# Cerealizer # Copyright (C) 2005-2006 Jean-Baptiste LAMY # # This program is free software. # It is available under the Python licence. """Cerealizer -- A secure Pickle-like module The interface of the Cerealizer module is similar to Pickle, and it supports __getstate__, __setstate__, __getinitargs__ and __getnewargs__. Cerealizer supports int, long, float, bool, complex, string, unicode, tuple, list, set, frozenset, dict, old-style and new-style class instances. C-defined types are supported but saving the C-side data may require to write e.g. a specific Handler or a __getstate__ and __setstate__ pair. Objects with __slots__ are supported too. You have to register the class you want to serialize, by calling cerealizer.register(YourClass). Cerealizer can be considered as secure AS LONG AS the following methods of 'YourClass' are secure: - __new__ - __del__ - __getstate__ - __setstate__ - __init__ (ONLY if __getinitargs__ is used for the class) These methods are the only one Cerealizer may call. For a higher security, Cerealizer maintains its own reference to these method (exepted __del__ that can only be called indirectly). Cerealizer doesn't aim at producing Human-readable files. About performances, Cerealizer is really fast and, when powered by Psyco, it may even beat cPickle! Although Cerealizer is implemented in less than 500 lines of pure-Python code (which is another reason for Cerealizer to be secure, since less code means less bugs :-). Compared to Pickle (cPickle): - Cerealizer is secure - Cerealizer achieves similar performances (using Psyco) - Cerealizer requires you to declare the serializable classes Compared to Jelly (from TwistedMatrix): - Cerealizer is faster - Cerealizer does a better job with object cycles, C-defined types and tuples (*) - Cerealizer files are not Human readable (*) Jelly handles them, but tuples and objects in a cycle are first created as _Tuple or _Dereference objects; this works for Python classes, but not with C-defined types which expects a precise type (e.g. tuple and not _Tuple). IMPLEMENTATION DETAILS GENERAL FILE FORMAT STRUCTURE Cerealizer format is simple but quite surprising. It uses a "double flat list" format. It looks like that : \\n \\n \\n \\n [...] [...] As you can see, the information for a given object is splitted in two parts, the first one for object's class, and the second one for the object's data. To avoid problems, the order of the objects is the following: Objects are put after basic types (list,...), since object's __setstate__ might rely on a list, and thus the list must be fully loaded BEFORE calling the object's __setstate__. DATA ( above) The part saves the data of object #n. It may contains reference to other data (see below, in Cerealizer references include reference to other objects but also raw data like int). - an object is saved by : e.g. 'r7\\n' (object #7 being e.g. the __dict__). - a list or a set is saved by : \\n [...] e.g. '3\\ni0\\ni1\\ni2\\n' for [0, 1, 2] - a dict is saved by : \\n [...] REFERENCES ( above) In Cerealizer a reference can be either a reference to another object beign serialized in the same file, or a raw value (e.g. an integer). - an int is saved by e.g. 'i187\\n' - a long is saved by e.g. 'l10000000000\\n' - a float is saved by e.g. 'f1.07\\n' - a bool is saved by 'b0' or 'b1' - a string is saved by e.g. 's5\\nascii' (where 5 is the number of characters) - an unicode is saved by e.g. 'u4\\nutf8' (where 4 is the number of characters) - an object reference is saved by e.g. 