Messages in this thread | | | Date | Sat, 11 Dec 2004 12:40:29 -0800 | From | Matt Mackall <> | Subject | Re: Concurrent access to /dev/urandom |
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On Sat, Dec 11, 2004 at 01:58:45PM -0600, Adam Heath wrote: > On Sat, 11 Dec 2004, Theodore Ts'o wrote: > > > On Fri, Dec 10, 2004 at 06:22:37PM -0600, Adam Heath wrote: > > > > > > Actually, I think this is a security issue. Since any plain old program can > > > read from /dev/urandom at any time, an attacker could attempt to read from > > > that device at the same moment some other program is doing so, and thereby > > > gain some knowledge as to the other program's state. > > > > It could be a potential exploit, but.... > > > > (a) it only applies on SMP machines > > (b) it's not a remote exploit; the attacker needs to have > > the ability to run arbitrary programs on the local > > machine > > (c) the attacker won't get all of other programs' reads of > > /dev/urandom, and > > (d) the attacker would have to have a program continuously > > reading from /dev/urandom, which would take up enough > > CPU time that it would be rather hard to hide. > > > > That's not to say that we shouldn't fix it at our earliest > > convenience, and I'd urge Andrew to push this to Linus for 2.6.10 --- > > but I don't think we need to move heaven and earth to try to > > accelerate the 2.6.10 release process, either. > > Is it a problem for other kernel versions? 2.4? Shouldn't this patch be > pushed out separately to distributions?
It's a problem for all kernels back to 1.3.57 (when SMP was added) and perhaps earlier for kernel-internal get_random_bytes users. Fixing pre-2.6 means backporting the whole driver but not the changes in the network area.
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