New submission from Edward Pilatowicz <edward.pilatow...@oracle.com>:
recently i was writing some python code that attempted to bind a unix domain socket to a long filesystem path. this code was failing and telling me that the path name was too long. tracing python i saw that it wasn't event issuing a system call for my bind() request. eventually i tracked down the problem to socketmodule.c`getsockaddrarg(): http://svn.python.org/view/python/trunk/Modules/socketmodule.c?view=markup there we see that getsockaddrarg() checks to verify that the specified path is less than "sizeof addr->sun_path", where addr is a struct sockaddr_un. this seems incorrect to me. on most systems sockaddr_un.sun_path is defined as a small character array. this limit is an ancient bit of unix legacy and most modern systems do not actually limit domain socket names to a path as short as sun_path. on solaris the real limit is MAXPATHLEN, there by allowing unix domain sockets to be bound to any filesystem path. the posix specification also says that users of the sockaddr_un structure should not make any assumptions about the maximum supported length of sun_path. from: http://www.opengroup.org/onlinepubs/009695399/basedefs/sys/un.h.html we have: char sun_path[] socket pathname ... The size of sun_path has intentionally been left undefined. This is because different implementations use different sizes. For example, 4.3 BSD uses a size of 108, and 4.4 BSD uses a size of 104. Since most implementations originate from BSD versions, the size is typically in the range 92 to 108. Applications should not assume a particular length for sun_path or assume that it can hold {_POSIX_PATH_MAX} characters (255). hence, it seems to me that python should not actually be doing any size checks on the path passed to getsockaddrarg(). instead is should dynamically allocate a sockaddr_un large enough to hold whatever string was pass in. this structure can then be passed on to system calls which can they check if the specified path is of a supported length. (if you look at the posix definitions for bind() and connect() you'll see that they both can return ENAMETOOLONG if the passed in pathname is too large.) ---------- components: None messages: 106929 nosy: Edward.Pilatowicz priority: normal severity: normal status: open title: socketmodule.c`getsockaddrarg() should not check the length of sun_path type: behavior versions: Python 2.6 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue8882> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
