From patchwork Wed Jun 24 21:57:14 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?q?Andreas_Gr=C3=BCnbacher?= X-Patchwork-Id: 6670521 Return-Path: X-Original-To: patchwork-linux-nfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 556769F39B for ; Wed, 24 Jun 2015 22:01:55 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 3CDCD20569 for ; Wed, 24 Jun 2015 22:01:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 076F420547 for ; Wed, 24 Jun 2015 22:01:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751415AbbFXV6g (ORCPT ); Wed, 24 Jun 2015 17:58:36 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:36058 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752488AbbFXV6J (ORCPT ); Wed, 24 Jun 2015 17:58:09 -0400 Received: by wicnd19 with SMTP id nd19so147385935wic.1; Wed, 24 Jun 2015 14:58:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=jPmRMDW3uYVSxhtSd+saQOyqonYjUgklC2GIsnWWkbk=; b=EG8npL8JP4+HVF9phloRBD1bCETiErdAaeVtD4W1zg46YWeE3UtJtV/SowVvLcIhd3 qEkh1ZiKGPzW3ULixmmwrkEV0zSJHxE/he8YVKtbxLeWiVtoPzhO4yaesrB4KiDni9L2 vatsK5i+gSBM5JLF4cc+qaDWWMTA8PdUxcITS4OPFf11R18INTyZCsJax2eU4Q2NAxWj GUm6MOr7x+T4bmNss20DR/c3YJyIy76mODSpzN1APD4TTjWXDy/jWbS1yvI6JE50ec/k aBHsRnRR2pTb4Pjz7iwAqbIbnsTpUrdEwl/XTSEH1/TO8gJUmbZSQdNM9gCuyNe7hRMn 3tUg== X-Received: by 10.180.103.194 with SMTP id fy2mr8818705wib.55.1435183087268; Wed, 24 Jun 2015 14:58:07 -0700 (PDT) Received: from nuc.home.com (80-110-112-232.cgn.dynamic.surfer.at. [80.110.112.232]) by mx.google.com with ESMTPSA id lu5sm42559880wjb.9.2015.06.24.14.58.06 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Jun 2015 14:58:06 -0700 (PDT) From: Andreas Gruenbacher X-Google-Original-From: Andreas Gruenbacher To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-api@vger.kernel.org, samba-technical@lists.samba.org, linux-security-module@vger.kernel.org Cc: Andreas Gruenbacher Subject: [RFC v4 25/31] richacl: Isolate the owner and group classes Date: Wed, 24 Jun 2015 23:57:14 +0200 Message-Id: <1435183040-22726-26-git-send-email-agruenba@redhat.com> X-Mailer: git-send-email 2.4.2 In-Reply-To: <1435183040-22726-1-git-send-email-agruenba@redhat.com> References: <1435183040-22726-1-git-send-email-agruenba@redhat.com> Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Spam-Status: No, score=-8.2 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, T_DKIM_INVALID, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When applying the file masks to an acl, we need to ensure that no process gets more permissions than allowed by its file mask. This may require inserting an owner@ deny ace to ensure this if the owner mask contains fewer permissions than the group or other mask. For example, when applying mode 0466 to the following acl: everyone@:rw::allow A deny ace needs to be inserted so that the owner won't get elevated write access: owner@:w::deny everyone@:rw::allow Likewise, we may need to insert group class deny aces if the group mask contains fewer permissions than the other mask. For example, when applying mode 0646 to the following acl: owner@:rw::allow everyone@:rw::allow A deny ace needs to be inserted so that the owning group won't get elevated write access: owner@:rw::allow group@:w::deny everyone@:rw::allow Signed-off-by: Andreas Gruenbacher --- fs/richacl_compat.c | 228 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 228 insertions(+) diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c index b699cd3..ae10fa6 100644 --- a/fs/richacl_compat.c +++ b/fs/richacl_compat.c @@ -480,3 +480,231 @@ richacl_set_other_permissions(struct richacl_alloc *alloc) richace_change_mask(alloc, &ace, other_mask); return 0; } + +/** + * richacl_max_allowed - maximum permissions that anybody is allowed + */ +static unsigned int +richacl_max_allowed(struct richacl *acl) +{ + struct richace *ace; + unsigned int allowed = 0; + + richacl_for_each_entry_reverse(ace, acl) { + if (richace_is_inherit_only(ace)) + continue; + if (richace_is_allow(ace)) + allowed |= ace->e_mask; + else if (richace_is_deny(ace)) { + if (richace_is_everyone(ace)) + allowed &= ~ace->e_mask; + } + } + return allowed; +} + +/** + * richacl_isolate_owner_class - limit the owner class to the owner file mask + * @alloc: acl and number of allocated entries + * + * POSIX requires that after a chmod, the owner class is granted no more + * permissions than the owner file permission bits. For richacls, this + * means that the owner class must not be granted any permissions that the + * owner mask does not include. + * + * When we apply file masks to an acl which grant more permissions to the group + * or other class than to the owner class, we may end up in a situation where + * the owner is granted additional permissions from other aces. For example, + * given this acl: + * + * everyone:rwx::allow + * + * when file masks corresponding to mode 0466 are applied, after + * richacl_propagate_everyone() and __richacl_apply_masks(), we end up with: + * + * owner@:r::allow + * everyone@:rw::allow + * + * This acl still grants the owner rw access through the