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Fix Problems

Created by dave. Last edited by dave, 15 days ago. Viewed 1,103 times. #2
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(2021-10-05)

CentOS 8 Problem: autofs isn't using /etc/auto.nfs to mount things.

Error in /var/log/audit/audit.log:

audit.log:type=AVC msg=audit(1633441257.707:78): avc:  denied  { read } for  pid=1346 comm="automount" name="auto.master" dev="sda2" ino=33588565 scontext=system_u:system_r:automount_t:s0 tcontext=unconfined_u:object_r:admin_home_t:s0 tclass=file permissive=0

Solution

# ausearch -c "automount"
time->Tue Oct  5 09:40:57 2021
type=PROCTITLE msg=audit(1633441257.707:78): proctitle=2F7573722F7362696E2F6175746F6D6F756E74002D2D73797374656D642D73657276696365002D2D646F6E742D636865636B2D6461656D6F6E
type=SYSCALL msg=audit(1633441257.707:78): arch=c000003e syscall=21 success=no exit=-13 a0=562e4d0d7e60 a1=4 a2=7fff45df2010 a3=0 items=0 ppid=1 pid=1346 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="automount" exe="/usr/sbin/automount" subj=system_u:system_r:automount_t:s0 key=(null)
type=AVC msg=audit(1633441257.707:78): avc:  denied  { read } for  pid=1346 comm="automount" name="auto.master" dev="sda2" ino=33588565 scontext=system_u:system_r:automount_t:s0 tcontext=unconfined_u:object_r:admin_home_t:s0 tclass=file permissive=0

# ausearch -c "automount" | audit2allow -M my-auto.master ******************** IMPORTANT *********************** To make this policy package active, execute:

semodule -i my-auto.master.pp

# semodule -i my-auto.master.pp #

Previously

(2017-09-20)

Example Problem

I'm on a CentOS 7.4.1708 system. I copied /etc/snmp/snmpd.conf from another system. When I query snmpd, I get nothing back. If I issue a

# setenforce 0
… then it works.

Troubleshooting

# yum -y install setroubeshoot
< ten million RPMs install >

# sealert -a /var/log/audit/audit.log | less

Scroll down to the bottom; the last entry starts with:

SELinux is preventing /usr/sbin/snmpd from getattr access on the file /etc/snmp/snmpd.conf.

***** Plugin restorecon (99.5 confidence) suggests ************************

If you want to fix the label. /etc/snmp/snmpd.conf default label should be etc_t. Then you can run restorecon. Do # /sbin/restorecon -v /etc/snmp/snmpd.conf

Solution

# /sbin/restorecon -v /etc/snmp/snmpd.conf
/sbin/restorecon reset /etc/snmp/snmpd.conf context unconfined_u:object_r:admin_home_t:s0->unconfined_u:object_r:etc_t:s0

Now when I enable enforcement and restart snmpd again, everything works.

Commentary

That was much less painful than previous expeditions into selinux. It still isn't clear what's going on, but figuring out what's wrong and how to fix it quickly is much easier. It would be nice if the setroubleshoot tool didn't decide you needed a bunch of X dependencies though.

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This is a collection of techical information, much of it learned the hard way. Consider it a lab book or a /info directory. I doubt much of it will be of use to anyone else.

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