I'm running sudo-1.8.6 on CentOS 6.5. My question is very simple: How do I prevent SHELL from propagating from a user's environment to a sudo environment?
Usually people are going the other way- they want to preserve an environment variable. However, I am having an issue where my user "zabbix" whose shell is
/sbin/nologin tries to run a command via sudo. Sudo is preserving the
/sbin/nologin so that root cannot run subshells. (Update: This part is true, but it is not the SHELL environment variable. It is the shell value that is being pulled from /etc/passwd that is the problem.)
I include a test that illustrates the problem; this is not my real-world use case but it simply illustrates that the calling user's SHELL is preserved. I have a program that runs as user
zabbix. It calls
/usr/bin/sudo -u root /tmp/doit (the programming running as
zabbix is a daemon, so the
/sbin/nologin shell in the password file does not prevent it).
/tmp/doit is a shell script that simply has:
#!/bin/sh env > /tmp/outfile
(its mode is 755, obviously). In
outfile I can see that
/sbin/nologin. However, at this point the script is running as root, via sudo, so it should not have the previous user's environment variables, right?
Here is my /etc/sudoers:
Defaults requiretty Defaults !visiblepw Defaults always_set_home Defaults env_reset Defaults env_keep = "COLORS DISPLAY HOSTNAME HISTSIZE INPUTRC KDEDIR LS_COLORS" Defaults env_keep += "MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE" Defaults env_keep += "LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES" Defaults env_keep += "LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE" Defaults env_keep += "LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY" Defaults secure_path = /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin:/usr/local/sbin ## Allow root to run any commands anywhere root ALL=(ALL) ALL #includedir /etc/sudoers.d
And here is my
Defaults:zabbix !requiretty zabbix ALL=(root) NOPASSWD: /tmp/doit
Edit: A little more information:
The process running the sudo is
zabbix_agentd, from the Zabbix monitoring software. There is an entry in the
/etc/zabbix/zabbix_agentd.d/userparameter_disk.conf file which looks like:
/usr/local/bin/zabbix_raid_discovery is a Python script. I have modified it to simply do this:
print subprocess.check_output(['/usr/bin/sudo', '-u', 'root', '/tmp/doit'])
/tmp/doit simply does this:
#!/bin/sh env >> /tmp/outfile
I run the following on my Zabbix server to run the
zabbix_get -s client_hostname -k 'example.disk.discovery'
Then I check the
/tmp/outfile, and I see:
SHELL=/sbin/nologin TERM=linux USER=root SUDO_USER=zabbix SUDO_UID=497 USERNAME=root PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin:/usr/local/sbin MAIL=/var/mail/root PWD=/ LANG=en_US.UTF-8 SHLVL=1 SUDO_COMMAND=/tmp/doit HOME=/root LOGNAME=root SUDO_GID=497 _=/bin/env
SHELL line really bugs me. The file is owned by root, so I know it's being created by the root user, but the shell is from the calling user (