netdev - Re: [PATCH] Re: [PATCH] drivers/net: remove network drivers' last few uses of IRQF_SAMPLE

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Message-ID: <20080517130535.02d45372@infradead.org>
Date:	Sat, 17 May 2008 13:05:35 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	"Chris Peterson" <cpeterso@...terso.com>
Cc:	"Andi Kleen" <andi@...stfloor.org>,
	"Herbert Xu" <herbert@...dor.apana.org.au>,
	"Alan Cox" <alan@...rguk.ukuu.org.uk>,
	"Jeff Garzik" <jeff@...zik.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	tpmdd-devel@...ts.sourceforge.net, tpm@...horst.net
Subject: Re: [PATCH] Re: [PATCH] drivers/net: remove network drivers' last
 few uses of IRQF_SAMPLE_RANDOM

On Sat, 17 May 2008 12:54:02 -0700
"Chris Peterson" <cpeterso@...terso.com> wrote:

> Andi, can you please clarify what you mean by "auto-feeding
> /dev/urandom only" and "only get blocking /dev/random with the user
> daemon"? Are you suggesting that the kernel provides /dev/urandom and
> a userspace daemon (e.g. EGD) provides /dev/random?
> 
> Also, if crypto apps like ssh and openssl use on "insecure"
> /dev/urandom, then who actually relies on /dev/random?

gpg does for key generation

> For comparison,
> FreeBSD does not even (AFAIK) have /dev/urandom. FreeBSD's /dev/random
> is nonblocking (like Linux's /dev/urandom) and includes network
> entropy.
> 

I think the big kicker is the difference between a session key (short
lived) and a "real" key such as a gpg key that lives for a long time
and is used for multile sessions and with different users (in crypto
speak, Alice uses the same random key for Bob, Charlotte and David and
potentially for a long time). For a session key, urandom is very likely
an acceptable compromise; there's only so much data it's used for.
For long term keys I can totally see why /dev/random is used instead.

So both have value, just in different circumstances.
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