Fedora 26
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Sudo Settings
2017/07/16
 
Configure Sudo to separate users' duty if some people share privileges.
It's unnecessarry to install sudo manually because it is installed by default even if "Minimal Install".
[1] Transfer root privilege to a user all.
[root@dlp ~]#
visudo
# add to the end: user 'fedora' can use all root privilege

fedora  ALL=(ALL)       ALL
# how to write ⇒ destination host=(owner) command
# verify with user "fedora"

[fedora@dlp ~]$
/bin/cat /etc/shadow

cat: /etc/shadow: Permission denied    
# denied normally
[fedora@dlp ~]$
sudo /bin/cat /etc/shadow

Password:    
# own password
tcpdump:!!:16973::::::
systemd-coredump:!!:16973::::::    
# just executed
[2] In addition to the setting [1], set that some commands are not allowed.
[root@dlp ~]#
visudo
# near line 49: add aliase for the kind of shutdown commands

Cmnd_Alias SHUTDOWN = /sbin/halt, /sbin/shutdown, \
/sbin/poweroff, /sbin/reboot, /sbin/init, /bin/systemctl
# add ( commands in aliase 'SHUTDOWN' are not allowed )

fedora     ALL=(ALL)     ALL,
!SHUTDOWN
# verify with user "fedora"

[fedora@dlp ~]$
sudo /sbin/shutdown -r now

Password:
Sorry, user fedora is not allowed to execute '/sbin/shutdown -r now' as root on dlp.srv.world.    
# denied normally
[3] Transfer some commands with root privilege to users in a group.
[root@dlp ~]#
visudo
# near line 51: add aliase for the kind of user management comamnds

Cmnd_Alias USERMGR = /sbin/useradd, /sbin/userdel, /sbin/usermod, \
/bin/passwd
# add to the end

%usermgr ALL=(ALL) USERMGR
[root@dlp ~]#
groupadd usermgr

[root@dlp ~]#
usermod -G usermgr fedora

# verify with user "fedora"

[fedora@dlp ~]$
sudo /sbin/useradd testuser

[fedora@dlp ~]$    
# done normally

[fedora@dlp ~]$
sudo /bin/passwd testuser

Changing password for user testuser.
New UNIX password:    
# set testuser's password

Retype new UNIX password:
passwd: all authentication tokens updated successfully.
[4] Transfer a command with root privilege to a user.
[root@dlp ~]#
visudo
# add at the end

fedora  ALL=(ALL)       /sbin/visudo
cent    ALL=(ALL)       /sbin/useradd, /sbin/userdel, /sbin/usermod, /bin/passwd
ubuntu  ALL=(ALL)       /bin/vi
# verify with user "fedora"

[fedora@dlp ~]$
sudo /sbin/visudo
# possible to open and edit

## Sudoers allows particular users to run various commands as
## the root user, without needing the root password.
##
# verify with user "cent"

[cent@dlp ~]$
sudo /sbin/userdel -r testuser

[cent@dlp ~]$    
# done normally
# verify with user "ubuntu"

[ubuntu@dlp ~]$
sudo /bin/vi /boot/grub2/grub.cfg
# possible to open and edit

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
[5] The logs for sudo are kept in '/var/log/secure', but there are many kind of logs in it. If you'd like to keep only sudo's log in another file, Configure like follows.
[root@dlp ~]#
visudo
# add to the end

# for example, output logs to "local1" facility

Defaults syslog=local1
[root@dlp ~]#
vi /etc/rsyslog.conf
# line 46,47: add

*.info;mail.none;authpriv.none;cron.none;local1.none   /var/log/messages
local1.*                /var/log/sudo.log

# The authpriv file has restricted access.
authpriv.*              /var/log/secure
[root@dlp ~]#
systemctl restart rsyslog

 
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