From d76d9e13b188e9fd8df98e1e21d88aa45951860e Mon Sep 17 00:00:00 2001 From: Guido Trentalancia Date: Sat, 31 Dec 2016 17:43:46 +0100 Subject: [PATCH] xserver: restrict executable memory permissions The dangerous execheap permission is removed from xdm and the dangerous execmem permission is only enabled for the Gnome Display Manager (gnome-shell running in gdm mode) through a new "xserver_gnome_xdm" boolean. This patch also updates the XKB libs file context with their default location (which at the moment is not compliant with FHS3 due to the fact that it allows by default to write the output from xkbcomp), adds the ability to read udev pid files and finally adds a few permissions so that xconsole can run smoothly. The anomalous permission to execute XKB var library files has been removed and the old X11R6 library location has been updated so that subdirectories are also labeled as xkb_var_lib. This patch includes various improvements and bug fixes as kindly suggested in reviews made by Christopher PeBenito. Signed-off-by: Guido Trentalancia --- policy/modules/services/xserver.fc | 6 ++++-- policy/modules/services/xserver.te | 25 ++++++++++++++++--------- 2 files changed, 20 insertions(+), 11 deletions(-) diff --git a/policy/modules/services/xserver.fc b/policy/modules/services/xserver.fc index a875863c1..10d68b451 100644 --- a/policy/modules/services/xserver.fc +++ b/policy/modules/services/xserver.fc @@ -81,6 +81,9 @@ HOME_DIR/\.Xauthority.* -- gen_context(system_u:object_r:xauth_home_t,s0) /usr/sbin/lightdm -- gen_context(system_u:object_r:xdm_exec_t,s0) +# xserver default configure bug: not FHS-compliant because not read-only ! +/usr/share/X11/xkb(/.*)? gen_context(system_u:object_r:xkb_var_lib_t,s0) + /usr/X11R6/bin/[xgkw]dm -- gen_context(system_u:object_r:xdm_exec_t,s0) /usr/X11R6/bin/iceauth -- gen_context(system_u:object_r:iceauth_exec_t,s0) /usr/X11R6/bin/X -- gen_context(system_u:object_r:xserver_exec_t,s0) @@ -89,8 +92,7 @@ HOME_DIR/\.Xauthority.* -- gen_context(system_u:object_r:xauth_home_t,s0) /usr/X11R6/bin/Xipaq -- gen_context(system_u:object_r:xserver_exec_t,s0) /usr/X11R6/bin/Xorg -- gen_context(system_u:object_r:xserver_exec_t,s0) /usr/X11R6/bin/Xwrapper -- gen_context(system_u:object_r:xserver_exec_t,s0) -/usr/X11R6/lib/X11/xkb -d gen_context(system_u:object_r:xkb_var_lib_t,s0) -/usr/X11R6/lib/X11/xkb/.* -- gen_context(system_u:object_r:xkb_var_lib_t,s0) +/usr/X11R6/lib/X11/xkb(/.*)? gen_context(system_u:object_r:xkb_var_lib_t,s0) ifndef(`distro_debian',` /usr/var/[xgkw]dm(/.*)? gen_context(system_u:object_r:xserver_log_t,s0) diff --git a/policy/modules/services/xserver.te b/policy/modules/services/xserver.te index 40852e05a..ada685ea3 100644 --- a/policy/modules/services/xserver.te +++ b/policy/modules/services/xserver.te @@ -40,6 +40,14 @@ gen_tunable(allow_write_xshm, false) ## gen_tunable(xdm_sysadm_login, false) +## +##

+## Use gnome-shell in gdm mode as the +## X Display Manager (XDM) +##

+## +gen_tunable(xserver_gnome_xdm, false) + ## ##

## Support X userspace object manager @@ -307,6 +315,7 @@ optional_policy(` # allow xdm_t self:capability { setgid setuid sys_resource kill sys_tty_config mknod chown dac_override dac_read_search fowner fsetid ipc_owner sys_nice sys_rawio net_bind_service }; +dontaudit xdm_t self:capability sys_admin; allow xdm_t self:process { setexec setpgid getsched setsched setrlimit signal_perms }; allow xdm_t self:fifo_file rw_fifo_file_perms; allow xdm_t self:shm create_shm_perms; @@ -319,7 +328,7 @@ allow xdm_t self:socket create_socket_perms; allow xdm_t self:appletalk_socket create_socket_perms; allow xdm_t self:key { search link write }; -allow xdm_t xconsole_device_t:fifo_file { getattr setattr }; +allow xdm_t xconsole_device_t:fifo_file { read_fifo_file_perms setattr_fifo_file_perms }; # Allow gdm to run gdm-binary can_exec(xdm_t, xdm_exec_t) @@ -510,6 +519,10 @@ tunable_policy(`xdm_sysadm_login',` # allow xserver_t xdm_tmpfs_t:file rw_file_perms; ') +tunable_policy(`xserver_gnome_xdm',` + allow xdm_t self:process execmem; +') + optional_policy(` alsa_domtrans(xdm_t) ') @@ -589,10 +602,6 @@ optional_policy(` optional_policy(` unconfined_domain(xdm_t) unconfined_domtrans(xdm_t) - - ifndef(`distro_redhat',` - allow xdm_t self:process { execheap execmem }; - ') ') optional_policy(` @@ -658,6 +667,7 @@ manage_fifo_files_pattern(xserver_t, xserver_tmpfs_t, xserver_tmpfs_t) manage_sock_files_pattern(xserver_t, xserver_tmpfs_t, xserver_tmpfs_t) fs_tmpfs_filetrans(xserver_t, xserver_tmpfs_t, { dir file lnk_file sock_file fifo_file }) +# Run xkbcomp manage_files_pattern(xserver_t, xkb_var_lib_t, xkb_var_lib_t) manage_lnk_files_pattern(xserver_t, xkb_var_lib_t, xkb_var_lib_t) files_search_var_lib(xserver_t) @@ -806,6 +816,7 @@ optional_policy(` optional_policy(` udev_read_db(xserver_t) + udev_read_pid_files(xserver_t) ') optional_policy(` @@ -843,10 +854,6 @@ manage_files_pattern(xserver_t, xdm_tmp_t, xdm_tmp_t) manage_lnk_files_pattern(xserver_t, xdm_tmp_t, xdm_tmp_t) manage_sock_files_pattern(xserver_t, xdm_tmp_t, xdm_tmp_t) -# Run xkbcomp. -allow xserver_t xkb_var_lib_t:lnk_file read; -can_exec(xserver_t, xkb_var_lib_t) - # Run Xorg.wrap can_exec(xserver_t, xserver_exec_t)