reference_monitor_adj329.r2py

#adj329

INVBUFFER = []
PERBUFFER = []
# Creating the locks for INV and PER both
mycontext['INVbufferlock'] = createlock()
mycontext['PERbufferlock'] = createlock()

# Loading the INV and PER buffers with locking mechanism
for filename in listfiles():
  if filename.startswith("private_"):
    fr = openfile(filename, False)
    
    if fr.readat(3,0) == "INV": # read
      mycontext['INVbufferlock'].acquire(bool(1)) 
      INVBUFFER.append(filename)
      mycontext['INVbufferlock'].release()
    
    elif fr.readat(3,0) == "PER": # read
      
      mycontext['PERbufferlock'].acquire(bool(1)) 
      PERBUFFER.append(filename)
      mycontext['PERbufferlock'].release() 
    fr.close()


class SecureFile():

  def __init__(self, file, filename):
    self.file = file
    self.filename = filename
    self.filelock = createlock() # create a file lock while initializing
    
  def readat(self, sizelimit, offset):
    
    # offset minimum value must be 0, its value cannot be less than 0
    if offset < 0:
      raise RepyArgumentError("\n Offset minimum value must be 0")
    else:
      return self.file.readat(sizelimit, offset)


  def writeat(self, data, offset):
  
    # offset minimum value must be 0, its value cannot be less than 0
    if offset < 0 or len(data) <= 0:
      raise RepyArgumentError("\n Sorry error while writting to file 1\n")
    else:
      self.filelock.acquire(True)
      fileWrite = self.file.writeat(data, offset)
      data = self.file.readat(3,0)
      self.filelock.release()

      if self.filename.startswith("private_"):
        
        if data == "INV":
          #acquiring the lock on buffer INV
          mycontext['INVbufferlock'].acquire(bool(1)) 
          INVBUFFER.append(self.filename)
          
          # remove the file from the PERBUFFER if it exists
          try:
            mycontext['PERbufferlock'].acquire(bool(1)) 
            if self.filename in PERBUFFER:
              PERBUFFER.remove(self.filename) # check file in per buffer
              
            mycontext['PERbufferlock'].release()  
            mycontext['INVbufferlock'].release() 
          except ValueError:
            mycontext['PERbufferlock'].release()
            mycontext['INVbufferlock'].release()  
            #self.filelock.release()
          else:
           #self.filelock.release()

            # we are writting new data to file so if writting INV, we have to remove the file from PERBuffer
            if self.filename in PERBUFFER:
              mycontext['PERbufferlock'].acquire(bool(1)) 
              PERBUFFER.remove(self.filename)        
              mycontext['PERbufferlock'].release() 

          return (fileWrite)
          
        elif data == "PER":
          mycontext['PERbufferlock'].acquire(bool(1)) 
          PERBUFFER.append(self.filename)
            # remove the file from the INVBUFFER if it exists
          try:
            mycontext['INVbufferlock'].acquire(bool(1)) 
            if self.filename in INVBUFFER:
              INVBUFFER.remove(self.filename)
            mycontext['PERbufferlock'].release()
            mycontext['INVbufferlock'].release()
          except ValueError:
            mycontext['PERbufferlock'].release()
            mycontext['INVbufferlock'].release()
              
            #self.filelock.release()
          else:
            #self.filelock.release()

            # we are writting new data to file so if writting INV, we have to remove the file from INVBuffer
            if filename in INVBUFFER:
              mycontext['INVbufferlock'].acquire(bool(1)) 
              INVBUFFER.remove(self.filename)
              mycontext['INVbufferlock'].release()

          return fileWrite
          
        else:

          # This will be executed if the attacker tries to change the filename and removes private
          mycontext['INVbufferlock'].acquire(bool(1)) 
          if ((not self.filename.startswith("private_")) and self.filename in INVBUFFER):
            INVBUFFER.remove(self.filename)
          mycontext['INVbufferlock'].release()

          mycontext['PERbufferlock'].acquire(bool(1)) 
          if ((not self.filename.startswith("private_")) and self.filename in PERBUFFER):
            PERBUFFER.remove(self.filename)
          mycontext['PERbufferlock'].release()

          # Normal write to the private file
          return fileWrite
      else:
        return fileWrite

                
  def close(self):
    return self.file.close()

def secure_openfile(filename, create):
  if filename.isupper() == False:
    file = openfile(filename, create)
  
    return SecureFile(file, filename)
  else:
    raise RepyArgumentError("\n Filename should only contain lowercase letters\n")


def secure_removefile(filename):
  #updatebuffer(filename)
  if filename in PERBUFFER:
    raise RepyArgumentError("Cannot delete this file!\n")
  removefile(filename) 



def secure_listfiles():
  filelist = listfiles()
  returnlist = []

  for filename in filelist:
    #updatebuffer(filename)
    if filename in INVBUFFER:
      continue
    returnlist.append(filename)
  return returnlist

def secure_removefile(filename):
  #updatebuffer(filename)
  if filename in PERBUFFER:
    raise RepyArgumentError("Cannot delete this file!\n")
  removefile(filename)

# 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":SecureFile,
  "name":"SecureFile",
  "readat":{"type":"func","args":((int,long,type(None)),(int,long)),"exceptions":Exception,"return":str,"target":SecureFile.readat},
  "writeat":{"type":"func","args":(str,(int,long)),"exceptions":Exception,"return":(None),"target":SecureFile.writeat},
  "close":{"type":"func","args":None,"exceptions":None,"return":(bool,type(None)),"target":SecureFile.close}
  }

CHILD_CONTEXT_DEF["openfile"] = {"type":"objc",
                                 "args":(str,bool),
                                 # any? why Exception in particular?
                                 "exceptions":Exception,
                                 "return":sec_file_def,
                                 "target":secure_openfile
                                }

CHILD_CONTEXT_DEF["listfiles"] = {"type":"func",
                                  "args":None,
                                  "return":list,
                                  "exceptions":"any",
                                  "target":secure_listfiles
                                 }

CHILD_CONTEXT_DEF["removefile"] = {"type":"func",
                                   "args":(str,),
                                   "return":None,
                                   "exceptions":"any",
                                   "target":secure_removefile
                                  }

# Execute the user code
secure_dispatch_module()