--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Microsoft Corporation
+ *
+ * Author: Tushar Sugandhi <tusharsu@linux.microsoft.com>
+ *
+ * File: dm-ima.c
+ * Enables IMA measurements for DM targets
+ */
+
+#include "dm-core.h"
+#include "dm-ima.h"
+
+#include <linux/ima.h>
+#include <crypto/hash.h>
+#include <linux/crypto.h>
+#include <crypto/hash_info.h>
+
+#define DM_MSG_PREFIX "ima"
+
+/*
+ * Internal function to prefix separator characters in input buffer with escape
+ * character, so that they don't interfere with the construction of key-value pairs,
+ * and clients can split the key1=val1,key2=val2,key3=val3; pairs properly.
+ */
+static void fix_separator_chars(char **buf)
+{
+ int l = strlen(*buf);
+ int i, j, sp = 0;
+
+ for (i = 0; i < l; i++)
+ if ((*buf)[i] == '\\' || (*buf)[i] == ';' || (*buf)[i] == '=' || (*buf)[i] == ',')
+ sp++;
+
+ if (!sp)
+ return;
+
+ for (i = l-1, j = i+sp; i >= 0; i--) {
+ (*buf)[j--] = (*buf)[i];
+ if ((*buf)[i] == '\\' || (*buf)[i] == ';' || (*buf)[i] == '=' || (*buf)[i] == ',')
+ (*buf)[j--] = '\\';
+ }
+}
+
+/*
+ * Internal function to allocate memory for IMA measurements.
+ */
+static void *dm_ima_alloc(size_t len, gfp_t flags, bool noio)
+{
+ unsigned int noio_flag;
+ void *ptr;
+
+ if (noio)
+ noio_flag = memalloc_noio_save();
+
+ ptr = kzalloc(len, flags);
+
+ if (noio)
+ memalloc_noio_restore(noio_flag);
+
+ return ptr;
+}
+
+/*
+ * Internal function to allocate and copy name and uuid for IMA measurements.
+ */
+static int dm_ima_alloc_and_copy_name_uuid(struct mapped_device *md, char **dev_name,
+ char **dev_uuid, bool noio)
+{
+ int r;
+ *dev_name = dm_ima_alloc(DM_NAME_LEN*2, GFP_KERNEL, noio);
+ if (!(*dev_name)) {
+ r = -ENOMEM;
+ goto error;
+ }
+
+ *dev_uuid = dm_ima_alloc(DM_UUID_LEN*2, GFP_KERNEL, noio);
+ if (!(*dev_uuid)) {
+ r = -ENOMEM;
+ goto error;
+ }
+
+ r = dm_copy_name_and_uuid(md, *dev_name, *dev_uuid);
+ if (r)
+ goto error;
+
+ fix_separator_chars(dev_name);
+ fix_separator_chars(dev_uuid);
+
+ return 0;
+error:
+ kfree(*dev_name);
+ kfree(*dev_uuid);
+ *dev_name = NULL;
+ *dev_uuid = NULL;
+ return r;
+}
+
+/*
+ * Internal function to allocate and copy device data for IMA measurements.
+ */
+static int dm_ima_alloc_and_copy_device_data(struct mapped_device *md, char **device_data,
+ unsigned int num_targets, bool noio)
+{
+ char *dev_name = NULL, *dev_uuid = NULL;
+ int r;
+
+ r = dm_ima_alloc_and_copy_name_uuid(md, &dev_name, &dev_uuid, noio);
+ if (r)
+ return r;
+
+ *device_data = dm_ima_alloc(DM_IMA_DEVICE_BUF_LEN, GFP_KERNEL, noio);
+ if (!(*device_data)) {
+ r = -ENOMEM;
+ goto error;
+ }
+
+ scnprintf(*device_data, DM_IMA_DEVICE_BUF_LEN,
+ "name=%s,uuid=%s,major=%d,minor=%d,minor_count=%d,num_targets=%u;",
+ dev_name, dev_uuid, md->disk->major, md->disk->first_minor,
+ md->disk->minors, num_targets);
+error:
+ kfree(dev_name);
+ kfree(dev_uuid);
+ return r;
+}
+
+/*
+ * Internal wrapper function to call IMA to measure DM data.
