[PATCH v4 07/14] Add namespace implementation.

Greg Wettstein
2024-08-26T10:50:24Z

The TSEM LSM has its own 'namespace' implementation for
restricting the scope of a security model that is independent of
other resource namespaces but which acts in much the same manner.

The TSEM control plane is used to signal that a process should
leave the root security modeling namespace and institute a new
subordinate modeling namespace. Process that derive from the
lead process all contribute security event descriptions to the
model that is being used to prove the security behavior of the
namespace.

Each modeling domain has a unique numeric identifier that is
implemented as an unsigned 64 bit value that is incremented each
time a new security modeling namespace is created. This
guarantees that every security modeling namespace will have a
unique identifier associated with it. The id value of 0 is
reserved for the root security modeling namespace.

Each modeling domain is designated as either internally or
externally modeled. An internally modeled domain has its
security model implemented by a Trusted Modeling Agent (TMA)
implementation that is run in the context of the kernel.

Externally modeled domains have a description of the security
event exported to a trust orchestrator running in userspace.
That trust orchestrator has an associated Trusted Modeling Agent
that implements the root of trust for the security namespace.

A process that exports a security event description is scheduled
away into an interruptible sleep state, with the exception of
event handlers that are running in atomic context. The trust
orchestrator that created the external modeling domain is
responsible for using the TSEM control plane to wake the process
up and set the trust status of the process to be trusted or
untrusted. The trust orchestrator also has the responsibility of
addressing the status of a workload that has generated a model
violating event that occurs in atomic context.

The namespace exists until the last task running in the context
of the namespace exits. The resources associated with the
namespace are released at that time.
---
security/tsem/namespace.c | 530 ++++++++++++++++++++++++++++++++++++++
1 file changed, 530 insertions(+)
create mode 100644 security/tsem/namespace.c

