From patchwork Wed May 5 11:29:24 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 12239773 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 1B46CC43470 for ; Wed, 5 May 2021 11:30:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00E00613C7 for ; Wed, 5 May 2021 11:30:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233050AbhEELbD (ORCPT ); Wed, 5 May 2021 07:31:03 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3004 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230001AbhEELbB (ORCPT ); Wed, 5 May 2021 07:31:01 -0400 Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4FZvVj5bCPz6yj77; Wed, 5 May 2021 19:24:13 +0800 (CST) Received: from roberto-ThinkStation-P620.huawei.com (10.204.62.217) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 5 May 2021 13:30:01 +0200 From: Roberto Sassu To: , CC: , , , Roberto Sassu Subject: [PATCH v6 00/11] evm: Improve usability of portable signatures Date: Wed, 5 May 2021 13:29:24 +0200 Message-ID: <20210505112935.1410679-1-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Originating-IP: [10.204.62.217] X-ClientProxiedBy: lhreml752-chm.china.huawei.com (10.201.108.202) To fraeml714-chm.china.huawei.com (10.206.15.33) X-CFilter-Loop: Reflected Precedence: bulk List-ID: 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 3-4 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 5-8 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. Test: https://github.com/robertosassu/ima-evm-utils/blob/ima-evm-fixes-v6-devel-v1/tests/portable_signatures.test Test results: https://travis-ci.com/github/robertosassu/ima-evm-utils/jobs/503096506 https://travis-ci.com/github/robertosassu/ima-evm-utils/jobs/503096510 Changelog v5: - remove IMA xattr post hooks and call evm_revalidate() from pre hooks (suggested by Mimi) - rename evm_ignore_error_safe() to evm_hmac_disabled() and check the errors inline (suggested by Mimi) - improve readability of error handling in evm_verify_hmac() (suggested by Mimi) - don't show an error message if the EVM status is INTEGRITY_PASS_IMMUTABLE (suggested by Mimi) - check if CONFIG_FS_POSIX_ACL is defined in evm_xattr_acl_change() (reported by kernel test robot) - fix return value of evm_xattr_change() (suggested by Christian Brauner) - simplify EVM_ALLOW_METADATA_WRITES check in evm_write_key() (suggested by Mimi) v4: - add patch to pass mnt_userns to EVM inode set/remove xattr hooks (suggested by Christian Brauner) - pass mnt_userns to posix_acl_update_mode() - use IS_ERR_OR_NULL() in evm_xattr_acl_change() (suggested by Mimi) 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 evm: Introduce evm_status_revalidate() evm: Introduce evm_hmac_disabled() to safely ignore verification errors evm: Allow xattr/attr operations for portable signatures evm: Pass user namespace to set/remove xattr hooks 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 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 evm: Introduce evm_status_revalidate() evm: Introduce evm_hmac_disabled() to safely ignore verification errors evm: Allow xattr/attr operations for portable signatures evm: Pass user namespace to set/remove xattr hooks 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 +- include/linux/evm.h | 18 +- include/linux/integrity.h | 1 + security/integrity/evm/evm_main.c | 227 ++++++++++++++++++++-- security/integrity/evm/evm_secfs.c | 5 +- security/integrity/iint.c | 4 +- security/integrity/ima/ima_appraise.c | 43 ++-- 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 | 4 +- 13 files changed, 304 insertions(+), 48 deletions(-)