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Date:   Wed, 4 Dec 2019 17:56:14 +0100
From:   Dominick Grift <dac.override@gmail.com>
To:     "Sugar, David" <dsugar@tresys.com>
Cc:     "selinux-refpolicy@vger.kernel.org" 
        <selinux-refpolicy@vger.kernel.org>
Subject: Re: [PATCH] Allow systemd to getattr configfile
Message-ID: <20191204165614.GA1321684@brutus.lan>
Mail-Followup-To: "Sugar, David" <dsugar@tresys.com>,
        "selinux-refpolicy@vger.kernel.org" <selinux-refpolicy@vger.kernel.org>
References: <20191204163306.16545-1-dsugar@tresys.com>
 <20191204163306.16545-2-dsugar@tresys.com>
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On Wed, Dec 04, 2019 at 04:33:20PM +0000, Sugar, David wrote:
> Systemd has ConditionalPathExists which is used to check if a path exists=
 to control starting a service.  But this requires getattr permissions on t=
he file.  This is generally for configuration files.  We are mostly seeing =
this is in our own policy.  But this lvm denial also fits the example.
>=20
> type=3DAVC msg=3Daudit(1575427946.229:1624): avc:  denied  { getattr } fo=
r  pid=3D1 comm=3D"systemd" path=3D"/etc/lvm/lvm.conf" dev=3D"dm-0" ino=3D5=
1799 scontext=3Dsystem_u:system_r:init_t:s0 tcontext=3Dsystem_u:object_r:lv=
m_etc_t:s0 tclass=3Dfile permissive=3D0
>=20
> This second example is from chronyd, but it is happening becuase I added =
the conditional in a drop-in file. Note that chronyd_conf_t is already a 'c=
onfigfile'.
>=20
> type=3DAVC msg=3Daudit(1575427959.882:1901): avc:  denied  { getattr } fo=
r  pid=3D1 comm=3D"systemd" path=3D"/etc/chrony.conf" dev=3D"dm-0" ino=3D53=
824 scontext=3Dsystem_u:system_r:init_t:s0 tcontext=3Dsystem_u:object_r:chr=
onyd_conf_t:s0 tclass=3Dfile permissive=3D1

how about something a little more general?

systemd_ConditionPath(`,'
	allow init_t $1:dir search_dir_perms;
	allow init_t $1:lnk_file read_lnk_file_perms;
	allow init_t $1:fifo_file getattr_fifo_file_perms;
	allow init_t $1:sock_file getattr_sock_file_perms;
	allow init_t $1:file getattr_file_perms;
	allow init_t $1:blk_file getattr_blk_file_perms;
	allow init_t $1:chr_file getattr_chr_file_perms;
')

>=20
> Signed-off-by: Dave Sugar <dsugar@tresys.com>
> ---
>  policy/modules/kernel/files.if | 20 ++++++++++++++++++++
>  policy/modules/system/init.te  |  1 +
>  policy/modules/system/lvm.te   |  2 +-
>  3 files changed, 22 insertions(+), 1 deletion(-)
>=20
> diff --git a/policy/modules/kernel/files.if b/policy/modules/kernel/files=
=2Eif
> index f1c94411..87be07ae 100644
> --- a/policy/modules/kernel/files.if
> +++ b/policy/modules/kernel/files.if
> @@ -1562,6 +1562,26 @@ interface(`files_relabel_config_dirs',`
>  	relabel_dirs_pattern($1, configfile, configfile)
>  ')
> =20
> +########################################
> +## <summary>
> +##	Getattr config files in /etc.
> +## </summary>
> +## <param name=3D"domain">
> +##	<summary>
> +##	Domain allowed access.
> +##	</summary>
> +## </param>
> +#
> +interface(`files_getattr_config_files',`
> +	gen_require(`
> +		attribute configfile;
> +	')
> +
> +	allow $1 configfile:dir list_dir_perms;
> +	getattr_files_pattern($1, configfile, configfile)
> +	read_lnk_files_pattern($1, configfile, configfile)
> +')
> +
>  ########################################
>  ## <summary>
>  ##	Read config files in /etc.
> diff --git a/policy/modules/system/init.te b/policy/modules/system/init.te
> index 8973a622..747b696e 100644
> --- a/policy/modules/system/init.te
> +++ b/policy/modules/system/init.te
> @@ -320,6 +320,7 @@ ifdef(`init_systemd',`
>  	domain_subj_id_change_exemption(init_t)
>  	domain_role_change_exemption(init_t)
> =20
> +	files_getattr_config_files(init_t)
>  	files_read_all_pids(init_t)
>  	files_list_usr(init_t)
>  	files_list_var(init_t)
> diff --git a/policy/modules/system/lvm.te b/policy/modules/system/lvm.te
> index ad4eb579..c05344e0 100644
> --- a/policy/modules/system/lvm.te
> +++ b/policy/modules/system/lvm.te
> @@ -25,7 +25,7 @@ domain_obj_id_change_exemption(lvm_t)
>  role system_r types lvm_t;
> =20
>  type lvm_etc_t;
> -files_type(lvm_etc_t)
> +files_config_file(lvm_etc_t)
> =20
>  type lvm_lock_t;
>  files_lock_file(lvm_lock_t)
> --=20
> 2.21.0
>=20

--=20
Key fingerprint =3D 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=3Dget&search=3D0x3B6C5F1D2C7B6B02
Dominick Grift

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