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From: "Serge E. Hallyn" <serge@hallyn.com>
To: Casey Schaufler <casey@schaufler-ca.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>,
	Micah Morton <mortonm@chromium.org>,
	jmorris@namei.org, Kees Cook <keescook@chromium.org>,
	linux-security-module@vger.kernel.org
Subject: Re: [PATCH] LSM: add SafeSetID module that gates setid calls
Date: Fri, 2 Nov 2018 19:22:27 +0000
Message-ID: <20181102192227.GA21498@mail.hallyn.com> (raw)
In-Reply-To: <b1f95526-d0f1-712e-e0a7-9710cae7e1f0@schaufler-ca.com>

Quoting Casey Schaufler (casey@schaufler-ca.com):
> On 11/2/2018 11:30 AM, Serge E. Hallyn wrote:
> > Quoting Casey Schaufler (casey@schaufler-ca.com):
> >
> >> Let me suggest a change to the way your LSM works
> >> that would reduce my concerns. Rather than refusing to
> >> make a UID change that isn't on your whitelist, kill a
> >> process that makes a prohibited request. This mitigates
> >> the problem where a process doesn't check for an error
> >> return. Sure, your system will be harder to get running
> >> until your whitelist is complete, but you'll avoid a
> >> whole category of security bugs.
> > Might also consider not restricting CAP_SETUID, but instead adding a
> > new CAP_SETUID_RANGE capability.  That way you can be sure there will be
> > no regressions with any programs which run with CAP_SETUID.
> >
> > Though that violates what Casey was just arguing halfway up the email.
> 
> I know that it's hard to believe 20 years after the fact,
> but the POSIX group worked very hard to ensure that the granularity
> of capabilities was correct for the security policy that the
> interfaces defined in P1003.1. What would CAP_SETUID_RANGE mean?

CAP_SETUID would mean you can switch to any uid.

CAP_SETUID_RANGE would mean you could make the transitions which have
been defined through <handwave> some mechanism.  Be it prctl, or some
new security.uidrange xattr, or the mechanism Micah proposed, except
it only applies for CAP_SETUID_RANGE not CAP_SETUID.

