[Python-Dev] Counting collisions for the win (original) (raw)

David Malcolm dmalcolm at redhat.com
Sat Jan 21 21:22:34 CET 2012

On Fri, 2012-01-20 at 16:55 +0100, Frank Sievertsen wrote:

Hello,

I still see at least two ways to create a DOS attack even with the collison-counting-patch.

[snip description of two types of attack on the collision counting approach]

What to do now? I think it's not smart to reduce the number of allowed collisions dramatically AND count all slot-collisions at the same time.

Frank: did you see the new approach I proposed in: http://bugs.python.org/issue13703#msg151735 http://bugs.python.org/file24289/amortized-probe-counting-dmalcolm-2012-01-21-003.patch

(repurposes the ma_smalltable region of large dictionaries to add tracking of each such dict's average iterations taken per modification, and raise an exception when it exceeds a particular ratio)

I'm interested in hearing how it holds up against your various test cases, or what flaws there are in it.

Thanks! Dave

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