From patchwork Wed Aug 23 10:12:52 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Richard Guy Briggs X-Patchwork-Id: 9917025 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 6CFF360327 for ; Wed, 23 Aug 2017 10:13:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5F685288B6 for ; Wed, 23 Aug 2017 10:13:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 542742893F; Wed, 23 Aug 2017 10:13:40 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BF05B288B6 for ; Wed, 23 Aug 2017 10:13:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753847AbdHWKNj (ORCPT ); Wed, 23 Aug 2017 06:13:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33764 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753844AbdHWKNi (ORCPT ); Wed, 23 Aug 2017 06:13:38 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 774877EA94; Wed, 23 Aug 2017 10:13:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 774877EA94 Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=rgb@redhat.com Received: from madcap2.tricolour.ca (ovpn-112-7.rdu2.redhat.com [10.10.112.7]) by smtp.corp.redhat.com (Postfix) with ESMTP id C2B7C63750; Wed, 23 Aug 2017 10:13:35 +0000 (UTC) From: Richard Guy Briggs To: linux-security-module@vger.kernel.org, linux-audit@redhat.com Cc: Richard Guy Briggs , Andy Lutomirski , "Serge E. Hallyn" , Kees Cook , James Morris , Eric Paris , Paul Moore , Steve Grubb Subject: [PATCH V3 01/10] capabilities: factor out cap_bprm_set_creds privileged root Date: Wed, 23 Aug 2017 06:12:52 -0400 Message-Id: <63333a7ed7e3ce62e3142b5e34ee942f3874a0d6.1503459890.git.rgb@redhat.com> In-Reply-To: References: In-Reply-To: References: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 23 Aug 2017 10:13:38 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Factor out the case of privileged root from the function cap_bprm_set_creds() to make the latter easier to read and analyse. Suggested-by: Serge Hallyn Signed-off-by: Richard Guy Briggs Reviewed-by: Serge Hallyn --- security/commoncap.c | 62 +++++++++++++++++++++++++++---------------------- 1 files changed, 34 insertions(+), 28 deletions(-) diff --git a/security/commoncap.c b/security/commoncap.c index 78b3783..b7fbf77 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -481,6 +481,38 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_c return rc; } +void handle_privileged_root(struct linux_binprm *bprm, bool has_cap, bool *effective, kuid_t root_uid) +{ + const struct cred *old = current_cred(); + struct cred *new = bprm->cred; + + if (issecure(SECURE_NOROOT)) + return; + /* + * If the legacy file capability is set, then don't set privs + * for a setuid root binary run by a non-root user. Do set it + * for a root user just to cause least surprise to an admin. + */ + if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { + warn_setuid_and_fcaps_mixed(bprm->filename); + return; + } + /* + * To support inheritance of root-permissions and suid-root + * executables under compatibility mode, we override the + * capability sets for the file. + * + * If only the real uid is 0, we do not set the effective bit. + */ + if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { + /* pP' = (cap_bset & ~0) | (pI & ~0) */ + new->cap_permitted = cap_combine(old->cap_bset, + old->cap_inheritable); + } + if (uid_eq(new->euid, root_uid)) + *effective = true; +} + /** * cap_bprm_set_creds - Set up the proposed credentials for execve(). * @bprm: The execution parameters, including the proposed creds @@ -493,46 +525,20 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) { const struct cred *old = current_cred(); struct cred *new = bprm->cred; - bool effective, has_cap = false, is_setid; + bool effective = false, has_cap = false, is_setid; int ret; kuid_t root_uid; if (WARN_ON(!cap_ambient_invariant_ok(old))) return -EPERM; - effective = false; ret = get_file_caps(bprm, &effective, &has_cap); if (ret < 0) return ret; root_uid = make_kuid(new->user_ns, 0); - if (!issecure(SECURE_NOROOT)) { - /* - * If the legacy file capability is set, then don't set privs - * for a setuid root binary run by a non-root user. Do set it - * for a root user just to cause least surprise to an admin. - */ - if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { - warn_setuid_and_fcaps_mixed(bprm->filename); - goto skip; - } - /* - * To support inheritance of root-permissions and suid-root - * executables under compatibility mode, we override the - * capability sets for the file. - * - * If only the real uid is 0, we do not set the effective bit. - */ - if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { - /* pP' = (cap_bset & ~0) | (pI & ~0) */ - new->cap_permitted = cap_combine(old->cap_bset, - old->cap_inheritable); - } - if (uid_eq(new->euid, root_uid)) - effective = true; - } -skip: + handle_privileged_root(bprm, has_cap, &effective, root_uid); /* if we have fs caps, clear dangerous personality flags */ if (!cap_issubset(new->cap_permitted, old->cap_permitted))