From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Johansen Subject: Re: [PATCH] Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve from granting privs Date: Fri, 13 Jan 2012 14:45:03 +0100 Message-ID: <4F10355F.5000805@canonical.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Will Drewry , torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, keescook@chromium.org, serge.hallyn@canonical.com, coreyb@linux.vnet.ibm.com, pmoore@redhat.com, eparis@redhat.com, djm@mindrot.org, segoon@openwall.com, rostedt@goodmis.org, jmorris@namei.org, scarybeasts@gmail.com, avi@redhat.com, penberg@cs.helsinki.fi, viro@zeniv.linux.org.uk, luto@MIT.EDU, mingo@elte.hu, akpm@linux-foundation.org, khilman@ti.com, borislav.petkov@amd.com, amwang@redhat.com, oleg@redhat.com, ak@linux.intel.com, eric.dumazet@gmail.com, gregkh@suse.de, dhowells@redhat.com, daniel.lezcano@free.fr, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, olofj@chromium.org, mhalcrow@google.com, dlaor@redhat.com, corbet@lwn.net, alan@lxorguk.ukuu.org.uk To: Andy Lutomirski Return-path: Received: from youngberry.canonical.com ([91.189.89.112]:34620 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752905Ab2AMNpR (ORCPT ); Fri, 13 Jan 2012 08:45:17 -0500 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 01/13/2012 03:12 AM, Andy Lutomirski wrote: > With this set, a lot of dangerous operations (chroot, unshare, etc) > become a lot less dangerous because there is no possibility of > subverting privileged binaries. > > This patch completely breaks apparmor. Someone who understands (and > uses) apparmor should fix it or at least give me a hint. > This should fix apparmor --- >>From b4d142f1a81d252ac2a72587841e7b430190a889 Mon Sep 17 00:00:00 2001 From: John Johansen Date: Fri, 13 Jan 2012 14:20:47 +0100 Subject: [PATCH] Fix apparmor for PR_{GET,SET}_NO_NEW_PRIV Signed-off-by: John Johansen --- security/apparmor/domain.c | 38 +++++++++++++++++++++++++++++++++++--- 1 files changed, 35 insertions(+), 3 deletions(-) diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c index 7f480b7..7316d77 100644 --- a/security/apparmor/domain.c +++ b/security/apparmor/domain.c @@ -360,9 +360,6 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm) if (bprm->cred_prepared) return 0; - /* XXX: someone who understands apparmor needs to fix this. */ - BUG_ON(bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS); - cxt = bprm->cred->security; BUG_ON(!cxt); @@ -398,6 +395,11 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm) new_profile = find_attach(ns, &ns->base.profiles, name); if (!new_profile) goto cleanup; + /* + * NOTE: Domain transitions from unconfined are allowed + * even when no_new_privs is set because this aways results + * in a further reduction of permissions. + */ goto apply; } @@ -458,6 +460,16 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm) /* fail exec */ error = -EACCES; + /* + * Policy has specified a domain transition, if no_new_privs then + * fail the exec. + */ + if (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) { + aa_put_profile(new_profile); + error = -EPERM; + goto cleanup; + } + if (!new_profile) goto audit; @@ -612,6 +624,14 @@ int aa_change_hat(const char *hats[], int count, u64 token, bool permtest) const char *target = NULL, *info = NULL; int error = 0; + /* + * Fail explicitly requested domain transitions if no_new_privs. + * There is no exception for unconfined as change_hat is not + * available. + */ + if (current->no_new_privs) + return -EPERM; + /* released below */ cred = get_current_cred(); cxt = cred->security; @@ -753,6 +773,18 @@ int aa_change_profile(const char *ns_name, const char *hname, bool onexec, cxt = cred->security; profile = aa_cred_profile(cred); + /* + * Fail explicitly requested domain transitions if no_new_privs + * and not unconfined. + * Domain transitions from unconfined are allowed even when + * no_new_privs is set because this aways results in a reduction + * of permissions. + */ + if (current->no_new_privs && !unconfined(profile)) { + put_cred(cred); + return -EPERM; + } + if (ns_name) { /* released below */ ns = aa_find_namespace(profile->ns, ns_name); -- 1.7.7.3