Re: unify entropy source for all php related functions

On Fri, Feb 14, 2014 at 4:19 PM, Jakub Zelenka <bukka@php.net> wrote: > On Fri, Feb 14, 2014 at 1:53 PM, Pierre Joye <pierre.php@gmail.com> wrote: >> >> On Feb 14, 2014 8:02 PM, "Andrey Andreev" <narf@devilix.net> wrote: >> >> > So how does openssl_random_pseudo_bytes() work without blocking then? >> >> Because it tells you if the result is crypto safe or not: >> >> string *openssl_random_pseudo_bytes* (int $length [, bool &$crypto_strong] >> ) >> >> >> If you want only crypto safe result another function has to be used (on >> opennssl). And my test.php that was pasted shows that it dumps TRUE for $crypto_strong, while mcrypt_create_iv() blocks. > That's not the way how it works in md_rand. The ssleay_rand_pseudo_bytes > (Rand_psedobytes called in openssl_random_pseudo_bytes) is just a wrapper > for ssleay_rand_bytes with pseudo flag set to 1. ssleay_rand_bytes first > calls Rand_poll that adds the entropy. The thing is that the entropy is > taken from /dev/urandom on Unix. It means you will always have enough > entropy on Linux and the functions returns 1 ($crypto_strong is set to > true). You won't get false on Linux though. The reason of the flag in > OpenSSL is if you run it in on some platform that can't provide enough > entropy which is not the case on Linux. Please see the sources for more > details. Sorry, I'm not really sure what this means, but 2 few bits that I spot are: - on UNIX(-like), it uses /dev/urandom - $crypto_strong will always be true on Linux (UNIX-whatever) And Pierre Joye says that /dev/urandom is not crypto-safe, so this kind of gets us in a conflict ... which one is it? The way I understand it, only /dev/whatever (meaning that it should be hardware input) could be considered crypto-safe and so if OpenSSL always returns without blocking, yet sets $crypto_strong to TRUE, then the same should be possible for PHP itself to do. That is, unless $crypto_strong is set to TRUE without the output actually being crypto-safe, in which case we have a bug. P.S.: Sorry folks, I didn't want to turn this into a "how OpenSSL works" thread. Cheers, Andrey.