Squid, SELinux and using a separate volume for the cache_dir

This was a slightly tricky one. I'm running CentOS5 with SELinux and I was trying to setup Squid to put its cache_dir on a LVM volume (to keep it from using up space on the root partition).

# /etc/init.d/squid stop
# cd /var/spool
# lvcreate -L64G -nvar-spool-squid vg
# mke2fs -j /dev/vg/var-spool-squid
# mkdir /mnt/squid ; mount /dev/vg/var-spool-squid squid
# cp -a /var/spool/squid/* /mnt/squid/
# cd /var/spool/squid
# rm -rf *
# cd /var/spool
# mount /dev/vg/var-spools-squid squid
# /etc/init.d/squid start

Starting squid: /etc/init.d/squid: line 53: 9440 Aborted $SQUID $SQUID_OPTS >>/var/log/squid/squid.out 2>&1
[FAILED]

# tail /var/log/messages

May 27 21:50:48 fw1-hosho setroubleshoot: SELinux is preventing /usr/sbin/named (named_t) "write" access to named (named_conf_t). For complete SELinux messages. run sealert -l 663ea169-d194-4c49-a5bb-a6a4bb707990
May 27 22:39:26 fw1-hosho squid: cache_dir /var/spool/squid: (13) Permission denied

# /usr/bin/sealert -l 626e75b4-32aa-4a61-88f7-f36a68fecd35
Summary
SELinux is preventing access to files with the label, file_t.

Detailed Description
SELinux permission checks on files labeled file_t are being denied. file_t
is the context the SELinux kernel gives to files that do not have a label.
This indicates a serious labeling problem. No files on an SELinux box should
ever be labeled file_t. If you have just added a new disk drive to the
system you can relabel it using the restorecon command. Otherwise you
should relabel the entire files system.

Allowing Access
You can execute the following command as root to relabel your computer
system: "touch /.autorelabel; reboot"

Additional Information

Source Context user_u:system_r:squid_t
Target Context user_u:object_r:file_t
Target Objects /var/spool/squid/00 [ dir ]
Affected RPM Packages squid-2.6.STABLE6-4.el5 [application]
Policy RPM selinux-policy-2.4.6-30.el5
Selinux Enabled True
Policy Type targeted
MLS Enabled True
Enforcing Mode Enforcing
Plugin Name plugins.file
Host Name fw1-hosho.intra.example.com.
Platform Linux fw1-hosho.intra.example.com. 2.6.18-8.1.4.el5
#1 SMP Thu May 17 03:16:52 EDT 2007 x86_64 x86_64
Alert Count 10
Line Numbers

Raw Audit Messages

avc: denied { getattr } for comm="squid" dev=dm-0 egid=23 euid=23
exe="/usr/sbin/squid" exit=-13 fsgid=23 fsuid=23 gid=23 items=0 name="00"
path="/var/spool/squid/00" pid=9584 scontext=user_u:system_r:squid_t:s0 sgid=23
subj=user_u:system_r:squid_t:s0 suid=0 tclass=dir
tcontext=user_u:object_r:file_t:s0 tty=(none) uid=23

...

So, the problem is that SELinux had not yet been told to look at the newly created volume (a LVM volume mounted on /var/spool/squid). Fixing this was rather simple once you know about the restorecon command.

# cd /var/spool/squid
# /usr/sbin/squid -z
# /sbin/restorecon -R *
# /etc/init.d/squid start