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.
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 sha1:4cbca71967d6b48e13ff5283d8e657899b005f70
1597518359:539244018:dm-crypt:add_target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where, the ascii representation of the above data is:
ti_num_discard_bios=1;per_bio_data_size=808;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;start=0;key_mac_size=0;
key_extra_size=0;key_parts=1;key_size=32;
cipher_string=aes-xts-plain64;device_name=253:0;
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 <tusha...@linux.microsoft.com>
---
drivers/md/dm-crypt.c | 170 +++++++++++++++++++++++++++++++++
security/integrity/ima/Kconfig | 3 +-
2 files changed, 171 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 000ddfab5ba0..aaca9594ec98 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -2465,6 +2465,8 @@ static void crypt_dtr(struct dm_target *ti)
ti->private = NULL;
+ dm_ima_exit_measurements(ti->type);
+
if (!cc)
return;
@@ -2908,6 +2910,166 @@ static int crypt_ctr_optional(struct dm_target *ti,
unsigned int argc, char **ar
return 0;
}
+#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);
+ kzfree(num_str);
+ return r;
+error:
+ DMERR("appending num values to IMA measurement list failed %d", r);
+ 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)
+{
+ int r = 0;
+ struct crypt_config *cc = NULL;
+ const char *devname = dm_table_device_name(ti->table);
+
+ if (!ti) {
+ r = -EINVAL;
+ goto out;
+ }
+
+ cc = ti->private;
+
+ if (devname) {
+ dm_ima_append_measurement_list(ti->type,
+ "device_name",
+ (const void *)devname,
+ strlen(devname));
+ }
+
+ 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, "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, "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);
+ return;
+
+out:
+ DMERR("IMA measurement of dm-crypt data failed %d", r);
+
+}
+#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>
@@ -3093,6 +3255,10 @@ 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:
@@ -3225,6 +3391,8 @@ 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)
@@ -3244,6 +3412,8 @@ 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/Kconfig b/security/integrity/ima/Kconfig
index bc2adab7bae2..2078db4c16e2 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -324,8 +324,7 @@ config IMA_MEASURE_ASYMMETRIC_KEYS
config IMA_QUEUE_EARLY_BOOT_DATA
bool
- depends on IMA_MEASURE_ASYMMETRIC_KEYS
- depends on SYSTEM_TRUSTED_KEYRING
+ depends on (IMA_MEASURE_ASYMMETRIC_KEYS && SYSTEM_TRUSTED_KEYRING) ||
DM_CRYPT
default y
config IMA_SECURE_AND_OR_TRUSTED_BOOT
--
2.17.1
