From patchwork Wed Jul 22 13:03:12 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: 6843271 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id B6352C05AC for ; Wed, 22 Jul 2015 13:14:02 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id A0670206CE for ; Wed, 22 Jul 2015 13:14:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C04D204F6 for ; Wed, 22 Jul 2015 13:14:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934317AbbGVNNr (ORCPT ); Wed, 22 Jul 2015 09:13:47 -0400 Received: from mail-wi0-f172.google.com ([209.85.212.172]:36809 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756846AbbGVNEc (ORCPT ); Wed, 22 Jul 2015 09:04:32 -0400 Received: by wicgb10 with SMTP id gb10so97400904wic.1; Wed, 22 Jul 2015 06:04:30 -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=Ep44Vyl26v53V+EEQGsmpgTuiAc31ERLNYU0tEwCwzE=; b=BJ2GR0qjjFnPBlZCuZHGKM0CvUIM7rTC77zgx40ygIGh2P/X4oocibHvsS4eXM3o3v 6TiTk+6yJ1GxPk1qcetisuGD4A+x+MZxuYbXMy4knZJVPve4dzc+PaDHi3FRKd//v+Rf blh3NDhSbO6pglMWAOpyw/E3gV2XHgSDTYF7T8zF9Htps/CMeFIRUESv5pUoiDs1pFyv LtGmkUueEXZIWKbDUTkezHoIixAgakm5ZIWO9zXlLMMjhHb8LBpZRdo5n1h02P5737uL UOfo3+0fM8MUBWOw3kvtU0bH3LjL56T5Qb5kUZxKkGi9gdlz70HzMaJFAOdAOwZFWraf 516g== X-Received: by 10.180.188.139 with SMTP id ga11mr6153120wic.87.1437570270500; Wed, 22 Jul 2015 06:04:30 -0700 (PDT) Received: from schleppi.home.com ([149.14.88.26]) by smtp.gmail.com with ESMTPSA id u7sm21992628wif.3.2015.07.22.06.04.29 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Jul 2015 06:04:30 -0700 (PDT) From: Andreas Gruenbacher To: linux-kernel@vger.kernel.org Cc: 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, Andreas Gruenbacher , Andreas Gruenbacher Subject: [PATCH v5 22/39] richacl: Propagate everyone@ permissions to other aces Date: Wed, 22 Jul 2015 15:03:12 +0200 Message-Id: <1437570209-29832-23-git-send-email-andreas.gruenbacher@gmail.com> X-Mailer: git-send-email 2.4.3 In-Reply-To: <1437570209-29832-1-git-send-email-andreas.gruenbacher@gmail.com> References: <1437570209-29832-1-git-send-email-andreas.gruenbacher@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-8.0 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 From: Andreas Gruenbacher The trailing everyone@ allow ace can grant permissions to all file classes including the owner and group class. Before we can apply the other mask to this entry to turn it into an "other class" entry, we need to ensure that members of the owner or group class will not lose any permissions from that ace. Conceptually, we do this by inserting additional :::allow entries before the trailing everyone@ allow ace with the same permissions as the trailing everyone@ allow ace for owner@, group@, and all explicitly mentioned users and groups. (In practice, we will rarely need to insert any additional aces in this step.) Signed-off-by: Andreas Gruenbacher --- fs/richacl_compat.c | 182 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 182 insertions(+) diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c index e10ead3..b709cde 100644 --- a/fs/richacl_compat.c +++ b/fs/richacl_compat.c @@ -217,3 +217,185 @@ richacl_move_everyone_aces_down(struct richacl_alloc *alloc) } return 0; } + +/** + * __richacl_propagate_everyone - propagate everyone@ permissions up for @who + * @alloc: acl and number of allocated entries + * @who: identifier to propagate permissions for + * @allow: permissions to propagate up + * + * Propagate the permissions in @allow up from the end of the acl to the start + * for the specified principal @who. + * + * The simplest possible approach to achieve this would be to insert a + * ":::allow" ace before the final everyone@ allow ace. Since this + * would often result in aces which are not needed or which could be merged + * with an existing ace, we make the following optimizations: + * + * - We go through the acl and determine which permissions are already + * allowed or denied to @who, and we remove those permissions from + * @allow. + * + * - If the acl contains an allow ace for @who and no aces after this entry + * deny permissions in @allow, we add the permissions in @allow to this + * ace. (Propagating permissions across a deny ace which can match the + * process can elevate permissions.) + * + * This transformation does not alter the permissions that the acl grants. + */ +static int +__richacl_propagate_everyone(struct richacl_alloc *alloc, struct