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 `SHELL` is `/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:
<pre>
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
</pre>
And here is my `/etc/sudoers.d/zabbix`:
<pre>
Defaults:zabbix !requiretty

zabbix    ALL=(root) NOPASSWD:       /tmp/doit
</pre>

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:
<pre>
UserParameter=example.disk.discovery,/usr/local/bin/zabbix_raid_discovery
</pre>
`/usr/local/bin/zabbix_raid_discovery` is a Python script. I have modified it to simply do this:
<pre>
print subprocess.check_output(['/usr/bin/sudo', '-u', 'root', '/tmp/doit'])
</pre>
`/tmp/doit` simply does this:
<pre>
#!/bin/sh
env >> /tmp/outfile
</pre>
I run the following on my Zabbix server to run the `/usr/local/bin/zabbix_raid_discovery` script:
<pre>
zabbix_get -s client_hostname -k 'example.disk.discovery'
</pre>
Then I check the `/tmp/outfile`, and I see:
<pre>
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
</pre>
That `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 (`zabbix`).