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From:   Dominick Grift <dominick.grift@defensec.nl>
To:     Russell Coker <russell@coker.com.au>
Cc:     selinux-refpolicy@vger.kernel.org
Subject: Re: [PATCH] strict 2
References: <YAf58vwzUfndWAlS@xev>
Date:   Wed, 20 Jan 2021 14:50:33 +0100
In-Reply-To: <YAf58vwzUfndWAlS@xev> (Russell Coker's message of "Wed, 20 Jan
        2021 20:37:54 +1100")
Message-ID: <ypjl1refn2dy.fsf@defensec.nl>
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Russell Coker <russell@coker.com.au> writes:

> Second set of strict configuration patches.  Ready for inclusion.
>
> Signed-off-by: Russell Coker <russell@coker.com.au>
>
> Index: refpolicy-2.20210120/policy/modules/system/userdomain.if
> ===================================================================
> --- refpolicy-2.20210120.orig/policy/modules/system/userdomain.if
> +++ refpolicy-2.20210120/policy/modules/system/userdomain.if
> @@ -68,6 +68,8 @@ template(`userdom_base_user_template',`
>  	dontaudit $1_t user_tty_device_t:chr_file ioctl;
>  
>  	kernel_read_kernel_sysctls($1_t)
> +	kernel_read_crypto_sysctls($1_t)
> +	kernel_read_vm_overcommit_sysctl($1_t)

Probably more suitable for userdom_unpriv_user_template() instead

This is the least required user template and so an effort should be made
to keep this one really minimal.

>  	kernel_dontaudit_list_unlabeled($1_t)
>  	kernel_dontaudit_getattr_unlabeled_files($1_t)
>  	kernel_dontaudit_getattr_unlabeled_symlinks($1_t)
> @@ -3552,6 +3554,25 @@ interface(`userdom_delete_all_user_runti
>  ')
>  
>  ########################################
> +## <summary>
> +##     write user runtime socket files
> +## </summary>
> +## <param name="domain">
> +##     <summary>
> +##     Domain allowed access.
> +##     </summary>
> +## </param>
> +#
> +interface(`userdom_write_all_user_runtime_named_sockets',`
> +	gen_require(`
> +		attribute user_runtime_content_type;
> +	')
> +
> +	allow $1 user_runtime_content_type:dir list_dir_perms;
> +	allow $1 user_runtime_content_type:sock_file write;
> +')

I think this is just too broad. see below.

> +
> +########################################
>  ## <summary>
>  ##	delete user runtime files
>  ## </summary>
> Index: refpolicy-2.20210120/policy/modules/roles/sysadm.te
> ===================================================================
> --- refpolicy-2.20210120.orig/policy/modules/roles/sysadm.te
> +++ refpolicy-2.20210120/policy/modules/roles/sysadm.te
> @@ -33,11 +33,22 @@ ifndef(`enable_mls',`
>  # Local policy
>  #
>  
> +allow sysadm_t self:netlink_generic_socket { create setopt bind write read };
> +
> +# for ptrace
> +allow sysadm_t self:netlink_tcpdiag_socket { create write nlmsg_read
> read };

r_netlink_socket_perms (i suppose, but i dont know how this relates to
ptrace ... might be the wrong place to add this)

> +
> +allow sysadm_t self:capability audit_write;

Can you explain the above permission?

> +allow sysadm_t self:system status;

the status permission is *theorically* systemd specific (needs an ifdef init_systemd?)

But regardless, and this is personal:

Why associate all these permissions with the sysadm_t shell. Shells do
not have systemd awareness. Why not just target whatever command is
doing this instead so that we can enforce some integrity in the sysadm_t domain?

> +
>  corecmd_exec_shell(sysadm_t)
>  
>  corenet_ib_access_unlabeled_pkeys(sysadm_t)
>  corenet_ib_manage_subnet_unlabeled_endports(sysadm_t)
>  
> +domain_getsched_all_domains(sysadm_t)
> +
> +dev_read_cpuid(sysadm_t)
>  dev_read_kmsg(sysadm_t)
>  
>  mls_process_read_all_levels(sysadm_t)
> @@ -55,6 +66,9 @@ init_admin(sysadm_t)
>  userdom_manage_user_home_dirs(sysadm_t)
>  userdom_home_filetrans_user_home_dir(sysadm_t)
>  
> +# for systemd-analyze
> +files_get_etc_unit_status(sysadm_t)

See above

> +
>  ifdef(`direct_sysadm_daemon',`
>  	optional_policy(`
>  		init_run_daemon(sysadm_t, sysadm_r)
> @@ -1121,6 +1135,10 @@ optional_policy(`
>  ')
>  
>  optional_policy(`
> +	systemd_dbus_chat_logind(sysadm_t)
> +')

shells do not dbus chat with systemd-logind. associating rules with the
sysadm_t shell instead of targeting commands will eventually lead to
sysadm_t becoming a unconfined_t clone

> +
> +optional_policy(`
>  	tboot_run_txtstat(sysadm_t, sysadm_r)
>  ')
>  
> @@ -1188,6 +1206,7 @@ optional_policy(`
>  ')
>  
>  optional_policy(`
> +	dev_rw_generic_usb_dev(sysadm_t)

shells do not write usb devices. If you want this kind of access then
why not use unconfined_t shell?


