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Bug 1715844 - [dhcpd] execute /lib64/libnss_sss.so.2 AVC denial
Summary: [dhcpd] execute /lib64/libnss_sss.so.2 AVC denial
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: selinux-policy
Version: 7.7
Hardware: Unspecified
OS: Unspecified
low
low
Target Milestone: rc
: ---
Assignee: Lukas Vrabec
QA Contact: BaseOS QE Security Team
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2019-05-31 12:31 UTC by Patrik Hagara
Modified: 2019-06-03 13:12 UTC (History)
6 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
: 1716418 (view as bug list)
Environment:
Last Closed: 2019-06-03 13:12:43 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Patrik Hagara 2019-05-31 12:31:59 UTC 
Description of problem:

dhcpd daemon start produces the following AVC denial:

time->Fri May 31 13:57:32 2019
type=PROCTITLE msg=audit(1559303852.249:413): proctitle=6468637064002D6366002F746D702F646863702E636F6E66002D6368726F6F74002F7661722F6C69622F6468637064002D6C66002F64622F64686370642E6C6561736573002D75736572006468637064002D67726F7570006468637064002D7066002F7661722F72756E2F64686370642E7069640064756D6D7930
type=SYSCALL msg=audit(1559303852.249:413): arch=c000003e syscall=9 success=yes exit=140067871424512 a0=0 a1=208490 a2=5 a3=802 items=0 ppid=5987 pid=5988 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="dhcpd" exe="/usr/sbin/dhcpd" subj=system_u:system_r:dhcpd_t:s0 key=(null)
type=AVC msg=audit(1559303852.249:413): avc:  denied  { execute } for  pid=5988 comm="dhcpd" path="/lib64/libnss_sss.so.2" dev="dm-0" ino=5752596 scontext=system_u:system_r:dhcpd_t:s0 tcontext=system_u:object_r:dhcpd_state_t:s0 tclass=file permissive=1

the dhcpd service appears to work, but might be missing some features do to the above when selinux is in enforcing mode (default).

Version-Release number of selected component (if applicable):
selinux-policy-3.13.1-249.el7.noarch

How reproducible:
always

Steps to Reproduce:
1. install, configure and start dhcpd
2.
3.

Actual results:
daemon starts, AVC denial logged

Expected results:
no AVC denials

Additional info:
Comment 2 Milos Malik 2019-05-31 14:37:49 UTC 
The /lib64/libnss_sss.so.2 is mislabeled.

Correct label is:
# matchpathcon /lib64/libnss_sss.so.2
/lib64/libnss_sss.so.2	system_u:object_r:lib_t:s0
#

Following command will repair the problem:
# restorecon -Rv /lib64
Comment 3 Lukas Vrabec 2019-06-03 11:49:45 UTC 
Patrick, 

Could you please confirm that solution from comment#2 is working for you? 

Thanks,
Lukas.
Comment 4 Patrik Hagara 2019-06-03 12:08:29 UTC 
Actually, the bug appears to be on the cluster resource agent side -- I'm running this in as a pacemaker cluster resource, sorry for not mentioning that in the description.

The resource agent defaults to running dhcpd in a chroot and copies config files and required libraries (libnss_sss.so.2 among them) into the chroot [1]. The "-p/--preserve" option of `cp` does not appear to preserve selinux context of the copied files (unless it's explicitly requested) and so the AVCs occur.

IIUC, this should be fixed in the resource agent itself and not selinux-policy. Is that correct?


[1] https://github.com/ClusterLabs/resource-agents/blob/master/heartbeat/dhcpd#L331
Comment 5 Zdenek Pytela 2019-06-03 12:57:55 UTC 
I'd suggest including xattr into the preserved set or use all, see cp(1):

       -p     same as --preserve=mode,ownership,timestamps

       --preserve[=ATTR_LIST]
              preserve the specified attributes (default: mode,ownership,timestamps), if possi‐
              ble additional attributes: context, links, xattr, all

or alternatively use restorecon after the cp command finishes.

Note -a has "all":

       -a, --archive
              same as -dR --preserve=all
Comment 6 Patrik Hagara 2019-06-03 13:06:36 UTC 
Thank you.

I've cloned this bug for the resource-agents component: bz#1716418.

Feel free to close this one.
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