For the device-mapper targets to take advantage of IMA's measuring and quoting abilities, and for enabling remote attestation for device-mapper targets, device-mapper needs to provide the functionality to consistently measure target data using ima_measure_critical_data() function provided by IMA. A generic set of functions at device-mapper layer would enable the measurement structure to be uniform across targets, and avoid code duplication. It will also make on-boarding easier and faster for targets that want to use IMA infrastructure for measurements, quoting, and remote attestation. The uniform measurement structure across targets would also help the remote attestation services to consistently process, across targets, the measurement to be attested. Implement a set of functions at device-mapper layer to manage the data coming from various device-mapper targets to be measured by IMA. Provide the functionality for various tasks - initialize the necessary data structures, add the data to the list of key-value pairs to be be measured, reset the list if needed (e.g. in error/retry cases), and finally pass it on to device-mapper layer, to be measured by IMA. Ensure the functionality is generic and implemented at device-mapper layer, so that any device-mapper target can use it to measure its data through IMA. Also make sure the functionality is non-intrusive/best effort for the targets using it. The errors in managing the list to be measured, and the actual errors in the measurement should not disrupt the core functionality of the targets. Protect the list of key value pairs to be measured for a given target, by putting it under critical sections - so that multi-threaded targets can safely use the list to append the data from different threads, for measurements and quoting. Compute the last measurement's hash and store it internally, so that unnecessary duplicate data is not sent to IMA for measurement. Divide the functionality into 5 main functions: (1) dm_ima_init_measurements(): Use it to initialize device-mapper target's IMA measurement list. It should abstract the necessary data initialization from the device-mapper target apps. (2) dm_ima_append_measurement_list(): Use it to append the key-value pair to the existing list of key-value pairs to measure. (3) dm_ima_finalize_and_measure(): Use it to measure the key-value pair list for a given target, and finally release the resources held by the list for that specific target. Note that the data given by the target for a given device would be sent to IMA subsystem for measurement only if it has changed since the last time it was measured. (4) dm_ima_reset_measurement_list(): Use it to reset device-mapper target's ima measurement list, by releasing the resources held by the list. Use it if the measurements list need to be reset after dm_ima_init_measurements() and before calling dm_ima_finalize_and_measure(). This can be needed in scenarios like recovering from error paths and retrying measurements and quoting again. (5) dm_ima_exit_measurements(): Use it during the destruction of the target - to release the resources held for measurement. This is useful to protect the kernel from possible resource leaks when the target adds data for measurements using dm_ima_append_measurement_list(), but gets destroyed before calling dm_ima_finalize_and_measure(). Signed-off-by: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx> --- drivers/md/Makefile | 1 + drivers/md/dm-ima.c | 298 ++++++++++++++++++++++++++++++++++ include/linux/device-mapper.h | 60 +++++++ 3 files changed, 359 insertions(+) create mode 100644 drivers/md/dm-ima.c diff --git a/drivers/md/Makefile b/drivers/md/Makefile index 6d3e234dc46a..0dc50181aaf2 100644 --- a/drivers/md/Makefile +++ b/drivers/md/Makefile @@ -77,6 +77,7 @@ obj-$(CONFIG_DM_LOG_WRITES) += dm-log-writes.o obj-$(CONFIG_DM_INTEGRITY) += dm-integrity.o obj-$(CONFIG_DM_ZONED) += dm-zoned.o obj-$(CONFIG_DM_WRITECACHE) += dm-writecache.o +obj-$(CONFIG_IMA) += dm-ima.o ifeq ($(CONFIG_DM_INIT),y) dm-mod-objs += dm-init.o diff --git a/drivers/md/dm-ima.c b/drivers/md/dm-ima.c new file mode 100644 index 000000000000..2651e5c88395 --- /dev/null +++ b/drivers/md/dm-ima.c @@ -0,0 +1,298 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2020 Microsoft Corporation + * + * Author: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx> + * + * File: dm-ima.c + * Enables