On 19/03/2025 13:30, Patrick Steinhardt wrote: > On Sun, Mar 16, 2025 at 01:41:40PM -0700, Junio C Hamano wrote: >> "brian m. carlson" <sandals@xxxxxxxxxxxxxxxxxxxx> writes: >> >>> When arc4random was added to glibc, the Linux kernel CSPRNG maintainer >>> argued that it was not a secure approach (I disagree), and convinced the >>> glibc maintainers to just make it a wrapper around the Linux kernel >>> CSPRNG, which it now is. So there's no actual benefit to calling >>> arc4random versus getrandom, and since it's newer and less commonly >>> available than getrandom, as well as slightly slower (because of an >>> extra function call), getrandom should be preferred. >> >> This >> >> https://www.phoronix.com/news/GNU-Glibc-arc4random-Functions >> >> was the first hit of my search in the area, but I think you are >> referring to >> >> https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=eaad4f9 >> >> that happened 5 days after the thing got in and the code there tells >> me that your summary of the situation is quite accurate. >> >> So I agree that dropping this patch makes sense, but do we want to >> do a bit more to improve the situation? >> >> Here is an attempt to improve what we have in Makefile (and possibly >> the Linux section in config.mak.uname, but that is improving what we >> do not have) to tell folks that arc4random in glibc is only for >> compatibility and they should pick getrandom() until the situation >> changes. >> >> --- >8 --- >> Subject: config/Makefile: a note on CSPRNG_METHOD choice for Linux >> >> arc4random() was added to glibc in July 2022, but quickly replaced >> by a stub implementation that wraps around getrandom(). Hence there >> is no actual benefit to calling arc4random() over getrandom() on >> glibc based systems, at least for now. >> >> To avoid enticing Linux users to choose arc4random(), leave a note >> that their arc4random() in glibc is not the same as what their >> friends use on other platforms, and guide them to use getrandom() >> instead in the meantime. > > Makes me wonder whether we should also change the order in which Meson > auto-detects functions. That is, do we want the following patch that > favors getrandom over arc4random? > That was my immediate thought also. :) ATB, Ramsay Jones
