Fatal glibc error: cannot get entropy for arc4random

[Jan Palus]

On 19.07.2024 20:00, Arkadiusz Miśkiewicz via pld-devel-en wrote:
> On 19/07/2024 12:48, Elan Ruusamäe wrote:
> > openssh is unable startup
> > 
> > # service sshd restart
> > Fatal glibc error: cannot get entropy for arc4random
> > Aborted
> > 
> > # rpm -q glibc openssh-server
> > glibc-2.39-6-th.x86_64
> > openssh-server-9.8p1-1-th.x86_64
> > 
> > # uname -r
> > 3.13.0-32-generic
> > 
> > from quick internet search 3.15 kernel is needed? but not specified in
> > .spec?
> 
> Hm, why 3.15?
> 
> Looking at the arc4random code it fallbacks to /dev/random and /dev/urandom
> if syscall is not available (getrandom syscall was introduced in 3.17).

Actually glibc-2.39-6 does not fallback to /dev/*random due to bug in
arc4random fallback logic (return value checked for ENOSYS instead of
errno).

It was fixed on Jul 8 (glibc 2.40 does not suffer from it):

https://sourceware.org/git/?p=glibc.git;a=commit;h=184b9e530e6326e668709826903b6d30dc6cac3f

> 
> Maybe sshd is not allowing access to these at that point?
> 
> strace could tell us something.
> 
> -- 
> Arkadiusz Miśkiewicz, arekm / ( maven.pl | pld-linux.org )
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