From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:35304 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751367AbeBVVdQ (ORCPT ); Thu, 22 Feb 2018 16:33:16 -0500 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w1MLTOB8018803 for ; Thu, 22 Feb 2018 16:33:16 -0500 Received: from e06smtp14.uk.ibm.com (e06smtp14.uk.ibm.com [195.75.94.110]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ga268gfbh-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 22 Feb 2018 16:33:15 -0500 Received: from localhost by e06smtp14.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 22 Feb 2018 21:33:13 -0000 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 v2 1/4] ima: fail file signature verification on non-init mounted filesystems Date: Thu, 22 Feb 2018 16:33:01 -0500 In-Reply-To: <1519335184-17808-1-git-send-email-zohar@linux.vnet.ibm.com> References: <1519335184-17808-1-git-send-email-zohar@linux.vnet.ibm.com> Message-Id: <1519335184-17808-2-git-send-email-zohar@linux.vnet.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: FUSE can be mounted by unprivileged users either today with fusermount installed with setuid, or soon with the upcoming patches to allow FUSE mounts in a non-init user namespace. This patch addresses the new unprivileged non-init mounted filesystems, which are untrusted, by failing the signature verification. This patch defines two new flags SB_I_IMA_UNVERIFIABLE_SIGNATURE and SB_I_UNTRUSTED_MOUNTER. 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 Changelog v2: - Limit patch to non-init mounted filesystems. - Define 2 sb->s_iflags Changelog v1: - Merged the unprivileged and privileged patches. - Dropped IMA fsname support. - Introduced a new IMA builtin policy named "untrusted_fs". - Replaced fs_type flag with sb->s_iflags flag. --- include/linux/fs.h | 2 ++ security/integrity/ima/ima_appraise.c | 14 +++++++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index 2a815560fda0..4e1c76af7b68 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1320,6 +1320,8 @@ extern int send_sigurg(struct fown_struct *fown); /* sb->s_iflags to limit user namespace mounts */ #define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */ +#define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020 +#define SB_I_UNTRUSTED_MOUNTER 0x00000040 /* Possible states of 'frozen' field */ enum { diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 1b177461f20e..f34901069e78 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -302,7 +302,18 @@ int ima_appraise_measurement(enum ima_hooks func, } out: - if (status != INTEGRITY_PASS) { + /* + * 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. + */ + if (inode->i_sb->s_iflags & + (SB_I_IMA_UNVERIFIABLE_SIGNATURE | SB_I_UNTRUSTED_MOUNTER)) { + status = INTEGRITY_FAIL; + cause = "unverifiable-signature"; + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, + op, cause, rc, 0); + } else if (status != INTEGRITY_PASS) { if ((ima_appraise & IMA_APPRAISE_FIX) && (!xattr_value || xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { @@ -319,6 +330,7 @@ int ima_appraise_measurement(enum ima_hooks func, } else { ima_cache_flags(iint, func); } + ima_set_cache_status(iint, func, status); return status; } -- 2.7.5