Messages in this thread | | | Date | Mon, 25 Jun 2007 17:02:01 +0200 | From | Alexander Gabert <> | Subject | Re: [PATCH] get_random_long() and AT_ENTROPY for auxv, kernel 2.6.21.5 |
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Hi Matt, sorry for not answering your questions in the first place, i hope this did not mean to make a bad impression Matt Mackall schrieb: > On Sun, Jun 24, 2007 at 07:45:04PM +0200, Alexander Gabert wrote: > >> Hi Linus, >> hi LKML, >> >> i would like to thank LKML and especially Eric (thanks for the per_cpu >> macro tips and design guidelines!) and the other contributors to this idea. >> >> This time the patch is rather big because it also removes >> get_random_int() and introduces get_random_long() throughout the kernel. >> > > Stop right there. You still haven't answered my original question. > What is the point of this exercise in the first place, please? > > Am I right in thinking you have three unrelated patches here? > I don't think so but you may be right nonetheless if my opinion. > - something to do with aux vector headers > Adding the new field > - something to do with get_random_int repeating itself > Found while adding the new field and testing it. > - sweeping change of get_random_int to get_random_long for no obvious reason > It is needed for properly initializing a SSP guard which is (afaik) a long value. > These should be three completely separate patches. > Probably ... but bear in mind that the goal is still the same: allowing glibc to use SSP with /proc/self/auxv instead of fopen(/dev/urandom) as it is now. Effectively saving three syscalls (open,read,close) and making life easier for glibc because randomization "generated" in the kernel does not deplete /dev/urandom too much for high coverage SSP userlands (i.e. Gentoo Hardened).
I can imagine that Redhat would do the same with the SSP implementation in glibc, i think if this patch moves into kernel, they will bring out a glibc patch that is checking for AT_ENTROPY and using the opening of /dev/urandom for retrieving randomized data as a fallback for machines where such a kernel is not available. This is a win-win situation for both sides- the kernel wins because the pressure on /dev/urandom is released a bit (applicable to SSP environments) and the glibc wins because it has a reliable, fast, cheap and easy to use source for randomization.
Thank you,
Alex
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