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Date: Mon, 25 Feb 2008 15:10:43 +0900
From: Kohei KaiGai <kaigai@...jp.nec.com>
To: greg@...ah.com, morgan@...nel.org, serue@...ibm.com
CC: Kohei KaiGai <kaigai@...jp.nec.com>,
linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] exporting capability name/code pairs (final#2)
[PATCH 2/3] exporting capability name/code pairs
This patch enables to export code/name pairs of capabilities the running
kernel supported.
A newer kernel sometimes adds new capabilities, like CAP_MAC_ADMIN
at 2.6.25. However, we have no interface to disclose what capabilities
are supported on the running kernel. Thus, we have to maintain libcap
version in appropriate one synchronously.
This patch enables libcap to collect the list of capabilities at run time,
and provide them for users. It helps to improve portability of library.
It exports these information as regular files under /sys/kernel/capability.
The numeric node exports its name, the symbolic node exports its code.
Signed-off-by: KaiGai Kohei <kaigai@...jp.nec.com>
--
Documentation/ABI/testing/sysfs-kernel-capability | 23 +++++
scripts/mkcapnames.sh | 44 +++++++++
security/Makefile | 9 ++
security/commoncap.c | 99 +++++++++++++++++++++
4 files changed, 175 insertions(+), 0 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-kernel-capability b/Documentation/ABI/testing/sysfs-kernel-capability
index e69de29..d4a14e7 100644
--- a/Documentation/ABI/testing/sysfs-kernel-capability
+++ b/Documentation/ABI/testing/sysfs-kernel-capability
@@ -0,0 +1,23 @@
+What: /sys/kernel/capability
+Date: Feb 2008
+Contact: KaiGai Kohei <kaigai@...jp.nec.com>
+Description:
+ The entries under /sys/kernel/capability are used to export
+ the list of capabilities the running kernel supports.
+
+ - /sys/kernel/capability/version
+ returns the most preferable version number for the
+ running kernel.
+ e.g) $ cat /sys/kernel/capability/version
+ 0x20071026
+
+ - /sys/kernel/capability/code/<numerical representation>
+ returns its symbolic representation, on reading.
+ e.g) $ cat /sys/kernel/capability/codes/30
+ cap_audit_control
+
+ - /sys/kernel/capability/name/<symbolic representation>
+ returns its numerical representation, on reading.
+ e.g) $ cat /sys/kernel/capability/names/cap_sys_pacct
+ 20
+
diff --git a/scripts/mkcapnames.sh b/scripts/mkcapnames.sh
index e69de29..5d36d52 100644
--- a/scripts/mkcapnames.sh
+++ b/scripts/mkcapnames.sh
@@ -0,0 +1,44 @@
+#!/bin/sh
+
+#
+# generate a cap_names.h file from include/linux/capability.h
+#
+
+CAPHEAD="`dirname $0`/../include/linux/capability.h"
+REGEXP='^#define CAP_[A-Z_]+[ ]+[0-9]+$'
+NUMCAP=`cat "$CAPHEAD" | egrep -c "$REGEXP"`
+
+echo '#ifndef CAP_NAMES_H'
+echo '#define CAP_NAMES_H'
+echo
+echo '/*'
+echo ' * Do NOT edit this file directly.'
+echo ' * This file is generated from include/linux/capability.h automatically'
+echo ' */'
+echo
+echo '#if !defined(SYSFS_CAP_NAME_ENTRY) || !defined(SYSFS_CAP_CODE_ENTRY)'
+echo '#error cap_names.h should be included from security/capability.c'
+echo '#else'
+echo "#if $NUMCAP != CAP_LAST_CAP + 1"
+echo '#error mkcapnames.sh cannot collect capabilities correctly'
+echo '#else'
+cat "$CAPHEAD" | egrep "$REGEXP" \
+ | awk '{ printf("SYSFS_CAP_NAME_ENTRY(%s,%s);\n", tolower($2), $2); }'
+echo
+echo 'static struct attribute *capability_name_attrs[] = {'
+cat "$CAPHEAD" | egrep "$REGEXP" \
+ | awk '{ printf("\t&%s_name_attr.attr,\n", tolower($2)); } END { print "\tNULL," }'
+echo '};'
+
+echo
+cat "$CAPHEAD" | egrep "$REGEXP" \
+ | awk '{ printf("SYSFS_CAP_CODE_ENTRY(%s,%s);\n", tolower($2), $2); }'
+echo
+echo 'static struct attribute *capability_code_attrs[] = {'
+cat "$CAPHEAD" | egrep "$REGEXP" \
+ | awk '{ printf("\t&%s_code_attr.attr,\n", tolower($2)); } END { print "\tNULL," }'
+echo '};'
+
+echo '#endif'
+echo '#endif'
+echo '#endif'
diff --git a/security/Makefile b/security/Makefile
index 9e8b025..4093e3e 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -18,3 +18,12 @@ obj-$(CONFIG_SECURITY_SELINUX) += selinux/built-in.o
obj-$(CONFIG_SECURITY_SMACK) += commoncap.o smack/built-in.o
obj-$(CONFIG_SECURITY_CAPABILITIES) += commoncap.o capability.o
obj-$(CONFIG_SECURITY_ROOTPLUG) += commoncap.o root_plug.o
+
+# cap_names.h contains the code/name pair of capabilities.