IMA measurements for DM targets + */ + +#include "dm-core.h" + +#include <linux/ima.h> +#include <linux/device-mapper.h> +#include <crypto/hash.h> +#include <linux/crypto.h> +#include <crypto/hash_info.h> + +#define DM_MSG_PREFIX "ima" + +static int dm_compute_buffer_hash(void *buf, + size_t buf_len, + void **buf_hash, + int *buf_hash_len) +{ + struct crypto_shash *tfm; + struct shash_desc *desc = NULL; + void *digest = NULL; + int desc_size; + int digest_size; + int ret = 0; + + tfm = crypto_alloc_shash("sha256", 0, 0); + if (IS_ERR(tfm)) + return PTR_ERR(tfm); + + desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); + digest_size = crypto_shash_digestsize(tfm); + + digest = kmalloc(digest_size, GFP_KERNEL); + if (!digest) { + ret = -ENOMEM; + goto error; + } + + desc = kzalloc(desc_size, GFP_KERNEL); + if (!desc) { + ret = -ENOMEM; + goto error; + } + + desc->tfm = tfm; + + ret = crypto_shash_digest(desc, buf, buf_len, digest); + if (ret < 0) + goto error; + + *buf_hash_len = digest_size; + *buf_hash = digest; + digest = NULL; + +error: + kfree(desc); + kfree(digest); + + crypto_free_shash(tfm); + + return ret; +} + +static void dm_release_ima_measurements(struct list_head + *ima_kv_list) +{ + struct ima_keyval *cur_keyval, *tmp_keyval; + + list_for_each_entry_safe(cur_keyval, + tmp_keyval, + ima_kv_list, + kv_list) { + + list_del(&cur_keyval->kv_list); + kzfree(cur_keyval->key); + kzfree(cur_keyval->val); + kfree(cur_keyval); + } +} + +void dm_ima_init_measurements(struct target_type *tt) +{ + INIT_LIST_HEAD(&tt->ima_kv_list); + mutex_init(&tt->ima_lock); + tt->ima_last_buf_hash = NULL; + tt->ima_last_buf_hash_len = 0; +} +EXPORT_SYMBOL(dm_ima_init_measurements); + +void dm_ima_reset_measurement_list(struct target_type *tt) +{ + LIST_HEAD(temp_list); + + if (!tt) { + DMERR("invalid argument, target_type"); + return; + } + + mutex_lock(&tt->ima_lock); + list_cut_before(&temp_list, &tt->ima_kv_list, &tt->ima_kv_list); + mutex_unlock(&tt->ima_lock); + + dm_release_ima_measurements(&temp_list); +} +EXPORT_SYMBOL(dm_ima_reset_measurement_list); + +void dm_ima_append_measurement_list(struct target_type *tt, + const char *key, + const void *val, + unsigned int val_len) +{ + struct ima_keyval *cur_keyval = NULL; + int r = 0; + + if (!tt || !key || !val || val_len == 0) { + r = -EINVAL; + goto error; + } + + cur_keyval = kzalloc(sizeof(*cur_keyval), GFP_KERNEL); + if (!cur_keyval) { + r = -ENOMEM; + goto error; + } + + cur_keyval->key = kstrdup(key, GFP_KERNEL); + if (!cur_keyval->key) { + r = -ENOMEM; + goto error; + } + + cur_keyval->val_len = val_len; + cur_keyval->val = kmemdup(val, val_len, GFP_KERNEL); + if (!cur_keyval->val) { + r = -ENOMEM; + goto error; + } + + INIT_LIST_HEAD(&cur_keyval->kv_list); + + mutex_lock(&tt->ima_lock); + list_add(&cur_keyval->kv_list, &tt->ima_kv_list); + mutex_unlock(&tt->ima_lock); + + return; + +error: + if (cur_keyval) { + kzfree(cur_keyval->key); + kzfree(cur_keyval->val); + } + kfree(cur_keyval); + + DMERR("failed to append IMA measurement list %d", r); +} +EXPORT_SYMBOL(dm_ima_append_measurement_list); + +void dm_ima_finalize_and_measure(struct target_type *tt, + const char *buf_desc, + bool measure_buf_hash) +{ + char *evt_name = NULL, *evt_src = NULL, *equ = "=", *sep = ";"; + void *buf = NULL, *buf_hash = NULL, *last_buf_hash = NULL; + struct ima_keyval *cur_keyval = NULL, *tmp_keyval = NULL; + int cursor = 0, buf_len = 0, cur_keyname_len = 0; + int l_sep = strlen(sep), l_equ = strlen(equ); + int r = 0, hr = 0, mr = 0; + int buf_hash_len = 0; + struct timespec64 ts; + LIST_HEAD(temp_list); + + + if (!tt) { + r = -EINVAL; + goto out; + } + + mutex_lock(&tt->ima_lock); + if (!list_empty(&tt->ima_kv_list)) + list_cut_before(&temp_list, + &tt->ima_kv_list, + &tt->ima_kv_list); + else + r = -EINVAL; + + last_buf_hash = tt->ima_last_buf_hash; + tt->ima_last_buf_hash = NULL; + tt->ima_last_buf_hash_len = 0; + mutex_unlock(&tt->ima_lock); + + if (r) + goto out; + + list_for_each_entry_safe(cur_keyval, + tmp_keyval, + &temp_list, + kv_list) + buf_len += strlen(cur_keyval->key) + l_equ + + cur_keyval->val_len + l_sep; + + if (!buf_len) { + r = -EINVAL; + goto out; + } + + buf = kzalloc(buf_len, GFP_KERNEL); + if (!buf) { + r = -ENOMEM; + goto out; + } + + list_for_each_entry_safe(cur_keyval, + tmp_keyval, + &temp_list, + kv_list) { + cur_keyname_len = strlen(cur_keyval->key); + memcpy(buf+cursor, cur_keyval->key, cur_keyname_len); + cursor += cur_keyname_len; + memcpy(buf+cursor, equ, l_equ); + cursor += l_equ; + memcpy(buf+cursor, cur_keyval->val, cur_keyval->val_len); + cursor += cur_keyval->val_len; + memcpy(buf+cursor, sep, l_sep); + cursor += l_sep; + } + + hr = dm_compute_buffer_hash(buf, buf_len, &buf_hash, &buf_hash_len); + + if (!hr && buf_hash && last_buf_hash) + mr = memcmp(buf_hash, last_buf_hash, buf_hash_len); + + if (hr || mr || !last_buf_hash) { + ktime_get_real_ts64(&ts); + + evt_src = kasprintf(GFP_KERNEL, "dm-%s", tt->name); + if (!evt_src) { + r = -ENOMEM; + goto out; + } + + evt_name = kasprintf(GFP_KERNEL, "%lld:%09ld:%s%s%s", + ts.tv_sec, + ts.tv_nsec, + evt_src, + buf_desc ? ":" : "", + buf_desc ? buf_desc : ""); + + if (!evt_name) { + r = -ENOMEM; + goto out; + } + + ima_measure_critical_data((const char *)evt_name, + (const char *)evt_src, + (const void *)buf, + buf_len, + measure_buf_hash); + + kzfree(last_buf_hash); + + mutex_lock(&tt->ima_lock); + tt->ima_last_buf_hash = buf_hash; + tt->ima_last_buf_hash_len = buf_hash_len; + mutex_unlock(&tt->ima_lock); + + buf_hash = NULL; + } + + dm_release_ima_measurements(&temp_list); +out: + if (r) + DMERR("failed to measure DM target data through IMA %d", r); + + kfree(evt_src); + kzfree(evt_name); + kzfree(buf); + kzfree(buf_hash); +} +EXPORT_SYMBOL(dm_ima_finalize_and_measure); + +void dm_ima_exit_measurements(struct target_type *tt) +{ + dm_ima_reset_measurement_list(tt); + kzfree(tt->ima_last_buf_hash); + mutex_destroy(&tt->ima_lock); +} +EXPORT_SYMBOL(dm_ima_exit_measurements); + +MODULE_AUTHOR("Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx>"); +MODULE_DESCRIPTION("Enables IMA measurements for DM targets"); +MODULE_LICENSE("GPL"); diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 93096e524e43..0568ba619723 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -164,6 +164,18 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, struct dm_dev **result); void dm_put_device(struct dm_target *ti, struct dm_dev *d); +/* + * Information about IMA measurement data entry + */ +#ifdef CONFIG_IMA +struct ima_keyval { + char *key; + void *val; + unsigned int val_len; + struct list_head kv_list; +}; +#endif + /* * Information about a target type */ @@ -199,6 +211,13 @@ struct target_type { dm_dax_copy_iter_fn dax_copy_to_iter; dm_dax_zero_page_range_fn dax_zero_page_range; +#ifdef CONFIG_IMA + /* For ima measurements*/ + struct list_head ima_kv_list; + void *ima_last_buf_hash; + int ima_last_buf_hash_len; + struct mutex ima_lock; +#endif /* For internal device-mapper use. */ struct list_head list; }; @@ -533,6 +552,47 @@ struct dm_table *dm_swap_table(struct mapped_device *md, */ void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size); +/*----------------------------------------------------------------- + * Functions for ima measurements. + *----------------------------------------------------------------- + */ +#ifdef CONFIG_IMA +void dm_ima_init_measurements(struct target_type *tt); + +/* + * Reset device mapper target's ima measurement list. + * If the measurements list need to be reset after dm_ima_init_measurements() + * and before calling dm_ima_finalize_and_measure(), this function should + * be called. This can be needed in scenarios like recovering from error + * paths and retrying measurements again. + */ +void dm_ima_reset_measurement_list(struct target_type *tt); + +void dm_ima_append_measurement_list(struct target_type *tt, + const char *key, + const void *val, + unsigned int val_length); + +void dm_ima_finalize_and_measure(struct target_type *tt, + const char *buf_desc, + bool measure_buf_hash); + +void dm_ima_exit_measurements(struct target_type *tt); +#else +static inline void dm_ima_init_measurements(struct target_type *tt) {} + +static inline void dm_ima_reset_measurement_list(struct target_type *tt) {} + +static inline void dm_ima_append_measurement_list(struct target_type *tt, + const char *key, + const void *val, + unsigned int val_length) {} + +static inline void dm_ima_finalize_and_measure(struct target_type *tt, + const char *buf_desc, + bool measure_buf_hash) {} +static inline void dm_ima_exit_measurements(struct target_type *tt) {} +#endif /* CONFIG_IMA */ /*----------------------------------------------------------------- * Macros. *---------------------------------------------------------------*/ -- 2.17.1