Re: [PATCH 2/2] Setup private type for /etc/hostname.

From: Russell Coker <russell@coker.com.au>
To: "Sugar, David" <dsugar@tresys.com>
Cc: "selinux-refpolicy@vger.kernel.org"  <selinux-refpolicy@vger.kernel.org>
Subject: Re: [PATCH 2/2] Setup private type for /etc/hostname.
Date: Sat, 12 Jan 2019 12:11:57 +1100	[thread overview]
Message-ID: <31583679.z2ikJt99TD@xev> (raw)
In-Reply-To: <20190111153011.27275-5-dsugar@tresys.com>

Are we really gaining anything from not using net_conf_t?  Yes writing to 
net_conf_t allows doing more things than changing the hostname, but changing 
the hostname is a privileged operation anyway.

Are we getting a benefit to make up for the increase in types?

On Saturday, 12 January 2019 2:30:54 AM AEDT Sugar, David wrote:
> hostnamectl updates /etc/hostname.
> This change is setting up a private type for the file /etc/hostname (was
> etc_t) and granting hostnamectl permission to edit this file.  Note that
> hostnamectl is initially creating a new file .#hostname????? which is why
> the create permissions are requied.
> 
> type=AVC msg=audit(1547039052.041:563): avc:  denied  { write } for 
> pid=7564 comm="systemd-hostnam" name="etc" dev="dm-1" ino=101
> scontext=system_u:system_r:systemd_hostnamed_t:s0
> tcontext=system_u:object_r:etc_t:s0 tclass=dir permissive=1 type=AVC
> msg=audit(1547039052.041:563): avc:  denied  { add_name } for  pid=7564
> comm="systemd-hostnam" name=".#hostnamezyqZ9t"
> scontext=system_u:system_r:systemd_hostnamed_t:s0
> tcontext=system_u:object_r:etc_t:s0 tclass=dir permissive=1 type=AVC
> msg=audit(1547039052.041:563): avc:  denied  { create } for  pid=7564
> comm="systemd-hostnam" name=".#hostnamezyqZ9t"
> scontext=system_u:system_r:systemd_hostnamed_t:s0
> tcontext=system_u:object_r:etc_t:s0 tclass=file permissive=1 type=AVC
> msg=audit(1547039052.041:563): avc:  denied  { write } for  pid=7564
> comm="systemd-hostnam" path="/etc/.#hostnamezyqZ9t" dev="dm-1" ino=1094726
> scontext=system_u:system_r:systemd_hostnamed_t:s0
> tcontext=system_u:object_r:etc_t:s0 tclass=file permissive=1 type=SYSCALL
> msg=audit(1547039052.041:563): arch=c000003e syscall=2 success=yes exit=8
> a0=560d0bba34b0 a1=800c2 a2=180 a3=5c35f14c items=2 ppid=1 pid=7564
> auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0
> tty=(none) ses=4294967295 comm="systemd-hostnam"
> exe="/usr/lib/systemd/systemd-hostnamed"
> subj=system_u:system_r:systemd_hostnamed_t:s0 key=(null) type=AVC
> msg=audit(1547039052.041:564): avc:  denied  { setattr } for  pid=7564
> comm="systemd-hostnam" name=".#hostnamezyqZ9t" dev="dm-1" ino=1094726
> scontext=system_u:system_r:systemd_hostnamed_t:s0
> tcontext=system_u:object_r:etc_t:s0 tclass=file permissive=1 type=SYSCALL
> msg=audit(1547039052.041:564): arch=c000003e syscall=91 success=yes exit=0
> a0=8 a1=1a4 a2=fbad2484 a3=24 items=1 ppid=1 pid=7564 auid=4294967295 uid=0
> gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295
> comm="systemd-hostnam" exe="/usr/lib/systemd/systemd-hostnamed"
> subj=system_u:system_r:systemd_hostnamed_t:s0 key=(null) type=AVC
> msg=audit(1547039052.041:565): avc:  denied  { remove_name } for  pid=7564
> comm="systemd-hostnam" name=".#hostnamezyqZ9t" dev="dm-1" ino=1094726
> scontext=system_u:system_r:systemd_hostnamed_t:s0
> tcontext=system_u:object_r:etc_t:s0 tclass=dir permissive=1 type=AVC
> msg=audit(1547039052.041:565): avc:  denied  { rename } for  pid=7564
> comm="systemd-hostnam" name=".#hostnamezyqZ9t" dev="dm-1" ino=1094726
> scontext=system_u:system_r:systemd_hostnamed_t:s0
> tcontext=system_u:object_r:etc_t:s0 tclass=file permissive=1 type=AVC
> msg=audit(1547039052.041:565): avc:  denied  { unlink } for  pid=7564
> comm="systemd-hostnam" name="hostname" dev="dm-1" ino=1094712
> scontext=system_u:system_r:systemd_hostnamed_t:s0
> tcontext=system_u:object_r:etc_t:s0 tclass=file permissive=1
> 
> Signed-off-by: Dave Sugar <dsugar@tresys.com>
> ---
>  policy/modules/system/systemd.fc | 1 +
>  policy/modules/system/systemd.te | 6 ++++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/policy/modules/system/systemd.fc
> b/policy/modules/system/systemd.fc index eefcfaf1..2277fc1e 100644
> --- a/policy/modules/system/systemd.fc
> +++ b/policy/modules/system/systemd.fc
> @@ -1,3 +1,4 @@
> +/etc/hostname				--	gen_context(system_u:object_r:hostname_etc_t,s0)
>  /etc/udev/hwdb\.bin			--	
gen_context(system_u:object_r:systemd_hwdb_t,s0)
> 
>  /run/log/journal(/.*)?				
gen_context(system_u:object_r:systemd_journal_t,s
> 0) diff --git a/policy/modules/system/systemd.te
> b/policy/modules/system/systemd.te index f5f7dc1b..3704b756 100644
> --- a/policy/modules/system/systemd.te
> +++ b/policy/modules/system/systemd.te
> @@ -77,6 +77,9 @@ type systemd_detect_virt_t;
>  type systemd_detect_virt_exec_t;
>  init_daemon_domain(systemd_detect_virt_t, systemd_detect_virt_exec_t)
> 
> +type hostname_etc_t;
> +files_config_file(hostname_etc_t)
> +
>  type systemd_hostnamed_t;
>  type systemd_hostnamed_exec_t;
>  init_daemon_domain(systemd_hostnamed_t, systemd_hostnamed_exec_t)
> @@ -317,10 +320,13 @@ seutil_search_default_contexts(systemd_coredump_t)
>  # Hostnamed policy
>  #
> 
> +allow systemd_hostnamed_t hostname_etc_t:file manage_file_perms;
> +
>  kernel_read_kernel_sysctls(systemd_hostnamed_t)
> 
>  dev_read_sysfs(systemd_hostnamed_t)
> 
> +files_etc_filetrans(systemd_hostnamed_t, hostname_etc_t, file)
>  files_read_etc_files(systemd_hostnamed_t)
> 
>  seutil_read_file_contexts(systemd_hostnamed_t)

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