-serge

  reply index

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-31 15:28 mortonm
2018-10-31 21:02 ` Serge E. Hallyn
2018-10-31 21:57   ` Kees Cook
2018-10-31 22:37     ` Casey Schaufler
2018-11-01  1:12       ` Micah Morton
2018-11-01  6:13         ` Serge E. Hallyn
2018-11-01 15:39           ` Casey Schaufler
2018-11-01 15:56             ` Serge E. Hallyn
2018-11-01 16:18             ` Micah Morton
2018-11-01  6:07   ` Serge E. Hallyn
2018-11-01 16:11     ` Micah Morton
2018-11-01 16:22       ` Micah Morton
2018-11-01 16:41       ` Micah Morton
2018-11-01 17:08       ` Casey Schaufler
2018-11-01 19:52         ` Micah Morton
2018-11-02 16:05           ` Casey Schaufler
2018-11-02 17:12             ` Micah Morton
2018-11-02 18:19               ` Casey Schaufler
2018-11-02 18:30                 ` Serge E. Hallyn
2018-11-02 19:02                   ` Casey Schaufler
2018-11-02 19:22                     ` Serge E. Hallyn [this message]
2018-11-08 20:53                       ` Micah Morton
2018-11-08 21:34                         ` Casey Schaufler
2018-11-09  0:30                           ` Micah Morton
2018-11-09 23:21                             ` [PATCH] LSM: generalize flag passing to security_capable mortonm
2018-11-21 16:54                             ` [PATCH] LSM: add SafeSetID module that gates setid calls mortonm
2018-12-06  0:08                               ` Kees Cook
2018-12-06 17:51                                 ` Micah Morton
2019-01-11 17:13                                 ` [PATCH v2] " mortonm
2019-01-15  0:38                                   ` Kees Cook
2019-01-15 18:04                                     ` [PATCH v3 1/2] LSM: mark all set*uid call sites in kernel/sys.c mortonm
2019-01-15 19:34                                       ` Kees Cook
2019-01-15 18:04                                     ` [PATCH v3 2/2] LSM: add SafeSetID module that gates setid calls mortonm
2019-01-15 19:44                                       ` Kees Cook
2019-01-15 21:50                                         ` [PATCH v4 " mortonm
2019-01-15 22:32                                           ` Kees Cook
2019-01-16 15:46                                             ` [PATCH v5 " mortonm
2019-01-16 16:10                                               ` Casey Schaufler
2019-01-22 20:40                                                 ` Micah Morton
2019-01-22 22:28                                                   ` James Morris
2019-01-22 22:40                                                     ` Micah Morton
2019-01-22 22:42                                                       ` [PATCH v3 1/2] " mortonm
2019-01-25 15:51                                                         ` Micah Morton
2019-01-25 20:15                                               ` [PATCH v5 2/2] " James Morris
2019-01-25 21:06                                                 ` Micah Morton
2019-01-28 19:47                                                   ` Micah Morton
2019-01-28 19:56                                                     ` Kees Cook
2019-01-28 20:09                                                       ` James Morris
2019-01-28 20:19                                                       ` Micah Morton
2019-01-28 20:30                                                         ` [PATCH] LSM: Add 'name' field for SafeSetID in DEFINE_LSM mortonm
2019-01-28 22:12                                                           ` James Morris
2019-01-28 22:33                                                         ` [PATCH v5 2/2] LSM: add SafeSetID module that gates setid calls Micah Morton
2019-01-29 17:25                                                           ` James Morris
2019-01-29 21:14                                                             ` Micah Morton
2019-01-30  7:15                                                               ` Kees Cook
2019-02-06 19:03                                                                 ` [PATCH] LSM: SafeSetID: add selftest mortonm
2019-02-06 19:26                                                                   ` Edwin Zimmerman
2019-02-07 21:54                                                                     ` Micah Morton
2019-02-12 19:01                                                                   ` James Morris
2019-01-15 21:58                                         ` [PATCH v3 2/2] LSM: add SafeSetID module that gates setid calls Micah Morton
2019-01-15 19:49                                     ` [PATCH v2] " Micah Morton
2019-01-15 19:53                                       ` Kees Cook
2019-01-15  4:07                                   ` James Morris
2019-01-15 19:42                                     ` Micah Morton
2018-11-02 19:28                 ` [PATCH] " Micah Morton
2018-11-06 19:09                 ` [PATCH v2] " mortonm
2018-11-06 20:59       ` [PATCH] " James Morris
2018-11-06 21:21         ` [PATCH v3] " mortonm
2018-11-02 18:07 ` [PATCH] " Stephen Smalley
2018-11-02 19:13   ` Micah Morton
2018-11-19 18:54   ` [PATCH] [PATCH] LSM: generalize flag passing to security_capable mortonm
2018-12-13 22:29     ` Micah Morton
2018-12-13 23:09       ` Casey Schaufler
2018-12-14  0:05         ` Micah Morton
2018-12-18 22:37         ` [PATCH v2] " mortonm
2019-01-07 17:55           ` Micah Morton
2019-01-07 18:16             ` Casey Schaufler
2019-01-07 18:36               ` Micah Morton
2019-01-07 18:46                 ` Casey Schaufler
2019-01-07 19:02                   ` Micah Morton
2019-01-07 22:57                     ` [PATCH v3] " mortonm
2019-01-07 23:13           ` [PATCH v2] " Kees Cook
2019-01-08  0:10             ` [PATCH v4] " mortonm
2019-01-08  0:20               ` Kees Cook
2019-01-09 18:39                 ` Micah Morton
2019-01-10 22:31               ` James Morris
2019-01-10 23:03                 ` Micah Morton
2019-01-08  0:10             ` [PATCH v2] " Micah Morton

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