'r3\\n' (where 3 means reference to object #3) - None is saved by 'n' """ __alls__ = ["load", "dump", "loads", "dumps", "freeze_configuration", "register"] VERSION = "0.5" import logging logger = logging.getLogger("cerealizer") #logging.basicConfig(level=logging.INFO) from cStringIO import StringIO from new import instance class NotCerealizerFileError(StandardError): pass class NonCerealizableObjectError(StandardError): pass def _priority_sorter(a, b): return cmp(a[0], b[0]) class Dumper(object): def dump(self, root_obj, s): self.objs = [] self.objs_id = set() self.priorities_objs = [] # [(priority1, obj1), (priority2, obj2),...] self.obj2state = {} self.obj2newargs = {} self.id2id = {} self.collect(root_obj) self.priorities_objs.sort(_priority_sorter) self.objs.extend([o for (priority, o) in self.priorities_objs]) s.write("cereal1\n%s\n" % len(self.objs)) i = 0 for obj in self.objs: self.id2id[id(obj)] = i i += 1 for obj in self.objs: _HANDLERS_[obj.__class__].dump_obj (obj, self, s) for obj in self.objs: _HANDLERS_[obj.__class__].dump_data(obj, self, s) _HANDLERS_[root_obj.__class__].dump_ref(root_obj, self, s) def undump(self, s): if s.read(8) != "cereal1\n": raise NotCerealizerFileError("Not a cerealizer file!") nb = int(s.readline()) self.id2obj = [ None ] * nb # DO NOT DO self.id2obj = [comprehension list], since undump_ref may access id2obj during its construction for i in range(nb): classname = s.readline() handler = _HANDLERS.get(classname) if not handler: raise NonCerealizableObjectError("Object of class/type '%s' cannot be de-cerealized! Use cerealizer.register to extend Cerealizer support to other classes." % classname[:-1]) self.id2obj[i] = handler.undump_obj(self, s) for obj in self.id2obj: _HANDLERS_[obj.__class__].undump_data(obj, self, s) return self.undump_ref(s) def collect(self, obj): """Dumper.collect(OBJ) -> bool Collects OBJ for serialization. Returns false is OBJ is already collected; else returns true.""" handler = _HANDLERS_.get(obj.__class__) if not handler: raise NonCerealizableObjectError("Object of class/type '%s' cannot be cerealized! Use cerealizer.register to extend Cerealizer support to other classes." % obj.__class__) handler.collect(obj, self) def dump_ref (self, obj, s): """Dumper.dump_ref(OBJ, S) Writes a reference to OBJ in file S.""" _HANDLERS_[obj.__class__].dump_ref(obj, self, s) def undump_ref(self, s): """Dumper.undump_ref(S) -> obj Reads a reference from file S.""" c = s.read(1) if c == "i": return int (s.readline()) elif c == "f": return float(s.readline()) elif c == "s": return s.read(int(s.readline())) elif c == "u": return s.read(int(s.readline())).decode("utf8") elif c == "r": return self.id2obj[int(s.readline())] elif c == "n": return None elif c == "b": return bool(int(s.read(1))) elif c == "l": return long(s.readline()) elif c == "c": return complex(s.readline()) raise ValueError("Unknown ref code '%s'!" % c) def immutable_depth(self, t): depth = 0 for i in t: i2 = self.obj2newargs.get(id(i)) if not i2 is None: i = i2 if isinstance(i, tuple) or isinstance(i, frozenset): x = self.immutable_depth(i) if x > depth: depth = x return depth + 1 class Handler(object): """Handler A customized handler for serialization and deserialization. You can subclass it to extend cerealization support to new object. See also ObjHandler.""" def collect(self, obj, dumper): """Handler.collect(obj, dumper) -> bool Collects all the objects referenced by OBJ. For each objects ROBJ referenced by OBJ, calls collect method of the Handler for ROBJ's class, i.e._HANDLERS_[ROBJ.__class__].collect(ROBJ, dumper). Returns false if OBJ is already referenced (and thus no collection should occur); else returns true. """ i = id(obj) if not i in dumper.objs_id: dumper.objs.append(obj) dumper.objs_id.add(i) return 1 def dump_obj (self, obj, dumper, s): """Handler.dump_obj(obj, dumper, s) Dumps OBJ classname in file S.""" s.write(self.classname) def dump_data(self, obj, dumper, s): """Handler.dump_data(obj, dumper, s) Dumps OBJ data in file S.""" def dump_ref (self, obj, dumper, s): """Handler.dump_ref(obj, dumper, s) Write a reference to OBJ in file S. You should not override dump_ref, since they is no corresponding 'undump_ref' that you can override.""" s.write("r%s\n" % dumper.id2id[id(obj)]) def undump_obj(self, dumper, s): """Handler.undump_obj(dumper, s) Returns a new uninitialized (=no __init__'ed) instance