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Random numbers for ASLRRandom numbers for ASLRPosted May 14, 2009 20:55 UTC (Thu) by wahern (subscriber, #37304)In reply to: Random numbers for ASLR by copsewood Parent article: Random numbers for ASLR
This argument is pure misdirection. There should be little doubt that cryptographically strong PRNGs exist which are just as performant as whatever ridiculous MD4 hack is being used now. Clearly there are cryptographers falling over themselves to try provide the code to Linus & Co.; he's just not hearing it.
Use a strong PRNG now, and worry (or not worry, as it may be) about ASLR entropy later. But who's going to care about the latter if the former would be the weak chain, regardless.
And let's not forget that there's an army of wholly untalented OEM engineers who will follow Linus & Co's lead, and will be (and surely are) using this inadequate PRNG for sundry cases in existing products, mimicking the same, poor calculus Linus uses in his stubborn defense.
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Random numbers for ASLR Posted May 14, 2009 21:47 UTC (Thu) by nix (subscriber, #2304) [Link] There should be little doubt that cryptographically strong PRNGs exist which are just as performant as whatever ridiculous MD4 hack is being used now. Clearly there are cryptographers falling over themselves to try provide the code to Linus & Co.; he's just not hearing it.If so, they're not doing it in that thread. Matt presented a PRNG that was twice as slow as the existing (crappy but cheap) MD4 one, to be used in time-critical contexts like process execution. That's not going to fly, given that that path has attention paid to every last cycle.
Random numbers for ASLR Posted May 15, 2009 11:55 UTC (Fri) by man_ls (subscriber, #15091) [Link] Linus wanted to speak about a small % instead of a big factor. Just from reading the article Ingo provided the answer: looking at the numbers in context we are talking about a 1% performance hit in fork(). If your system is completely CPU-bound and fork() takes half the CPU then your task will take 0.5% more to execute (seven extra minutes every day). I think it is quite acceptable for even a small increase in security.
Random numbers for ASLR Posted May 15, 2009 12:33 UTC (Fri) by hppnq (guest, #14462) [Link] If you genuinely worry about address space related exploits, you will know that ASLR is not really going to save the day regardless of the RNG used, although obviously some randomization is needed.
Random numbers for ASLR Posted May 15, 2009 18:17 UTC (Fri) by nix (subscriber, #2304) [Link]
ASLR can make attacks very much harder, but only on 64-bit systems (and of
course only if more than 8 bits of randomness is used). On 32-bit there isn't the room to make attacks significantly harder :(
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