From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Geoghegan <pg@bowt.ie>
cc: Michael Paquier <michael@paquier.xyz>,
        Alvaro Herrera <alvherre@2ndquadrant.com>,
        Adrien Nayrat <adrien.nayrat@anayrat.info>,
        Thomas Munro <thomas.munro@enterprisedb.com>,
        Dmitry Dolgov <9erthalion6@gmail.com>,
        Tomas Vondra <tomas.vondra@2ndquadrant.com>,
        Vik Fearing <vik.fearing@2ndquadrant.com>,
        Robert Haas <robertmhaas@gmail.com>,
        David Rowley <david.rowley@2ndquadrant.com>,
        Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: random() (was Re: New GUC to sample log queries)
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Comments: In-reply-to Peter Geoghegan <pg@bowt.ie>
	message dated "Wed, 26 Dec 2018 18:55:08 -0800"
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Date: Thu, 27 Dec 2018 14:33:34 -0500
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Peter Geoghegan <pg@bowt.ie> writes:
> On Wed, Dec 26, 2018 at 6:39 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Now, we could probably fix that with some less intrusive patch than
>> #define'ing random() --- in particular, if we give drandom and setseed
>> their own private PRNG state, we've really fixed the security exposure
>> without need to change anything else anywhere.  So maybe we should
>> just do that and be happy.

> +1. I don't like the idea of #define'ing random() myself.

> We're already making fairly broad assumptions about our having control
> of the backend's PRNG state within InitProcessGlobals(). How should
> this affect the new drandom()/setseed() private state, if at all?

I would think that InitProcessGlobals would initialize drandom's
seed alongside random()'s seed.  Hopefully to values not easily
predictable from each other -- see also Munro's comment, which
I'll respond to in a moment.

			regards, tom lane