diff --git a/security/tsem/namespace.c b/security/tsem/namespace.c
new file mode 100644
index 000000000000..e265a1cc7d09
--- /dev/null
+++ b/security/tsem/namespace.c
@@ -0,0 +1,530 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (C) 2024 Enjellic Systems Development, LLC
+ * Author: Dr. Greg Wettstein <greg@enjellic.com>
+ *
+ * This file is responsible for managing the TSEM namespace
+ * implementation that allows security models to be implemented for
+ * workloads that are isolated from the root security modeling
+ * namespace. The namespaces that TSEM implements are
+ * non-heirarchical and are at only a single depth below the root
+ * security modeling namespace.
+ *
+ * Security modeling namespaces are identified by a 64-bit context
+ * identity with context identity 0 being reserved for the root
+ * security modeling namespace.
+ *
+ * The modeling of a namspace can be done by either an internal
+ * trusted modeling agent implementation or by a trusted modeling
+ * agent implementation associated with an external trust
+ * orchestrator.
+ *
+ * This file is responsible for creating and setting up a tsem_context
+ * structure that defines the modeling context being used by a
+ * security modeling namespace. This structure encapsulates
+ * functionality that is generic to the namespace, such as the
+ * cryptographic digest function that is used for security coefficient
+ * mapping.
+ *
+ * Information for managing externally modeled namespaces are
+ * maintained in the tsem_context structure while information for
+ * internally modeled namespaces is maintained in the tsem_model
+ * structure. These structures are populated in the tsem_context
+ * structure depending on whether or not an internal or externally
+ * modeled namespace is being created.
+ *
+ * A tsem_context structure has a kref structure that is used to track
+ * the number of uses of a context. This reference count is
+ * incremented each time a task is allocated in the context of a
+ * security modeling namespace and decremented when a task exists.
+ *
+ * The release of the last reference to a context causes the structure
+ * and its embedded structures to be released, thus freeing the
+ * resources that have been allocated for modeling the namespace.
+ */
+
+#include "tsem.h"
+#include "nsmgr.h"
+
+static u64 context_id;
+
+struct context_key {
+ struct list_head list;
+ u64 context_id;
+ u8 key[HASH_MAX_DIGESTSIZE];
+};
+
+DEFINE_MUTEX(context_id_mutex);
+LIST_HEAD(context_id_list);
+
+static void remove_task_key(u64 context_id)
+{
+ struct context_key *entry, *tmp_entry;
+
+ list_for_each_entry_safe(entry, tmp_entry, &context_id_list, list) {
+ if (context_id == entry->context_id) {
+ list_del(&entry->list);
+ kfree(entry);
+ break;
+ }
+ }
+}
+
+static int generate_task_key(const char *keystr, u64 context_id,
+ struct tsem_task *t_ttask,
+ struct tsem_task *p_ttask)
+{
+ int retn;
+ bool found_key, valid_key = false;
+ unsigned int size = tsem_digestsize();
+ struct context_key *entry;
+
+ while (!valid_key) {
+ get_random_bytes(t_ttask->task_key, size);
+ retn = tsem_ns_event_key(t_ttask->task_key, keystr,
+ p_ttask->task_key);
+ if (retn)
+ goto done;
+
+ if (list_empty(&context_id_list))
+ break;
+
+ found_key = false;
+ list_for_each_entry(entry, &context_id_list, list) {
+ if (!memcmp(entry->key, p_ttask->task_key, size)) {
+ found_key = true;
+ break;
+ }
+ }
+ if (!found_key)
+ valid_key = true;
+ }
+
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry) {
+ retn = -ENOMEM;
+ goto done;
+ }
+
+ entry->context_id = context_id;
+ memcpy(entry->key, p_ttask->task_key, size);
+ list_add_tail(&entry->list, &context_id_list);
+ retn = 0;
+
+ done:
+ return retn;
+}
+
