Re: Random seed and possible blocking of /dev/random

[Richard Levitte - VMS Whacker]

From: Lutz Jaenicke <[EMAIL PROTECTED]>

Lutz.Jaenicke> On Fri, Jan 05, 2001 at 09:49:56PM +0100, Richard Levitte - VMS Whacker 
wrote:
Lutz.Jaenicke> I don't know how select() would act on a regular
Lutz.Jaenicke> file. /dev/random (and/or /dev/urandom) are no regular
Lutz.Jaenicke> files, so we could first call stat() and only continue
Lutz.Jaenicke> when S_ISCHR() is true (character device).

My question about regular files was with the thought that one could
hack RAND_load_file() with something similar.

Lutz.Jaenicke> > If select() is useable before read() for a standard
Lutz.Jaenicke> > file, then it would perhaps be possible to use
Lutz.Jaenicke> > possibly blocking devices like /dev/random and still
Lutz.Jaenicke> > not get impatient developpers on our throats :-).
Lutz.Jaenicke> Hmm, I would consider using non-blocking
Lutz.Jaenicke> reads. Select() does not know how many bytes you intend
Lutz.Jaenicke> to read, so it will return "available" if just one byte
Lutz.Jaenicke> is there and the second byte will block. Of course we
Lutz.Jaenicke> could read byte-per-byte...

That is a solution, but if we want to do reads with a timeout (say
20ms), that would mean a loop with a polling read with a definitely
higher frequency than we wold get with a select().  On the other hand,
non-blocking doesn't stop us from select()ing, does it?  Hmm, perhaps
it's a thought after all...

Lutz.Jaenicke> This brings me to related point. Would it make sense to
Lutz.Jaenicke> define a "default" place to look for an egd-socket? I
Lutz.Jaenicke> had several contacts with people using my prngd (egd
Lutz.Jaenicke> replacement) that installed prngd and did expect
Lutz.Jaenicke> openssl to magically find it.

That would be a good idea, I think.  Personally, I'd say
/etc/.egd-socket rather than /etc/egd-socket.  This removes some
possibilities for "accidents" as well.  Yes, this is security by
obscurity...

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