On Thu, Mar 20, 2025 at 01:28:31AM +0000, Ramsay Jones wrote: > > > 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. :) Okay. Will you pick it up in v2 of this patch series? Thanks! Patrick
