Bug 782499

Summary:	Propose that you turn on PrivateTmp=true in service file for dhcpd
Product:	[Fedora] Fedora	Reporter:	Daniel Walsh <dwalsh>
Component:	dhcp	Assignee:	Jiri Popelka <jpopelka>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	rawhide	CC:	jpopelka
Target Milestone:	---
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-01-17 17:23:06 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	782466

Description Daniel Walsh 2012-01-17 15:39:30 UTC

I would like to propose using PrivateTmp for dhcpd systemd unit file
This should make the use of /tmp directory more secure
and avoid users from being able to potentially effect it.

http://fedoraproject.org/wiki/Features/ServicesPrivateTmp

Comment 1 Jiri Popelka 2012-01-25 14:30:00 UTC

Actually it's only dhclient (dhclient-script) that uses /tmp.
There's a code in dhcpd that reads attributes of files in /tmp
to generate semi random data, but it doesn't seem to be used anyway.

So I'm going to revert the change I already did and close this as NOTABUG.

Comment 2 Daniel Walsh 2012-01-25 20:44:30 UTC

Well do any of the scripts to redirection within bash

command << _EOF
...
_EOF

Also can't dhclient-script execute custom scripts?

Comment 3 Jiri Popelka 2012-01-26 06:57:02 UTC

(In reply to comment #2)
> Well do any of the scripts to redirection within bash
> 
> command << _EOF
> ...
> _EOF

Not sure whether this is what you are asking (if that was a question),
but dhclient-script uses /tmp this way:
rscf="$(mktemp ${TMPDIR:-/tmp}/XXXXXX)"
echo "nameserver ${nameserver}" >> ${rscf}
change_resolv_conf ${rscf}
rm -f ${rscf}

change_resolv_conf is from
/etc/sysconfig/network-scripts/network-functions
and for example
/etc/sysconfig/network-scripts/ifup-post
use it the same way.

> Also can't dhclient-script execute custom scripts?

Yes, it runs (if they exist)
/etc/dhcp/dhclient-enter-hooks
/etc/dhcp/dhclient-up-hooks
/etc/dhcp/dhclient-down-hooks
/etc/dhcp/dhclient-exit-hooks
/etc/dhcp/dhclient.d/*.sh

Comment 4 Daniel Walsh 2012-01-26 22:34:16 UTC

So why not be secure by default and not have to worry about users hacking something in here to break dhclient or get a privledge exploit?

Comment 5 Jiri Popelka 2012-01-27 08:24:27 UTC

I'm not sure I understand.
There's no dhclient systemd unit to put PrivateTmp into.
dhclient is started either by NetworkManager (NM) or by network-scripts.
And in case of NM the dhclient-script is even not used because NM has its own "script" for dhclient.

Comment 6 Daniel Walsh 2012-01-27 16:21:07 UTC

I thought I checked that it is had a systemd unit file.  

Sorry never mind.