From patchwork Wed May 5 11:33:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 12239799 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 79CE6C43460 for ; Wed, 5 May 2021 11:34:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F29B6109E for ; Wed, 5 May 2021 11:34:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233088AbhEELe4 (ORCPT ); Wed, 5 May 2021 07:34:56 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3012 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233022AbhEELex (ORCPT ); Wed, 5 May 2021 07:34:53 -0400 Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4FZvbB55dGz6yhpy; Wed, 5 May 2021 19:28:06 +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 13:33:54 +0200 From: Roberto Sassu To: , CC: , , , Roberto Sassu Subject: [PATCH v6 09/11] ima: Allow imasig requirement to be satisfied by EVM portable signatures Date: Wed, 5 May 2021 13:33:27 +0200 Message-ID: <20210505113329.1410943-5-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: System administrators can require that all accessed files have a signature by specifying appraise_type=imasig in a policy rule. Currently, IMA signatures satisfy this requirement. Appended signatures may also satisfy this requirement, but are not applicable as IMA signatures. IMA/appended signatures ensure data source authentication for file content and prevent any change. EVM signatures instead ensure data source authentication for file metadata. Given that the digest or signature of the file content must be included in the metadata, EVM signatures provide the same file data guarantees of IMA signatures, as well as providing file metadata guarantees. This patch lets systems protected with EVM signatures pass appraisal verification if the appraise_type=imasig requirement is specified in the policy. This facilitates deployment in the scenarios where only EVM signatures are available. The patch makes the following changes: file xattr types: security.ima: IMA_XATTR_DIGEST/IMA_XATTR_DIGEST_NG security.evm: EVM_XATTR_PORTABLE_DIGSIG execve(), mmap(), open() behavior (with appraise_type=imasig): before: denied (file without IMA signature, imasig requirement not met) after: allowed (file with EVM portable signature, imasig requirement met) open(O_WRONLY) behavior (without appraise_type=imasig): before: allowed (file without IMA signature, not immutable) after: denied (file with EVM portable signature, immutable) In addition, similarly to IMA signatures, this patch temporarily allows new files without or with incomplete metadata to be opened so that content can be written. Signed-off-by: Roberto Sassu Reviewed-by: Mimi Zohar --- security/integrity/ima/ima_appraise.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 6d0983a97711..23af45d8ac58 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -242,12 +242,16 @@ static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint, hash_start = 1; fallthrough; case IMA_XATTR_DIGEST: - if (iint->flags & IMA_DIGSIG_REQUIRED) { - *cause = "IMA-signature-required"; - *status = INTEGRITY_FAIL; - break; + if (*status != INTEGRITY_PASS_IMMUTABLE) { + if (iint->flags & IMA_DIGSIG_REQUIRED) { + *cause = "IMA-signature-required"; + *status = INTEGRITY_FAIL; + break; + } + clear_bit(IMA_DIGSIG, &iint->atomic_flags); + } else { + set_bit(IMA_DIGSIG, &iint->atomic_flags); } - clear_bit(IMA_DIGSIG, &iint->atomic_flags); if (xattr_len - sizeof(xattr_value->type) - hash_start >= iint->ima_hash->length) /* @@ -417,6 +421,7 @@ int ima_appraise_measurement(enum ima_hooks func, cause = "missing-HMAC"; goto out; case INTEGRITY_FAIL_IMMUTABLE: + set_bit(IMA_DIGSIG, &iint->atomic_flags); fallthrough; case INTEGRITY_FAIL: /* Invalid HMAC/signature. */ cause = "invalid-HMAC"; @@ -461,9 +466,12 @@ int ima_appraise_measurement(enum ima_hooks func, status = INTEGRITY_PASS; } - /* Permit new files with file signatures, but without data. */ + /* + * Permit new files with file/EVM portable signatures, but + * without data. + */ if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE && - xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) { + test_bit(IMA_DIGSIG, &iint->atomic_flags)) { status = INTEGRITY_PASS; } @@ -581,6 +589,8 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) return -EINVAL; digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG); + } else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) { + digsig = (xvalue->type == EVM_XATTR_PORTABLE_DIGSIG); } if (result == 1 || evm_status_revalidate(xattr_name)) { ima_reset_appraise_flags(d_backing_inode(dentry), digsig);