Am 29.12.2011 12:13, schrieb Mark Shannon: > The attack relies on being able to predict the hash value for a given > string. Randomising the string hash function is quite straightforward. > There is no need to change the dictionary code. > > A possible (*untested*) patch is attached. I'll leave it for those more > familiar with unicodeobject.c to do properly.
I'm worried that hash randomization of str is going to break 3rd party software that rely on a stable hash across multiple Python instances. Persistence layers like ZODB and cross interpreter communication channels used by multiprocessing may (!) rely on the fact that the hash of a string is fixed. Perhaps the dict code is a better place for randomization. The code in lookdict() and lookdict_unicode() could add a value to the hash. My approach is less intrusive and also closes the attack vector for all possible objects including str, byte, int and so on. I like also Armin's idea of an optional hash randomization. Christian _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
