From patchwork Thu Mar 8 20:24:09 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mimi Zohar X-Patchwork-Id: 10269175 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 5DB816037E for ; Thu, 8 Mar 2018 20:24:34 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4D07328768 for ; Thu, 8 Mar 2018 20:24:34 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4191A29A3A; Thu, 8 Mar 2018 20:24:34 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A5F7028768 for ; Thu, 8 Mar 2018 20:24:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751028AbeCHUYd (ORCPT ); Thu, 8 Mar 2018 15:24:33 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:53974 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750966AbeCHUY2 (ORCPT ); Thu, 8 Mar 2018 15:24:28 -0500 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w28K6q1O145131 for ; Thu, 8 Mar 2018 15:24:28 -0500 Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) by mx0b-001b2d01.pphosted.com with ESMTP id 2gkah8kxj0-1 (version=TLSv1.2 cipher=AES256-SHA256 bits=256 verify=NOT) for ; Thu, 08 Mar 2018 15:24:27 -0500 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Thu, 8 Mar 2018 20:24:23 -0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w28KON5N54263826; Thu, 8 Mar 2018 20:24:23 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5FFA74C040; Thu, 8 Mar 2018 20:17:44 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EC2A34C04A; Thu, 8 Mar 2018 20:17:42 +0000 (GMT) Received: from localhost.ibm.com (unknown [9.80.82.179]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 8 Mar 2018 20:17:42 +0000 (GMT) From: Mimi Zohar To: linux-integrity@vger.kernel.org Cc: linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, Mimi Zohar , Miklos Szeredi , Seth Forshee , "Eric W . Biederman" , Dongsu Park , Alban Crequy , "Serge E . Hallyn" Subject: [PATCH v3 3/4] ima: fail signature verification based on policy Date: Thu, 8 Mar 2018 15:24:09 -0500 X-Mailer: git-send-email 2.7.5 In-Reply-To: <1520540650-7451-1-git-send-email-zohar@linux.vnet.ibm.com> References: <1520540650-7451-1-git-send-email-zohar@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18030820-0040-0000-0000-0000041C90D7 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18030820-0041-0000-0000-0000261FAD4B Message-Id: <1520540650-7451-4-git-send-email-zohar@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2018-03-08_11:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803080221 Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This patch addresses the fuse privileged mounted filesystems in environments which are unwilling to accept the risk of trusting the signature verification and want to always fail safe, but are for example using a pre-built kernel. This patch defines a new builtin policy named "fail_securely", which can be specified on the boot command line as an argument to "ima_policy=". Signed-off-by: Mimi Zohar Cc: Miklos Szeredi Cc: Seth Forshee Cc: Eric W. Biederman Cc: Dongsu Park Cc: Alban Crequy Cc: Serge E. Hallyn Acked-by: Serge Hallyn Acked-by: "Eric W. Biederman" --- Changelog v3: - Rename the builtin policy name Changelog v2: - address the fail safe environement Documentation/admin-guide/kernel-parameters.txt | 8 +++++++- security/integrity/ima/ima_appraise.c | 11 ++++++----- security/integrity/ima/ima_main.c | 3 ++- security/integrity/ima/ima_policy.c | 5 +++++ security/integrity/integrity.h | 1 + 5 files changed, 21 insertions(+), 7 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 1d1d53f85ddd..2cc17dc7ab84 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1525,7 +1525,8 @@ ima_policy= [IMA] The builtin policies to load during IMA setup. - Format: "tcb | appraise_tcb | secure_boot" + Format: "tcb | appraise_tcb | secure_boot | + fail_securely" The "tcb" policy measures all programs exec'd, files mmap'd for exec, and all files opened with the read @@ -1540,6 +1541,11 @@ of files (eg. kexec kernel image, kernel modules, firmware, policy, etc) based on file signatures. + The "fail_securely" policy forces file signature + verification failure also on privileged mounted + filesystems with the SB_I_UNVERIFIABLE_SIGNATURE + flag. + ima_tcb [IMA] Deprecated. Use ima_policy= instead. Load a policy which meets the needs of the Trusted Computing Base. This means IMA will measure all diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 4bafb397ee91..3034935e1eb3 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -304,12 +304,13 @@ int ima_appraise_measurement(enum ima_hooks func, out: /* * File signatures on some filesystems can not be properly verified. - * On these filesytems, that are mounted by an untrusted mounter, - * fail the file signature verification. + * On these filesytems, that are mounted by an untrusted mounter or + * for systems not willing to accept the risk, fail the file signature + * verification. */ - if ((inode->i_sb->s_iflags & - (SB_I_IMA_UNVERIFIABLE_SIGNATURE | SB_I_UNTRUSTED_MOUNTER)) == - (SB_I_IMA_UNVERIFIABLE_SIGNATURE | SB_I_UNTRUSTED_MOUNTER)) { + if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && + ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) || + (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) { status = INTEGRITY_FAIL; cause = "unverifiable-signature"; integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index f550f25294a3..5d122daf5c8a 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -238,7 +238,8 @@ static int process_measurement(struct file *file, const struct cred *cred, */ if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) || ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && - !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER))) { + !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) && + !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) { iint->flags &= ~IMA_DONE_MASK; iint->measured_pcrs = 0; } diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index e3da29af2c16..36f9570941c1 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -188,6 +188,7 @@ __setup("ima_tcb", default_measure_policy_setup); static bool ima_use_appraise_tcb __initdata; static bool ima_use_secure_boot __initdata; +static bool ima_fail_unverifiable_sigs __ro_after_init; static int __init policy_setup(char *str) { char *p; @@ -201,6 +202,8 @@ static int __init policy_setup(char *str) ima_use_appraise_tcb = true; else if (strcmp(p, "secure_boot") == 0) ima_use_secure_boot = true; + else if (strcmp(p, "fail_securely") == 0) + ima_fail_unverifiable_sigs = true; } return 1; @@ -390,6 +393,8 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid, if (entry->action & IMA_APPRAISE) { action |= get_subaction(entry, func); action ^= IMA_HASH; + if (ima_fail_unverifiable_sigs) + action |= IMA_FAIL_UNVERIFIABLE_SIGS; } if (entry->action & IMA_DO_MASK) diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h index 843ae23ba0ac..8224880935e0 100644 --- a/security/integrity/integrity.h +++ b/security/integrity/integrity.h @@ -35,6 +35,7 @@ #define IMA_PERMIT_DIRECTIO 0x02000000 #define IMA_NEW_FILE 0x04000000 #define EVM_IMMUTABLE_DIGSIG 0x08000000 +#define IMA_FAIL_UNVERIFIABLE_SIGS 0x10000000 #define IMA_DO_MASK (IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT | \ IMA_HASH | IMA_APPRAISE_SUBMASK)