of the class. If you override undump_obj, DUMPER and file S can be used to read additional data saved by Handler.dump_obj().""" def undump_data(self, obj, dumper, s): """Handler.undump_data(obj, dumper, s) Reads the data for OBJ, from DUMPER and file S. If you override undump_data, you should use DUMPER.undump_ref(S) to read a reference or a basic type (=a string, an int,...).""" class RefHandler(object): def collect (self, obj, dumper) : pass def dump_obj (self, obj, dumper, s): pass def dump_data(self, obj, dumper, s): pass class NoneHandler(RefHandler): def dump_ref (self, obj, dumper, s): s.write("n") class StrHandler(RefHandler): def dump_ref (self, obj, dumper, s): s.write("s%s\n%s" % (len(obj), obj)) class UnicodeHandler(RefHandler): def dump_ref (self, obj, dumper, s): obj = obj.encode("utf8") s.write("u%s\n%s" % (len(obj), obj)) class BoolHandler(RefHandler): def dump_ref (self, obj, dumper, s): s.write("b%s" % int(obj)) class IntHandler(RefHandler): def dump_ref (self, obj, dumper, s): s.write("i%s\n" % obj) class LongHandler(RefHandler): def dump_ref (self, obj, dumper, s): s.write("l%s\n" % obj) class FloatHandler(RefHandler): def dump_ref (self, obj, dumper, s): s.write("f%s\n" % obj) class ComplexHandler(RefHandler): def dump_ref (self, obj, dumper, s): c = str(obj) if c.startswith("("): c = c[1:-1] # complex("(1+2j)") doesn't work s.write("c%s\n" % c) class TupleHandler(Handler): classname = "tuple\n" def collect(self, obj, dumper): if not id(obj) in dumper.objs_id: dumper.priorities_objs.append((dumper.immutable_depth(obj), obj)) dumper.objs_id.add(id(obj)) for i in obj: dumper.collect(i) return 1 def dump_obj(self, obj, dumper, s): s.write("%s%s\n" % (self.classname, len(obj))) for i in obj: _HANDLERS_[i.__class__].dump_ref(i, dumper, s) def undump_obj(self, dumper, s): return tuple([dumper.undump_ref(s) for i in range(int(s.readline()))]) class FrozensetHandler(TupleHandler): classname = "frozenset\n" def undump_obj(self, dumper, s): return frozenset([dumper.undump_ref(s) for i in range(int(s.readline()))]) class ListHandler(Handler): classname = "list\n" def collect(self, obj, dumper): if Handler.collect(self, obj, dumper): for i in obj: dumper.collect(i) return 1 def dump_data(self, obj, dumper, s): s.write("%s\n" % len(obj)) for i in obj: _HANDLERS_[i.__class__].dump_ref(i, dumper, s) def undump_obj(self, dumper, s): return [] def undump_data(self, obj, dumper, s): for i in range(int(s.readline())): obj.append(dumper.undump_ref(s)) class SetHandler(ListHandler): classname = "set\n" def undump_obj(self, dumper, s): return set() def undump_data(self, obj, dumper, s): for i in range(int(s.readline())): obj.add(dumper.undump_ref(s)) class DictHandler(Handler): classname = "dict\n" def collect(self, obj, dumper): if Handler.collect(self, obj, dumper): for i in obj.iterkeys (): dumper.collect(i) # Collect is not ordered for i in obj.itervalues(): dumper.collect(i) return 1 def dump_data(self, obj, dumper, s): s.write("%s\n" % len(obj)) for k, v in obj.iteritems(): _HANDLERS_[v.__class__].dump_ref(v, dumper, s) # Value is saved fist _HANDLERS_[k.__class__].dump_ref(k, dumper, s) def undump_obj(self, dumper, s): return {} def undump_data(self, obj, dumper, s): for i in range(int(s.readline())): obj[dumper.undump_ref(s)] = dumper.undump_ref(s) # Value is read fist class ObjHandler(Handler): """ObjHandler A Cerealizer Handler that can support any new-style class instances, old-style class instances as well as C-defined types (although it may not save the C-side data).""" def __init__(self, Class, classname = ""): self.Class = Class self.Class_new = getattr(Class, "__new__" , instance) self.Class_getstate = getattr(Class, "__getstate__", None) # Check for and store __getstate__ and __setstate__ now self.Class_setstate = getattr(Class, "__setstate__", None) # so we are are they are not modified in the class or the object if classname: self.classname = "%s\n" % classname else: self.classname = "%s.