Message-Id: <20201019172607.16714-3-tusharsu@linux.microsoft.com>
Date:   Mon, 19 Oct 2020 10:26:07 -0700
From:   Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To:     zohar@...ux.ibm.com, agk@...hat.com, snitzer@...hat.com,
        gmazyland@...il.com
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: [PATCH v4 2/2] dm-crypt: collect data and submit to DM to measure

Currently, dm-crypt does not take advantage of IMA measuring
capabilities, and ultimately the benefits of remote attestation.

Measure various dm-crypt constructs by calling various device-mapper
functions - dm_ima_*() that use IMA measuring capabilities. Implement
ima_measure_dm_crypt_data() to measure various dm-crypt constructs.

Ensure that ima_measure_dm_crypt_data() is non intrusive, i.e. failures
in this function and the call-stack below should not affect the core
functionality of dm-crypt.

Register dm-crypt as supported data source for IMA measurement in ima.h.

A demonstrative usage of above functionality on a system:

If the IMA policy contains the following rule:

    measure func=CRITICAL_DATA data_sources=dm-crypt template=ima-buf

and, the following commands are used to setup a crypt target:

 #key="faf453b4ee938cff2f0d2c869a0b743f59125c0a37f5bcd8f1dbbd911a78abaa"
 #arg="'0 1953125 crypt aes-xts-plain64 "
 #arg="$arg $key 0 "
 #arg="$arg /dev/loop0 0 1 allow_discards'"
 #tgt_name="test-crypt"
 #cmd="dmsetup create $tgt_name --table $arg"
 #eval $cmd

then, the IMA log at
/sys/kernel/security/integrity/ima/ascii_runtime_measurements should
contain the dm-crypt measurements. And, the following IMA log entry
should be added in the IMA log,
 ima-buf sha1:f418b90557619b42ade6b51476170e5f1a631a31
 1603056402:556677963:dm-crypt:add_target 
 74695f6e756d5f646973636172645f62696f733d313b7065725f62696f5f646
 174615f73697a653d3834383b646d7265715f73746172743d3136383b74666d
 735f636f756e743d313b6f6e5f6469736b5f7461675f73697a653d303b696e7
 46567726974795f69765f73697a653d303b696e746567726974795f7461675f
 73697a653d303b69765f73697a653d31363b69765f6f66667365743d303b736
 563746f725f73686966743d303b736563746f725f73697a653d3531323b666c
 6167733d323b6369706865725f666c6167733d303b63635f73746172743d303
 b6b65795f6d61635f73697a653d303b6b65795f65787472615f73697a653d30
 3b6b65795f70617274733d313b6b65795f73697a653d33323b7461726765745
 f6c656e6774683d313935333132353b7461726765745f626567696e3d303b63
 69706865725f737472696e673d6165732d7874732d706c61696e36343b74617
 26765745f6465766963655f6d616a6f725f6d696e6f723d3235333a313b7461
 726765745f6465766963655f6e616d653d646d2d313b626173655f646576696
 3655f6d616a6f725f6d696e6f723d373a303b626173655f6465766963655f6e
 616d653d6c6f6f70303b

where, the ascii representation of the above data is:

 ti_num_discard_bios=1;per_bio_data_size=848;dmreq_start=168;
 tfms_count=1;on_disk_tag_size=0;integrity_iv_size=0;
 integrity_tag_size=0;iv_size=16;iv_offset=0;sector_shift=0;
 sector_size=512;flags=2;cipher_flags=0;cc_start=0;key_mac_size=0;
 key_extra_size=0;key_parts=1;key_size=32;target_length=1953125;
 target_begin=0;cipher_string=aes-xts-plain64;
 target_device_major_minor=253:1;target_device_name=dm-1;
 base_device_major_minor=7:0;base_device_name=loop0;

Some of the above values can be verified using:

 #dmsetup table --showkeys

where, the output of the command should be similar to:

 test-crypt: 0 1953125 crypt aes-xts-plain64
 faf453b4ee938cff2f0d2c869a0b743f59125c0a37f5bcd8f1dbbd911a78abaa
 0 7:0 0 1 allow_discards

Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
---
 drivers/md/dm-crypt.c                   | 217 ++++++++++++++++++++++++
 security/integrity/ima/ima.h            |   1 +
 security/integrity/ima/ima_queue_data.c |   3 +-
 3 files changed, 220 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 148960721254..6d4030afa163 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -2529,6 +2529,8 @@ static void crypt_dtr(struct dm_target *ti)
 
 	ti->private = NULL;
 
+	dm_ima_exit_measurements(ti->type);
+
 	if (!cc)
 		return;
 
@@ -2991,6 +2993,213 @@ static int crypt_report_zones(struct dm_target *ti,
 
 #endif
 
+#ifdef CONFIG_IMA
+/*
+ * append integer values to dm-crypt specific data
+ * to be measured through IMA
+ */
+static int ima_append_num_values(struct dm_target *ti,
+				 const char *key,
+				 long long num_val)
+{
+	char *num_str = NULL;
+	int length = 0;
+	int r = 0;
+
+	if (!ti || !key) {
+		r = -EINVAL;
+		goto error;
+	}
+
+	length = snprintf(NULL, 0, "%lld", num_val);
+	num_str = kzalloc(length + 1, GFP_KERNEL);
+	if (!num_str) {
+		r = -ENOMEM;
+		goto error;
+	}
+	snprintf(num_str, length + 1, "%lld", num_val);
+	dm_ima_append_measurement_list(ti->type,
+				       key,
+				       (const void *)num_str,
+				       length);
+
+error:
+	if (r < 0)
+		DMERR("appending num values to IMA measurement list failed %d", r);
+	kzfree(num_str);
+	return r;
+}
+/*
+ * Measure dm-crypt specific data through IMA.
+ * It appends all the needed data to the list as a key-val pair using
+ * dm_ima_append_measurement_list() and internal ima_append_num_values(),
+ * and finally measures the list using dm_ima_finalize_and_measure().
+ */
+static void ima_measure_dm_crypt_data(struct dm_target *ti, const char *desc)
+{
+	char *str_base_dev_name = NULL;
+	char *str_target_dev_name = NULL;
+	const char *str_target_dev_maj_min = NULL;
+	struct crypt_config *cc = NULL;
+	int r = 0;
+
+	if (!ti) {
+		r = -EINVAL;
+		goto out;
+	}
+
+	str_target_dev_maj_min = dm_table_device_name(ti->table);
+	if (!str_target_dev_maj_min) {
+		r = -EINVAL;
+		goto out;
+	}
+
+	cc = ti->private;
+
+	r = get_devname_from_maj_min(cc->dev->name, &str_base_dev_name);
+	if (r || !str_base_dev_name) {
+		r = -EINVAL;
+		goto out;
+	}
+
+	dm_ima_append_measurement_list(ti->type,
+				       "base_device_name",
+				       (const void *)str_base_dev_name,
+				       strlen(str_base_dev_name));
+
+
+	dm_ima_append_measurement_list(ti->type,
+				       "base_device_major_minor",
+				       (const void *)cc->dev->name,
+				       strlen(cc->dev->name));
+
+	r = get_devname_from_maj_min(str_target_dev_maj_min,
+				      &str_target_dev_name);
+	if (r || !str_target_dev_name) {
+		r = -EINVAL;
+		goto out;
+	}
+
+	dm_ima_append_measurement_list(ti->type,
+				       "target_device_name",
+				       (const void *)str_target_dev_name,
+				       strlen(str_target_dev_name));
+
+	dm_ima_append_measurement_list(ti->type,
+				       "target_device_major_minor",
+				       (const void *)str_target_dev_maj_min,
+				       strlen(str_target_dev_maj_min));
+
+	if (cc->cipher_string) {
+		dm_ima_append_measurement_list(ti->type,
+					       "cipher_string",
+					       (const void *)cc->cipher_string,
+					       strlen(cc->cipher_string));
+	}
+
+	if (cc->cipher_auth) {
+		dm_ima_append_measurement_list(ti->type,
+					       "cipher_auth",
+					       (const void *)cc->cipher_auth,
+					       strlen(cc->cipher_auth));
+	}
+
+	r = ima_append_num_values(ti, "target_begin", ti->begin);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "target_length", ti->len);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "key_size", cc->key_size);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "key_parts", cc->key_parts);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "key_extra_size", cc->key_extra_size);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "key_mac_size", cc->key_mac_size);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "cc_start", cc->start);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "cipher_flags", cc->cipher_flags);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "flags", cc->flags);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "sector_size", cc->sector_size);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "sector_shift", cc->sector_shift);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "iv_offset", cc->iv_offset);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "iv_size", cc->iv_size);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "integrity_tag_size", cc->integrity_tag_size);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "integrity_iv_size", cc->integrity_iv_size);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "on_disk_tag_size", cc->on_disk_tag_size);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "tfms_count", cc->tfms_count);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "dmreq_start", cc->dmreq_start);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "per_bio_data_size", cc->per_bio_data_size);
+	if (r)
+		goto out;
+
+	r = ima_append_num_values(ti, "ti_num_discard_bios",
+			      ti->num_discard_bios);
+	if (r)
+		goto out;
+
+	dm_ima_finalize_and_measure(ti->type, desc, false);
+
+out:
+	if (r)
+		DMERR("IMA measurement of dm-crypt data failed %d", r);
+
+	kzfree(str_base_dev_name);
+	kzfree(str_target_dev_name);
+}
+#else
+static inline void ima_measure_dm_crypt_data(struct dm_target *ti,
+					     const char *desc) {}
+#endif /* CONFIG_IMA */
+
+
 /*
  * Construct an encryption mapping:
  * <cipher> [<key>|:<key_size>:<user|logon>:<key_description>] <iv_offset> <dev_path> <start>
@@ -3186,6 +3395,10 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
 	ti->num_flush_bios = 1;
 