+static struct tsem_external *allocate_external(u64 context_id,
+ const char *keystr)
+{
+ int retn = -ENOMEM;
+ char bufr[20 + 1];
+ struct tsem_external *external;
+ struct tsem_task *t_ttask = tsem_task(current);
+ struct tsem_task *p_ttask = tsem_task(current->real_parent);
+
+ external = kzalloc(sizeof(*external), GFP_KERNEL);
+ if (!external)
+ goto done;
+
+ retn = generate_task_key(keystr, context_id, t_ttask, p_ttask);
+ if (retn)
+ goto done;
+
+ spin_lock_init(&external->export_lock);
+ INIT_LIST_HEAD(&external->export_list);
+
+ init_waitqueue_head(&external->wq);
+
+ scnprintf(bufr, sizeof(bufr), "%llu", context_id);
+ external->dentry = tsem_fs_create_external(bufr);
+ if (IS_ERR(external->dentry)) {
+ retn = PTR_ERR(external->dentry);
+ external->dentry = NULL;
+ } else
+ retn = 0;
+
+ done:
+ if (retn) {
+ memset(t_ttask->task_key, '\0', tsem_digestsize());
+ memset(p_ttask->task_key, '\0', tsem_digestsize());
+ kfree(external);
+ remove_task_key(context_id);
+ external = ERR_PTR(retn);
+ } else
+ p_ttask->tma_for_ns = context_id;
+
+ return external;
+}
+
+static struct tsem_external *allocate_export(u64 context_id)
+{
+ int retn = -ENOMEM;
+ char bufr[20 + 1];
+ struct tsem_external *external;
+
+ external = kzalloc(sizeof(*external), GFP_KERNEL);
+ if (!external)
+ goto done;
+
+ spin_lock_init(&external->export_lock);
+ INIT_LIST_HEAD(&external->export_list);
+
+ init_waitqueue_head(&external->wq);
+
+ scnprintf(bufr, sizeof(bufr), "%llu", context_id);
+ external->dentry = tsem_fs_create_external(bufr);
+ if (IS_ERR(external->dentry)) {
+ retn = PTR_ERR(external->dentry);
+ external->dentry = NULL;
+ } else
+ retn = 0;
+
+ done:
+ if (retn) {
+ kfree(external);
+ external = ERR_PTR(retn);
+ }
+ return external;
+}
+
+static void _release_inode_instances(u64 id, struct tsem_inode *tsip)
+{
+ struct tsem_inode_instance *owner, *tmp_owner;
+
+ mutex_lock(&tsip->instance_mutex);
+ list_for_each_entry_safe(owner, tmp_owner, &tsip->instance_list,
+ list) {
+ if (id == owner->creator) {
+ list_del(&owner->list);
+ kfree(owner);
+ }
+ }
+ mutex_unlock(&tsip->instance_mutex);
+}
+
+static void wq_put(struct work_struct *work)
+{
+ struct tsem_context *ctx;
+ struct tsem_inode_entry *ie, *tmp_ie;
+
+ ctx = container_of(work, struct tsem_context, work);
+
+ mutex_lock(&ctx->inode_mutex);
+ list_for_each_entry_safe(ie, tmp_ie, &ctx->inode_list, list) {
+ list_del(&ie->list);
+ _release_inode_instances(ctx->id, ie->tsip);
+ kfree(ie);
+ }
+ mutex_unlock(&ctx->inode_mutex);
+
+ if (ctx->external) {
+ mutex_lock(&context_id_mutex);
+ remove_task_key(ctx->id);
+ mutex_unlock(&context_id_mutex);
+
+ securityfs_remove(ctx->external->dentry);
+ tsem_export_magazine_free(ctx->external);
+ kfree(ctx->external);
+ } else
+ tsem_model_free(ctx);
+
+ tsem_nsmgr_put(ctx->ops);
+
+ crypto_free_shash(ctx->tfm);
+ tsem_event_magazine_free(ctx);
+ kfree(ctx->digestname);
+ kfree(ctx);
+}
+
+static void ns_free(struct kref *kref)
+{
+ struct tsem_context *ctx;
+
+ ctx = container_of(kref, struct tsem_context, kref);
+
+ INIT_WORK(&ctx->work, wq_put);
+ if (!queue_work(system_wq, &ctx->work))
+ WARN_ON_ONCE(1);
+}
+
+/**
+ * tsem_ns_put() - Release a reference to a modeling context.
+ * @ctx: A pointer to the TMA context for which a reference is
+ * to be released.
+ *
+ * This function is called to release a reference to a TMA modeling
+ * domain. The release of the last reference calls the ns_free()
+ * function that schedules the actual work to release the resources
+ * associated with the namespace to a workqueue.
+ */
+void tsem_ns_put(struct tsem_context *ctx)
+{
+ kref_put(&ctx->kref, ns_free);
+}
+
+/**
+ * tsem_ns_event_key() - Generate TMA authentication key.
