[ih] SIP and ENUM

John Levine johnl at iecc.com
Wed Jul 8 14:14:42 PDT 2020

In article <7498b3fd-cc55-2de3-3c56-2c89e430289e at cavebear.com> you write:
>As for Enum - that has always scared me.  I am made nervous by the 
>notion that DNS clients would evaluate j-random regular expressions 
>found in NAPTR records.   That strikes me not much different than the 
>security problems we have had with web browsers evaluating random 
>Javascript fed to them by websites.

I don't understand this concern. Even the most complicated regex is
only a pattern that either matches or doesn't, with well understood
mathematical properties. It doesn't have loops or subroutines, and
since we have fifty years of experience with regex matching, we know
how to handle them efficiently.

It's certainly easy enough to write a regex that is wrong, but not one
that is dangerous.


PS: If you haven't kept up with the literature, current regex matchers
generally don't complle them into 7094 machine code any more.

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