%s\n" % (Class.__module__, Class.__name__) def collect(self, obj, dumper): i = id(obj) if not i in dumper.objs_id: dumper.priorities_objs.append((-1, obj)) dumper.objs_id.add(i) if self.Class_getstate: state = self.Class_getstate(obj) else: state = obj.__dict__ dumper.obj2state[i] = state dumper.collect(state) return 1 def dump_data(self, obj, dumper, s): i = dumper.obj2state[id(obj)] _HANDLERS_[i.__class__].dump_ref(i, dumper, s) def undump_obj(self, dumper, s): return self.Class_new(self.Class) def undump_data(self, obj, dumper, s): if self.Class_setstate: self.Class_setstate(obj, dumper.undump_ref(s)) else: obj.__dict__ = dumper.undump_ref(s) class SlotedObjHandler(ObjHandler): """SlotedObjHandler A Cerealizer Handler that can support new-style class instances with __slot__.""" def __init__(self, Class, classname = ""): ObjHandler.__init__(self, Class, classname) self.Class_slots = Class.__slots__ def collect(self, obj, dumper): i = id(obj) if not i in dumper.objs_id: dumper.priorities_objs.append((-1, obj)) dumper.objs_id.add(i) if self.Class_getstate: state = self.Class_getstate(obj) else: state = dict([(slot, getattr(obj, slot, None)) for slot in self.Class_slots]) dumper.obj2state[i] = state dumper.collect(state) return 1 def undump_data(self, obj, dumper, s): if self.Class_setstate: self.Class_setstate(obj, dumper.undump_ref(s)) else: state = dumper.undump_ref(s) for slot in self.Class_slots: setattr(obj, slot, state[slot]) class InitArgsObjHandler(ObjHandler): """InitArgsObjHandler A Cerealizer Handler that can support class instances with __getinitargs__.""" def __init__(self, Class, classname = ""): ObjHandler.__init__(self, Class, classname) self.Class_getinitargs = Class.__getinitargs__ self.Class_init = Class.__init__ def collect(self, obj, dumper): i = id(obj) if not i in dumper.objs_id: dumper.priorities_objs.append((-1, obj)) dumper.objs_id.add(i) dumper.obj2state[i] = state = self.Class_getinitargs(obj) dumper.collect(state) return 1 def undump_data(self, obj, dumper, s): self.Class_init(obj, *dumper.undump_ref(s)) class NewArgsObjHandler(ObjHandler): """NewArgsObjHandler A Cerealizer Handler that can support class instances with __getnewargs__.""" def __init__(self, Class, classname = ""): ObjHandler.__init__(self, Class, classname) self.Class_getnewargs = Class.__getnewargs__ def collect(self, obj, dumper): i = id(obj) if not i in dumper.objs_id: dumper.obj2newargs[i] = newargs = self.Class_getnewargs(obj) dumper.collect(newargs) dumper.priorities_objs.append((dumper.immutable_depth(newargs), obj)) dumper.objs_id.add(i) if self.Class_getstate: state = self.Class_getstate(obj) else: state = obj.__dict__ dumper.obj2state[i] = state dumper.collect(state) return 1 def dump_obj (self, obj, dumper, s): s.write(self.classname) newargs = dumper.obj2newargs[id(obj)] _HANDLERS_[newargs.__class__].dump_ref(newargs, dumper, s) def undump_obj(self, dumper, s): return self.Class_new(self.Class, *dumper.undump_ref(s)) _configurable = 1 _HANDLERS = {} _HANDLERS_ = {} def register(Class, handler = None, classname = ""): """register(Class, handler = None, classname = "") Registers CLASS as a serializable and secure class. By calling register, YOU HAVE TO ASSUME THAT THE FOLLOWING METHODS ARE SECURE: - CLASS.__new__ - CLASS.__del__ - CLASS.__getstate__ - CLASS.__setstate__ - CLASS.__getinitargs__ - CLASS.__init__ (only if CLASS.