From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5723C433EF for ; Sun, 26 Jun 2022 23:33:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229468AbiFZXd4 (ORCPT ); Sun, 26 Jun 2022 19:33:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50262 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229492AbiFZXd4 (ORCPT ); Sun, 26 Jun 2022 19:33:56 -0400 Received: from mail.hallyn.com (mail.hallyn.com [178.63.66.53]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 856942BEC; Sun, 26 Jun 2022 16:33:54 -0700 (PDT) Received: by mail.hallyn.com (Postfix, from userid 1001) id 0617E113A; Sun, 26 Jun 2022 18:33:53 -0500 (CDT) Date: Sun, 26 Jun 2022 18:33:52 -0500 From: "Serge E. Hallyn" To: Casey Schaufler Cc: Micah Morton , linux-security-module@vger.kernel.org, keescook@chromium.org, jmorris@namei.org, serge@hallyn.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] security: Add LSM hook to setgroups() syscall Message-ID: <20220626233352.GA31265@mail.hallyn.com> References: <20220616171809.783277-1-mortonm@chromium.org> <034eb96c-573e-a074-2506-99456ec7f6f7@schaufler-ca.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <034eb96c-573e-a074-2506-99456ec7f6f7@schaufler-ca.com> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: On Mon, Jun 20, 2022 at 11:15:05AM -0700, Casey Schaufler wrote: > On 6/16/2022 10:18 AM, Micah Morton wrote: > > Give the LSM framework the ability to filter setgroups() syscalls. There > > are already analagous hooks for the set*uid() and set*gid() syscalls. > > The SafeSetID LSM will use this new hook to ensure setgroups() calls are > > allowed by the installed security policy. Tested by putting print > > statement in security_task_fix_setgroups() hook and confirming that it > > gets hit when userspace does a setgroups() syscall. > > > > Signed-off-by: Micah Morton > > I don't see any problems with this. > Acked-by: Casey Schaufler > Ditto. Thanks. Reviewed-by: Serge Hallyn > > --- > > include/linux/lsm_hook_defs.h | 1 + > > include/linux/lsm_hooks.h | 7 +++++++ > > include/linux/security.h | 7 +++++++ > > kernel/groups.c | 13 +++++++++++++ > > security/security.c | 5 +++++ > > 5 files changed, 33 insertions(+) > > > > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h > > index eafa1d2489fd..806448173033 100644 > > --- a/include/linux/lsm_hook_defs.h > > +++ b/include/linux/lsm_hook_defs.h > > @@ -201,6 +201,7 @@ LSM_HOOK(int, 0, task_fix_setuid, struct cred *new, const struct cred *old, > > int flags) > > LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old, > > int flags) > > +LSM_HOOK(int, 0, task_fix_setgroups, struct cred *new, const struct cred * old) > > LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid) > > LSM_HOOK(int, 0, task_getpgid, struct task_struct *p) > > LSM_HOOK(int, 0, task_getsid, struct task_struct *p) > > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > > index 91c8146649f5..84a0d7e02176 100644 > > --- a/include/linux/lsm_hooks.h > > +++ b/include/linux/lsm_hooks.h > > @@ -702,6 +702,13 @@ > > * @old is the set of credentials that are being replaced. > > * @flags contains one of the LSM_SETID_* values. > > * Return 0 on success. > > + * @task_fix_setgroups: > > + * Update the module's state after setting the supplementary group > > + * identity attributes of the current process. > > + * @new is the set of credentials that will be installed. Modifications > > + * should be made to this rather than to @current->cred. > > + * @old is the set of credentials that are being replaced. > > + * Return 0 on success. > > * @task_setpgid: > > * Check permission before setting the process group identifier of the > > * process @p to @pgid. > > diff --git a/include/linux/security.h b/include/linux/security.h > > index 7fc4e9f49f54..1dfd32c49fa3 100644 > > --- a/include/linux/security.h > > +++ b/include/linux/security.h > > @@ -415,6 +415,7 @@ int security_task_fix_setuid(struct cred *new, const struct cred *old, > > int flags); > > int security_task_fix_setgid(struct cred *new, const struct cred *old, > > int flags); > > +int security_task_fix_setgroups(struct cred *new, const struct cred *old); > > int security_task_setpgid(struct task_struct *p, pid_t pgid); > > int security_task_getpgid(struct task_struct *p); > > int security_task_getsid(struct task_struct *p); > > @@ -1098,6 +1099,12 @@ static inline int security_task_fix_setgid(struct cred *new, > > return 0; > > } > > +static inline int security_task_fix_setgroups(struct cred *new, > > + const struct cred *old) > > +{ > > + return 0; > > +} > > + > > static inline int security_task_setpgid(struct task_struct *p, pid_t pgid) > > { > > return 0; > > diff --git a/kernel/groups.c b/kernel/groups.c > > index 787b381c7c00..9aaed2a31073 100644 > > --- a/kernel/groups.c > > +++ b/kernel/groups.c > > @@ -134,13 +134,26 @@ EXPORT_SYMBOL(set_groups); > > int set_current_groups(struct group_info *group_info) > > { > > struct cred *new; > > + const struct cred *old; > > + int retval; > > new = prepare_creds(); > > if (!new) > > return -ENOMEM; > > + old = current_cred(); > > + > > set_groups(new, group_info); > > + > > + retval = security_task_fix_setgroups(new, old); > > + if (retval < 0) > > + goto error; > > + > > return commit_creds(new); > > + > > +error: > > + abort_creds(new); > > + return retval; > > } > > EXPORT_SYMBOL(set_current_groups); > > diff --git a/security/security.c b/security/security.c > > index 188b8f782220..15c686145ad6 100644 > > --- a/security/security.c > > +++ b/security/security.c > > @@ -1803,6 +1803,11 @@ int security_task_fix_setgid(struct cred *new, const struct cred *old, > > return call_int_hook(task_fix_setgid, 0, new, old, flags); > > } > > +int security_task_fix_setgroups(struct cred *new, const struct cred *old) > > +{ > > + return call_int_hook(task_fix_setgroups, 0, new, old); > > +} > > + > > int security_task_setpgid(struct task_struct *p, pid_t pgid) > > { > > return call_int_hook(task_setpgid, 0, p, pgid);