From mboxrd@z Thu Jan 1 00:00:00 1970 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=-23.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 D585AC0018C for ; Fri, 11 Dec 2020 02:10:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9668723ECF for ; Fri, 11 Dec 2020 02:10:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389329AbgLKCJc (ORCPT ); Thu, 10 Dec 2020 21:09:32 -0500 Received: from linux.microsoft.com ([13.77.154.182]:58586 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389315AbgLKCJS (ORCPT ); Thu, 10 Dec 2020 21:09:18 -0500 Received: from sequoia (162-237-133-238.lightspeed.rcsntx.sbcglobal.net [162.237.133.238]) by linux.microsoft.com (Postfix) with ESMTPSA id 0D8A820B717A; Thu, 10 Dec 2020 18:08:34 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 0D8A820B717A DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1607652516; bh=9X/NJCjbNRL+2FRUiUBV5P5PMfmvUnnF+PMN3fhX2f8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qJ4kL50mWser+1/zBiQQ6cfgXARSNcSdfYIGjsCoBZSxWLSshBUJZvb/DGjc/Ikom MC4ou8NBhcD2stSkHZmxXhhPF0g9CQAilLsvTXcs5oYxe2Ix9VQhn+IeyYoU93tdr9 iRpoUGFQJC2R1tvx/bZjP6vf8gt1HtBTjTyc+VNY= Date: Thu, 10 Dec 2020 20:08:33 -0600 From: Tyler Hicks To: Tushar Sugandhi Cc: zohar@linux.ibm.com, stephen.smalley.work@gmail.com, casey@schaufler-ca.com, agk@redhat.com, snitzer@redhat.com, gmazyland@gmail.com, paul@paul-moore.com, sashal@kernel.org, jmorris@namei.org, nramas@linux.microsoft.com, linux-integrity@vger.kernel.org, selinux@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com Subject: Re: [PATCH v7 2/8] IMA: add support to measure buffer data hash Message-ID: <20201211020833.GM489768@sequoia> References: <20201209194212.5131-1-tusharsu@linux.microsoft.com> <20201209194212.5131-3-tusharsu@linux.microsoft.com> <20201210223854.GG489768@sequoia> <09d42e5e-09bf-af6e-cc45-c2f9bc8b39de@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <09d42e5e-09bf-af6e-cc45-c2f9bc8b39de@linux.microsoft.com> Precedence: bulk List-ID: On 2020-12-10 17:21:19, Tushar Sugandhi wrote: > > > On 2020-12-10 2:38 p.m., Tyler Hicks wrote: > > On 2020-12-09 11:42:06, Tushar Sugandhi wrote: > > > The original IMA buffer data measurement sizes were small (e.g. boot > > > command line), but the new buffer data measurement use cases have data > > > sizes that are a lot larger. Just as IMA measures the file data hash, > > > not the file data, IMA should similarly support the option for measuring > > > the hash of the buffer data. > > > > > > Measuring in-memory buffer-data/buffer-data-hash is different than > > > measuring file-data/file-data-hash. For the file, IMA stores the > > > measurements in both measurement log and the file's extended attribute - > > > which can later be used for appraisal as well. For buffer, the > > > measurements are only stored in the IMA log, since the buffer has no > > > extended attributes associated with it. > > > > > > Introduce a boolean parameter measure_buf_hash to support measuring > > > hash of a buffer, which would be much smaller, instead of the buffer > > > itself. > > > > > > Signed-off-by: Tushar Sugandhi > > > --- > > > security/integrity/ima/ima.h | 3 +- > > > security/integrity/ima/ima_appraise.c | 2 +- > > > security/integrity/ima/ima_asymmetric_keys.c | 2 +- > > > security/integrity/ima/ima_main.c | 36 +++++++++++++++++--- > > > security/integrity/ima/ima_queue_keys.c | 3 +- > > > 5 files changed, 38 insertions(+), 8 deletions(-) > > > > > > diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h > > > index e5622ce8cbb1..fa3044a7539f 100644 > > > --- a/security/integrity/ima/ima.h > > > +++ b/security/integrity/ima/ima.h > > > @@ -268,7 +268,8 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file, > > > struct ima_template_desc *template_desc); > > > void process_buffer_measurement(struct inode *inode, const void *buf, int size, > > > const char *eventname, enum ima_hooks func, > > > - int pcr, const char *func_data); > > > + int pcr, const char *func_data, > > > + bool measure_buf_hash); > > > void ima_audit_measurement(struct integrity_iint_cache *iint, > > > const unsigned char *filename); > > > int ima_alloc_init_template(struct ima_event_data *event_data, > > > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > > > index 8361941ee0a1..46ffa38bab12 100644 > > > --- a/security/integrity/ima/ima_appraise.c > > > +++ b/security/integrity/ima/ima_appraise.c > > > @@ -352,7 +352,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint, > > > if ((rc == -EPERM) && (iint->flags & IMA_MEASURE)) > > > process_buffer_measurement(NULL, digest, digestsize, > > > "blacklisted-hash", NONE, > > > - pcr, NULL); > > > + pcr, NULL, false); > > > } > > > return rc; > > > diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c > > > index 1c68c500c26f..a74095793936 100644 > > > --- a/security/integrity/ima/ima_asymmetric_keys.c > > > +++ b/security/integrity/ima/ima_asymmetric_keys.c > > > @@ -60,5 +60,5 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key, > > > */ > > > process_buffer_measurement(NULL, payload, payload_len, > > > keyring->description, KEY_CHECK, 0, > > > - keyring->description); > > > + keyring->description, false); > > > } > > > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c > > > index e76ef4bfd0f4..03aad13e9e70 100644 > > > --- a/security/integrity/ima/ima_main.c > > > +++ b/security/integrity/ima/ima_main.c > > > @@ -779,7 +779,7 @@ int ima_post_load_data(char *buf, loff_t size, > > > } > > > /* > > > - * process_buffer_measurement - Measure the buffer to ima log. > > > + * process_buffer_measurement - Measure the buffer or the buffer data hash > > > * @inode: inode associated with the object being measured (NULL for KEY_CHECK) > > > * @buf: pointer to the buffer that needs to be added to the log. > > > * @size: size of buffer(in bytes). > > > @@ -787,12 +787,23 @@ int ima_post_load_data(char *buf, loff_t size, > > > * @func: IMA hook > > > * @pcr: pcr to extend the measurement > > > * @func_data: private data specific to @func, can be NULL. > > > + * @measure_buf_hash: measure buffer hash > > > * > > > - * Based on policy, the buffer is measured into the ima log. > > > + * Measure the buffer into the IMA log, and extend the @pcr. > > > + * > > > + * Determine what buffers are allowed to be measured, based on the policy rules > > > + * and the IMA hook passed using @func. > > > + * > > > + * Use @func_data, if provided, to match against the measurement policy rule > > > + * data for @func. > > > + * > > > + * If @measure_buf_hash is set to true - measure hash of the buffer data, > > > + * else measure the buffer data itself. > > > */ > > > void process_buffer_measurement(struct inode *inode, const void *buf, int size, > > > const char *eventname, enum ima_hooks func, > > > - int pcr, const char *func_data) > > > + int pcr, const char *func_data, > > > + bool measure_buf_hash) > > > { > > > int ret = 0; > > > const char *audit_cause = "ENOMEM"; > > > @@ -807,6 +818,8 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size, > > > struct ima_digest_data hdr; > > > char digest[IMA_MAX_DIGEST_SIZE]; > > > } hash = {}; > > > + char buf_hash[IMA_MAX_DIGEST_SIZE]; > > > + int buf_hash_len = hash_digest_size[ima_hash_algo]; > > > int violation = 0; > > > int action = 0; > > > u32 secid; > > > @@ -849,6 +862,20 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size, > > > goto out; > > > } > > > + if (measure_buf_hash) { > > > + memcpy(buf_hash, hash.hdr.digest, buf_hash_len); > > > + > > > + ret = ima_calc_buffer_hash(buf_hash, buf_hash_len, > > > + iint.ima_hash); > > > + if (ret < 0) { > > > + audit_cause = "measure_buf_hash_error"; > > > + goto out; > > > + } > > > + > > > + event_data.buf = buf_hash; > > > + event_data.buf_len = buf_hash_len; > > > + } > > > + > > > ret = ima_alloc_init_template(&event_data, &entry, template); > > > if (ret < 0) { > > > audit_cause = "alloc_entry"; > > > > A few more lines below, not present in this context, is a call to > > ima_store_template() with buf as the fourth parameter passed in. That > > parameter eventually makes its way to integrity_audit_message() and ends > > up as part of an audit message as the value of the "name=" field. This > > is usually a filename, the name of a key, or a kexec cmdline. In the > > case of measuring SELinux policy, do we want the entire buf to be > > included in the audit message? > > > > Tyler > > > Great catch. > We obviously don't want to include the entire buf in the audit message, > especially when the measure_buf_hash is set to true. (the buffer being > measured is expected to be large in that case) > > How about the following? Does it look ok to you? Mimi? > > if (measure_buf_hash) > ret = ima_store_template(entry, violation, NULL, buf_hash, pcr); > else > ret = ima_store_template(entry, violation, NULL, buf, pcr); I think that looks fine. You could also just pass event_data.buf to ima_store_template(). Tyler > > ~Tushar >