>  	usbmodules_run(sysadm_t, sysadm_r)
>  ')
>  
> Index: refpolicy-2.20210120/policy/modules/services/xserver.if
> ===================================================================
> --- refpolicy-2.20210120.orig/policy/modules/services/xserver.if
> +++ refpolicy-2.20210120/policy/modules/services/xserver.if
> @@ -100,6 +100,7 @@ interface(`xserver_restricted_role',`
>  	xserver_xsession_entry_type($2)
>  	xserver_dontaudit_write_log($2)
>  	xserver_stream_connect_xdm($2)
> +	xserver_use_user_fonts($2)
>  	# certain apps want to read xdm.pid file
>  	xserver_read_xdm_runtime_files($2)
>  	# gnome-session creates socket under /tmp/.ICE-unix/
> @@ -141,7 +142,7 @@ interface(`xserver_role',`
>  	gen_require(`
>  		type iceauth_home_t, xserver_t, xserver_tmp_t, xserver_tmpfs_t, xauth_home_t;
>  		type user_fonts_t, user_fonts_cache_t, user_fonts_config_t;
> -		type mesa_shader_cache_t;
> +		type mesa_shader_cache_t, xdm_t;
>  	')
>  
>  	xserver_restricted_role($1, $2)
> @@ -184,6 +185,8 @@ interface(`xserver_role',`
>  
>  	xserver_read_xkb_libs($2)
>  
> +	allow $2 xdm_t:unix_stream_socket accept;

Looks weird, why would $2 have to accept connections on xdm_t unix
stream sockets?

> +
>  	optional_policy(`
>  		xdg_cache_filetrans($2, mesa_shader_cache_t, dir, "mesa_shader_cache")
>  	')
> @@ -1239,6 +1242,7 @@ interface(`xserver_read_xkb_libs',`
>  	allow $1 xkb_var_lib_t:dir list_dir_perms;
>  	read_files_pattern($1, xkb_var_lib_t, xkb_var_lib_t)
>  	read_lnk_files_pattern($1, xkb_var_lib_t, xkb_var_lib_t)
> +	allow $1 xkb_var_lib_t:file map;
>  ')
>  
>  ########################################
> Index: refpolicy-2.20210120/policy/modules/services/dbus.if
> ===================================================================
> --- refpolicy-2.20210120.orig/policy/modules/services/dbus.if
> +++ refpolicy-2.20210120/policy/modules/services/dbus.if
> @@ -84,6 +84,7 @@ template(`dbus_role_template',`
>  
>  	allow $3 $1_dbusd_t:unix_stream_socket connectto;
>  	allow $3 $1_dbusd_t:dbus { send_msg acquire_svc };
> +	allow $1_dbusd_t $3:dbus send_msg;

I do not believe this is needed, or that it should be part of this
template (too broad)

>  	allow $3 $1_dbusd_t:fd use;
>  
>  	allow $3 system_dbusd_t:dbus { send_msg acquire_svc };
> @@ -99,9 +100,13 @@ template(`dbus_role_template',`
>  
>  	allow $1_dbusd_t $3:process sigkill;
>  
> +	allow $1_dbusd_t self:process getcap;
> +
>  	corecmd_bin_domtrans($1_dbusd_t, $3)
>  	corecmd_shell_domtrans($1_dbusd_t, $3)
>  
> +	dev_read_sysfs($1_dbusd_t)
> +
>  	auth_use_nsswitch($1_dbusd_t)
>  
>  	ifdef(`hide_broken_symptoms',`
> @@ -111,6 +116,15 @@ template(`dbus_role_template',`
>  	optional_policy(`
>  		systemd_read_logind_runtime_files($1_dbusd_t)
>  	')
> +
> +	optional_policy(`
> +		init_dbus_chat($1_dbusd_t)
> +		dbus_system_bus_client($1_dbusd_t)

Why did you add this? is this to resolve dynamic users with systemd?
Using dbus to resolve dynamic users was a fluke and has been
reimplemented. So if this was added for that then its obsolete and it
should be revisited with modern systemd

> +	')
> +
> +	optional_policy(`
> +		xdg_read_data_files($1_dbusd_t)
> +	')

Is this for ~/.local/share/dbus-1? I would probably consider creating a
private xdg_data type for that , but thats subjective.