richace *who, + unsigned int allow) +{ + struct richace *allow_last = NULL, *ace; + struct richacl *acl = alloc->acl; + + /* + * Remove the permissions from allow that are already determined for + * this who value, and figure out if there is an allow entry for + * this who value that is "reachable" from the trailing everyone@ + * allow ace. + */ + richacl_for_each_entry(ace, acl) { + if (richace_is_inherit_only(ace)) + continue; + if (richace_is_allow(ace)) { + if (richace_is_same_identifier(ace, who)) { + allow &= ~ace->e_mask; + allow_last = ace; + } + } else if (richace_is_deny(ace)) { + if (richace_is_same_identifier(ace, who)) + allow &= ~ace->e_mask; + else if (allow & ace->e_mask) + allow_last = NULL; + } + } + ace--; + + /* + * If for group class entries, all the remaining permissions will + * remain granted by the trailing everyone@ ace, no additional entry is + * needed. + */ + if (!richace_is_owner(who) && + richace_is_everyone(ace) && richace_is_allow(ace) && + !(allow & ~(ace->e_mask & acl->a_other_mask))) + allow = 0; + + if (allow) { + if (allow_last) + return richace_change_mask(alloc, &allow_last, + allow_last->e_mask | allow); + else { + struct richace who_copy; + + richace_copy(&who_copy, who); + ace = acl->a_entries + acl->a_count - 1; + if (richacl_insert_entry(alloc, &ace)) + return -1; + richace_copy(ace, &who_copy); + ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE; + richace_clear_inheritance_flags(ace); + ace->e_mask = allow; + } + } + return 0; +} + +/** + * richacl_propagate_everyone - propagate everyone@ permissions up the acl + * @alloc: acl and number of allocated entries + * + * Make sure that group@ and all other users and groups mentioned in the acl + * will not lose any permissions when finally applying the other mask to the + * everyone@ allow ace at the end of the acl. We modify the permissions of + * existing entries or add new entries before the final everyone@ allow ace to + * achieve that. + * + * Entries for owner@ are ignored here; see richacl_set_owner_permissions(). + * + * For example, the following acl implicitly grants everyone rwpx access: + * + * joe:r::allow + * everyone@:rwpx::allow + * + * When applying mode 0660 to this acl, group@ would lose rwp access, and joe + * would lose wp access even though the mode does not exclude those + * permissions. After propagating the everyone@ permissions, the result for + * applying mode 0660 becomes: + * + * owner@:rwp::allow + * joe:rwp::allow + * group@:rwp::allow + * + * Deny aces complicate the matter. For example, the following acl grants + * everyone but joe write access: + * + * joe:wp::deny + * everyone@:rwpx::allow + * + * When applying mode 0660 to this acl, group@ would lose rwp access, and joe + * would lose r access. After propagating the everyone@ permissions, the + * result for applying mode 0660 becomes: + * + * owner@:rwp::allow + * joe:w::deny + * group@:rwp::allow + * joe:r::allow + */ +static int +richacl_propagate_everyone(struct richacl_alloc *alloc) +{ + struct richace who = { .e_flags = RICHACE_SPECIAL_WHO }; + struct richacl *acl = alloc->acl; + struct richace *ace; + unsigned int group_allow; + + /* + * If the group mask contains permissions which are not in the other + * mask, we may need to propagate permissions up from the everyone@ + * allow ace. + */ + if (!(acl->a_group_mask & ~acl->a_other_mask)) + return 0; + if (!acl->a_count) + return 0; + ace = acl->a_entries + acl->a_count - 1; + if (richace_is_inherit_only(ace) || !richace_is_everyone(ace)) + return 0; + + group_allow = ace->e_mask & acl->a_group_mask; + if (group_allow & ~acl->a_other_mask) { + int n; + + /* Propagate everyone@ permissions through to group@. */ + who.e_id.special = RICHACE_GROUP_SPECIAL_ID; + if (__richacl_propagate_everyone(alloc, &who, group_allow)) + return -1; + acl = alloc->acl; + + /* + * Start from the entry before the trailing everyone@ allow + * entry. We will not hit everyone@ entries in the loop. + */ + for (n = acl->a_count - 2; n != -1; n--) { + ace = acl->a_entries + n; + + if (richace_is_inherit_only(ace) || + richace_is_owner(ace) || + richace_is_group(ace)) + continue; + if (richace_is_allow(ace) || richace_is_deny(ace)) { + /* + * Any inserted entry will end up below the + * current entry + */ + if (__richacl_propagate_everyone(alloc, ace, + group_allow)) + return -1; + } + } + } + return 0; +}