Re: Trying to set context on a FIFO for nut_upsmon_t process

Robert,

based on your audit.log message, the new policy should be
allow nut_upsmon_t user_tmp_t:fifo_file getattr

your policy:
allow nut_upsmon_t nut_upsmon_t:fifo_file { append getattr ioctl lock open
read write };

destination type should be user_tmp_t instead of nut_upsmon_t

Normally, after updating your policy, your operation should go through

---henry

On Thu, Jun 8, 2023 at 2:49 PM Robert Nichols <[email protected]>
wrote:

> On 6/8/23 16:12, Henry Zhang wrote:
> > Robert,
> >
> > If your application fails due to selinux policy, you could check
> /var/log/audit/audit.log.
> > If the audit.log contains denial, please post or attach the log here.
> > It should show what kind of policy your application needed in order to
> execute it.
> >
> > ---henry
>
> Since you asked, see below. I really don't want to allow a nut_upsmon_t
> process to write to any user_tmp_t file. That's adding unnecessary
> privilege. The right solution is to give the FIFO a label that allows the
> access. I used sesearch to find out what target types would be appropriate,
> and found:
>
>     allow nut_upsmon_t nut_upsmon_t:fifo_file { append getattr ioctl lock
> open read write };
>
> Note that the error is for "getattr", not "write". The script is checking
> that the name refers to a FIFO before writing to it. The same problem would
> occur for a "write" attempt.
>
> chcon fails when trying to set that context on the FIFO, and when it tries
> I see a message that nut_upsmon_t is not a valid file type. What is it,
> then? Perhaps valid on a FIFO but not on an ordinary file?? The above
> "allow" rule shows what I need, but there is no way to set it.
>
> SELinux is preventing /usr/bin/bash from getattr access on the fifo_file
> /tmp/.alertFIFO2.
>
> *****  Plugin catchall (100. confidence) suggests
>  **************************
>
> If you believe that bash should be allowed getattr access on the
> .alertFIFO2 fifo_file 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 'UPS-alert' --raw | audit2allow -M my-UPSalert
> # semodule -X 300 -i my-UPSalert.pp
>
> Additional Information:
> Source Context                system_u:system_r:nut_upsmon_t:s0
> Target Context                unconfined_u:object_r:user_tmp_t:s0
> Target Objects                /tmp/.alertFIFO2 [ fifo_file ]
> Source                        UPS-alert
> Source Path                   /usr/bin/bash
> Port                          <Unknown>
> Host                          omega-3x.local
> Source RPM Packages
> Target RPM Packages
> SELinux Policy RPM            selinux-policy-targeted-3.14.3-117.el8.noarch
> Local Policy RPM              selinux-policy-targeted-3.14.3-117.el8.noarch
> Selinux Enabled               True
> Policy Type                   targeted
> Enforcing Mode                Enforcing
> Host Name                     omega-3x.local
> Platform                      Linux omega-3x.local
> 4.18.0-477.13.1.el8_8.x86_64
>                                #1 SMP Tue May 30 22:15:39 UTC 2023 x86_64
> x86_64
> Alert Count                   4
> First Seen                    2023-06-08 16:32:07 CDT
> Last Seen                     2023-06-08 16:32:17 CDT
> Local ID                      87bfa152-e72e-4bff-872e-2ccd882f0d48
>
> Raw Audit Messages
> type=AVC msg=audit(1686259937.20:17430): avc:  denied  { getattr } for
> pid=860169 comm="UPS-alert" path="/tmp/.alertFIFO2" dev="tmpfs"
> ino=19804366 scontext=system_u:system_r:nut_upsmon_t:s0
> tcontext=unconfined_u:object_r:user_tmp_t:s0 tclass=fifo_file permissive=0
>
>
> Hash: UPS-alert,nut_upsmon_t,user_tmp_t,fifo_file,getattr
>
>
>
>
> --
> Bob Nichols     "NOSPAM" is really part of my email address.
>                  Do NOT delete it.
>
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