>  ')
>  
>  #######################################
> Index: refpolicy-2.20210120/policy/modules/services/ssh.if
> ===================================================================
> --- refpolicy-2.20210120.orig/policy/modules/services/ssh.if
> +++ refpolicy-2.20210120/policy/modules/services/ssh.if
> @@ -439,6 +439,7 @@ template(`ssh_role_template',`
>  		xserver_use_xdm_fds($1_ssh_agent_t)
>  		xserver_rw_xdm_pipes($1_ssh_agent_t)
>  		xserver_sigchld_xdm($1_ssh_agent_t)
> +		xserver_write_inherited_xsession_log($1_ssh_agent_t)

this access should probably be allowed on application_domain level, but
thats a personal opinion. Basicall stdout of all application domains is
directed to the xsession log AFAIK.

No strong feelings about this though as xserver is dead anyway.

>  	')
>  ')
>  
> Index: refpolicy-2.20210120/policy/modules/kernel/corecommands.te
> ===================================================================
> --- refpolicy-2.20210120.orig/policy/modules/kernel/corecommands.te
> +++ refpolicy-2.20210120/policy/modules/kernel/corecommands.te
> @@ -13,7 +13,7 @@ attribute exec_type;
>  #
>  # bin_t is the type of files in the system bin/sbin directories.
>  #
> -type bin_t alias { ls_exec_t sbin_t };
> +type bin_t alias { ls_exec_t sbin_t systemd_analyze_exec_t };

I wouldnt remove systemd_analyze_t but i will leave that for others to
decide (obviously)

>  corecmd_executable_file(bin_t)
>  dev_associate(bin_t)	#For /dev/MAKEDEV
>  
> Index: refpolicy-2.20210120/policy/modules/system/systemd.te
> ===================================================================
> --- refpolicy-2.20210120.orig/policy/modules/system/systemd.te
> +++ refpolicy-2.20210120/policy/modules/system/systemd.te
> @@ -55,10 +55,6 @@ type systemd_activate_t;
>  type systemd_activate_exec_t;
>  init_system_domain(systemd_activate_t, systemd_activate_exec_t)
>  
> -type systemd_analyze_t;
> -type systemd_analyze_exec_t;
> -init_daemon_domain(systemd_analyze_t, systemd_analyze_exec_t)
> -
>  type systemd_backlight_t;
>  type systemd_backlight_exec_t;
>  init_system_domain(systemd_backlight_t, systemd_backlight_exec_t)
> @@ -1361,6 +1357,7 @@ tunable_policy(`systemd_tmpfiles_manage_
>  ')
>  
>  optional_policy(`
> +	dbus_manage_lib_files(systemd_tmpfiles_t)
>  	dbus_read_lib_files(systemd_tmpfiles_t)
>  	dbus_relabel_lib_dirs(systemd_tmpfiles_t)
>  ')
> Index: refpolicy-2.20210120/policy/modules/services/cron.te
> ===================================================================
> --- refpolicy-2.20210120.orig/policy/modules/services/cron.te
> +++ refpolicy-2.20210120/policy/modules/services/cron.te
> @@ -489,6 +489,7 @@ kernel_getattr_core_if(system_cronjob_t)
>  kernel_getattr_message_if(system_cronjob_t)
>  
>  kernel_read_crypto_sysctls(system_cronjob_t)
> +kernel_read_fs_sysctls(system_cronjob_t)
>  kernel_read_irq_sysctls(system_cronjob_t)
>  kernel_read_kernel_sysctls(system_cronjob_t)
>  kernel_read_network_state(system_cronjob_t)
> Index: refpolicy-2.20210120/policy/modules/apps/pulseaudio.te
> ===================================================================
> --- refpolicy-2.20210120.orig/policy/modules/apps/pulseaudio.te
> +++ refpolicy-2.20210120/policy/modules/apps/pulseaudio.te
> @@ -156,6 +156,7 @@ userdom_search_user_home_content(pulseau
>  userdom_manage_user_tmp_dirs(pulseaudio_t)
>  userdom_manage_user_tmp_files(pulseaudio_t)
>  userdom_manage_user_tmp_sockets(pulseaudio_t)
> +userdom_write_all_user_runtime_named_sockets(pulseaudio_t)
>  
>  tunable_policy(`pulseaudio_execmem',`
>  	allow pulseaudio_t self:process execmem;
>

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