xserver: introduce new fc and interface to manage X session logs

The following patch (split in two parts, one for base and
another one for contrib) introduces a new file context for
the X session log files and two new interface to manage
them (instead of allowing to manage the whole user home
content files).

It is required after the recent confinement of graphical
desktop components (e.g. wm, xscreensaver).

The second version of the patch correctly uses file type
transitions and uses more tight permissions.

The third version simply moves some interface calls.

The fourth version introduces the new template for
username-dependent file contexts.

The fifth version moves other interface calls thanks to
further revisions from Christopher PeBenito (the corresponding
contrib policy part remains unchanged at version 4).

This sixth version, adds the missing diff relative to the
xserver.te policy file to declare the new xsession_log_t type.

The corresponding base policy patch is at version 4.

Signed-off-by: Guido Trentalancia <guido@trentalancia.net>

3 files changed, 68 insertions, 2 deletions

diff --git a/policy/modules/services/xserver.fc b/policy/modules/services/xserver.fc
index 5b218c63..389b74fa 100644
--- a/policy/modules/services/xserver.fc
+++ b/policy/modules/services/xserver.fc
@@ -10,6 +10,7 @@ HOME_DIR/\.fontconfig(/.*)?	gen_context(system_u:object_r:user_fonts_cache_t,s0)
 HOME_DIR/\.ICEauthority.* --	gen_context(system_u:object_r:iceauth_home_t,s0)
 HOME_DIR/\.serverauth.*	--	gen_context(system_u:object_r:xauth_home_t,s0)
 HOME_DIR/\.xauth.*	--	gen_context(system_u:object_r:xauth_home_t,s0)
+HOME_DIR/\.xsession-errors	--	gen_context(system_u:object_r:xsession_log_t,s0)
 HOME_DIR/\.Xauthority.*	--	gen_context(system_u:object_r:xauth_home_t,s0)
 
 #
@@ -55,6 +56,7 @@ HOME_DIR/\.Xauthority.*	--	gen_context(system_u:object_r:xauth_home_t,s0)
 /tmp/\.X0-lock		--	gen_context(system_u:object_r:xserver_tmp_t,s0)
 /tmp/\.X11-unix		-d	gen_context(system_u:object_r:xdm_tmp_t,s0)
 /tmp/\.X11-unix/.*	-s	<<none>>
+/tmp/xses-%{USERNAME}	--	gen_context(system_u:object_r:xsession_log_t,s0)
 
 #
 # /usr
diff --git a/policy/modules/services/xserver.if b/policy/modules/services/xserver.if
index c1d41b5b..59d5821e 100644
--- a/policy/modules/services/xserver.if
+++ b/policy/modules/services/xserver.if
@@ -107,6 +107,10 @@ interface(`xserver_restricted_role',`
 	# Needed for escd, remove if we get escd policy
 	xserver_manage_xdm_tmp_files($2)
 
+	# for the .xsession-errors log file
+	xserver_user_home_dir_filetrans_user_xsession_log($2)
+	xserver_manage_xsession_log($2)
+
 	# Client write xserver shm
 	tunable_policy(`allow_write_xshm',`
 		allow $2 xserver_t:shm rw_shm_perms;
@@ -307,7 +311,7 @@ interface(`xserver_user_client',`
 
 	userdom_search_user_home_dirs($1)
 	# for .xsession-errors
-	userdom_dontaudit_write_user_home_content_files($1)
+	xserver_rw_xsession_log($1)
 
 	xserver_ro_session($1,$2)
 	xserver_use_user_fonts($1)
@@ -469,7 +473,7 @@ template(`xserver_user_x_domain_template',`
 
 	userdom_search_user_home_dirs($2)
 	# for .xsession-errors
-	userdom_dontaudit_write_user_home_content_files($2)
+	xserver_rw_xsession_log($2)
 
 	xserver_ro_session($2,$3)
 	xserver_use_user_fonts($2)
@@ -566,6 +570,25 @@ interface(`xserver_user_home_dir_filetrans_user_xauth',`
 
 ########################################
 ## <summary>
+##	Create a .xsession-errors log
+##	file in the user home directory.
+## </summary>
+## <param name="domain">
+##	<summary>
+##	Domain allowed access.
+##	</summary>
+## </param>
+#
+interface(`xserver_user_home_dir_filetrans_user_xsession_log',`
+	gen_require(`
+		type xsession_log_t;
+	')
+
+	userdom_user_home_dir_filetrans($1, xsession_log_t, file, ".xsession-errors")
+')
+
+########################################
+## <summary>
 ##	Read all users fonts, user font configurations,
 ##	and manage all users font caches.
 ## </summary>
@@ -1001,6 +1024,44 @@ interface(`xserver_xsession_spec_domtrans',`
 
 ########################################
 ## <summary>
+##	Read and write xsession log
+##	files such as .xsession-errors.
+## </summary>
+## <param name="domain">
+##	<summary>
+##	Domain allowed access.
+##	</summary>
+## </param>
+#
+interface(`xserver_rw_xsession_log',`
+	gen_require(`
+		type xsession_log_t;
+	')
+
+	allow $1 xsession_log_t:file rw_file_perms;
+')
+
+########################################
+## <summary>
+##	Manage xsession log files such
+##	as .xsession-errors.
+## </summary>
+## <param name="domain">
+##	<summary>
+##	Domain allowed access.
+##	</summary>
+## </param>
+#
+interface(`xserver_manage_xsession_log',`
+	gen_require(`
+		type xsession_log_t;
+	')
+
+	allow $1 xsession_log_t:file manage_file_perms;
+')
+
+########################################
+## <summary>
 ##	Get the attributes of X server logs.
 ## </summary>
 ## <param name="domain">
diff --git a/policy/modules/services/xserver.te b/policy/modules/services/xserver.te
index ba96a780..1956ddb2 100644
--- a/policy/modules/services/xserver.te
+++ b/policy/modules/services/xserver.te
@@ -210,6 +210,9 @@ userdom_user_tmpfs_file(xserver_tmpfs_t)
 type xsession_exec_t;
 corecmd_executable_file(xsession_exec_t)
 
+type xsession_log_t;
+userdom_user_home_content(xsession_log_t)
+
 # Type for the X server log file.
 type xserver_log_t;
 logging_log_file(xserver_log_t)