On Mon, 03 Aug 2009 21:34:15 -0700, Paul Rubin wrote: > Steven D'Aprano <ste...@remove.this.cybersource.com.au> writes: >> > The Python interpreter is written in C. Python extension modules are >> > written in C (or something similar). If you find an unprotected >> > buffer in this C code, you can possibly overflow this buffer. >> >> How are C extension modules "_pure_ python"? > > A lot of basic Python constructs (like numbers and dictionaries) are > implemented as C extension modules. It is reasonable to consider "pure > Python" to include the contents of the Python standard library.
Well, yes, but we're not saying that Python is bug-free. There could be bugs in the Python VM for that matter. The point is that code you write yourself can rely on "pure Python" to be free of buffer-overflows (for some definition of "rely") rather than having to worry about managing memory yourself. If you do this: buffer = [0]*1024 buffer[:] = [1]*1025 you don't over-write some random piece of memory, the list object resizes to accommodate, or fails with an exception instead. No special action is needed to avoid buffer overflows. You can't make that claim about C extensions. It's interesting to contrast that with DoS vulnerabilities in pure Python code. Python won't stop you from trying to calculate a googolplex: googol = 10**100 googolplex = 10**googol and doing so will be a moderately effective denial of service against your Python application. If you're concerned with that, you need to code defensively in the Python layer. Protecting against time-consuming operations is not part of Python's design. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
