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Violators will be prosecuted; Thu, 8 Mar 2018 20:24:18 -0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w28KOHHp52822034; Thu, 8 Mar 2018 20:24:17 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D82724C044; Thu, 8 Mar 2018 20:17:38 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6AFE94C040; Thu, 8 Mar 2018 20:17:37 +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 20:17:37 +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 1/4] ima: fail file signature verification on non-init mounted filesystems Date: Thu, 8 Mar 2018 15:24:07 -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: 18030820-0040-0000-0000-0000041C90D4 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18030820-0041-0000-0000-0000261FAD48 Message-Id: <1520540650-7451-2-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=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803080221 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 Acked-by: Serge Hallyn Acked-by: "Eric W. Biederman" --- Changelog v3: - Fix SB_IMA_UNVERIFIABLE_SIGNATURE & SB_I_UNTRUSTED_MOUNTER test. 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 | 15 ++++++++++++++- 2 files changed, 16 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..4bafb397ee91 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -302,7 +302,19 @@ 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)) == + (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 +331,7 @@ int ima_appraise_measurement(enum ima_hooks func, } else { ima_cache_flags(iint, func); } + ima_set_cache_status(iint, func, status); return status; }