From: Micah Morton <mortonm@chromium.org> To: Kees Cook <keescook@chromium.org> Cc: jmorris@namei.org, serge@hallyn.com, casey@schaufler-ca.com, sds@tycho.nsa.gov, linux-security-module@vger.kernel.org Subject: Re: [PATCH] LSM: add SafeSetID module that gates setid calls Date: Thu, 6 Dec 2018 09:51:36 -0800 Message-ID: <CAJ-EccPf-u7PC2bzAzqFjz4-W5pFiLxSKcbKwkFYv8avfPdu3g@mail.gmail.com> (raw) In-Reply-To: <CAGXu5jJCk8p_nkuutM0kPLhwibKEVoA6E=ZqT2r8jVK5H47ORQ@mail.gmail.com> On Wed, Dec 5, 2018 at 4:08 PM Kees Cook <keescook@chromium.org> wrote: > > On Wed, Nov 21, 2018 at 8:54 AM <mortonm@chromium.org> wrote: > > > > From: Micah Morton <mortonm@chromium.org> > > > > SafeSetID gates the setid family of syscalls to restrict UID/GID > > transitions from a given UID/GID to only those approved by a > > system-wide whitelist. These restrictions also prohibit the given > > UIDs/GIDs from obtaining auxiliary privileges associated with > > CAP_SET{U/G}ID, such as allowing a user to set up user namespace UID > > mappings. For now, only gating the set*uid family of syscalls is > > supported, with support for set*gid coming in a future patch set. > > > > Signed-off-by: Micah Morton <mortonm@chromium.org> > > --- > > > > Sending a patch developed against the 'next-general' branch of the > > linux-security tree, since the previous patch versions wouldn't apply > > cleanly to 'next-general'. > > I'm finally getting back around to this. Sorry for the delay! > > A few general process notes: > - Please "version" your patches in the Subject (e.g. "[PATCH v3] LSM: > add SafeSetID ..."). This helps track discussion. > - Please include a "changes since last version below the first "---" > line, to summarize what has changed. This makes review faster for > people that have read a specific version but need to catch up (like > me) :) Ok thanks, will do in the future. The only code change since the initial upload was to add a do_exit(SIGKILL) line to setuid_policy_warning() in lsm.c, which will kill any process that violates the whitelist policy. This way, there can never be a case where a privileged program fails to drop privilege because of our whitelist and continues running in an accidentally over-privileged context. > > > +/* > > + * TODO: Figuring out whether the current syscall number (saved on the kernel > > + * stack) is one of the set*uid syscalls is an operation that requires checking > > + * the number against arch-specific constants as seen below. The need for this > > + * LSM to know about arch-specific syscall stuff is not ideal. Is it better to > > + * implement an arch-specific function that gets called from this file and > > + * update arch/Kconfig to mention that the HAVE_SAFESETID symbol should only be > > + * selected for architectures that implement the function? Any other ideas? > > + */ > > What would Stephen's solution for this problem end up looking like? I > think avoiding the arch-specific-ness would be quite valuable. I sent a patch here that is an example of how it could be done: https://www.spinics.net/lists/linux-security-module/msg24504.html. AFAICT I think this is what Stephen had in mind. > > I think adding a capability for this isn't the way to go (there is a > very painful history on adding capabilities). This feels much more > like a good mapping to an LSM (it's narrowing a privilege) with a very > specific policy. > > -- > Kees Cook
next prev parent 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 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 [this message] 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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