reference_monitor_ns5407.r2py

"""
This security layer inadequately handles LeftPad writeat()s that strictly append



Note:
    This security layer uses encasementlib.r2py, restrictions.default, repy.py and Python
    Also you need to give it an application to run.
    python repy.py restrictions.default encasementlib.r2py [security_layer].r2py [attack_program].r2py 
    
    """ 
TYPE="type"
ARGS="args"
RETURN="return"
EXCP="exceptions"
TARGET="target"
FUNC="func"
OBJC="objc"

o = createlock()

class LPFile():
  def __init__(self,filename,create):
    self.LPfile = openfile(filename,create)
    self.length = len(self.LPfile.readat(None,0))

  def readat(self, bytes, offset):
    o.acquire(True)

    read_output = ""
    try:
      read_output = self.LPfile.readat(bytes, offset)
    except:
      raise
    finally:
      o.release()

    return read_output

  def writeat(self, data, offset):
    o.acquire(True)
    try:   
      if offset == self.length:
      
        if '\n' not in data:
          self.LPfile.writeat(data,offset)
          self.length = max(self.length,len(data)+offset)
        
        elif '\n' in data:
          counter = data.count('\n')
          if counter > 1:
            raise RepyArgumentError
          else:
           loc = data.find('\n')
           self.LPfile.writeat(data[:(loc+1)]+"    "+data[(loc+1):],offset)
           self.length = len(data)+offset+4
   
      else:
          self.LPfile.writeat(data,offset)
          self.length = max(offset+len(data),self.length)
    except:
      raise
    finally:
      o.release()  

  
  def close(self):
    self.LPfile.close()


def LPopenfile(filename, create):
  return LPFile(filename,create)




# The code here sets up type checking and variable hiding for you.  You
# should not need to change anything below here.
sec_file_def = {"obj-type":LPFile,
                "name":"LPFile",
                "writeat":{"type":"func","args":(str,(int,long)),"exceptions":Exception,"return":(int,type(None)),"target":LPFile.writeat},
                "readat":{"type":"func","args":((int,long,type(None)),(int,long)),"exceptions":Exception,"return":str,"target":LPFile.readat},
                "close":{"type":"func","args":None,"exceptions":None,"return":(bool,type(None)),"target":LPFile.close}
           }

CHILD_CONTEXT_DEF["openfile"] = {TYPE:OBJC,ARGS:(str,bool),EXCP:Exception,RETURN:sec_file_def,TARGET:LPopenfile}

# Execute the user code
secure_dispatch_module()