Re: [PATCH] exporting capability code/name pairs (try #4)

Serge E. Hallyn
2008-02-12T18:09:25Z

Quoting Kohei KaiGai (kaigai@ak.jp.nec.com):
> This patch enables to export code/name pair of capabilities supported
> on the running kernel, under the /sys/kernel/capability .
> We can apply it onto the latest Linus's git tree.
>
> Changes from the previous version:
> - I added "names/" ans "codes/" directories, and we can use them
> to lookup capability code or name non-sequentially.
> In the previous version, we had to scan whole of entries to lookup
> capability name by its code.
> (required by Andrew Morgan)
> - I added an assertion when "mkcapname.sh" works incorrectly.
> (required by Serge E.Hallyn)
>
> In addition, Andrew suggested me to export these translation by symlinks
> to reduce the number of invocation of system call.
> However, current sysfs interface does not allows to create symlinks with
> invalid indication.
> Thus, this patch exports them as regular files.
>
> --------------------------------------------------------
> [kaigai@saba ~]$ ls -R /sys/kernel/capability/
> /sys/kernel/capability/:
> codes names version
>
> /sys/kernel/capability/codes:
> 0 10 12 14 16 18 2 21 23 25 27 29 30 32 4 6 8
> 1 11 13 15 17 19 20 22 24 26 28 3 31 33 5 7 9
>
> /sys/kernel/capability/names:
> cap_audit_control cap_kill cap_net_raw cap_sys_nice
> cap_audit_write cap_lease cap_setfcap cap_sys_pacct
> cap_chown cap_linux_immutable cap_setgid cap_sys_ptrace
> cap_dac_override cap_mac_admin cap_setpcap cap_sys_rawio
> cap_dac_read_search cap_mac_override cap_setuid cap_sys_resource
> cap_fowner cap_mknod cap_sys_admin cap_sys_time
> cap_fsetid cap_net_admin cap_sys_boot cap_sys_tty_config
> cap_ipc_lock cap_net_bind_service cap_sys_chroot
> cap_ipc_owner cap_net_broadcast cap_sys_module
> [kaigai@saba ~]$ cat /sys/kernel/capability/codes/20
> cap_sys_pacct
> [kaigai@saba ~]$ cat /sys/kernel/capability/names/cap_mknod
> 27
> [kaigai@saba ~]$
> --------------------------------------------------------
> Any comment please.
>
> Thanks,
>
> Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
> ----
> scripts/mkcapnames.sh | 44 +++++++++++++++++++
> security/Kconfig | 9 ++++
> security/Makefile | 11 +++++
> security/capability.c | 115 +++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 179 insertions(+), 0 deletions(-)
>
> diff --git a/scripts/mkcapnames.sh b/scripts/mkcapnames.sh
> index e69de29..9e7290f 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/Kconfig b/security/Kconfig
> index 25ffe1b..b79e830 100644
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -91,6 +91,15 @@ config SECURITY_FILE_CAPABILITIES
>
> If in doubt, answer N.
>
> +config SECURITY_CAPABILITIES_EXPORT
> + bool "Exporting capabilities kernel supported"
> + depends on SECURITY_CAPABILITIES && SYSFS

Oh no, we're being bit by this again... When SECURITY=n, capabilities
are compiled in but SECURITY_CAPABILITIES=n.

Months ago I floated the following patch so we'd have a CONFIG variable
to let us know whether commoncap is compiled in. You might want to use
this and depend on CONFIG_COMMONCAP? (Though really I personally don't
think you need your own config variable for this)

Other than that, this tested fine for me.

thanks,
-serge

>From 54c70ca7671750fe8986451fae91d42107d0ca90 Mon Sep 17 00:00:00 2001
From: Serge E. Hallyn <serue@us.ibm.com>
Date: Fri, 28 Sep 2007 10:33:33 -0500
Subject: [PATCH 1/2] capabilities: define CONFIG_COMMONCAP

currently the compilation of commoncap.c is determined
through Makefile logic. So there is no single CONFIG
variable which can be relied upon to know whether it
will be compiled.

Define CONFIG_COMMONCAP to be true when lsm is not
compiled in, or when the capability or rootplug modules
are compiled. These are the cases when commoncap is
currently compiled. Use this variable in security/Makefile
to determine commoncap.c's compilation.

Apart from being a logic cleanup, this is needed by the
upcoming cap_bset patch so that prctl can know whether
PR_SET_BSET should be allowed.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
---
security/Kconfig | 4 ++++
security/Makefile | 9 +++------
2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/security/Kconfig b/security/Kconfig
index 8086e61..02b33fa 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -103,6 +103,10 @@ config SECURITY_ROOTPLUG

If you are unsure how to answer this question, answer N.

+config COMMONCAP
+ bool
+ default !SECURITY || SECURITY_CAPABILITIES || SECURITY_ROOTPLUG
+
source security/selinux/Kconfig

endmenu
diff --git a/security/Makefile b/security/Makefile
index ef87df2..7cccc81 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -5,14 +5,11 @@
obj-$(CONFIG_KEYS) += keys/
subdir-$(CONFIG_SECURITY_SELINUX) += selinux

-# if we don't select a security model, use the default capabilities
-ifneq ($(CONFIG_SECURITY),y)
-obj-y += commoncap.o
-endif
+obj-$(CONFIG_COMMONCAP) += commoncap.o

# Object file lists
obj-$(CONFIG_SECURITY) += security.o dummy.o inode.o
# Must precede capability.o in order to stack properly.
obj-$(CONFIG_SECURITY_SELINUX) += selinux/built-in.o
-obj-$(CONFIG_SECURITY_CAPABILITIES) += commoncap.o capability.o
-obj-$(CONFIG_SECURITY_ROOTPLUG) += commoncap.o root_plug.o
+obj-$(CONFIG_SECURITY_CAPABILITIES) += capability.o
+obj-$(CONFIG_SECURITY_ROOTPLUG) += root_plug.o
--
1.5.1.1.GIT