everyone@ allow ace. + * To fix this, we must deny the owner w access: + * + * owner@:w::deny + * owner@:r::allow + * everyone@:rw::allow + */ +static int +richacl_isolate_owner_class(struct richacl_alloc *alloc) +{ + struct richace *ace; + unsigned int allowed = 0; + + allowed = richacl_max_allowed(alloc->acl); + if (allowed & ~alloc->acl->a_owner_mask) { + /* + * Figure out if we can update an existig OWNER@ DENY entry. + */ + richacl_for_each_entry(ace, alloc->acl) { + if (richace_is_inherit_only(ace)) + continue; + if (richace_is_deny(ace)) { + if (richace_is_owner(ace)) + break; + } else if (richace_is_allow(ace)) { + ace = alloc->acl->a_entries + alloc->acl->a_count; + break; + } + } + if (ace != alloc->acl->a_entries + alloc->acl->a_count) { + if (richace_change_mask(alloc, &ace, ace->e_mask | + (allowed & ~alloc->acl->a_owner_mask))) + return -1; + } else { + /* Insert an owner@ deny entry at the front. */ + ace = alloc->acl->a_entries; + if (richacl_insert_entry(alloc, &ace)) + return -1; + ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE; + ace->e_flags = RICHACE_SPECIAL_WHO; + ace->e_mask = allowed & ~alloc->acl->a_owner_mask; + ace->e_id.special = RICHACE_OWNER_SPECIAL_ID; + } + } + return 0; +} + +/** + * __richacl_isolate_who - isolate entry from everyone@ allow entry + * @alloc: acl and number of allocated entries + * @who: identifier to isolate + * @deny: permissions this identifier should not be allowed + * + * See richacl_isolate_group_class(). + */ +static int +__richacl_isolate_who(struct richacl_alloc *alloc, struct richace *who, + unsigned int deny) +{ + struct richace *ace; + unsigned int n; + /* + * Compute the permissions already denied to @who. + */ + richacl_for_each_entry(ace, alloc->acl) { + if (richace_is_inherit_only(ace)) + continue; + if (richace_is_same_identifier(ace, who) && + richace_is_deny(ace)) + deny &= ~ace->e_mask; + } + if (!deny) + return 0; + + /* + * Figure out if we can update an existig deny entry. Start from the + * entry before the trailing everyone@ allow entry. We will not hit + * everyone@ entries in the loop. + */ + for (n = alloc->acl->a_count - 2; n != -1; n--) { + ace = alloc->acl->a_entries + n; + if (richace_is_inherit_only(ace)) + continue; + if (richace_is_deny(ace)) { + if (richace_is_same_identifier(ace, who)) + break; + } else if (richace_is_allow(ace) && + (ace->e_mask & deny)) { + n = -1; + break; + } + } + if (n != -1) { + if (richace_change_mask(alloc, &ace, ace->e_mask | deny)) + return -1; + } else { + /* + * Insert a new entry before the trailing everyone@ deny entry. + */ + struct richace who_copy; + + ace = alloc->acl->a_entries + alloc->acl->a_count - 1; + memcpy(&who_copy, who, sizeof(struct richace)); + if (richacl_insert_entry(alloc, &ace)) + return -1; + memcpy(ace, &who_copy, sizeof(struct richace)); + ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE; + richace_clear_inheritance_flags(ace); + ace->e_mask = deny; + } + return 0; +} + +/** + * richacl_isolate_group_class - limit the group class to the group file mask + * @alloc: acl and number of allocated entries + * + * POSIX requires that after a chmod, the group class is granted no more + * permissions than the group file permission bits. For richacls, this + * means that the group class must not be granted any permissions that the + * group mask does not include. + * + * When we apply file masks to an acl which grant more permissions to the other + * class than to the group class, we may end up in a situation where processes + * in the group class are granted additional permission from other aces. For + * example, given this acl: + * + * joe:rwx::allow + * everyone:rwx::allow + * + * when file masks corresponding to mode 0646 are applied, after + * richacl_propagate_everyone() and __richacl_apply_masks(), we end up with: + * + * joe:r::allow + * owner@:rw::allow + * group@:r::allow + * everyone@:rw::allow + * + * This acl still grants joe and group@ rw access through the everyone@ allow + * ace. To fix this, we must deny w access to group class aces before the + * everyone@ allow ace at the end of the acl: + * + * joe:r::allow + * owner@:rw::allow + * group@:r::allow + * joe:w::deny + * group@:w::deny + * everyone@:rw::allow + */ +static int +richacl_isolate_group_class(struct richacl_alloc *alloc) +{ + struct richace who = { + .e_flags = RICHACE_SPECIAL_WHO, + .e_id.special = RICHACE_GROUP_SPECIAL_ID, + }; + unsigned int deny; + + deny = alloc->acl->a_other_mask & ~alloc->acl->a_group_mask; + + if (deny) { + unsigned int n; + + if (__richacl_isolate_who(alloc, &who, deny)) + return -1; + /* + * Start from the entry before the trailing everyone@ allow + * entry. We will not hit everyone@ entries in the loop. + */ + for (n = alloc->acl->a_count - 1; n != -1; n--) { + struct richace *ace = alloc->acl->a_entries + n; + + if (richace_is_inherit_only(ace) || + richace_is_owner(ace) || + richace_is_group(ace) || + richace_is_everyone(ace)) + continue; + if (__richacl_isolate_who(alloc, ace, deny)) + return -1; + } + } + return 0; +}