First, note that the existing policy's "allow" rule is not something I wrote. It is in the nut-2.8.0-3.el8.x86_64.rpm package. It is a complete mystery to me how a policy could allow those types of access to a type that is not a valid file type.
Second, opening up the permissions of nut_upsmon_t to write to user_tmp_t is precisely what I said I do _not_ want to do.
The solution I found (see my response to Trevor Hemsley) is to change the context of the FIFO to "initctl_t. That is one of the few fifo_file types that nut_upsmon_t is allowed to access. No change needed to the policy.
--
Bob Nichols "NOSPAM" is really part of my email address.
Do NOT delete it.
On 6/9/23 10:49, Henry Zhang wrote:
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 <rnicholsNOSPAM@xxxxxxxxxxx <mailto:rnicholsNOSPAM@xxxxxxxxxxx>> 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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