+# It is generated using include/linux/capability.h automatically.
+$(obj)/commoncap.o: $(obj)/cap_names.h
+quiet_cmd_cap_names = CAPS $@
+ cmd_cap_names = /bin/sh $(srctree)/scripts/mkcapnames.sh > $@
+targets += cap_names.h
+$(obj)/cap_names.h: $(srctree)/scripts/mkcapnames.sh $(srctree)/include/linux/capability.h FORCE
+ $(call if_changed,cap_names)
diff --git a/security/commoncap.c b/security/commoncap.c
index 5aba826..9483fa9 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -24,6 +24,8 @@
#include <linux/hugetlb.h>
#include <linux/mount.h>
#include <linux/sched.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
/* Global security state */
@@ -637,3 +639,100 @@ int cap_vm_enough_memory(struct mm_struct *mm, long pages)
return __vm_enough_memory(mm, pages, cap_sys_admin);
}
+/*
+ * Export the list of capabilities on /sys/kernel/capability
+ */
+static struct kobject *capability_kobj;
+
+static ssize_t capability_name_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buffer)
+{
+ /* It returns numerical representation of capability. */
+ return scnprintf(buffer, PAGE_SIZE, "%ld\n", (long) attr->data);
+}
+
+static ssize_t capability_code_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buffer)
+{
+ /* It returns symbolic representation of capability. */
+ return scnprintf(buffer, PAGE_SIZE, "%s\n", (char *) attr->data);
+}
+
+static ssize_t capability_version_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buffer)
+{
+ return scnprintf(buffer, PAGE_SIZE, "0x%08x\n",
+ _LINUX_CAPABILITY_VERSION);
+}
+
+#define SYSFS_CAP_NAME_ENTRY(_name,_code) \
+ static struct kobj_attribute _name##_name_attr = \
+ __ATTR_DATA(_name, 0444, capability_name_show, NULL, (long)(_code))
+
+#define SYSFS_CAP_CODE_ENTRY(_name,_code) \
+ static struct kobj_attribute _name##_code_attr = \
+ __ATTR_DATA(_code, 0444, capability_code_show, NULL, __stringify(_name))
+
+/*
+ * capability_attrs[] is generated automatically by scripts/mkcapnames.sh
+ * This script parses include/linux/capability.h
+ */
+#include "cap_names.h"
+
+static struct attribute_group capability_name_attr_group = {
+ .name = "names",
+ .attrs = capability_name_attrs,
+};
+
+static struct attribute_group capability_code_attr_group = {
+ .name = "codes",
+ .attrs = capability_code_attrs,
+};
+
+static struct kobj_attribute cap_version_attr =
+ __ATTR(version, 0444, capability_version_show, NULL);
+
+static int __init capability_export_names(void)
+{
+ int rc = -ENOMEM;
+
+ /* make /sys/kernel/capability */
+ capability_kobj = kobject_create_and_add("capability", kernel_kobj);
+ if (!capability_kobj)
+ goto error0;
+
+ /* make /sys/kernel/capability/names */
+ rc = sysfs_create_group(capability_kobj,
+ &capability_name_attr_group);
+ if (rc)
+ goto error1;
+
+ /* make /sys/kernel/capability/codes */
+ rc = sysfs_create_group(capability_kobj,
+ &capability_code_attr_group);
+ if (rc)
+ goto error2;
+
+ /* make /sys/kernel/capability/version */
+ rc = sysfs_create_file(capability_kobj,
+ &cap_version_attr.attr);
+ if (rc)
+ goto error3;
+
+ return 0;
+
+error3:
+ sysfs_remove_group(capability_kobj, &capability_code_attr_group);
+error2:
+ sysfs_remove_group(capability_kobj, &capability_name_attr_group);
+error1:
+ kobject_put(capability_kobj);
+error0:
+ printk(KERN_ERR "Unable to export capabilities\n");
+
+ return rc;
+}
+__initcall(capability_export_names);
--
OSS Platform Development Division, NEC
KaiGai Kohei <kaigai@...jp.nec.com>
--
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