From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:56182 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728046AbeJKWvE (ORCPT ); Thu, 11 Oct 2018 18:51:04 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w9BFLm2S022027 for ; Thu, 11 Oct 2018 11:23:25 -0400 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2n276764es-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 11 Oct 2018 11:23:24 -0400 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 11 Oct 2018 16:23:22 +0100 Subject: Re: [PATCH 2/3] IMA: Make use of filesystem-provided hashes From: Mimi Zohar To: Matthew Garrett , linux-integrity@vger.kernel.org Cc: dmitry.kasatkin@gmail.com, miklos@szeredi.hu, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk Date: Thu, 11 Oct 2018 11:23:06 -0400 In-Reply-To: <20181004203007.217320-3-mjg59@google.com> References: <20181004203007.217320-1-mjg59@google.com> <20181004203007.217320-3-mjg59@google.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <1539271386.11939.79.camel@linux.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu, 2018-10-04 at 13:30 -0700, Matthew Garrett wrote: > Some filesystems may be able to provide hashes in an out of band manner, > and allowing them to do so is a performance win. This is especially true > of FUSE-based filesystems where otherwise we recalculate the hash on > every measurement. Make use of this by default, but provide a parameter > to force recalculation rather than trusting the filesystem. > > Signed-off-by: Matthew Garrett Support for not calculating the file hash would need to be finer grained than this, probably on a per mount basis.  The default should be for IMA to always calculate the file hash, unless explicitly told not to. > --- > Documentation/admin-guide/kernel-parameters.txt | 5 +++++ > security/integrity/ima/ima_crypto.c | 11 +++++++++++ > 2 files changed, 16 insertions(+) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 92eb1f42240d..617ae0f83b14 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1612,6 +1612,11 @@ > different crypto accelerators. This option can be used > to achieve best performance for particular HW. > > + ima.force_hash= [IMA] Force hash calculation in IMA > + Format: > + Always calculate hashes rather than trusting the > + filesystem to provide them to us. > + > init= [KNL] > Format: > Run specified binary instead of /sbin/init as init > diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c > index 7e7e7e7c250a..f25259b2b6ec 100644 > --- a/security/integrity/ima/ima_crypto.c > +++ b/security/integrity/ima/ima_crypto.c > @@ -32,6 +32,10 @@ static unsigned long ima_ahash_minsize; > module_param_named(ahash_minsize, ima_ahash_minsize, ulong, 0644); > MODULE_PARM_DESC(ahash_minsize, "Minimum file size for ahash use"); > > +static bool ima_force_hash; > +module_param_named(force_hash, ima_force_hash, bool_enable_only, 0644); > +MODULE_PARM_DESC(force_hash, "Always calculate hashes"); > + > /* default is 0 - 1 page. */ > static int ima_maxorder; > static unsigned int ima_bufsize = PAGE_SIZE; > @@ -431,6 +435,13 @@ int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash) > return -EINVAL; > } > > + if (!ima_force_hash) { IMA should never skip the file hash calculation if the filesystem is an untrusted mount (eg. SB_I_UNTRUSTED_MOUNTER). Mimi > + hash->length = hash_digest_size[hash->algo]; > + rc = vfs_get_hash(file, hash->algo, hash->digest, hash->length); > + if (!rc) > + return 0; > + } > + > i_size = i_size_read(file_inode(file)); > > if (ima_ahash_minsize && i_size >= ima_ahash_minsize) {