Re: Fix /etc/rc.d/random umask handling (/entropy permissions)

On Sun, Jan 22, 2017 at 01:22:07AM +0000, Lu Tung-Pin wrote:
> On 2017-01-21 22:01, Jilles Tjoelker wrote:
> > [Adding Cc: Dag-Erling Smørgrav who committed r273957 which seems to
> > have introduced this]
> > On Sat, Jan 21, 2017 at 01:21:42AM +0000, Lu Tung-Pin wrote:
> >> A 2014 change broke the umask handling in /etc/rc.d/random,
> >> leaving /entropy with ug+r permissions. Quick fix attached,

> Edit: go+r permissions.

> > Switching the umask here will avoid incorrect permissions on
> > /entropy on new installations, but will not fix existing systems. A
> > chmod command may be useful here.

> Note that random_start() first removes /entropy via feed_dev_random().
> There's also a removal in random_stop(). Provided that a removal occurs,
> the chmod won't be necessary on machines with an existing go+r /entropy.

Right, /entropy is deleted after being read so the chmod is not needed.

> I'm wondering, though: Would it be better to replace all the umask
> fiddling with simple chmods? Every other rc.d script uses chmod if it
> needs to set tighter permissions. When umask is used (dmesg, mountd,
> syslogd), it's with a relaxed 022 setting.

The umask ensures the file is created with the correct permissions so
there is no race window where an unprivileged process can open the file.
A permissions change has no existing opens.

-- 
Jilles Tjoelker