dm ima: measure data on device remove

Presence of an active block-device, configured with expected parameters,
is important for an external attestation service to determine if a system
meets the attestation requirements.  Therefore it is important for DM to
measure the device remove events.

Measure device parameters and table hashes when the device is removed,
using either remove or remove_all.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 119 insertions, 0 deletions

diff --git a/drivers/md/dm-ima.c b/drivers/md/dm-ima.c
index 30b9875be63a..4fb230024825 100644
--- a/drivers/md/dm-ima.c
+++ b/drivers/md/dm-ima.c
@@ -444,3 +444,122 @@ error:
 	kfree(capacity_str);
 	kfree(device_table_data);
 }
+
+/*
+ * Measure IMA data on remove.
+ */
+void dm_ima_measure_on_device_remove(struct mapped_device *md, bool remove_all)
+{
+	char *device_table_data, *dev_name = NULL, *dev_uuid = NULL, *capacity_str = NULL;
+	char active_table_str[] = "active_table_hash=";
+	char inactive_table_str[] = "inactive_table_hash=";
+	char device_active_str[] = "device_active_metadata=";
+	char device_inactive_str[] = "device_inactive_metadata=";
+	char remove_all_str[] = "remove_all=";
+	unsigned int active_table_len = strlen(active_table_str);
+	unsigned int inactive_table_len = strlen(inactive_table_str);
+	unsigned int device_active_len = strlen(device_active_str);
+	unsigned int device_inactive_len = strlen(device_inactive_str);
+	unsigned int remove_all_len = strlen(remove_all_str);
+	unsigned int capacity_len = 0;
+	unsigned int l = 0;
+	bool noio = true;
+	int r;
+
+	device_table_data = dm_ima_alloc(DM_IMA_DEVICE_BUF_LEN*2, GFP_KERNEL, noio);
+	if (!device_table_data)
+		goto exit;
+
+	r = dm_ima_alloc_and_copy_capacity_str(md, &capacity_str, noio);
+	if (r) {
+		kfree(device_table_data);
+		goto exit;
+	}
+
+	if (md->ima.active_table.device_metadata) {
+		memcpy(device_table_data + l, device_active_str, device_active_len);
+		l += device_active_len;
+
+		memcpy(device_table_data + l, md->ima.active_table.device_metadata,
+		       md->ima.active_table.device_metadata_len);
+		l += md->ima.active_table.device_metadata_len;
+	}
+
+	if (md->ima.inactive_table.device_metadata) {
+		memcpy(device_table_data + l, device_inactive_str, device_inactive_len);
+		l += device_inactive_len;
+
+		memcpy(device_table_data + l, md->ima.inactive_table.device_metadata,
+		       md->ima.inactive_table.device_metadata_len);
+		l += md->ima.inactive_table.device_metadata_len;
+	}
+
+	if (md->ima.active_table.hash) {
+		memcpy(device_table_data + l, active_table_str, active_table_len);
+		l += active_table_len;
+
+		memcpy(device_table_data + l, md->ima.active_table.hash,
+			   md->ima.active_table.hash_len);
+		l += md->ima.active_table.hash_len;
+
+		memcpy(device_table_data + l, ",", 1);
+		l++;
+	}
+
+	if (md->ima.inactive_table.hash) {
+		memcpy(device_table_data + l, inactive_table_str, inactive_table_len);
+		l += inactive_table_len;
+
+		memcpy(device_table_data + l, md->ima.inactive_table.hash,
+		       md->ima.inactive_table.hash_len);
+		l += md->ima.inactive_table.hash_len;
+
+		memcpy(device_table_data + l, ",", 1);
+		l++;
+	}
+	/*
+	 * In case both active and inactive tables, and corresponding
+	 * device metadata is cleared/missing - record the name and uuid
+	 * in IMA measurements.
+	 */
+	if (!l) {
+		if (dm_ima_alloc_and_copy_name_uuid(md, &dev_name, &dev_uuid, noio))
+			goto error;
+
+		scnprintf(device_table_data, DM_IMA_DEVICE_BUF_LEN,
+			  "name=%s,uuid=%s;device_remove=no_data;",
+			  dev_name, dev_uuid);
+		l += strlen(device_table_data);
+	}
+
+	memcpy(device_table_data + l, remove_all_str, remove_all_len);
+	l += remove_all_len;
+	memcpy(device_table_data + l, remove_all ? "y;" : "n;", 2);
+	l += 2;
+
+	capacity_len = strlen(capacity_str);
+	memcpy(device_table_data + l, capacity_str, capacity_len);
+	l += capacity_len;
+
+	dm_ima_measure_data("device_remove", device_table_data, l, noio);
+
+error:
+	kfree(device_table_data);
+	kfree(capacity_str);
+exit:
+	kfree(md->ima.active_table.device_metadata);
+
+	if (md->ima.active_table.device_metadata !=
+	    md->ima.inactive_table.device_metadata)
+		kfree(md->ima.inactive_table.device_metadata);
+
+	kfree(md->ima.active_table.hash);
+
+	if (md->ima.active_table.hash != md->ima.inactive_table.hash)
+		kfree(md->ima.inactive_table.hash);
+
+	dm_ima_reset_data(md);
+
+	kfree(dev_name);
+	kfree(dev_uuid);
+}