Privileged syslog operations currently require CAP_SYS_ADMIN. Split
this off into a new CAP_SYSLOG privilege which we can sanely take away
from a container through the capability bounding set.
With this patch, an lxc container can be prevented from messing with
the host's syslog (i.e. dmesg -c).
There is one downside to this patch: If some site or distro currently
has syslogd/whatever running as a non-root user with cap_sys_admin+pe,
then it will need to be changed to run with cap_syslog+pe. I don't
know if there are such sites, or if that concern means we should take
a different approach to introducing this change, or simply refuse this
change.
I'm also sending out corresponding patches for libcap and refpolicy, and
will whip up a man-pages patch next week.
Changelog: mar 12 2010: add selinux capability2:cap_syslog perm
Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx>
Acked-by: Andrew G. Morgan <morgan@xxxxxxxxxx>
Acked-By: Kees Cook <kees.cook@xxxxxxxxxxxxx>
Cc: James Morris <jmorris@xxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Stephen Smalley <sds@xxxxxxxxxxxxx>
Cc: "Christopher J. PeBenito" <cpebenito@xxxxxxxxxx>
Cc: Eric Paris <eparis@xxxxxxxxxxxxxx>
---
include/linux/capability.h | 7 +++++--
security/commoncap.c | 2 +-
security/selinux/include/classmap.h | 2 +-
3 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/include/linux/capability.h b/include/linux/capability.h
index 39e5ff5..837a55c 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -249,7 +249,6 @@ struct cpu_vfs_cap_data {
/* Allow configuration of the secure attention key */
/* Allow administration of the random device */
/* Allow examination and configuration of disk quotas */
-/* Allow configuring the kernel's syslog (printk behaviour) */
/* Allow setting the domainname */
/* Allow setting the hostname */
/* Allow calling bdflush() */
@@ -355,7 +354,11 @@ struct cpu_vfs_cap_data {
#define CAP_MAC_ADMIN 33
-#define CAP_LAST_CAP CAP_MAC_ADMIN
+/* Allow configuring the kernel's syslog (printk behaviour) */
+
+#define CAP_SYSLOG 34
+
+#define CAP_LAST_CAP CAP_SYSLOG
#define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
diff --git a/security/commoncap.c b/security/commoncap.c
index 6166973..018985e 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -899,7 +899,7 @@ int cap_syslog(int type, bool from_file)
if (type != SYSLOG_ACTION_OPEN && from_file)
return 0;
if ((type != SYSLOG_ACTION_READ_ALL &&
- type != SYSLOG_ACTION_SIZE_BUFFER) && !capable(CAP_SYS_ADMIN))
+ type != SYSLOG_ACTION_SIZE_BUFFER) && !capable(CAP_SYSLOG))
return -EPERM;
return 0;
}
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 8b32e95..f03cf56 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -142,7 +142,7 @@ struct security_class_mapping secclass_map[] = {
"node_bind", "name_connect", NULL } },
{ "memprotect", { "mmap_zero", NULL } },
{ "peer", { "recv", NULL } },
- { "capability2", { "mac_override", "mac_admin", NULL } },
+ { "capability2", { "mac_override", "mac_admin", "syslog", NULL } },
{ "kernel_service", { "use_as_override", "create_files_as", NULL } },
{ "tun_socket",
{ COMMON_SOCK_PERMS, NULL } },
--
1.6.1
--
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