Re: Assistance with SELinux and NFS Read-Only

On Tue, Dec 8, 2020 at 5:04 PM Felipe Polanco <[email protected]>
wrote:

> Hi,
>
> I'm trying to share an NFS mount point as Read-only using only
> SELinux, this is for learning purposes.
>
> I'm running Centos but I didn't find a Centos Mailing List, this one
> was the closest I could find.
>
Hi,

The behaviour should be basically the same for all distros using Fedora
based policy.


> I'm on Centos 7 server 7.8.2003
>
> I have run setsebool -P nfs_export_all_ro 1 and nfs_export_all_rw 0
> and still, the NFS clients can write to the files of the Share.
>
> I played with the public_content_t type but that made no difference on
> the files.
>
Do you mean you tried different types, e. g. public_content_rw_t?


> My share directory on NFS server:
>
> [root@localhost primary]# ls -lahZ
> drwxr-xr-x. root root unconfined_u:object_r:usr_t:s0   .
> drwxr-xr-x. root root unconfined_u:object_r:usr_t:s0   ..
> -rw-r--r--. root root system_u:object_r:public_content_t:s0 file1
> -rw-r--r--. root root unconfined_u:object_r:public_content_t:s0 file2
> -rw-r--r--. root root system_u:object_r:public_content_t:s0 file3
> -rw-r--r--. root root unconfined_u:object_r:public_content_t:s0 file4
>
> Those with user system_u were created by NFS clients, the unconfined_u
> were created by root on the NFS server, still the NFS clients have
> write capabilities to all of them.
>
>
> [root@localhost primary]# getsebool -a | grep nfs_export
> nfs_export_all_ro --> on
> nfs_export_all_rw --> off
>
> [root@localhost primary]# getenforce
> Enforcing
>
> Any ideas?
>
Please install setools-console and run and compare with this output:

# getsebool nfsd_anon_write
nfsd_anon_write --> off
# sesearch -A -s nfsd_t -t public_content_t -c file
allow domain file_type:file map; [ domain_can_mmap_files ]:True
allow nfsd_t non_security_file_type:file { getattr ioctl lock open read };
[ nfs_export_all_ro ]:True
allow nfsd_t public_content_t:file { getattr ioctl lock map open read };
# sesearch -A -s nfsd_t -t public_content_t -c file -p write
# sesearch -A -s nfsd_t -t public_content_rw_t -c file -p write
allow nfsd_t public_content_rw_t:file { append create link rename setattr
unlink write }; [ nfsd_anon_write ]:True


> Thanks,
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-- 

Zdenek Pytela
SELinux team

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