+ * @task_key: A pointer to the buffer containing the task identification
+ * key that was randomly generated for the modeling domain.
+ * @keystr: A pointer to the buffer containing the TMA authentication key
+ * in ASCII hexadecimal form.
+ *
+ * This function generates the authentication key that will be used
+ * to validate a call by a TMA to set the trust status of the process.
+ *
+ * Return: This function returns 0 if the key was properly generated
+ * or a negative value if a hashing error occurred.
+ */
+int tsem_ns_event_key(u8 *task_key, const char *keystr, u8 *key)
+{
+ bool retn;
+ u8 tma_key[HASH_MAX_DIGESTSIZE];
+ SHASH_DESC_ON_STACK(shash, tfm);
+
+ retn = hex2bin(tma_key, keystr, tsem_digestsize());
+ if (retn)
+ return -EINVAL;
+
+ shash->tfm = tsem_digest();
+ retn = crypto_shash_init(shash);
+ if (retn)
+ return retn;
+
+ retn = crypto_shash_update(shash, task_key, tsem_digestsize());
+ if (retn)
+ return retn;
+
+ return crypto_shash_finup(shash, tma_key, tsem_digestsize(), key);
+}
+
+static struct crypto_shash *configure_digest(const char *digest,
+ char **digestname,
+ u8 *zero_digest)
+{
+ int retn;
+ struct crypto_shash *tfm;
+ SHASH_DESC_ON_STACK(shash, tfm);
+
+ *digestname = kstrdup(digest, GFP_KERNEL);
+ if (!*digestname)
+ return ERR_PTR(-ENOMEM);
+
+ tfm = crypto_alloc_shash(digest, 0, 0);
+ if (IS_ERR(tfm))
+ return tfm;
+
+ shash->tfm = tfm;
+ retn = crypto_shash_digest(shash, NULL, 0, zero_digest);
+ if (retn) {
+ crypto_free_shash(tfm);
+ tfm = NULL;
+ }
+
+ return tfm;
+}
+
+/**
+ * tsem_ns_create() - Create a TSEM modeling namespace.
+ * @type: The type of namespace being created.
+ * @digest: A null terminated character buffer containing the name
+ * of the hash function that is to be used for the modeling
+ * domain.
+ * @ns: The enumeration type that specifies whether the security
+ * event descriptions should reference the initial user
+ * namespace or the current user namespace.
+ * @key: A pointer to a null-terminated buffer containing the key
+ * that will be used to authenticate the TMA's ability to set
+ * the trust status of a process.
+ * @cache_size: The number of entries to be implemented in the
+ * atomic allocation magazines for the security modeling
+ * namespace being created.
+ * @ops: A pointer to the security namespace definitions and
+ * operations for the namespace being created.
+ *
+ * This function is used to create either an internally or externally
+ * modeled TSEM namespace. The type of the namespace to be created
+ * is specified with the tsem_control_type enumeration value. A
+ * request for an internally model namespace causes a new structure to be
+ * allocated that will hold the description of the security model.
+ * An externally modeled domain will have a control structure allocated
+ * that manages the export of security event descriptions to the
+ * trust orchestrator that is responsible for running the TMA
+ * implementation.
+ *
+ * Return: This function returns 0 if the namespace was created and
+ * a negative error value on error.
+ */
+int tsem_ns_create(const enum tsem_control_type type, const char *digest,
+ const enum tsem_ns_reference ns, const char *key,
+ unsigned int cache_size, const struct tsem_context_ops *ops)
+{
+ u8 zero_digest[HASH_MAX_DIGESTSIZE];
+ char *use_digest;
+ int retn = -ENOMEM;
+ u64 new_id;
+ struct tsem_task *tsk = tsem_task(current);
+ struct tsem_context *new_ctx;
+ struct tsem_model *model = NULL;
+ struct crypto_shash *tfm;
+
+ tfm = configure_digest(digest, &use_digest, zero_digest);
+ if (IS_ERR(tfm))
+ return PTR_ERR(tfm);
+
+ new_ctx = kzalloc(sizeof(*new_ctx), GFP_KERNEL);
+ if (!new_ctx)
+ return retn;
+
+ mutex_lock(&context_id_mutex);
