CentOS - Jan 2017 - tor and selinux

I'm experimenting with tor hidden services and got it to work nicely on
my Centos7, with tor from epel. That is, until I booted the machine.
Then SELinux kicked in and in the logs there's?

[warn] Directory /var/lib/tor/hidden_service/ cannot be read:
Permission denied

The permissions are
drwx------.??2 toranon toranon????4096 Jan 28 23:39 hidden_service

And SELinux gives the following

SELinux is preventing /usr/bin/tor from using the dac_override
capability.

*****??Plugin dac_override (91.4 confidence)
suggests???**********************

If you want to help identify if domain needs this access or you have a
file with the wrong permissions on your system
Then turn on full auditing to get path information about the offending
file and generate the error again.
Do

Turn on full auditing
# auditctl -w /etc/shadow -p w
Try to recreate AVC. Then execute
# ausearch -m avc -ts recent
If you see PATH record check ownership/permissions on file, and fix it,
otherwise report as a bugzilla.

*****??Plugin catchall (9.59 confidence)
suggests???**************************

If you believe that tor should have the dac_override capability by
default.
Then you should report this as a bug.
You can generate a local policy module to allow this access.
Do
allow this access for now by executing:
# ausearch -c 'tor' --raw | audit2allow -M my-tor
# semodule -i my-tor.pp


Additional Information:
Source Context????????????????system_u:system_r:tor_t:s0
Target Context????????????????system_u:system_r:tor_t:s0
Target Objects????????????????Unknown [ capability ]
Source????????????????????????tor
Source Path???????????????????/usr/bin/tor
Port??????????????????????????<Unknown>
Host??????????????????????????<Unknown>
Source RPM Packages???????????tor-0.2.8.12-1.el7.x86_64
Target RPM Packages???????????
Policy RPM????????????????????selinux-policy-3.13.1-102.el7_3.13.noarch
Selinux Enabled???????????????True
Policy Type???????????????????targeted
Enforcing Mode????????????????Enforcing
Host Name?????????????????????host
Platform??????????????????????Linux host 3.10.0-514.6.1.el7.x86_64
??????????????????????????????#1 SMP Wed Jan 18 13:06:36 UTC 2017
x86_64 x86_64
Alert Count???????????????????5
First Seen????????????????????2017-01-29 22:42:46 EST
Last Seen?????????????????????2017-01-29 22:42:51 EST
Local ID??????????????????????51ceb58e-19cf-4f8f-ab1e-fe48265aaf1d

Raw Audit Messages
type=AVC msg=audit(1485747771.709:106): avc:??denied??{ dac_override }
for??pid=2253 comm="tor"
capability=1??scontext=system_u:system_r:tor_t:s0
tcontext=system_u:system_r:tor_t:s0 tclass=capability


type=AVC msg=audit(1485747771.709:106): avc:??denied??{ dac_read_search
} for??pid=2253 comm="tor"
capability=2??scontext=system_u:system_r:tor_t:s0
tcontext=system_u:system_r:tor_t:s0 tclass=capability


type=SYSCALL msg=audit(1485747771.709:106): arch=x86_64 syscall=open
success=no exit=EACCES a0=7fcd2c12fe90 a1=20000 a2=0 a3=1 items=0
ppid=1 pid=2253 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm=tor
exe=/usr/bin/tor subj=system_u:system_r:tor_t:s0 key=(null)

Hash: tor,tor_t,tor_t,capability,dac_override


As I don't know what dac_override is I don't know if it's a good
idea
to give it to tor and the confidence seems quite low. 

Cheers
Mark

On 01/29/2017 11:59 AM, Mark wrote:
> As I don't know what dac_override is I don't know if it's a
good idea
> to give it to tor and the confidence seems quite low.

dac_override indicates that you're running your process as root, and 
it's trying to do something on the filesystem which is not explicitly 
allowed by permissions.  DAC is the standard POSIX permission system, 
and the process is trying to override it.  DAC allows access to the 
toranon user and toranon group only, and the process is trying to 
override that access by way of root access.

I'd say that no, giving dac_override is not a good idea, but mostly 
because that implies that you'd continue running the process as root.  
You should be running the service as the "toranon" user instead, in 
which case it will not need dac_override.

On Sun, 2017-01-29 at 15:53 -0800, Gordon Messmer wrote:
> On 01/29/2017 11:59 AM, Mark wrote:
> > As I don't know what dac_override is I don't know if it's
a good
> > idea
> > to give it to tor and the confidence seems quite low.
> 
> 
> dac_override indicates that you're running your process as root, and?
> it's trying to do something on the filesystem which is not
> explicitly?
> allowed by permissions.??DAC is the standard POSIX permission
> system,?
> and the process is trying to override it.??DAC allows access to the?
> toranon user and toranon group only, and the process is trying to?
> override that access by way of root access.
That's strange, because I started the tor process simply with
sudo systemctl start tor

The only changes I've really made was to add two lines of configuration
in torrc

Cheers
Mark