rc: dmesg: Allow file and umask to be configurable

[jlduran]

Summary

Allow file, and umask to be configurable.

Being able to set the umask via an rc variable is useful when setting:

security.bsd.unprivileged_read_msgbuf=0

As it allows a user to configure:

dmesg_umask="066"

Without modifying the rc script, and preventing the contents of the
$dmesg_file (/var/run/dmesg.boot) from being publicly readable.

PR: 272552

[jlduran]

libexec/rc/rc.d/dmesg

15

I can leave this part of the patch intact, without the user being able to change the dmesg_file via rc.conf.
My main focus is on setting the umask before creating the file (with an rc variable).

[netchild]

The umask part looks fine.
About the dmesg_file part: from a technical point of view it is ok.,From a feature point of view, if it is not necessary, don't change it (I can't remember to have seen someone to have asked in the last 20 years about having it in another location).

[jlduran]

In D53169#1215059, @netchild wrote:

The umask part looks fine.
About the dmesg_file part: from a technical point of view it is ok.,From a feature point of view, if it is not necessary, don't change it (I can't remember to have seen someone to have asked in the last 20 years about having it in another location).

Thank you, good advice! Will do so when committing.