From patchwork Wed May 5 11:29:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 432124 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_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, 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 6D2DEC43461 for ; Wed, 5 May 2021 11:30:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2FF35613BA for ; Wed, 5 May 2021 11:30:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233020AbhEELbB (ORCPT ); Wed, 5 May 2021 07:31:01 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3003 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232905AbhEELbB (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 4FZvS85d7qz6rlXW; Wed, 5 May 2021 19:22:00 +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 13:30:02 +0200 From: Roberto Sassu To: , CC: , , , Roberto Sassu , Subject: [PATCH v6 01/11] evm: Execute evm_inode_init_security() only when an HMAC key is loaded Date: Wed, 5 May 2021 13:29:25 +0200 Message-ID: <20210505112935.1410679-2-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210505112935.1410679-1-roberto.sassu@huawei.com> References: <20210505112935.1410679-1-roberto.sassu@huawei.com> 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: X-Mailing-List: stable@vger.kernel.org evm_inode_init_security() requires an HMAC key to calculate the HMAC on initial xattrs provided by LSMs. However, it checks generically whether a key has been loaded, including also public keys, which is not correct as public keys are not suitable to calculate the HMAC. Originally, support for signature verification was introduced to verify a possibly immutable initial ram disk, when no new files are created, and to switch to HMAC for the root filesystem. By that time, an HMAC key should have been loaded and usable to calculate HMACs for new files. More recently support for requiring an HMAC key was removed from the kernel, so that signature verification can be used alone. Since this is a legitimate use case, evm_inode_init_security() should not return an error when no HMAC key has been loaded. This patch fixes this problem by replacing the evm_key_loaded() check with a check of the EVM_INIT_HMAC flag in evm_initialized. Cc: stable@vger.kernel.org # 4.5.x Fixes: 26ddabfe96b ("evm: enable EVM when X509 certificate is loaded") Signed-off-by: Roberto Sassu Reviewed-by: Mimi Zohar --- security/integrity/evm/evm_main.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 0de367aaa2d3..7ac5204c8d1f 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -521,7 +521,7 @@ void evm_inode_post_setattr(struct dentry *dentry, int ia_valid) } /* - * evm_inode_init_security - initializes security.evm + * evm_inode_init_security - initializes security.evm HMAC value */ int evm_inode_init_security(struct inode *inode, const struct xattr *lsm_xattr, @@ -530,7 +530,8 @@ int evm_inode_init_security(struct inode *inode, struct evm_xattr *xattr_data; int rc; - if (!evm_key_loaded() || !evm_protected_xattr(lsm_xattr->name)) + if (!(evm_initialized & EVM_INIT_HMAC) || + !evm_protected_xattr(lsm_xattr->name)) return 0; xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); From patchwork Wed May 5 11:29:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 431617 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_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, 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 7F784C43600 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 621DD610A7 for ; Wed, 5 May 2021 11:30:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233053AbhEELbD (ORCPT ); Wed, 5 May 2021 07:31:03 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3006 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232967AbhEELbB (ORCPT ); Wed, 5 May 2021 07:31:01 -0400 Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4FZvVl3R3hz6yjBC; Wed, 5 May 2021 19:24:15 +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 13:30:03 +0200 From: Roberto Sassu To: , CC: , , , Roberto Sassu , Subject: [PATCH v6 03/11] evm: Refuse EVM_ALLOW_METADATA_WRITES only if an HMAC key is loaded Date: Wed, 5 May 2021 13:29:27 +0200 Message-ID: <20210505112935.1410679-4-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210505112935.1410679-1-roberto.sassu@huawei.com> References: <20210505112935.1410679-1-roberto.sassu@huawei.com> 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: X-Mailing-List: stable@vger.kernel.org EVM_ALLOW_METADATA_WRITES is an EVM initialization flag that can be set to temporarily disable metadata verification until all xattrs/attrs necessary to verify an EVM portable signature are copied to the file. This flag is cleared when EVM is initialized with an HMAC key, to avoid that the HMAC is calculated on unverified xattrs/attrs. Currently EVM unnecessarily denies setting this flag if EVM is initialized with a public key, which is not a concern as it cannot be used to trust xattrs/attrs updates. This patch removes this limitation. Cc: stable@vger.kernel.org # 4.16.x Fixes: ae1ba1676b88e ("EVM: Allow userland to permit modification of EVM-protected metadata") Signed-off-by: Roberto Sassu Reviewed-by: Mimi Zohar --- Documentation/ABI/testing/evm | 5 +++-- security/integrity/evm/evm_secfs.c | 5 ++--- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/Documentation/ABI/testing/evm b/Documentation/ABI/testing/evm index 3c477ba48a31..eb6d70fd6fa2 100644 --- a/Documentation/ABI/testing/evm +++ b/Documentation/ABI/testing/evm @@ -49,8 +49,9 @@ Description: modification of EVM-protected metadata and disable all further modification of policy - Note that once a key has been loaded, it will no longer be - possible to enable metadata modification. + Note that once an HMAC key has been loaded, it will no longer + be possible to enable metadata modification and, if it is + already enabled, it will be disabled. Until key loading has been signaled EVM can not create or validate the 'security.evm' xattr, but returns diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c index bbc85637e18b..860c48b9a0c3 100644 --- a/security/integrity/evm/evm_secfs.c +++ b/security/integrity/evm/evm_secfs.c @@ -81,11 +81,10 @@ static ssize_t evm_write_key(struct file *file, const char __user *buf, return -EINVAL; /* Don't allow a request to freshly enable metadata writes if - * keys are loaded. + * an HMAC key is loaded. */ if ((i & EVM_ALLOW_METADATA_WRITES) && - ((evm_initialized & EVM_KEY_MASK) != 0) && - !(evm_initialized & EVM_ALLOW_METADATA_WRITES)) + (evm_initialized & EVM_INIT_HMAC) != 0) return -EPERM; if (i & EVM_INIT_HMAC) {