__getinitargs__ exists) HANDLER is the Cerealizer Handler object that handles serialization and deserialization for Class. If not given, Cerealizer create an instance of ObjHandler, which is suitable for old-style and new_style Python class, and also C-defined types (although if it has some C-side data, you may have to write a custom Handler or a __getstate__ and __setstate__ pair). CLASSNAME is the classname used in Cerealizer files. It defaults to the full classname (module.class) but you may choose something shorter -- as long as there is no risk of name clash.""" if not _configurable: raise StandardError("Cannot register new classes after freeze_configuration has been called!") if "\n" in classname: raise ValueError("CLASSNAME cannot have \\n (Cerealizer automatically add a trailing \\n for performance reason)!") if not handler: if hasattr(Class, "__getnewargs__" ): handler = NewArgsObjHandler (Class, classname) elif hasattr(Class, "__getinitargs__"): handler = InitArgsObjHandler(Class, classname) elif hasattr(Class, "__slots__" ): handler = SlotedObjHandler (Class, classname) else: handler = ObjHandler (Class, classname) if _HANDLERS_.has_key(Class): raise ValueError("Class %s has already been registred!" % Class) if not isinstance(handler, RefHandler): if _HANDLERS .has_key(handler.classname): raise ValueError("A class has already been registred under the name %s!" % handler.classname[:-1]) _HANDLERS [handler.classname] = handler if handler.__class__ is ObjHandler: logger.info("Registring class %s as '%s'" % (Class, handler.classname[:-1])) else: logger.info("Registring class %s as '%s' (using %s)" % (Class, handler.classname[:-1], handler.__class__.__name__)) else: logger.info("Registring reference '%s'" % Class) _HANDLERS_[Class] = handler register_class = register # For backward compatibility def register_alias(Class, alias): """register_alias(Class, alias) Registers ALIAS as an alias classname for CLASS. Usefull for keeping backward compatibility in files: e.g. if you have renamed OldClass to NewClass, just do: cerealizer.register_alias(NewClass, "OldClass") and you'll be able to open old files containing OldClass serialized.""" handler = _HANDLERS_.get(Class) if not handler: raise ValueError("Cannot register alias '%s' to Class %s: the class is not yet registred!" % (alias, Class)) if _HANDLERS.has_key(alias): raise ValueError("Cannot register alias '%s' to Class %s: another class is already registred under the alias name!" % (alias, Class)) logger.info("Registring alias '%s' for %s" % (alias, Class)) _HANDLERS[alias + "\n"] = handler def freeze_configuration(): """freeze_configuration() Ends Cerealizer configuration. When freeze_configuration() is called, it is no longer possible to register classes, using register(). Calling freeze_configuration() is not mandatory, but it may enforce security, by forbidding unexpected calls to register().""" global _configurable _configurable = 0 logger.info("Configuration frozen") register(type(None), NoneHandler ()) register(str , StrHandler ()) register(unicode , UnicodeHandler ()) register(bool , BoolHandler ()) register(int , IntHandler ()) register(long , LongHandler ()) register(float , FloatHandler ()) register(complex , ComplexHandler ()) register(dict , DictHandler ()) register(list , ListHandler ()) register(set , SetHandler ()) register(tuple , TupleHandler ()) register(frozenset , FrozensetHandler()) def dump(obj, file, protocol = 0): """dump(obj, file, protocol = 0) Serializes object OBJ in FILE. PROTOCOL is unused, it exists only for compatibility with Pickle.""" Dumper().dump(obj, file) def load(file): """load(file) -> obj De-serializes an object from FILE.""" return Dumper().undump(file) def dumps(obj, protocol = 0): """dumps(obj, protocol = 0) -> str Serializes object OBJ and returns the serialized string. PROTOCOL is unused, it exists only for compatibility with Pickle.""" s = StringIO() Dumper().dump(obj, s) return s.getvalue() def loads(string): """loads(file) -> obj De-serializes an object from STRING.""" return Dumper().undump(StringIO(string)) def dump_class_of_module(*modules): """dump_class_of_module(*modules) Utility function; for each classes found in the given module, print the needed call to register.""" class D: pass class O(object): pass s = set([c for module in modules for c in module.__dict__.values() if isinstance(c, type(D)) or isinstance(c, type(O))]) l = ['cerealizer.register(%s.%s)' % (c.__module__, c.__name__) for c in s] l.sort() for i in l: print i