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Message-ID: <cfd18e0f0911140042n265b95adve2121e143c21c8ad@mail.gmail.com>
Date: Sat, 14 Nov 2009 09:42:33 +0100
From: Michael Kerrisk <mtk.manpages@...glemail.com>
To: James Morris <jmorris@...ei.org>
Cc: "Serge E. Hallyn" <serue@...ibm.com>,
linux-security-module@...r.kernel.org,
lkml <linux-kernel@...r.kernel.org>,
"Andrew G. Morgan" <morgan@...nel.org>,
Ulrich Drepper <drepper@...hat.com>,
Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH] define convenient securebits masks for prctl users (v2)
On Thu, Oct 29, 2009 at 10:51 PM, James Morris <jmorris@...ei.org> wrote:
> On Thu, 29 Oct 2009, Serge E. Hallyn wrote:
>
>> Hi James, would you mind taking the following into
>> security-testing?
>
>
> Applied to
> git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6#next
It doesn't look like this change is in 2.6.32-rc7. Is it planned to
push this out for 2.6.32?
Cheers,
Michael
>> The securebits are used by passing them to prctl with the
>> PR_{S,G}ET_SECUREBITS commands. But the defines must be
>> shifted to be used in prctl, which begs to be confused and
>> misused by userspace. So define some more convenient
>> values for userspace to specify. This way userspace does
>>
>> prctl(PR_SET_SECUREBITS, SECBIT_NOROOT);
>>
>> instead of
>>
>> prctl(PR_SET_SECUREBITS, 1 << SECURE_NOROOT);
>>
>> (Thanks to Michael for the idea)
>>
>> This patch also adds include/linux/securebits to the installed headers.
>> Then perhaps it can be included by glibc's sys/prctl.h.
>>
>> Changelog:
>> Oct 29: Stephen Rothwell points out that issecure can
>> be under __KERNEL__.
>> Oct 14: (Suggestions by Michael Kerrisk):
>> 1. spell out SETUID in SECBIT_NO_SETUID*
>> 2. SECBIT_X_LOCKED does not imply SECBIT_X
>> 3. add definitions for keepcaps
>> Oct 14: As suggested by Michael Kerrisk, don't
>> use SB_* as that convention is already in
>> use. Use SECBIT_ prefix instead.
>>
>> Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
>> Acked-by: Andrew G. Morgan <morgan@...nel.org>
>> Acked-by: Michael Kerrisk <mtk.manpages@...il.com>
>> Cc: Ulrich Drepper <drepper@...hat.com>
>> Cc: James Morris <jmorris@...ei.org>
>> ---
>> include/linux/Kbuild | 1 +
>> include/linux/securebits.h | 24 ++++++++++++++++++------
>> 2 files changed, 19 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/Kbuild b/include/linux/Kbuild
>> index 1feed71..5a53857 100644
>> --- a/include/linux/Kbuild
>> +++ b/include/linux/Kbuild
>> @@ -330,6 +330,7 @@ unifdef-y += scc.h
>> unifdef-y += sched.h
>> unifdef-y += screen_info.h
>> unifdef-y += sdla.h
>> +unifdef-y += securebits.h
>> unifdef-y += selinux_netlink.h
>> unifdef-y += sem.h
>> unifdef-y += serial_core.h
>> diff --git a/include/linux/securebits.h b/include/linux/securebits.h
>> index d2c5ed8..3340617 100644
>> --- a/include/linux/securebits.h
>> +++ b/include/linux/securebits.h
>> @@ -1,6 +1,15 @@
>> #ifndef _LINUX_SECUREBITS_H
>> #define _LINUX_SECUREBITS_H 1
>>
>> +/* Each securesetting is implemented using two bits. One bit specifies
>> + whether the setting is on or off. The other bit specify whether the
>> + setting is locked or not. A setting which is locked cannot be
>> + changed from user-level. */
>> +#define issecure_mask(X) (1 << (X))
>> +#ifdef __KERNEL__
>> +#define issecure(X) (issecure_mask(X) & current_cred_xxx(securebits))
>> +#endif
>> +
>> #define SECUREBITS_DEFAULT 0x00000000
>>
>> /* When set UID 0 has no special privileges. When unset, we support
>> @@ -12,6 +21,9 @@
>> #define SECURE_NOROOT 0
>> #define SECURE_NOROOT_LOCKED 1 /* make bit-0 immutable */
>>
>> +#define SECBIT_NOROOT (issecure_mask(SECURE_NOROOT))
>> +#define SECBIT_NOROOT_LOCKED (issecure_mask(SECURE_NOROOT_LOCKED))
>> +
>> /* When set, setuid to/from uid 0 does not trigger capability-"fixup".
>> When unset, to provide compatiblility with old programs relying on
>> set*uid to gain/lose privilege, transitions to/from uid 0 cause
>> @@ -19,6 +31,10 @@
>> #define SECURE_NO_SETUID_FIXUP 2
>> #define SECURE_NO_SETUID_FIXUP_LOCKED 3 /* make bit-2 immutable */
>>
>> +#define SECBIT_NO_SETUID_FIXUP (issecure_mask(SECURE_NO_SETUID_FIXUP))
>> +#define SECBIT_NO_SETUID_FIXUP_LOCKED \
>> + (issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED))
>> +
>> /* When set, a process can retain its capabilities even after
>> transitioning to a non-root user (the set-uid fixup suppressed by
>> bit 2). Bit-4 is cleared when a process calls exec(); setting both
>> @@ -27,12 +43,8 @@
>> #define SECURE_KEEP_CAPS 4
>> #define SECURE_KEEP_CAPS_LOCKED 5 /* make bit-4 immutable */
>>
>> -/* Each securesetting is implemented using two bits. One bit specifies
>> - whether the setting is on or off. The other bit specify whether the
>> - setting is locked or not. A setting which is locked cannot be
>> - changed from user-level. */
>> -#define issecure_mask(X) (1 << (X))
>> -#define issecure(X) (issecure_mask(X) & current_cred_xxx(securebits))
>> +#define SECBIT_KEEP_CAPS (issecure_mask(SECURE_KEEP_CAPS))
>> +#define SECBIT_KEEP_CAPS_LOCKED (issecure_mask(SECURE_KEEP_CAPS_LOCKED))
>>
>> #define SECURE_ALL_BITS (issecure_mask(SECURE_NOROOT) | \
>> issecure_mask(SECURE_NO_SETUID_FIXUP) | \
>> --
>> 1.6.1
>>
>
> --
> James Morris
> <jmorris@...ei.org>
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface" http://blog.man7.org/
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