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 X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5CE62C43381 for ; Sat, 16 Feb 2019 16:43:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 23E21222D0 for ; Sat, 16 Feb 2019 16:43:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730352AbfBPQnh (ORCPT ); Sat, 16 Feb 2019 11:43:37 -0500 Received: from mail.hallyn.com ([178.63.66.53]:38688 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726689AbfBPQnh (ORCPT ); Sat, 16 Feb 2019 11:43:37 -0500 Received: by mail.hallyn.com (Postfix, from userid 1001) id 9C023168; Sat, 16 Feb 2019 10:43:33 -0600 (CST) Date: Sat, 16 Feb 2019 10:43:33 -0600 From: "Serge E. Hallyn" To: mortonm@chromium.org Cc: jmorris@namei.org, serge@hallyn.com, keescook@chromium.org, casey@schaufler-ca.com, sds@tycho.nsa.gov, linux-security-module@vger.kernel.org Subject: Re: [PATCH 1/2] LSM: SafeSetID: gate setgid transitions Message-ID: <20190216164333.GA10883@mail.hallyn.com> References: <20190215222217.133213-1-mortonm@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190215222217.133213-1-mortonm@chromium.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri, Feb 15, 2019 at 02:22:17PM -0800, mortonm@chromium.org wrote: > From: Micah Morton > > This patch adds a 'task_fix_setgid' LSM hook, which is analogous to the > existing 'task_fix_setuid' LSM hook, and calls this new hook from the > setgid functions in kernel/sys.c. This will allow the SafeSetID LSM to > govern setgid transitions in addition to setuid transitions. This change > also makes sure the setgid functions in kernel/sys.c call > security_capable_setid rather than the ordinary security_capable Sorry, where security_capable_setid this defined? I assume it was in a recent patchset, but google and grep are failing me. > function, so that the security_capable hook in the SafeSetID LSM knows > it is being invoked from a setid function. > > Signed-off-by: Micah Morton > --- > Tested with slight mod to test in tools/testing/selftests/safesetid for > testing setgid as well as setuid. > > include/linux/lsm_hooks.h | 12 ++++++++++++ > include/linux/security.h | 10 ++++++++++ > kernel/sys.c | 27 +++++++++++++++++++++------ > security/security.c | 6 ++++++ > 4 files changed, 49 insertions(+), 6 deletions(-) > > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > index 22fc786d723a..f252ed3e95ef 100644 > --- a/include/linux/lsm_hooks.h > +++ b/include/linux/lsm_hooks.h > @@ -603,6 +603,15 @@ > * @old is the set of credentials that are being replaces > * @flags contains one of the LSM_SETID_* values. > * Return 0 on success. > + * @task_fix_setgid: > + * Update the module's state after setting one or more of the group > + * identity attributes of the current process. The @flags parameter > + * indicates which of the set*gid system calls invoked this hook. > + * @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 > + * @flags contains one of the LSM_SETID_* values. > + * Return 0 on success. > * @task_setpgid: > * Check permission before setting the process group identifier of the > * process @p to @pgid. > @@ -1596,6 +1605,8 @@ union security_list_options { > enum kernel_read_file_id id); > int (*task_fix_setuid)(struct cred *new, const struct cred *old, > int flags); > + int (*task_fix_setgid)(struct cred *new, const struct cred *old, > + int flags); > int (*task_setpgid)(struct task_struct *p, pid_t pgid); > int (*task_getpgid)(struct task_struct *p); > int (*task_getsid)(struct task_struct *p); > @@ -1887,6 +1898,7 @@ struct security_hook_heads { > struct hlist_head kernel_post_read_file; > struct hlist_head kernel_module_request; > struct hlist_head task_fix_setuid; > + struct hlist_head task_fix_setgid; > struct hlist_head task_setpgid; > struct hlist_head task_getpgid; > struct hlist_head task_getsid; > diff --git a/include/linux/security.h b/include/linux/security.h > index 13537a49ae97..f3d095e8dfc1 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -96,6 +96,7 @@ extern int cap_mmap_addr(unsigned long addr); > extern int cap_mmap_file(struct file *file, unsigned long reqprot, > unsigned long prot, unsigned long flags); > extern int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags); > +extern