New submission from Sebastian Noack:
If I run following code (on Python 3.5.3, Linux) the interpreter crashes with a
segfault:
def pbkdf2_bin(data, salt, iterations=1000, keylen=24, hashfunc=None):
hashfunc = hashfunc or hashlib.sha1
mac = hmac.new(data, None, hashfunc)
def _pseudorandom(x, mac=mac):
h = mac.copy()
h.update(x)
return h.digest()
buf = []
for block in range(1, -(-keylen // mac.digest_size) + 1):
rv = u = _pseudorandom(salt + _pack_int(block))
for i in range(iterations - 1):
u = _pseudorandom(u)
rv = starmap(xor, zip(rv, u))
buf.extend(rv)
return bytes(buf[:keylen])
pbkdf2_bin(b'1234567890', b'1234567890', 200000, 32)
I was able to track it down to the line of buf.extend(rv) which apparently is
causing the segfault. Note that rv is a lazy-evaluated starmap. I also get a
segfault if I evaluate it by other means (e.g. by passing it to the list
constructor). However, if I evaluate it immediately by wrapping the starmap
constructor with the list constructor, the code works as expected. But I wasn't
able yet, to further isolate the issue. FWIW, the Python 2 version [1] of this
code works just fine without forcing immediate evaluation of the starmap.
Note that the code posted, except for the bits I changed in order to make it
compatible with Python 3, is under the copyright of Armin Ronacher, who
published it under the BSD license.
[1]: https://github.com/mitsuhiko/python-pbkdf2
----------
messages: 293192
nosy: Sebastian.Noack
priority: normal
severity: normal
status: open
title: Recursive starmap causes Segmentation fault
type: crash
versions: Python 3.5
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue30297>
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