from => :_id2, :to => :_id1, :size => 16
    s.jmp :_output
    s.label :_output1_wins
    # Still do a memcpy, to prevent timing attacks.
    s.mcfxb :from => :_id2, :to => :_id2, :size => 16
    s.jmp :_output
    # Refresh the nonce to prevent learning about the comparison criteria.
    s.label :_output
    s.ldbc 3
    s.ldwc :_nonce1
    s.rnd
    # Encrypt output.
    s.ldwc :const => :_key
    s.rdk
    s.kefxb :from => :_id1, :size => 23, :to => 0xFFFF
    s.halt
    
    s.label :_plain
    # The comparison result produced by the user comparison procedure.
    s.label :comparison
    s.zeros :tem_short, 1
    s.label :_key_id
    s.zeros :tem_short, 1
    
    # The two inputs to reduce.
    [1, 2].each do |i|
      # Encrypted map/reduce output.
      s.label :"_output#{i}"        
      s.zeros :tem_ubyte, 24
      # Unencrypted input (decrypted inside TEM).
      s.label :"_id#{i}"
      s.zeros :tem_ubyte, 8
      s.label :"score#{i}"
      s.zeros :tem_short, 1
      s.label :"_nonce#{i}"
      s.zeros :tem_ubyte, 3        
      s.label :"_check#{i}"
      s.zeros :tem_ubyte, @check_bytes.length
    end
    s.stack 16
  end
end