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Thu, 24 Dec 2020 00:03:23 +0000 (GMT) Received: from sig-9-65-213-118.ibm.com (unknown [9.65.213.118]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 930335204E; Thu, 24 Dec 2020 00:03:19 +0000 (GMT) Message-ID: <4e83480731b937cea479f688029560444b9cb66a.camel@linux.ibm.com> Subject: Re: [PATCH v9 2/8] IMA: add support to measure buffer data hash From: Mimi Zohar To: Tushar Sugandhi , stephen.smalley.work@gmail.com, casey@schaufler-ca.com, agk@redhat.com, snitzer@redhat.com, gmazyland@gmail.com, paul@paul-moore.com Cc: tyhicks@linux.microsoft.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 Date: Wed, 23 Dec 2020 19:03:18 -0500 In-Reply-To: <20201212180251.9943-3-tusharsu@linux.microsoft.com> References: <20201212180251.9943-1-tusharsu@linux.microsoft.com> <20201212180251.9943-3-tusharsu@linux.microsoft.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.28.5 (3.28.5-12.el8) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2020-12-23_14:2020-12-23,2020-12-23 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 phishscore=0 suspectscore=0 lowpriorityscore=0 priorityscore=1501 mlxscore=0 mlxlogscore=999 spamscore=0 adultscore=0 clxscore=1011 bulkscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012230164 Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Sat, 2020-12-12 at 10:02 -0800, 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. By definition, buffer data is only measured. Nothing new is added by the above paragraph. Please remove 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. Like the patch Subject line use "the buffer data hash" instead of the "hash of a buffer". There's no need to include the boolean parameter name "measure_buf_hash". Please remove it. > > Signed-off-by: Tushar Sugandhi > Reviewed-by: Tyler Hicks > --- > 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 | 38 +++++++++++++++++--- > security/integrity/ima/ima_queue_keys.c | 3 +- > 5 files changed, 39 insertions(+), 9 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); Please abbreviate the boolean name to "hash". The test would then be "if (hash == true)" or "if (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..0f8409d77602 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 ^@hash: measure buffer data hash > * > - * Based on policy, the buffer is measured into the ima log. > + * Measure the buffer into the IMA log, and extend the @pcr. IMA always measures/appraises files and measures buffer data based on policy. The above sentence succintly summarizes what process_buffer_measurement() does. This patch adds support for measuring the "buffer data hash". The following would be an appropriate change. * Based on policy, either the buffer data or buffer data hash is measured > + * > + * 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. This patch should be limited to adding "buffer data hash" support. These changes don't belong in this patch. Please remove. > */ > 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; > @@ -849,13 +862,27 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size, > goto out; > } > > + if (measure_buf_hash) { ^ if (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"; I don't see a good no reason for defining a new audit cause. Use the existing "hashing_error". thanks, Mimi > + 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"; > goto out; > } > > - ret = ima_store_template(entry, violation, NULL, buf, pcr); > + ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr); > if (ret < 0) { > audit_cause = "store_entry"; > ima_free_template_entry(entry); > @@ -890,7 +917,8 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) > return; > > process_buffer_measurement(file_inode(f.file), buf, size, > - "kexec-cmdline", KEXEC_CMDLINE, 0, NULL); > + "kexec-cmdline", KEXEC_CMDLINE, 0, NULL, > + false); > fdput(f); > } > > diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c > index 69a8626a35c0..c2f2ad34f9b7 100644 > --- a/security/integrity/ima/ima_queue_keys.c > +++ b/security/integrity/ima/ima_queue_keys.c > @@ -162,7 +162,8 @@ void ima_process_queued_keys(void) > entry->payload_len, > entry->keyring_name, > KEY_CHECK, 0, > - entry->keyring_name); > + entry->keyring_name, > + false); > list_del(&entry->list); > ima_free_key_entry(entry); > }