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Bug 1547932 - libvirt starts dnsmasq which runs as nobody user
Summary: libvirt starts dnsmasq which runs as nobody user
Keywords:
Status: CLOSED DUPLICATE of bug 1548050
Alias: None
Product: Fedora
Classification: Fedora
Component: dnsmasq
Version: 27
Hardware: Unspecified
OS: Unspecified
unspecified
high
Target Milestone: ---
Assignee: Petr Menšík
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks: 1537262 1591969
TreeView+ depends on / blocked
 
Reported: 2018-02-22 10:15 UTC by Zbigniew Jędrzejewski-Szmek
Modified: 2018-06-15 21:49 UTC (History)
15 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2018-02-23 02:50:55 UTC
Type: Bug
Embargoed:

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System ID Private Priority Status Summary Last Updated
Red Hat Bugzilla 1548050 0 unspecified CLOSED dnsmasq starts dnsmasq which runs as nobody user 2022-05-16 11:32:56 UTC

Internal Links: 1548050

Description Zbigniew Jędrzejewski-Szmek 2018-02-22 10:15:01 UTC 
Description of problem:
When libvirt.service is started, is starts a bunch of processes, including dnsmasq. dnsmasq has two processes: one runs as root, and one runs as nobody!
This is insecure and in direct contradiction to packaging guidelines [https://fedoraproject.org/wiki/Packaging:Guidelines#Users_and_Groups].

Version-Release number of selected component (if applicable):
libvirt-daemon-3.7.0-3.fc27.x86_64
dnsmasq-2.78-2.fc27.x86_64

How reproducible:
This seems deterministic, at least on two machines I tested.
Comment 1 Laine Stump 2018-02-22 14:21:09 UTC 
libvirt doesn't set the uid for the dnsmasq process. It execs dnsmasq and leaves it to do whatever is appropriate.

Try enabling dnsmasq.service then starting it. You'll see the same issue.
Comment 2 Zbigniew Jędrzejewski-Szmek 2018-02-22 15:19:22 UTC 
Yes, it's very likely that the similar bug exists in dnsmasq.service. Note that the issue exists at the _service_ level. Each time dnsmasq is running in a separate service, it must be using a dedicated user. Thus, libvirt must take care to run dnsmasq appropriately.
Comment 3 Daniel Berrangé 2018-02-22 15:24:55 UTC 
Re-assigning to dnsmasq, since libvirt isn't picking the "nobody" user account - it is a decision compiled into dnsmasq - Fedora should patch it to run as a "dnsmasq" user account by default.

Running each separate dnsmasq process in a different user account is total overkill so not something we would do in libvirt - just let dnsmasq pick a more suitable default account.
Comment 4 Zbigniew Jędrzejewski-Szmek 2018-02-22 15:36:19 UTC 
In the meantime I opened a separate bug against dnsmasq.

I think "your" dnsmasq should get a dedicated user, so that it can never step on the toes of the dnsmasq from dnsmasq.service, and vice-versa. Let's see what dnsmasq maintainers say.
Comment 5 Itamar Reis Peixoto 2018-02-22 17:12:21 UTC 
(In reply to Daniel Berrange from comment #3)
please take a look ->

https://bugzilla.redhat.com/show_bug.cgi?id=1548050


dnsmasq accepts the user/group parameters,

user=dnsmasq
group=dnsmasq

I think libvirt should include these info on -> 

/var/lib/libvirt/dnsmasq/default.conf

if you move default.conf to /etc/dnsmasq.d and run dnsmasq with -conf-file=/etc/dnsmasq.conf then it will run under dnsmasq.conf user (after this https://src.fedoraproject.org/rpms/dnsmasq/pull-request/1  merged)
Comment 6 Daniel Berrangé 2018-02-22 17:33:41 UTC 
Yes, I know libvirt could set a custom user / group via config, but that doesn't solve the root cause problem. The Fedora guidelines linked above say:

  "Note that system services packaged for Fedora MUST NOT run as the nobody user, but MUST instead allocate their own system user. "

so that strongly says that dnsmasq's built-in default should be changed to run as dnsmasq user account. Once that's done there's nothing needed in libvirt.
Comment 7 Zbigniew Jędrzejewski-Szmek 2018-02-22 18:08:52 UTC 
My point is that dnsmasq-binary-running-in-dnsmasq.service, dnsmasq-binary-running-in-libvirt.service, and any other instance, are all separate users.

The wider picture is that users are the strongest security and separation mechanism that Linux has, and we should use as many of them as possible.
Comment 8 Laine Stump 2018-02-22 19:37:39 UTC 
Setting user= in the example conf file is inadequate, even for the instance of dnsmasq started by the dnsmasq service file. See my comment in the pull request for the patch that does that:

https://src.fedoraproject.org/rpms/dnsmasq/pull-request/1

The default user should be set in dnsmasq's src/config.h.
Comment 9 Itamar Reis Peixoto 2018-02-23 02:50:55 UTC 
(In reply to Laine Stump from comment #8)

ok, fixed in dnsmasq side, closing this one, thank you for the suggestion.

*** This bug has been marked as a duplicate of bug 1548050 ***
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