Class: Elf::Policy::Policy

Inherits:
Object
  • Object
show all
Defined in:
lib/mithril/policy/dsl.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Policy

Returns a new instance of Policy.



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# File 'lib/mithril/policy/dsl.rb', line 64

def initialize
  @data={}
  @calls=[]
  @states ={}
  @tags = {}
  @imported_symbols = {}
end

Instance Attribute Details

#calls ⇒ Object

Returns the value of attribute calls.



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# File 'lib/mithril/policy/dsl.rb', line 36

def calls
  @calls
end

#data ⇒ Object

Returns the value of attribute data.



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# File 'lib/mithril/policy/dsl.rb', line 36

def data
  @data
end

#imported_symbols ⇒ Object

Returns the value of attribute imported_symbols.



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# File 'lib/mithril/policy/dsl.rb', line 37

def imported_symbols
  @imported_symbols
end

#start ⇒ Object

Returns the value of attribute start.



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# File 'lib/mithril/policy/dsl.rb', line 36

def start
  @start
end

#tags ⇒ Object

Returns the value of attribute tags.



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# File 'lib/mithril/policy/dsl.rb', line 36

def tags
  @tags
end

Instance Method Details

#<<(*transitions) ⇒ Object 



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# File 'lib/mithril/policy/dsl.rb', line 43

def <<(*transitions)
  transitions.each do |t|
    if t.is_a? Data
      x= data
      x[t.from] ||= {}
      x[t.from][t.tag] ||= t
      if(x[t.from][t.tag].to  != t.to)
        raise ArgumentError "Invalid Policy, different to states on same tag" #TODO: allow
        #different accesses to go to different tags. at the moment, this is moot, because data
        #access is unconditional
      end
      x[t.from][t.tag].read ||= t.read
      x[t.from][t.tag].write ||= t.write
      x[t.from][t.tag].exec ||= t.exec            
    elsif t.is_a? Call
      calls << t
    else
      raise ArgumentError.new "#{t.class} is not a valid transition"
    end
  end
end

#inject(file) ⇒ Object 



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# File 'lib/mithril/policy/dsl.rb', line 202

def inject(file)
  case file.machine
  when ElfFlags::Machine::EM_X86_64
    write_amd64(file)
  else
    raise RuntimeError.new "Wrong architecture for ARM64"
  end
end

#resolve_reference(elffile, relocations, offset, ref) ⇒ Object 



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# File 'lib/mithril/policy/dsl.rb', line 71

def resolve_reference(elffile, relocations,offset, ref)
  if(ref.is_a? Integer)
    ref.to_i
  elsif(ref == "_dl_runtime_resolve") #HACK:HACK:HACK: I couldn't hack ld.so to fix this, so
    #here comes a nasty hack
    #note that the address of _dl_runtime_resolve is 16 bytes into PLT.GOT
    if !elffile.symbols.include? "_elfp_hidden_trampolineaddr"
      pltgot = elffile.dynamic.pltgot or raise RuntimeError.new "No plt.got for _dl_runtime_resolve hack"
      elffile.symbols << Elf::Symbol.new("_elfp_hidden_trampolineaddr", pltgot,STT::STT_OBJECT,16, STB::STB_LOCAL,8)            
    end
    symb = elffile.symbols["_elfp_hidden_trampolineaddr"]
    relocations << Elf::Relocation.new.tap{|x|
      x.type = R::R_X86_64_COPY
      x.offset = offset
      x.symbol = symb
      x.is_dynamic = true
      x.addend = 0
    }
    0xDEADBEEF
  else
    raise RuntimeError.new "Symbol #{ref} not found" unless elffile.symbols.include? ref          
    relocations << Elf::Relocation.new.tap{|x|
      x.type = R::R_X86_64_64
      x.offset = offset
      x.symbol = elffile.symbols[ref]
      x.is_dynamic = true
      x.addend = 0
    }
    2**64-1
  end
end

