From patchwork Fri Mar 5 15:19:12 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 12118649 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 73A54C43603 for ; Fri, 5 Mar 2021 15:21:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 50DFF6509A for ; Fri, 5 Mar 2021 15:21:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230432AbhCEPUm (ORCPT ); Fri, 5 Mar 2021 10:20:42 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]:2623 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230109AbhCEPUE (ORCPT ); Fri, 5 Mar 2021 10:20:04 -0500 Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4DsWV73FxLz67vx9; Fri, 5 Mar 2021 23:14:07 +0800 (CST) Received: from fraphisprd00473.huawei.com (7.182.8.141) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2106.2; Fri, 5 Mar 2021 16:19:54 +0100 From: Roberto Sassu To: , CC: , , , , Roberto Sassu Subject: [PATCH v4 00/11] evm: Improve usability of portable signatures Date: Fri, 5 Mar 2021 16:19:12 +0100 Message-ID: <20210305151923.29039-1-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 X-Originating-IP: [7.182.8.141] X-ClientProxiedBy: lhreml707-chm.china.huawei.com (10.201.108.56) To fraeml714-chm.china.huawei.com (10.206.15.33) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org EVM portable signatures are particularly suitable for the protection of metadata of immutable files where metadata is signed by a software vendor. They can be used for example in conjunction with an IMA policy that appraises only executed and memory mapped files. However, some usability issues are still unsolved, especially when EVM is used without loading an HMAC key. This patch set attempts to fix the open issues. Patch 1 allows EVM to be used without loading an HMAC key. Patch 2 avoids appraisal verification of public keys (they are already verified by the key subsystem). Patches 3-5 allow metadata verification to be turned off when no HMAC key is loaded and to use this mode in a safe way (by ensuring that IMA revalidates metadata when there is a change). Patches 6-8 make portable signatures more usable if metadata verification is not turned off, by ignoring the INTEGRITY_NOLABEL and INTEGRITY_NOXATTS errors when possible, by accepting any metadata modification until signature verification succeeds (useful when xattrs/attrs are copied sequentially from a source) and by allowing operations that don't change metadata. Patch 9 makes it possible to use portable signatures when the IMA policy requires file signatures and patch 10 shows portable signatures in the measurement list when the ima-sig template is selected. Lastly, patch 11 avoids undesired removal of security.ima when a file is not selected by the IMA policy. Changelog v3: - introduce evm_ignore_error_safe() to correctly ignore INTEGRITY_NOLABEL and INTEGRITY_NOXATTRS errors - fix an error in evm_xattr_acl_change() - replace #ifndef with !IS_ENABLED() in integrity_load_keys() - reintroduce ima_inode_removexattr() - adapt patches to apply on top of the idmapped mounts patch set v2: - replace EVM_RESET_STATUS flag with evm_status_revalidate() - introduce IMA post hooks ima_inode_post_setxattr() and ima_inode_post_removexattr() - remove ima_inode_removexattr() - ignore INTEGRITY_NOLABEL error if the HMAC key is not loaded v1: - introduce EVM_RESET_STATUS integrity flag instead of clearing IMA flag - introduce new template field evmsig - add description of evm_xattr_acl_change() and evm_xattr_change() Roberto Sassu (11): evm: Execute evm_inode_init_security() only when an HMAC key is loaded evm: Load EVM key in ima_load_x509() to avoid appraisal evm: Refuse EVM_ALLOW_METADATA_WRITES only if an HMAC key is loaded ima: Move ima_reset_appraise_flags() call to post hooks evm: Introduce evm_status_revalidate() evm: Ignore INTEGRITY_NOLABEL/INTEGRITY_NOXATTRS if conditions are safe evm: Allow xattr/attr operations for portable signatures evm: Allow setxattr() and setattr() for unmodified metadata ima: Allow imasig requirement to be satisfied by EVM portable signatures ima: Introduce template field evmsig and write to field sig as fallback ima: Don't remove security.ima if file must not be appraised Documentation/ABI/testing/evm | 5 +- Documentation/security/IMA-templates.rst | 4 +- fs/xattr.c | 2 + include/linux/evm.h | 6 + include/linux/ima.h | 18 +++ include/linux/integrity.h | 1 + security/integrity/evm/evm_main.c | 188 ++++++++++++++++++++-- security/integrity/evm/evm_secfs.c | 4 +- security/integrity/iint.c | 4 +- security/integrity/ima/ima_appraise.c | 55 +++++-- security/integrity/ima/ima_init.c | 4 + security/integrity/ima/ima_template.c | 2 + security/integrity/ima/ima_template_lib.c | 33 +++- security/integrity/ima/ima_template_lib.h | 2 + security/security.c | 1 + 15 files changed, 297 insertions(+), 32 deletions(-)