int cap_task_fix_setgid(struct cred *new, const struct cred *old, int flags); > extern int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, > unsigned long arg4, unsigned long arg5); > extern int cap_task_setscheduler(struct task_struct *p); > @@ -326,6 +327,8 @@ int security_kernel_post_read_file(struct file *file, char *buf, loff_t size, > enum kernel_read_file_id id); > 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_setpgid(struct task_struct *p, pid_t pgid); > int security_task_getpgid(struct task_struct *p); > int security_task_getsid(struct task_struct *p); > @@ -930,6 +933,13 @@ static inline int security_task_fix_setuid(struct cred *new, > return cap_task_fix_setuid(new, old, flags); > } > > +static inline int security_task_fix_setgid(struct cred *new, > + const struct cred *old, > + int flags) > +{ > + return cap_task_fix_setgid(new, old, flags); > +} > + > static inline int security_task_setpgid(struct task_struct *p, pid_t pgid) > { > return 0; > diff --git a/kernel/sys.c b/kernel/sys.c > index c5f875048aef..76f1c46ac66f 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -372,7 +372,7 @@ long __sys_setregid(gid_t rgid, gid_t egid) > if (rgid != (gid_t) -1) { > if (gid_eq(old->gid, krgid) || > gid_eq(old->egid, krgid) || > - ns_capable(old->user_ns, CAP_SETGID)) > + ns_capable_setid(old->user_ns, CAP_SETGID)) > new->gid = krgid; > else > goto error; > @@ -381,7 +381,7 @@ long __sys_setregid(gid_t rgid, gid_t egid) > if (gid_eq(old->gid, kegid) || > gid_eq(old->egid, kegid) || > gid_eq(old->sgid, kegid) || > - ns_capable(old->user_ns, CAP_SETGID)) > + ns_capable_setid(old->user_ns, CAP_SETGID)) > new->egid = kegid; > else > goto error; > @@ -392,6 +392,10 @@ long __sys_setregid(gid_t rgid, gid_t egid) > new->sgid = new->egid; > new->fsgid = new->egid; > > + retval = security_task_fix_setgid(new, old, LSM_SETID_RE); > + if (retval < 0) > + goto error; > + > return commit_creds(new); > > error: > @@ -427,13 +431,17 @@ long __sys_setgid(gid_t gid) > old = current_cred(); > > retval = -EPERM; > - if (ns_capable(old->user_ns, CAP_SETGID)) > + if (ns_capable_setid(old->user_ns, CAP_SETGID)) > new->gid = new->egid = new->sgid = new->fsgid = kgid; > else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid)) > new->egid = new->fsgid = kgid; > else > goto error; > > + retval = security_task_fix_setgid(new, old, LSM_SETID_ID); > + if (retval < 0) > + goto error; > + > return commit_creds(new); > > error: > @@ -735,7 +743,7 @@ long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid) > old = current_cred(); > > retval = -EPERM; > - if (!ns_capable(old->user_ns, CAP_SETGID)) { > + if (!ns_capable_setid(old->user_ns, CAP_SETGID)) { > if (rgid != (gid_t) -1 && !gid_eq(krgid, old->gid) && > !gid_eq(krgid, old->egid) && !gid_eq(krgid, old->sgid)) > goto error; > @@ -755,6 +763,10 @@ long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid) > new->sgid = ksgid; > new->fsgid = new->egid; > > + retval = security_task_fix_setgid(new, old, LSM_SETID_RES); > + if (retval < 0) > + goto error; > + > return commit_creds(new); > > error: > @@ -858,10 +870,13 @@ long __sys_setfsgid(gid_t gid) > > if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->egid) || > gid_eq(kgid, old->sgid) || gid_eq(kgid, old->fsgid) || > - ns_capable(old->user_ns, CAP_SETGID)) { > + ns_capable_setid(old->user_ns, CAP_SETGID)) { > if (!gid_eq(kgid, old->fsgid)) { > new->fsgid = kgid; > - goto change_okay; > + if (security_task_fix_setgid(new, > + old, > + LSM_SETID_FS) == 0) > + goto change_okay; > } > } > > diff --git a/security/security.c b/security/security.c > index b6bff646d373..4264a1e77ce8 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -1570,6 +1570,12 @@ int security_task_fix_setuid(struct cred *new, const struct cred *old, > return call_int_hook(task_fix_setuid, 0, new, old, flags); > } > > +int security_task_fix_setgid(struct cred *new, const struct cred *old, > + int flags) > +{ > + return call_int_hook(task_fix_setgid, 0, new, old, flags); > +} > + > int security_task_setpgid(struct task_struct *p, pid_t pgid) > { > return call_int_hook(task_setpgid, 0, p, pgid); > -- > 2.21.0.rc0.258.g878e2cd30e-goog