+ */
+static void dm_ima_measure_data(const char *event_name, const void *buf, size_t buf_len,
+ bool noio)
+{
+ unsigned int noio_flag;
+
+ if (noio)
+ noio_flag = memalloc_noio_save();
+
+ ima_measure_critical_data(DM_NAME, event_name, buf, buf_len, false);
+
+ if (noio)
+ memalloc_noio_restore(noio_flag);
+}
+
+/*
+ * Initialize/reset the dm ima related data structure variables.
+ */
+void dm_ima_reset_data(struct mapped_device *md)
+{
+ memset(&(md->ima), 0, sizeof(md->ima));
+}
+
+/*
+ * Build up the IMA data for each target, and finally measure.
+ */
+void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_flags)
+{
+ size_t device_data_buf_len, target_metadata_buf_len, target_data_buf_len, l = 0;
+ char *target_metadata_buf = NULL, *target_data_buf = NULL, *digest_buf = NULL;
+ char *ima_buf = NULL, *device_data_buf = NULL;
+ int digest_size, last_target_measured = -1, r;
+ status_type_t type = STATUSTYPE_IMA;
+ size_t cur_total_buf_len = 0;
+ unsigned int num_targets, i;
+ SHASH_DESC_ON_STACK(shash, NULL);
+ struct crypto_shash *tfm = NULL;
+ u8 *digest = NULL;
+ bool noio = false;
+
+ ima_buf = dm_ima_alloc(DM_IMA_MEASUREMENT_BUF_LEN, GFP_KERNEL, noio);
+ if (!ima_buf)
+ return;
+
+ target_metadata_buf = dm_ima_alloc(DM_IMA_TARGET_METADATA_BUF_LEN, GFP_KERNEL, noio);
+ if (!target_metadata_buf)
+ goto error;
+
+ target_data_buf = dm_ima_alloc(DM_IMA_TARGET_DATA_BUF_LEN, GFP_KERNEL, noio);
+ if (!target_data_buf)
+ goto error;
+
+ num_targets = dm_table_get_num_targets(table);
+
+ if (dm_ima_alloc_and_copy_device_data(table->md, &device_data_buf, num_targets, noio))
+ goto error;
+
+ tfm = crypto_alloc_shash("sha256", 0, 0);
+ if (IS_ERR(tfm))
+ goto error;
+
+ shash->tfm = tfm;
+ digest_size = crypto_shash_digestsize(tfm);
+ digest = dm_ima_alloc(digest_size, GFP_KERNEL, noio);
+ if (!digest)
+ goto error;
+
+ r = crypto_shash_init(shash);
+ if (r)
+ goto error;
+
+ device_data_buf_len = strlen(device_data_buf);
+ memcpy(ima_buf + l, device_data_buf, device_data_buf_len);
+ l += device_data_buf_len;
+
+ for (i = 0; i < num_targets; i++) {
+ struct dm_target *ti = dm_table_get_target(table, i);
+
+ if (!ti)
+ goto error;
+
+ last_target_measured = 0;
+
+ /*
+ * First retrieve the target metadata.
+ */
+ scnprintf(target_metadata_buf, DM_IMA_TARGET_METADATA_BUF_LEN,
+ "target_index=%d,target_begin=%llu,target_len=%llu,",
+ i, ti->begin, ti->len);
+ target_metadata_buf_len = strlen(target_metadata_buf);
+
+ /*
+ * Then retrieve the actual target data.
