From patchwork Tue Jul 21 20:02:30 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dominick Grift X-Patchwork-Id: 11676567 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4F3471510 for ; Tue, 21 Jul 2020 20:02:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 352F72073A for ; Tue, 21 Jul 2020 20:02:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=defensec.nl header.i=@defensec.nl header.b="o9dDaCgS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726646AbgGUUCm (ORCPT ); Tue, 21 Jul 2020 16:02:42 -0400 Received: from agnus.defensec.nl ([80.100.19.56]:56064 "EHLO agnus.defensec.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726029AbgGUUCm (ORCPT ); Tue, 21 Jul 2020 16:02:42 -0400 Received: from localhost.localdomain (brutus [IPv6:2001:985:d55d::438]) by agnus.defensec.nl (Postfix) with ESMTPSA id A50812A06FB; Tue, 21 Jul 2020 22:02:40 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 agnus.defensec.nl A50812A06FB DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=defensec.nl; s=default; t=1595361760; bh=aPQljGd9QBnBgxv2U9+3HV96V4IevQKcuPaftay8lcI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=o9dDaCgShlpcen6NkSrFwB0pAGJ6WP2OIqKTqYuTvIOe9c4Nqco/2OuWshlLJ0Jnw IpfYHPAE2Ng71Sb5/9PIY5GiqrO+RH2rTJRYNedJ67ZxOoXDKW4oh4+mzFQeRtXA5g cTLthJ2ihUZZqxX7/pL9m5DczvhMH90rgBaFMrv8= From: Dominick Grift To: selinux@vger.kernel.org Cc: Dominick Grift Subject: [SELinux-notebook PATCH v8] objects.md: some clarifications Date: Tue, 21 Jul 2020 22:02:30 +0200 Message-Id: <20200721200230.1976501-1-dominick.grift@defensec.nl> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200721195153.1974509-1-dominick.grift@defensec.nl> References: <20200721195153.1974509-1-dominick.grift@defensec.nl> MIME-Version: 1.0 Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org Elaborate on labeling. Touch on the significance of the default statement, on various av permissions related to labeling using the libselinux API, and on how the kernel and unlabeled initial security identifiers are used to address labeling challenges in special cases such as initialization and failover respectively. Signed-off-by: Dominick Grift --- v2: fixes patch description v3: adding patch description, s/policies/policy's/, split unlabeled and kernel descriptions for clarity v4: fixes another typo in description and emphasize system initialization a bit v5: emphasize kernel threads with kernel isid description v6: forgot to mention defaultuser, can only associate one label with isids v7: copied and pasted feedback from Stephen Smalley v8: missed a s/access vectors/permissions/ instance src/objects.md | 47 +++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 43 insertions(+), 4 deletions(-) diff --git a/src/objects.md b/src/objects.md index 58664ef..1907316 100644 --- a/src/objects.md +++ b/src/objects.md @@ -110,14 +110,20 @@ objects is managed by the system and generally unseen by the users (until labeling goes wrong !!). As processes and objects are created and destroyed, they either: -1. Inherit their labels from the parent process or object. +1. Inherit their labels from the parent process or object. The policy + default user, type, role and range statements can be used to + change the behavior as discussed in the [**Default Rules**](default_rules.md#default-object-rules) + section. 2. The policy type, role and range transition statements allow a different label to be assigned as discussed in the [**Domain and Object Transitions**](domain_object_transitions.md#domain-and-object-transitions) section. -3. SELinux-aware applications can enforce a new label (with the - policies approval of course) using the **libselinux** API - functions. +3. SELinux-aware applications can assign a new label (with the + policy's approval of course) using the **libselinux** API + functions. The `process setfscreate` permission can be used to + allow subjects to create files with a new label programmatically + using the ***setfscreatecon**(3)* function, overriding default + rules and transition statements. 4. An object manager (OM) can enforce a default label that can either be built into the OM or obtained via a configuration file (such as those used by @@ -269,6 +275,39 @@ and manage their transition: `type_transition`, `role_transition` and `range_transition` +SELinux-aware applications can assign a new label (with the policy's +approval of course) using the **libselinux** API functions. The +`process setexec`, `process setkeycreate` and `process setsockcreate` +permissions can be used to allow subjects to label processes, +kernel keyrings, and sockets programmatically using the +***setexec**(3)*, ***setkeycreatecon**(3)* and +***setsockcreatecon**(3)* functions respectively, overriding +transition statements. + +The `kernel` **initial security identifier** is used to associate +a specified label with kernel objects, including kernel threads +(both those that are created during initialization but also kernel +threads created later), kernel-private sockets, synthetic objects +representing kernel resources (e.g. the "system" class). + +It is true that processes created prior to initial policy load will +also be in the kernel SID until/unless there is a policy loaded and +either a policy-defined transition or an explicit setcon or +setexeccon+execve, but that's just the typical default inheritance +from creating task behavior for processes. + +The `unlabeled` **initial security identifier** is used +to associate a specified label with subjects that had their label +invalidated due to policy changes at runtime. + +It is also assigned as the initial state for various objects e.g. +inodes, superblocks, etc until they reach a point where a more +specific label can be determined e.g. from an xattr or from policy. +The context associated with the unlabeled SID is used as the fallback +context for both subjects and objects when their label is invalidated +by a policy reload (their SID is unchanged but the SID is +transparently remapped to the unlabeled context). + ### Object Reuse As GNU / Linux runs it creates instances of objects and manages the