+	dm_ima_init_measurements(ti->type);
+
+	ima_measure_dm_crypt_data(ti, "add_target");
+
 	return 0;
 
 bad:
@@ -3324,6 +3537,8 @@ static void crypt_postsuspend(struct dm_target *ti)
 	struct crypt_config *cc = ti->private;
 
 	set_bit(DM_CRYPT_SUSPENDED, &cc->flags);
+
+	ima_measure_dm_crypt_data(ti, "post_suspend");
 }
 
 static int crypt_preresume(struct dm_target *ti)
@@ -3343,6 +3558,8 @@ static void crypt_resume(struct dm_target *ti)
 	struct crypt_config *cc = ti->private;
 
 	clear_bit(DM_CRYPT_SUSPENDED, &cc->flags);
+
+	ima_measure_dm_crypt_data(ti, "resume");
 }
 
 /* Message interface
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index e99e5e0db720..3d846c99c4ab 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -230,6 +230,7 @@ struct modsig;
 
 #define __ima_supported_kernel_data_sources(source)	\
 	source(MIN_SOURCE, min_source)			\
+	source(DM_CRYPT, dm-crypt)			\
 	source(MAX_SOURCE, max_source)
 
 #define __ima_enum_stringify(ENUM, str) (#str),
diff --git a/security/integrity/ima/ima_queue_data.c b/security/integrity/ima/ima_queue_data.c
index 9bf0b50024dd..c7ea0a644852 100644
--- a/security/integrity/ima/ima_queue_data.c
+++ b/security/integrity/ima/ima_queue_data.c
@@ -36,7 +36,8 @@ static bool timer_expired;
 static inline bool ima_queuing_enabled(void)
 {
 	if ((IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) &&
-	     IS_ENABLED(CONFIG_SYSTEM_TRUSTED_KEYRING)))
+	     IS_ENABLED(CONFIG_SYSTEM_TRUSTED_KEYRING)) ||
+	     IS_ENABLED(CONFIG_DM_CRYPT))
 		return true;
 
 	return false;
-- 
2.17.1

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