From 14f74809348227ad07d1d934d747f7218c7e21a3 Mon Sep 17 00:00:00 2001 From: Daniel Micay Date: Fri, 29 Jul 2016 14:48:19 -0400 Subject: [PATCH] restrict access to timing information in /proc These APIs expose sensitive information via timing side channels. This leaves access via the adb shell intact along with the current uses by dumpstate, init and system_server. The /proc/interrupts and /proc/stat files were covered in this paper: https://www.lightbluetouchpaper.org/2016/07/29/yet-another-android-side-channel/ The /proc/softirqs, /proc/timer_list and /proc/timer_stats files are also relevant. Access to /proc has been greatly restricted since then, with untrusted apps no longer having direct access to these, but stricter restrictions beyond that would be quite useful. Change-Id: Ibed16674856569d26517e5729f0f194b830cfedd --- dumpstate.te | 1 + file.te | 3 +++ genfs_contexts | 5 +++++ init.te | 3 +++ shell.te | 3 +++ system_server.te | 3 +++ 6 files changed, 18 insertions(+) diff --git a/dumpstate.te b/dumpstate.te index 0b1f97bd6..71c12461c 100644 --- a/dumpstate.te +++ b/dumpstate.te @@ -188,6 +188,7 @@ allow dumpstate debugfs_tracing:dir r_dir_perms; allow dumpstate debugfs_tracing:file rw_file_perms; allow dumpstate debugfs_trace_marker:file getattr; allow dumpstate atrace_exec:file rx_file_perms; +allow dumpstate proc_interrupts:file r_file_perms; # Access to /data/media. # This should be removed if sdcardfs is modified to alter the secontext for its diff --git a/file.te b/file.te index 446c1829c..6099eb581 100644 --- a/file.te +++ b/file.te @@ -13,10 +13,13 @@ type usermodehelper, fs_type, sysfs_type; type qtaguid_proc, fs_type, mlstrustedobject; type proc_bluetooth_writable, fs_type; type proc_cpuinfo, fs_type; +type proc_interrupts, fs_type; type proc_iomem, fs_type; type proc_meminfo, fs_type; type proc_net, fs_type; +type proc_stat, fs_type; type proc_sysrq, fs_type; +type proc_timer, fs_type; type proc_uid_cputime_showstat, fs_type; type proc_uid_cputime_removeuid, fs_type; type selinuxfs, fs_type, mlstrustedobject; diff --git a/genfs_contexts b/genfs_contexts index 31794a1e8..612cc5b70 100644 --- a/genfs_contexts +++ b/genfs_contexts @@ -2,11 +2,14 @@ genfscon rootfs / u:object_r:rootfs:s0 # proc labeling can be further refined (longest matching prefix). genfscon proc / u:object_r:proc:s0 +genfscon proc /interrupts u:object_r:proc_interrupts:s0 genfscon proc /iomem u:object_r:proc_iomem:s0 genfscon proc /meminfo u:object_r:proc_meminfo:s0 genfscon proc /net u:object_r:proc_net:s0 genfscon proc /net/xt_qtaguid/ctrl u:object_r:qtaguid_proc:s0 genfscon proc /cpuinfo u:object_r:proc_cpuinfo:s0 +genfscon proc /softirqs u:object_r:proc_timer:s0 +genfscon proc /stat u:object_r:proc_stat:s0 genfscon proc /sysrq-trigger u:object_r:proc_sysrq:s0 genfscon proc /sys/fs/protected_hardlinks u:object_r:proc_security:s0 genfscon proc /sys/fs/protected_symlinks u:object_r:proc_security:s0 @@ -23,6 +26,8 @@ genfscon proc /sys/kernel/usermodehelper u:object_r:usermodehelper:s0 genfscon proc /sys/net u:object_r:proc_net:s0 genfscon proc /sys/vm/mmap_min_addr u:object_r:proc_security:s0 genfscon proc /sys/vm/drop_caches u:object_r:proc_drop_caches:s0 +genfscon proc /timer_list u:object_r:proc_timer:s0 +genfscon proc /timer_stats u:object_r:proc_timer:s0 genfscon proc /uid_cputime/show_uid_stat u:object_r:proc_uid_cputime_showstat:s0 genfscon proc /uid_cputime/remove_uid_range u:object_r:proc_uid_cputime_removeuid:s0 diff --git a/init.te b/init.te index 9bc78d173..4e14d97e1 100644 --- a/init.te +++ b/init.te @@ -155,6 +155,9 @@ allow init self:capability net_admin; # Write to /proc/sysrq-trigger. allow init proc_sysrq:file w_file_perms; +# Read /proc/stat for bootchart. +allow init proc_stat:file r_file_perms; + # Reboot. allow init self:capability sys_boot; diff --git a/shell.te b/shell.te index 3e95b4687..69e9c113a 100644 --- a/shell.te +++ b/shell.te @@ -96,7 +96,10 @@ allow shell { service_manager_type -gatekeeper_service -netd_service }:service_m # allow shell to look through /proc/ for ps, top, netstat r_dir_file(shell, proc) r_dir_file(shell, proc_net) +allow shell proc_interrupts:file r_file_perms; allow shell proc_meminfo:file r_file_perms; +allow shell proc_stat:file r_file_perms; +allow shell proc_timer:file r_file_perms; r_dir_file(shell, cgroup) allow shell domain:dir { search open read getattr }; allow shell domain:{ file lnk_file } { open read getattr }; diff --git a/system_server.te b/system_server.te index db59b6573..334cb9144 100644 --- a/system_server.te +++ b/system_server.te @@ -107,6 +107,9 @@ allow system_server proc_uid_cputime_removeuid:file { w_file_perms getattr }; # Write to /proc/sysrq-trigger. allow system_server proc_sysrq:file rw_file_perms; +# Read /proc/stat for CPU usage statistics +allow system_server proc_stat:file r_file_perms; + # Read /sys/kernel/debug/wakeup_sources. allow system_server debugfs:file r_file_perms;