+ */
+ if (ti->type->status)
+ ti->type->status(ti, type, status_flags, target_data_buf,
+ DM_IMA_TARGET_DATA_BUF_LEN);
+ else
+ target_data_buf[0] = '\0';
+
+ target_data_buf_len = strlen(target_data_buf);
+
+ /*
+ * Check if the total data can fit into the IMA buffer.
+ */
+ cur_total_buf_len = l + target_metadata_buf_len + target_data_buf_len;
+
+ /*
+ * IMA measurements for DM targets are best-effort.
+ * If the total data buffered so far, including the current target,
+ * is too large to fit into DM_IMA_MEASUREMENT_BUF_LEN, measure what
+ * we have in the current buffer, and continue measuring the remaining
+ * targets by prefixing the device metadata again.
+ */
+ if (unlikely(cur_total_buf_len >= DM_IMA_MEASUREMENT_BUF_LEN)) {
+ dm_ima_measure_data("table_load", ima_buf, l, noio);
+ r = crypto_shash_update(shash, (const u8 *)ima_buf, l);
+ if (r < 0)
+ goto error;
+
+ memset(ima_buf, 0, DM_IMA_MEASUREMENT_BUF_LEN);
+ l = 0;
+
+ /*
+ * Each new "table_load" entry in IMA log should have device data
+ * prefix, so that multiple records from the same table_load for
+ * a given device can be linked together.
+ */
+ memcpy(ima_buf + l, device_data_buf, device_data_buf_len);
+ l += device_data_buf_len;
+
+ /*
+ * If this iteration of the for loop turns out to be the last target
+ * in the table, dm_ima_measure_data("table_load", ...) doesn't need
+ * to be called again, just the hash needs to be finalized.
+ * "last_target_measured" tracks this state.
+ */
+ last_target_measured = 1;
+ }
+
+ /*
+ * Fill-in all the target metadata, so that multiple targets for the same
+ * device can be linked together.
+ */
+ memcpy(ima_buf + l, target_metadata_buf, target_metadata_buf_len);
+ l += target_metadata_buf_len;
+
+ memcpy(ima_buf + l, target_data_buf, target_data_buf_len);
+ l += target_data_buf_len;
+ }
+
+ if (!last_target_measured) {
+ dm_ima_measure_data("table_load", ima_buf, l, noio);
+
+ r = crypto_shash_update(shash, (const u8 *)ima_buf, l);
+ if (r < 0)
+ goto error;
+ }
+
+ /*
+ * Finalize the table hash, and store it in table->md->ima.inactive_table.hash,
+ * so that the table data can be verified against the future device state change
+ * events, e.g. resume, rename, remove, table-clear etc.
+ */
+ r = crypto_shash_final(shash, digest);
+ if (r < 0)
+ goto error;
+
+ digest_buf = dm_ima_alloc((digest_size*2)+1, GFP_KERNEL, noio);
+ if (!digest_buf)
+ goto error;
+
+ for (i = 0; i < digest_size; i++)
+ snprintf((digest_buf+(i*2)), 3, "%02x", digest[i]);
+
+ if (table->md->ima.active_table.hash != table->md->ima.inactive_table.hash)
+ kfree(table->md->ima.inactive_table.hash);
+
+ table->md->ima.inactive_table.hash = digest_buf;
+ table->md->ima.inactive_table.hash_len = strlen(digest_buf);
+ table->md->ima.inactive_table.num_targets = num_targets;
+
+ if (table->md->ima.active_table.device_metadata !=
+ table->md->ima.inactive_table.device_metadata)
+ kfree(table->md->ima.inactive_table.device_metadata);
+
+ table->md->ima.inactive_table.device_metadata = device_data_buf;
+ table->md->ima.inactive_table.device_metadata_len = device_data_buf_len;
+
+ goto exit;
+error:
+ kfree(digest_buf);
+ kfree(device_data_buf);
+exit:
+ kfree(digest);
+ if (tfm)
+ crypto_free_shash(tfm);
+ kfree(ima_buf);
+ kfree(target_metadata_buf);
+ kfree(target_data_buf);
+}
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