+ new_id = context_id + 1;
+
+ retn = tsem_event_magazine_allocate(new_ctx, cache_size);
+ if (retn)
+ goto done;
+
+ if (type == TSEM_CONTROL_INTERNAL) {
+ model = tsem_model_allocate(cache_size);
+ if (!model)
+ goto done;
+ new_ctx->model = model;
+ }
+ if (type == TSEM_CONTROL_EXTERNAL) {
+ if (crypto_shash_digestsize(tfm)*2 != strlen(key)) {
+ retn = -EINVAL;
+ goto done;
+ }
+
+ new_ctx->external = allocate_external(new_id, key);
+ if (IS_ERR(new_ctx->external)) {
+ retn = PTR_ERR(new_ctx->external);
+ new_ctx->external = NULL;
+ goto done;
+ }
+
+ retn = tsem_export_magazine_allocate(new_ctx->external,
+ cache_size);
+ if (retn)
+ goto done;
+ }
+ if (type == TSEM_CONTROL_EXPORT) {
+ new_ctx->external = allocate_export(new_id);
+ if (IS_ERR(new_ctx->external)) {
+ retn = PTR_ERR(new_ctx->external);
+ new_ctx->external = NULL;
+ goto done;
+ }
+
+ retn = tsem_export_magazine_allocate(new_ctx->external,
+ cache_size);
+ if (retn)
+ goto done;
+
+ new_ctx->external->export_only = true;
+ }
+
+
+ kref_init(&new_ctx->kref);
+
+ new_ctx->id = new_id;
+ new_ctx->tfm = tfm;
+ new_ctx->ops = ops;
+ new_ctx->digestname = use_digest;
+ new_ctx->timestamp = ktime_get_boottime_ns();
+ memcpy(new_ctx->zero_digest, zero_digest,
+ crypto_shash_digestsize(tfm));
+
+ mutex_init(&new_ctx->inode_mutex);
+ INIT_LIST_HEAD(&new_ctx->inode_list);
+
+ if (ns == TSEM_NS_CURRENT)
+ new_ctx->use_current_ns = true;
+ memcpy(new_ctx->actions, tsk->context->actions,
+ sizeof(new_ctx->actions));
+ retn = 0;
+
+ done:
+ if (retn) {
+ if (type != TSEM_CONTROL_EXPORT)
+ remove_task_key(new_id);
+ crypto_free_shash(tfm);
+ tsem_event_magazine_free(new_ctx);
+ kfree(use_digest);
+ if (new_ctx->external)
+ tsem_export_magazine_free(new_ctx->external);
+ kfree(new_ctx->external);
+ kfree(new_ctx);
+ kfree(model);
+ } else {
+ context_id = new_id;
+ tsk->context = new_ctx;
+ if (type == TSEM_CONTROL_EXTERNAL)
+ retn = tsem_export_aggregate();
+ if (type == TSEM_CONTROL_INTERNAL)
+ retn = tsem_model_add_aggregate();
+ }
+
+ mutex_unlock(&context_id_mutex);
+ return retn;
+}
+
+/**
+ * tsem_ns_export_root() - Configure root namespace for export only modeling.
+ * @magazine_size: The number of entries to be implemented in the event
+ * cache.
+ *
+ * This function is called to setup the root security modeling namespace
+ * for the export of security event descriptions in tsem_mode=2
+ * operation.
+ *
+ * Return: This function returns 0 if the setup of the root namespace
+ * for export was successul and a negative error value if
+ * the setup fails.
+ */
+int tsem_ns_export_root(unsigned int magazine_size)
+{
+ int retn = -ENOMEM;
+ struct tsem_context *new_ctx;
+ struct tsem_task *tsk = tsem_task(current);
+
+ new_ctx = kzalloc(sizeof(*new_ctx), GFP_KERNEL);
+ if (!new_ctx)
+ return retn;
+ *new_ctx = *tsem_context(current);
+
+ new_ctx->external = allocate_export(tsem_context(current)->id);
+ if (IS_ERR(new_ctx->external)) {
+ retn = PTR_ERR(new_ctx->external);
+ new_ctx->external = NULL;
+ goto done;
+ }
+
+ retn = tsem_export_magazine_allocate(new_ctx->external, magazine_size);
+ if (retn)
+ goto done;
+
+ new_ctx->external->export_only = true;
+
+ done:
+ if (retn) {
+ tsem_event_magazine_free(new_ctx);
+ if (new_ctx->external)
+ tsem_export_magazine_free(new_ctx->external);
+ kfree(new_ctx);
+ } else {
+ new_ctx->tfm = tsk->context->tfm;
+ new_ctx->timestamp = ktime_get_boottime_ns();
+ new_ctx->digestname = tsk->context->digestname;
+ memcpy(new_ctx->zero_digest, tsk->context->zero_digest,
+ crypto_shash_digestsize(tsk->context->tfm));
+
+ mutex_init(&new_ctx->inode_mutex);
+ INIT_LIST_HEAD(&new_ctx->inode_list);
+
+ tsk->context = new_ctx;
+ }
+
+ return retn;
+}
--
2.39.1