#resolve_size(elffile, relocations, offset, ref) ⇒ Object 



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# File 'lib/mithril/policy/dsl.rb', line 102

def resolve_size(elffile,relocations, offset, ref)
    if(ref.is_a? Integer)
    ref.to_i
  else
    raise RuntimeError.new "Symbol #{ref} not found" unless elffile.symbols.include? ref          
    relocations << Elf::Relocation.new.tap{|x|
      x.type = R::R_X86_64_SIZE64
      x.offset = offset
      x.symbol = elffile.symbols[ref]
      x.is_dynamic = true
      x.addend = 0
    }
    2**64-1
  end
end

#states ⇒ Object 



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# File 'lib/mithril/policy/dsl.rb', line 38

def states
  t = data.keys + data.values.map(&:keys).flatten + calls.map(&:from) +
    calls.map(&:to)
  t.uniq
end

#write_amd64(elffile) ⇒ Object 



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# File 'lib/mithril/policy/dsl.rb', line 117

def write_amd64(elffile)
  factory = ElfStructFactory.instance(:little,64)
  @imported_symbols.each_key {|symbol|
    if elffile.symbols.include?(symbol)
      elffile.symbols[symbol].is_dynamic = true
    else
      elffile.symbols << Elf::Symbol.new(symbol,nil,Elf::STT::STT_OBJECT, 0, Elf::STB::STB_GLOBAL, 0).tap {|x|
        x.semantics = Elf::SHN::SHN_UNDEF
      }
    end
  }
  out = factory.elfp_header.new()
  state_ids = {}
  tag_ids = {}
  relocations = []
  states = states()
  @start = states.first unless states.include? @start
  #These have to be filled in the order in which they are written
  #FIXME: Make these aware of double transitions to the same range/ state
  states.each_with_index do |state,index|
    id = index + 2
    id = 1 if @start == state
    out.states << factory.elfp_state.new.tap {|x|
      x.id = id
      x.stackid = 0 
    }
    state_ids[state] = id
    print "State #{state} #{id}\n"
  end
  tag_ids[:default] = 0 
  @tags.each_with_index do |(name,ranges),index|
    tag_ids[name] = index+1
    ranges.each do |data|
      out.tags << factory.elfp_tag.new.tap {|x|
        x.tag = index + 1
        x.addr = 0
        x.siz = 0
      }
      out.tags.last.tap {|x|
        x.addr  = resolve_reference(elffile,relocations,x.addr.offset,data.low)
        if data.high.nil?
          x.siz = resolve_size(elffile,relocations,x.siz.offset,data.low)
        else
          pp "Warning, emitting SIZE symbol with value  #{ data.high.to_i rescue data.high.name}"
          x.siz = resolve_reference(elffile,relocations,x.siz.offset,data.high)
        end
      }
    end
    print "Tag #{name} #{index + 1} \n"
  end
  self.calls.each do |call|
    out.calls << factory.elfp_call.new.tap {|x|
      x.from = state_ids[call.from]
      x.to = state_ids[call.to]
      x.parambytes = call.parambytes
      x.returnbytes = call.parambytes
    }
    out.calls.last.off = resolve_reference(elffile,relocations,out.calls.last.off.offset, call.symbol)
  end
  self.data.values.map(&:values).flatten.each do |data|
    out.data << factory.elfp_data.new.tap {|x|
      x.from = state_ids[data.from]
      x.to = state_ids[data.to]
      x.type = 0
      x.type |= ELFP::ELFP_RW_READ if data.read
      x.type |= ELFP::ELFP_RW_WRITE if data.write
      x.type |= ELFP::ELFP_RW_EXEC if data.exec
      raise RuntimeError.new "Unknown tag #{data.tag}" unless tag_ids.include? data.tag
      x.tag =   tag_ids[data.tag]
      print "#{x.from} to #{x.to} data #{data.tag} = #{x.tag} #{data.read ? "r":" "}#{data.write ? "w":" "}#{data.exec ? "x":" "}\n" 
    }
  end
  out = Elf::ProgBits.new(".elfbac",nil,out.to_binary_s)
  out.align = 8
  out.flags = SHF::SHF_ALLOC | SHF::SHF_WRITE
  out.sect_type = SHT::SHT_PROGBITS
  out.phdr = ElfFlags::PhdrType::PT_ELFBAC
  out.phdr_flags =  ElfFlags::PhdrFlags::PF_R
  relocations.each { |rel|
    rel.section = out
    elffile.relocations << rel
  }
  elffile.progbits << out
  
end