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security: Define CAP_SYSLOG

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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).

Changelog: mar 12 2010: add selinux capability2:cap_syslog perm
Changelog: nov 22 2010:
	. port to new kernel
	. add a WARN_ONCE if userspace isn't using CAP_SYSLOG

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Andrew G. Morgan <morgan@kernel.org>
Acked-By: Kees Cook <kees.cook@canonical.com>
Cc: James Morris <jmorris@namei.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: "Christopher J. PeBenito" <cpebenito@tresys.com>
Cc: Eric Paris <eparis@parisplace.org>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Serge E. Hallyn 2010-11-25 17:11:32 +00:00 committed by James Morris
parent 1d6d75684d
commit ce6ada35bd
3 changed files with 13 additions and 4 deletions
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7
include/linux/capability.h
View file

@ -246,7 +246,6 @@ 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() */
@ -352,7 +351,11 @@ 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)

8
kernel/printk.c
View file

@ -283,9 +283,15 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
return -EPERM;
if ((type != SYSLOG_ACTION_READ_ALL &&
type != SYSLOG_ACTION_SIZE_BUFFER) &&
!capable(CAP_SYS_ADMIN))
!capable(CAP_SYSLOG)) {
/* remove after 2.6.38 */
if (capable(CAP_SYS_ADMIN))
WARN_ONCE(1, "Attempt to access syslog with "
"CAP_SYS_ADMIN but no CAP_SYSLOG "
"(deprecated and denied).\n");
return -EPERM;
}
}
error = security_syslog(type);
if (error)

2
security/selinux/include/classmap.h
View file

@ -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 } },