Bugs item #1122301, was opened at 2005-02-14 03:14
Message generated for change (Comment added) made by nnorwitz
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Category: Python Library
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Fredrik Lundh (effbot)
Assigned to: Fredrik Lundh (effbot)
Summary: marshal may crash on truncated input
Initial Comment:
marshal doesn't behave well on truncated or otherwise
malformed input. here's a short demo script, from a
recent comp.lang.python thread:
:::
the problem is that the following may or may not reach
the "done!" statement, somewhat depending on python
version, memory allocator, and what data you pass to
dumps.
import marshal
data = marshal.dumps((1, 2, 3, "hello", 4, 5, 6))
for i in range(len(data), -1, -1):
try:
print marshal.loads(data[:i])
except EOFError:
print "EOFError"
except ValueError:
print "ValueError"
print "done!"
(try different data combinations, to see how far you get
on your platform...)
fixing this should be relatively easy, and should result in
a safe unmarshaller (your application will still have to
limit the amount of data fed into load/loads, of course).
:::
(also note that marshal may raise either EOFError or
ValueError exceptions, again somewhat depending on
how the file is damaged. a little consistency wouldn't
hurt, but I'm not sure if/how this can be fixed...)
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>Comment By: Neal Norwitz (nnorwitz)
Date: 2005-09-29 22:19
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This works in CVS, but still not in 2.4. I guess the patch
didn't get backported.
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Comment By: Michael Hudson (mwh)
Date: 2005-05-27 02:36
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Ping!
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Comment By: Michael Hudson (mwh)
Date: 2005-04-19 07:58
Message:
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I think the attached fixes this example, and another involving marshalled
sets.
I spent a while feeding random data to marshal a few days ago and found
that the commonest problem was attempting to allocate really huge
sequences. Also, the TYPE_STRINGREF is horribly fragile, but I'm
hoping Martin's going to fix that (he has a bug filed against him, anyway).
Can you test/check it in? My marshal.c has rather a lot of local changes.
Also, a test suite entry would be nice...
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